[RFC 10/17] x86/asm/64: Pass sp0 directly to load_sp0()

From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org
Cc: linux-kernel@vger.kernel.org, Borislav Petkov <bp@alien8.de>,
	Brian Gerst <brgerst@gmail.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Juergen Gross <jgross@suse.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Kees Cook <keescook@chromium.org>,
	Andy Lutomirski <luto@kernel.org>
Subject: [RFC 10/17] x86/asm/64: Pass sp0 directly to load_sp0()
Date: Wed,  6 Sep 2017 14:36:55 -0700	[thread overview]
Message-ID: <66c53e714940bc07fa0165bdac6572796eb5c4a9.1504733277.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1504733277.git.luto@kernel.org>
In-Reply-To: <cover.1504733277.git.luto@kernel.org>

load_sp0() had an odd signature:

void load_sp0(struct tss_struct *tss, struct thread_struct *thread);

Simplify it to:

void load_sp0(unsigned long sp0);

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/paravirt.h       |  5 ++---
 arch/x86/include/asm/paravirt_types.h |  2 +-
 arch/x86/include/asm/processor.h      |  9 ++++-----
 arch/x86/kernel/cpu/common.c          |  4 ++--
 arch/x86/kernel/process_32.c          |  4 ++--
 arch/x86/kernel/process_64.c          |  2 +-
 arch/x86/kernel/vm86_32.c             | 12 ++++--------
 arch/x86/lguest/boot.c                |  7 +++----
 arch/x86/xen/enlighten_pv.c           |  7 +++----
 9 files changed, 22 insertions(+), 30 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 9ccac1926587..209dada6207e 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -15,10 +15,9 @@
 #include <linux/cpumask.h>
 #include <asm/frame.h>
 
-static inline void load_sp0(struct tss_struct *tss,
-			     struct thread_struct *thread)
+static inline void load_sp0(unsigned long sp0)
 {
-	PVOP_VCALL2(pv_cpu_ops.load_sp0, tss, thread);
+	PVOP_VCALL1(pv_cpu_ops.load_sp0, sp0);
 }
 
 /* The paravirtualized CPUID instruction. */
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 9ffc36bfe4cd..04a091615c08 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -136,7 +136,7 @@ struct pv_cpu_ops {
 	void (*alloc_ldt)(struct desc_struct *ldt, unsigned entries);
 	void (*free_ldt)(struct desc_struct *ldt, unsigned entries);
 
-	void (*load_sp0)(struct tss_struct *tss, struct thread_struct *t);
+	void (*load_sp0)(unsigned long sp0);
 
 	void (*set_iopl_mask)(unsigned mask);
 
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index ee37fb86900a..85ddfc1a9bb5 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -510,9 +510,9 @@ static inline void native_set_iopl_mask(unsigned mask)
 }
 
 static inline void
-native_load_sp0(struct tss_struct *tss, struct thread_struct *thread)
+native_load_sp0(unsigned long sp0)
 {
-	tss->x86_tss.sp0 = thread->sp0;
+	this_cpu_write(cpu_tss.x86_tss.sp0, sp0);
 }
 
 static inline void native_swapgs(void)
@@ -537,10 +537,9 @@ static inline unsigned long current_top_of_stack(void)
 #else
 #define __cpuid			native_cpuid
 
-static inline void load_sp0(struct tss_struct *tss,
-			    struct thread_struct *thread)
+static inline void load_sp0(unsigned long sp0)
 {
-	native_load_sp0(tss, thread);
+	native_load_sp0(sp0);
 }
 
 #define set_iopl_mask native_set_iopl_mask
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index c8b39870f33e..40312b3ef9de 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1554,7 +1554,7 @@ void cpu_init(void)
 	BUG_ON(me->mm);
 	enter_lazy_tlb(&init_mm, me);
 
-	load_sp0(t, &current->thread);
+	load_sp0(current->thread.sp0);
 	set_tss_desc(cpu, t);
 	load_TR_desc();
 	load_mm_ldt(&init_mm);
@@ -1608,7 +1608,7 @@ void cpu_init(void)
 	BUG_ON(curr->mm);
 	enter_lazy_tlb(&init_mm, curr);
 
-	load_sp0(t, thread);
+	load_sp0(thread->sp0);
 	set_tss_desc(cpu, t);
 	load_TR_desc();
 	load_mm_ldt(&init_mm);
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 9f217b5ef438..e06a98e3a772 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -286,8 +286,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	 * Reload esp0 and cpu_current_top_of_stack.  This changes
 	 * current_thread_info().
 	 */
-	load_sp0(tss, next);
-	refresh_sysenter_cs();  /* in case prev or next is vm86 */
+	load_sp0(next->sp0);
+	refresh_sysenter_cs(next);  /* in case prev or next is vm86 */
 	this_cpu_write(cpu_current_top_of_stack,
 		       (unsigned long)task_stack_page(next_p) +
 		       THREAD_SIZE);
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 985e7569ab57..06c4393b19b3 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -437,7 +437,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	this_cpu_write(current_task, next_p);
 
 	/* Reload sp0. */
-	load_sp0(tss, next);
+	load_sp0(next->sp0);
 
 	/*
 	 * Now maybe reload the debug registers and handle I/O bitmaps
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index 9edda73dcc90..3b98b7771f15 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -94,7 +94,6 @@
 
 void save_v86_state(struct kernel_vm86_regs *regs, int retval)
 {
-	struct tss_struct *tss;
 	struct task_struct *tsk = current;
 	struct vm86plus_struct __user *user;
 	struct vm86 *vm86 = current->thread.vm86;
@@ -146,11 +145,10 @@ void save_v86_state(struct kernel_vm86_regs *regs, int retval)
 		do_exit(SIGSEGV);
 	}
 
-	tss = &per_cpu(cpu_tss, get_cpu());
 	tsk->thread.sp0 = vm86->saved_sp0;
 	tsk->thread.sysenter_cs = __KERNEL_CS;
-	load_sp0(tss, &tsk->thread);
-	refresh_sysenter_cs();
+	load_sp0(tsk->thread.sp0);
+	refresh_sysenter_cs(&tsk->thread);
 	vm86->saved_sp0 = 0;
 	put_cpu();
 
@@ -238,7 +236,6 @@ SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
 
 static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
 {
-	struct tss_struct *tss;
 	struct task_struct *tsk = current;
 	struct vm86 *vm86 = tsk->thread.vm86;
 	struct kernel_vm86_regs vm86regs;
@@ -366,16 +363,15 @@ static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
 	vm86->saved_sp0 = tsk->thread.sp0;
 	lazy_save_gs(vm86->regs32.gs);
 
-	tss = &per_cpu(cpu_tss, get_cpu());
 	/* make room for real-mode segments */
 	tsk->thread.sp0 += 16;
 
 	if (static_cpu_has(X86_FEATURE_SEP)) {
 		tsk->thread.sysenter_cs = 0;
-		refresh_sysenter_cs();
+		refresh_sysenter_cs(&tsk->thread);
 	}
 
-	load_sp0(tss, &tsk->thread);
+	load_sp0(tsk->thread.sp0);
 	put_cpu();
 
 	if (vm86->flags & VM86_SCREEN_BITMAP)
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 99472698c931..07bb8e9a69ac 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1054,12 +1054,11 @@ static void lguest_time_init(void)
  * will not tolerate us trying to use that), the stack pointer, and the number
  * of pages in the stack.
  */
-static void lguest_load_sp0(struct tss_struct *tss,
-			    struct thread_struct *thread)
+static void lguest_load_sp0(unsigned long sp0)
 {
-	lazy_hcall3(LHCALL_SET_STACK, __KERNEL_DS | 0x1, thread->sp0,
+	lazy_hcall3(LHCALL_SET_STACK, __KERNEL_DS | 0x1, sp0,
 		   THREAD_SIZE / PAGE_SIZE);
-	tss->x86_tss.sp0 = thread->sp0;
+	this_cpu_write(cpu_tss.x86_tss.sp0, sp0);
 }
 
 /* Let's just say, I wouldn't do debugging under a Guest. */
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 811e4ddb3f37..6c803c3ee831 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -771,15 +771,14 @@ static void __init xen_write_gdt_entry_boot(struct desc_struct *dt, int entry,
 	}
 }
 
-static void xen_load_sp0(struct tss_struct *tss,
-			 struct thread_struct *thread)
+static void xen_load_sp0(unsigned long sp0)
 {
 	struct multicall_space mcs;
 
 	mcs = xen_mc_entry(0);
-	MULTI_stack_switch(mcs.mc, __KERNEL_DS, thread->sp0);
+	MULTI_stack_switch(mcs.mc, __KERNEL_DS, sp0);
 	xen_mc_issue(PARAVIRT_LAZY_CPU);
-	tss->x86_tss.sp0 = thread->sp0;
+	this_cpu_write(cpu_tss.x86_tss.sp0, sp0);
 }
 
 void xen_set_iopl_mask(unsigned mask)
-- 
2.13.5
