[patch V3 00/20] x86/iopl: Prevent user space from using CLI/STI with iopl(3)

[patch V3 00/20] x86/iopl: Prevent user space from using CLI/STI with iopl(3)

[Thomas Gleixner]

This is the third version of the attempt to confine the unwanted side
effects of iopl(). The first version of this series can be found here:

   https://lore.kernel.org/r/20191106193459.581614484@linutronix.de

Second version is here:

   https://lore.kernel.org/r/20191111220314.519933535@linutronix.de

The V1 cover letter also contains a longer variant of the
background. Summary:

iopl(level = 3) enables aside of access to all 65536 I/O ports also the
usage of CLI/STI in user space.

Disabling interrupts in user space can lead to system lockups and breaks
assumptions in the kernel that userspace always runs with interrupts
enabled.

iopl() is often preferred over ioperm() as it avoids the overhead of
copying the tasks I/O bitmap to the TSS bitmap on context switch. This
overhead can be avoided by providing a all zeroes bitmap in the TSS and
switching the TSS bitmap offset to this permit all IO bitmap. It's
marginally slower than iopl() which is a one time setup, but prevents the
usage of CLI/STI in user space.

The changes vs. V3:

    - Split out the restructuring of the first/subsequent ioperm()
      invocation into a seperate patch to address the inconsisteny which
      Andy detected in the patch which introduces the concept of
      invalidating the I/O bitmap base to speed up context switching.
      This change is moved in front so the subsequent changes are
      functionally correct.

    - Moved the non HW TSS data related to I/O bitmap(s) into a seperate
      data structure. Modified version of Ingos proposed patch.

    - Made struct memeber names more consistent (Ingo)

    - Dropped the bitmap union. It is not longer necessary because V2
      already dropped the finer grained copying algorithm. The sequence
      count approach should avoid most of the copying overhead when the
      number of ioperm() using processes is very low which is the normal
      case.

    - Dropped the pointer storage of the bitmap in the TSS data as it is
      not required (Peter, Andy)

    - Fixed the missing refcount setting in the bitmap duplication code
      path. (Peter, Andy)

    - Updated changelog and comment to explain the bitmap invalidation
      logic. (Andy)

    - Removed TIF_IO_BITMAP from the TIF flags which are evaluated on the
      next task for entering the slow path.

    - Folded the NULL pointer check fix

    - Simplified the config option in the legacy removal patch (Andy)

    - Extended the scope of the config option to disable ioperm() along
      with iopl() which also mokes all related storage and functions
      compile time conditional. (Andy)

The series is also available from git:

  git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git WIP.x86/iopl

Thanks,

	tglx
---
 arch/x86/Kconfig                        |   18 ++
 arch/x86/entry/common.c                 |    4 
 arch/x86/include/asm/io_bitmap.h        |   29 ++++
 arch/x86/include/asm/paravirt.h         |    4 
 arch/x86/include/asm/paravirt_types.h   |    2 
 arch/x86/include/asm/pgtable_32_types.h |    2 
 arch/x86/include/asm/processor.h        |  113 ++++++++++-------
 arch/x86/include/asm/ptrace.h           |    6 
 arch/x86/include/asm/switch_to.h        |   10 +
 arch/x86/include/asm/thread_info.h      |   14 +-
 arch/x86/include/asm/xen/hypervisor.h   |    2 
 arch/x86/kernel/cpu/common.c            |  188 ++++++++++++----------------
 arch/x86/kernel/doublefault.c           |    2 
 arch/x86/kernel/ioport.c                |  209 +++++++++++++++++++++-----------
 arch/x86/kernel/paravirt.c              |    2 
 arch/x86/kernel/process.c               |  200 ++++++++++++++++++++++++------
 arch/x86/kernel/process_32.c            |   77 -----------
 arch/x86/kernel/process_64.c            |   86 -------------
 arch/x86/kernel/ptrace.c                |   12 +
 arch/x86/kvm/vmx/vmx.c                  |    8 -
 arch/x86/mm/cpu_entry_area.c            |    8 +
 arch/x86/xen/enlighten_pv.c             |   10 -
 tools/testing/selftests/x86/ioperm.c    |   16 ++
 tools/testing/selftests/x86/iopl.c      |  129 ++++++++++++++++++-
 24 files changed, 674 insertions(+), 477 deletions(-)

[patch V3 01/20] x86/ptrace: Prevent truncation of bitmap size

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

The active() callback of the IO bitmap regset divides the IO bitmap size by
the word size (32/64 bit). As the I/O bitmap size is in bytes the active
check fails for bitmap sizes of 1-3 bytes on 32bit and 1-7 bytes on 64bit.

Use DIV_ROUND_UP() instead.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>


---
 arch/x86/kernel/ptrace.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -697,7 +697,7 @@ static int ptrace_set_debugreg(struct ta
 static int ioperm_active(struct task_struct *target,
 			 const struct user_regset *regset)
 {
-	return target->thread.io_bitmap_max / regset->size;
+	return DIV_ROUND_UP(target->thread.io_bitmap_max, regset->size);
 }
 
 static int ioperm_get(struct task_struct *target,

[tip: x86/iopl] x86/ptrace: Prevent truncation of bitmap size

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     c5d623b17c2424272b3355a524b094ff02cfd9aa
Gitweb:        https://git.kernel.org/tip/c5d623b17c2424272b3355a524b094ff02cfd9aa
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:41 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:14:59 +01:00

x86/ptrace: Prevent truncation of bitmap size

The active() callback of the IO bitmap regset divides the IO bitmap size by
the word size (32/64 bit). As the I/O bitmap size is in bytes the active
check fails for bitmap sizes of 1-3 bytes on 32bit and 1-7 bytes on 64bit.

Use DIV_ROUND_UP() instead.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210103.819769574@linutronix.de



---
 arch/x86/kernel/ptrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 3c5bbe8..7c52674 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -697,7 +697,7 @@ static int ptrace_set_debugreg(struct task_struct *tsk, int n,
 static int ioperm_active(struct task_struct *target,
 			 const struct user_regset *regset)
 {
-	return target->thread.io_bitmap_max / regset->size;
+	return DIV_ROUND_UP(target->thread.io_bitmap_max, regset->size);
 }
 
 static int ioperm_get(struct task_struct *target,

[patch V3 02/20] x86/process: Unify copy_thread_tls()

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

While looking at the TSS io bitmap it turned out that any change in that
area would require identical changes to copy_thread_tls(). The 32 and 64
bit variants share sufficient code to consolidate them into a common
function to avoid duplication of upcoming modifications.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>

---
 arch/x86/include/asm/ptrace.h    |    6 ++
 arch/x86/include/asm/switch_to.h |   10 ++++
 arch/x86/kernel/process.c        |   94 +++++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/process_32.c     |   68 ----------------------------
 arch/x86/kernel/process_64.c     |   75 -------------------------------
 5 files changed, 110 insertions(+), 143 deletions(-)

--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -361,5 +361,11 @@ extern int do_get_thread_area(struct tas
 extern int do_set_thread_area(struct task_struct *p, int idx,
 			      struct user_desc __user *info, int can_allocate);
 
+#ifdef CONFIG_X86_64
+# define do_set_thread_area_64(p, s, t)	do_arch_prctl_64(p, s, t)
+#else
+# define do_set_thread_area_64(p, s, t)	(0)
+#endif
+
 #endif /* !__ASSEMBLY__ */
 #endif /* _ASM_X86_PTRACE_H */
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -103,7 +103,17 @@ static inline void update_task_stack(str
 	if (static_cpu_has(X86_FEATURE_XENPV))
 		load_sp0(task_top_of_stack(task));
 #endif
+}
 
+static inline void kthread_frame_init(struct inactive_task_frame *frame,
+				      unsigned long fun, unsigned long arg)
+{
+	frame->bx = fun;
+#ifdef CONFIG_X86_32
+	frame->di = arg;
+#else
+	frame->r12 = arg;
+#endif
 }
 
 #endif /* _ASM_X86_SWITCH_TO_H */
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -132,6 +132,100 @@ void exit_thread(struct task_struct *tsk
 	fpu__drop(fpu);
 }
 
+static int set_new_tls(struct task_struct *p, unsigned long tls)
+{
+	struct user_desc __user *utls = (struct user_desc __user *)tls;
+
+	if (in_ia32_syscall())
+		return do_set_thread_area(p, -1, utls, 0);
+	else
+		return do_set_thread_area_64(p, ARCH_SET_FS, tls);
+}
+
+static inline int copy_io_bitmap(struct task_struct *tsk)
+{
+	if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP)))
+		return 0;
+
+	tsk->thread.io_bitmap_ptr = kmemdup(current->thread.io_bitmap_ptr,
+					    IO_BITMAP_BYTES, GFP_KERNEL);
+	if (!tsk->thread.io_bitmap_ptr) {
+		tsk->thread.io_bitmap_max = 0;
+		return -ENOMEM;
+	}
+	set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
+	return 0;
+}
+
+static inline void free_io_bitmap(struct task_struct *tsk)
+{
+	if (tsk->thread.io_bitmap_ptr) {
+		kfree(tsk->thread.io_bitmap_ptr);
+		tsk->thread.io_bitmap_ptr = NULL;
+		tsk->thread.io_bitmap_max = 0;
+	}
+}
+
+int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
+		    unsigned long arg, struct task_struct *p, unsigned long tls)
+{
+	struct inactive_task_frame *frame;
+	struct fork_frame *fork_frame;
+	struct pt_regs *childregs;
+	int ret;
+
+	childregs = task_pt_regs(p);
+	fork_frame = container_of(childregs, struct fork_frame, regs);
+	frame = &fork_frame->frame;
+
+	frame->bp = 0;
+	frame->ret_addr = (unsigned long) ret_from_fork;
+	p->thread.sp = (unsigned long) fork_frame;
+	p->thread.io_bitmap_ptr = NULL;
+	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
+
+#ifdef CONFIG_X86_64
+	savesegment(gs, p->thread.gsindex);
+	p->thread.gsbase = p->thread.gsindex ? 0 : current->thread.gsbase;
+	savesegment(fs, p->thread.fsindex);
+	p->thread.fsbase = p->thread.fsindex ? 0 : current->thread.fsbase;
+	savesegment(es, p->thread.es);
+	savesegment(ds, p->thread.ds);
+#else
+	/* Clear all status flags including IF and set fixed bit. */
+	frame->flags = X86_EFLAGS_FIXED;
+#endif
+
+	/* Kernel thread ? */
+	if (unlikely(p->flags & PF_KTHREAD)) {
+		memset(childregs, 0, sizeof(struct pt_regs));
+		kthread_frame_init(frame, sp, arg);
+		return 0;
+	}
+
+	frame->bx = 0;
+	*childregs = *current_pt_regs();
+	childregs->ax = 0;
+	if (sp)
+		childregs->sp = sp;
+
+#ifdef CONFIG_X86_32
+	task_user_gs(p) = get_user_gs(current_pt_regs());
+#endif
+
+	ret = copy_io_bitmap(p);
+	if (ret)
+		return ret;
+
+	/* Set a new TLS for the child thread? */
+	if (clone_flags & CLONE_SETTLS) {
+		ret = set_new_tls(p, tls);
+		if (ret)
+			free_io_bitmap(p);
+	}
+	return ret;
+}
+
 void flush_thread(void)
 {
 	struct task_struct *tsk = current;
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -112,74 +112,6 @@ void release_thread(struct task_struct *
 	release_vm86_irqs(dead_task);
 }
 
-int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
-	unsigned long arg, struct task_struct *p, unsigned long tls)
-{
-	struct pt_regs *childregs = task_pt_regs(p);
-	struct fork_frame *fork_frame = container_of(childregs, struct fork_frame, regs);
-	struct inactive_task_frame *frame = &fork_frame->frame;
-	struct task_struct *tsk;
-	int err;
-
-	/*
-	 * For a new task use the RESET flags value since there is no before.
-	 * All the status flags are zero; DF and all the system flags must also
-	 * be 0, specifically IF must be 0 because we context switch to the new
-	 * task with interrupts disabled.
-	 */
-	frame->flags = X86_EFLAGS_FIXED;
-	frame->bp = 0;
-	frame->ret_addr = (unsigned long) ret_from_fork;
-	p->thread.sp = (unsigned long) fork_frame;
-	p->thread.sp0 = (unsigned long) (childregs+1);
-	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
-
-	if (unlikely(p->flags & PF_KTHREAD)) {
-		/* kernel thread */
-		memset(childregs, 0, sizeof(struct pt_regs));
-		frame->bx = sp;		/* function */
-		frame->di = arg;
-		p->thread.io_bitmap_ptr = NULL;
-		return 0;
-	}
-	frame->bx = 0;
-	*childregs = *current_pt_regs();
-	childregs->ax = 0;
-	if (sp)
-		childregs->sp = sp;
-
-	task_user_gs(p) = get_user_gs(current_pt_regs());
-
-	p->thread.io_bitmap_ptr = NULL;
-	tsk = current;
-	err = -ENOMEM;
-
-	if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
-		p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
-						IO_BITMAP_BYTES, GFP_KERNEL);
-		if (!p->thread.io_bitmap_ptr) {
-			p->thread.io_bitmap_max = 0;
-			return -ENOMEM;
-		}
-		set_tsk_thread_flag(p, TIF_IO_BITMAP);
-	}
-
-	err = 0;
-
-	/*
-	 * Set a new TLS for the child thread?
-	 */
-	if (clone_flags & CLONE_SETTLS)
-		err = do_set_thread_area(p, -1,
-			(struct user_desc __user *)tls, 0);
-
-	if (err && p->thread.io_bitmap_ptr) {
-		kfree(p->thread.io_bitmap_ptr);
-		p->thread.io_bitmap_max = 0;
-	}
-	return err;
-}
-
 void
 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
 {
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -371,81 +371,6 @@ void x86_gsbase_write_task(struct task_s
 	task->thread.gsbase = gsbase;
 }
 
-int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
-		unsigned long arg, struct task_struct *p, unsigned long tls)
-{
-	int err;
-	struct pt_regs *childregs;
-	struct fork_frame *fork_frame;
-	struct inactive_task_frame *frame;
-	struct task_struct *me = current;
-
-	childregs = task_pt_regs(p);
-	fork_frame = container_of(childregs, struct fork_frame, regs);
-	frame = &fork_frame->frame;
-
-	frame->bp = 0;
-	frame->ret_addr = (unsigned long) ret_from_fork;
-	p->thread.sp = (unsigned long) fork_frame;
-	p->thread.io_bitmap_ptr = NULL;
-
-	savesegment(gs, p->thread.gsindex);
-	p->thread.gsbase = p->thread.gsindex ? 0 : me->thread.gsbase;
-	savesegment(fs, p->thread.fsindex);
-	p->thread.fsbase = p->thread.fsindex ? 0 : me->thread.fsbase;
-	savesegment(es, p->thread.es);
-	savesegment(ds, p->thread.ds);
-	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
-
-	if (unlikely(p->flags & PF_KTHREAD)) {
-		/* kernel thread */
-		memset(childregs, 0, sizeof(struct pt_regs));
-		frame->bx = sp;		/* function */
-		frame->r12 = arg;
-		return 0;
-	}
-	frame->bx = 0;
-	*childregs = *current_pt_regs();
-
-	childregs->ax = 0;
-	if (sp)
-		childregs->sp = sp;
-
-	err = -ENOMEM;
-	if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
-		p->thread.io_bitmap_ptr = kmemdup(me->thread.io_bitmap_ptr,
-						  IO_BITMAP_BYTES, GFP_KERNEL);
-		if (!p->thread.io_bitmap_ptr) {
-			p->thread.io_bitmap_max = 0;
-			return -ENOMEM;
-		}
-		set_tsk_thread_flag(p, TIF_IO_BITMAP);
-	}
-
-	/*
-	 * Set a new TLS for the child thread?
-	 */
-	if (clone_flags & CLONE_SETTLS) {
-#ifdef CONFIG_IA32_EMULATION
-		if (in_ia32_syscall())
-			err = do_set_thread_area(p, -1,
-				(struct user_desc __user *)tls, 0);
-		else
-#endif
-			err = do_arch_prctl_64(p, ARCH_SET_FS, tls);
-		if (err)
-			goto out;
-	}
-	err = 0;
-out:
-	if (err && p->thread.io_bitmap_ptr) {
-		kfree(p->thread.io_bitmap_ptr);
-		p->thread.io_bitmap_max = 0;
-	}
-
-	return err;
-}
-
 static void
 start_thread_common(struct pt_regs *regs, unsigned long new_ip,
 		    unsigned long new_sp,

Re: [patch V3 02/20] x86/process: Unify copy_thread_tls()

[Linus Torvalds]

On Wed, Nov 13, 2019 at 1:02 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> +int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
> +                   unsigned long arg, struct task_struct *p, unsigned long tls)
...
> +#ifdef CONFIG_X86_64
..
> +#else
> +       /* Clear all status flags including IF and set fixed bit. */
> +       frame->flags = X86_EFLAGS_FIXED;
> +#endif

Hmm. The unification I like, but it also shows these differences that
I don't remember the reason for.

Remind me why __switch_to_asm() on 32-bit safes eflags, but we don't
do it on x86-64?

The comment just talks about callee-saved registers, but flags isn't
callee-saved, so there's something else going on.

This patch clearly doesn't change anything, I'm not complaining about
the patch at all. I'm just wondering about the odd difference that the
patch exposes.

               Linus

Re: [patch V3 02/20] x86/process: Unify copy_thread_tls()

[Thomas Gleixner]

On Wed, 13 Nov 2019, Linus Torvalds wrote:
> On Wed, Nov 13, 2019 at 1:02 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > +int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
> > +                   unsigned long arg, struct task_struct *p, unsigned long tls)
> ...
> > +#ifdef CONFIG_X86_64
> ..
> > +#else
> > +       /* Clear all status flags including IF and set fixed bit. */
> > +       frame->flags = X86_EFLAGS_FIXED;
> > +#endif
> 
> Hmm. The unification I like, but it also shows these differences that
> I don't remember the reason for.
> 
> Remind me why __switch_to_asm() on 32-bit safes eflags, but we don't
> do it on x86-64?
> 
> The comment just talks about callee-saved registers, but flags isn't
> callee-saved, so there's something else going on.
> 
> This patch clearly doesn't change anything, I'm not complaining about
> the patch at all. I'm just wondering about the odd difference that the
> patch exposes.

See commit: 64604d54d311 ("sched/x86_64: Don't save flags on context switch")

We need "only" make objtool support 32bit :)

Thanks,

	tglx

Re: [patch V3 02/20] x86/process: Unify copy_thread_tls()

[Linus Torvalds]

On Wed, Nov 13, 2019 at 1:41 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> See commit: 64604d54d311 ("sched/x86_64: Don't save flags on context switch")
>
> We need "only" make objtool support 32bit :)

Duh, I knew that.

Maybe just a comment in the structure and/or the __switch_to_asm() so
that next time I forget I won't look like such a tool.

The "Save callee-saved registers" comment we have now in the 32-bit
__switch_to_asm() really is misleading and incorrect wrt the pushfl.

            Linus

Re: [patch V3 02/20] x86/process: Unify copy_thread_tls()

[Thomas Gleixner]

On Wed, 13 Nov 2019, Linus Torvalds wrote:
> On Wed, Nov 13, 2019 at 1:41 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > See commit: 64604d54d311 ("sched/x86_64: Don't save flags on context switch")
> >
> > We need "only" make objtool support 32bit :)
> 
> Duh, I knew that.
> 
> Maybe just a comment in the structure and/or the __switch_to_asm() so
> that next time I forget I won't look like such a tool.
> 
> The "Save callee-saved registers" comment we have now in the 32-bit
> __switch_to_asm() really is misleading and incorrect wrt the pushfl.

Yeah. Let me fix that.

Thanks,

	tglx

Re: [patch V3 02/20] x86/process: Unify copy_thread_tls()

[Brian Gerst]

On Wed, Nov 13, 2019 at 4:14 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Wed, Nov 13, 2019 at 1:02 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > +int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
> > +                   unsigned long arg, struct task_struct *p, unsigned long tls)
> ...
> > +#ifdef CONFIG_X86_64
> ..
> > +#else
> > +       /* Clear all status flags including IF and set fixed bit. */
> > +       frame->flags = X86_EFLAGS_FIXED;
> > +#endif
>
> Hmm. The unification I like, but it also shows these differences that
> I don't remember the reason for.
>
> Remind me why __switch_to_asm() on 32-bit safes eflags, but we don't
> do it on x86-64?
>
> The comment just talks about callee-saved registers, but flags isn't
> callee-saved, so there's something else going on.
>
> This patch clearly doesn't change anything, I'm not complaining about
> the patch at all. I'm just wondering about the odd difference that the
> patch exposes.

It's to prevent AC from leaking into the next task.  objtool can
verify that 64-bit code doesn't schedule when AC is set, but it
doesn't work on 32-bit.  We could probably just do a CLAC on switch
and when it switches back to that task you would get an oops and it
would get noticed.  It's likely though that the 64-bit coverage has
fixed most of the places where this happened.

--
Brian Gerst

[tip: x86/iopl] x86/process: Unify copy_thread_tls()

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     320044006807464e3e80c11b3afbc08a57767f29
Gitweb:        https://git.kernel.org/tip/320044006807464e3e80c11b3afbc08a57767f29
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:42 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:14:59 +01:00

x86/process: Unify copy_thread_tls()

While looking at the TSS io bitmap it turned out that any change in that
area would require identical changes to copy_thread_tls(). The 32 and 64
bit variants share sufficient code to consolidate them into a common
function to avoid duplication of upcoming modifications.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210103.911310593@linutronix.de


---
 arch/x86/include/asm/ptrace.h    |  6 ++-
 arch/x86/include/asm/switch_to.h | 10 +++-
 arch/x86/kernel/process.c        | 94 +++++++++++++++++++++++++++++++-
 arch/x86/kernel/process_32.c     | 68 +----------------------
 arch/x86/kernel/process_64.c     | 75 +-------------------------
 5 files changed, 110 insertions(+), 143 deletions(-)

diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index 332eb35..5057a8e 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -361,5 +361,11 @@ extern int do_get_thread_area(struct task_struct *p, int idx,
 extern int do_set_thread_area(struct task_struct *p, int idx,
 			      struct user_desc __user *info, int can_allocate);
 
+#ifdef CONFIG_X86_64
+# define do_set_thread_area_64(p, s, t)	do_arch_prctl_64(p, s, t)
+#else
+# define do_set_thread_area_64(p, s, t)	(0)
+#endif
+
 #endif /* !__ASSEMBLY__ */
 #endif /* _ASM_X86_PTRACE_H */
diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index 18a4b68..0e059b7 100644
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -103,7 +103,17 @@ static inline void update_task_stack(struct task_struct *task)
 	if (static_cpu_has(X86_FEATURE_XENPV))
 		load_sp0(task_top_of_stack(task));
 #endif
+}
 
+static inline void kthread_frame_init(struct inactive_task_frame *frame,
+				      unsigned long fun, unsigned long arg)
+{
+	frame->bx = fun;
+#ifdef CONFIG_X86_32
+	frame->di = arg;
+#else
+	frame->r12 = arg;
+#endif
 }
 
 #endif /* _ASM_X86_SWITCH_TO_H */
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 5e94c43..c09130a 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -132,6 +132,100 @@ void exit_thread(struct task_struct *tsk)
 	fpu__drop(fpu);
 }
 
+static int set_new_tls(struct task_struct *p, unsigned long tls)
+{
+	struct user_desc __user *utls = (struct user_desc __user *)tls;
+
+	if (in_ia32_syscall())
+		return do_set_thread_area(p, -1, utls, 0);
+	else
+		return do_set_thread_area_64(p, ARCH_SET_FS, tls);
+}
+
+static inline int copy_io_bitmap(struct task_struct *tsk)
+{
+	if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP)))
+		return 0;
+
+	tsk->thread.io_bitmap_ptr = kmemdup(current->thread.io_bitmap_ptr,
+					    IO_BITMAP_BYTES, GFP_KERNEL);
+	if (!tsk->thread.io_bitmap_ptr) {
+		tsk->thread.io_bitmap_max = 0;
+		return -ENOMEM;
+	}
+	set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
+	return 0;
+}
+
+static inline void free_io_bitmap(struct task_struct *tsk)
+{
+	if (tsk->thread.io_bitmap_ptr) {
+		kfree(tsk->thread.io_bitmap_ptr);
+		tsk->thread.io_bitmap_ptr = NULL;
+		tsk->thread.io_bitmap_max = 0;
+	}
+}
+
+int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
+		    unsigned long arg, struct task_struct *p, unsigned long tls)
+{
+	struct inactive_task_frame *frame;
+	struct fork_frame *fork_frame;
+	struct pt_regs *childregs;
+	int ret;
+
+	childregs = task_pt_regs(p);
+	fork_frame = container_of(childregs, struct fork_frame, regs);
+	frame = &fork_frame->frame;
+
+	frame->bp = 0;
+	frame->ret_addr = (unsigned long) ret_from_fork;
+	p->thread.sp = (unsigned long) fork_frame;
+	p->thread.io_bitmap_ptr = NULL;
+	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
+
+#ifdef CONFIG_X86_64
+	savesegment(gs, p->thread.gsindex);
+	p->thread.gsbase = p->thread.gsindex ? 0 : current->thread.gsbase;
+	savesegment(fs, p->thread.fsindex);
+	p->thread.fsbase = p->thread.fsindex ? 0 : current->thread.fsbase;
+	savesegment(es, p->thread.es);
+	savesegment(ds, p->thread.ds);
+#else
+	/* Clear all status flags including IF and set fixed bit. */
+	frame->flags = X86_EFLAGS_FIXED;
+#endif
+
+	/* Kernel thread ? */
+	if (unlikely(p->flags & PF_KTHREAD)) {
+		memset(childregs, 0, sizeof(struct pt_regs));
+		kthread_frame_init(frame, sp, arg);
+		return 0;
+	}
+
+	frame->bx = 0;
+	*childregs = *current_pt_regs();
+	childregs->ax = 0;
+	if (sp)
+		childregs->sp = sp;
+
+#ifdef CONFIG_X86_32
+	task_user_gs(p) = get_user_gs(current_pt_regs());
+#endif
+
+	ret = copy_io_bitmap(p);
+	if (ret)
+		return ret;
+
+	/* Set a new TLS for the child thread? */
+	if (clone_flags & CLONE_SETTLS) {
+		ret = set_new_tls(p, tls);
+		if (ret)
+			free_io_bitmap(p);
+	}
+	return ret;
+}
+
 void flush_thread(void)
 {
 	struct task_struct *tsk = current;
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index b8ceec4..6c7d905 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -112,74 +112,6 @@ void release_thread(struct task_struct *dead_task)
 	release_vm86_irqs(dead_task);
 }
 
-int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
-	unsigned long arg, struct task_struct *p, unsigned long tls)
-{
-	struct pt_regs *childregs = task_pt_regs(p);
-	struct fork_frame *fork_frame = container_of(childregs, struct fork_frame, regs);
-	struct inactive_task_frame *frame = &fork_frame->frame;
-	struct task_struct *tsk;
-	int err;
-
-	/*
-	 * For a new task use the RESET flags value since there is no before.
-	 * All the status flags are zero; DF and all the system flags must also
-	 * be 0, specifically IF must be 0 because we context switch to the new
-	 * task with interrupts disabled.
-	 */
-	frame->flags = X86_EFLAGS_FIXED;
-	frame->bp = 0;
-	frame->ret_addr = (unsigned long) ret_from_fork;
-	p->thread.sp = (unsigned long) fork_frame;
-	p->thread.sp0 = (unsigned long) (childregs+1);
-	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
-
-	if (unlikely(p->flags & PF_KTHREAD)) {
-		/* kernel thread */
-		memset(childregs, 0, sizeof(struct pt_regs));
-		frame->bx = sp;		/* function */
-		frame->di = arg;
-		p->thread.io_bitmap_ptr = NULL;
-		return 0;
-	}
-	frame->bx = 0;
-	*childregs = *current_pt_regs();
-	childregs->ax = 0;
-	if (sp)
-		childregs->sp = sp;
-
-	task_user_gs(p) = get_user_gs(current_pt_regs());
-
-	p->thread.io_bitmap_ptr = NULL;
-	tsk = current;
-	err = -ENOMEM;
-
-	if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
-		p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
-						IO_BITMAP_BYTES, GFP_KERNEL);
-		if (!p->thread.io_bitmap_ptr) {
-			p->thread.io_bitmap_max = 0;
-			return -ENOMEM;
-		}
-		set_tsk_thread_flag(p, TIF_IO_BITMAP);
-	}
-
-	err = 0;
-
-	/*
-	 * Set a new TLS for the child thread?
-	 */
-	if (clone_flags & CLONE_SETTLS)
-		err = do_set_thread_area(p, -1,
-			(struct user_desc __user *)tls, 0);
-
-	if (err && p->thread.io_bitmap_ptr) {
-		kfree(p->thread.io_bitmap_ptr);
-		p->thread.io_bitmap_max = 0;
-	}
-	return err;
-}
-
 void
 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
 {
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index af64519..e93a1b8 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -371,81 +371,6 @@ void x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase)
 	task->thread.gsbase = gsbase;
 }
 
-int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
-		unsigned long arg, struct task_struct *p, unsigned long tls)
-{
-	int err;
-	struct pt_regs *childregs;
-	struct fork_frame *fork_frame;
-	struct inactive_task_frame *frame;
-	struct task_struct *me = current;
-
-	childregs = task_pt_regs(p);
-	fork_frame = container_of(childregs, struct fork_frame, regs);
-	frame = &fork_frame->frame;
-
-	frame->bp = 0;
-	frame->ret_addr = (unsigned long) ret_from_fork;
-	p->thread.sp = (unsigned long) fork_frame;
-	p->thread.io_bitmap_ptr = NULL;
-
-	savesegment(gs, p->thread.gsindex);
-	p->thread.gsbase = p->thread.gsindex ? 0 : me->thread.gsbase;
-	savesegment(fs, p->thread.fsindex);
-	p->thread.fsbase = p->thread.fsindex ? 0 : me->thread.fsbase;
-	savesegment(es, p->thread.es);
-	savesegment(ds, p->thread.ds);
-	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
-
-	if (unlikely(p->flags & PF_KTHREAD)) {
-		/* kernel thread */
-		memset(childregs, 0, sizeof(struct pt_regs));
-		frame->bx = sp;		/* function */
-		frame->r12 = arg;
-		return 0;
-	}
-	frame->bx = 0;
-	*childregs = *current_pt_regs();
-
-	childregs->ax = 0;
-	if (sp)
-		childregs->sp = sp;
-
-	err = -ENOMEM;
-	if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
-		p->thread.io_bitmap_ptr = kmemdup(me->thread.io_bitmap_ptr,
-						  IO_BITMAP_BYTES, GFP_KERNEL);
-		if (!p->thread.io_bitmap_ptr) {
-			p->thread.io_bitmap_max = 0;
-			return -ENOMEM;
-		}
-		set_tsk_thread_flag(p, TIF_IO_BITMAP);
-	}
-
-	/*
-	 * Set a new TLS for the child thread?
-	 */
-	if (clone_flags & CLONE_SETTLS) {
-#ifdef CONFIG_IA32_EMULATION
-		if (in_ia32_syscall())
-			err = do_set_thread_area(p, -1,
-				(struct user_desc __user *)tls, 0);
-		else
-#endif
-			err = do_arch_prctl_64(p, ARCH_SET_FS, tls);
-		if (err)
-			goto out;
-	}
-	err = 0;
-out:
-	if (err && p->thread.io_bitmap_ptr) {
-		kfree(p->thread.io_bitmap_ptr);
-		p->thread.io_bitmap_max = 0;
-	}
-
-	return err;
-}
-
 static void
 start_thread_common(struct pt_regs *regs, unsigned long new_ip,
 		    unsigned long new_sp,

[patch V3 03/20] x86/cpu: Unify cpu_init()

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

Similar to copy_thread_tls() the 32bit and 64bit implementations of
cpu_init() are very similar and unification avoids duplicate changes in the
future.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>

---
V2: Fix 32bit build by removing the pointless #ifdef around the uv header include.
---
 arch/x86/kernel/cpu/common.c |  175 ++++++++++++++++---------------------------
 1 file changed, 66 insertions(+), 109 deletions(-)

--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -53,10 +53,7 @@
 #include <asm/microcode_intel.h>
 #include <asm/intel-family.h>
 #include <asm/cpu_device_id.h>
-
-#ifdef CONFIG_X86_LOCAL_APIC
 #include <asm/uv/uv.h>
-#endif
 
 #include "cpu.h"
 
@@ -1749,7 +1746,7 @@ static void wait_for_master_cpu(int cpu)
 }
 
 #ifdef CONFIG_X86_64
-static void setup_getcpu(int cpu)
+static inline void setup_getcpu(int cpu)
 {
 	unsigned long cpudata = vdso_encode_cpunode(cpu, early_cpu_to_node(cpu));
 	struct desc_struct d = { };
@@ -1769,7 +1766,43 @@ static void setup_getcpu(int cpu)
 
 	write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_CPUNODE, &d, DESCTYPE_S);
 }
+
+static inline void ucode_cpu_init(int cpu)
+{
+	if (cpu)
+		load_ucode_ap();
+}
+
+static inline void tss_setup_ist(struct tss_struct *tss)
+{
+	/* Set up the per-CPU TSS IST stacks */
+	tss->x86_tss.ist[IST_INDEX_DF] = __this_cpu_ist_top_va(DF);
+	tss->x86_tss.ist[IST_INDEX_NMI] = __this_cpu_ist_top_va(NMI);
+	tss->x86_tss.ist[IST_INDEX_DB] = __this_cpu_ist_top_va(DB);
+	tss->x86_tss.ist[IST_INDEX_MCE] = __this_cpu_ist_top_va(MCE);
+}
+
+static inline void gdt_setup_doublefault_tss(int cpu) { }
+
+#else /* CONFIG_X86_64 */
+
+static inline void setup_getcpu(int cpu) { }
+
+static inline void ucode_cpu_init(int cpu)
+{
+	show_ucode_info_early();
+}
+
+static inline void tss_setup_ist(struct tss_struct *tss) { }
+
+static inline void gdt_setup_doublefault_tss(int cpu)
+{
+#ifdef CONFIG_DOUBLEFAULT
+	/* Set up the doublefault TSS pointer in the GDT */
+	__set_tss_desc(cpu, GDT_ENTRY_DOUBLEFAULT_TSS, &doublefault_tss);
 #endif
+}
+#endif /* !CONFIG_X86_64 */
 
 /*
  * cpu_init() initializes state that is per-CPU. Some data is already
@@ -1777,21 +1810,15 @@ static void setup_getcpu(int cpu)
  * and IDT. We reload them nevertheless, this function acts as a
  * 'CPU state barrier', nothing should get across.
  */
-#ifdef CONFIG_X86_64
-
 void cpu_init(void)
 {
+	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
+	struct task_struct *cur = current;
 	int cpu = raw_smp_processor_id();
-	struct task_struct *me;
-	struct tss_struct *t;
-	int i;
 
 	wait_for_master_cpu(cpu);
 
-	if (cpu)
-		load_ucode_ap();
-
-	t = &per_cpu(cpu_tss_rw, cpu);
+	ucode_cpu_init(cpu);
 
 #ifdef CONFIG_NUMA
 	if (this_cpu_read(numa_node) == 0 &&
@@ -1800,63 +1827,48 @@ void cpu_init(void)
 #endif
 	setup_getcpu(cpu);
 
-	me = current;
-
 	pr_debug("Initializing CPU#%d\n", cpu);
 
-	cr4_clear_bits(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);
+	if (IS_ENABLED(CONFIG_X86_64) || cpu_feature_enabled(X86_FEATURE_VME) ||
+	    boot_cpu_has(X86_FEATURE_TSC) || boot_cpu_has(X86_FEATURE_DE))
+		cr4_clear_bits(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);
 
 	/*
 	 * Initialize the per-CPU GDT with the boot GDT,
 	 * and set up the GDT descriptor:
 	 */
-
 	switch_to_new_gdt(cpu);
-	loadsegment(fs, 0);
-
 	load_current_idt();
 
-	memset(me->thread.tls_array, 0, GDT_ENTRY_TLS_ENTRIES * 8);
-	syscall_init();
+	if (IS_ENABLED(CONFIG_X86_64)) {
+		loadsegment(fs, 0);
+		memset(cur->thread.tls_array, 0, GDT_ENTRY_TLS_ENTRIES * 8);
+		syscall_init();
+
+		wrmsrl(MSR_FS_BASE, 0);
+		wrmsrl(MSR_KERNEL_GS_BASE, 0);
+		barrier();
 
-	wrmsrl(MSR_FS_BASE, 0);
-	wrmsrl(MSR_KERNEL_GS_BASE, 0);
-	barrier();
-
-	x86_configure_nx();
-	x2apic_setup();
-
-	/*
-	 * set up and load the per-CPU TSS
-	 */
-	if (!t->x86_tss.ist[0]) {
-		t->x86_tss.ist[IST_INDEX_DF] = __this_cpu_ist_top_va(DF);
-		t->x86_tss.ist[IST_INDEX_NMI] = __this_cpu_ist_top_va(NMI);
-		t->x86_tss.ist[IST_INDEX_DB] = __this_cpu_ist_top_va(DB);
-		t->x86_tss.ist[IST_INDEX_MCE] = __this_cpu_ist_top_va(MCE);
+		x2apic_setup();
 	}
 
-	t->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
-
-	/*
-	 * <= is required because the CPU will access up to
-	 * 8 bits beyond the end of the IO permission bitmap.
-	 */
-	for (i = 0; i <= IO_BITMAP_LONGS; i++)
-		t->io_bitmap[i] = ~0UL;
-
 	mmgrab(&init_mm);
-	me->active_mm = &init_mm;
-	BUG_ON(me->mm);
+	cur->active_mm = &init_mm;
+	BUG_ON(cur->mm);
 	initialize_tlbstate_and_flush();
-	enter_lazy_tlb(&init_mm, me);
+	enter_lazy_tlb(&init_mm, cur);
 
-	/*
-	 * Initialize the TSS.  sp0 points to the entry trampoline stack
-	 * regardless of what task is running.
-	 */
+	/* Initialize the TSS. */
+	tss_setup_ist(tss);
+	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
+	memset(tss->io_bitmap, 0xff, sizeof(tss->io_bitmap));
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
+
 	load_TR_desc();
+	/*
+	 * sp0 points to the entry trampoline stack regardless of what task
+	 * is running.
+	 */
 	load_sp0((unsigned long)(cpu_entry_stack(cpu) + 1));
 
 	load_mm_ldt(&init_mm);
@@ -1864,6 +1876,8 @@ void cpu_init(void)
 	clear_all_debug_regs();
 	dbg_restore_debug_regs();
 
+	gdt_setup_doublefault_tss(cpu);
+
 	fpu__init_cpu();
 
 	if (is_uv_system())
@@ -1872,63 +1886,6 @@ void cpu_init(void)
 	load_fixmap_gdt(cpu);
 }
 
-#else
-
-void cpu_init(void)
-{
-	int cpu = smp_processor_id();
-	struct task_struct *curr = current;
-	struct tss_struct *t = &per_cpu(cpu_tss_rw, cpu);
-
-	wait_for_master_cpu(cpu);
-
-	show_ucode_info_early();
-
-	pr_info("Initializing CPU#%d\n", cpu);
-
-	if (cpu_feature_enabled(X86_FEATURE_VME) ||
-	    boot_cpu_has(X86_FEATURE_TSC) ||
-	    boot_cpu_has(X86_FEATURE_DE))
-		cr4_clear_bits(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);
-
-	load_current_idt();
-	switch_to_new_gdt(cpu);
-
-	/*
-	 * Set up and load the per-CPU TSS and LDT
-	 */
-	mmgrab(&init_mm);
-	curr->active_mm = &init_mm;
-	BUG_ON(curr->mm);
-	initialize_tlbstate_and_flush();
-	enter_lazy_tlb(&init_mm, curr);
-
-	/*
-	 * Initialize the TSS.  sp0 points to the entry trampoline stack
-	 * regardless of what task is running.
-	 */
-	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
-	load_TR_desc();
-	load_sp0((unsigned long)(cpu_entry_stack(cpu) + 1));
-
-	load_mm_ldt(&init_mm);
-
-	t->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
-
-#ifdef CONFIG_DOUBLEFAULT
-	/* Set up doublefault TSS pointer in the GDT */
-	__set_tss_desc(cpu, GDT_ENTRY_DOUBLEFAULT_TSS, &doublefault_tss);
-#endif
-
-	clear_all_debug_regs();
-	dbg_restore_debug_regs();
-
-	fpu__init_cpu();
-
-	load_fixmap_gdt(cpu);
-}
-#endif
-
 /*
  * The microcode loader calls this upon late microcode load to recheck features,
  * only when microcode has been updated. Caller holds microcode_mutex and CPU

[tip: x86/iopl] x86/cpu: Unify cpu_init()

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     fff628d736f261ab0bebb94f97678710f48df75e
Gitweb:        https://git.kernel.org/tip/fff628d736f261ab0bebb94f97678710f48df75e
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:43 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:00 +01:00

x86/cpu: Unify cpu_init()

Similar to copy_thread_tls() the 32bit and 64bit implementations of
cpu_init() are very similar and unification avoids duplicate changes in the
future.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.002114856@linutronix.de


---
 arch/x86/kernel/cpu/common.c | 173 ++++++++++++----------------------
 1 file changed, 65 insertions(+), 108 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9ae7d1b..d52ec1a 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -53,10 +53,7 @@
 #include <asm/microcode_intel.h>
 #include <asm/intel-family.h>
 #include <asm/cpu_device_id.h>
-
-#ifdef CONFIG_X86_LOCAL_APIC
 #include <asm/uv/uv.h>
-#endif
 
 #include "cpu.h"
 
@@ -1749,7 +1746,7 @@ static void wait_for_master_cpu(int cpu)
 }
 
 #ifdef CONFIG_X86_64
-static void setup_getcpu(int cpu)
+static inline void setup_getcpu(int cpu)
 {
 	unsigned long cpudata = vdso_encode_cpunode(cpu, early_cpu_to_node(cpu));
 	struct desc_struct d = { };
@@ -1769,7 +1766,43 @@ static void setup_getcpu(int cpu)
 
 	write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_CPUNODE, &d, DESCTYPE_S);
 }
+
+static inline void ucode_cpu_init(int cpu)
+{
+	if (cpu)
+		load_ucode_ap();
+}
+
+static inline void tss_setup_ist(struct tss_struct *tss)
+{
+	/* Set up the per-CPU TSS IST stacks */
+	tss->x86_tss.ist[IST_INDEX_DF] = __this_cpu_ist_top_va(DF);
+	tss->x86_tss.ist[IST_INDEX_NMI] = __this_cpu_ist_top_va(NMI);
+	tss->x86_tss.ist[IST_INDEX_DB] = __this_cpu_ist_top_va(DB);
+	tss->x86_tss.ist[IST_INDEX_MCE] = __this_cpu_ist_top_va(MCE);
+}
+
+static inline void gdt_setup_doublefault_tss(int cpu) { }
+
+#else /* CONFIG_X86_64 */
+
+static inline void setup_getcpu(int cpu) { }
+
+static inline void ucode_cpu_init(int cpu)
+{
+	show_ucode_info_early();
+}
+
+static inline void tss_setup_ist(struct tss_struct *tss) { }
+
+static inline void gdt_setup_doublefault_tss(int cpu)
+{
+#ifdef CONFIG_DOUBLEFAULT
+	/* Set up the doublefault TSS pointer in the GDT */
+	__set_tss_desc(cpu, GDT_ENTRY_DOUBLEFAULT_TSS, &doublefault_tss);
 #endif
+}
+#endif /* !CONFIG_X86_64 */
 
 /*
  * cpu_init() initializes state that is per-CPU. Some data is already
@@ -1777,21 +1810,15 @@ static void setup_getcpu(int cpu)
  * and IDT. We reload them nevertheless, this function acts as a
  * 'CPU state barrier', nothing should get across.
  */
-#ifdef CONFIG_X86_64
-
 void cpu_init(void)
 {
+	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
+	struct task_struct *cur = current;
 	int cpu = raw_smp_processor_id();
-	struct task_struct *me;
-	struct tss_struct *t;
-	int i;
 
 	wait_for_master_cpu(cpu);
 
-	if (cpu)
-		load_ucode_ap();
-
-	t = &per_cpu(cpu_tss_rw, cpu);
+	ucode_cpu_init(cpu);
 
 #ifdef CONFIG_NUMA
 	if (this_cpu_read(numa_node) == 0 &&
@@ -1800,63 +1827,48 @@ void cpu_init(void)
 #endif
 	setup_getcpu(cpu);
 
-	me = current;
-
 	pr_debug("Initializing CPU#%d\n", cpu);
 
-	cr4_clear_bits(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);
+	if (IS_ENABLED(CONFIG_X86_64) || cpu_feature_enabled(X86_FEATURE_VME) ||
+	    boot_cpu_has(X86_FEATURE_TSC) || boot_cpu_has(X86_FEATURE_DE))
+		cr4_clear_bits(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);
 
 	/*
 	 * Initialize the per-CPU GDT with the boot GDT,
 	 * and set up the GDT descriptor:
 	 */
-
 	switch_to_new_gdt(cpu);
-	loadsegment(fs, 0);
-
 	load_current_idt();
 
-	memset(me->thread.tls_array, 0, GDT_ENTRY_TLS_ENTRIES * 8);
-	syscall_init();
+	if (IS_ENABLED(CONFIG_X86_64)) {
+		loadsegment(fs, 0);
+		memset(cur->thread.tls_array, 0, GDT_ENTRY_TLS_ENTRIES * 8);
+		syscall_init();
 
-	wrmsrl(MSR_FS_BASE, 0);
-	wrmsrl(MSR_KERNEL_GS_BASE, 0);
-	barrier();
+		wrmsrl(MSR_FS_BASE, 0);
+		wrmsrl(MSR_KERNEL_GS_BASE, 0);
+		barrier();
 
-	x86_configure_nx();
-	x2apic_setup();
-
-	/*
-	 * set up and load the per-CPU TSS
-	 */
-	if (!t->x86_tss.ist[0]) {
-		t->x86_tss.ist[IST_INDEX_DF] = __this_cpu_ist_top_va(DF);
-		t->x86_tss.ist[IST_INDEX_NMI] = __this_cpu_ist_top_va(NMI);
-		t->x86_tss.ist[IST_INDEX_DB] = __this_cpu_ist_top_va(DB);
-		t->x86_tss.ist[IST_INDEX_MCE] = __this_cpu_ist_top_va(MCE);
+		x2apic_setup();
 	}
 
-	t->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
-
-	/*
-	 * <= is required because the CPU will access up to
-	 * 8 bits beyond the end of the IO permission bitmap.
-	 */
-	for (i = 0; i <= IO_BITMAP_LONGS; i++)
-		t->io_bitmap[i] = ~0UL;
-
 	mmgrab(&init_mm);
-	me->active_mm = &init_mm;
-	BUG_ON(me->mm);
+	cur->active_mm = &init_mm;
+	BUG_ON(cur->mm);
 	initialize_tlbstate_and_flush();
-	enter_lazy_tlb(&init_mm, me);
+	enter_lazy_tlb(&init_mm, cur);
 
-	/*
-	 * Initialize the TSS.  sp0 points to the entry trampoline stack
-	 * regardless of what task is running.
-	 */
+	/* Initialize the TSS. */
+	tss_setup_ist(tss);
+	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
+	memset(tss->io_bitmap, 0xff, sizeof(tss->io_bitmap));
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
+
 	load_TR_desc();
+	/*
+	 * sp0 points to the entry trampoline stack regardless of what task
+	 * is running.
+	 */
 	load_sp0((unsigned long)(cpu_entry_stack(cpu) + 1));
 
 	load_mm_ldt(&init_mm);
@@ -1864,6 +1876,8 @@ void cpu_init(void)
 	clear_all_debug_regs();
 	dbg_restore_debug_regs();
 
+	gdt_setup_doublefault_tss(cpu);
+
 	fpu__init_cpu();
 
 	if (is_uv_system())
@@ -1872,63 +1886,6 @@ void cpu_init(void)
 	load_fixmap_gdt(cpu);
 }
 
-#else
-
-void cpu_init(void)
-{
-	int cpu = smp_processor_id();
-	struct task_struct *curr = current;
-	struct tss_struct *t = &per_cpu(cpu_tss_rw, cpu);
-
-	wait_for_master_cpu(cpu);
-
-	show_ucode_info_early();
-
-	pr_info("Initializing CPU#%d\n", cpu);
-
-	if (cpu_feature_enabled(X86_FEATURE_VME) ||
-	    boot_cpu_has(X86_FEATURE_TSC) ||
-	    boot_cpu_has(X86_FEATURE_DE))
-		cr4_clear_bits(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);
-
-	load_current_idt();
-	switch_to_new_gdt(cpu);
-
-	/*
-	 * Set up and load the per-CPU TSS and LDT
-	 */
-	mmgrab(&init_mm);
-	curr->active_mm = &init_mm;
-	BUG_ON(curr->mm);
-	initialize_tlbstate_and_flush();
-	enter_lazy_tlb(&init_mm, curr);
-
-	/*
-	 * Initialize the TSS.  sp0 points to the entry trampoline stack
-	 * regardless of what task is running.
-	 */
-	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
-	load_TR_desc();
-	load_sp0((unsigned long)(cpu_entry_stack(cpu) + 1));
-
-	load_mm_ldt(&init_mm);
-
-	t->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
-
-#ifdef CONFIG_DOUBLEFAULT
-	/* Set up doublefault TSS pointer in the GDT */
-	__set_tss_desc(cpu, GDT_ENTRY_DOUBLEFAULT_TSS, &doublefault_tss);
-#endif
-
-	clear_all_debug_regs();
-	dbg_restore_debug_regs();
-
-	fpu__init_cpu();
-
-	load_fixmap_gdt(cpu);
-}
-#endif
-
 /*
  * The microcode loader calls this upon late microcode load to recheck features,
  * only when microcode has been updated. Caller holds microcode_mutex and CPU

[patch V3 04/20] x86/tss: Fix and move VMX BUILD_BUG_ON()

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

The BUILD_BUG_ON(IO_BITMAP_OFFSET - 1 == 0x67) in the VMX code is bogus in
two aspects:

1) This wants to be in generic x86 code simply to catch issues even when
   VMX is disabled in Kconfig.

2) The IO_BITMAP_OFFSET is not the right thing to check because it makes
   asssumptions about the layout of tss_struct. Nothing requires that the
   I/O bitmap is placed right after x86_tss, which is the hardware mandated
   tss structure. It pointlessly makes restrictions on the struct
   tss_struct layout.

The proper thing to check is:

    - Offset of x86_tss in tss_struct is 0
    - Size of x86_tss == 0x68

Move it to the other build time TSS checks and make it do the right thing.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Andy Lutomirski <luto@kernel.org>

---
V2: New patch
---
 arch/x86/kvm/vmx/vmx.c       |    8 --------
 arch/x86/mm/cpu_entry_area.c |    8 ++++++++
 2 files changed, 8 insertions(+), 8 deletions(-)

--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1338,14 +1338,6 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu
 			    (unsigned long)&get_cpu_entry_area(cpu)->tss.x86_tss);
 		vmcs_writel(HOST_GDTR_BASE, (unsigned long)gdt);   /* 22.2.4 */
 
-		/*
-		 * VM exits change the host TR limit to 0x67 after a VM
-		 * exit.  This is okay, since 0x67 covers everything except
-		 * the IO bitmap and have have code to handle the IO bitmap
-		 * being lost after a VM exit.
-		 */
-		BUILD_BUG_ON(IO_BITMAP_OFFSET - 1 != 0x67);
-
 		rdmsrl(MSR_IA32_SYSENTER_ESP, sysenter_esp);
 		vmcs_writel(HOST_IA32_SYSENTER_ESP, sysenter_esp); /* 22.2.3 */
 
--- a/arch/x86/mm/cpu_entry_area.c
+++ b/arch/x86/mm/cpu_entry_area.c
@@ -161,6 +161,14 @@ static void __init setup_cpu_entry_area(
 	BUILD_BUG_ON((offsetof(struct tss_struct, x86_tss) ^
 		      offsetofend(struct tss_struct, x86_tss)) & PAGE_MASK);
 	BUILD_BUG_ON(sizeof(struct tss_struct) % PAGE_SIZE != 0);
+	/*
+	 * VMX changes the host TR limit to 0x67 after a VM exit. This is
+	 * okay, since 0x67 covers the size of struct x86_hw_tss. Make sure
+	 * that this is correct.
+	 */
+	BUILD_BUG_ON(offsetof(struct tss_struct, x86_tss) != 0);
+	BUILD_BUG_ON(sizeof(struct x86_hw_tss) != 0x68);
+
 	cea_map_percpu_pages(&cea->tss, &per_cpu(cpu_tss_rw, cpu),
 			     sizeof(struct tss_struct) / PAGE_SIZE, tss_prot);
 

[tip: x86/iopl] x86/tss: Fix and move VMX BUILD_BUG_ON()

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     4dee588dc12914966faf902932238cb09a493d1c
Gitweb:        https://git.kernel.org/tip/4dee588dc12914966faf902932238cb09a493d1c
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:44 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:00 +01:00

x86/tss: Fix and move VMX BUILD_BUG_ON()

The BUILD_BUG_ON(IO_BITMAP_OFFSET - 1 == 0x67) in the VMX code is bogus in
two aspects:

1) This wants to be in generic x86 code simply to catch issues even when
   VMX is disabled in Kconfig.

2) The IO_BITMAP_OFFSET is not the right thing to check because it makes
   asssumptions about the layout of tss_struct. Nothing requires that the
   I/O bitmap is placed right after x86_tss, which is the hardware mandated
   tss structure. It pointlessly makes restrictions on the struct
   tss_struct layout.

The proper thing to check is:

    - Offset of x86_tss in tss_struct is 0
    - Size of x86_tss == 0x68

Move it to the other build time TSS checks and make it do the right thing.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.097140143@linutronix.de


---
 arch/x86/kvm/vmx/vmx.c       | 8 --------
 arch/x86/mm/cpu_entry_area.c | 8 ++++++++
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 5d21a4a..311fd48 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1338,14 +1338,6 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu)
 			    (unsigned long)&get_cpu_entry_area(cpu)->tss.x86_tss);
 		vmcs_writel(HOST_GDTR_BASE, (unsigned long)gdt);   /* 22.2.4 */
 
-		/*
-		 * VM exits change the host TR limit to 0x67 after a VM
-		 * exit.  This is okay, since 0x67 covers everything except
-		 * the IO bitmap and have have code to handle the IO bitmap
-		 * being lost after a VM exit.
-		 */
-		BUILD_BUG_ON(IO_BITMAP_OFFSET - 1 != 0x67);
-
 		rdmsrl(MSR_IA32_SYSENTER_ESP, sysenter_esp);
 		vmcs_writel(HOST_IA32_SYSENTER_ESP, sysenter_esp); /* 22.2.3 */
 
diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c
index 752ad11..2c1d422 100644
--- a/arch/x86/mm/cpu_entry_area.c
+++ b/arch/x86/mm/cpu_entry_area.c
@@ -161,6 +161,14 @@ static void __init setup_cpu_entry_area(unsigned int cpu)
 	BUILD_BUG_ON((offsetof(struct tss_struct, x86_tss) ^
 		      offsetofend(struct tss_struct, x86_tss)) & PAGE_MASK);
 	BUILD_BUG_ON(sizeof(struct tss_struct) % PAGE_SIZE != 0);
+	/*
+	 * VMX changes the host TR limit to 0x67 after a VM exit. This is
+	 * okay, since 0x67 covers the size of struct x86_hw_tss. Make sure
+	 * that this is correct.
+	 */
+	BUILD_BUG_ON(offsetof(struct tss_struct, x86_tss) != 0);
+	BUILD_BUG_ON(sizeof(struct x86_hw_tss) != 0x68);
+
 	cea_map_percpu_pages(&cea->tss, &per_cpu(cpu_tss_rw, cpu),
 			     sizeof(struct tss_struct) / PAGE_SIZE, tss_prot);
 

[patch V3 05/20] x86/iopl: Cleanup include maze

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

Get rid of superfluous includes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>

---
V2: New patch
---
 arch/x86/kernel/ioport.c |   16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -3,22 +3,14 @@
  * This contains the io-permission bitmap code - written by obz, with changes
  * by Linus. 32/64 bits code unification by Miguel Botón.
  */
-
-#include <linux/sched.h>
-#include <linux/sched/task_stack.h>
-#include <linux/kernel.h>
 #include <linux/capability.h>
-#include <linux/errno.h>
-#include <linux/types.h>
-#include <linux/ioport.h>
 #include <linux/security.h>
-#include <linux/smp.h>
-#include <linux/stddef.h>
-#include <linux/slab.h>
-#include <linux/thread_info.h>
 #include <linux/syscalls.h>
 #include <linux/bitmap.h>
-#include <asm/syscalls.h>
+#include <linux/ioport.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
 #include <asm/desc.h>
 
 /*

[tip: x86/iopl] x86/iopl: Cleanup include maze

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     2a03b5d8fe438f798aa4c764779d3d8e0e0710d5
Gitweb:        https://git.kernel.org/tip/2a03b5d8fe438f798aa4c764779d3d8e0e0710d5
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:45 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:01 +01:00

x86/iopl: Cleanup include maze

Get rid of superfluous includes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.203489329@linutronix.de


---
 arch/x86/kernel/ioport.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 61a89d3..76fc2ef 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -3,22 +3,14 @@
  * This contains the io-permission bitmap code - written by obz, with changes
  * by Linus. 32/64 bits code unification by Miguel Botón.
  */
-
-#include <linux/sched.h>
-#include <linux/sched/task_stack.h>
-#include <linux/kernel.h>
 #include <linux/capability.h>
-#include <linux/errno.h>
-#include <linux/types.h>
-#include <linux/ioport.h>
 #include <linux/security.h>
-#include <linux/smp.h>
-#include <linux/stddef.h>
-#include <linux/slab.h>
-#include <linux/thread_info.h>
 #include <linux/syscalls.h>
 #include <linux/bitmap.h>
-#include <asm/syscalls.h>
+#include <linux/ioport.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
 #include <asm/desc.h>
 
 /*

[patch V3 06/20] x86/ioperm: Simplify first ioperm() invocation logic

[Thomas Gleixner]

On the first allocation of a task the I/O bitmap needs to be
allocated. After the allocation it is installed as an empty bitmap and
immediately afterwards updated.

Avoid that and just do the initial updates (store bitmap pointer, set TIF
flag and make TSS limit valid) in the update path unconditionally. If the
bitmap was already active this is redundant but harmless.

Preparatory change for later optimizations in the context switch code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V3: Split out from a later patch for simpler review and to make the first
    context switch optimization correct.
---
 arch/x86/kernel/ioport.c |   57 +++++++++++++++++++++++------------------------
 1 file changed, 28 insertions(+), 29 deletions(-)

--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -18,9 +18,10 @@
  */
 long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 {
+	unsigned int i, max_long, bytes, bytes_updated;
 	struct thread_struct *t = &current->thread;
 	struct tss_struct *tss;
-	unsigned int i, max_long, bytes, bytes_updated;
+	unsigned long *bitmap;
 
 	if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
 		return -EINVAL;
@@ -33,59 +34,57 @@ long ksys_ioperm(unsigned long from, uns
 	 * IO bitmap up. ioperm() is much less timing critical than clone(),
 	 * this is why we delay this operation until now:
 	 */
-	if (!t->io_bitmap_ptr) {
-		unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
-
+	bitmap = t->io_bitmap_ptr;
+	if (!bitmap) {
+		bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
 		if (!bitmap)
 			return -ENOMEM;
 
 		memset(bitmap, 0xff, IO_BITMAP_BYTES);
-		t->io_bitmap_ptr = bitmap;
-		set_thread_flag(TIF_IO_BITMAP);
-
-		/*
-		 * Now that we have an IO bitmap, we need our TSS limit to be
-		 * correct.  It's fine if we are preempted after doing this:
-		 * with TIF_IO_BITMAP set, context switches will keep our TSS
-		 * limit correct.
-		 */
-		preempt_disable();
-		refresh_tss_limit();
-		preempt_enable();
 	}
 
 	/*
-	 * do it in the per-thread copy and in the TSS ...
-	 *
-	 * Disable preemption via get_cpu() - we must not switch away
-	 * because the ->io_bitmap_max value must match the bitmap
-	 * contents:
+	 * Update the bitmap and the TSS copy with preemption disabled to
+	 * prevent a race against context switch.
 	 */
-	tss = &per_cpu(cpu_tss_rw, get_cpu());
-
+	preempt_disable();
 	if (turn_on)
-		bitmap_clear(t->io_bitmap_ptr, from, num);
+		bitmap_clear(bitmap, from, num);
 	else
-		bitmap_set(t->io_bitmap_ptr, from, num);
+		bitmap_set(bitmap, from, num);
 
 	/*
 	 * Search for a (possibly new) maximum. This is simple and stupid,
 	 * to keep it obviously correct:
 	 */
 	max_long = 0;
-	for (i = 0; i < IO_BITMAP_LONGS; i++)
-		if (t->io_bitmap_ptr[i] != ~0UL)
+	for (i = 0; i < IO_BITMAP_LONGS; i++) {
+		if (bitmap[i] != ~0UL)
 			max_long = i;
+	}
 
 	bytes = (max_long + 1) * sizeof(unsigned long);
 	bytes_updated = max(bytes, t->io_bitmap_max);
 
+	/* Update the thread data */
 	t->io_bitmap_max = bytes;
+	/*
+	 * Store the bitmap pointer (might be the same if the task already
+	 * head one). Set the TIF flag, just in case this is the first
+	 * invocation.
+	 */
+	t->io_bitmap_ptr = bitmap;
+	set_thread_flag(TIF_IO_BITMAP);
 
-	/* Update the TSS: */
+	/* Update the TSS */
+	tss = this_cpu_ptr(&cpu_tss_rw);
 	memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
+	/* Store the new end of the zero bits */
+	tss->io_bitmap_prev_max = bytes;
+	/* Make sure the TSS limit covers the I/O bitmap. */
+	refresh_tss_limit();
 
-	put_cpu();
+	preempt_enable();
 
 	return 0;
 }

[tip: x86/iopl] x86/ioperm: Simplify first ioperm() invocation logic

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     3817927e6f5686a5c7571ae33f7b1a8483821c5b
Gitweb:        https://git.kernel.org/tip/3817927e6f5686a5c7571ae33f7b1a8483821c5b
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:46 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:01 +01:00

x86/ioperm: Simplify first ioperm() invocation logic

On the first allocation of a task the I/O bitmap needs to be
allocated. After the allocation it is installed as an empty bitmap and
immediately afterwards updated.

Avoid that and just do the initial updates (store bitmap pointer, set TIF
flag and make TSS limit valid) in the update path unconditionally. If the
bitmap was already active this is redundant but harmless.

Preparatory change for later optimizations in the context switch code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.295618595@linutronix.de

---
 arch/x86/kernel/ioport.c | 55 ++++++++++++++++++---------------------
 1 file changed, 26 insertions(+), 29 deletions(-)

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 76fc2ef..ca6aa1e 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -18,9 +18,10 @@
  */
 long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 {
+	unsigned int i, max_long, bytes, bytes_updated;
 	struct thread_struct *t = &current->thread;
 	struct tss_struct *tss;
-	unsigned int i, max_long, bytes, bytes_updated;
+	unsigned long *bitmap;
 
 	if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
 		return -EINVAL;
@@ -33,59 +34,55 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 	 * IO bitmap up. ioperm() is much less timing critical than clone(),
 	 * this is why we delay this operation until now:
 	 */
-	if (!t->io_bitmap_ptr) {
-		unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
-
+	bitmap = t->io_bitmap_ptr;
+	if (!bitmap) {
+		bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
 		if (!bitmap)
 			return -ENOMEM;
 
 		memset(bitmap, 0xff, IO_BITMAP_BYTES);
-		t->io_bitmap_ptr = bitmap;
-		set_thread_flag(TIF_IO_BITMAP);
-
-		/*
-		 * Now that we have an IO bitmap, we need our TSS limit to be
-		 * correct.  It's fine if we are preempted after doing this:
-		 * with TIF_IO_BITMAP set, context switches will keep our TSS
-		 * limit correct.
-		 */
-		preempt_disable();
-		refresh_tss_limit();
-		preempt_enable();
 	}
 
 	/*
-	 * do it in the per-thread copy and in the TSS ...
-	 *
-	 * Disable preemption via get_cpu() - we must not switch away
-	 * because the ->io_bitmap_max value must match the bitmap
-	 * contents:
+	 * Update the bitmap and the TSS copy with preemption disabled to
+	 * prevent a race against context switch.
 	 */
-	tss = &per_cpu(cpu_tss_rw, get_cpu());
-
+	preempt_disable();
 	if (turn_on)
-		bitmap_clear(t->io_bitmap_ptr, from, num);
+		bitmap_clear(bitmap, from, num);
 	else
-		bitmap_set(t->io_bitmap_ptr, from, num);
+		bitmap_set(bitmap, from, num);
 
 	/*
 	 * Search for a (possibly new) maximum. This is simple and stupid,
 	 * to keep it obviously correct:
 	 */
 	max_long = 0;
-	for (i = 0; i < IO_BITMAP_LONGS; i++)
-		if (t->io_bitmap_ptr[i] != ~0UL)
+	for (i = 0; i < IO_BITMAP_LONGS; i++) {
+		if (bitmap[i] != ~0UL)
 			max_long = i;
+	}
 
 	bytes = (max_long + 1) * sizeof(unsigned long);
 	bytes_updated = max(bytes, t->io_bitmap_max);
 
+	/* Update the thread data */
 	t->io_bitmap_max = bytes;
+	/*
+	 * Store the bitmap pointer (might be the same if the task already
+	 * head one). Set the TIF flag, just in case this is the first
+	 * invocation.
+	 */
+	t->io_bitmap_ptr = bitmap;
+	set_thread_flag(TIF_IO_BITMAP);
 
-	/* Update the TSS: */
+	/* Update the TSS */
+	tss = this_cpu_ptr(&cpu_tss_rw);
 	memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
+	/* Make sure the TSS limit covers the I/O bitmap. */
+	refresh_tss_limit();
 
-	put_cpu();
+	preempt_enable();
 
 	return 0;
 }

[patch V3 07/20] x86/ioperm: Avoid bitmap allocation if no permissions are set

[Thomas Gleixner]

If ioperm() is invoked the first time and the @turn_on argument is 0, then
there is no point to allocate a bitmap just to clear permissions which are
not set.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V3: Split out from large combo patch
---
 arch/x86/kernel/ioport.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -36,6 +36,9 @@ long ksys_ioperm(unsigned long from, uns
 	 */
 	bitmap = t->io_bitmap_ptr;
 	if (!bitmap) {
+		/* No point to allocate a bitmap just to clear permissions */
+		if (!turn_on)
+			return 0;
 		bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
 		if (!bitmap)
 			return -ENOMEM;

[tip: x86/iopl] x86/ioperm: Avoid bitmap allocation if no permissions are set

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     5487da6bf0775d996352442b89a8defbd671b4ae
Gitweb:        https://git.kernel.org/tip/5487da6bf0775d996352442b89a8defbd671b4ae
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:47 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:02 +01:00

x86/ioperm: Avoid bitmap allocation if no permissions are set

If ioperm() is invoked the first time and the @turn_on argument is 0, then
there is no point to allocate a bitmap just to clear permissions which are
not set.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.404509322@linutronix.de

---
 arch/x86/kernel/ioport.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index ca6aa1e..80fa36b 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -36,6 +36,9 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 	 */
 	bitmap = t->io_bitmap_ptr;
 	if (!bitmap) {
+		/* No point to allocate a bitmap just to clear permissions */
+		if (!turn_on)
+			return 0;
 		bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
 		if (!bitmap)
 			return -ENOMEM;

[patch V3 08/20] x86/io: Speedup schedule out of I/O bitmap user

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

There is no requirement to update the TSS I/O bitmap when a thread using it is
scheduled out and the incoming thread does not use it.

For the permission check based on the TSS I/O bitmap the CPU calculates the memory
location of the I/O bitmap by the address of the TSS and the io_bitmap_base member
of the tss_struct. The easiest way to invalidate the I/O bitmap is to switch the
offset to an address outside of the TSS limit.

If an I/O instruction is issued from user space the TSS limit causes #GP to be
raised in the same was as valid I/O bitmap with all bits set to 1 would do.

This removes the extra work when an I/O bitmap using task is scheduled out
and puts the burden on the rare I/O bitmap users when they are scheduled
in.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---

V3: Moved the changes required to make the first invocation of ioperm()
    correct into a seperate patch. (Incorrectness pointed out by Andy)

---
 arch/x86/include/asm/processor.h |   38 ++++++++++++++++-------
 arch/x86/kernel/cpu/common.c     |    3 +
 arch/x86/kernel/doublefault.c    |    2 -
 arch/x86/kernel/ioport.c         |    2 +
 arch/x86/kernel/process.c        |   63 ++++++++++++++++++++++-----------------
 5 files changed, 67 insertions(+), 41 deletions(-)

--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -330,8 +330,23 @@ struct x86_hw_tss {
 #define IO_BITMAP_BITS			65536
 #define IO_BITMAP_BYTES			(IO_BITMAP_BITS/8)
 #define IO_BITMAP_LONGS			(IO_BITMAP_BYTES/sizeof(long))
-#define IO_BITMAP_OFFSET		(offsetof(struct tss_struct, io_bitmap) - offsetof(struct tss_struct, x86_tss))
-#define INVALID_IO_BITMAP_OFFSET	0x8000
+
+#define IO_BITMAP_OFFSET_VALID				\
+	(offsetof(struct tss_struct, io_bitmap) -	\
+	 offsetof(struct tss_struct, x86_tss))
+
+/*
+ * sizeof(unsigned long) coming from an extra "long" at the end
+ * of the iobitmap.
+ *
+ * -1? seg base+limit should be pointing to the address of the
+ * last valid byte
+ */
+#define __KERNEL_TSS_LIMIT	\
+	(IO_BITMAP_OFFSET_VALID + IO_BITMAP_BYTES + sizeof(unsigned long) - 1)
+
+/* Base offset outside of TSS_LIMIT so unpriviledged IO causes #GP */
+#define IO_BITMAP_OFFSET_INVALID	(__KERNEL_TSS_LIMIT + 1)
 
 struct entry_stack {
 	unsigned long		words[64];
@@ -350,6 +365,15 @@ struct tss_struct {
 	struct x86_hw_tss	x86_tss;
 
 	/*
+	 * Store the dirty size of the last io bitmap offender. The next
+	 * one will have to do the cleanup as the switch out to a non io
+	 * bitmap user will just set x86_tss.io_bitmap_base to a value
+	 * outside of the TSS limit. So for sane tasks there is no need to
+	 * actually touch the io_bitmap at all.
+	 */
+	unsigned int		io_bitmap_prev_max;
+
+	/*
 	 * The extra 1 is there because the CPU will access an
 	 * additional byte beyond the end of the IO permission
 	 * bitmap. The extra byte must be all 1 bits, and must
@@ -360,16 +384,6 @@ struct tss_struct {
 
 DECLARE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw);
 
-/*
- * sizeof(unsigned long) coming from an extra "long" at the end
- * of the iobitmap.
- *
- * -1? seg base+limit should be pointing to the address of the
- * last valid byte
- */
-#define __KERNEL_TSS_LIMIT	\
-	(IO_BITMAP_OFFSET + IO_BITMAP_BYTES + sizeof(unsigned long) - 1)
-
 /* Per CPU interrupt stacks */
 struct irq_stack {
 	char		stack[IRQ_STACK_SIZE];
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1860,7 +1860,8 @@ void cpu_init(void)
 
 	/* Initialize the TSS. */
 	tss_setup_ist(tss);
-	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
+	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
+	tss->io_bitmap_prev_max = 0;
 	memset(tss->io_bitmap, 0xff, sizeof(tss->io_bitmap));
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
--- a/arch/x86/kernel/doublefault.c
+++ b/arch/x86/kernel/doublefault.c
@@ -54,7 +54,7 @@ struct x86_hw_tss doublefault_tss __cach
 	.sp0		= STACK_START,
 	.ss0		= __KERNEL_DS,
 	.ldt		= 0,
-	.io_bitmap_base	= INVALID_IO_BITMAP_OFFSET,
+	.io_bitmap_base	= IO_BITMAP_OFFSET_INVALID,
 
 	.ip		= (unsigned long) doublefault_fn,
 	/* 0x2 bit is always set */
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -84,6 +84,8 @@ long ksys_ioperm(unsigned long from, uns
 	memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
 	/* Store the new end of the zero bits */
 	tss->io_bitmap_prev_max = bytes;
+	/* Make the bitmap base in the TSS valid */
+	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
 	/* Make sure the TSS limit covers the I/O bitmap. */
 	refresh_tss_limit();
 
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -72,18 +72,9 @@
 #ifdef CONFIG_X86_32
 		.ss0 = __KERNEL_DS,
 		.ss1 = __KERNEL_CS,
-		.io_bitmap_base	= INVALID_IO_BITMAP_OFFSET,
 #endif
+		.io_bitmap_base	= IO_BITMAP_OFFSET_INVALID,
 	 },
-#ifdef CONFIG_X86_32
-	 /*
-	  * Note that the .io_bitmap member must be extra-big. This is because
-	  * the CPU will access an additional byte beyond the end of the IO
-	  * permission bitmap. The extra byte must be all 1 bits, and must
-	  * be within the limit.
-	  */
-	.io_bitmap		= { [0 ... IO_BITMAP_LONGS] = ~0 },
-#endif
 };
 EXPORT_PER_CPU_SYMBOL(cpu_tss_rw);
 
@@ -112,18 +103,18 @@ void exit_thread(struct task_struct *tsk
 	struct thread_struct *t = &tsk->thread;
 	unsigned long *bp = t->io_bitmap_ptr;
 	struct fpu *fpu = &t->fpu;
+	struct tss_struct *tss;
 
 	if (bp) {
-		struct tss_struct *tss = &per_cpu(cpu_tss_rw, get_cpu());
+		preempt_disable();
+		tss = this_cpu_ptr(&cpu_tss_rw);
 
 		t->io_bitmap_ptr = NULL;
-		clear_thread_flag(TIF_IO_BITMAP);
-		/*
-		 * Careful, clear this in the TSS too:
-		 */
-		memset(tss->io_bitmap, 0xff, t->io_bitmap_max);
 		t->io_bitmap_max = 0;
-		put_cpu();
+		clear_thread_flag(TIF_IO_BITMAP);
+		/* Invalidate the io bitmap base in the TSS */
+		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
+		preempt_enable();
 		kfree(bp);
 	}
 
@@ -363,29 +354,47 @@ void arch_setup_new_exec(void)
 	}
 }
 
-static inline void switch_to_bitmap(struct thread_struct *prev,
-				    struct thread_struct *next,
+static inline void switch_to_bitmap(struct thread_struct *next,
 				    unsigned long tifp, unsigned long tifn)
 {
 	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
 
 	if (tifn & _TIF_IO_BITMAP) {
 		/*
-		 * Copy the relevant range of the IO bitmap.
-		 * Normally this is 128 bytes or less:
+		 * Copy at least the size of the incoming tasks bitmap
+		 * which covers the last permitted I/O port.
+		 *
+		 * If the previous task which used an io bitmap had more
+		 * bits permitted, then the copy needs to cover those as
+		 * well so they get turned off.
 		 */
 		memcpy(tss->io_bitmap, next->io_bitmap_ptr,
-		       max(prev->io_bitmap_max, next->io_bitmap_max));
+		       max(tss->io_bitmap_prev_max, next->io_bitmap_max));
+
+		/* Store the new max and set io_bitmap_base valid */
+		tss->io_bitmap_prev_max = next->io_bitmap_max;
+		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
+
 		/*
-		 * Make sure that the TSS limit is correct for the CPU
-		 * to notice the IO bitmap.
+		 * Make sure that the TSS limit is covering the io bitmap.
+		 * It might have been cut down by a VMEXIT to 0x67 which
+		 * would cause a subsequent I/O access from user space to
+		 * trigger a #GP because tbe bitmap is outside the TSS
+		 * limit.
 		 */
 		refresh_tss_limit();
 	} else if (tifp & _TIF_IO_BITMAP) {
 		/*
-		 * Clear any possible leftover bits:
+		 * Do not touch the bitmap. Let the next bitmap using task
+		 * deal with the mess. Just make the io_bitmap_base invalid
+		 * by moving it outside the TSS limit so any subsequent I/O
+		 * access from user space will trigger a #GP.
+		 *
+		 * This is correct even when VMEXIT rewrites the TSS limit
+		 * to 0x67 as the only requirement is that the base points
+		 * outside the limit.
 		 */
-		memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
+		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
 	}
 }
 
@@ -599,7 +608,7 @@ void __switch_to_xtra(struct task_struct
 
 	tifn = READ_ONCE(task_thread_info(next_p)->flags);
 	tifp = READ_ONCE(task_thread_info(prev_p)->flags);
-	switch_to_bitmap(prev, next, tifp, tifn);
+	switch_to_bitmap(next, tifp, tifn);
 
 	propagate_user_return_notify(prev_p, next_p);
 

[tip: x86/iopl] x86/io: Speedup schedule out of I/O bitmap user

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     40ba6822b4b396fa3a1490dd63f8f18ab34ad5df
Gitweb:        https://git.kernel.org/tip/40ba6822b4b396fa3a1490dd63f8f18ab34ad5df
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:48 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:02 +01:00

x86/io: Speedup schedule out of I/O bitmap user

There is no requirement to update the TSS I/O bitmap when a thread using it is
scheduled out and the incoming thread does not use it.

For the permission check based on the TSS I/O bitmap the CPU calculates the memory
location of the I/O bitmap by the address of the TSS and the io_bitmap_base member
of the tss_struct. The easiest way to invalidate the I/O bitmap is to switch the
offset to an address outside of the TSS limit.

If an I/O instruction is issued from user space the TSS limit causes #GP to be
raised in the same was as valid I/O bitmap with all bits set to 1 would do.

This removes the extra work when an I/O bitmap using task is scheduled out
and puts the burden on the rare I/O bitmap users when they are scheduled
in.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.493587550@linutronix.de

---
 arch/x86/include/asm/processor.h | 38 +++++++++++++------
 arch/x86/kernel/cpu/common.c     |  3 +-
 arch/x86/kernel/doublefault.c    |  2 +-
 arch/x86/kernel/ioport.c         |  4 ++-
 arch/x86/kernel/process.c        | 63 +++++++++++++++++--------------
 5 files changed, 69 insertions(+), 41 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 6e0a3b4..6d0059c 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -330,8 +330,23 @@ struct x86_hw_tss {
 #define IO_BITMAP_BITS			65536
 #define IO_BITMAP_BYTES			(IO_BITMAP_BITS/8)
 #define IO_BITMAP_LONGS			(IO_BITMAP_BYTES/sizeof(long))
-#define IO_BITMAP_OFFSET		(offsetof(struct tss_struct, io_bitmap) - offsetof(struct tss_struct, x86_tss))
-#define INVALID_IO_BITMAP_OFFSET	0x8000
+
+#define IO_BITMAP_OFFSET_VALID				\
+	(offsetof(struct tss_struct, io_bitmap) -	\
+	 offsetof(struct tss_struct, x86_tss))
+
+/*
+ * sizeof(unsigned long) coming from an extra "long" at the end
+ * of the iobitmap.
+ *
+ * -1? seg base+limit should be pointing to the address of the
+ * last valid byte
+ */
+#define __KERNEL_TSS_LIMIT	\
+	(IO_BITMAP_OFFSET_VALID + IO_BITMAP_BYTES + sizeof(unsigned long) - 1)
+
+/* Base offset outside of TSS_LIMIT so unpriviledged IO causes #GP */
+#define IO_BITMAP_OFFSET_INVALID	(__KERNEL_TSS_LIMIT + 1)
 
 struct entry_stack {
 	unsigned long		words[64];
@@ -350,6 +365,15 @@ struct tss_struct {
 	struct x86_hw_tss	x86_tss;
 
 	/*
+	 * Store the dirty size of the last io bitmap offender. The next
+	 * one will have to do the cleanup as the switch out to a non io
+	 * bitmap user will just set x86_tss.io_bitmap_base to a value
+	 * outside of the TSS limit. So for sane tasks there is no need to
+	 * actually touch the io_bitmap at all.
+	 */
+	unsigned int		io_bitmap_prev_max;
+
+	/*
 	 * The extra 1 is there because the CPU will access an
 	 * additional byte beyond the end of the IO permission
 	 * bitmap. The extra byte must be all 1 bits, and must
@@ -360,16 +384,6 @@ struct tss_struct {
 
 DECLARE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw);
 
-/*
- * sizeof(unsigned long) coming from an extra "long" at the end
- * of the iobitmap.
- *
- * -1? seg base+limit should be pointing to the address of the
- * last valid byte
- */
-#define __KERNEL_TSS_LIMIT	\
-	(IO_BITMAP_OFFSET + IO_BITMAP_BYTES + sizeof(unsigned long) - 1)
-
 /* Per CPU interrupt stacks */
 struct irq_stack {
 	char		stack[IRQ_STACK_SIZE];
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index d52ec1a..8c1000a 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1860,7 +1860,8 @@ void cpu_init(void)
 
 	/* Initialize the TSS. */
 	tss_setup_ist(tss);
-	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
+	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
+	tss->io_bitmap_prev_max = 0;
 	memset(tss->io_bitmap, 0xff, sizeof(tss->io_bitmap));
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
diff --git a/arch/x86/kernel/doublefault.c b/arch/x86/kernel/doublefault.c
index 0b8cedb..cedb07d 100644
--- a/arch/x86/kernel/doublefault.c
+++ b/arch/x86/kernel/doublefault.c
@@ -54,7 +54,7 @@ struct x86_hw_tss doublefault_tss __cacheline_aligned = {
 	.sp0		= STACK_START,
 	.ss0		= __KERNEL_DS,
 	.ldt		= 0,
-	.io_bitmap_base	= INVALID_IO_BITMAP_OFFSET,
+	.io_bitmap_base	= IO_BITMAP_OFFSET_INVALID,
 
 	.ip		= (unsigned long) doublefault_fn,
 	/* 0x2 bit is always set */
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 80fa36b..eed218a 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -82,6 +82,10 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 	/* Update the TSS */
 	tss = this_cpu_ptr(&cpu_tss_rw);
 	memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
+	/* Store the new end of the zero bits */
+	tss->io_bitmap_prev_max = bytes;
+	/* Make the bitmap base in the TSS valid */
+	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
 	/* Make sure the TSS limit covers the I/O bitmap. */
 	refresh_tss_limit();
 
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index c09130a..023e7f8 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -72,18 +72,9 @@ __visible DEFINE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw) = {
 #ifdef CONFIG_X86_32
 		.ss0 = __KERNEL_DS,
 		.ss1 = __KERNEL_CS,
-		.io_bitmap_base	= INVALID_IO_BITMAP_OFFSET,
 #endif
+		.io_bitmap_base	= IO_BITMAP_OFFSET_INVALID,
 	 },
-#ifdef CONFIG_X86_32
-	 /*
-	  * Note that the .io_bitmap member must be extra-big. This is because
-	  * the CPU will access an additional byte beyond the end of the IO
-	  * permission bitmap. The extra byte must be all 1 bits, and must
-	  * be within the limit.
-	  */
-	.io_bitmap		= { [0 ... IO_BITMAP_LONGS] = ~0 },
-#endif
 };
 EXPORT_PER_CPU_SYMBOL(cpu_tss_rw);
 
@@ -112,18 +103,18 @@ void exit_thread(struct task_struct *tsk)
 	struct thread_struct *t = &tsk->thread;
 	unsigned long *bp = t->io_bitmap_ptr;
 	struct fpu *fpu = &t->fpu;
+	struct tss_struct *tss;
 
 	if (bp) {
-		struct tss_struct *tss = &per_cpu(cpu_tss_rw, get_cpu());
+		preempt_disable();
+		tss = this_cpu_ptr(&cpu_tss_rw);
 
 		t->io_bitmap_ptr = NULL;
-		clear_thread_flag(TIF_IO_BITMAP);
-		/*
-		 * Careful, clear this in the TSS too:
-		 */
-		memset(tss->io_bitmap, 0xff, t->io_bitmap_max);
 		t->io_bitmap_max = 0;
-		put_cpu();
+		clear_thread_flag(TIF_IO_BITMAP);
+		/* Invalidate the io bitmap base in the TSS */
+		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
+		preempt_enable();
 		kfree(bp);
 	}
 
@@ -363,29 +354,47 @@ void arch_setup_new_exec(void)
 	}
 }
 
-static inline void switch_to_bitmap(struct thread_struct *prev,
-				    struct thread_struct *next,
+static inline void switch_to_bitmap(struct thread_struct *next,
 				    unsigned long tifp, unsigned long tifn)
 {
 	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
 
 	if (tifn & _TIF_IO_BITMAP) {
 		/*
-		 * Copy the relevant range of the IO bitmap.
-		 * Normally this is 128 bytes or less:
+		 * Copy at least the size of the incoming tasks bitmap
+		 * which covers the last permitted I/O port.
+		 *
+		 * If the previous task which used an io bitmap had more
+		 * bits permitted, then the copy needs to cover those as
+		 * well so they get turned off.
 		 */
 		memcpy(tss->io_bitmap, next->io_bitmap_ptr,
-		       max(prev->io_bitmap_max, next->io_bitmap_max));
+		       max(tss->io_bitmap_prev_max, next->io_bitmap_max));
+
+		/* Store the new max and set io_bitmap_base valid */
+		tss->io_bitmap_prev_max = next->io_bitmap_max;
+		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
+
 		/*
-		 * Make sure that the TSS limit is correct for the CPU
-		 * to notice the IO bitmap.
+		 * Make sure that the TSS limit is covering the io bitmap.
+		 * It might have been cut down by a VMEXIT to 0x67 which
+		 * would cause a subsequent I/O access from user space to
+		 * trigger a #GP because tbe bitmap is outside the TSS
+		 * limit.
 		 */
 		refresh_tss_limit();
 	} else if (tifp & _TIF_IO_BITMAP) {
 		/*
-		 * Clear any possible leftover bits:
+		 * Do not touch the bitmap. Let the next bitmap using task
+		 * deal with the mess. Just make the io_bitmap_base invalid
+		 * by moving it outside the TSS limit so any subsequent I/O
+		 * access from user space will trigger a #GP.
+		 *
+		 * This is correct even when VMEXIT rewrites the TSS limit
+		 * to 0x67 as the only requirement is that the base points
+		 * outside the limit.
 		 */
-		memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
+		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
 	}
 }
 
@@ -599,7 +608,7 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p)
 
 	tifn = READ_ONCE(task_thread_info(next_p)->flags);
 	tifp = READ_ONCE(task_thread_info(prev_p)->flags);
-	switch_to_bitmap(prev, next, tifp, tifn);
+	switch_to_bitmap(next, tifp, tifn);
 
 	propagate_user_return_notify(prev_p, next_p);
 

[patch V3 09/20] x86/tss: Move I/O bitmap data into a seperate struct

[Thomas Gleixner]

Move the non hardware portion of I/O bitmap data into a seperate struct for
readability sake.

Originally-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V3: New patch
---
 arch/x86/include/asm/processor.h |   35 +++++++++++++++++++++--------------
 arch/x86/kernel/cpu/common.c     |    4 ++--
 arch/x86/kernel/ioport.c         |    4 ++--
 arch/x86/kernel/process.c        |    6 +++---
 4 files changed, 28 insertions(+), 21 deletions(-)

--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -328,11 +328,11 @@ struct x86_hw_tss {
  * IO-bitmap sizes:
  */
 #define IO_BITMAP_BITS			65536
-#define IO_BITMAP_BYTES			(IO_BITMAP_BITS/8)
-#define IO_BITMAP_LONGS			(IO_BITMAP_BYTES/sizeof(long))
+#define IO_BITMAP_BYTES			(IO_BITMAP_BITS / BITS_PER_BYTE)
+#define IO_BITMAP_LONGS			(IO_BITMAP_BYTES / sizeof(long))
 
-#define IO_BITMAP_OFFSET_VALID				\
-	(offsetof(struct tss_struct, io_bitmap) -	\
+#define IO_BITMAP_OFFSET_VALID					\
+	(offsetof(struct tss_struct, io_bitmap.bitmap) -	\
 	 offsetof(struct tss_struct, x86_tss))
 
 /*
@@ -356,14 +356,10 @@ struct entry_stack_page {
 	struct entry_stack stack;
 } __aligned(PAGE_SIZE);
 
-struct tss_struct {
-	/*
-	 * The fixed hardware portion.  This must not cross a page boundary
-	 * at risk of violating the SDM's advice and potentially triggering
-	 * errata.
-	 */
-	struct x86_hw_tss	x86_tss;
-
+/*
+ * All IO bitmap related data stored in the TSS:
+ */
+struct x86_io_bitmap {
 	/*
 	 * Store the dirty size of the last io bitmap offender. The next
 	 * one will have to do the cleanup as the switch out to a non io
@@ -371,7 +367,7 @@ struct tss_struct {
 	 * outside of the TSS limit. So for sane tasks there is no need to
 	 * actually touch the io_bitmap at all.
 	 */
-	unsigned int		io_bitmap_prev_max;
+	unsigned int		prev_max;
 
 	/*
 	 * The extra 1 is there because the CPU will access an
@@ -379,7 +375,18 @@ struct tss_struct {
 	 * bitmap. The extra byte must be all 1 bits, and must
 	 * be within the limit.
 	 */
-	unsigned long		io_bitmap[IO_BITMAP_LONGS + 1];
+	unsigned long		bitmap[IO_BITMAP_LONGS + 1];
+};
+
+struct tss_struct {
+	/*
+	 * The fixed hardware portion.  This must not cross a page boundary
+	 * at risk of violating the SDM's advice and potentially triggering
+	 * errata.
+	 */
+	struct x86_hw_tss	x86_tss;
+
+	struct x86_io_bitmap	io_bitmap;
 } __aligned(PAGE_SIZE);
 
 DECLARE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw);
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1861,8 +1861,8 @@ void cpu_init(void)
 	/* Initialize the TSS. */
 	tss_setup_ist(tss);
 	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
-	tss->io_bitmap_prev_max = 0;
-	memset(tss->io_bitmap, 0xff, sizeof(tss->io_bitmap));
+	tss->io_bitmap.prev_max = 0;
+	memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
 	load_TR_desc();
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -81,9 +81,9 @@ long ksys_ioperm(unsigned long from, uns
 
 	/* Update the TSS */
 	tss = this_cpu_ptr(&cpu_tss_rw);
-	memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
+	memcpy(tss->io_bitmap.bitmap, t->io_bitmap_ptr, bytes_updated);
 	/* Store the new end of the zero bits */
-	tss->io_bitmap_prev_max = bytes;
+	tss->io_bitmap.prev_max = bytes;
 	/* Make the bitmap base in the TSS valid */
 	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
 	/* Make sure the TSS limit covers the I/O bitmap. */
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -368,11 +368,11 @@ static inline void switch_to_bitmap(stru
 		 * bits permitted, then the copy needs to cover those as
 		 * well so they get turned off.
 		 */
-		memcpy(tss->io_bitmap, next->io_bitmap_ptr,
-		       max(tss->io_bitmap_prev_max, next->io_bitmap_max));
+		memcpy(tss->io_bitmap.bitmap, next->io_bitmap_ptr,
+		       max(tss->io_bitmap.prev_max, next->io_bitmap_max));
 
 		/* Store the new max and set io_bitmap_base valid */
-		tss->io_bitmap_prev_max = next->io_bitmap_max;
+		tss->io_bitmap.prev_max = next->io_bitmap_max;
 		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
 
 		/*

[tip: x86/iopl] x86/tss: Move I/O bitmap data into a seperate struct

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     98336a94ec192ef45ba66e2c86dd3d7a3ef520a1
Gitweb:        https://git.kernel.org/tip/98336a94ec192ef45ba66e2c86dd3d7a3ef520a1
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:49 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:03 +01:00

x86/tss: Move I/O bitmap data into a seperate struct

Move the non hardware portion of I/O bitmap data into a seperate struct for
readability sake.

Originally-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.591976506@linutronix.de

---
 arch/x86/include/asm/processor.h | 35 ++++++++++++++++++-------------
 arch/x86/kernel/cpu/common.c     |  4 ++--
 arch/x86/kernel/ioport.c         |  4 ++--
 arch/x86/kernel/process.c        |  6 ++---
 4 files changed, 28 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 6d0059c..cd7cd7d 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -328,11 +328,11 @@ struct x86_hw_tss {
  * IO-bitmap sizes:
  */
 #define IO_BITMAP_BITS			65536
-#define IO_BITMAP_BYTES			(IO_BITMAP_BITS/8)
-#define IO_BITMAP_LONGS			(IO_BITMAP_BYTES/sizeof(long))
+#define IO_BITMAP_BYTES			(IO_BITMAP_BITS / BITS_PER_BYTE)
+#define IO_BITMAP_LONGS			(IO_BITMAP_BYTES / sizeof(long))
 
-#define IO_BITMAP_OFFSET_VALID				\
-	(offsetof(struct tss_struct, io_bitmap) -	\
+#define IO_BITMAP_OFFSET_VALID					\
+	(offsetof(struct tss_struct, io_bitmap.bitmap) -	\
 	 offsetof(struct tss_struct, x86_tss))
 
 /*
@@ -356,14 +356,10 @@ struct entry_stack_page {
 	struct entry_stack stack;
 } __aligned(PAGE_SIZE);
 
-struct tss_struct {
-	/*
-	 * The fixed hardware portion.  This must not cross a page boundary
-	 * at risk of violating the SDM's advice and potentially triggering
-	 * errata.
-	 */
-	struct x86_hw_tss	x86_tss;
-
+/*
+ * All IO bitmap related data stored in the TSS:
+ */
+struct x86_io_bitmap {
 	/*
 	 * Store the dirty size of the last io bitmap offender. The next
 	 * one will have to do the cleanup as the switch out to a non io
@@ -371,7 +367,7 @@ struct tss_struct {
 	 * outside of the TSS limit. So for sane tasks there is no need to
 	 * actually touch the io_bitmap at all.
 	 */
-	unsigned int		io_bitmap_prev_max;
+	unsigned int		prev_max;
 
 	/*
 	 * The extra 1 is there because the CPU will access an
@@ -379,7 +375,18 @@ struct tss_struct {
 	 * bitmap. The extra byte must be all 1 bits, and must
 	 * be within the limit.
 	 */
-	unsigned long		io_bitmap[IO_BITMAP_LONGS + 1];
+	unsigned long		bitmap[IO_BITMAP_LONGS + 1];
+};
+
+struct tss_struct {
+	/*
+	 * The fixed hardware portion.  This must not cross a page boundary
+	 * at risk of violating the SDM's advice and potentially triggering
+	 * errata.
+	 */
+	struct x86_hw_tss	x86_tss;
+
+	struct x86_io_bitmap	io_bitmap;
 } __aligned(PAGE_SIZE);
 
 DECLARE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw);
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 8c1000a..3aee167 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1861,8 +1861,8 @@ void cpu_init(void)
 	/* Initialize the TSS. */
 	tss_setup_ist(tss);
 	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
-	tss->io_bitmap_prev_max = 0;
-	memset(tss->io_bitmap, 0xff, sizeof(tss->io_bitmap));
+	tss->io_bitmap.prev_max = 0;
+	memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
 	load_TR_desc();
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index eed218a..80d99bb 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -81,9 +81,9 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 
 	/* Update the TSS */
 	tss = this_cpu_ptr(&cpu_tss_rw);
-	memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
+	memcpy(tss->io_bitmap.bitmap, t->io_bitmap_ptr, bytes_updated);
 	/* Store the new end of the zero bits */
-	tss->io_bitmap_prev_max = bytes;
+	tss->io_bitmap.prev_max = bytes;
 	/* Make the bitmap base in the TSS valid */
 	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
 	/* Make sure the TSS limit covers the I/O bitmap. */
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 023e7f8..3e2f1aa 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -368,11 +368,11 @@ static inline void switch_to_bitmap(struct thread_struct *next,
 		 * bits permitted, then the copy needs to cover those as
 		 * well so they get turned off.
 		 */
-		memcpy(tss->io_bitmap, next->io_bitmap_ptr,
-		       max(tss->io_bitmap_prev_max, next->io_bitmap_max));
+		memcpy(tss->io_bitmap.bitmap, next->io_bitmap_ptr,
+		       max(tss->io_bitmap.prev_max, next->io_bitmap_max));
 
 		/* Store the new max and set io_bitmap_base valid */
-		tss->io_bitmap_prev_max = next->io_bitmap_max;
+		tss->io_bitmap.prev_max = next->io_bitmap_max;
 		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
 
 		/*

[patch V3 10/20] x86/ioperm: Move iobitmap data into a struct

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

No point in having all the data in thread_struct, especially as upcoming
changes add more.

Make the bitmap in the new struct accessible as array of longs and as array
of characters via a union, so both the bitmap functions and the update
logic can avoid type casts.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
V2: New patch
---
 arch/x86/include/asm/io_bitmap.h |   13 +++++++++++++
 arch/x86/include/asm/processor.h |    6 ++----
 arch/x86/kernel/ioport.c         |   27 ++++++++++++++-------------
 arch/x86/kernel/process.c        |   38 ++++++++++++++++++++------------------
 arch/x86/kernel/ptrace.c         |   12 ++++++++----
 5 files changed, 57 insertions(+), 39 deletions(-)

--- /dev/null
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_IOBITMAP_H
+#define _ASM_X86_IOBITMAP_H
+
+#include <asm/processor.h>
+
+struct io_bitmap {
+	/* The maximum number of bytes to copy so all zero bits are covered */
+	unsigned int	max;
+	unsigned long	bitmap[IO_BITMAP_LONGS];
+};
+
+#endif
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -7,6 +7,7 @@
 /* Forward declaration, a strange C thing */
 struct task_struct;
 struct mm_struct;
+struct io_bitmap;
 struct vm86;
 
 #include <asm/math_emu.h>
@@ -501,10 +502,8 @@ struct thread_struct {
 	struct vm86		*vm86;
 #endif
 	/* IO permissions: */
-	unsigned long		*io_bitmap_ptr;
+	struct io_bitmap	*io_bitmap;
 	unsigned long		iopl;
-	/* Max allowed port in the bitmap, in bytes: */
-	unsigned		io_bitmap_max;
 
 	mm_segment_t		addr_limit;
 
@@ -862,7 +861,6 @@ static inline void spin_lock_prefetch(co
 #define INIT_THREAD  {							  \
 	.sp0			= TOP_OF_INIT_STACK,			  \
 	.sysenter_cs		= __KERNEL_CS,				  \
-	.io_bitmap_ptr		= NULL,					  \
 	.addr_limit		= KERNEL_DS,				  \
 }
 
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -11,6 +11,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 
+#include <asm/io_bitmap.h>
 #include <asm/desc.h>
 
 /*
@@ -21,7 +22,7 @@ long ksys_ioperm(unsigned long from, uns
 	unsigned int i, max_long, bytes, bytes_updated;
 	struct thread_struct *t = &current->thread;
 	struct tss_struct *tss;
-	unsigned long *bitmap;
+	struct io_bitmap *iobm;
 
 	if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
 		return -EINVAL;
@@ -34,16 +35,16 @@ long ksys_ioperm(unsigned long from, uns
 	 * IO bitmap up. ioperm() is much less timing critical than clone(),
 	 * this is why we delay this operation until now:
 	 */
-	bitmap = t->io_bitmap_ptr;
-	if (!bitmap) {
+	iobm = t->io_bitmap;
+	if (!iobm) {
 		/* No point to allocate a bitmap just to clear permissions */
 		if (!turn_on)
 			return 0;
-		bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
-		if (!bitmap)
+		iobm = kmalloc(sizeof(*iobm), GFP_KERNEL);
+		if (!iobm)
 			return -ENOMEM;
 
-		memset(bitmap, 0xff, IO_BITMAP_BYTES);
+		memset(iobm->bitmap, 0xff, sizeof(iobm->bitmap));
 	}
 
 	/*
@@ -52,9 +53,9 @@ long ksys_ioperm(unsigned long from, uns
 	 */
 	preempt_disable();
 	if (turn_on)
-		bitmap_clear(bitmap, from, num);
+		bitmap_clear(iobm->bitmap, from, num);
 	else
-		bitmap_set(bitmap, from, num);
+		bitmap_set(iobm->bitmap, from, num);
 
 	/*
 	 * Search for a (possibly new) maximum. This is simple and stupid,
@@ -62,26 +63,26 @@ long ksys_ioperm(unsigned long from, uns
 	 */
 	max_long = 0;
 	for (i = 0; i < IO_BITMAP_LONGS; i++) {
-		if (bitmap[i] != ~0UL)
+		if (iobm->bitmap[i] != ~0UL)
 			max_long = i;
 	}
 
 	bytes = (max_long + 1) * sizeof(unsigned long);
-	bytes_updated = max(bytes, t->io_bitmap_max);
+	bytes_updated = max(bytes, t->io_bitmap->max);
 
 	/* Update the thread data */
-	t->io_bitmap_max = bytes;
+	iobm->max = bytes;
 	/*
 	 * Store the bitmap pointer (might be the same if the task already
 	 * head one). Set the TIF flag, just in case this is the first
 	 * invocation.
 	 */
-	t->io_bitmap_ptr = bitmap;
+	t->io_bitmap = iobm;
 	set_thread_flag(TIF_IO_BITMAP);
 
 	/* Update the TSS */
 	tss = this_cpu_ptr(&cpu_tss_rw);
-	memcpy(tss->io_bitmap.bitmap, t->io_bitmap_ptr, bytes_updated);
+	memcpy(tss->io_bitmap.bitmap, iobm->bitmap, bytes_updated);
 	/* Store the new end of the zero bits */
 	tss->io_bitmap.prev_max = bytes;
 	/* Make the bitmap base in the TSS valid */
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -41,6 +41,7 @@
 #include <asm/desc.h>
 #include <asm/prctl.h>
 #include <asm/spec-ctrl.h>
+#include <asm/io_bitmap.h>
 #include <asm/proto.h>
 
 #include "process.h"
@@ -101,21 +102,20 @@ int arch_dup_task_struct(struct task_str
 void exit_thread(struct task_struct *tsk)
 {
 	struct thread_struct *t = &tsk->thread;
-	unsigned long *bp = t->io_bitmap_ptr;
+	struct io_bitmap *iobm = t->io_bitmap;
 	struct fpu *fpu = &t->fpu;
 	struct tss_struct *tss;
 
-	if (bp) {
+	if (iobm) {
 		preempt_disable();
 		tss = this_cpu_ptr(&cpu_tss_rw);
 
-		t->io_bitmap_ptr = NULL;
-		t->io_bitmap_max = 0;
+		t->io_bitmap = NULL;
 		clear_thread_flag(TIF_IO_BITMAP);
 		/* Invalidate the io bitmap base in the TSS */
 		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
 		preempt_enable();
-		kfree(bp);
+		kfree(iobm);
 	}
 
 	free_vm86(t);
@@ -135,25 +135,25 @@ static int set_new_tls(struct task_struc
 
 static inline int copy_io_bitmap(struct task_struct *tsk)
 {
+	struct io_bitmap *iobm = current->thread.io_bitmap;
+
 	if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP)))
 		return 0;
 
-	tsk->thread.io_bitmap_ptr = kmemdup(current->thread.io_bitmap_ptr,
-					    IO_BITMAP_BYTES, GFP_KERNEL);
-	if (!tsk->thread.io_bitmap_ptr) {
-		tsk->thread.io_bitmap_max = 0;
+	tsk->thread.io_bitmap = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL);
+
+	if (!tsk->thread.io_bitmap)
 		return -ENOMEM;
-	}
+
 	set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
 	return 0;
 }
 
 static inline void free_io_bitmap(struct task_struct *tsk)
 {
-	if (tsk->thread.io_bitmap_ptr) {
-		kfree(tsk->thread.io_bitmap_ptr);
-		tsk->thread.io_bitmap_ptr = NULL;
-		tsk->thread.io_bitmap_max = 0;
+	if (tsk->thread.io_bitmap) {
+		kfree(tsk->thread.io_bitmap);
+		tsk->thread.io_bitmap = NULL;
 	}
 }
 
@@ -172,7 +172,7 @@ int copy_thread_tls(unsigned long clone_
 	frame->bp = 0;
 	frame->ret_addr = (unsigned long) ret_from_fork;
 	p->thread.sp = (unsigned long) fork_frame;
-	p->thread.io_bitmap_ptr = NULL;
+	p->thread.io_bitmap = NULL;
 	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 
 #ifdef CONFIG_X86_64
@@ -360,6 +360,8 @@ static inline void switch_to_bitmap(stru
 	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
 
 	if (tifn & _TIF_IO_BITMAP) {
+		struct io_bitmap *iobm = next->io_bitmap;
+
 		/*
 		 * Copy at least the size of the incoming tasks bitmap
 		 * which covers the last permitted I/O port.
@@ -368,11 +370,11 @@ static inline void switch_to_bitmap(stru
 		 * bits permitted, then the copy needs to cover those as
 		 * well so they get turned off.
 		 */
-		memcpy(tss->io_bitmap.bitmap, next->io_bitmap_ptr,
-		       max(tss->io_bitmap.prev_max, next->io_bitmap_max));
+		memcpy(tss->io_bitmap.bitmap, next->io_bitmap->bitmap,
+		       max(tss->io_bitmap.prev_max, next->io_bitmap->max));
 
 		/* Store the new max and set io_bitmap_base valid */
-		tss->io_bitmap.prev_max = next->io_bitmap_max;
+		tss->io_bitmap.prev_max = next->io_bitmap->max;
 		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
 
 		/*
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -42,6 +42,7 @@
 #include <asm/traps.h>
 #include <asm/syscall.h>
 #include <asm/fsgsbase.h>
+#include <asm/io_bitmap.h>
 
 #include "tls.h"
 
@@ -697,7 +698,9 @@ static int ptrace_set_debugreg(struct ta
 static int ioperm_active(struct task_struct *target,
 			 const struct user_regset *regset)
 {
-	return DIV_ROUND_UP(target->thread.io_bitmap_max, regset->size);
+	struct io_bitmap *iobm = target->thread.io_bitmap;
+
+	return iobm ? DIV_ROUND_UP(iobm->max, regset->size) : 0;
 }
 
 static int ioperm_get(struct task_struct *target,
@@ -705,12 +708,13 @@ static int ioperm_get(struct task_struct
 		      unsigned int pos, unsigned int count,
 		      void *kbuf, void __user *ubuf)
 {
-	if (!target->thread.io_bitmap_ptr)
+	struct io_bitmap *iobm = target->thread.io_bitmap;
+
+	if (!iobm)
 		return -ENXIO;
 
 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
-				   target->thread.io_bitmap_ptr,
-				   0, IO_BITMAP_BYTES);
+				   iobm->bitmap, 0, IO_BITMAP_BYTES);
 }
 
 /*

[tip: x86/iopl] x86/ioperm: Move iobitmap data into a struct

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     a975eef7788ec94ee548a4f182592b425759b7db
Gitweb:        https://git.kernel.org/tip/a975eef7788ec94ee548a4f182592b425759b7db
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:50 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:03 +01:00

x86/ioperm: Move iobitmap data into a struct

No point in having all the data in thread_struct, especially as upcoming
changes add more.

Make the bitmap in the new struct accessible as array of longs and as array
of characters via a union, so both the bitmap functions and the update
logic can avoid type casts.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.683535229@linutronix.de


---
 arch/x86/include/asm/io_bitmap.h | 13 +++++++++++-
 arch/x86/include/asm/processor.h |  6 +----
 arch/x86/kernel/ioport.c         | 27 +++++++++++-----------
 arch/x86/kernel/process.c        | 38 ++++++++++++++++---------------
 arch/x86/kernel/ptrace.c         | 12 ++++++----
 5 files changed, 57 insertions(+), 39 deletions(-)
 create mode 100644 arch/x86/include/asm/io_bitmap.h

diff --git a/arch/x86/include/asm/io_bitmap.h b/arch/x86/include/asm/io_bitmap.h
new file mode 100644
index 0000000..1a12b9f
--- /dev/null
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_IOBITMAP_H
+#define _ASM_X86_IOBITMAP_H
+
+#include <asm/processor.h>
+
+struct io_bitmap {
+	/* The maximum number of bytes to copy so all zero bits are covered */
+	unsigned int	max;
+	unsigned long	bitmap[IO_BITMAP_LONGS];
+};
+
+#endif
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index cd7cd7d..c949e0e 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -7,6 +7,7 @@
 /* Forward declaration, a strange C thing */
 struct task_struct;
 struct mm_struct;
+struct io_bitmap;
 struct vm86;
 
 #include <asm/math_emu.h>
@@ -501,10 +502,8 @@ struct thread_struct {
 	struct vm86		*vm86;
 #endif
 	/* IO permissions: */
-	unsigned long		*io_bitmap_ptr;
+	struct io_bitmap	*io_bitmap;
 	unsigned long		iopl;
-	/* Max allowed port in the bitmap, in bytes: */
-	unsigned		io_bitmap_max;
 
 	mm_segment_t		addr_limit;
 
@@ -862,7 +861,6 @@ static inline void spin_lock_prefetch(const void *x)
 #define INIT_THREAD  {							  \
 	.sp0			= TOP_OF_INIT_STACK,			  \
 	.sysenter_cs		= __KERNEL_CS,				  \
-	.io_bitmap_ptr		= NULL,					  \
 	.addr_limit		= KERNEL_DS,				  \
 }
 
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 80d99bb..05f77f3 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -11,6 +11,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 
+#include <asm/io_bitmap.h>
 #include <asm/desc.h>
 
 /*
@@ -21,7 +22,7 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 	unsigned int i, max_long, bytes, bytes_updated;
 	struct thread_struct *t = &current->thread;
 	struct tss_struct *tss;
-	unsigned long *bitmap;
+	struct io_bitmap *iobm;
 
 	if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
 		return -EINVAL;
@@ -34,16 +35,16 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 	 * IO bitmap up. ioperm() is much less timing critical than clone(),
 	 * this is why we delay this operation until now:
 	 */
-	bitmap = t->io_bitmap_ptr;
-	if (!bitmap) {
+	iobm = t->io_bitmap;
+	if (!iobm) {
 		/* No point to allocate a bitmap just to clear permissions */
 		if (!turn_on)
 			return 0;
-		bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
-		if (!bitmap)
+		iobm = kmalloc(sizeof(*iobm), GFP_KERNEL);
+		if (!iobm)
 			return -ENOMEM;
 
-		memset(bitmap, 0xff, IO_BITMAP_BYTES);
+		memset(iobm->bitmap, 0xff, sizeof(iobm->bitmap));
 	}
 
 	/*
@@ -52,9 +53,9 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 	 */
 	preempt_disable();
 	if (turn_on)
-		bitmap_clear(bitmap, from, num);
+		bitmap_clear(iobm->bitmap, from, num);
 	else
-		bitmap_set(bitmap, from, num);
+		bitmap_set(iobm->bitmap, from, num);
 
 	/*
 	 * Search for a (possibly new) maximum. This is simple and stupid,
@@ -62,26 +63,26 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 	 */
 	max_long = 0;
 	for (i = 0; i < IO_BITMAP_LONGS; i++) {
-		if (bitmap[i] != ~0UL)
+		if (iobm->bitmap[i] != ~0UL)
 			max_long = i;
 	}
 
 	bytes = (max_long + 1) * sizeof(unsigned long);
-	bytes_updated = max(bytes, t->io_bitmap_max);
+	bytes_updated = max(bytes, t->io_bitmap->max);
 
 	/* Update the thread data */
-	t->io_bitmap_max = bytes;
+	iobm->max = bytes;
 	/*
 	 * Store the bitmap pointer (might be the same if the task already
 	 * head one). Set the TIF flag, just in case this is the first
 	 * invocation.
 	 */
-	t->io_bitmap_ptr = bitmap;
+	t->io_bitmap = iobm;
 	set_thread_flag(TIF_IO_BITMAP);
 
 	/* Update the TSS */
 	tss = this_cpu_ptr(&cpu_tss_rw);
-	memcpy(tss->io_bitmap.bitmap, t->io_bitmap_ptr, bytes_updated);
+	memcpy(tss->io_bitmap.bitmap, iobm->bitmap, bytes_updated);
 	/* Store the new end of the zero bits */
 	tss->io_bitmap.prev_max = bytes;
 	/* Make the bitmap base in the TSS valid */
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 3e2f1aa..39c495d 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -41,6 +41,7 @@
 #include <asm/desc.h>
 #include <asm/prctl.h>
 #include <asm/spec-ctrl.h>
+#include <asm/io_bitmap.h>
 #include <asm/proto.h>
 
 #include "process.h"
@@ -101,21 +102,20 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 void exit_thread(struct task_struct *tsk)
 {
 	struct thread_struct *t = &tsk->thread;
-	unsigned long *bp = t->io_bitmap_ptr;
+	struct io_bitmap *iobm = t->io_bitmap;
 	struct fpu *fpu = &t->fpu;
 	struct tss_struct *tss;
 
-	if (bp) {
+	if (iobm) {
 		preempt_disable();
 		tss = this_cpu_ptr(&cpu_tss_rw);
 
-		t->io_bitmap_ptr = NULL;
-		t->io_bitmap_max = 0;
+		t->io_bitmap = NULL;
 		clear_thread_flag(TIF_IO_BITMAP);
 		/* Invalidate the io bitmap base in the TSS */
 		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
 		preempt_enable();
-		kfree(bp);
+		kfree(iobm);
 	}
 
 	free_vm86(t);
@@ -135,25 +135,25 @@ static int set_new_tls(struct task_struct *p, unsigned long tls)
 
 static inline int copy_io_bitmap(struct task_struct *tsk)
 {
+	struct io_bitmap *iobm = current->thread.io_bitmap;
+
 	if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP)))
 		return 0;
 
-	tsk->thread.io_bitmap_ptr = kmemdup(current->thread.io_bitmap_ptr,
-					    IO_BITMAP_BYTES, GFP_KERNEL);
-	if (!tsk->thread.io_bitmap_ptr) {
-		tsk->thread.io_bitmap_max = 0;
+	tsk->thread.io_bitmap = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL);
+
+	if (!tsk->thread.io_bitmap)
 		return -ENOMEM;
-	}
+
 	set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
 	return 0;
 }
 
 static inline void free_io_bitmap(struct task_struct *tsk)
 {
-	if (tsk->thread.io_bitmap_ptr) {
-		kfree(tsk->thread.io_bitmap_ptr);
-		tsk->thread.io_bitmap_ptr = NULL;
-		tsk->thread.io_bitmap_max = 0;
+	if (tsk->thread.io_bitmap) {
+		kfree(tsk->thread.io_bitmap);
+		tsk->thread.io_bitmap = NULL;
 	}
 }
 
@@ -172,7 +172,7 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 	frame->bp = 0;
 	frame->ret_addr = (unsigned long) ret_from_fork;
 	p->thread.sp = (unsigned long) fork_frame;
-	p->thread.io_bitmap_ptr = NULL;
+	p->thread.io_bitmap = NULL;
 	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 
 #ifdef CONFIG_X86_64
@@ -360,6 +360,8 @@ static inline void switch_to_bitmap(struct thread_struct *next,
 	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
 
 	if (tifn & _TIF_IO_BITMAP) {
+		struct io_bitmap *iobm = next->io_bitmap;
+
 		/*
 		 * Copy at least the size of the incoming tasks bitmap
 		 * which covers the last permitted I/O port.
@@ -368,11 +370,11 @@ static inline void switch_to_bitmap(struct thread_struct *next,
 		 * bits permitted, then the copy needs to cover those as
 		 * well so they get turned off.
 		 */
-		memcpy(tss->io_bitmap.bitmap, next->io_bitmap_ptr,
-		       max(tss->io_bitmap.prev_max, next->io_bitmap_max));
+		memcpy(tss->io_bitmap.bitmap, next->io_bitmap->bitmap,
+		       max(tss->io_bitmap.prev_max, next->io_bitmap->max));
 
 		/* Store the new max and set io_bitmap_base valid */
-		tss->io_bitmap.prev_max = next->io_bitmap_max;
+		tss->io_bitmap.prev_max = next->io_bitmap->max;
 		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
 
 		/*
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 7c52674..066e5b0 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -42,6 +42,7 @@
 #include <asm/traps.h>
 #include <asm/syscall.h>
 #include <asm/fsgsbase.h>
+#include <asm/io_bitmap.h>
 
 #include "tls.h"
 
@@ -697,7 +698,9 @@ static int ptrace_set_debugreg(struct task_struct *tsk, int n,
 static int ioperm_active(struct task_struct *target,
 			 const struct user_regset *regset)
 {
-	return DIV_ROUND_UP(target->thread.io_bitmap_max, regset->size);
+	struct io_bitmap *iobm = target->thread.io_bitmap;
+
+	return iobm ? DIV_ROUND_UP(iobm->max, regset->size) : 0;
 }
 
 static int ioperm_get(struct task_struct *target,
@@ -705,12 +708,13 @@ static int ioperm_get(struct task_struct *target,
 		      unsigned int pos, unsigned int count,
 		      void *kbuf, void __user *ubuf)
 {
-	if (!target->thread.io_bitmap_ptr)
+	struct io_bitmap *iobm = target->thread.io_bitmap;
+
+	if (!iobm)
 		return -ENXIO;
 
 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
-				   target->thread.io_bitmap_ptr,
-				   0, IO_BITMAP_BYTES);
+				   iobm->bitmap, 0, IO_BITMAP_BYTES);
 }
 
 /*

[patch V3 11/20] x86/ioperm: Add bitmap sequence number

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

Add a globally unique sequence number which is incremented when ioperm() is
changing the I/O bitmap of a task. Store the new sequence number in the
io_bitmap structure and compare it with the sequence number of the I/O
bitmap which was last loaded on a CPU. Only update the bitmap if the
sequence is different.

That should further reduce the overhead of I/O bitmap scheduling when there
are only a few I/O bitmap users on the system.

The 64bit sequence counter is sufficient. A wraparound of the sequence
counter assuming an ioperm() call every nanosecond would require about 584
years of uptime.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
V3: Remove the pointer comparison (Peter, Andy)

V2: New patch
---
 arch/x86/include/asm/io_bitmap.h |    1 +
 arch/x86/include/asm/processor.h |    3 +++
 arch/x86/kernel/cpu/common.c     |    1 +
 arch/x86/kernel/ioport.c         |    5 +++++
 arch/x86/kernel/process.c        |   38 ++++++++++++++++++++++++++++----------
 5 files changed, 38 insertions(+), 10 deletions(-)

--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -5,6 +5,7 @@
 #include <asm/processor.h>
 
 struct io_bitmap {
+	u64		sequence;
 	/* The maximum number of bytes to copy so all zero bits are covered */
 	unsigned int	max;
 	unsigned long	bitmap[IO_BITMAP_LONGS];
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -361,6 +361,9 @@ struct entry_stack_page {
  * All IO bitmap related data stored in the TSS:
  */
 struct x86_io_bitmap {
+	/* The sequence number of the last active bitmap. */
+	u64			prev_sequence;
+
 	/*
 	 * Store the dirty size of the last io bitmap offender. The next
 	 * one will have to do the cleanup as the switch out to a non io
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1862,6 +1862,7 @@ void cpu_init(void)
 	tss_setup_ist(tss);
 	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
 	tss->io_bitmap.prev_max = 0;
+	tss->io_bitmap.prev_sequence = 0;
 	memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -14,6 +14,8 @@
 #include <asm/io_bitmap.h>
 #include <asm/desc.h>
 
+static atomic64_t io_bitmap_sequence;
+
 /*
  * this changes the io permissions bitmap in the current task.
  */
@@ -72,6 +74,9 @@ long ksys_ioperm(unsigned long from, uns
 
 	/* Update the thread data */
 	iobm->max = bytes;
+	/* Update the sequence number to force an update in switch_to() */
+	iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
+
 	/*
 	 * Store the bitmap pointer (might be the same if the task already
 	 * head one). Set the TIF flag, just in case this is the first
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -354,6 +354,28 @@ void arch_setup_new_exec(void)
 	}
 }
 
+static void switch_to_update_io_bitmap(struct tss_struct *tss,
+				       struct io_bitmap *iobm)
+{
+	/*
+	 * Copy at least the byte range of the incoming tasks bitmap which
+	 * covers the permitted I/O ports.
+	 *
+	 * If the previous task which used an I/O bitmap had more bits
+	 * permitted, then the copy needs to cover those as well so they
+	 * get turned off.
+	 */
+	memcpy(tss->io_bitmap.bitmap, iobm->bitmap,
+	       max(tss->io_bitmap.prev_max, iobm->max));
+
+	/*
+	 * Store the new max and the sequence number of this bitmap
+	 * and a pointer to the bitmap itself.
+	 */
+	tss->io_bitmap.prev_max = iobm->max;
+	tss->io_bitmap.prev_sequence = iobm->sequence;
+}
+
 static inline void switch_to_bitmap(struct thread_struct *next,
 				    unsigned long tifp, unsigned long tifn)
 {
@@ -363,18 +385,14 @@ static inline void switch_to_bitmap(stru
 		struct io_bitmap *iobm = next->io_bitmap;
 
 		/*
-		 * Copy at least the size of the incoming tasks bitmap
-		 * which covers the last permitted I/O port.
-		 *
-		 * If the previous task which used an io bitmap had more
-		 * bits permitted, then the copy needs to cover those as
-		 * well so they get turned off.
+		 * Only copy bitmap data when the sequence number
+		 * differs. The update time is accounted to the incoming
+		 * task.
 		 */
-		memcpy(tss->io_bitmap.bitmap, next->io_bitmap->bitmap,
-		       max(tss->io_bitmap.prev_max, next->io_bitmap->max));
+		if (tss->io_bitmap.prev_sequence != iobm->sequence)
+			switch_to_update_io_bitmap(tss, iobm);
 
-		/* Store the new max and set io_bitmap_base valid */
-		tss->io_bitmap.prev_max = next->io_bitmap->max;
+		/* Enable the bitmap */
 		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
 
 		/*

[tip: x86/iopl] x86/ioperm: Add bitmap sequence number

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     209c34d3c2de01a5dfe428b8b79fdb913dd76334
Gitweb:        https://git.kernel.org/tip/209c34d3c2de01a5dfe428b8b79fdb913dd76334
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:51 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:04 +01:00

x86/ioperm: Add bitmap sequence number

Add a globally unique sequence number which is incremented when ioperm() is
changing the I/O bitmap of a task. Store the new sequence number in the
io_bitmap structure and compare it with the sequence number of the I/O
bitmap which was last loaded on a CPU. Only update the bitmap if the
sequence is different.

That should further reduce the overhead of I/O bitmap scheduling when there
are only a few I/O bitmap users on the system.

The 64bit sequence counter is sufficient. A wraparound of the sequence
counter assuming an ioperm() call every nanosecond would require about 584
years of uptime.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.790774205@linutronix.de


---
 arch/x86/include/asm/io_bitmap.h |  1 +-
 arch/x86/include/asm/processor.h |  3 ++-
 arch/x86/kernel/cpu/common.c     |  1 +-
 arch/x86/kernel/ioport.c         |  5 ++++-
 arch/x86/kernel/process.c        | 38 ++++++++++++++++++++++---------
 5 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/io_bitmap.h b/arch/x86/include/asm/io_bitmap.h
index 1a12b9f..d63bd5a 100644
--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -5,6 +5,7 @@
 #include <asm/processor.h>
 
 struct io_bitmap {
+	u64		sequence;
 	/* The maximum number of bytes to copy so all zero bits are covered */
 	unsigned int	max;
 	unsigned long	bitmap[IO_BITMAP_LONGS];
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index c949e0e..40bb0f7 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -361,6 +361,9 @@ struct entry_stack_page {
  * All IO bitmap related data stored in the TSS:
  */
 struct x86_io_bitmap {
+	/* The sequence number of the last active bitmap. */
+	u64			prev_sequence;
+
 	/*
 	 * Store the dirty size of the last io bitmap offender. The next
 	 * one will have to do the cleanup as the switch out to a non io
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 3aee167..79dd544 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1862,6 +1862,7 @@ void cpu_init(void)
 	tss_setup_ist(tss);
 	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
 	tss->io_bitmap.prev_max = 0;
+	tss->io_bitmap.prev_sequence = 0;
 	memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 05f77f3..7c1ab5c 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -14,6 +14,8 @@
 #include <asm/io_bitmap.h>
 #include <asm/desc.h>
 
+static atomic64_t io_bitmap_sequence;
+
 /*
  * this changes the io permissions bitmap in the current task.
  */
@@ -72,6 +74,9 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 
 	/* Update the thread data */
 	iobm->max = bytes;
+	/* Update the sequence number to force an update in switch_to() */
+	iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
+
 	/*
 	 * Store the bitmap pointer (might be the same if the task already
 	 * head one). Set the TIF flag, just in case this is the first
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 39c495d..eec7987 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -354,6 +354,28 @@ void arch_setup_new_exec(void)
 	}
 }
 
+static void switch_to_update_io_bitmap(struct tss_struct *tss,
+				       struct io_bitmap *iobm)
+{
+	/*
+	 * Copy at least the byte range of the incoming tasks bitmap which
+	 * covers the permitted I/O ports.
+	 *
+	 * If the previous task which used an I/O bitmap had more bits
+	 * permitted, then the copy needs to cover those as well so they
+	 * get turned off.
+	 */
+	memcpy(tss->io_bitmap.bitmap, iobm->bitmap,
+	       max(tss->io_bitmap.prev_max, iobm->max));
+
+	/*
+	 * Store the new max and the sequence number of this bitmap
+	 * and a pointer to the bitmap itself.
+	 */
+	tss->io_bitmap.prev_max = iobm->max;
+	tss->io_bitmap.prev_sequence = iobm->sequence;
+}
+
 static inline void switch_to_bitmap(struct thread_struct *next,
 				    unsigned long tifp, unsigned long tifn)
 {
@@ -363,18 +385,14 @@ static inline void switch_to_bitmap(struct thread_struct *next,
 		struct io_bitmap *iobm = next->io_bitmap;
 
 		/*
-		 * Copy at least the size of the incoming tasks bitmap
-		 * which covers the last permitted I/O port.
-		 *
-		 * If the previous task which used an io bitmap had more
-		 * bits permitted, then the copy needs to cover those as
-		 * well so they get turned off.
+		 * Only copy bitmap data when the sequence number
+		 * differs. The update time is accounted to the incoming
+		 * task.
 		 */
-		memcpy(tss->io_bitmap.bitmap, next->io_bitmap->bitmap,
-		       max(tss->io_bitmap.prev_max, next->io_bitmap->max));
+		if (tss->io_bitmap.prev_sequence != iobm->sequence)
+			switch_to_update_io_bitmap(tss, iobm);
 
-		/* Store the new max and set io_bitmap_base valid */
-		tss->io_bitmap.prev_max = next->io_bitmap->max;
+		/* Enable the bitmap */
 		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
 
 		/*

[patch V3 12/20] x86/ioperm: Move TSS bitmap update to exit to user work

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

There is no point to update the TSS bitmap for tasks which use I/O bitmaps
on every context switch. It's enough to update it right before exiting to
user space.

That reduces the context switch bitmap handling to invalidating the io
bitmap base offset in the TSS when the outgoing task has TIF_IO_BITMAP
set. The invaldiation is done on purpose when a task with an IO bitmap
switches out to prevent any possible leakage of an activated IO bitmap.

It also removes the requirement to update the tasks bitmap atomically in
ioperm().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
V3: Updated comment and changelog to clarify the invalidation logic
    Removed _TIF_IO_BITMAP from _TIF_WORK_CTXSW_NEXT as it is only
    required for the outgoing task.

V2: New patch
---
 arch/x86/entry/common.c            |    4 ++
 arch/x86/include/asm/io_bitmap.h   |    2 +
 arch/x86/include/asm/thread_info.h |    9 +++--
 arch/x86/kernel/ioport.c           |   25 ++-------------
 arch/x86/kernel/process.c          |   59 ++++++++++++++++++++++++-------------
 5 files changed, 54 insertions(+), 45 deletions(-)

--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -33,6 +33,7 @@
 #include <asm/cpufeature.h>
 #include <asm/fpu/api.h>
 #include <asm/nospec-branch.h>
+#include <asm/io_bitmap.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/syscalls.h>
@@ -196,6 +197,9 @@ static void exit_to_usermode_loop(struct
 	/* Reload ti->flags; we may have rescheduled above. */
 	cached_flags = READ_ONCE(ti->flags);
 
+	if (unlikely(cached_flags & _TIF_IO_BITMAP))
+		tss_update_io_bitmap();
+
 	fpregs_assert_state_consistent();
 	if (unlikely(cached_flags & _TIF_NEED_FPU_LOAD))
 		switch_fpu_return();
--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -11,4 +11,6 @@ struct io_bitmap {
 	unsigned long	bitmap[IO_BITMAP_LONGS];
 };
 
+void tss_update_io_bitmap(void);
+
 #endif
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -143,8 +143,8 @@ struct thread_info {
 	 _TIF_NOHZ)
 
 /* flags to check in __switch_to() */
-#define _TIF_WORK_CTXSW_BASE						\
-	(_TIF_IO_BITMAP|_TIF_NOCPUID|_TIF_NOTSC|_TIF_BLOCKSTEP|		\
+#define _TIF_WORK_CTXSW_BASE					\
+	(_TIF_NOCPUID | _TIF_NOTSC | _TIF_BLOCKSTEP |		\
 	 _TIF_SSBD | _TIF_SPEC_FORCE_UPDATE)
 
 /*
@@ -156,8 +156,9 @@ struct thread_info {
 # define _TIF_WORK_CTXSW	(_TIF_WORK_CTXSW_BASE)
 #endif
 
-#define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
-#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
+#define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY | \
+				 _TIF_IO_BITMAP)
+#define _TIF_WORK_CTXSW_NEXT	(_TIF_WORK_CTXSW)
 
 #define STACK_WARN		(THREAD_SIZE/8)
 
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -21,9 +21,8 @@ static atomic64_t io_bitmap_sequence;
  */
 long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 {
-	unsigned int i, max_long, bytes, bytes_updated;
 	struct thread_struct *t = &current->thread;
-	struct tss_struct *tss;
+	unsigned int i, max_long;
 	struct io_bitmap *iobm;
 
 	if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
@@ -50,10 +49,9 @@ long ksys_ioperm(unsigned long from, uns
 	}
 
 	/*
-	 * Update the bitmap and the TSS copy with preemption disabled to
-	 * prevent a race against context switch.
+	 * Update the tasks bitmap. The update of the TSS bitmap happens on
+	 * exit to user mode. So this needs no protection.
 	 */
-	preempt_disable();
 	if (turn_on)
 		bitmap_clear(iobm->bitmap, from, num);
 	else
@@ -69,11 +67,8 @@ long ksys_ioperm(unsigned long from, uns
 			max_long = i;
 	}
 
-	bytes = (max_long + 1) * sizeof(unsigned long);
-	bytes_updated = max(bytes, t->io_bitmap->max);
+	iobm->max = (max_long + 1) * sizeof(unsigned long);
 
-	/* Update the thread data */
-	iobm->max = bytes;
 	/* Update the sequence number to force an update in switch_to() */
 	iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
 
@@ -85,18 +80,6 @@ long ksys_ioperm(unsigned long from, uns
 	t->io_bitmap = iobm;
 	set_thread_flag(TIF_IO_BITMAP);
 
-	/* Update the TSS */
-	tss = this_cpu_ptr(&cpu_tss_rw);
-	memcpy(tss->io_bitmap.bitmap, iobm->bitmap, bytes_updated);
-	/* Store the new end of the zero bits */
-	tss->io_bitmap.prev_max = bytes;
-	/* Make the bitmap base in the TSS valid */
-	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
-	/* Make sure the TSS limit covers the I/O bitmap. */
-	refresh_tss_limit();
-
-	preempt_enable();
-
 	return 0;
 }
 
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -354,8 +354,34 @@ void arch_setup_new_exec(void)
 	}
 }
 
-static void switch_to_update_io_bitmap(struct tss_struct *tss,
-				       struct io_bitmap *iobm)
+static inline void tss_invalidate_io_bitmap(struct tss_struct *tss)
+{
+	/*
+	 * Invalidate the I/O bitmap by moving io_bitmap_base outside the
+	 * TSS limit so any subsequent I/O access from user space will
+	 * trigger a #GP.
+	 *
+	 * This is correct even when VMEXIT rewrites the TSS limit
+	 * to 0x67 as the only requirement is that the base points
+	 * outside the limit.
+	 */
+	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
+}
+
+static inline void switch_to_bitmap(unsigned long tifp)
+{
+	/*
+	 * Invalidate I/O bitmap if the previous task used it. This prevents
+	 * any possible leakage of an active I/O bitmap.
+	 *
+	 * If the next task has an I/O bitmap it will handle it on exit to
+	 * user mode.
+	 */
+	if (tifp & _TIF_IO_BITMAP)
+		tss_invalidate_io_bitmap(this_cpu_ptr(&cpu_tss_rw));
+}
+
+static void tss_copy_io_bitmap(struct tss_struct *tss, struct io_bitmap *iobm)
 {
 	/*
 	 * Copy at least the byte range of the incoming tasks bitmap which
@@ -376,13 +402,15 @@ static void switch_to_update_io_bitmap(s
 	tss->io_bitmap.prev_sequence = iobm->sequence;
 }
 
-static inline void switch_to_bitmap(struct thread_struct *next,
-				    unsigned long tifp, unsigned long tifn)
+/**
+ * tss_update_io_bitmap - Update I/O bitmap before exiting to usermode
+ */
+void tss_update_io_bitmap(void)
 {
 	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
 
-	if (tifn & _TIF_IO_BITMAP) {
-		struct io_bitmap *iobm = next->io_bitmap;
+	if (test_thread_flag(TIF_IO_BITMAP)) {
+		struct io_bitmap *iobm = current->thread.io_bitmap;
 
 		/*
 		 * Only copy bitmap data when the sequence number
@@ -390,7 +418,7 @@ static inline void switch_to_bitmap(stru
 		 * task.
 		 */
 		if (tss->io_bitmap.prev_sequence != iobm->sequence)
-			switch_to_update_io_bitmap(tss, iobm);
+			tss_copy_io_bitmap(tss, iobm);
 
 		/* Enable the bitmap */
 		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
@@ -403,18 +431,8 @@ static inline void switch_to_bitmap(stru
 		 * limit.
 		 */
 		refresh_tss_limit();
-	} else if (tifp & _TIF_IO_BITMAP) {
-		/*
-		 * Do not touch the bitmap. Let the next bitmap using task
-		 * deal with the mess. Just make the io_bitmap_base invalid
-		 * by moving it outside the TSS limit so any subsequent I/O
-		 * access from user space will trigger a #GP.
-		 *
-		 * This is correct even when VMEXIT rewrites the TSS limit
-		 * to 0x67 as the only requirement is that the base points
-		 * outside the limit.
-		 */
-		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
+	} else {
+		tss_invalidate_io_bitmap(tss);
 	}
 }
 
@@ -628,7 +646,8 @@ void __switch_to_xtra(struct task_struct
 
 	tifn = READ_ONCE(task_thread_info(next_p)->flags);
 	tifp = READ_ONCE(task_thread_info(prev_p)->flags);
-	switch_to_bitmap(next, tifp, tifn);
+
+	switch_to_bitmap(tifp);
 
 	propagate_user_return_notify(prev_p, next_p);
 

Re: [patch V3 12/20] x86/ioperm: Move TSS bitmap update to exit to user work

[Linus Torvalds]

On Wed, Nov 13, 2019 at 1:02 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> From: Thomas Gleixner <tglx@linutronix.de>
>
> There is no point to update the TSS bitmap for tasks which use I/O bitmaps
> on every context switch. It's enough to update it right before exiting to
> user space.

Hmm.

I wonder if it might make sense to delay it even more: just always
invalidate the bitmap on task switch, and leave it at that.

And then on GP fault, just add trivial logic like

     if (I_have_an_io_bitmap && it_isnt_installed) {
          install_io_bitmap();
          return;
     }

and now you do get that extra GP fault if you actually use IO
accesses, but the normal case has zero overhead.

Even processes that do ioperm may not be *using* it all the time.

               Linus

Re: [patch V3 12/20] x86/ioperm: Move TSS bitmap update to exit to user work

[Linus Torvalds]

On Wed, Nov 13, 2019 at 1:19 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> I wonder if it might make sense to delay it even more: [..]

Btw, don't take that as a suggestion to make further changes. It was
more of an idle observation, and it probably doesn't matter one whit.

              Linus

Re: [patch V3 12/20] x86/ioperm: Move TSS bitmap update to exit to user work

[Thomas Gleixner]

On Wed, 13 Nov 2019, Linus Torvalds wrote:

> On Wed, Nov 13, 2019 at 1:19 PM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > I wonder if it might make sense to delay it even more: [..]
> 
> Btw, don't take that as a suggestion to make further changes. It was
> more of an idle observation, and it probably doesn't matter one whit.

Hehe. I wont, but yes the idea is sneaky enough to be really tempting :)

Thanks,

	tglx

[tip: x86/iopl] x86/ioperm: Move TSS bitmap update to exit to user work

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     8ef04e97f1b49edd583e7b6fe81a3e24a3916786
Gitweb:        https://git.kernel.org/tip/8ef04e97f1b49edd583e7b6fe81a3e24a3916786
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:52 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:04 +01:00

x86/ioperm: Move TSS bitmap update to exit to user work

There is no point to update the TSS bitmap for tasks which use I/O bitmaps
on every context switch. It's enough to update it right before exiting to
user space.

That reduces the context switch bitmap handling to invalidating the io
bitmap base offset in the TSS when the outgoing task has TIF_IO_BITMAP
set. The invaldiation is done on purpose when a task with an IO bitmap
switches out to prevent any possible leakage of an activated IO bitmap.

It also removes the requirement to update the tasks bitmap atomically in
ioperm().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.882617091@linutronix.de


---
 arch/x86/entry/common.c            |  4 ++-
 arch/x86/include/asm/io_bitmap.h   |  2 +-
 arch/x86/include/asm/thread_info.h |  9 ++--
 arch/x86/kernel/ioport.c           | 25 +-----------
 arch/x86/kernel/process.c          | 59 +++++++++++++++++++----------
 5 files changed, 54 insertions(+), 45 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 3f8e226..9747876 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -33,6 +33,7 @@
 #include <asm/cpufeature.h>
 #include <asm/fpu/api.h>
 #include <asm/nospec-branch.h>
+#include <asm/io_bitmap.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/syscalls.h>
@@ -196,6 +197,9 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
 	/* Reload ti->flags; we may have rescheduled above. */
 	cached_flags = READ_ONCE(ti->flags);
 
+	if (unlikely(cached_flags & _TIF_IO_BITMAP))
+		tss_update_io_bitmap();
+
 	fpregs_assert_state_consistent();
 	if (unlikely(cached_flags & _TIF_NEED_FPU_LOAD))
 		switch_fpu_return();
diff --git a/arch/x86/include/asm/io_bitmap.h b/arch/x86/include/asm/io_bitmap.h
index d63bd5a..6d82a37 100644
--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -11,4 +11,6 @@ struct io_bitmap {
 	unsigned long	bitmap[IO_BITMAP_LONGS];
 };
 
+void tss_update_io_bitmap(void);
+
 #endif
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index f945353..0accf44 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -143,8 +143,8 @@ struct thread_info {
 	 _TIF_NOHZ)
 
 /* flags to check in __switch_to() */
-#define _TIF_WORK_CTXSW_BASE						\
-	(_TIF_IO_BITMAP|_TIF_NOCPUID|_TIF_NOTSC|_TIF_BLOCKSTEP|		\
+#define _TIF_WORK_CTXSW_BASE					\
+	(_TIF_NOCPUID | _TIF_NOTSC | _TIF_BLOCKSTEP |		\
 	 _TIF_SSBD | _TIF_SPEC_FORCE_UPDATE)
 
 /*
@@ -156,8 +156,9 @@ struct thread_info {
 # define _TIF_WORK_CTXSW	(_TIF_WORK_CTXSW_BASE)
 #endif
 
-#define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
-#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
+#define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY | \
+				 _TIF_IO_BITMAP)
+#define _TIF_WORK_CTXSW_NEXT	(_TIF_WORK_CTXSW)
 
 #define STACK_WARN		(THREAD_SIZE/8)
 
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 7c1ab5c..198bead 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -21,9 +21,8 @@ static atomic64_t io_bitmap_sequence;
  */
 long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 {
-	unsigned int i, max_long, bytes, bytes_updated;
 	struct thread_struct *t = &current->thread;
-	struct tss_struct *tss;
+	unsigned int i, max_long;
 	struct io_bitmap *iobm;
 
 	if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
@@ -50,10 +49,9 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 	}
 
 	/*
-	 * Update the bitmap and the TSS copy with preemption disabled to
-	 * prevent a race against context switch.
+	 * Update the tasks bitmap. The update of the TSS bitmap happens on
+	 * exit to user mode. So this needs no protection.
 	 */
-	preempt_disable();
 	if (turn_on)
 		bitmap_clear(iobm->bitmap, from, num);
 	else
@@ -69,11 +67,8 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 			max_long = i;
 	}
 
-	bytes = (max_long + 1) * sizeof(unsigned long);
-	bytes_updated = max(bytes, t->io_bitmap->max);
+	iobm->max = (max_long + 1) * sizeof(unsigned long);
 
-	/* Update the thread data */
-	iobm->max = bytes;
 	/* Update the sequence number to force an update in switch_to() */
 	iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
 
@@ -85,18 +80,6 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 	t->io_bitmap = iobm;
 	set_thread_flag(TIF_IO_BITMAP);
 
-	/* Update the TSS */
-	tss = this_cpu_ptr(&cpu_tss_rw);
-	memcpy(tss->io_bitmap.bitmap, iobm->bitmap, bytes_updated);
-	/* Store the new end of the zero bits */
-	tss->io_bitmap.prev_max = bytes;
-	/* Make the bitmap base in the TSS valid */
-	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
-	/* Make sure the TSS limit covers the I/O bitmap. */
-	refresh_tss_limit();
-
-	preempt_enable();
-
 	return 0;
 }
 
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index eec7987..1990011 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -354,8 +354,34 @@ void arch_setup_new_exec(void)
 	}
 }
 
-static void switch_to_update_io_bitmap(struct tss_struct *tss,
-				       struct io_bitmap *iobm)
+static inline void tss_invalidate_io_bitmap(struct tss_struct *tss)
+{
+	/*
+	 * Invalidate the I/O bitmap by moving io_bitmap_base outside the
+	 * TSS limit so any subsequent I/O access from user space will
+	 * trigger a #GP.
+	 *
+	 * This is correct even when VMEXIT rewrites the TSS limit
+	 * to 0x67 as the only requirement is that the base points
+	 * outside the limit.
+	 */
+	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
+}
+
+static inline void switch_to_bitmap(unsigned long tifp)
+{
+	/*
+	 * Invalidate I/O bitmap if the previous task used it. This prevents
+	 * any possible leakage of an active I/O bitmap.
+	 *
+	 * If the next task has an I/O bitmap it will handle it on exit to
+	 * user mode.
+	 */
+	if (tifp & _TIF_IO_BITMAP)
+		tss_invalidate_io_bitmap(this_cpu_ptr(&cpu_tss_rw));
+}
+
+static void tss_copy_io_bitmap(struct tss_struct *tss, struct io_bitmap *iobm)
 {
 	/*
 	 * Copy at least the byte range of the incoming tasks bitmap which
@@ -376,13 +402,15 @@ static void switch_to_update_io_bitmap(struct tss_struct *tss,
 	tss->io_bitmap.prev_sequence = iobm->sequence;
 }
 
-static inline void switch_to_bitmap(struct thread_struct *next,
-				    unsigned long tifp, unsigned long tifn)
+/**
+ * tss_update_io_bitmap - Update I/O bitmap before exiting to usermode
+ */
+void tss_update_io_bitmap(void)
 {
 	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
 
-	if (tifn & _TIF_IO_BITMAP) {
-		struct io_bitmap *iobm = next->io_bitmap;
+	if (test_thread_flag(TIF_IO_BITMAP)) {
+		struct io_bitmap *iobm = current->thread.io_bitmap;
 
 		/*
 		 * Only copy bitmap data when the sequence number
@@ -390,7 +418,7 @@ static inline void switch_to_bitmap(struct thread_struct *next,
 		 * task.
 		 */
 		if (tss->io_bitmap.prev_sequence != iobm->sequence)
-			switch_to_update_io_bitmap(tss, iobm);
+			tss_copy_io_bitmap(tss, iobm);
 
 		/* Enable the bitmap */
 		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
@@ -403,18 +431,8 @@ static inline void switch_to_bitmap(struct thread_struct *next,
 		 * limit.
 		 */
 		refresh_tss_limit();
-	} else if (tifp & _TIF_IO_BITMAP) {
-		/*
-		 * Do not touch the bitmap. Let the next bitmap using task
-		 * deal with the mess. Just make the io_bitmap_base invalid
-		 * by moving it outside the TSS limit so any subsequent I/O
-		 * access from user space will trigger a #GP.
-		 *
-		 * This is correct even when VMEXIT rewrites the TSS limit
-		 * to 0x67 as the only requirement is that the base points
-		 * outside the limit.
-		 */
-		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
+	} else {
+		tss_invalidate_io_bitmap(tss);
 	}
 }
 
@@ -628,7 +646,8 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p)
 
 	tifn = READ_ONCE(task_thread_info(next_p)->flags);
 	tifp = READ_ONCE(task_thread_info(prev_p)->flags);
-	switch_to_bitmap(next, tifp, tifn);
+
+	switch_to_bitmap(tifp);
 
 	propagate_user_return_notify(prev_p, next_p);
 

[patch V3 13/20] x86/ioperm: Remove bitmap if all permissions dropped

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

If ioperm() results in a bitmap with all bits set (no permissions to any
I/O port), then handling that bitmap on context switch and exit to user
mode is pointless. Drop it.

Move the bitmap exit handling to the ioport code and reuse it for both the
thread exit path and dropping it. This allows to reuse this code for the
upcoming iopl() emulation.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
---
V3: Reduced the preempt disable scope (Ingo)

V2: New patch
---
 arch/x86/include/asm/io_bitmap.h |    2 ++
 arch/x86/kernel/ioport.c         |   19 ++++++++++++++++++-
 arch/x86/kernel/process.c        |   15 ++-------------
 3 files changed, 22 insertions(+), 14 deletions(-)

--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -11,6 +11,8 @@ struct io_bitmap {
 	unsigned long	bitmap[IO_BITMAP_LONGS];
 };
 
+void io_bitmap_exit(void);
+
 void tss_update_io_bitmap(void);
 
 #endif
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -16,6 +16,18 @@
 
 static atomic64_t io_bitmap_sequence;
 
+void io_bitmap_exit(void)
+{
+	struct io_bitmap *iobm = current->thread.io_bitmap;
+
+	current->thread.io_bitmap = NULL;
+	clear_thread_flag(TIF_IO_BITMAP);
+	preempt_disable();
+	tss_update_io_bitmap();
+	preempt_enable();
+	kfree(iobm);
+}
+
 /*
  * this changes the io permissions bitmap in the current task.
  */
@@ -61,11 +73,16 @@ long ksys_ioperm(unsigned long from, uns
 	 * Search for a (possibly new) maximum. This is simple and stupid,
 	 * to keep it obviously correct:
 	 */
-	max_long = 0;
+	max_long = UINT_MAX;
 	for (i = 0; i < IO_BITMAP_LONGS; i++) {
 		if (iobm->bitmap[i] != ~0UL)
 			max_long = i;
 	}
+	/* All permissions dropped? */
+	if (max_long == UINT_MAX) {
+		io_bitmap_exit();
+		return 0;
+	}
 
 	iobm->max = (max_long + 1) * sizeof(unsigned long);
 
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -102,21 +102,10 @@ int arch_dup_task_struct(struct task_str
 void exit_thread(struct task_struct *tsk)
 {
 	struct thread_struct *t = &tsk->thread;
-	struct io_bitmap *iobm = t->io_bitmap;
 	struct fpu *fpu = &t->fpu;
-	struct tss_struct *tss;
 
-	if (iobm) {
-		preempt_disable();
-		tss = this_cpu_ptr(&cpu_tss_rw);
-
-		t->io_bitmap = NULL;
-		clear_thread_flag(TIF_IO_BITMAP);
-		/* Invalidate the io bitmap base in the TSS */
-		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
-		preempt_enable();
-		kfree(iobm);
-	}
+	if (test_thread_flag(TIF_IO_BITMAP))
+		io_bitmap_exit();
 
 	free_vm86(t);
 

[tip: x86/iopl] x86/ioperm: Remove bitmap if all permissions dropped

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     f16c41c9db8460874662b46f0db5c8af2a568157
Gitweb:        https://git.kernel.org/tip/f16c41c9db8460874662b46f0db5c8af2a568157
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:53 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:05 +01:00

x86/ioperm: Remove bitmap if all permissions dropped

If ioperm() results in a bitmap with all bits set (no permissions to any
I/O port), then handling that bitmap on context switch and exit to user
mode is pointless. Drop it.

Move the bitmap exit handling to the ioport code and reuse it for both the
thread exit path and dropping it. This allows to reuse this code for the
upcoming iopl() emulation.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.988865829@linutronix.de

---
 arch/x86/include/asm/io_bitmap.h |  2 ++
 arch/x86/kernel/ioport.c         | 19 ++++++++++++++++++-
 arch/x86/kernel/process.c        | 17 +++--------------
 3 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/io_bitmap.h b/arch/x86/include/asm/io_bitmap.h
index 6d82a37..784a88e 100644
--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -11,6 +11,8 @@ struct io_bitmap {
 	unsigned long	bitmap[IO_BITMAP_LONGS];
 };
 
+void io_bitmap_exit(void);
+
 void tss_update_io_bitmap(void);
 
 #endif
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 198bead..f9fc69a 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -16,6 +16,18 @@
 
 static atomic64_t io_bitmap_sequence;
 
+void io_bitmap_exit(void)
+{
+	struct io_bitmap *iobm = current->thread.io_bitmap;
+
+	current->thread.io_bitmap = NULL;
+	clear_thread_flag(TIF_IO_BITMAP);
+	preempt_disable();
+	tss_update_io_bitmap();
+	preempt_enable();
+	kfree(iobm);
+}
+
 /*
  * this changes the io permissions bitmap in the current task.
  */
@@ -61,11 +73,16 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 	 * Search for a (possibly new) maximum. This is simple and stupid,
 	 * to keep it obviously correct:
 	 */
-	max_long = 0;
+	max_long = UINT_MAX;
 	for (i = 0; i < IO_BITMAP_LONGS; i++) {
 		if (iobm->bitmap[i] != ~0UL)
 			max_long = i;
 	}
+	/* All permissions dropped? */
+	if (max_long == UINT_MAX) {
+		io_bitmap_exit();
+		return 0;
+	}
 
 	iobm->max = (max_long + 1) * sizeof(unsigned long);
 
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 1990011..75f8b13 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -102,21 +102,10 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 void exit_thread(struct task_struct *tsk)
 {
 	struct thread_struct *t = &tsk->thread;
-	struct io_bitmap *iobm = t->io_bitmap;
 	struct fpu *fpu = &t->fpu;
-	struct tss_struct *tss;
-
-	if (iobm) {
-		preempt_disable();
-		tss = this_cpu_ptr(&cpu_tss_rw);
-
-		t->io_bitmap = NULL;
-		clear_thread_flag(TIF_IO_BITMAP);
-		/* Invalidate the io bitmap base in the TSS */
-		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
-		preempt_enable();
-		kfree(iobm);
-	}
+
+	if (test_thread_flag(TIF_IO_BITMAP))
+		io_bitmap_exit();
 
 	free_vm86(t);
 

[patch V3 14/20] x86/ioperm: Share I/O bitmap if identical

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

The I/O bitmap is duplicated on fork. That's wasting memory and slows down
fork. There is no point to do so. As long as the bitmap is not modified it
can be shared between threads and processes.

Add a refcount and just share it on fork. If a task modifies the bitmap
then it has to do the duplication if and only if it is shared.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>

---
V3: Reset the ref count after duplicating io_bitmap. (Peter, Andy)

V2: New patch
---
 arch/x86/include/asm/io_bitmap.h |    5 ++++
 arch/x86/kernel/ioport.c         |   48 +++++++++++++++++++++++++++++++--------
 arch/x86/kernel/process.c        |   39 ++++---------------------------
 3 files changed, 50 insertions(+), 42 deletions(-)

--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -2,15 +2,20 @@
 #ifndef _ASM_X86_IOBITMAP_H
 #define _ASM_X86_IOBITMAP_H
 
+#include <linux/refcount.h>
 #include <asm/processor.h>
 
 struct io_bitmap {
 	u64		sequence;
+	refcount_t	refcnt;
 	/* The maximum number of bytes to copy so all zero bits are covered */
 	unsigned int	max;
 	unsigned long	bitmap[IO_BITMAP_LONGS];
 };
 
+struct task_struct;
+
+void io_bitmap_share(struct task_struct *tsk);
 void io_bitmap_exit(void);
 
 void tss_update_io_bitmap(void);
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -16,6 +16,17 @@
 
 static atomic64_t io_bitmap_sequence;
 
+void io_bitmap_share(struct task_struct *tsk)
+ {
+	/*
+	 * Take a refcount on current's bitmap. It can be used by
+	 * both tasks as long as none of them changes the bitmap.
+	 */
+	refcount_inc(&current->thread.io_bitmap->refcnt);
+	tsk->thread.io_bitmap = current->thread.io_bitmap;
+	set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
+}
+
 void io_bitmap_exit(void)
 {
 	struct io_bitmap *iobm = current->thread.io_bitmap;
@@ -25,7 +36,8 @@ void io_bitmap_exit(void)
 	preempt_disable();
 	tss_update_io_bitmap();
 	preempt_enable();
-	kfree(iobm);
+	if (iobm && refcount_dec_and_test(&iobm->refcnt))
+		kfree(iobm);
 }
 
 /*
@@ -58,9 +70,32 @@ long ksys_ioperm(unsigned long from, uns
 			return -ENOMEM;
 
 		memset(iobm->bitmap, 0xff, sizeof(iobm->bitmap));
+		refcount_set(&iobm->refcnt, 1);
+	}
+
+	/*
+	 * If the bitmap is not shared, then nothing can take a refcount as
+	 * current can obviously not fork at the same time. If it's shared
+	 * duplicate it and drop the refcount on the original one.
+	 */
+	if (refcount_read(&iobm->refcnt) > 1) {
+		iobm = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL);
+		if (!iobm)
+			return -ENOMEM;
+		refcount_set(&iobm->refcnt, 1);
+		io_bitmap_exit();
 	}
 
 	/*
+	 * Store the bitmap pointer (might be the same if the task already
+	 * head one). Must be done here so freeing the bitmap when all
+	 * permissions are dropped has the pointer set up.
+	 */
+	t->io_bitmap = iobm;
+	/* Mark it active for context switching and exit to user mode */
+	set_thread_flag(TIF_IO_BITMAP);
+
+	/*
 	 * Update the tasks bitmap. The update of the TSS bitmap happens on
 	 * exit to user mode. So this needs no protection.
 	 */
@@ -86,16 +121,11 @@ long ksys_ioperm(unsigned long from, uns
 
 	iobm->max = (max_long + 1) * sizeof(unsigned long);
 
-	/* Update the sequence number to force an update in switch_to() */
-	iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
-
 	/*
-	 * Store the bitmap pointer (might be the same if the task already
-	 * head one). Set the TIF flag, just in case this is the first
-	 * invocation.
+	 * Update the sequence number to force a TSS update on return to
+	 * user mode.
 	 */
-	t->io_bitmap = iobm;
-	set_thread_flag(TIF_IO_BITMAP);
+	iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
 
 	return 0;
 }
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -122,37 +122,13 @@ static int set_new_tls(struct task_struc
 		return do_set_thread_area_64(p, ARCH_SET_FS, tls);
 }
 
-static inline int copy_io_bitmap(struct task_struct *tsk)
-{
-	struct io_bitmap *iobm = current->thread.io_bitmap;
-
-	if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP)))
-		return 0;
-
-	tsk->thread.io_bitmap = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL);
-
-	if (!tsk->thread.io_bitmap)
-		return -ENOMEM;
-
-	set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
-	return 0;
-}
-
-static inline void free_io_bitmap(struct task_struct *tsk)
-{
-	if (tsk->thread.io_bitmap) {
-		kfree(tsk->thread.io_bitmap);
-		tsk->thread.io_bitmap = NULL;
-	}
-}
-
 int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 		    unsigned long arg, struct task_struct *p, unsigned long tls)
 {
 	struct inactive_task_frame *frame;
 	struct fork_frame *fork_frame;
 	struct pt_regs *childregs;
-	int ret;
+	int ret = 0;
 
 	childregs = task_pt_regs(p);
 	fork_frame = container_of(childregs, struct fork_frame, regs);
@@ -193,16 +169,13 @@ int copy_thread_tls(unsigned long clone_
 	task_user_gs(p) = get_user_gs(current_pt_regs());
 #endif
 
-	ret = copy_io_bitmap(p);
-	if (ret)
-		return ret;
-
 	/* Set a new TLS for the child thread? */
-	if (clone_flags & CLONE_SETTLS) {
+	if (clone_flags & CLONE_SETTLS)
 		ret = set_new_tls(p, tls);
-		if (ret)
-			free_io_bitmap(p);
-	}
+
+	if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP)))
+		io_bitmap_share(p);
+
 	return ret;
 }
 

[tip: x86/iopl] x86/ioperm: Share I/O bitmap if identical

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     b9027e7c44922bf1499adb76f87da7a374a48c22
Gitweb:        https://git.kernel.org/tip/b9027e7c44922bf1499adb76f87da7a374a48c22
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:54 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:05 +01:00

x86/ioperm: Share I/O bitmap if identical

The I/O bitmap is duplicated on fork. That's wasting memory and slows down
fork. There is no point to do so. As long as the bitmap is not modified it
can be shared between threads and processes.

Add a refcount and just share it on fork. If a task modifies the bitmap
then it has to do the duplication if and only if it is shared.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210105.078437077@linutronix.de


---
 arch/x86/include/asm/io_bitmap.h |  5 +++-
 arch/x86/kernel/ioport.c         | 48 +++++++++++++++++++++++++------
 arch/x86/kernel/process.c        | 39 +++----------------------
 3 files changed, 50 insertions(+), 42 deletions(-)

diff --git a/arch/x86/include/asm/io_bitmap.h b/arch/x86/include/asm/io_bitmap.h
index 784a88e..b664baa 100644
--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -2,15 +2,20 @@
 #ifndef _ASM_X86_IOBITMAP_H
 #define _ASM_X86_IOBITMAP_H
 
+#include <linux/refcount.h>
 #include <asm/processor.h>
 
 struct io_bitmap {
 	u64		sequence;
+	refcount_t	refcnt;
 	/* The maximum number of bytes to copy so all zero bits are covered */
 	unsigned int	max;
 	unsigned long	bitmap[IO_BITMAP_LONGS];
 };
 
+struct task_struct;
+
+void io_bitmap_share(struct task_struct *tsk);
 void io_bitmap_exit(void);
 
 void tss_update_io_bitmap(void);
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index f9fc69a..f82ca1c 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -16,6 +16,17 @@
 
 static atomic64_t io_bitmap_sequence;
 
+void io_bitmap_share(struct task_struct *tsk)
+ {
+	/*
+	 * Take a refcount on current's bitmap. It can be used by
+	 * both tasks as long as none of them changes the bitmap.
+	 */
+	refcount_inc(&current->thread.io_bitmap->refcnt);
+	tsk->thread.io_bitmap = current->thread.io_bitmap;
+	set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
+}
+
 void io_bitmap_exit(void)
 {
 	struct io_bitmap *iobm = current->thread.io_bitmap;
@@ -25,7 +36,8 @@ void io_bitmap_exit(void)
 	preempt_disable();
 	tss_update_io_bitmap();
 	preempt_enable();
-	kfree(iobm);
+	if (iobm && refcount_dec_and_test(&iobm->refcnt))
+		kfree(iobm);
 }
 
 /*
@@ -58,9 +70,32 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 			return -ENOMEM;
 
 		memset(iobm->bitmap, 0xff, sizeof(iobm->bitmap));
+		refcount_set(&iobm->refcnt, 1);
+	}
+
+	/*
+	 * If the bitmap is not shared, then nothing can take a refcount as
+	 * current can obviously not fork at the same time. If it's shared
+	 * duplicate it and drop the refcount on the original one.
+	 */
+	if (refcount_read(&iobm->refcnt) > 1) {
+		iobm = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL);
+		if (!iobm)
+			return -ENOMEM;
+		refcount_set(&iobm->refcnt, 1);
+		io_bitmap_exit();
 	}
 
 	/*
+	 * Store the bitmap pointer (might be the same if the task already
+	 * head one). Must be done here so freeing the bitmap when all
+	 * permissions are dropped has the pointer set up.
+	 */
+	t->io_bitmap = iobm;
+	/* Mark it active for context switching and exit to user mode */
+	set_thread_flag(TIF_IO_BITMAP);
+
+	/*
 	 * Update the tasks bitmap. The update of the TSS bitmap happens on
 	 * exit to user mode. So this needs no protection.
 	 */
@@ -86,16 +121,11 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 
 	iobm->max = (max_long + 1) * sizeof(unsigned long);
 
-	/* Update the sequence number to force an update in switch_to() */
-	iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
-
 	/*
-	 * Store the bitmap pointer (might be the same if the task already
-	 * head one). Set the TIF flag, just in case this is the first
-	 * invocation.
+	 * Update the sequence number to force a TSS update on return to
+	 * user mode.
 	 */
-	t->io_bitmap = iobm;
-	set_thread_flag(TIF_IO_BITMAP);
+	iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
 
 	return 0;
 }
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 75f8b13..bfc935d 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -122,37 +122,13 @@ static int set_new_tls(struct task_struct *p, unsigned long tls)
 		return do_set_thread_area_64(p, ARCH_SET_FS, tls);
 }
 
-static inline int copy_io_bitmap(struct task_struct *tsk)
-{
-	struct io_bitmap *iobm = current->thread.io_bitmap;
-
-	if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP)))
-		return 0;
-
-	tsk->thread.io_bitmap = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL);
-
-	if (!tsk->thread.io_bitmap)
-		return -ENOMEM;
-
-	set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
-	return 0;
-}
-
-static inline void free_io_bitmap(struct task_struct *tsk)
-{
-	if (tsk->thread.io_bitmap) {
-		kfree(tsk->thread.io_bitmap);
-		tsk->thread.io_bitmap = NULL;
-	}
-}
-
 int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 		    unsigned long arg, struct task_struct *p, unsigned long tls)
 {
 	struct inactive_task_frame *frame;
 	struct fork_frame *fork_frame;
 	struct pt_regs *childregs;
-	int ret;
+	int ret = 0;
 
 	childregs = task_pt_regs(p);
 	fork_frame = container_of(childregs, struct fork_frame, regs);
@@ -193,16 +169,13 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 	task_user_gs(p) = get_user_gs(current_pt_regs());
 #endif
 
-	ret = copy_io_bitmap(p);
-	if (ret)
-		return ret;
-
 	/* Set a new TLS for the child thread? */
-	if (clone_flags & CLONE_SETTLS) {
+	if (clone_flags & CLONE_SETTLS)
 		ret = set_new_tls(p, tls);
-		if (ret)
-			free_io_bitmap(p);
-	}
+
+	if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP)))
+		io_bitmap_share(p);
+
 	return ret;
 }
 

[patch V3 15/20] selftests/x86/ioperm: Extend testing so the shared bitmap is exercised

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

Add code to the fork path which forces the shared bitmap to be duplicated
and the reference count to be dropped. Verify that the child modifications
did not affect the parent.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
V2: New patch
---
 tools/testing/selftests/x86/ioperm.c |   16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

--- a/tools/testing/selftests/x86/ioperm.c
+++ b/tools/testing/selftests/x86/ioperm.c
@@ -131,6 +131,17 @@ int main(void)
 		printf("[RUN]\tchild: check that we inherited permissions\n");
 		expect_ok(0x80);
 		expect_gp(0xed);
+		printf("[RUN]\tchild: Extend permissions to 0x81\n");
+		if (ioperm(0x81, 1, 1) != 0) {
+			printf("[FAIL]\tioperm(0x81, 1, 1) failed (%d)", errno);
+			return 1;
+		}
+		printf("[RUN]\tchild: Drop permissions to 0x80\n");
+		if (ioperm(0x80, 1, 0) != 0) {
+			printf("[FAIL]\tioperm(0x80, 1, 0) failed (%d)", errno);
+			return 1;
+		}
+		expect_gp(0x80);
 		return 0;
 	} else {
 		int status;
@@ -146,8 +157,11 @@ int main(void)
 		}
 	}
 
-	/* Test the capability checks. */
+	/* Verify that the child dropping 0x80 did not affect the parent */
+	printf("\tVerify that unsharing the bitmap worked\n");
+	expect_ok(0x80);
 
+	/* Test the capability checks. */
 	printf("\tDrop privileges\n");
 	if (setresuid(1, 1, 1) != 0) {
 		printf("[WARN]\tDropping privileges failed\n");

[tip: x86/iopl] selftests/x86/ioperm: Extend testing so the shared bitmap is exercised

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     b7091d239d19ef5cf69b139902fda665f74fd7c1
Gitweb:        https://git.kernel.org/tip/b7091d239d19ef5cf69b139902fda665f74fd7c1
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:55 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:06 +01:00

selftests/x86/ioperm: Extend testing so the shared bitmap is exercised

Add code to the fork path which forces the shared bitmap to be duplicated
and the reference count to be dropped. Verify that the child modifications
did not affect the parent.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210105.169922940@linutronix.de


---
 tools/testing/selftests/x86/ioperm.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/x86/ioperm.c b/tools/testing/selftests/x86/ioperm.c
index 01de41c..57ec5e9 100644
--- a/tools/testing/selftests/x86/ioperm.c
+++ b/tools/testing/selftests/x86/ioperm.c
@@ -131,6 +131,17 @@ int main(void)
 		printf("[RUN]\tchild: check that we inherited permissions\n");
 		expect_ok(0x80);
 		expect_gp(0xed);
+		printf("[RUN]\tchild: Extend permissions to 0x81\n");
+		if (ioperm(0x81, 1, 1) != 0) {
+			printf("[FAIL]\tioperm(0x81, 1, 1) failed (%d)", errno);
+			return 1;
+		}
+		printf("[RUN]\tchild: Drop permissions to 0x80\n");
+		if (ioperm(0x80, 1, 0) != 0) {
+			printf("[FAIL]\tioperm(0x80, 1, 0) failed (%d)", errno);
+			return 1;
+		}
+		expect_gp(0x80);
 		return 0;
 	} else {
 		int status;
@@ -146,8 +157,11 @@ int main(void)
 		}
 	}
 
-	/* Test the capability checks. */
+	/* Verify that the child dropping 0x80 did not affect the parent */
+	printf("\tVerify that unsharing the bitmap worked\n");
+	expect_ok(0x80);
 
+	/* Test the capability checks. */
 	printf("\tDrop privileges\n");
 	if (setresuid(1, 1, 1) != 0) {
 		printf("[WARN]\tDropping privileges failed\n");

[patch V3 16/20] x86/iopl: Fixup misleading comment

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

The comment for the sys_iopl() implementation is outdated and actively
misleading in some parts. Fix it up.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/kernel/ioport.c |   35 +++++++++++++++++++++++++++--------
 1 file changed, 27 insertions(+), 8 deletions(-)

--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -41,7 +41,7 @@ void io_bitmap_exit(void)
 }
 
 /*
- * this changes the io permissions bitmap in the current task.
+ * This changes the io permissions bitmap in the current task.
  */
 long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 {
@@ -136,14 +136,24 @@ SYSCALL_DEFINE3(ioperm, unsigned long, f
 }
 
 /*
- * sys_iopl has to be used when you want to access the IO ports
- * beyond the 0x3ff range: to get the full 65536 ports bitmapped
- * you'd need 8kB of bitmaps/process, which is a bit excessive.
+ * The sys_iopl functionality depends on the level argument, which if
+ * granted for the task is used by the CPU to check I/O instruction and
+ * CLI/STI against the current priviledge level (CPL). If CPL is less than
+ * or equal the tasks IOPL level the instructions take effect. If not a #GP
+ * is raised. The default IOPL is 0, i.e. no permissions.
  *
- * Here we just change the flags value on the stack: we allow
- * only the super-user to do it. This depends on the stack-layout
- * on system-call entry - see also fork() and the signal handling
- * code.
+ * Setting IOPL to level 0-2 is disabling the userspace access. Only level
+ * 3 enables it. If set it allows the user space thread:
+ *
+ * - Unrestricted access to all 65535 I/O ports
+ * - The usage of CLI/STI instructions
+ *
+ * The advantage over ioperm is that the context switch does not require to
+ * update the I/O bitmap which is especially true when a large number of
+ * ports is accessed. But the allowance of CLI/STI in userspace is
+ * considered a major problem.
+ *
+ * IOPL is strictly per thread and inherited on fork.
  */
 SYSCALL_DEFINE1(iopl, unsigned int, level)
 {
@@ -164,9 +174,18 @@ SYSCALL_DEFINE1(iopl, unsigned int, leve
 		    security_locked_down(LOCKDOWN_IOPORT))
 			return -EPERM;
 	}
+	/*
+	 * Change the flags value on the return stack, which has been set
+	 * up on system-call entry. See also the fork and signal handling
+	 * code how this is handled.
+	 */
 	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
 		(level << X86_EFLAGS_IOPL_BIT);
+	/* Store the new level in the thread struct */
 	t->iopl = level << X86_EFLAGS_IOPL_BIT;
+	/*
+	 * X86_32 switches immediately and XEN handles it via emulation.
+	 */
 	set_iopl_mask(t->iopl);
 
 	return 0;

[tip: x86/iopl] x86/iopl: Fixup misleading comment

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     7543e168c1d3c135d21747e494d99e60550c3828
Gitweb:        https://git.kernel.org/tip/7543e168c1d3c135d21747e494d99e60550c3828
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:56 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:06 +01:00

x86/iopl: Fixup misleading comment

The comment for the sys_iopl() implementation is outdated and actively
misleading in some parts. Fix it up.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210105.276580787@linutronix.de

---
 arch/x86/kernel/ioport.c | 35 +++++++++++++++++++++++++++--------
 1 file changed, 27 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index f82ca1c..3548563 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -41,7 +41,7 @@ void io_bitmap_exit(void)
 }
 
 /*
- * this changes the io permissions bitmap in the current task.
+ * This changes the io permissions bitmap in the current task.
  */
 long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 {
@@ -136,14 +136,24 @@ SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
 }
 
 /*
- * sys_iopl has to be used when you want to access the IO ports
- * beyond the 0x3ff range: to get the full 65536 ports bitmapped
- * you'd need 8kB of bitmaps/process, which is a bit excessive.
+ * The sys_iopl functionality depends on the level argument, which if
+ * granted for the task is used by the CPU to check I/O instruction and
+ * CLI/STI against the current priviledge level (CPL). If CPL is less than
+ * or equal the tasks IOPL level the instructions take effect. If not a #GP
+ * is raised. The default IOPL is 0, i.e. no permissions.
  *
- * Here we just change the flags value on the stack: we allow
- * only the super-user to do it. This depends on the stack-layout
- * on system-call entry - see also fork() and the signal handling
- * code.
+ * Setting IOPL to level 0-2 is disabling the userspace access. Only level
+ * 3 enables it. If set it allows the user space thread:
+ *
+ * - Unrestricted access to all 65535 I/O ports
+ * - The usage of CLI/STI instructions
+ *
+ * The advantage over ioperm is that the context switch does not require to
+ * update the I/O bitmap which is especially true when a large number of
+ * ports is accessed. But the allowance of CLI/STI in userspace is
+ * considered a major problem.
+ *
+ * IOPL is strictly per thread and inherited on fork.
  */
 SYSCALL_DEFINE1(iopl, unsigned int, level)
 {
@@ -164,9 +174,18 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
 		    security_locked_down(LOCKDOWN_IOPORT))
 			return -EPERM;
 	}
+	/*
+	 * Change the flags value on the return stack, which has been set
+	 * up on system-call entry. See also the fork and signal handling
+	 * code how this is handled.
+	 */
 	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
 		(level << X86_EFLAGS_IOPL_BIT);
+	/* Store the new level in the thread struct */
 	t->iopl = level << X86_EFLAGS_IOPL_BIT;
+	/*
+	 * X86_32 switches immediately and XEN handles it via emulation.
+	 */
 	set_iopl_mask(t->iopl);
 
 	return 0;

[patch V3 17/20] x86/iopl: Restrict iopl() permission scope

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

The access to the full I/O port range can be also provided by the TSS I/O
bitmap, but that would require to copy 8k of data on scheduling in the
task. As shown with the sched out optimization TSS.io_bitmap_base can be
used to switch the incoming task to a preallocated I/O bitmap which has all
bits zero, i.e. allows access to all I/O ports.

Implementing this allows to provide an iopl() emulation mode which restricts
the IOPL level 3 permissions to I/O port access but removes the STI/CLI
permission which is coming with the hardware IOPL mechansim.

Provide a config option to switch IOPL to emulation mode, make it the
default and while at it also provide an option to disable IOPL completely.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
---
V3:	Folded the missing NULL pointer check, reduced preempt disable
	scope (Ingo)

V2:	Fixed the 32bit build fail by increasing the cpu entry area size
	Move the TSS update out of the iopl() emulation code.
---
 arch/x86/Kconfig                        |   32 +++++++++++
 arch/x86/include/asm/pgtable_32_types.h |    2 
 arch/x86/include/asm/processor.h        |   28 +++++++---
 arch/x86/kernel/cpu/common.c            |    5 +
 arch/x86/kernel/ioport.c                |   87 ++++++++++++++++++++++----------
 arch/x86/kernel/process.c               |   28 ++++++----
 6 files changed, 137 insertions(+), 45 deletions(-)

--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1254,6 +1254,38 @@ config X86_VSYSCALL_EMULATION
 	 Disabling this option saves about 7K of kernel size and
 	 possibly 4K of additional runtime pagetable memory.
 
+choice
+	prompt "IOPL"
+	default X86_IOPL_EMULATION
+
+config X86_IOPL_EMULATION
+	bool "IOPL Emulation"
+	---help---
+	  Legacy IOPL support is an overbroad mechanism which allows user
+	  space aside of accessing all 65536 I/O ports also to disable
+	  interrupts. To gain this access the caller needs CAP_SYS_RAWIO
+	  capabilities and permission from eventually active security
+	  modules.
+
+	  The emulation restricts the functionality of the syscall to
+	  only allowing the full range I/O port access, but prevents the
+	  ability to disable interrupts from user space.
+
+config X86_IOPL_LEGACY
+	bool "IOPL Legacy"
+	---help---
+	Allow the full IOPL permissions, i.e. user space access to all
+	65536 I/O ports and also the ability to disable interrupts, which
+	is overbroad and can result in system lockups.
+
+config X86_IOPL_NONE
+	bool "IOPL None"
+	---help---
+	Disable the IOPL permission syscall. That's the safest option as
+	no sane application should depend on this functionality.
+
+endchoice
+
 config TOSHIBA
 	tristate "Toshiba Laptop support"
 	depends on X86_32
--- a/arch/x86/include/asm/pgtable_32_types.h
+++ b/arch/x86/include/asm/pgtable_32_types.h
@@ -44,7 +44,7 @@ extern bool __vmalloc_start_set; /* set
  * Define this here and validate with BUILD_BUG_ON() in pgtable_32.c
  * to avoid include recursion hell
  */
-#define CPU_ENTRY_AREA_PAGES	(NR_CPUS * 40)
+#define CPU_ENTRY_AREA_PAGES	(NR_CPUS * 41)
 
 #define CPU_ENTRY_AREA_BASE						\
 	((FIXADDR_TOT_START - PAGE_SIZE * (CPU_ENTRY_AREA_PAGES + 1))   \
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -332,19 +332,21 @@ struct x86_hw_tss {
 #define IO_BITMAP_BYTES			(IO_BITMAP_BITS / BITS_PER_BYTE)
 #define IO_BITMAP_LONGS			(IO_BITMAP_BYTES / sizeof(long))
 
-#define IO_BITMAP_OFFSET_VALID					\
+#define IO_BITMAP_OFFSET_VALID_MAP				\
 	(offsetof(struct tss_struct, io_bitmap.bitmap) -	\
 	 offsetof(struct tss_struct, x86_tss))
 
+#define IO_BITMAP_OFFSET_VALID_ALL				\
+	(offsetof(struct tss_struct, io_bitmap.mapall) -	\
+	 offsetof(struct tss_struct, x86_tss))
+
 /*
- * sizeof(unsigned long) coming from an extra "long" at the end
- * of the iobitmap.
- *
- * -1? seg base+limit should be pointing to the address of the
- * last valid byte
+ * sizeof(unsigned long) coming from an extra "long" at the end of the
+ * iobitmap. The limit is inclusive, i.e. the last valid byte.
  */
 #define __KERNEL_TSS_LIMIT	\
-	(IO_BITMAP_OFFSET_VALID + IO_BITMAP_BYTES + sizeof(unsigned long) - 1)
+	(IO_BITMAP_OFFSET_VALID_ALL + IO_BITMAP_BYTES + \
+	 sizeof(unsigned long) - 1)
 
 /* Base offset outside of TSS_LIMIT so unpriviledged IO causes #GP */
 #define IO_BITMAP_OFFSET_INVALID	(__KERNEL_TSS_LIMIT + 1)
@@ -380,6 +382,12 @@ struct x86_io_bitmap {
 	 * be within the limit.
 	 */
 	unsigned long		bitmap[IO_BITMAP_LONGS + 1];
+
+	/*
+	 * Special I/O bitmap to emulate IOPL(3). All bytes zero,
+	 * except the additional byte at the end.
+	 */
+	unsigned long		mapall[IO_BITMAP_LONGS + 1];
 };
 
 struct tss_struct {
@@ -506,7 +514,13 @@ struct thread_struct {
 #endif
 	/* IO permissions: */
 	struct io_bitmap	*io_bitmap;
+
+	/*
+	 * IOPL. Priviledge level dependent I/O permission which includes
+	 * user space CLI/STI when granted.
+	 */
 	unsigned long		iopl;
+	unsigned long		iopl_emul;
 
 	mm_segment_t		addr_limit;
 
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1864,6 +1864,11 @@ void cpu_init(void)
 	tss->io_bitmap.prev_max = 0;
 	tss->io_bitmap.prev_sequence = 0;
 	memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
+	/*
+	 * Invalidate the extra array entry past the end of the all
+	 * permission bitmap as required by the hardware.
+	 */
+	tss->io_bitmap.mapall[IO_BITMAP_LONGS] = ~0UL;
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
 	load_TR_desc();
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -17,25 +17,41 @@
 static atomic64_t io_bitmap_sequence;
 
 void io_bitmap_share(struct task_struct *tsk)
- {
-	/*
-	 * Take a refcount on current's bitmap. It can be used by
-	 * both tasks as long as none of them changes the bitmap.
-	 */
-	refcount_inc(&current->thread.io_bitmap->refcnt);
-	tsk->thread.io_bitmap = current->thread.io_bitmap;
+{
+	/* Can be NULL when current->thread.iopl_emul == 3 */
+	if (current->thread.io_bitmap) {
+		/*
+		 * Take a refcount on current's bitmap. It can be used by
+		 * both tasks as long as none of them changes the bitmap.
+		 */
+		refcount_inc(&current->thread.io_bitmap->refcnt);
+		tsk->thread.io_bitmap = current->thread.io_bitmap;
+	}
 	set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
 }
 
+static void task_update_io_bitmap(void)
+{
+	struct thread_struct *t = &current->thread;
+
+	if (t->iopl_emul == 3 || t->io_bitmap) {
+		/* TSS update is handled on exit to user space */
+		set_thread_flag(TIF_IO_BITMAP);
+	} else {
+		clear_thread_flag(TIF_IO_BITMAP);
+		/* Invalidate TSS */
+		preempt_disable();
+		tss_update_io_bitmap();
+		preempt_enable();
+	}
+}
+
 void io_bitmap_exit(void)
 {
 	struct io_bitmap *iobm = current->thread.io_bitmap;
 
 	current->thread.io_bitmap = NULL;
-	clear_thread_flag(TIF_IO_BITMAP);
-	preempt_disable();
-	tss_update_io_bitmap();
-	preempt_enable();
+	task_update_io_bitmap();
 	if (iobm && refcount_dec_and_test(&iobm->refcnt))
 		kfree(iobm);
 }
@@ -157,36 +173,55 @@ SYSCALL_DEFINE3(ioperm, unsigned long, f
  */
 SYSCALL_DEFINE1(iopl, unsigned int, level)
 {
-	struct pt_regs *regs = current_pt_regs();
 	struct thread_struct *t = &current->thread;
+	struct pt_regs *regs = current_pt_regs();
+	unsigned int old;
 
 	/*
 	 * Careful: the IOPL bits in regs->flags are undefined under Xen PV
 	 * and changing them has no effect.
 	 */
-	unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT;
+	if (IS_ENABLED(CONFIG_X86_IOPL_NONE))
+		return -ENOSYS;
 
 	if (level > 3)
 		return -EINVAL;
+
+	if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION))
+		old = t->iopl_emul;
+	else
+		old = t->iopl >> X86_EFLAGS_IOPL_BIT;
+
+	/* No point in going further if nothing changes */
+	if (level == old)
+		return 0;
+
 	/* Trying to gain more privileges? */
 	if (level > old) {
 		if (!capable(CAP_SYS_RAWIO) ||
 		    security_locked_down(LOCKDOWN_IOPORT))
 			return -EPERM;
 	}
-	/*
-	 * Change the flags value on the return stack, which has been set
-	 * up on system-call entry. See also the fork and signal handling
-	 * code how this is handled.
-	 */
-	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
-		(level << X86_EFLAGS_IOPL_BIT);
-	/* Store the new level in the thread struct */
-	t->iopl = level << X86_EFLAGS_IOPL_BIT;
-	/*
-	 * X86_32 switches immediately and XEN handles it via emulation.
-	 */
-	set_iopl_mask(t->iopl);
+
+	if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION)) {
+		t->iopl_emul = level;
+		task_update_io_bitmap();
+	} else {
+		/*
+		 * Change the flags value on the return stack, which has
+		 * been set up on system-call entry. See also the fork and
+		 * signal handling code how this is handled.
+		 */
+		regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
+			(level << X86_EFLAGS_IOPL_BIT);
+		/* Store the new level in the thread struct */
+		t->iopl = level << X86_EFLAGS_IOPL_BIT;
+		/*
+		 * X86_32 switches immediately and XEN handles it via
+		 * emulation.
+		 */
+		set_iopl_mask(t->iopl);
+	}
 
 	return 0;
 }
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -370,21 +370,27 @@ static void tss_copy_io_bitmap(struct ts
 void tss_update_io_bitmap(void)
 {
 	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
+	u16 *base = &tss->x86_tss.io_bitmap_base;
 
 	if (test_thread_flag(TIF_IO_BITMAP)) {
-		struct io_bitmap *iobm = current->thread.io_bitmap;
+		struct thread_struct *t = &current->thread;
 
-		/*
-		 * Only copy bitmap data when the sequence number
-		 * differs. The update time is accounted to the incoming
-		 * task.
-		 */
-		if (tss->io_bitmap.prev_sequence != iobm->sequence)
-			tss_copy_io_bitmap(tss, iobm);
-
-		/* Enable the bitmap */
-		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
+		if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION) &&
+		    t->iopl_emul == 3) {
+			*base = IO_BITMAP_OFFSET_VALID_ALL;
+		} else {
+			struct io_bitmap *iobm = t->io_bitmap;
+			/*
+			 * Only copy bitmap data when the sequence number
+			 * differs. The update time is accounted to the
+			 * incoming task.
+			 */
+			if (tss->io_bitmap.prev_sequence != iobm->sequence)
+				tss_copy_io_bitmap(tss, iobm);
 
+			/* Enable the bitmap */
+			*base = IO_BITMAP_OFFSET_VALID_MAP;
+		}
 		/*
 		 * Make sure that the TSS limit is covering the io bitmap.
 		 * It might have been cut down by a VMEXIT to 0x67 which

Re: [patch V3 17/20] x86/iopl: Restrict iopl() permission scope

[Borislav Petkov]

On Wed, Nov 13, 2019 at 09:42:57PM +0100, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
> 
> The access to the full I/O port range can be also provided by the TSS I/O
> bitmap, but that would require to copy 8k of data on scheduling in the
> task. As shown with the sched out optimization TSS.io_bitmap_base can be
> used to switch the incoming task to a preallocated I/O bitmap which has all
> bits zero, i.e. allows access to all I/O ports.
> 
> Implementing this allows to provide an iopl() emulation mode which restricts
> the IOPL level 3 permissions to I/O port access but removes the STI/CLI
> permission which is coming with the hardware IOPL mechansim.
> 
> Provide a config option to switch IOPL to emulation mode, make it the
> default and while at it also provide an option to disable IOPL completely.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Acked-by: Andy Lutomirski <luto@kernel.org>
> ---
> V3:	Folded the missing NULL pointer check, reduced preempt disable
> 	scope (Ingo)
> 
> V2:	Fixed the 32bit build fail by increasing the cpu entry area size
> 	Move the TSS update out of the iopl() emulation code.
> ---
>  arch/x86/Kconfig                        |   32 +++++++++++
>  arch/x86/include/asm/pgtable_32_types.h |    2 
>  arch/x86/include/asm/processor.h        |   28 +++++++---
>  arch/x86/kernel/cpu/common.c            |    5 +
>  arch/x86/kernel/ioport.c                |   87 ++++++++++++++++++++++----------
>  arch/x86/kernel/process.c               |   28 ++++++----
>  6 files changed, 137 insertions(+), 45 deletions(-)
> 
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1254,6 +1254,38 @@ config X86_VSYSCALL_EMULATION
>  	 Disabling this option saves about 7K of kernel size and
>  	 possibly 4K of additional runtime pagetable memory.
>  
> +choice
> +	prompt "IOPL"
> +	default X86_IOPL_EMULATION
> +
> +config X86_IOPL_EMULATION
> +	bool "IOPL Emulation"
> +	---help---
> +	  Legacy IOPL support is an overbroad mechanism which allows user
> +	  space aside of accessing all 65536 I/O ports also to disable
> +	  interrupts. To gain this access the caller needs CAP_SYS_RAWIO
> +	  capabilities and permission from eventually active security

I think you mean here: s/eventually/potentially/ or so. "eventually" is
one of the false friends. :)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [patch V3 17/20] x86/iopl: Restrict iopl() permission scope

[Thomas Gleixner]

On Thu, 14 Nov 2019, Borislav Petkov wrote:
> On Wed, Nov 13, 2019 at 09:42:57PM +0100, Thomas Gleixner wrote:
> > +config X86_IOPL_EMULATION
> > +	bool "IOPL Emulation"
> > +	---help---
> > +	  Legacy IOPL support is an overbroad mechanism which allows user
> > +	  space aside of accessing all 65536 I/O ports also to disable
> > +	  interrupts. To gain this access the caller needs CAP_SYS_RAWIO
> > +	  capabilities and permission from eventually active security
> 
> I think you mean here: s/eventually/potentially/ or so. "eventually" is
> one of the false friends. :)

Fixed

[tip: x86/iopl] x86/iopl: Restrict iopl() permission scope

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     ede65f28e61e5a5ccf6c46d9c8169abbd89fe24d
Gitweb:        https://git.kernel.org/tip/ede65f28e61e5a5ccf6c46d9c8169abbd89fe24d
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:57 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:07 +01:00

x86/iopl: Restrict iopl() permission scope

The access to the full I/O port range can be also provided by the TSS I/O
bitmap, but that would require to copy 8k of data on scheduling in the
task. As shown with the sched out optimization TSS.io_bitmap_base can be
used to switch the incoming task to a preallocated I/O bitmap which has all
bits zero, i.e. allows access to all I/O ports.

Implementing this allows to provide an iopl() emulation mode which restricts
the IOPL level 3 permissions to I/O port access but removes the STI/CLI
permission which is coming with the hardware IOPL mechansim.

Provide a config option to switch IOPL to emulation mode, make it the
default and while at it also provide an option to disable IOPL completely.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210105.369055550@linutronix.de

---
 arch/x86/Kconfig                        | 32 +++++++++-
 arch/x86/include/asm/pgtable_32_types.h |  2 +-
 arch/x86/include/asm/processor.h        | 28 ++++++--
 arch/x86/kernel/cpu/common.c            |  5 +-
 arch/x86/kernel/ioport.c                | 87 ++++++++++++++++--------
 arch/x86/kernel/process.c               | 32 +++++----
 6 files changed, 139 insertions(+), 47 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d6e1faa..2aad1cd 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1254,6 +1254,38 @@ config X86_VSYSCALL_EMULATION
 	 Disabling this option saves about 7K of kernel size and
 	 possibly 4K of additional runtime pagetable memory.
 
+choice
+	prompt "IOPL"
+	default X86_IOPL_EMULATION
+
+config X86_IOPL_EMULATION
+	bool "IOPL Emulation"
+	---help---
+	  Legacy IOPL support is an overbroad mechanism which allows user
+	  space aside of accessing all 65536 I/O ports also to disable
+	  interrupts. To gain this access the caller needs CAP_SYS_RAWIO
+	  capabilities and permission from potentially active security
+	  modules.
+
+	  The emulation restricts the functionality of the syscall to
+	  only allowing the full range I/O port access, but prevents the
+	  ability to disable interrupts from user space.
+
+config X86_IOPL_LEGACY
+	bool "IOPL Legacy"
+	---help---
+	Allow the full IOPL permissions, i.e. user space access to all
+	65536 I/O ports and also the ability to disable interrupts, which
+	is overbroad and can result in system lockups.
+
+config X86_IOPL_NONE
+	bool "IOPL None"
+	---help---
+	Disable the IOPL permission syscall. That's the safest option as
+	no sane application should depend on this functionality.
+
+endchoice
+
 config TOSHIBA
 	tristate "Toshiba Laptop support"
 	depends on X86_32
diff --git a/arch/x86/include/asm/pgtable_32_types.h b/arch/x86/include/asm/pgtable_32_types.h
index b0bc0ff..0fab4bf 100644
--- a/arch/x86/include/asm/pgtable_32_types.h
+++ b/arch/x86/include/asm/pgtable_32_types.h
@@ -44,7 +44,7 @@ extern bool __vmalloc_start_set; /* set once high_memory is set */
  * Define this here and validate with BUILD_BUG_ON() in pgtable_32.c
  * to avoid include recursion hell
  */
-#define CPU_ENTRY_AREA_PAGES	(NR_CPUS * 40)
+#define CPU_ENTRY_AREA_PAGES	(NR_CPUS * 41)
 
 #define CPU_ENTRY_AREA_BASE						\
 	((FIXADDR_TOT_START - PAGE_SIZE * (CPU_ENTRY_AREA_PAGES + 1))   \
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 40bb0f7..b0e02aa 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -332,19 +332,21 @@ struct x86_hw_tss {
 #define IO_BITMAP_BYTES			(IO_BITMAP_BITS / BITS_PER_BYTE)
 #define IO_BITMAP_LONGS			(IO_BITMAP_BYTES / sizeof(long))
 
-#define IO_BITMAP_OFFSET_VALID					\
+#define IO_BITMAP_OFFSET_VALID_MAP				\
 	(offsetof(struct tss_struct, io_bitmap.bitmap) -	\
 	 offsetof(struct tss_struct, x86_tss))
 
+#define IO_BITMAP_OFFSET_VALID_ALL				\
+	(offsetof(struct tss_struct, io_bitmap.mapall) -	\
+	 offsetof(struct tss_struct, x86_tss))
+
 /*
- * sizeof(unsigned long) coming from an extra "long" at the end
- * of the iobitmap.
- *
- * -1? seg base+limit should be pointing to the address of the
- * last valid byte
+ * sizeof(unsigned long) coming from an extra "long" at the end of the
+ * iobitmap. The limit is inclusive, i.e. the last valid byte.
  */
 #define __KERNEL_TSS_LIMIT	\
-	(IO_BITMAP_OFFSET_VALID + IO_BITMAP_BYTES + sizeof(unsigned long) - 1)
+	(IO_BITMAP_OFFSET_VALID_ALL + IO_BITMAP_BYTES + \
+	 sizeof(unsigned long) - 1)
 
 /* Base offset outside of TSS_LIMIT so unpriviledged IO causes #GP */
 #define IO_BITMAP_OFFSET_INVALID	(__KERNEL_TSS_LIMIT + 1)
@@ -380,6 +382,12 @@ struct x86_io_bitmap {
 	 * be within the limit.
 	 */
 	unsigned long		bitmap[IO_BITMAP_LONGS + 1];
+
+	/*
+	 * Special I/O bitmap to emulate IOPL(3). All bytes zero,
+	 * except the additional byte at the end.
+	 */
+	unsigned long		mapall[IO_BITMAP_LONGS + 1];
 };
 
 struct tss_struct {
@@ -506,7 +514,13 @@ struct thread_struct {
 #endif
 	/* IO permissions: */
 	struct io_bitmap	*io_bitmap;
+
+	/*
+	 * IOPL. Priviledge level dependent I/O permission which includes
+	 * user space CLI/STI when granted.
+	 */
 	unsigned long		iopl;
+	unsigned long		iopl_emul;
 
 	mm_segment_t		addr_limit;
 
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 79dd544..7bf402b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1864,6 +1864,11 @@ void cpu_init(void)
 	tss->io_bitmap.prev_max = 0;
 	tss->io_bitmap.prev_sequence = 0;
 	memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
+	/*
+	 * Invalidate the extra array entry past the end of the all
+	 * permission bitmap as required by the hardware.
+	 */
+	tss->io_bitmap.mapall[IO_BITMAP_LONGS] = ~0UL;
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
 	load_TR_desc();
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 3548563..9ed9458 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -17,25 +17,41 @@
 static atomic64_t io_bitmap_sequence;
 
 void io_bitmap_share(struct task_struct *tsk)
- {
-	/*
-	 * Take a refcount on current's bitmap. It can be used by
-	 * both tasks as long as none of them changes the bitmap.
-	 */
-	refcount_inc(&current->thread.io_bitmap->refcnt);
-	tsk->thread.io_bitmap = current->thread.io_bitmap;
+{
+	/* Can be NULL when current->thread.iopl_emul == 3 */
+	if (current->thread.io_bitmap) {
+		/*
+		 * Take a refcount on current's bitmap. It can be used by
+		 * both tasks as long as none of them changes the bitmap.
+		 */
+		refcount_inc(&current->thread.io_bitmap->refcnt);
+		tsk->thread.io_bitmap = current->thread.io_bitmap;
+	}
 	set_tsk_thread_flag(tsk, TIF_IO_BITMAP);
 }
 
+static void task_update_io_bitmap(void)
+{
+	struct thread_struct *t = &current->thread;
+
+	if (t->iopl_emul == 3 || t->io_bitmap) {
+		/* TSS update is handled on exit to user space */
+		set_thread_flag(TIF_IO_BITMAP);
+	} else {
+		clear_thread_flag(TIF_IO_BITMAP);
+		/* Invalidate TSS */
+		preempt_disable();
+		tss_update_io_bitmap();
+		preempt_enable();
+	}
+}
+
 void io_bitmap_exit(void)
 {
 	struct io_bitmap *iobm = current->thread.io_bitmap;
 
 	current->thread.io_bitmap = NULL;
-	clear_thread_flag(TIF_IO_BITMAP);
-	preempt_disable();
-	tss_update_io_bitmap();
-	preempt_enable();
+	task_update_io_bitmap();
 	if (iobm && refcount_dec_and_test(&iobm->refcnt))
 		kfree(iobm);
 }
@@ -157,36 +173,55 @@ SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
  */
 SYSCALL_DEFINE1(iopl, unsigned int, level)
 {
-	struct pt_regs *regs = current_pt_regs();
 	struct thread_struct *t = &current->thread;
+	struct pt_regs *regs = current_pt_regs();
+	unsigned int old;
 
 	/*
 	 * Careful: the IOPL bits in regs->flags are undefined under Xen PV
 	 * and changing them has no effect.
 	 */
-	unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT;
+	if (IS_ENABLED(CONFIG_X86_IOPL_NONE))
+		return -ENOSYS;
 
 	if (level > 3)
 		return -EINVAL;
+
+	if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION))
+		old = t->iopl_emul;
+	else
+		old = t->iopl >> X86_EFLAGS_IOPL_BIT;
+
+	/* No point in going further if nothing changes */
+	if (level == old)
+		return 0;
+
 	/* Trying to gain more privileges? */
 	if (level > old) {
 		if (!capable(CAP_SYS_RAWIO) ||
 		    security_locked_down(LOCKDOWN_IOPORT))
 			return -EPERM;
 	}
-	/*
-	 * Change the flags value on the return stack, which has been set
-	 * up on system-call entry. See also the fork and signal handling
-	 * code how this is handled.
-	 */
-	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
-		(level << X86_EFLAGS_IOPL_BIT);
-	/* Store the new level in the thread struct */
-	t->iopl = level << X86_EFLAGS_IOPL_BIT;
-	/*
-	 * X86_32 switches immediately and XEN handles it via emulation.
-	 */
-	set_iopl_mask(t->iopl);
+
+	if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION)) {
+		t->iopl_emul = level;
+		task_update_io_bitmap();
+	} else {
+		/*
+		 * Change the flags value on the return stack, which has
+		 * been set up on system-call entry. See also the fork and
+		 * signal handling code how this is handled.
+		 */
+		regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
+			(level << X86_EFLAGS_IOPL_BIT);
+		/* Store the new level in the thread struct */
+		t->iopl = level << X86_EFLAGS_IOPL_BIT;
+		/*
+		 * X86_32 switches immediately and XEN handles it via
+		 * emulation.
+		 */
+		set_iopl_mask(t->iopl);
+	}
 
 	return 0;
 }
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index bfc935d..8ba2707 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -370,21 +370,27 @@ static void tss_copy_io_bitmap(struct tss_struct *tss, struct io_bitmap *iobm)
 void tss_update_io_bitmap(void)
 {
 	struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
+	u16 *base = &tss->x86_tss.io_bitmap_base;
 
 	if (test_thread_flag(TIF_IO_BITMAP)) {
-		struct io_bitmap *iobm = current->thread.io_bitmap;
-
-		/*
-		 * Only copy bitmap data when the sequence number
-		 * differs. The update time is accounted to the incoming
-		 * task.
-		 */
-		if (tss->io_bitmap.prev_sequence != iobm->sequence)
-			tss_copy_io_bitmap(tss, iobm);
-
-		/* Enable the bitmap */
-		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
-
+		struct thread_struct *t = &current->thread;
+
+		if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION) &&
+		    t->iopl_emul == 3) {
+			*base = IO_BITMAP_OFFSET_VALID_ALL;
+		} else {
+			struct io_bitmap *iobm = t->io_bitmap;
+			/*
+			 * Only copy bitmap data when the sequence number
+			 * differs. The update time is accounted to the
+			 * incoming task.
+			 */
+			if (tss->io_bitmap.prev_sequence != iobm->sequence)
+				tss_copy_io_bitmap(tss, iobm);
+
+			/* Enable the bitmap */
+			*base = IO_BITMAP_OFFSET_VALID_MAP;
+		}
 		/*
 		 * Make sure that the TSS limit is covering the io bitmap.
 		 * It might have been cut down by a VMEXIT to 0x67 which

[patch V3 18/20] x86/iopl: Remove legacy IOPL option

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

The IOPL emulation via the I/O bitmap is sufficient. Remove the legacy
cruft dealing with the (e)flags based IOPL mechanism.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Juergen Gross <jgross@suse.com> (Paravirt and Xen parts)
Acked-by: Andy Lutomirski <luto@kernel.org>

---
V3: Simplified config option (removed the choice)

V2: Adapted to changes in the previous patches.
---
 arch/x86/Kconfig                      |   23 ++--------------
 arch/x86/include/asm/paravirt.h       |    4 --
 arch/x86/include/asm/paravirt_types.h |    2 -
 arch/x86/include/asm/processor.h      |   26 ++----------------
 arch/x86/include/asm/xen/hypervisor.h |    2 -
 arch/x86/kernel/ioport.c              |   47 +++++++---------------------------
 arch/x86/kernel/paravirt.c            |    2 -
 arch/x86/kernel/process_32.c          |    9 ------
 arch/x86/kernel/process_64.c          |   11 -------
 arch/x86/xen/enlighten_pv.c           |   10 -------
 10 files changed, 17 insertions(+), 119 deletions(-)

--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1254,12 +1254,9 @@ config X86_VSYSCALL_EMULATION
 	 Disabling this option saves about 7K of kernel size and
 	 possibly 4K of additional runtime pagetable memory.
 
-choice
-	prompt "IOPL"
-	default X86_IOPL_EMULATION
-
 config X86_IOPL_EMULATION
 	bool "IOPL Emulation"
+	default y
 	---help---
 	  Legacy IOPL support is an overbroad mechanism which allows user
 	  space aside of accessing all 65536 I/O ports also to disable
@@ -1269,22 +1266,8 @@ config X86_IOPL_EMULATION
 
 	  The emulation restricts the functionality of the syscall to
 	  only allowing the full range I/O port access, but prevents the
-	  ability to disable interrupts from user space.
-
-config X86_IOPL_LEGACY
-	bool "IOPL Legacy"
-	---help---
-	Allow the full IOPL permissions, i.e. user space access to all
-	65536 I/O ports and also the ability to disable interrupts, which
-	is overbroad and can result in system lockups.
-
-config X86_IOPL_NONE
-	bool "IOPL None"
-	---help---
-	Disable the IOPL permission syscall. That's the safest option as
-	no sane application should depend on this functionality.
-
-endchoice
+	  ability to disable interrupts from user space which would be
+	  granted if the hardware IOPL mechanism would be used.
 
 config TOSHIBA
 	tristate "Toshiba Laptop support"
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -294,10 +294,6 @@ static inline void write_idt_entry(gate_
 {
 	PVOP_VCALL3(cpu.write_idt_entry, dt, entry, g);
 }
-static inline void set_iopl_mask(unsigned mask)
-{
-	PVOP_VCALL1(cpu.set_iopl_mask, mask);
-}
 
 static inline void paravirt_activate_mm(struct mm_struct *prev,
 					struct mm_struct *next)
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -140,8 +140,6 @@ struct pv_cpu_ops {
 
 	void (*load_sp0)(unsigned long sp0);
 
-	void (*set_iopl_mask)(unsigned mask);
-
 	void (*wbinvd)(void);
 
 	/* cpuid emulation, mostly so that caps bits can be disabled */
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -516,10 +516,10 @@ struct thread_struct {
 	struct io_bitmap	*io_bitmap;
 
 	/*
-	 * IOPL. Priviledge level dependent I/O permission which includes
-	 * user space CLI/STI when granted.
+	 * IOPL. Priviledge level dependent I/O permission which is
+	 * emulated via the I/O bitmap to prevent user space from disabling
+	 * interrupts.
 	 */
-	unsigned long		iopl;
 	unsigned long		iopl_emul;
 
 	mm_segment_t		addr_limit;
@@ -552,25 +552,6 @@ static inline void arch_thread_struct_wh
  */
 #define TS_COMPAT		0x0002	/* 32bit syscall active (64BIT)*/
 
-/*
- * Set IOPL bits in EFLAGS from given mask
- */
-static inline void native_set_iopl_mask(unsigned mask)
-{
-#ifdef CONFIG_X86_32
-	unsigned int reg;
-
-	asm volatile ("pushfl;"
-		      "popl %0;"
-		      "andl %1, %0;"
-		      "orl %2, %0;"
-		      "pushl %0;"
-		      "popfl"
-		      : "=&r" (reg)
-		      : "i" (~X86_EFLAGS_IOPL), "r" (mask));
-#endif
-}
-
 static inline void
 native_load_sp0(unsigned long sp0)
 {
@@ -610,7 +591,6 @@ static inline void load_sp0(unsigned lon
 	native_load_sp0(sp0);
 }
 
-#define set_iopl_mask native_set_iopl_mask
 #endif /* CONFIG_PARAVIRT_XXL */
 
 /* Free all resources held by a thread. */
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -62,6 +62,4 @@ void xen_arch_register_cpu(int num);
 void xen_arch_unregister_cpu(int num);
 #endif
 
-extern void xen_set_iopl_mask(unsigned mask);
-
 #endif /* _ASM_X86_XEN_HYPERVISOR_H */
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -153,28 +153,23 @@ SYSCALL_DEFINE3(ioperm, unsigned long, f
 
 /*
  * The sys_iopl functionality depends on the level argument, which if
- * granted for the task is used by the CPU to check I/O instruction and
- * CLI/STI against the current priviledge level (CPL). If CPL is less than
- * or equal the tasks IOPL level the instructions take effect. If not a #GP
- * is raised. The default IOPL is 0, i.e. no permissions.
+ * granted for the task is used to enable access to all 65536 I/O ports.
  *
- * Setting IOPL to level 0-2 is disabling the userspace access. Only level
- * 3 enables it. If set it allows the user space thread:
+ * This does not use the IOPL mechanism provided by the CPU as that would
+ * also allow the user space task to use the CLI/STI instructions.
  *
- * - Unrestricted access to all 65535 I/O ports
- * - The usage of CLI/STI instructions
+ * Disabling interrupts in a user space task is dangerous as it might lock
+ * up the machine and the semantics vs. syscalls and exceptions is
+ * undefined.
  *
- * The advantage over ioperm is that the context switch does not require to
- * update the I/O bitmap which is especially true when a large number of
- * ports is accessed. But the allowance of CLI/STI in userspace is
- * considered a major problem.
+ * Setting IOPL to level 0-2 is disabling I/O permissions. Level 3
+ * 3 enables them.
  *
  * IOPL is strictly per thread and inherited on fork.
  */
 SYSCALL_DEFINE1(iopl, unsigned int, level)
 {
 	struct thread_struct *t = &current->thread;
-	struct pt_regs *regs = current_pt_regs();
 	unsigned int old;
 
 	/*
@@ -187,10 +182,7 @@ SYSCALL_DEFINE1(iopl, unsigned int, leve
 	if (level > 3)
 		return -EINVAL;
 
-	if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION))
-		old = t->iopl_emul;
-	else
-		old = t->iopl >> X86_EFLAGS_IOPL_BIT;
+	old = t->iopl_emul;
 
 	/* No point in going further if nothing changes */
 	if (level == old)
@@ -203,25 +195,8 @@ SYSCALL_DEFINE1(iopl, unsigned int, leve
 			return -EPERM;
 	}
 
-	if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION)) {
-		t->iopl_emul = level;
-		task_update_io_bitmap();
-	} else {
-		/*
-		 * Change the flags value on the return stack, which has
-		 * been set up on system-call entry. See also the fork and
-		 * signal handling code how this is handled.
-		 */
-		regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
-			(level << X86_EFLAGS_IOPL_BIT);
-		/* Store the new level in the thread struct */
-		t->iopl = level << X86_EFLAGS_IOPL_BIT;
-		/*
-		 * X86_32 switches immediately and XEN handles it via
-		 * emulation.
-		 */
-		set_iopl_mask(t->iopl);
-	}
+	t->iopl_emul = level;
+	task_update_io_bitmap();
 
 	return 0;
 }
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -341,8 +341,6 @@ struct paravirt_patch_template pv_ops =
 	.cpu.iret		= native_iret,
 	.cpu.swapgs		= native_swapgs,
 
-	.cpu.set_iopl_mask	= native_set_iopl_mask,
-
 	.cpu.start_context_switch	= paravirt_nop,
 	.cpu.end_context_switch		= paravirt_nop,
 
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -187,15 +187,6 @@ EXPORT_SYMBOL_GPL(start_thread);
 	 */
 	load_TLS(next, cpu);
 
-	/*
-	 * Restore IOPL if needed.  In normal use, the flags restore
-	 * in the switch assembly will handle this.  But if the kernel
-	 * is running virtualized at a non-zero CPL, the popf will
-	 * not restore flags, so it must be done in a separate step.
-	 */
-	if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
-		set_iopl_mask(next->iopl);
-
 	switch_to_extra(prev_p, next_p);
 
 	/*
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -497,17 +497,6 @@ void compat_start_thread(struct pt_regs
 
 	switch_to_extra(prev_p, next_p);
 
-#ifdef CONFIG_XEN_PV
-	/*
-	 * On Xen PV, IOPL bits in pt_regs->flags have no effect, and
-	 * current_pt_regs()->flags may not match the current task's
-	 * intended IOPL.  We need to switch it manually.
-	 */
-	if (unlikely(static_cpu_has(X86_FEATURE_XENPV) &&
-		     prev->iopl != next->iopl))
-		xen_set_iopl_mask(next->iopl);
-#endif
-
 	if (static_cpu_has_bug(X86_BUG_SYSRET_SS_ATTRS)) {
 		/*
 		 * AMD CPUs have a misfeature: SYSRET sets the SS selector but
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -837,15 +837,6 @@ static void xen_load_sp0(unsigned long s
 	this_cpu_write(cpu_tss_rw.x86_tss.sp0, sp0);
 }
 
-void xen_set_iopl_mask(unsigned mask)
-{
-	struct physdev_set_iopl set_iopl;
-
-	/* Force the change at ring 0. */
-	set_iopl.iopl = (mask == 0) ? 1 : (mask >> 12) & 3;
-	HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
-}
-
 static void xen_io_delay(void)
 {
 }
@@ -1055,7 +1046,6 @@ static const struct pv_cpu_ops xen_cpu_o
 	.write_idt_entry = xen_write_idt_entry,
 	.load_sp0 = xen_load_sp0,
 
-	.set_iopl_mask = xen_set_iopl_mask,
 	.io_delay = xen_io_delay,
 
 	/* Xen takes care of %gs when switching to usermode for us */

[tip: x86/iopl] x86/iopl: Remove legacy IOPL option

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     5650e933f0fcc7f76c13878eb944c04bcf1fda32
Gitweb:        https://git.kernel.org/tip/5650e933f0fcc7f76c13878eb944c04bcf1fda32
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:58 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:07 +01:00

x86/iopl: Remove legacy IOPL option

The IOPL emulation via the I/O bitmap is sufficient. Remove the legacy
cruft dealing with the (e)flags based IOPL mechanism.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Juergen Gross <jgross@suse.com> (Paravirt and Xen parts)
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210105.461938850@linutronix.de


---
 arch/x86/Kconfig                      | 23 +------------
 arch/x86/include/asm/paravirt.h       |  4 +--
 arch/x86/include/asm/paravirt_types.h |  2 +-
 arch/x86/include/asm/processor.h      | 26 +-------------
 arch/x86/include/asm/xen/hypervisor.h |  2 +-
 arch/x86/kernel/ioport.c              | 47 ++++++--------------------
 arch/x86/kernel/paravirt.c            |  2 +-
 arch/x86/kernel/process_32.c          |  9 +-----
 arch/x86/kernel/process_64.c          | 11 +------
 arch/x86/xen/enlighten_pv.c           | 10 +------
 10 files changed, 17 insertions(+), 119 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2aad1cd..1f926e3 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1254,12 +1254,9 @@ config X86_VSYSCALL_EMULATION
 	 Disabling this option saves about 7K of kernel size and
 	 possibly 4K of additional runtime pagetable memory.
 
-choice
-	prompt "IOPL"
-	default X86_IOPL_EMULATION
-
 config X86_IOPL_EMULATION
 	bool "IOPL Emulation"
+	default y
 	---help---
 	  Legacy IOPL support is an overbroad mechanism which allows user
 	  space aside of accessing all 65536 I/O ports also to disable
@@ -1269,22 +1266,8 @@ config X86_IOPL_EMULATION
 
 	  The emulation restricts the functionality of the syscall to
 	  only allowing the full range I/O port access, but prevents the
-	  ability to disable interrupts from user space.
-
-config X86_IOPL_LEGACY
-	bool "IOPL Legacy"
-	---help---
-	Allow the full IOPL permissions, i.e. user space access to all
-	65536 I/O ports and also the ability to disable interrupts, which
-	is overbroad and can result in system lockups.
-
-config X86_IOPL_NONE
-	bool "IOPL None"
-	---help---
-	Disable the IOPL permission syscall. That's the safest option as
-	no sane application should depend on this functionality.
-
-endchoice
+	  ability to disable interrupts from user space which would be
+	  granted if the hardware IOPL mechanism would be used.
 
 config TOSHIBA
 	tristate "Toshiba Laptop support"
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 69089d4..86e7317 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -294,10 +294,6 @@ static inline void write_idt_entry(gate_desc *dt, int entry, const gate_desc *g)
 {
 	PVOP_VCALL3(cpu.write_idt_entry, dt, entry, g);
 }
-static inline void set_iopl_mask(unsigned mask)
-{
-	PVOP_VCALL1(cpu.set_iopl_mask, mask);
-}
 
 static inline void paravirt_activate_mm(struct mm_struct *prev,
 					struct mm_struct *next)
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 70b654f..8481296 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -140,8 +140,6 @@ struct pv_cpu_ops {
 
 	void (*load_sp0)(unsigned long sp0);
 
-	void (*set_iopl_mask)(unsigned mask);
-
 	void (*wbinvd)(void);
 
 	/* cpuid emulation, mostly so that caps bits can be disabled */
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index b0e02aa..1387d31 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -516,10 +516,10 @@ struct thread_struct {
 	struct io_bitmap	*io_bitmap;
 
 	/*
-	 * IOPL. Priviledge level dependent I/O permission which includes
-	 * user space CLI/STI when granted.
+	 * IOPL. Priviledge level dependent I/O permission which is
+	 * emulated via the I/O bitmap to prevent user space from disabling
+	 * interrupts.
 	 */
-	unsigned long		iopl;
 	unsigned long		iopl_emul;
 
 	mm_segment_t		addr_limit;
@@ -552,25 +552,6 @@ static inline void arch_thread_struct_whitelist(unsigned long *offset,
  */
 #define TS_COMPAT		0x0002	/* 32bit syscall active (64BIT)*/
 
-/*
- * Set IOPL bits in EFLAGS from given mask
- */
-static inline void native_set_iopl_mask(unsigned mask)
-{
-#ifdef CONFIG_X86_32
-	unsigned int reg;
-
-	asm volatile ("pushfl;"
-		      "popl %0;"
-		      "andl %1, %0;"
-		      "orl %2, %0;"
-		      "pushl %0;"
-		      "popfl"
-		      : "=&r" (reg)
-		      : "i" (~X86_EFLAGS_IOPL), "r" (mask));
-#endif
-}
-
 static inline void
 native_load_sp0(unsigned long sp0)
 {
@@ -610,7 +591,6 @@ static inline void load_sp0(unsigned long sp0)
 	native_load_sp0(sp0);
 }
 
-#define set_iopl_mask native_set_iopl_mask
 #endif /* CONFIG_PARAVIRT_XXL */
 
 /* Free all resources held by a thread. */
diff --git a/arch/x86/include/asm/xen/hypervisor.h b/arch/x86/include/asm/xen/hypervisor.h
index 42e1245..ff4b52e 100644
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -62,6 +62,4 @@ void xen_arch_register_cpu(int num);
 void xen_arch_unregister_cpu(int num);
 #endif
 
-extern void xen_set_iopl_mask(unsigned mask);
-
 #endif /* _ASM_X86_XEN_HYPERVISOR_H */
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 9ed9458..d5dcde9 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -153,28 +153,23 @@ SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
 
 /*
  * The sys_iopl functionality depends on the level argument, which if
- * granted for the task is used by the CPU to check I/O instruction and
- * CLI/STI against the current priviledge level (CPL). If CPL is less than
- * or equal the tasks IOPL level the instructions take effect. If not a #GP
- * is raised. The default IOPL is 0, i.e. no permissions.
+ * granted for the task is used to enable access to all 65536 I/O ports.
  *
- * Setting IOPL to level 0-2 is disabling the userspace access. Only level
- * 3 enables it. If set it allows the user space thread:
+ * This does not use the IOPL mechanism provided by the CPU as that would
+ * also allow the user space task to use the CLI/STI instructions.
  *
- * - Unrestricted access to all 65535 I/O ports
- * - The usage of CLI/STI instructions
+ * Disabling interrupts in a user space task is dangerous as it might lock
+ * up the machine and the semantics vs. syscalls and exceptions is
+ * undefined.
  *
- * The advantage over ioperm is that the context switch does not require to
- * update the I/O bitmap which is especially true when a large number of
- * ports is accessed. But the allowance of CLI/STI in userspace is
- * considered a major problem.
+ * Setting IOPL to level 0-2 is disabling I/O permissions. Level 3
+ * 3 enables them.
  *
  * IOPL is strictly per thread and inherited on fork.
  */
 SYSCALL_DEFINE1(iopl, unsigned int, level)
 {
 	struct thread_struct *t = &current->thread;
-	struct pt_regs *regs = current_pt_regs();
 	unsigned int old;
 
 	/*
@@ -187,10 +182,7 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
 	if (level > 3)
 		return -EINVAL;
 
-	if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION))
-		old = t->iopl_emul;
-	else
-		old = t->iopl >> X86_EFLAGS_IOPL_BIT;
+	old = t->iopl_emul;
 
 	/* No point in going further if nothing changes */
 	if (level == old)
@@ -203,25 +195,8 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
 			return -EPERM;
 	}
 
-	if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION)) {
-		t->iopl_emul = level;
-		task_update_io_bitmap();
-	} else {
-		/*
-		 * Change the flags value on the return stack, which has
-		 * been set up on system-call entry. See also the fork and
-		 * signal handling code how this is handled.
-		 */
-		regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
-			(level << X86_EFLAGS_IOPL_BIT);
-		/* Store the new level in the thread struct */
-		t->iopl = level << X86_EFLAGS_IOPL_BIT;
-		/*
-		 * X86_32 switches immediately and XEN handles it via
-		 * emulation.
-		 */
-		set_iopl_mask(t->iopl);
-	}
+	t->iopl_emul = level;
+	task_update_io_bitmap();
 
 	return 0;
 }
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 59d3d27..789f5e4 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -341,8 +341,6 @@ struct paravirt_patch_template pv_ops = {
 	.cpu.iret		= native_iret,
 	.cpu.swapgs		= native_swapgs,
 
-	.cpu.set_iopl_mask	= native_set_iopl_mask,
-
 	.cpu.start_context_switch	= paravirt_nop,
 	.cpu.end_context_switch		= paravirt_nop,
 
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 6c7d905..323499f 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -187,15 +187,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	 */
 	load_TLS(next, cpu);
 
-	/*
-	 * Restore IOPL if needed.  In normal use, the flags restore
-	 * in the switch assembly will handle this.  But if the kernel
-	 * is running virtualized at a non-zero CPL, the popf will
-	 * not restore flags, so it must be done in a separate step.
-	 */
-	if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
-		set_iopl_mask(next->iopl);
-
 	switch_to_extra(prev_p, next_p);
 
 	/*
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index e93a1b8..506d668 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -497,17 +497,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 
 	switch_to_extra(prev_p, next_p);
 
-#ifdef CONFIG_XEN_PV
-	/*
-	 * On Xen PV, IOPL bits in pt_regs->flags have no effect, and
-	 * current_pt_regs()->flags may not match the current task's
-	 * intended IOPL.  We need to switch it manually.
-	 */
-	if (unlikely(static_cpu_has(X86_FEATURE_XENPV) &&
-		     prev->iopl != next->iopl))
-		xen_set_iopl_mask(next->iopl);
-#endif
-
 	if (static_cpu_has_bug(X86_BUG_SYSRET_SS_ATTRS)) {
 		/*
 		 * AMD CPUs have a misfeature: SYSRET sets the SS selector but
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 5bfea37..ae4a41c 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -837,15 +837,6 @@ static void xen_load_sp0(unsigned long sp0)
 	this_cpu_write(cpu_tss_rw.x86_tss.sp0, sp0);
 }
 
-void xen_set_iopl_mask(unsigned mask)
-{
-	struct physdev_set_iopl set_iopl;
-
-	/* Force the change at ring 0. */
-	set_iopl.iopl = (mask == 0) ? 1 : (mask >> 12) & 3;
-	HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
-}
-
 static void xen_io_delay(void)
 {
 }
@@ -1055,7 +1046,6 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
 	.write_idt_entry = xen_write_idt_entry,
 	.load_sp0 = xen_load_sp0,
 
-	.set_iopl_mask = xen_set_iopl_mask,
 	.io_delay = xen_io_delay,
 
 	/* Xen takes care of %gs when switching to usermode for us */

[patch V3 19/20] x86/ioperm: Extend IOPL config to control ioperm() as well

[Thomas Gleixner]

If iopl() is disabled, then providing ioperm() does not make much sense.

Rename the config option and disable/enable both syscalls with it. Guard
the code with #ifdefs where appropriate.

Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V3: New patch
---
 arch/x86/Kconfig                   |    7 +++++--
 arch/x86/include/asm/io_bitmap.h   |    6 ++++++
 arch/x86/include/asm/processor.h   |    9 ++++++++-
 arch/x86/include/asm/thread_info.h |    7 ++++++-
 arch/x86/kernel/cpu/common.c       |   26 +++++++++++++++++---------
 arch/x86/kernel/ioport.c           |   26 +++++++++++++++++++-------
 arch/x86/kernel/process.c          |    4 ++++
 7 files changed, 65 insertions(+), 20 deletions(-)

--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1254,10 +1254,13 @@ config X86_VSYSCALL_EMULATION
 	 Disabling this option saves about 7K of kernel size and
 	 possibly 4K of additional runtime pagetable memory.
 
-config X86_IOPL_EMULATION
-	bool "IOPL Emulation"
+config X86_IOPL_IOPERM
+	bool "IOPERM and IOPL Emulation"
 	default y
 	---help---
+	  This enables the ioperm() and iopl() syscalls which are necessary
+	  for legacy applications.
+
 	  Legacy IOPL support is an overbroad mechanism which allows user
 	  space aside of accessing all 65536 I/O ports also to disable
 	  interrupts. To gain this access the caller needs CAP_SYS_RAWIO
--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -15,9 +15,15 @@ struct io_bitmap {
 
 struct task_struct;
 
+#ifdef CONFIG_X86_IOPL_IOPERM
 void io_bitmap_share(struct task_struct *tsk);
 void io_bitmap_exit(void);
 
 void tss_update_io_bitmap(void);
+#else
+static inline void io_bitmap_share(struct task_struct *tsk) { }
+static inline void io_bitmap_exit(void) { }
+static inline void tss_update_io_bitmap(void) { }
+#endif
 
 #endif
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -340,13 +340,18 @@ struct x86_hw_tss {
 	(offsetof(struct tss_struct, io_bitmap.mapall) -	\
 	 offsetof(struct tss_struct, x86_tss))
 
+#ifdef CONFIG_X86_IOPL_IOPERM
 /*
  * sizeof(unsigned long) coming from an extra "long" at the end of the
  * iobitmap. The limit is inclusive, i.e. the last valid byte.
  */
-#define __KERNEL_TSS_LIMIT	\
+# define __KERNEL_TSS_LIMIT	\
 	(IO_BITMAP_OFFSET_VALID_ALL + IO_BITMAP_BYTES + \
 	 sizeof(unsigned long) - 1)
+#else
+# define __KERNEL_TSS_LIMIT	\
+	(offsetof(struct tss_struct, x86_tss) + sizeof(struct x86_hw_tss) - 1)
+#endif
 
 /* Base offset outside of TSS_LIMIT so unpriviledged IO causes #GP */
 #define IO_BITMAP_OFFSET_INVALID	(__KERNEL_TSS_LIMIT + 1)
@@ -398,7 +403,9 @@ struct tss_struct {
 	 */
 	struct x86_hw_tss	x86_tss;
 
+#ifdef CONFIG_X86_IOPL_IOPERM
 	struct x86_io_bitmap	io_bitmap;
+#endif
 } __aligned(PAGE_SIZE);
 
 DECLARE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw);
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -156,8 +156,13 @@ struct thread_info {
 # define _TIF_WORK_CTXSW	(_TIF_WORK_CTXSW_BASE)
 #endif
 
-#define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY | \
+#ifdef CONFIG_X86_IOPL_IOPERM
+# define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY | \
 				 _TIF_IO_BITMAP)
+#else
+# define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY)
+#endif
+
 #define _TIF_WORK_CTXSW_NEXT	(_TIF_WORK_CTXSW)
 
 #define STACK_WARN		(THREAD_SIZE/8)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1804,6 +1804,22 @@ static inline void gdt_setup_doublefault
 }
 #endif /* !CONFIG_X86_64 */
 
+static inline void tss_setup_io_bitmap(struct tss_struct *tss)
+{
+	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
+
+#ifdef CONFIG_X86_IOPL_IOPERM
+	tss->io_bitmap.prev_max = 0;
+	tss->io_bitmap.prev_sequence = 0;
+	memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
+	/*
+	 * Invalidate the extra array entry past the end of the all
+	 * permission bitmap as required by the hardware.
+	 */
+	tss->io_bitmap.mapall[IO_BITMAP_LONGS] = ~0UL;
+#endif
+}
+
 /*
  * cpu_init() initializes state that is per-CPU. Some data is already
  * initialized (naturally) in the bootstrap process, such as the GDT
@@ -1860,15 +1876,7 @@ void cpu_init(void)
 
 	/* Initialize the TSS. */
 	tss_setup_ist(tss);
-	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
-	tss->io_bitmap.prev_max = 0;
-	tss->io_bitmap.prev_sequence = 0;
-	memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
-	/*
-	 * Invalidate the extra array entry past the end of the all
-	 * permission bitmap as required by the hardware.
-	 */
-	tss->io_bitmap.mapall[IO_BITMAP_LONGS] = ~0UL;
+	tss_setup_io_bitmap(tss);
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
 	load_TR_desc();
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -14,6 +14,8 @@
 #include <asm/io_bitmap.h>
 #include <asm/desc.h>
 
+#ifdef CONFIG_X86_IOPL_IOPERM
+
 static atomic64_t io_bitmap_sequence;
 
 void io_bitmap_share(struct task_struct *tsk)
@@ -172,13 +174,6 @@ SYSCALL_DEFINE1(iopl, unsigned int, leve
 	struct thread_struct *t = &current->thread;
 	unsigned int old;
 
-	/*
-	 * Careful: the IOPL bits in regs->flags are undefined under Xen PV
-	 * and changing them has no effect.
-	 */
-	if (IS_ENABLED(CONFIG_X86_IOPL_NONE))
-		return -ENOSYS;
-
 	if (level > 3)
 		return -EINVAL;
 
@@ -200,3 +195,20 @@ SYSCALL_DEFINE1(iopl, unsigned int, leve
 
 	return 0;
 }
+
+#else /* CONFIG_X86_IOPL_IOPERM */
+
+long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
+{
+	return -ENOSYS;
+}
+SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
+{
+	return -ENOSYS;
+}
+
+SYSCALL_DEFINE1(iopl, unsigned int, level)
+{
+	return -ENOSYS;
+}
+#endif
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -316,6 +316,7 @@ void arch_setup_new_exec(void)
 	}
 }
 
+#ifdef CONFIG_X86_IOPL_IOPERM
 static inline void tss_invalidate_io_bitmap(struct tss_struct *tss)
 {
 	/*
@@ -403,6 +404,9 @@ void tss_update_io_bitmap(void)
 		tss_invalidate_io_bitmap(tss);
 	}
 }
+#else /* CONFIG_X86_IOPL_IOPERM */
+static inline void switch_to_bitmap(unsigned long tifp) { }
+#endif
 
 #ifdef CONFIG_SMP
 

[tip: x86/iopl] x86/ioperm: Extend IOPL config to control ioperm() as well

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     845fa6a960f45e07ab22b660bee7f7644dd29610
Gitweb:        https://git.kernel.org/tip/845fa6a960f45e07ab22b660bee7f7644dd29610
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:59 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:08 +01:00

x86/ioperm: Extend IOPL config to control ioperm() as well

If iopl() is disabled, then providing ioperm() does not make much sense.

Rename the config option and disable/enable both syscalls with it. Guard
the code with #ifdefs where appropriate.

Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210105.557339819@linutronix.de

---
 arch/x86/Kconfig                   |  7 +++++--
 arch/x86/include/asm/io_bitmap.h   |  6 ++++++
 arch/x86/include/asm/processor.h   |  9 ++++++++-
 arch/x86/include/asm/thread_info.h |  7 ++++++-
 arch/x86/kernel/cpu/common.c       | 26 +++++++++++++++++---------
 arch/x86/kernel/ioport.c           | 26 +++++++++++++++++++-------
 arch/x86/kernel/process.c          |  4 ++++
 7 files changed, 65 insertions(+), 20 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1f926e3..b162ce1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1254,10 +1254,13 @@ config X86_VSYSCALL_EMULATION
 	 Disabling this option saves about 7K of kernel size and
 	 possibly 4K of additional runtime pagetable memory.
 
-config X86_IOPL_EMULATION
-	bool "IOPL Emulation"
+config X86_IOPL_IOPERM
+	bool "IOPERM and IOPL Emulation"
 	default y
 	---help---
+	  This enables the ioperm() and iopl() syscalls which are necessary
+	  for legacy applications.
+
 	  Legacy IOPL support is an overbroad mechanism which allows user
 	  space aside of accessing all 65536 I/O ports also to disable
 	  interrupts. To gain this access the caller needs CAP_SYS_RAWIO
diff --git a/arch/x86/include/asm/io_bitmap.h b/arch/x86/include/asm/io_bitmap.h
index b664baa..02c6ef8 100644
--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -15,9 +15,15 @@ struct io_bitmap {
 
 struct task_struct;
 
+#ifdef CONFIG_X86_IOPL_IOPERM
 void io_bitmap_share(struct task_struct *tsk);
 void io_bitmap_exit(void);
 
 void tss_update_io_bitmap(void);
+#else
+static inline void io_bitmap_share(struct task_struct *tsk) { }
+static inline void io_bitmap_exit(void) { }
+static inline void tss_update_io_bitmap(void) { }
+#endif
 
 #endif
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 1387d31..45f416a 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -340,13 +340,18 @@ struct x86_hw_tss {
 	(offsetof(struct tss_struct, io_bitmap.mapall) -	\
 	 offsetof(struct tss_struct, x86_tss))
 
+#ifdef CONFIG_X86_IOPL_IOPERM
 /*
  * sizeof(unsigned long) coming from an extra "long" at the end of the
  * iobitmap. The limit is inclusive, i.e. the last valid byte.
  */
-#define __KERNEL_TSS_LIMIT	\
+# define __KERNEL_TSS_LIMIT	\
 	(IO_BITMAP_OFFSET_VALID_ALL + IO_BITMAP_BYTES + \
 	 sizeof(unsigned long) - 1)
+#else
+# define __KERNEL_TSS_LIMIT	\
+	(offsetof(struct tss_struct, x86_tss) + sizeof(struct x86_hw_tss) - 1)
+#endif
 
 /* Base offset outside of TSS_LIMIT so unpriviledged IO causes #GP */
 #define IO_BITMAP_OFFSET_INVALID	(__KERNEL_TSS_LIMIT + 1)
@@ -398,7 +403,9 @@ struct tss_struct {
 	 */
 	struct x86_hw_tss	x86_tss;
 
+#ifdef CONFIG_X86_IOPL_IOPERM
 	struct x86_io_bitmap	io_bitmap;
+#endif
 } __aligned(PAGE_SIZE);
 
 DECLARE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw);
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 0accf44..d779366 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -156,8 +156,13 @@ struct thread_info {
 # define _TIF_WORK_CTXSW	(_TIF_WORK_CTXSW_BASE)
 #endif
 
-#define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY | \
+#ifdef CONFIG_X86_IOPL_IOPERM
+# define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY | \
 				 _TIF_IO_BITMAP)
+#else
+# define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY)
+#endif
+
 #define _TIF_WORK_CTXSW_NEXT	(_TIF_WORK_CTXSW)
 
 #define STACK_WARN		(THREAD_SIZE/8)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 7bf402b..6f6ca6b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1804,6 +1804,22 @@ static inline void gdt_setup_doublefault_tss(int cpu)
 }
 #endif /* !CONFIG_X86_64 */
 
+static inline void tss_setup_io_bitmap(struct tss_struct *tss)
+{
+	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
+
+#ifdef CONFIG_X86_IOPL_IOPERM
+	tss->io_bitmap.prev_max = 0;
+	tss->io_bitmap.prev_sequence = 0;
+	memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
+	/*
+	 * Invalidate the extra array entry past the end of the all
+	 * permission bitmap as required by the hardware.
+	 */
+	tss->io_bitmap.mapall[IO_BITMAP_LONGS] = ~0UL;
+#endif
+}
+
 /*
  * cpu_init() initializes state that is per-CPU. Some data is already
  * initialized (naturally) in the bootstrap process, such as the GDT
@@ -1860,15 +1876,7 @@ void cpu_init(void)
 
 	/* Initialize the TSS. */
 	tss_setup_ist(tss);
-	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
-	tss->io_bitmap.prev_max = 0;
-	tss->io_bitmap.prev_sequence = 0;
-	memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
-	/*
-	 * Invalidate the extra array entry past the end of the all
-	 * permission bitmap as required by the hardware.
-	 */
-	tss->io_bitmap.mapall[IO_BITMAP_LONGS] = ~0UL;
+	tss_setup_io_bitmap(tss);
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
 	load_TR_desc();
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index d5dcde9..8abeee0 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -14,6 +14,8 @@
 #include <asm/io_bitmap.h>
 #include <asm/desc.h>
 
+#ifdef CONFIG_X86_IOPL_IOPERM
+
 static atomic64_t io_bitmap_sequence;
 
 void io_bitmap_share(struct task_struct *tsk)
@@ -172,13 +174,6 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
 	struct thread_struct *t = &current->thread;
 	unsigned int old;
 
-	/*
-	 * Careful: the IOPL bits in regs->flags are undefined under Xen PV
-	 * and changing them has no effect.
-	 */
-	if (IS_ENABLED(CONFIG_X86_IOPL_NONE))
-		return -ENOSYS;
-
 	if (level > 3)
 		return -EINVAL;
 
@@ -200,3 +195,20 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
 
 	return 0;
 }
+
+#else /* CONFIG_X86_IOPL_IOPERM */
+
+long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
+{
+	return -ENOSYS;
+}
+SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
+{
+	return -ENOSYS;
+}
+
+SYSCALL_DEFINE1(iopl, unsigned int, level)
+{
+	return -ENOSYS;
+}
+#endif
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 8ba2707..77a7d8f 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -316,6 +316,7 @@ void arch_setup_new_exec(void)
 	}
 }
 
+#ifdef CONFIG_X86_IOPL_IOPERM
 static inline void tss_invalidate_io_bitmap(struct tss_struct *tss)
 {
 	/*
@@ -403,6 +404,9 @@ void tss_update_io_bitmap(void)
 		tss_invalidate_io_bitmap(tss);
 	}
 }
+#else /* CONFIG_X86_IOPL_IOPERM */
+static inline void switch_to_bitmap(unsigned long tifp) { }
+#endif
 
 #ifdef CONFIG_SMP
 

[patch V3 20/20] selftests/x86/iopl: Extend test to cover IOPL emulation

[Thomas Gleixner]

From: Thomas Gleixner <tglx@linutronix.de>

Add tests that the now emulated iopl() functionality:

    - does not longer allow user space to disable interrupts.

    - does restore a I/O bitmap when IOPL is dropped

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>


---
 tools/testing/selftests/x86/iopl.c |  129 +++++++++++++++++++++++++++++++++----
 1 file changed, 118 insertions(+), 11 deletions(-)

--- a/tools/testing/selftests/x86/iopl.c
+++ b/tools/testing/selftests/x86/iopl.c
@@ -35,6 +35,16 @@ static void sethandler(int sig, void (*h
 
 }
 
+static void clearhandler(int sig)
+{
+	struct sigaction sa;
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = SIG_DFL;
+	sigemptyset(&sa.sa_mask);
+	if (sigaction(sig, &sa, 0))
+		err(1, "sigaction");
+}
+
 static jmp_buf jmpbuf;
 
 static void sigsegv(int sig, siginfo_t *si, void *ctx_void)
@@ -42,25 +52,128 @@ static void sigsegv(int sig, siginfo_t *
 	siglongjmp(jmpbuf, 1);
 }
 
+static bool try_outb(unsigned short port)
+{
+	sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
+	if (sigsetjmp(jmpbuf, 1) != 0) {
+		return false;
+	} else {
+		asm volatile ("outb %%al, %w[port]"
+			      : : [port] "Nd" (port), "a" (0));
+		return true;
+	}
+	clearhandler(SIGSEGV);
+}
+
+static void expect_ok_outb(unsigned short port)
+{
+	if (!try_outb(port)) {
+		printf("[FAIL]\toutb to 0x%02hx failed\n", port);
+		exit(1);
+	}
+
+	printf("[OK]\toutb to 0x%02hx worked\n", port);
+}
+
+static void expect_gp_outb(unsigned short port)
+{
+	if (try_outb(port)) {
+		printf("[FAIL]\toutb to 0x%02hx worked\n", port);
+		nerrs++;
+	}
+
+	printf("[OK]\toutb to 0x%02hx failed\n", port);
+}
+
+static bool try_cli(void)
+{
+	sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
+	if (sigsetjmp(jmpbuf, 1) != 0) {
+		return false;
+	} else {
+		asm volatile ("cli");
+		return true;
+	}
+	clearhandler(SIGSEGV);
+}
+
+static bool try_sti(void)
+{
+	sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
+	if (sigsetjmp(jmpbuf, 1) != 0) {
+		return false;
+	} else {
+		asm volatile ("sti");
+		return true;
+	}
+	clearhandler(SIGSEGV);
+}
+
+static void expect_gp_sti(void)
+{
+	if (try_sti()) {
+		printf("[FAIL]\tSTI worked\n");
+		nerrs++;
+	} else {
+		printf("[OK]\tSTI faulted\n");
+	}
+}
+
+static void expect_gp_cli(void)
+{
+	if (try_cli()) {
+		printf("[FAIL]\tCLI worked\n");
+		nerrs++;
+	} else {
+		printf("[OK]\tCLI faulted\n");
+	}
+}
+
 int main(void)
 {
 	cpu_set_t cpuset;
+
 	CPU_ZERO(&cpuset);
 	CPU_SET(0, &cpuset);
 	if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
 		err(1, "sched_setaffinity to CPU 0");
 
 	/* Probe for iopl support.  Note that iopl(0) works even as nonroot. */
-	if (iopl(3) != 0) {
+	switch(iopl(3)) {
+	case 0:
+		break;
+	case -ENOSYS:
+		printf("[OK]\tiopl() nor supported\n");
+		return 0;
+	default:
 		printf("[OK]\tiopl(3) failed (%d) -- try running as root\n",
 		       errno);
 		return 0;
 	}
 
-	/* Restore our original state prior to starting the test. */
+	/* Make sure that CLI/STI are blocked even with IOPL level 3 */
+	expect_gp_cli();
+	expect_gp_sti();
+	expect_ok_outb(0x80);
+
+	/* Establish an I/O bitmap to test the restore */
+	if (ioperm(0x80, 1, 1) != 0)
+		err(1, "ioperm(0x80, 1, 1) failed\n");
+
+	/* Restore our original state prior to starting the fork test. */
 	if (iopl(0) != 0)
 		err(1, "iopl(0)");
 
+	/*
+	 * Verify that IOPL emulation is disabled and the I/O bitmap still
+	 * works.
+	 */
+	expect_ok_outb(0x80);
+	expect_gp_outb(0xed);
+	/* Drop the I/O bitmap */
+	if (ioperm(0x80, 1, 0) != 0)
+		err(1, "ioperm(0x80, 1, 0) failed\n");
+
 	pid_t child = fork();
 	if (child == -1)
 		err(1, "fork");
@@ -90,14 +203,9 @@ int main(void)
 
 	printf("[RUN]\tparent: write to 0x80 (should fail)\n");
 
-	sethandler(SIGSEGV, sigsegv, 0);
-	if (sigsetjmp(jmpbuf, 1) != 0) {
-		printf("[OK]\twrite was denied\n");
-	} else {
-		asm volatile ("outb %%al, $0x80" : : "a" (0));
-		printf("[FAIL]\twrite was allowed\n");
-		nerrs++;
-	}
+	expect_gp_outb(0x80);
+	expect_gp_cli();
+	expect_gp_sti();
 
 	/* Test the capability checks. */
 	printf("\tiopl(3)\n");
@@ -133,4 +241,3 @@ int main(void)
 done:
 	return nerrs ? 1 : 0;
 }
-

[tip: x86/iopl] selftests/x86/iopl: Extend test to cover IOPL emulation

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     04f822767cb1387a277b96246e1f7f5f93fa35f0
Gitweb:        https://git.kernel.org/tip/04f822767cb1387a277b96246e1f7f5f93fa35f0
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:43:00 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:08 +01:00

selftests/x86/iopl: Extend test to cover IOPL emulation

Add tests that the now emulated iopl() functionality:

    - does not longer allow user space to disable interrupts.

    - does restore a I/O bitmap when IOPL is dropped

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210105.671132359@linutronix.de



---
 tools/testing/selftests/x86/iopl.c | 129 +++++++++++++++++++++++++---
 1 file changed, 118 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/x86/iopl.c b/tools/testing/selftests/x86/iopl.c
index 6aa27f3..bab2f6e 100644
--- a/tools/testing/selftests/x86/iopl.c
+++ b/tools/testing/selftests/x86/iopl.c
@@ -35,6 +35,16 @@ static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
 
 }
 
+static void clearhandler(int sig)
+{
+	struct sigaction sa;
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = SIG_DFL;
+	sigemptyset(&sa.sa_mask);
+	if (sigaction(sig, &sa, 0))
+		err(1, "sigaction");
+}
+
 static jmp_buf jmpbuf;
 
 static void sigsegv(int sig, siginfo_t *si, void *ctx_void)
@@ -42,25 +52,128 @@ static void sigsegv(int sig, siginfo_t *si, void *ctx_void)
 	siglongjmp(jmpbuf, 1);
 }
 
+static bool try_outb(unsigned short port)
+{
+	sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
+	if (sigsetjmp(jmpbuf, 1) != 0) {
+		return false;
+	} else {
+		asm volatile ("outb %%al, %w[port]"
+			      : : [port] "Nd" (port), "a" (0));
+		return true;
+	}
+	clearhandler(SIGSEGV);
+}
+
+static void expect_ok_outb(unsigned short port)
+{
+	if (!try_outb(port)) {
+		printf("[FAIL]\toutb to 0x%02hx failed\n", port);
+		exit(1);
+	}
+
+	printf("[OK]\toutb to 0x%02hx worked\n", port);
+}
+
+static void expect_gp_outb(unsigned short port)
+{
+	if (try_outb(port)) {
+		printf("[FAIL]\toutb to 0x%02hx worked\n", port);
+		nerrs++;
+	}
+
+	printf("[OK]\toutb to 0x%02hx failed\n", port);
+}
+
+static bool try_cli(void)
+{
+	sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
+	if (sigsetjmp(jmpbuf, 1) != 0) {
+		return false;
+	} else {
+		asm volatile ("cli");
+		return true;
+	}
+	clearhandler(SIGSEGV);
+}
+
+static bool try_sti(void)
+{
+	sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
+	if (sigsetjmp(jmpbuf, 1) != 0) {
+		return false;
+	} else {
+		asm volatile ("sti");
+		return true;
+	}
+	clearhandler(SIGSEGV);
+}
+
+static void expect_gp_sti(void)
+{
+	if (try_sti()) {
+		printf("[FAIL]\tSTI worked\n");
+		nerrs++;
+	} else {
+		printf("[OK]\tSTI faulted\n");
+	}
+}
+
+static void expect_gp_cli(void)
+{
+	if (try_cli()) {
+		printf("[FAIL]\tCLI worked\n");
+		nerrs++;
+	} else {
+		printf("[OK]\tCLI faulted\n");
+	}
+}
+
 int main(void)
 {
 	cpu_set_t cpuset;
+
 	CPU_ZERO(&cpuset);
 	CPU_SET(0, &cpuset);
 	if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
 		err(1, "sched_setaffinity to CPU 0");
 
 	/* Probe for iopl support.  Note that iopl(0) works even as nonroot. */
-	if (iopl(3) != 0) {
+	switch(iopl(3)) {
+	case 0:
+		break;
+	case -ENOSYS:
+		printf("[OK]\tiopl() nor supported\n");
+		return 0;
+	default:
 		printf("[OK]\tiopl(3) failed (%d) -- try running as root\n",
 		       errno);
 		return 0;
 	}
 
-	/* Restore our original state prior to starting the test. */
+	/* Make sure that CLI/STI are blocked even with IOPL level 3 */
+	expect_gp_cli();
+	expect_gp_sti();
+	expect_ok_outb(0x80);
+
+	/* Establish an I/O bitmap to test the restore */
+	if (ioperm(0x80, 1, 1) != 0)
+		err(1, "ioperm(0x80, 1, 1) failed\n");
+
+	/* Restore our original state prior to starting the fork test. */
 	if (iopl(0) != 0)
 		err(1, "iopl(0)");
 
+	/*
+	 * Verify that IOPL emulation is disabled and the I/O bitmap still
+	 * works.
+	 */
+	expect_ok_outb(0x80);
+	expect_gp_outb(0xed);
+	/* Drop the I/O bitmap */
+	if (ioperm(0x80, 1, 0) != 0)
+		err(1, "ioperm(0x80, 1, 0) failed\n");
+
 	pid_t child = fork();
 	if (child == -1)
 		err(1, "fork");
@@ -90,14 +203,9 @@ int main(void)
 
 	printf("[RUN]\tparent: write to 0x80 (should fail)\n");
 
-	sethandler(SIGSEGV, sigsegv, 0);
-	if (sigsetjmp(jmpbuf, 1) != 0) {
-		printf("[OK]\twrite was denied\n");
-	} else {
-		asm volatile ("outb %%al, $0x80" : : "a" (0));
-		printf("[FAIL]\twrite was allowed\n");
-		nerrs++;
-	}
+	expect_gp_outb(0x80);
+	expect_gp_cli();
+	expect_gp_sti();
 
 	/* Test the capability checks. */
 	printf("\tiopl(3)\n");
@@ -133,4 +241,3 @@ int main(void)
 done:
 	return nerrs ? 1 : 0;
 }
-

Re: [patch V3 00/20] x86/iopl: Prevent user space from using CLI/STI with iopl(3)

[Peter Zijlstra]

On Wed, Nov 13, 2019 at 09:42:40PM +0100, Thomas Gleixner wrote:

> iopl(level = 3) enables aside of access to all 65536 I/O ports also the
> usage of CLI/STI in user space.
> 
> Disabling interrupts in user space can lead to system lockups and breaks
> assumptions in the kernel that userspace always runs with interrupts
> enabled.
> 
> iopl() is often preferred over ioperm() as it avoids the overhead of
> copying the tasks I/O bitmap to the TSS bitmap on context switch. This
> overhead can be avoided by providing a all zeroes bitmap in the TSS and
> switching the TSS bitmap offset to this permit all IO bitmap. It's
> marginally slower than iopl() which is a one time setup, but prevents the
> usage of CLI/STI in user space.

> ---
>  arch/x86/Kconfig                        |   18 ++
>  arch/x86/entry/common.c                 |    4 
>  arch/x86/include/asm/io_bitmap.h        |   29 ++++
>  arch/x86/include/asm/paravirt.h         |    4 
>  arch/x86/include/asm/paravirt_types.h   |    2 
>  arch/x86/include/asm/pgtable_32_types.h |    2 
>  arch/x86/include/asm/processor.h        |  113 ++++++++++-------
>  arch/x86/include/asm/ptrace.h           |    6 
>  arch/x86/include/asm/switch_to.h        |   10 +
>  arch/x86/include/asm/thread_info.h      |   14 +-
>  arch/x86/include/asm/xen/hypervisor.h   |    2 
>  arch/x86/kernel/cpu/common.c            |  188 ++++++++++++----------------
>  arch/x86/kernel/doublefault.c           |    2 
>  arch/x86/kernel/ioport.c                |  209 +++++++++++++++++++++-----------
>  arch/x86/kernel/paravirt.c              |    2 
>  arch/x86/kernel/process.c               |  200 ++++++++++++++++++++++++------
>  arch/x86/kernel/process_32.c            |   77 -----------
>  arch/x86/kernel/process_64.c            |   86 -------------
>  arch/x86/kernel/ptrace.c                |   12 +
>  arch/x86/kvm/vmx/vmx.c                  |    8 -
>  arch/x86/mm/cpu_entry_area.c            |    8 +
>  arch/x86/xen/enlighten_pv.c             |   10 -
>  tools/testing/selftests/x86/ioperm.c    |   16 ++
>  tools/testing/selftests/x86/iopl.c      |  129 ++++++++++++++++++-
>  24 files changed, 674 insertions(+), 477 deletions(-)


Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

[tip: x86/iopl] x86/iopl: Remove legacy IOPL option

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     a24ca9976843156eabbc5f2d798954b5674d1b61
Gitweb:        https://git.kernel.org/tip/a24ca9976843156eabbc5f2d798954b5674d1b61
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Mon, 11 Nov 2019 23:03:29 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sat, 16 Nov 2019 11:24:05 +01:00

x86/iopl: Remove legacy IOPL option

The IOPL emulation via the I/O bitmap is sufficient. Remove the legacy
cruft dealing with the (e)flags based IOPL mechanism.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Juergen Gross <jgross@suse.com> (Paravirt and Xen parts)
Acked-by: Andy Lutomirski <luto@kernel.org>

---
 arch/x86/Kconfig                      | 23 +------------
 arch/x86/include/asm/paravirt.h       |  4 +--
 arch/x86/include/asm/paravirt_types.h |  2 +-
 arch/x86/include/asm/processor.h      | 26 +-------------
 arch/x86/include/asm/xen/hypervisor.h |  2 +-
 arch/x86/kernel/ioport.c              | 47 ++++++--------------------
 arch/x86/kernel/paravirt.c            |  2 +-
 arch/x86/kernel/process_32.c          |  9 +-----
 arch/x86/kernel/process_64.c          | 11 +------
 arch/x86/xen/enlighten_pv.c           | 10 +------
 10 files changed, 17 insertions(+), 119 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2aad1cd..1f926e3 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1254,12 +1254,9 @@ config X86_VSYSCALL_EMULATION
 	 Disabling this option saves about 7K of kernel size and
 	 possibly 4K of additional runtime pagetable memory.
 
-choice
-	prompt "IOPL"
-	default X86_IOPL_EMULATION
-
 config X86_IOPL_EMULATION
 	bool "IOPL Emulation"
+	default y
 	---help---
 	  Legacy IOPL support is an overbroad mechanism which allows user
 	  space aside of accessing all 65536 I/O ports also to disable
@@ -1269,22 +1266,8 @@ config X86_IOPL_EMULATION
 
 	  The emulation restricts the functionality of the syscall to
 	  only allowing the full range I/O port access, but prevents the
-	  ability to disable interrupts from user space.
-
-config X86_IOPL_LEGACY
-	bool "IOPL Legacy"
-	---help---
-	Allow the full IOPL permissions, i.e. user space access to all
-	65536 I/O ports and also the ability to disable interrupts, which
-	is overbroad and can result in system lockups.
-
-config X86_IOPL_NONE
-	bool "IOPL None"
-	---help---
-	Disable the IOPL permission syscall. That's the safest option as
-	no sane application should depend on this functionality.
-
-endchoice
+	  ability to disable interrupts from user space which would be
+	  granted if the hardware IOPL mechanism would be used.
 
 config TOSHIBA
 	tristate "Toshiba Laptop support"
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 69089d4..86e7317 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -294,10 +294,6 @@ static inline void write_idt_entry(gate_desc *dt, int entry, const gate_desc *g)
 {
 	PVOP_VCALL3(cpu.write_idt_entry, dt, entry, g);
 }
-static inline void set_iopl_mask(unsigned mask)
-{
-	PVOP_VCALL1(cpu.set_iopl_mask, mask);
-}
 
 static inline void paravirt_activate_mm(struct mm_struct *prev,
 					struct mm_struct *next)
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 70b654f..8481296 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -140,8 +140,6 @@ struct pv_cpu_ops {
 
 	void (*load_sp0)(unsigned long sp0);
 
-	void (*set_iopl_mask)(unsigned mask);
-
 	void (*wbinvd)(void);
 
 	/* cpuid emulation, mostly so that caps bits can be disabled */
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index b0e02aa..1387d31 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -516,10 +516,10 @@ struct thread_struct {
 	struct io_bitmap	*io_bitmap;
 
 	/*
-	 * IOPL. Priviledge level dependent I/O permission which includes
-	 * user space CLI/STI when granted.
+	 * IOPL. Priviledge level dependent I/O permission which is
+	 * emulated via the I/O bitmap to prevent user space from disabling
+	 * interrupts.
 	 */
-	unsigned long		iopl;
 	unsigned long		iopl_emul;
 
 	mm_segment_t		addr_limit;
@@ -552,25 +552,6 @@ static inline void arch_thread_struct_whitelist(unsigned long *offset,
  */
 #define TS_COMPAT		0x0002	/* 32bit syscall active (64BIT)*/
 
-/*
- * Set IOPL bits in EFLAGS from given mask
- */
-static inline void native_set_iopl_mask(unsigned mask)
-{
-#ifdef CONFIG_X86_32
-	unsigned int reg;
-
-	asm volatile ("pushfl;"
-		      "popl %0;"
-		      "andl %1, %0;"
-		      "orl %2, %0;"
-		      "pushl %0;"
-		      "popfl"
-		      : "=&r" (reg)
-		      : "i" (~X86_EFLAGS_IOPL), "r" (mask));
-#endif
-}
-
 static inline void
 native_load_sp0(unsigned long sp0)
 {
@@ -610,7 +591,6 @@ static inline void load_sp0(unsigned long sp0)
 	native_load_sp0(sp0);
 }
 
-#define set_iopl_mask native_set_iopl_mask
 #endif /* CONFIG_PARAVIRT_XXL */
 
 /* Free all resources held by a thread. */
diff --git a/arch/x86/include/asm/xen/hypervisor.h b/arch/x86/include/asm/xen/hypervisor.h
index 42e1245..ff4b52e 100644
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -62,6 +62,4 @@ void xen_arch_register_cpu(int num);
 void xen_arch_unregister_cpu(int num);
 #endif
 
-extern void xen_set_iopl_mask(unsigned mask);
-
 #endif /* _ASM_X86_XEN_HYPERVISOR_H */
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 9ed9458..d5dcde9 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -153,28 +153,23 @@ SYSCALL_DEFINE3(ioperm, unsigned long, from, unsigned long, num, int, turn_on)
 
 /*
  * The sys_iopl functionality depends on the level argument, which if
- * granted for the task is used by the CPU to check I/O instruction and
- * CLI/STI against the current priviledge level (CPL). If CPL is less than
- * or equal the tasks IOPL level the instructions take effect. If not a #GP
- * is raised. The default IOPL is 0, i.e. no permissions.
+ * granted for the task is used to enable access to all 65536 I/O ports.
  *
- * Setting IOPL to level 0-2 is disabling the userspace access. Only level
- * 3 enables it. If set it allows the user space thread:
+ * This does not use the IOPL mechanism provided by the CPU as that would
+ * also allow the user space task to use the CLI/STI instructions.
  *
- * - Unrestricted access to all 65535 I/O ports
- * - The usage of CLI/STI instructions
+ * Disabling interrupts in a user space task is dangerous as it might lock
+ * up the machine and the semantics vs. syscalls and exceptions is
+ * undefined.
  *
- * The advantage over ioperm is that the context switch does not require to
- * update the I/O bitmap which is especially true when a large number of
- * ports is accessed. But the allowance of CLI/STI in userspace is
- * considered a major problem.
+ * Setting IOPL to level 0-2 is disabling I/O permissions. Level 3
+ * 3 enables them.
  *
  * IOPL is strictly per thread and inherited on fork.
  */
 SYSCALL_DEFINE1(iopl, unsigned int, level)
 {
 	struct thread_struct *t = &current->thread;
-	struct pt_regs *regs = current_pt_regs();
 	unsigned int old;
 
 	/*
@@ -187,10 +182,7 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
 	if (level > 3)
 		return -EINVAL;
 
-	if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION))
-		old = t->iopl_emul;
-	else
-		old = t->iopl >> X86_EFLAGS_IOPL_BIT;
+	old = t->iopl_emul;
 
 	/* No point in going further if nothing changes */
 	if (level == old)
@@ -203,25 +195,8 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
 			return -EPERM;
 	}
 
-	if (IS_ENABLED(CONFIG_X86_IOPL_EMULATION)) {
-		t->iopl_emul = level;
-		task_update_io_bitmap();
-	} else {
-		/*
-		 * Change the flags value on the return stack, which has
-		 * been set up on system-call entry. See also the fork and
-		 * signal handling code how this is handled.
-		 */
-		regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
-			(level << X86_EFLAGS_IOPL_BIT);
-		/* Store the new level in the thread struct */
-		t->iopl = level << X86_EFLAGS_IOPL_BIT;
-		/*
-		 * X86_32 switches immediately and XEN handles it via
-		 * emulation.
-		 */
-		set_iopl_mask(t->iopl);
-	}
+	t->iopl_emul = level;
+	task_update_io_bitmap();
 
 	return 0;
 }
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 59d3d27..789f5e4 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -341,8 +341,6 @@ struct paravirt_patch_template pv_ops = {
 	.cpu.iret		= native_iret,
 	.cpu.swapgs		= native_swapgs,
 
-	.cpu.set_iopl_mask	= native_set_iopl_mask,
-
 	.cpu.start_context_switch	= paravirt_nop,
 	.cpu.end_context_switch		= paravirt_nop,
 
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 6c7d905..323499f 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -187,15 +187,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	 */
 	load_TLS(next, cpu);
 
-	/*
-	 * Restore IOPL if needed.  In normal use, the flags restore
-	 * in the switch assembly will handle this.  But if the kernel
-	 * is running virtualized at a non-zero CPL, the popf will
-	 * not restore flags, so it must be done in a separate step.
-	 */
-	if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
-		set_iopl_mask(next->iopl);
-
 	switch_to_extra(prev_p, next_p);
 
 	/*
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index e93a1b8..506d668 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -497,17 +497,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 
 	switch_to_extra(prev_p, next_p);
 
-#ifdef CONFIG_XEN_PV
-	/*
-	 * On Xen PV, IOPL bits in pt_regs->flags have no effect, and
-	 * current_pt_regs()->flags may not match the current task's
-	 * intended IOPL.  We need to switch it manually.
-	 */
-	if (unlikely(static_cpu_has(X86_FEATURE_XENPV) &&
-		     prev->iopl != next->iopl))
-		xen_set_iopl_mask(next->iopl);
-#endif
-
 	if (static_cpu_has_bug(X86_BUG_SYSRET_SS_ATTRS)) {
 		/*
 		 * AMD CPUs have a misfeature: SYSRET sets the SS selector but
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 5bfea37..ae4a41c 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -837,15 +837,6 @@ static void xen_load_sp0(unsigned long sp0)
 	this_cpu_write(cpu_tss_rw.x86_tss.sp0, sp0);
 }
 
-void xen_set_iopl_mask(unsigned mask)
-{
-	struct physdev_set_iopl set_iopl;
-
-	/* Force the change at ring 0. */
-	set_iopl.iopl = (mask == 0) ? 1 : (mask >> 12) & 3;
-	HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
-}
-
 static void xen_io_delay(void)
 {
 }
@@ -1055,7 +1046,6 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
 	.write_idt_entry = xen_write_idt_entry,
 	.load_sp0 = xen_load_sp0,
 
-	.set_iopl_mask = xen_set_iopl_mask,
 	.io_delay = xen_io_delay,
 
 	/* Xen takes care of %gs when switching to usermode for us */