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* [patch 00/10] x86/entry: Consolidation - Part I
@ 2020-02-25 21:36 Thomas Gleixner
  2020-02-25 21:36 ` [patch 01/10] x86/entry/32: Add missing ASM_CLAC to general_protection entry Thomas Gleixner
                   ` (12 more replies)
  0 siblings, 13 replies; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-25 21:36 UTC (permalink / raw)
  To: LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann

Hi!

This is the first batch of a 73 patches series which consolidates the x86
entry code.

This work started off as a trivial 5 patches series moving the heavy
lifting of POSIX CPU timers out of interrupt context into thread/process
context. This discovered that KVM is lacking to handle pending work items
before entering guest mode and added the handling to the x86 KVM
code. Review requested to make this a generic infrastructure.

The next series grew to 25 patches implementing the generic infrastructure,
converting x86 (and as a POC ARM64) over, but it turned out that this was
slightly incomplete and still had some entanglement with the rest of the
x86 entry code as some of that functionality is shared between syscall and
interrupt entry/exit. And it also unearthed the nastyness of IOPL which got
already addressed in mainline.

This series addresses these issues in order to prepare for making the entry
from userspace and exit to userspace (and it's counterpart enter guest) a
generic infrastructure in order to restrict the necessary ASM work to the
bare minimum.

The series is split into 5 parts:

    - General cleanups and bugfixes

    - Consolidation of the syscall entry/exit code

    - Autogenerate simple exception/trap code and reduce the difference
      between 32 and 64 bit

    - Autogenerate complex exception/trap code and provide different entry
      points for #DB and #MC exceptions which allows to address the
      recently discovered RCU vs. world issues in a more structured way

    - Convert the device interrupt entry code to use the same mechanism as
      exceptions and traps and finally convert the system vectors over as
      well. The last step after all those cleanups is to move the return
      from exception/interrupt logic (user mode work, kernel preemption)
      completely from ASM into C-code, so the ASM code just has to take
      care about returning from the exception, which is horrible and
      convoluted enough already.

At the end the x86 entry code is ready to move the syscall parts out into
generic code and finally tackle the initial problem which started all of
this.

The complete series is available from git:

   git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git x86/entry

which contains all 73 patches. The individual parts are tagged, so this
part can be retrieved via:

   git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git entry-v1-part1

Thanks,

	tglx

8<---------------
 entry/entry_32.S          |   19 +++++++------------
 include/asm/irq.h         |    2 +-
 include/asm/mce.h         |    3 ---
 include/asm/traps.h       |   17 +++++++----------
 kernel/cpu/mce/core.c     |   12 ++++++++++--
 kernel/cpu/mce/internal.h |    3 +++
 kernel/irq.c              |    3 +--
 kernel/traps.c            |   41 ++++++++++++++++++++++++++++++++++-------
 8 files changed, 63 insertions(+), 37 deletions(-)

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [patch 01/10] x86/entry/32: Add missing ASM_CLAC to general_protection entry
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
@ 2020-02-25 21:36 ` Thomas Gleixner
  2020-02-26  1:00   ` Frederic Weisbecker
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  2020-02-25 21:36 ` [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check() Thomas Gleixner
                   ` (11 subsequent siblings)
  12 siblings, 2 replies; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-25 21:36 UTC (permalink / raw)
  To: LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann, stable

All exception entry points must have ASM_CLAC right at the
beginning. The general_protection entry is missing one.

Fixes: e59d1b0a2419 ("x86-32, smap: Add STAC/CLAC instructions to 32-bit kernel entry")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
---
 arch/x86/entry/entry_32.S |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1694,6 +1694,7 @@ SYM_CODE_START(int3)
 SYM_CODE_END(int3)
 
 SYM_CODE_START(general_protection)
+	ASM_CLAC
 	pushl	$do_general_protection
 	jmp	common_exception
 SYM_CODE_END(general_protection)


^ permalink raw reply	[flat|nested] 45+ messages in thread

* [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
  2020-02-25 21:36 ` [patch 01/10] x86/entry/32: Add missing ASM_CLAC to general_protection entry Thomas Gleixner
@ 2020-02-25 21:36 ` Thomas Gleixner
  2020-02-26  1:13   ` Frederic Weisbecker
                     ` (2 more replies)
  2020-02-25 21:36 ` [patch 03/10] x86/entry/32: Force MCE through do_mce() Thomas Gleixner
                   ` (10 subsequent siblings)
  12 siblings, 3 replies; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-25 21:36 UTC (permalink / raw)
  To: LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann, Andy Lutomirski

From: Andy Lutomirski <luto@kernel.org>

do_machine_check() can be raised in almost any context including the most
fragile ones. Prevent kprobes and tracing.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/include/asm/traps.h   |    3 ---
 arch/x86/kernel/cpu/mce/core.c |   12 ++++++++++--
 2 files changed, 10 insertions(+), 5 deletions(-)

--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -88,9 +88,6 @@ dotraplinkage void do_page_fault(struct
 dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *regs, long error_code);
 dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code);
 dotraplinkage void do_alignment_check(struct pt_regs *regs, long error_code);
-#ifdef CONFIG_X86_MCE
-dotraplinkage void do_machine_check(struct pt_regs *regs, long error_code);
-#endif
 dotraplinkage void do_simd_coprocessor_error(struct pt_regs *regs, long error_code);
 #ifdef CONFIG_X86_32
 dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code);
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1213,8 +1213,14 @@ static void __mc_scan_banks(struct mce *
  * On Intel systems this is entered on all CPUs in parallel through
  * MCE broadcast. However some CPUs might be broken beyond repair,
  * so be always careful when synchronizing with others.
+ *
+ * Tracing and kprobes are disabled: if we interrupted a kernel context
+ * with IF=1, we need to minimize stack usage.  There are also recursion
+ * issues: if the machine check was due to a failure of the memory
+ * backing the user stack, tracing that reads the user stack will cause
+ * potentially infinite recursion.
  */
-void do_machine_check(struct pt_regs *regs, long error_code)
+void notrace do_machine_check(struct pt_regs *regs, long error_code)
 {
 	DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
 	DECLARE_BITMAP(toclear, MAX_NR_BANKS);
@@ -1360,6 +1366,7 @@ void do_machine_check(struct pt_regs *re
 	ist_exit(regs);
 }
 EXPORT_SYMBOL_GPL(do_machine_check);
+NOKPROBE_SYMBOL(do_machine_check);
 
 #ifndef CONFIG_MEMORY_FAILURE
 int memory_failure(unsigned long pfn, int flags)
@@ -1892,10 +1899,11 @@ static void unexpected_machine_check(str
 void (*machine_check_vector)(struct pt_regs *, long error_code) =
 						unexpected_machine_check;
 
-dotraplinkage void do_mce(struct pt_regs *regs, long error_code)
+dotraplinkage notrace void do_mce(struct pt_regs *regs, long error_code)
 {
 	machine_check_vector(regs, error_code);
 }
+NOKPROBE_SYMBOL(do_mce);
 
 /*
  * Called for each booted CPU to set up machine checks.


^ permalink raw reply	[flat|nested] 45+ messages in thread

* [patch 03/10] x86/entry/32: Force MCE through do_mce()
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
  2020-02-25 21:36 ` [patch 01/10] x86/entry/32: Add missing ASM_CLAC to general_protection entry Thomas Gleixner
  2020-02-25 21:36 ` [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check() Thomas Gleixner
@ 2020-02-25 21:36 ` Thomas Gleixner
  2020-02-26  1:11   ` Frederic Weisbecker
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  2020-02-25 21:36 ` [patch 04/10] x86/traps: Remove pointless irq enable from do_spurious_interrupt_bug() Thomas Gleixner
                   ` (9 subsequent siblings)
  12 siblings, 2 replies; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-25 21:36 UTC (permalink / raw)
  To: LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann

Remove the pointless difference between 32 and 64 bit to make further
unifications simpler.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/entry/entry_32.S          |    2 +-
 arch/x86/include/asm/mce.h         |    3 ---
 arch/x86/kernel/cpu/mce/internal.h |    3 +++
 3 files changed, 4 insertions(+), 4 deletions(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1365,7 +1365,7 @@ SYM_CODE_END(divide_error)
 SYM_CODE_START(machine_check)
 	ASM_CLAC
 	pushl	$0
-	pushl	machine_check_vector
+	pushl	$do_mce
 	jmp	common_exception
 SYM_CODE_END(machine_check)
 #endif
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -238,9 +238,6 @@ extern void mce_disable_bank(int bank);
 /*
  * Exception handler
  */
-
-/* Call the installed machine check handler for this CPU setup. */
-extern void (*machine_check_vector)(struct pt_regs *, long error_code);
 void do_machine_check(struct pt_regs *, long);
 
 /*
--- a/arch/x86/kernel/cpu/mce/internal.h
+++ b/arch/x86/kernel/cpu/mce/internal.h
@@ -8,6 +8,9 @@
 #include <linux/device.h>
 #include <asm/mce.h>
 
+/* Pointer to the installed machine check handler for this CPU setup. */
+extern void (*machine_check_vector)(struct pt_regs *, long error_code);
+
 enum severity_level {
 	MCE_NO_SEVERITY,
 	MCE_DEFERRED_SEVERITY,


^ permalink raw reply	[flat|nested] 45+ messages in thread

* [patch 04/10] x86/traps: Remove pointless irq enable from do_spurious_interrupt_bug()
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
                   ` (2 preceding siblings ...)
  2020-02-25 21:36 ` [patch 03/10] x86/entry/32: Force MCE through do_mce() Thomas Gleixner
@ 2020-02-25 21:36 ` Thomas Gleixner
  2020-02-26  1:19   ` Frederic Weisbecker
  2020-02-25 21:36 ` [patch 05/10] x86/traps: Document do_spurious_interrupt_bug() Thomas Gleixner
                   ` (8 subsequent siblings)
  12 siblings, 1 reply; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-25 21:36 UTC (permalink / raw)
  To: LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann, Sean Christopherson, Alexandre Chartre,
	Peter Zijlstra (Intel)

From: Thomas Gleixner <tglx@linutronix.de>

That function returns immediately after conditionally reenabling interrupts which
is more than pointless and requires the ASM code to disable interrupts again.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20191023123117.871608831@linutronix.de

---
 arch/x86/kernel/traps.c |    1 -
 1 file changed, 1 deletion(-)

--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -862,7 +862,6 @@ do_simd_coprocessor_error(struct pt_regs
 dotraplinkage void
 do_spurious_interrupt_bug(struct pt_regs *regs, long error_code)
 {
-	cond_local_irq_enable(regs);
 }
 
 dotraplinkage void


^ permalink raw reply	[flat|nested] 45+ messages in thread

* [patch 05/10] x86/traps: Document do_spurious_interrupt_bug()
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
                   ` (3 preceding siblings ...)
  2020-02-25 21:36 ` [patch 04/10] x86/traps: Remove pointless irq enable from do_spurious_interrupt_bug() Thomas Gleixner
@ 2020-02-25 21:36 ` Thomas Gleixner
  2020-02-26 17:08   ` Frederic Weisbecker
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  2020-02-25 21:36 ` [patch 06/10] x86/traps: Remove redundant declaration of do_double_fault() Thomas Gleixner
                   ` (7 subsequent siblings)
  12 siblings, 2 replies; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-25 21:36 UTC (permalink / raw)
  To: LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann, Josh Poimboeuf

Add a comment which explains why this empty handler for a reserved vector
exists.

Requested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/traps.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -862,6 +862,25 @@ do_simd_coprocessor_error(struct pt_regs
 dotraplinkage void
 do_spurious_interrupt_bug(struct pt_regs *regs, long error_code)
 {
+	/*
+	 * This addresses a Pentium Pro Erratum:
+	 *
+	 * PROBLEM: If the APIC subsystem is configured in mixed mode with
+	 * Virtual Wire mode implemented through the local APIC, an
+	 * interrupt vector of 0Fh (Intel reserved encoding) may be
+	 * generated by the local APIC (Int 15).  This vector may be
+	 * generated upon receipt of a spurious interrupt (an interrupt
+	 * which is removed before the system receives the INTA sequence)
+	 * instead of the programmed 8259 spurious interrupt vector.
+	 *
+	 * IMPLICATION: The spurious interrupt vector programmed in the
+	 * 8259 is normally handled by an operating system's spurious
+	 * interrupt handler. However, a vector of 0Fh is unknown to some
+	 * operating systems, which would crash if this erratum occurred.
+	 *
+	 * In theory this could be limited to 32bit, but the handler is not
+	 * hurting and who knows which other CPUs suffer from this.
+	 */
 }
 
 dotraplinkage void


^ permalink raw reply	[flat|nested] 45+ messages in thread

* [patch 06/10] x86/traps: Remove redundant declaration of do_double_fault()
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
                   ` (4 preceding siblings ...)
  2020-02-25 21:36 ` [patch 05/10] x86/traps: Document do_spurious_interrupt_bug() Thomas Gleixner
@ 2020-02-25 21:36 ` Thomas Gleixner
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  2020-02-25 21:36 ` [patch 07/10] x86/irq: Remove useless return value from do_IRQ() Thomas Gleixner
                   ` (6 subsequent siblings)
  12 siblings, 1 reply; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-25 21:36 UTC (permalink / raw)
  To: LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/include/asm/traps.h |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -76,13 +76,6 @@ dotraplinkage void do_coprocessor_segmen
 dotraplinkage void do_invalid_TSS(struct pt_regs *regs, long error_code);
 dotraplinkage void do_segment_not_present(struct pt_regs *regs, long error_code);
 dotraplinkage void do_stack_segment(struct pt_regs *regs, long error_code);
-#ifdef CONFIG_X86_64
-dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsigned long address);
-asmlinkage __visible notrace struct pt_regs *sync_regs(struct pt_regs *eregs);
-asmlinkage __visible notrace
-struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s);
-void __init trap_init(void);
-#endif
 dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code);
 dotraplinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address);
 dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *regs, long error_code);
@@ -94,6 +87,13 @@ dotraplinkage void do_iret_error(struct
 #endif
 dotraplinkage void do_mce(struct pt_regs *regs, long error_code);
 
+#ifdef CONFIG_X86_64
+asmlinkage __visible notrace struct pt_regs *sync_regs(struct pt_regs *eregs);
+asmlinkage __visible notrace
+struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s);
+void __init trap_init(void);
+#endif
+
 static inline int get_si_code(unsigned long condition)
 {
 	if (condition & DR_STEP)


^ permalink raw reply	[flat|nested] 45+ messages in thread

* [patch 07/10] x86/irq: Remove useless return value from do_IRQ()
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
                   ` (5 preceding siblings ...)
  2020-02-25 21:36 ` [patch 06/10] x86/traps: Remove redundant declaration of do_double_fault() Thomas Gleixner
@ 2020-02-25 21:36 ` Thomas Gleixner
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  2020-02-25 21:36 ` [patch 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries Thomas Gleixner
                   ` (5 subsequent siblings)
  12 siblings, 1 reply; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-25 21:36 UTC (permalink / raw)
  To: LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann

Nothing is using it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/include/asm/irq.h |    2 +-
 arch/x86/kernel/irq.c      |    3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -36,7 +36,7 @@ extern void native_init_IRQ(void);
 
 extern void handle_irq(struct irq_desc *desc, struct pt_regs *regs);
 
-extern __visible unsigned int do_IRQ(struct pt_regs *regs);
+extern __visible void do_IRQ(struct pt_regs *regs);
 
 extern void init_ISA_irqs(void);
 
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -230,7 +230,7 @@ u64 arch_irq_stat(void)
  * SMP cross-CPU interrupts have their own specific
  * handlers).
  */
-__visible unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
+__visible void __irq_entry do_IRQ(struct pt_regs *regs)
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
 	struct irq_desc * desc;
@@ -263,7 +263,6 @@ u64 arch_irq_stat(void)
 	exiting_irq();
 
 	set_irq_regs(old_regs);
-	return 1;
 }
 
 #ifdef CONFIG_X86_LOCAL_APIC


^ permalink raw reply	[flat|nested] 45+ messages in thread

* [patch 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
                   ` (6 preceding siblings ...)
  2020-02-25 21:36 ` [patch 07/10] x86/irq: Remove useless return value from do_IRQ() Thomas Gleixner
@ 2020-02-25 21:36 ` Thomas Gleixner
  2020-02-26  5:34   ` Andy Lutomirski
  2020-02-25 21:36 ` [patch 09/10] x86/entry/entry_32: Route int3 through common_exception Thomas Gleixner
                   ` (4 subsequent siblings)
  12 siblings, 1 reply; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-25 21:36 UTC (permalink / raw)
  To: LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann

Nothing cares about the -1 "mark as interrupt" in the errorcode anymore. Just
use 0 for all excpetions which do not have an errorcode consistently.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/entry/entry_32.S |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1290,7 +1290,7 @@ SYM_CODE_END(simd_coprocessor_error)
 
 SYM_CODE_START(device_not_available)
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 	pushl	$do_device_not_available
 	jmp	common_exception
 SYM_CODE_END(device_not_available)
@@ -1531,7 +1531,7 @@ SYM_CODE_START(debug)
 	 * Entry from sysenter is now handled in common_exception
 	 */
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 	pushl	$do_debug
 	jmp	common_exception
 SYM_CODE_END(debug)
@@ -1682,7 +1682,7 @@ SYM_CODE_END(nmi)
 
 SYM_CODE_START(int3)
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 
 	SAVE_ALL switch_stacks=1
 	ENCODE_FRAME_POINTER


^ permalink raw reply	[flat|nested] 45+ messages in thread

* [patch 09/10] x86/entry/entry_32: Route int3 through common_exception
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
                   ` (7 preceding siblings ...)
  2020-02-25 21:36 ` [patch 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries Thomas Gleixner
@ 2020-02-25 21:36 ` Thomas Gleixner
  2020-02-26 17:35   ` Frederic Weisbecker
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  2020-02-25 21:36 ` [patch 10/10] x86/traps: Stop using ist_enter/exit() in do_int3() Thomas Gleixner
                   ` (3 subsequent siblings)
  12 siblings, 2 replies; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-25 21:36 UTC (permalink / raw)
  To: LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann

int3 is not using the common_exception path for purely historical reasons,
but there is no reason to keep it the only exception which is different.

Make it use common_exception so the upcoming changes to autogenerate the
entry stubs do not have to special case int3.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/entry/entry_32.S |   10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1683,14 +1683,8 @@ SYM_CODE_END(nmi)
 SYM_CODE_START(int3)
 	ASM_CLAC
 	pushl	$0
-
-	SAVE_ALL switch_stacks=1
-	ENCODE_FRAME_POINTER
-	TRACE_IRQS_OFF
-	xorl	%edx, %edx			# zero error code
-	movl	%esp, %eax			# pt_regs pointer
-	call	do_int3
-	jmp	ret_from_exception
+	pushl	$do_int3
+	jmp	common_exception
 SYM_CODE_END(int3)
 
 SYM_CODE_START(general_protection)


^ permalink raw reply	[flat|nested] 45+ messages in thread

* [patch 10/10] x86/traps: Stop using ist_enter/exit() in do_int3()
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
                   ` (8 preceding siblings ...)
  2020-02-25 21:36 ` [patch 09/10] x86/entry/entry_32: Route int3 through common_exception Thomas Gleixner
@ 2020-02-25 21:36 ` Thomas Gleixner
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  2020-02-27 14:33   ` tip-bot2 for Andy Lutomirski
  2020-02-26  5:26 ` [patch 00/10] x86/entry: Consolidation - Part I Andy Lutomirski
                   ` (2 subsequent siblings)
  12 siblings, 2 replies; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-25 21:36 UTC (permalink / raw)
  To: LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann, Andy Lutomirski

#BP is not longer using IST and using ist_enter() and ist_exit() makes it
harder to change ist_enter() and ist_exit()'s behavior.  Instead open-code
the very small amount of required logic.

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

---
 arch/x86/kernel/traps.c |   21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -572,14 +572,20 @@ dotraplinkage void notrace do_int3(struc
 		return;
 
 	/*
-	 * Use ist_enter despite the fact that we don't use an IST stack.
-	 * We can be called from a kprobe in non-CONTEXT_KERNEL kernel
-	 * mode or even during context tracking state changes.
+	 * Unlike any other non-IST entry, we can be called from a kprobe in
+	 * non-CONTEXT_KERNEL kernel mode or even during context tracking
+	 * state changes.  Make sure that we wake up RCU even if we're coming
+	 * from kernel code.
 	 *
-	 * This means that we can't schedule.  That's okay.
+	 * This means that we can't schedule even if we came from a
+	 * preemptible kernel context.  That's okay.
 	 */
-	ist_enter(regs);
+	if (!user_mode(regs)) {
+		rcu_nmi_enter();
+		preempt_disable();
+	}
 	RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
+
 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
 	if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
 				SIGTRAP) == NOTIFY_STOP)
@@ -600,7 +606,10 @@ dotraplinkage void notrace do_int3(struc
 	cond_local_irq_disable(regs);
 
 exit:
-	ist_exit(regs);
+	if (!user_mode(regs)) {
+		preempt_enable_no_resched();
+		rcu_nmi_exit();
+	}
 }
 NOKPROBE_SYMBOL(do_int3);
 


^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 01/10] x86/entry/32: Add missing ASM_CLAC to general_protection entry
  2020-02-25 21:36 ` [patch 01/10] x86/entry/32: Add missing ASM_CLAC to general_protection entry Thomas Gleixner
@ 2020-02-26  1:00   ` Frederic Weisbecker
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  1 sibling, 0 replies; 45+ messages in thread
From: Frederic Weisbecker @ 2020-02-26  1:00 UTC (permalink / raw)
  To: Thomas Gleixner
  Cc: LKML, x86, Steven Rostedt, Brian Gerst, Juergen Gross,
	Paolo Bonzini, Arnd Bergmann, stable

On Tue, Feb 25, 2020 at 10:36:37PM +0100, Thomas Gleixner wrote:
> All exception entry points must have ASM_CLAC right at the
> beginning. The general_protection entry is missing one.
> 
> Fixes: e59d1b0a2419 ("x86-32, smap: Add STAC/CLAC instructions to 32-bit kernel entry")
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: stable@vger.kernel.org

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 03/10] x86/entry/32: Force MCE through do_mce()
  2020-02-25 21:36 ` [patch 03/10] x86/entry/32: Force MCE through do_mce() Thomas Gleixner
@ 2020-02-26  1:11   ` Frederic Weisbecker
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  1 sibling, 0 replies; 45+ messages in thread
From: Frederic Weisbecker @ 2020-02-26  1:11 UTC (permalink / raw)
  To: Thomas Gleixner
  Cc: LKML, x86, Steven Rostedt, Brian Gerst, Juergen Gross,
	Paolo Bonzini, Arnd Bergmann

On Tue, Feb 25, 2020 at 10:36:39PM +0100, Thomas Gleixner wrote:
> Remove the pointless difference between 32 and 64 bit to make further
> unifications simpler.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-25 21:36 ` [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check() Thomas Gleixner
@ 2020-02-26  1:13   ` Frederic Weisbecker
  2020-02-26  5:29     ` Andy Lutomirski
  2020-02-26 11:18   ` Borislav Petkov
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Andy Lutomirski
  2 siblings, 1 reply; 45+ messages in thread
From: Frederic Weisbecker @ 2020-02-26  1:13 UTC (permalink / raw)
  To: Thomas Gleixner
  Cc: LKML, x86, Steven Rostedt, Brian Gerst, Juergen Gross,
	Paolo Bonzini, Arnd Bergmann, Andy Lutomirski

On Tue, Feb 25, 2020 at 10:36:38PM +0100, Thomas Gleixner wrote:
> From: Andy Lutomirski <luto@kernel.org>
> 
> do_machine_check() can be raised in almost any context including the most
> fragile ones. Prevent kprobes and tracing.
> 
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
>  arch/x86/include/asm/traps.h   |    3 ---
>  arch/x86/kernel/cpu/mce/core.c |   12 ++++++++++--
>  2 files changed, 10 insertions(+), 5 deletions(-)
> 
> --- a/arch/x86/include/asm/traps.h
> +++ b/arch/x86/include/asm/traps.h
> @@ -88,9 +88,6 @@ dotraplinkage void do_page_fault(struct
>  dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *regs, long error_code);
>  dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code);
>  dotraplinkage void do_alignment_check(struct pt_regs *regs, long error_code);
> -#ifdef CONFIG_X86_MCE
> -dotraplinkage void do_machine_check(struct pt_regs *regs, long error_code);
> -#endif
>  dotraplinkage void do_simd_coprocessor_error(struct pt_regs *regs, long error_code);
>  #ifdef CONFIG_X86_32
>  dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code);
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -1213,8 +1213,14 @@ static void __mc_scan_banks(struct mce *
>   * On Intel systems this is entered on all CPUs in parallel through
>   * MCE broadcast. However some CPUs might be broken beyond repair,
>   * so be always careful when synchronizing with others.
> + *
> + * Tracing and kprobes are disabled: if we interrupted a kernel context
> + * with IF=1, we need to minimize stack usage.  There are also recursion
> + * issues: if the machine check was due to a failure of the memory
> + * backing the user stack, tracing that reads the user stack will cause
> + * potentially infinite recursion.
>   */
> -void do_machine_check(struct pt_regs *regs, long error_code)
> +void notrace do_machine_check(struct pt_regs *regs, long error_code)
>  {
>  	DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
>  	DECLARE_BITMAP(toclear, MAX_NR_BANKS);
> @@ -1360,6 +1366,7 @@ void do_machine_check(struct pt_regs *re
>  	ist_exit(regs);
>  }
>  EXPORT_SYMBOL_GPL(do_machine_check);
> +NOKPROBE_SYMBOL(do_machine_check);

That won't protect all the function called by do_machine_check(), right?
There are lots of them.

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 04/10] x86/traps: Remove pointless irq enable from do_spurious_interrupt_bug()
  2020-02-25 21:36 ` [patch 04/10] x86/traps: Remove pointless irq enable from do_spurious_interrupt_bug() Thomas Gleixner
@ 2020-02-26  1:19   ` Frederic Weisbecker
  0 siblings, 0 replies; 45+ messages in thread
From: Frederic Weisbecker @ 2020-02-26  1:19 UTC (permalink / raw)
  To: Thomas Gleixner
  Cc: LKML, x86, Steven Rostedt, Brian Gerst, Juergen Gross,
	Paolo Bonzini, Arnd Bergmann, Sean Christopherson,
	Alexandre Chartre, Peter Zijlstra (Intel)

On Tue, Feb 25, 2020 at 10:36:40PM +0100, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
> 
> That function returns immediately after conditionally reenabling interrupts which
> is more than pointless and requires the ASM code to disable interrupts again.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Link: https://lore.kernel.org/r/20191023123117.871608831@linutronix.de

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 00/10] x86/entry: Consolidation - Part I
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
                   ` (9 preceding siblings ...)
  2020-02-25 21:36 ` [patch 10/10] x86/traps: Stop using ist_enter/exit() in do_int3() Thomas Gleixner
@ 2020-02-26  5:26 ` Andy Lutomirski
  2020-02-26  5:35 ` Andy Lutomirski
  2020-02-27 11:01 ` Alexandre Chartre
  12 siblings, 0 replies; 45+ messages in thread
From: Andy Lutomirski @ 2020-02-26  5:26 UTC (permalink / raw)
  To: Thomas Gleixner, LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann

On 2/25/20 1:36 PM, Thomas Gleixner wrote:
> Hi!
> 
> This is the first batch of a 73 patches series which consolidates the x86
> entry code.
> 

Egads!

If there's a v2, I don't suppose you could tweak your subject-prefix to
generate something like [patch part1 2/10]?

--Andy

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-26  1:13   ` Frederic Weisbecker
@ 2020-02-26  5:29     ` Andy Lutomirski
  2020-02-26 13:28       ` Peter Zijlstra
  0 siblings, 1 reply; 45+ messages in thread
From: Andy Lutomirski @ 2020-02-26  5:29 UTC (permalink / raw)
  To: Frederic Weisbecker, Thomas Gleixner
  Cc: LKML, x86, Steven Rostedt, Brian Gerst, Juergen Gross,
	Paolo Bonzini, Arnd Bergmann

On 2/25/20 5:13 PM, Frederic Weisbecker wrote:
> On Tue, Feb 25, 2020 at 10:36:38PM +0100, Thomas Gleixner wrote:
>> From: Andy Lutomirski <luto@kernel.org>
>>
>> do_machine_check() can be raised in almost any context including the most
>> fragile ones. Prevent kprobes and tracing.
>>
>> Signed-off-by: Andy Lutomirski <luto@kernel.org>
>> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>> ---
>>  arch/x86/include/asm/traps.h   |    3 ---
>>  arch/x86/kernel/cpu/mce/core.c |   12 ++++++++++--
>>  2 files changed, 10 insertions(+), 5 deletions(-)
>>
>> --- a/arch/x86/include/asm/traps.h
>> +++ b/arch/x86/include/asm/traps.h
>> @@ -88,9 +88,6 @@ dotraplinkage void do_page_fault(struct
>>  dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *regs, long error_code);
>>  dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code);
>>  dotraplinkage void do_alignment_check(struct pt_regs *regs, long error_code);
>> -#ifdef CONFIG_X86_MCE
>> -dotraplinkage void do_machine_check(struct pt_regs *regs, long error_code);
>> -#endif
>>  dotraplinkage void do_simd_coprocessor_error(struct pt_regs *regs, long error_code);
>>  #ifdef CONFIG_X86_32
>>  dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code);
>> --- a/arch/x86/kernel/cpu/mce/core.c
>> +++ b/arch/x86/kernel/cpu/mce/core.c
>> @@ -1213,8 +1213,14 @@ static void __mc_scan_banks(struct mce *
>>   * On Intel systems this is entered on all CPUs in parallel through
>>   * MCE broadcast. However some CPUs might be broken beyond repair,
>>   * so be always careful when synchronizing with others.
>> + *
>> + * Tracing and kprobes are disabled: if we interrupted a kernel context
>> + * with IF=1, we need to minimize stack usage.  There are also recursion
>> + * issues: if the machine check was due to a failure of the memory
>> + * backing the user stack, tracing that reads the user stack will cause
>> + * potentially infinite recursion.
>>   */
>> -void do_machine_check(struct pt_regs *regs, long error_code)
>> +void notrace do_machine_check(struct pt_regs *regs, long error_code)
>>  {
>>  	DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
>>  	DECLARE_BITMAP(toclear, MAX_NR_BANKS);
>> @@ -1360,6 +1366,7 @@ void do_machine_check(struct pt_regs *re
>>  	ist_exit(regs);
>>  }
>>  EXPORT_SYMBOL_GPL(do_machine_check);
>> +NOKPROBE_SYMBOL(do_machine_check);
> 
> That won't protect all the function called by do_machine_check(), right?
> There are lots of them.
> 

It at least means we can survive to run actual C code in
do_machine_check(), which lets us try to mitigate this issue further.
PeterZ has patches for that, and maybe this series fixes it later on.
(I'm reading in order!)

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries
  2020-02-25 21:36 ` [patch 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries Thomas Gleixner
@ 2020-02-26  5:34   ` Andy Lutomirski
  2020-02-26 18:42     ` Thomas Gleixner
  0 siblings, 1 reply; 45+ messages in thread
From: Andy Lutomirski @ 2020-02-26  5:34 UTC (permalink / raw)
  To: Thomas Gleixner, LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann

On 2/25/20 1:36 PM, Thomas Gleixner wrote:
> Nothing cares about the -1 "mark as interrupt" in the errorcode anymore. Just
> use 0 for all excpetions which do not have an errorcode consistently.
> 

I sincerely wish this were the case.  But look at collect_syscall() in
lib/syscall.c.

It would be really quite nice to address this for real in some
low-overhead way.  My suggestion would be to borrow a trick from 32-bit:
split regs->cs into ->cs and ->__csh, and stick CS_FROM_SYSCALL into
__csh for syscalls.  This will only add any overhead at all to the int80
case.  Then we could adjust syscall_get_nr() to look for CS_FROM_SYSCALL.

What do you think?  An alternative would be to use the stack walking
machinery in collect_syscall(), since the mere existence of that
function is abomination and we may not care about performance.

--Andy

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 00/10] x86/entry: Consolidation - Part I
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
                   ` (10 preceding siblings ...)
  2020-02-26  5:26 ` [patch 00/10] x86/entry: Consolidation - Part I Andy Lutomirski
@ 2020-02-26  5:35 ` Andy Lutomirski
  2020-02-27 11:01 ` Alexandre Chartre
  12 siblings, 0 replies; 45+ messages in thread
From: Andy Lutomirski @ 2020-02-26  5:35 UTC (permalink / raw)
  To: Thomas Gleixner, LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann

On 2/25/20 1:36 PM, Thomas Gleixner wrote:
> Hi!
> 
> This is the first batch of a 73 patches series which consolidates the x86
> entry code.
> 
> 

In part 1, all but 08/10 are:

Reviewed-by: Andy Lutomirski <luto@kernel.org>

I object to patch 8 as described in my reply.

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-25 21:36 ` [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check() Thomas Gleixner
  2020-02-26  1:13   ` Frederic Weisbecker
@ 2020-02-26 11:18   ` Borislav Petkov
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Andy Lutomirski
  2 siblings, 0 replies; 45+ messages in thread
From: Borislav Petkov @ 2020-02-26 11:18 UTC (permalink / raw)
  To: Thomas Gleixner
  Cc: LKML, x86, Steven Rostedt, Brian Gerst, Juergen Gross,
	Paolo Bonzini, Arnd Bergmann, Andy Lutomirski

On Tue, Feb 25, 2020 at 10:36:38PM +0100, Thomas Gleixner wrote:
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -1213,8 +1213,14 @@ static void __mc_scan_banks(struct mce *
>   * On Intel systems this is entered on all CPUs in parallel through
>   * MCE broadcast. However some CPUs might be broken beyond repair,
>   * so be always careful when synchronizing with others.
> + *
> + * Tracing and kprobes are disabled: if we interrupted a kernel context
> + * with IF=1, we need to minimize stack usage.  There are also recursion
> + * issues: if the machine check was due to a failure of the memory
> + * backing the user stack, tracing that reads the user stack will cause
			      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Had to read this a couple of times to parse that formulation properly.
Make that

"... backing the user stack, tracing code which accesses same user stack
will potentially cause an infinite recursion."

With that:

Reviewed-by: Borislav Petkov <bp@suse.de>

Thx.

-- 
Regards/Gruss,
    Boris.

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

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-26  5:29     ` Andy Lutomirski
@ 2020-02-26 13:28       ` Peter Zijlstra
  2020-02-26 15:10         ` Andy Lutomirski
  0 siblings, 1 reply; 45+ messages in thread
From: Peter Zijlstra @ 2020-02-26 13:28 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Frederic Weisbecker, Thomas Gleixner, LKML, x86, Steven Rostedt,
	Brian Gerst, Juergen Gross, Paolo Bonzini, Arnd Bergmann

On Tue, Feb 25, 2020 at 09:29:00PM -0800, Andy Lutomirski wrote:

> >> +void notrace do_machine_check(struct pt_regs *regs, long error_code)
> >>  {
> >>  	DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
> >>  	DECLARE_BITMAP(toclear, MAX_NR_BANKS);
> >> @@ -1360,6 +1366,7 @@ void do_machine_check(struct pt_regs *re
> >>  	ist_exit(regs);
> >>  }
> >>  EXPORT_SYMBOL_GPL(do_machine_check);
> >> +NOKPROBE_SYMBOL(do_machine_check);
> > 
> > That won't protect all the function called by do_machine_check(), right?
> > There are lots of them.
> > 
> 
> It at least means we can survive to run actual C code in
> do_machine_check(), which lets us try to mitigate this issue further.
> PeterZ has patches for that, and maybe this series fixes it later on.
> (I'm reading in order!)

Yeah, I don't cover that either. Making the kernel completely kprobe
safe is _lots_ more work I think.

We really need some form of automation for this :/ The current situation
is completely nonsatisfactory.

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-26 13:28       ` Peter Zijlstra
@ 2020-02-26 15:10         ` Andy Lutomirski
  2020-02-26 16:08           ` Peter Zijlstra
  0 siblings, 1 reply; 45+ messages in thread
From: Andy Lutomirski @ 2020-02-26 15:10 UTC (permalink / raw)
  To: Peter Zijlstra
  Cc: Andy Lutomirski, Frederic Weisbecker, Thomas Gleixner, LKML,
	X86 ML, Steven Rostedt, Brian Gerst, Juergen Gross,
	Paolo Bonzini, Arnd Bergmann

On Wed, Feb 26, 2020 at 5:28 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Tue, Feb 25, 2020 at 09:29:00PM -0800, Andy Lutomirski wrote:
>
> > >> +void notrace do_machine_check(struct pt_regs *regs, long error_code)
> > >>  {
> > >>    DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
> > >>    DECLARE_BITMAP(toclear, MAX_NR_BANKS);
> > >> @@ -1360,6 +1366,7 @@ void do_machine_check(struct pt_regs *re
> > >>    ist_exit(regs);
> > >>  }
> > >>  EXPORT_SYMBOL_GPL(do_machine_check);
> > >> +NOKPROBE_SYMBOL(do_machine_check);
> > >
> > > That won't protect all the function called by do_machine_check(), right?
> > > There are lots of them.
> > >
> >
> > It at least means we can survive to run actual C code in
> > do_machine_check(), which lets us try to mitigate this issue further.
> > PeterZ has patches for that, and maybe this series fixes it later on.
> > (I'm reading in order!)
>
> Yeah, I don't cover that either. Making the kernel completely kprobe
> safe is _lots_ more work I think.
>
> We really need some form of automation for this :/ The current situation
> is completely nonsatisfactory.

I've looked at too many patches lately and lost track a bit of which
is which.  Shouldn't a simple tracing_disable() or similar in
do_machine_check() be sufficient?  We'd maybe want automation to check
everything before it.  We still need to survive hitting a kprobe int3,
but that shouldn't have recursion issues.

(Yes, that function doesn't exist in current kernels.  And we'd need
to make sure that BPF respects it.)

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-26 15:10         ` Andy Lutomirski
@ 2020-02-26 16:08           ` Peter Zijlstra
  2020-02-26 17:28             ` Andy Lutomirski
  0 siblings, 1 reply; 45+ messages in thread
From: Peter Zijlstra @ 2020-02-26 16:08 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Frederic Weisbecker, Thomas Gleixner, LKML, X86 ML,
	Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann

On Wed, Feb 26, 2020 at 07:10:01AM -0800, Andy Lutomirski wrote:
> On Wed, Feb 26, 2020 at 5:28 AM Peter Zijlstra <peterz@infradead.org> wrote:
> > On Tue, Feb 25, 2020 at 09:29:00PM -0800, Andy Lutomirski wrote:
> >
> > > >> +void notrace do_machine_check(struct pt_regs *regs, long error_code)
> > > >>  {
> > > >>    DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
> > > >>    DECLARE_BITMAP(toclear, MAX_NR_BANKS);
> > > >> @@ -1360,6 +1366,7 @@ void do_machine_check(struct pt_regs *re
> > > >>    ist_exit(regs);
> > > >>  }
> > > >>  EXPORT_SYMBOL_GPL(do_machine_check);
> > > >> +NOKPROBE_SYMBOL(do_machine_check);
> > > >
> > > > That won't protect all the function called by do_machine_check(), right?
> > > > There are lots of them.
> > > >
> > >
> > > It at least means we can survive to run actual C code in
> > > do_machine_check(), which lets us try to mitigate this issue further.
> > > PeterZ has patches for that, and maybe this series fixes it later on.
> > > (I'm reading in order!)
> >
> > Yeah, I don't cover that either. Making the kernel completely kprobe
> > safe is _lots_ more work I think.
> >
> > We really need some form of automation for this :/ The current situation
> > is completely nonsatisfactory.
> 
> I've looked at too many patches lately and lost track a bit of which
> is which.  Shouldn't a simple tracing_disable() or similar in
> do_machine_check() be sufficient?

It entirely depends on what the goal is :-/ On the one hand I see why
people might want function tracing / kprobes enabled, OTOH it's all
mighty frigging scary. Any tracing/probing/whatever on an MCE has the
potential to make a bad situation worse -- not unlike the same on #DF.

The same with that compiler instrumentation crap; allowing kprobes on
*SAN code has the potential to inject probes in arbitrary random code.
At the same time, if you're running a kernel with that on and injecting
kprobes in it, you're welcome to own the remaining pieces.

How far do we want to go? At some point I think we'll have to give
people rope, show then the knot and leave them be.

> We'd maybe want automation to check
> everything before it.  We still need to survive hitting a kprobe int3,
> but that shouldn't have recursion issues.

Right, so I think avoiding the obvious recursion issues is a more
tractable problem and yes some 'safe' spot annotation should be enough
to get automation working for that -- mostly.

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 05/10] x86/traps: Document do_spurious_interrupt_bug()
  2020-02-25 21:36 ` [patch 05/10] x86/traps: Document do_spurious_interrupt_bug() Thomas Gleixner
@ 2020-02-26 17:08   ` Frederic Weisbecker
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  1 sibling, 0 replies; 45+ messages in thread
From: Frederic Weisbecker @ 2020-02-26 17:08 UTC (permalink / raw)
  To: Thomas Gleixner
  Cc: LKML, x86, Steven Rostedt, Brian Gerst, Juergen Gross,
	Paolo Bonzini, Arnd Bergmann, Josh Poimboeuf

On Tue, Feb 25, 2020 at 10:36:41PM +0100, Thomas Gleixner wrote:
> Add a comment which explains why this empty handler for a reserved vector
> exists.
> 
> Requested-by: Josh Poimboeuf <jpoimboe@redhat.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
>  arch/x86/kernel/traps.c |   19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -862,6 +862,25 @@ do_simd_coprocessor_error(struct pt_regs
>  dotraplinkage void
>  do_spurious_interrupt_bug(struct pt_regs *regs, long error_code)
>  {
> +	/*
> +	 * This addresses a Pentium Pro Erratum:
> +	 *
> +	 * PROBLEM: If the APIC subsystem is configured in mixed mode with
> +	 * Virtual Wire mode implemented through the local APIC, an
> +	 * interrupt vector of 0Fh (Intel reserved encoding) may be
> +	 * generated by the local APIC (Int 15).  This vector may be
> +	 * generated upon receipt of a spurious interrupt (an interrupt
> +	 * which is removed before the system receives the INTA sequence)
> +	 * instead of the programmed 8259 spurious interrupt vector.
> +	 *
> +	 * IMPLICATION: The spurious interrupt vector programmed in the
> +	 * 8259 is normally handled by an operating system's spurious
> +	 * interrupt handler. However, a vector of 0Fh is unknown to some
> +	 * operating systems, which would crash if this erratum occurred.
> +	 *
> +	 * In theory this could be limited to 32bit, but the handler is not
> +	 * hurting and who knows which other CPUs suffer from this.
> +	 */
>  }

Nice to have!

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-26 16:08           ` Peter Zijlstra
@ 2020-02-26 17:28             ` Andy Lutomirski
  2020-02-26 18:42               ` Borislav Petkov
  0 siblings, 1 reply; 45+ messages in thread
From: Andy Lutomirski @ 2020-02-26 17:28 UTC (permalink / raw)
  To: Peter Zijlstra
  Cc: Andy Lutomirski, Frederic Weisbecker, Thomas Gleixner, LKML,
	X86 ML, Steven Rostedt, Brian Gerst, Juergen Gross,
	Paolo Bonzini, Arnd Bergmann



> On Feb 26, 2020, at 8:08 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> 
> On Wed, Feb 26, 2020 at 07:10:01AM -0800, Andy Lutomirski wrote:
>>> On Wed, Feb 26, 2020 at 5:28 AM Peter Zijlstra <peterz@infradead.org> wrote:
>>>> On Tue, Feb 25, 2020 at 09:29:00PM -0800, Andy Lutomirski wrote:
>>> 
>>>>>> +void notrace do_machine_check(struct pt_regs *regs, long error_code)
>>>>>> {
>>>>>>   DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
>>>>>>   DECLARE_BITMAP(toclear, MAX_NR_BANKS);
>>>>>> @@ -1360,6 +1366,7 @@ void do_machine_check(struct pt_regs *re
>>>>>>   ist_exit(regs);
>>>>>> }
>>>>>> EXPORT_SYMBOL_GPL(do_machine_check);
>>>>>> +NOKPROBE_SYMBOL(do_machine_check);
>>>>> 
>>>>> That won't protect all the function called by do_machine_check(), right?
>>>>> There are lots of them.
>>>>> 
>>>> 
>>>> It at least means we can survive to run actual C code in
>>>> do_machine_check(), which lets us try to mitigate this issue further.
>>>> PeterZ has patches for that, and maybe this series fixes it later on.
>>>> (I'm reading in order!)
>>> 
>>> Yeah, I don't cover that either. Making the kernel completely kprobe
>>> safe is _lots_ more work I think.
>>> 
>>> We really need some form of automation for this :/ The current situation
>>> is completely nonsatisfactory.
>> 
>> I've looked at too many patches lately and lost track a bit of which
>> is which.  Shouldn't a simple tracing_disable() or similar in
>> do_machine_check() be sufficient?
> 
> It entirely depends on what the goal is :-/ On the one hand I see why
> people might want function tracing / kprobes enabled, OTOH it's all
> mighty frigging scary. Any tracing/probing/whatever on an MCE has the
> potential to make a bad situation worse -- not unlike the same on #DF.
> 
> The same with that compiler instrumentation crap; allowing kprobes on
> *SAN code has the potential to inject probes in arbitrary random code.
> At the same time, if you're running a kernel with that on and injecting
> kprobes in it, you're welcome to own the remaining pieces.
> 

Agreed.

> How far do we want to go? At some point I think we'll have to give
> people rope, show then the knot and leave them be.

If someone puts a kprobe on some TLB flush thing and an MCE does memory failure handling, it would be polite to avoid crashing.  OTOH the x86 memory failure story is *so* bad that I’m not sure how well we can ever really expect this to work.

I think we should aim to get the entry part correct, and if the meat of the function explodes, so be it.

> 
>> We'd maybe want automation to check
>> everything before it.  We still need to survive hitting a kprobe int3,
>> but that shouldn't have recursion issues.
> 
> Right, so I think avoiding the obvious recursion issues is a more
> tractable problem and yes some 'safe' spot annotation should be enough
> to get automation working for that -- mostly.

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 09/10] x86/entry/entry_32: Route int3 through common_exception
  2020-02-25 21:36 ` [patch 09/10] x86/entry/entry_32: Route int3 through common_exception Thomas Gleixner
@ 2020-02-26 17:35   ` Frederic Weisbecker
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  1 sibling, 0 replies; 45+ messages in thread
From: Frederic Weisbecker @ 2020-02-26 17:35 UTC (permalink / raw)
  To: Thomas Gleixner
  Cc: LKML, x86, Steven Rostedt, Brian Gerst, Juergen Gross,
	Paolo Bonzini, Arnd Bergmann

On Tue, Feb 25, 2020 at 10:36:45PM +0100, Thomas Gleixner wrote:
> int3 is not using the common_exception path for purely historical reasons,
> but there is no reason to keep it the only exception which is different.
> 
> Make it use common_exception so the upcoming changes to autogenerate the
> entry stubs do not have to special case int3.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-26 17:28             ` Andy Lutomirski
@ 2020-02-26 18:42               ` Borislav Petkov
  2020-02-26 18:59                 ` Peter Zijlstra
  0 siblings, 1 reply; 45+ messages in thread
From: Borislav Petkov @ 2020-02-26 18:42 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Peter Zijlstra, Andy Lutomirski, Frederic Weisbecker,
	Thomas Gleixner, LKML, X86 ML, Steven Rostedt, Brian Gerst,
	Juergen Gross, Paolo Bonzini, Arnd Bergmann

On Wed, Feb 26, 2020 at 09:28:51AM -0800, Andy Lutomirski wrote:
> > It entirely depends on what the goal is :-/ On the one hand I see why
> > people might want function tracing / kprobes enabled, OTOH it's all
> > mighty frigging scary. Any tracing/probing/whatever on an MCE has the
> > potential to make a bad situation worse -- not unlike the same on #DF.

FWIW, I had this at the beginning of the #MC handler in a feeble attempt
to poke at this:

+       hw_breakpoint_disable();
+       static_key_disable(&__tracepoint_read_msr.key);
+       tracing_off();

But then Tony noted that some recoverable errors do get reported with an
#MC exception so we would have to look at the error severity and then
decide whether to allow tracing or not.

But the error severity happens all the way down in __mc_scan_banks() -
i.e., we've executed the half handler already.

So, frankly, I wanna say, f*ck tracing etc - there are certain handlers
which simply don't allow it. And we'll only consider changing that when
a really good reason for it appears...

-- 
Regards/Gruss,
    Boris.

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

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries
  2020-02-26  5:34   ` Andy Lutomirski
@ 2020-02-26 18:42     ` Thomas Gleixner
  2020-02-26 18:57       ` Andy Lutomirski
  0 siblings, 1 reply; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-26 18:42 UTC (permalink / raw)
  To: Andy Lutomirski, LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann

Andy Lutomirski <luto@kernel.org> writes:

> On 2/25/20 1:36 PM, Thomas Gleixner wrote:
>> Nothing cares about the -1 "mark as interrupt" in the errorcode anymore. Just
>> use 0 for all excpetions which do not have an errorcode consistently.
>> 
>
> I sincerely wish this were the case.  But look at collect_syscall() in
> lib/syscall.c.
>
> It would be really quite nice to address this for real in some
> low-overhead way.  My suggestion would be to borrow a trick from 32-bit:
> split regs->cs into ->cs and ->__csh, and stick CS_FROM_SYSCALL into
> __csh for syscalls.  This will only add any overhead at all to the int80
> case.  Then we could adjust syscall_get_nr() to look for CS_FROM_SYSCALL.
>
> What do you think?  An alternative would be to use the stack walking
> machinery in collect_syscall(), since the mere existence of that
> function is abomination and we may not care about performance.

Looking deeper. The code in common_exception does:

	movl	PT_ORIG_EAX(%esp), %edx		# get the error code
	movl	$-1, PT_ORIG_EAX(%esp)		# no syscall to restart

So whatever the exception pushed on the stack the thing what
collect_syscall finds is -1.

The pushed value is used as the error_code argument for the exception
handler and I really can't find a single one which cares (anymore).

But darn and I overlooked that, it's propagated to do_trap() and
friends, but even if this causes a user visible change, I doubt that
anything cares about it today simply because for giggles a 64bit kernel
unconditionally pushes 0 for all exceptions which do not have a hardware
error code on stack. So any 32bit application which excpects a
particular error code (0/-1) in the signal would have been broken on the
first day it ran on a x64 bit kernel.

If someone yells regression, then that's really trivial to fix in
C-code.

Let me rephrase the changelog for this.

Thanks,

        tglx

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries
  2020-02-26 18:42     ` Thomas Gleixner
@ 2020-02-26 18:57       ` Andy Lutomirski
  2020-02-26 19:15         ` Thomas Gleixner
  0 siblings, 1 reply; 45+ messages in thread
From: Andy Lutomirski @ 2020-02-26 18:57 UTC (permalink / raw)
  To: Thomas Gleixner
  Cc: Andy Lutomirski, LKML, X86 ML, Steven Rostedt, Brian Gerst,
	Juergen Gross, Paolo Bonzini, Arnd Bergmann

On Wed, Feb 26, 2020 at 10:42 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> Andy Lutomirski <luto@kernel.org> writes:
>
> > On 2/25/20 1:36 PM, Thomas Gleixner wrote:
> >> Nothing cares about the -1 "mark as interrupt" in the errorcode anymore. Just
> >> use 0 for all excpetions which do not have an errorcode consistently.
> >>
> >
> > I sincerely wish this were the case.  But look at collect_syscall() in
> > lib/syscall.c.
> >
> > It would be really quite nice to address this for real in some
> > low-overhead way.  My suggestion would be to borrow a trick from 32-bit:
> > split regs->cs into ->cs and ->__csh, and stick CS_FROM_SYSCALL into
> > __csh for syscalls.  This will only add any overhead at all to the int80
> > case.  Then we could adjust syscall_get_nr() to look for CS_FROM_SYSCALL.
> >
> > What do you think?  An alternative would be to use the stack walking
> > machinery in collect_syscall(), since the mere existence of that
> > function is abomination and we may not care about performance.
>
> Looking deeper. The code in common_exception does:
>
>         movl    PT_ORIG_EAX(%esp), %edx         # get the error code
>         movl    $-1, PT_ORIG_EAX(%esp)          # no syscall to restart
>
> So whatever the exception pushed on the stack the thing what
> collect_syscall finds is -1.
>
> The pushed value is used as the error_code argument for the exception
> handler and I really can't find a single one which cares (anymore).
>
> But darn and I overlooked that, it's propagated to do_trap() and
> friends, but even if this causes a user visible change, I doubt that
> anything cares about it today simply because for giggles a 64bit kernel
> unconditionally pushes 0 for all exceptions which do not have a hardware
> error code on stack. So any 32bit application which excpects a
> particular error code (0/-1) in the signal would have been broken on the
> first day it ran on a x64 bit kernel.
>
> If someone yells regression, then that's really trivial to fix in
> C-code.

I *think* this is plumbed much more directly to userspace:

$ cat /proc/$$/syscall
61 0xffffffff 0x7ffccf734ed0 0xa 0x0 0x1 0x0 0x7ffccf734eb8 0x7f0667465eda

That entire feature is highly dubious and I suppose we could just
delete it.  But right now, we at least pretend that we can tell,
totally asynchronously, whether another task is in a syscall.  Unless
we do *something*, though, I think you shouldn't make this change.

Sticking 0 in the error_code field in ucontext for a signal with no
error code seems entirely harmless to me in contrast.

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-26 18:42               ` Borislav Petkov
@ 2020-02-26 18:59                 ` Peter Zijlstra
  2020-02-26 19:09                   ` Andy Lutomirski
  0 siblings, 1 reply; 45+ messages in thread
From: Peter Zijlstra @ 2020-02-26 18:59 UTC (permalink / raw)
  To: Borislav Petkov
  Cc: Andy Lutomirski, Andy Lutomirski, Frederic Weisbecker,
	Thomas Gleixner, LKML, X86 ML, Steven Rostedt, Brian Gerst,
	Juergen Gross, Paolo Bonzini, Arnd Bergmann

On Wed, Feb 26, 2020 at 07:42:37PM +0100, Borislav Petkov wrote:
> On Wed, Feb 26, 2020 at 09:28:51AM -0800, Andy Lutomirski wrote:
> > > It entirely depends on what the goal is :-/ On the one hand I see why
> > > people might want function tracing / kprobes enabled, OTOH it's all
> > > mighty frigging scary. Any tracing/probing/whatever on an MCE has the
> > > potential to make a bad situation worse -- not unlike the same on #DF.
> 
> FWIW, I had this at the beginning of the #MC handler in a feeble attempt
> to poke at this:
> 
> +       hw_breakpoint_disable();
> +       static_key_disable(&__tracepoint_read_msr.key);
> +       tracing_off();

You can't do static_key_disable() from an IST

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-26 18:59                 ` Peter Zijlstra
@ 2020-02-26 19:09                   ` Andy Lutomirski
  2020-02-26 20:59                     ` Steven Rostedt
  0 siblings, 1 reply; 45+ messages in thread
From: Andy Lutomirski @ 2020-02-26 19:09 UTC (permalink / raw)
  To: Peter Zijlstra
  Cc: Borislav Petkov, Andy Lutomirski, Frederic Weisbecker,
	Thomas Gleixner, LKML, X86 ML, Steven Rostedt, Brian Gerst,
	Juergen Gross, Paolo Bonzini, Arnd Bergmann



> On Feb 26, 2020, at 10:59 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> 
> On Wed, Feb 26, 2020 at 07:42:37PM +0100, Borislav Petkov wrote:
>> On Wed, Feb 26, 2020 at 09:28:51AM -0800, Andy Lutomirski wrote:
>>>> It entirely depends on what the goal is :-/ On the one hand I see why
>>>> people might want function tracing / kprobes enabled, OTOH it's all
>>>> mighty frigging scary. Any tracing/probing/whatever on an MCE has the
>>>> potential to make a bad situation worse -- not unlike the same on #DF.
>> 
>> FWIW, I had this at the beginning of the #MC handler in a feeble attempt
>> to poke at this:
>> 
>> +       hw_breakpoint_disable();
>> +       static_key_disable(&__tracepoint_read_msr.key);
>> +       tracing_off();
> 
> You can't do static_key_disable() from an IST

Can we set a percpu variable saying “in some stupid context, don’t trace”?

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries
  2020-02-26 18:57       ` Andy Lutomirski
@ 2020-02-26 19:15         ` Thomas Gleixner
  2020-02-27 14:24           ` [patch V2 " Thomas Gleixner
  0 siblings, 1 reply; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-26 19:15 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Andy Lutomirski, LKML, X86 ML, Steven Rostedt, Brian Gerst,
	Juergen Gross, Paolo Bonzini, Arnd Bergmann

Andy Lutomirski <luto@kernel.org> writes:
> On Wed, Feb 26, 2020 at 10:42 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>> The pushed value is used as the error_code argument for the exception
>> handler and I really can't find a single one which cares (anymore).
>>
>> But darn and I overlooked that, it's propagated to do_trap() and
>> friends, but even if this causes a user visible change, I doubt that
>> anything cares about it today simply because for giggles a 64bit kernel
>> unconditionally pushes 0 for all exceptions which do not have a hardware
>> error code on stack. So any 32bit application which excpects a
>> particular error code (0/-1) in the signal would have been broken on the
>> first day it ran on a x64 bit kernel.
>>
>> If someone yells regression, then that's really trivial to fix in
>> C-code.
>
> I *think* this is plumbed much more directly to userspace:
>
> $ cat /proc/$$/syscall
> 61 0xffffffff 0x7ffccf734ed0 0xa 0x0 0x1 0x0 0x7ffccf734eb8 0x7f0667465eda

The task is in syscall 61. And the 0xffffffff is syscall args[0]. So I'm
not sure what you try to demonstrate.

> That entire feature is highly dubious and I suppose we could just
> delete it.  But right now, we at least pretend that we can tell,
> totally asynchronously, whether another task is in a syscall.  Unless
> we do *something*, though, I think you shouldn't make this change.

So if a task actually hits a breakpoint that syscall proc thing reads:

-1 0xffffd0e0 0x565561a6

So even if the entry stub pushs 0, the fixup turns it into -1.

Thanks,

        tglx

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-26 19:09                   ` Andy Lutomirski
@ 2020-02-26 20:59                     ` Steven Rostedt
  0 siblings, 0 replies; 45+ messages in thread
From: Steven Rostedt @ 2020-02-26 20:59 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: Peter Zijlstra, Borislav Petkov, Andy Lutomirski,
	Frederic Weisbecker, Thomas Gleixner, LKML, X86 ML, Brian Gerst,
	Juergen Gross, Paolo Bonzini, Arnd Bergmann

On Wed, 26 Feb 2020 11:09:03 -0800
Andy Lutomirski <luto@amacapital.net> wrote:

> > On Feb 26, 2020, at 10:59 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > 
> > On Wed, Feb 26, 2020 at 07:42:37PM +0100, Borislav Petkov wrote:  
> >> On Wed, Feb 26, 2020 at 09:28:51AM -0800, Andy Lutomirski wrote:  
> >>>> It entirely depends on what the goal is :-/ On the one hand I see why
> >>>> people might want function tracing / kprobes enabled, OTOH it's all
> >>>> mighty frigging scary. Any tracing/probing/whatever on an MCE has the
> >>>> potential to make a bad situation worse -- not unlike the same on #DF.  
> >> 
> >> FWIW, I had this at the beginning of the #MC handler in a feeble attempt
> >> to poke at this:
> >> 
> >> +       hw_breakpoint_disable();
> >> +       static_key_disable(&__tracepoint_read_msr.key);
> >> +       tracing_off();  
> > 
> > You can't do static_key_disable() from an IST  
> 
> Can we set a percpu variable saying “in some stupid context, don’t trace”?

Matter's what kind of tracing you care about? "tracing_off()" only stops
writing to the ring buffer, but all the mechanisms are still in place (the
things you want to stop).

And "tracing" is not the issue. The issue is usually the breakpoint that is
added to modify the jump labels to enable tracing, or a flag that has a
trace event do a user space stack dump. It's not tracing you want to stop,
its the other parts that are attached to tracing that makes it dangerous.

-- Steve

^ permalink raw reply	[flat|nested] 45+ messages in thread

* Re: [patch 00/10] x86/entry: Consolidation - Part I
  2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
                   ` (11 preceding siblings ...)
  2020-02-26  5:35 ` Andy Lutomirski
@ 2020-02-27 11:01 ` Alexandre Chartre
  12 siblings, 0 replies; 45+ messages in thread
From: Alexandre Chartre @ 2020-02-27 11:01 UTC (permalink / raw)
  To: Thomas Gleixner, LKML
  Cc: x86, Steven Rostedt, Brian Gerst, Juergen Gross, Paolo Bonzini,
	Arnd Bergmann


On 2/25/20 10:36 PM, Thomas Gleixner wrote:
> Hi!
> 
> This is the first batch of a 73 patches series which consolidates the x86
> entry code.
> 
> This work started off as a trivial 5 patches series moving the heavy
> lifting of POSIX CPU timers out of interrupt context into thread/process
> context. This discovered that KVM is lacking to handle pending work items
> before entering guest mode and added the handling to the x86 KVM
> code. Review requested to make this a generic infrastructure.
> 
> The next series grew to 25 patches implementing the generic infrastructure,
> converting x86 (and as a POC ARM64) over, but it turned out that this was
> slightly incomplete and still had some entanglement with the rest of the
> x86 entry code as some of that functionality is shared between syscall and
> interrupt entry/exit. And it also unearthed the nastyness of IOPL which got
> already addressed in mainline.
> 
> This series addresses these issues in order to prepare for making the entry
> from userspace and exit to userspace (and it's counterpart enter guest) a
> generic infrastructure in order to restrict the necessary ASM work to the
> bare minimum.
> 
> The series is split into 5 parts:
> 
>      - General cleanups and bugfixes
> 
>      - Consolidation of the syscall entry/exit code
> 
>      - Autogenerate simple exception/trap code and reduce the difference
>        between 32 and 64 bit
> 
>      - Autogenerate complex exception/trap code and provide different entry
>        points for #DB and #MC exceptions which allows to address the
>        recently discovered RCU vs. world issues in a more structured way
> 
>      - Convert the device interrupt entry code to use the same mechanism as
>        exceptions and traps and finally convert the system vectors over as
>        well. The last step after all those cleanups is to move the return
>        from exception/interrupt logic (user mode work, kernel preemption)
>        completely from ASM into C-code, so the ASM code just has to take
>        care about returning from the exception, which is horrible and
>        convoluted enough already.
> 
> At the end the x86 entry code is ready to move the syscall parts out into
> generic code and finally tackle the initial problem which started all of
> this.
> 
> The complete series is available from git:
> 
>     git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git x86/entry
> 
> which contains all 73 patches. The individual parts are tagged, so this
> part can be retrieved via:
> 
>     git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git entry-v1-part1
> 
> Thanks,
> 
> 	tglx
> 
> 8<---------------
>   entry/entry_32.S          |   19 +++++++------------
>   include/asm/irq.h         |    2 +-
>   include/asm/mce.h         |    3 ---
>   include/asm/traps.h       |   17 +++++++----------
>   kernel/cpu/mce/core.c     |   12 ++++++++++--
>   kernel/cpu/mce/internal.h |    3 +++
>   kernel/irq.c              |    3 +--
>   kernel/traps.c            |   41 ++++++++++++++++++++++++++++++++++-------
>   8 files changed, 63 insertions(+), 37 deletions(-)
> 

For part I:

Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>

for all patches. I had a slight concern about patch 08 and propagating a different
error_code, but I agree with your argument that it is limited to 32-bit process and
now matches with the 64-bit behavior.

alex.

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [tip: x86/entry] x86/entry/entry_32: Route int3 through common_exception
  2020-02-25 21:36 ` [patch 09/10] x86/entry/entry_32: Route int3 through common_exception Thomas Gleixner
  2020-02-26 17:35   ` Frederic Weisbecker
@ 2020-02-27 14:15   ` tip-bot2 for Thomas Gleixner
  1 sibling, 0 replies; 45+ messages in thread
From: tip-bot2 for Thomas Gleixner @ 2020-02-27 14:15 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Thomas Gleixner, Frederic Weisbecker, Alexandre Chartre,
	Andy Lutomirski, x86, LKML

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

Commit-ID:     ac3607f92f70c762e24d0ae731168f7584de51ec
Gitweb:        https://git.kernel.org/tip/ac3607f92f70c762e24d0ae731168f7584de51ec
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Tue, 25 Feb 2020 22:36:45 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 27 Feb 2020 14:48:41 +01:00

x86/entry/entry_32: Route int3 through common_exception

int3 is not using the common_exception path for purely historical reasons,
but there is no reason to keep it the only exception which is different.

Make it use common_exception so the upcoming changes to autogenerate the
entry stubs do not have to special case int3.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200225220217.042369808@linutronix.de

---
 arch/x86/entry/entry_32.S | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index a8b4438..0753f48 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1683,14 +1683,8 @@ SYM_CODE_END(nmi)
 SYM_CODE_START(int3)
 	ASM_CLAC
 	pushl	$-1				# mark this as an int
-
-	SAVE_ALL switch_stacks=1
-	ENCODE_FRAME_POINTER
-	TRACE_IRQS_OFF
-	xorl	%edx, %edx			# zero error code
-	movl	%esp, %eax			# pt_regs pointer
-	call	do_int3
-	jmp	ret_from_exception
+	pushl	$do_int3
+	jmp	common_exception
 SYM_CODE_END(int3)
 
 SYM_CODE_START(general_protection)

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [tip: x86/entry] x86/traps: Stop using ist_enter/exit() in do_int3()
  2020-02-25 21:36 ` [patch 10/10] x86/traps: Stop using ist_enter/exit() in do_int3() Thomas Gleixner
@ 2020-02-27 14:15   ` tip-bot2 for Thomas Gleixner
  2020-02-27 14:33   ` tip-bot2 for Andy Lutomirski
  1 sibling, 0 replies; 45+ messages in thread
From: tip-bot2 for Thomas Gleixner @ 2020-02-27 14:15 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Andy Lutomirski, Thomas Gleixner, Alexandre Chartre, x86, LKML

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

Commit-ID:     009cae30b6cb2e0af56c8fa44d89d11ba89fb2d1
Gitweb:        https://git.kernel.org/tip/009cae30b6cb2e0af56c8fa44d89d11ba89fb2d1
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Tue, 25 Feb 2020 22:36:46 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 27 Feb 2020 14:48:41 +01:00

x86/traps: Stop using ist_enter/exit() in do_int3()

#BP is not longer using IST and using ist_enter() and ist_exit() makes it
harder to change ist_enter() and ist_exit()'s behavior.  Instead open-code
the very small amount of required logic.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200225220217.150607679@linutronix.de


---
 arch/x86/kernel/traps.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 7ffb6f4..c0bc9df 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -572,14 +572,20 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
 		return;
 
 	/*
-	 * Use ist_enter despite the fact that we don't use an IST stack.
-	 * We can be called from a kprobe in non-CONTEXT_KERNEL kernel
-	 * mode or even during context tracking state changes.
+	 * Unlike any other non-IST entry, we can be called from a kprobe in
+	 * non-CONTEXT_KERNEL kernel mode or even during context tracking
+	 * state changes.  Make sure that we wake up RCU even if we're coming
+	 * from kernel code.
 	 *
-	 * This means that we can't schedule.  That's okay.
+	 * This means that we can't schedule even if we came from a
+	 * preemptible kernel context.  That's okay.
 	 */
-	ist_enter(regs);
+	if (!user_mode(regs)) {
+		rcu_nmi_enter();
+		preempt_disable();
+	}
 	RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
+
 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
 	if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
 				SIGTRAP) == NOTIFY_STOP)
@@ -600,7 +606,10 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
 	cond_local_irq_disable(regs);
 
 exit:
-	ist_exit(regs);
+	if (!user_mode(regs)) {
+		preempt_enable_no_resched();
+		rcu_nmi_exit();
+	}
 }
 NOKPROBE_SYMBOL(do_int3);
 

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [tip: x86/entry] x86/traps: Document do_spurious_interrupt_bug()
  2020-02-25 21:36 ` [patch 05/10] x86/traps: Document do_spurious_interrupt_bug() Thomas Gleixner
  2020-02-26 17:08   ` Frederic Weisbecker
@ 2020-02-27 14:15   ` tip-bot2 for Thomas Gleixner
  1 sibling, 0 replies; 45+ messages in thread
From: tip-bot2 for Thomas Gleixner @ 2020-02-27 14:15 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Thomas Gleixner, Frederic Weisbecker, Alexandre Chartre,
	Andy Lutomirski, x86, LKML

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

Commit-ID:     d244d0e195bc12964bcf3b8eef45e715a7f203b0
Gitweb:        https://git.kernel.org/tip/d244d0e195bc12964bcf3b8eef45e715a7f203b0
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Tue, 25 Feb 2020 22:36:41 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 27 Feb 2020 14:48:40 +01:00

x86/traps: Document do_spurious_interrupt_bug()

Add a comment which explains why this empty handler for a reserved vector
exists.

Requested-by: Josh Poimboeuf <jpoimboe@redhat.com>

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200225220216.624165786@linutronix.de

---
 arch/x86/kernel/traps.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 474b8cb..7ffb6f4 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -862,6 +862,25 @@ do_simd_coprocessor_error(struct pt_regs *regs, long error_code)
 dotraplinkage void
 do_spurious_interrupt_bug(struct pt_regs *regs, long error_code)
 {
+	/*
+	 * This addresses a Pentium Pro Erratum:
+	 *
+	 * PROBLEM: If the APIC subsystem is configured in mixed mode with
+	 * Virtual Wire mode implemented through the local APIC, an
+	 * interrupt vector of 0Fh (Intel reserved encoding) may be
+	 * generated by the local APIC (Int 15).  This vector may be
+	 * generated upon receipt of a spurious interrupt (an interrupt
+	 * which is removed before the system receives the INTA sequence)
+	 * instead of the programmed 8259 spurious interrupt vector.
+	 *
+	 * IMPLICATION: The spurious interrupt vector programmed in the
+	 * 8259 is normally handled by an operating system's spurious
+	 * interrupt handler. However, a vector of 0Fh is unknown to some
+	 * operating systems, which would crash if this erratum occurred.
+	 *
+	 * In theory this could be limited to 32bit, but the handler is not
+	 * hurting and who knows which other CPUs suffer from this.
+	 */
 }
 
 dotraplinkage void

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [tip: x86/entry] x86/irq: Remove useless return value from do_IRQ()
  2020-02-25 21:36 ` [patch 07/10] x86/irq: Remove useless return value from do_IRQ() Thomas Gleixner
@ 2020-02-27 14:15   ` tip-bot2 for Thomas Gleixner
  0 siblings, 0 replies; 45+ messages in thread
From: tip-bot2 for Thomas Gleixner @ 2020-02-27 14:15 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Thomas Gleixner, Alexandre Chartre, Andy Lutomirski, x86, LKML

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

Commit-ID:     17dbedb5da184b501c5c51fc78d1071005139e48
Gitweb:        https://git.kernel.org/tip/17dbedb5da184b501c5c51fc78d1071005139e48
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Tue, 25 Feb 2020 22:36:43 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 27 Feb 2020 14:48:40 +01:00

x86/irq: Remove useless return value from do_IRQ()

Nothing is using it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200225220216.826870369@linutronix.de

---
 arch/x86/include/asm/irq.h | 2 +-
 arch/x86/kernel/irq.c      | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
index a176f61..72fba0e 100644
--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -36,7 +36,7 @@ extern void native_init_IRQ(void);
 
 extern void handle_irq(struct irq_desc *desc, struct pt_regs *regs);
 
-extern __visible unsigned int do_IRQ(struct pt_regs *regs);
+extern __visible void do_IRQ(struct pt_regs *regs);
 
 extern void init_ISA_irqs(void);
 
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 21efee3..c7965ff 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -230,7 +230,7 @@ u64 arch_irq_stat(void)
  * SMP cross-CPU interrupts have their own specific
  * handlers).
  */
-__visible unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
+__visible void __irq_entry do_IRQ(struct pt_regs *regs)
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
 	struct irq_desc * desc;
@@ -263,7 +263,6 @@ __visible unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
 	exiting_irq();
 
 	set_irq_regs(old_regs);
-	return 1;
 }
 
 #ifdef CONFIG_X86_LOCAL_APIC

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [tip: x86/entry] x86/traps: Remove redundant declaration of do_double_fault()
  2020-02-25 21:36 ` [patch 06/10] x86/traps: Remove redundant declaration of do_double_fault() Thomas Gleixner
@ 2020-02-27 14:15   ` tip-bot2 for Thomas Gleixner
  0 siblings, 0 replies; 45+ messages in thread
From: tip-bot2 for Thomas Gleixner @ 2020-02-27 14:15 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Thomas Gleixner, Alexandre Chartre, Andy Lutomirski, x86, LKML

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

Commit-ID:     3ba4f0a633ca4bfeadb24eba19cb53ebe246eabf
Gitweb:        https://git.kernel.org/tip/3ba4f0a633ca4bfeadb24eba19cb53ebe246eabf
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Tue, 25 Feb 2020 22:36:42 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 27 Feb 2020 14:48:40 +01:00

x86/traps: Remove redundant declaration of do_double_fault()



Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200225220216.720335354@linutronix.de

---
 arch/x86/include/asm/traps.h | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index e1c660b..c26a7e1 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -76,13 +76,6 @@ dotraplinkage void do_coprocessor_segment_overrun(struct pt_regs *regs, long err
 dotraplinkage void do_invalid_TSS(struct pt_regs *regs, long error_code);
 dotraplinkage void do_segment_not_present(struct pt_regs *regs, long error_code);
 dotraplinkage void do_stack_segment(struct pt_regs *regs, long error_code);
-#ifdef CONFIG_X86_64
-dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsigned long address);
-asmlinkage __visible notrace struct pt_regs *sync_regs(struct pt_regs *eregs);
-asmlinkage __visible notrace
-struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s);
-void __init trap_init(void);
-#endif
 dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code);
 dotraplinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address);
 dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *regs, long error_code);
@@ -94,6 +87,13 @@ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code);
 #endif
 dotraplinkage void do_mce(struct pt_regs *regs, long error_code);
 
+#ifdef CONFIG_X86_64
+asmlinkage __visible notrace struct pt_regs *sync_regs(struct pt_regs *eregs);
+asmlinkage __visible notrace
+struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s);
+void __init trap_init(void);
+#endif
+
 static inline int get_si_code(unsigned long condition)
 {
 	if (condition & DR_STEP)

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [tip: x86/entry] x86/mce: Disable tracing and kprobes on do_machine_check()
  2020-02-25 21:36 ` [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check() Thomas Gleixner
  2020-02-26  1:13   ` Frederic Weisbecker
  2020-02-26 11:18   ` Borislav Petkov
@ 2020-02-27 14:15   ` tip-bot2 for Andy Lutomirski
  2 siblings, 0 replies; 45+ messages in thread
From: tip-bot2 for Andy Lutomirski @ 2020-02-27 14:15 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Andy Lutomirski, Thomas Gleixner, Borislav Petkov,
	Alexandre Chartre, x86, LKML

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

Commit-ID:     55ba18d6ed37a28cf8b8ca79e9aef4cf98183bb7
Gitweb:        https://git.kernel.org/tip/55ba18d6ed37a28cf8b8ca79e9aef4cf98183bb7
Author:        Andy Lutomirski <luto@kernel.org>
AuthorDate:    Tue, 25 Feb 2020 22:36:38 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 27 Feb 2020 14:48:39 +01:00

x86/mce: Disable tracing and kprobes on do_machine_check()

do_machine_check() can be raised in almost any context including the most
fragile ones. Prevent kprobes and tracing.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200225220216.315548935@linutronix.de

---
 arch/x86/include/asm/traps.h   |  3 ---
 arch/x86/kernel/cpu/mce/core.c | 12 ++++++++++--
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index ffa0dc8..e1c660b 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -88,9 +88,6 @@ dotraplinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code,
 dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *regs, long error_code);
 dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code);
 dotraplinkage void do_alignment_check(struct pt_regs *regs, long error_code);
-#ifdef CONFIG_X86_MCE
-dotraplinkage void do_machine_check(struct pt_regs *regs, long error_code);
-#endif
 dotraplinkage void do_simd_coprocessor_error(struct pt_regs *regs, long error_code);
 #ifdef CONFIG_X86_32
 dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code);
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 2c4f949..32ecc59 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1213,8 +1213,14 @@ static void __mc_scan_banks(struct mce *m, struct mce *final,
  * On Intel systems this is entered on all CPUs in parallel through
  * MCE broadcast. However some CPUs might be broken beyond repair,
  * so be always careful when synchronizing with others.
+ *
+ * Tracing and kprobes are disabled: if we interrupted a kernel context
+ * with IF=1, we need to minimize stack usage.  There are also recursion
+ * issues: if the machine check was due to a failure of the memory
+ * backing the user stack, tracing that reads the user stack will cause
+ * potentially infinite recursion.
  */
-void do_machine_check(struct pt_regs *regs, long error_code)
+void notrace do_machine_check(struct pt_regs *regs, long error_code)
 {
 	DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
 	DECLARE_BITMAP(toclear, MAX_NR_BANKS);
@@ -1360,6 +1366,7 @@ out_ist:
 	ist_exit(regs);
 }
 EXPORT_SYMBOL_GPL(do_machine_check);
+NOKPROBE_SYMBOL(do_machine_check);
 
 #ifndef CONFIG_MEMORY_FAILURE
 int memory_failure(unsigned long pfn, int flags)
@@ -1892,10 +1899,11 @@ static void unexpected_machine_check(struct pt_regs *regs, long error_code)
 void (*machine_check_vector)(struct pt_regs *, long error_code) =
 						unexpected_machine_check;
 
-dotraplinkage void do_mce(struct pt_regs *regs, long error_code)
+dotraplinkage notrace void do_mce(struct pt_regs *regs, long error_code)
 {
 	machine_check_vector(regs, error_code);
 }
+NOKPROBE_SYMBOL(do_mce);
 
 /*
  * Called for each booted CPU to set up machine checks.

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [tip: x86/entry] x86/entry/32: Force MCE through do_mce()
  2020-02-25 21:36 ` [patch 03/10] x86/entry/32: Force MCE through do_mce() Thomas Gleixner
  2020-02-26  1:11   ` Frederic Weisbecker
@ 2020-02-27 14:15   ` tip-bot2 for Thomas Gleixner
  1 sibling, 0 replies; 45+ messages in thread
From: tip-bot2 for Thomas Gleixner @ 2020-02-27 14:15 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Thomas Gleixner, Frederic Weisbecker, Alexandre Chartre,
	Andy Lutomirski, x86, LKML

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

Commit-ID:     840371bea19e85f30d19909171248cf8c5845fd7
Gitweb:        https://git.kernel.org/tip/840371bea19e85f30d19909171248cf8c5845fd7
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Tue, 25 Feb 2020 22:36:39 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 27 Feb 2020 14:48:39 +01:00

x86/entry/32: Force MCE through do_mce()

Remove the pointless difference between 32 and 64 bit to make further
unifications simpler.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200225220216.428188397@linutronix.de

---
 arch/x86/entry/entry_32.S          | 2 +-
 arch/x86/include/asm/mce.h         | 3 ---
 arch/x86/kernel/cpu/mce/internal.h | 3 +++
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 39243df..a8b4438 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1365,7 +1365,7 @@ SYM_CODE_END(divide_error)
 SYM_CODE_START(machine_check)
 	ASM_CLAC
 	pushl	$0
-	pushl	machine_check_vector
+	pushl	$do_mce
 	jmp	common_exception
 SYM_CODE_END(machine_check)
 #endif
diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 4359b95..a7e0b9d 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -238,9 +238,6 @@ extern void mce_disable_bank(int bank);
 /*
  * Exception handler
  */
-
-/* Call the installed machine check handler for this CPU setup. */
-extern void (*machine_check_vector)(struct pt_regs *, long error_code);
 void do_machine_check(struct pt_regs *, long);
 
 /*
diff --git a/arch/x86/kernel/cpu/mce/internal.h b/arch/x86/kernel/cpu/mce/internal.h
index b785c0d..c1cda0b 100644
--- a/arch/x86/kernel/cpu/mce/internal.h
+++ b/arch/x86/kernel/cpu/mce/internal.h
@@ -8,6 +8,9 @@
 #include <linux/device.h>
 #include <asm/mce.h>
 
+/* Pointer to the installed machine check handler for this CPU setup. */
+extern void (*machine_check_vector)(struct pt_regs *, long error_code);
+
 enum severity_level {
 	MCE_NO_SEVERITY,
 	MCE_DEFERRED_SEVERITY,

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [tip: x86/entry] x86/entry/32: Add missing ASM_CLAC to general_protection entry
  2020-02-25 21:36 ` [patch 01/10] x86/entry/32: Add missing ASM_CLAC to general_protection entry Thomas Gleixner
  2020-02-26  1:00   ` Frederic Weisbecker
@ 2020-02-27 14:15   ` tip-bot2 for Thomas Gleixner
  1 sibling, 0 replies; 45+ messages in thread
From: tip-bot2 for Thomas Gleixner @ 2020-02-27 14:15 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Thomas Gleixner, Frederic Weisbecker, Alexandre Chartre,
	Andy Lutomirski, stable, x86, LKML

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

Commit-ID:     3d51507f29f2153a658df4a0674ec5b592b62085
Gitweb:        https://git.kernel.org/tip/3d51507f29f2153a658df4a0674ec5b592b62085
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Tue, 25 Feb 2020 22:36:37 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 27 Feb 2020 14:48:38 +01:00

x86/entry/32: Add missing ASM_CLAC to general_protection entry

All exception entry points must have ASM_CLAC right at the
beginning. The general_protection entry is missing one.

Fixes: e59d1b0a2419 ("x86-32, smap: Add STAC/CLAC instructions to 32-bit kernel entry")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200225220216.219537887@linutronix.de

---
 arch/x86/entry/entry_32.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 7e05604..39243df 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1694,6 +1694,7 @@ SYM_CODE_START(int3)
 SYM_CODE_END(int3)
 
 SYM_CODE_START(general_protection)
+	ASM_CLAC
 	pushl	$do_general_protection
 	jmp	common_exception
 SYM_CODE_END(general_protection)

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [patch V2 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries
  2020-02-26 19:15         ` Thomas Gleixner
@ 2020-02-27 14:24           ` Thomas Gleixner
  2020-02-29 11:49             ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
  0 siblings, 1 reply; 45+ messages in thread
From: Thomas Gleixner @ 2020-02-27 14:24 UTC (permalink / raw)
  To: Andy Lutomirski
  Cc: LKML, X86 ML, Steven Rostedt, Brian Gerst, Juergen Gross,
	Paolo Bonzini, Arnd Bergmann

Nothing cares about the -1 "mark as interrupt" in the errorcode of
exception entries. It's only used to fill the error code when a signal
is delivered, but this is already inconsistent vs. 64 bit as there all
exceptions which do not have an error code set it to 0. So if 32bit
applications would care about this, then they would have noticed more
than a decade ago.

Just use 0 for all excpetions which do not have an errorcode consistently.

This does neither break /proc/$PID/syscall because this interface
examines the error code / syscall number which is on the stack and that
is set to -1 (no syscall) in common_exception unconditionally for all
exceptions. The push in the entry stub is just there to fill the
hardware error code slot on the stack for consistency of the stack
layout.

A transient observation of 0 is possible, but that's true for the other
exceptions which use 0 already as well and that interface is an unreliable
snapshot of dubious correctness anyway.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
---
V2: Amend changelog. Rebased on top of tip x86/entry 
---
 arch/x86/entry/entry_32.S |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1290,7 +1290,7 @@ SYM_CODE_END(simd_coprocessor_error)
 
 SYM_CODE_START(device_not_available)
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 	pushl	$do_device_not_available
 	jmp	common_exception
 SYM_CODE_END(device_not_available)
@@ -1531,7 +1531,7 @@ SYM_CODE_START(debug)
 	 * Entry from sysenter is now handled in common_exception
 	 */
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 	pushl	$do_debug
 	jmp	common_exception
 SYM_CODE_END(debug)
@@ -1682,7 +1682,7 @@ SYM_CODE_END(nmi)
 
 SYM_CODE_START(int3)
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 	pushl	$do_int3
 	jmp	common_exception
 SYM_CODE_END(int3)

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [tip: x86/entry] x86/traps: Stop using ist_enter/exit() in do_int3()
  2020-02-25 21:36 ` [patch 10/10] x86/traps: Stop using ist_enter/exit() in do_int3() Thomas Gleixner
  2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
@ 2020-02-27 14:33   ` tip-bot2 for Andy Lutomirski
  1 sibling, 0 replies; 45+ messages in thread
From: tip-bot2 for Andy Lutomirski @ 2020-02-27 14:33 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Andy Lutomirski, Thomas Gleixner, Alexandre Chartre, x86, LKML

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

Commit-ID:     65c668f5faebf549db086b7a6841b6f4187b4e4f
Gitweb:        https://git.kernel.org/tip/65c668f5faebf549db086b7a6841b6f4187b4e4f
Author:        Andy Lutomirski <luto@kernel.org>
AuthorDate:    Tue, 25 Feb 2020 22:36:46 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 27 Feb 2020 15:28:39 +01:00

x86/traps: Stop using ist_enter/exit() in do_int3()

#BP is not longer using IST and using ist_enter() and ist_exit() makes it
harder to change ist_enter() and ist_exit()'s behavior.  Instead open-code
the very small amount of required logic.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200225220217.150607679@linutronix.de


---
 arch/x86/kernel/traps.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 7ffb6f4..c0bc9df 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -572,14 +572,20 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
 		return;
 
 	/*
-	 * Use ist_enter despite the fact that we don't use an IST stack.
-	 * We can be called from a kprobe in non-CONTEXT_KERNEL kernel
-	 * mode or even during context tracking state changes.
+	 * Unlike any other non-IST entry, we can be called from a kprobe in
+	 * non-CONTEXT_KERNEL kernel mode or even during context tracking
+	 * state changes.  Make sure that we wake up RCU even if we're coming
+	 * from kernel code.
 	 *
-	 * This means that we can't schedule.  That's okay.
+	 * This means that we can't schedule even if we came from a
+	 * preemptible kernel context.  That's okay.
 	 */
-	ist_enter(regs);
+	if (!user_mode(regs)) {
+		rcu_nmi_enter();
+		preempt_disable();
+	}
 	RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
+
 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
 	if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
 				SIGTRAP) == NOTIFY_STOP)
@@ -600,7 +606,10 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
 	cond_local_irq_disable(regs);
 
 exit:
-	ist_exit(regs);
+	if (!user_mode(regs)) {
+		preempt_enable_no_resched();
+		rcu_nmi_exit();
+	}
 }
 NOKPROBE_SYMBOL(do_int3);
 

^ permalink raw reply	[flat|nested] 45+ messages in thread

* [tip: x86/entry] x86/entry/32: Remove the 0/-1 distinction from exception entries
  2020-02-27 14:24           ` [patch V2 " Thomas Gleixner
@ 2020-02-29 11:49             ` tip-bot2 for Thomas Gleixner
  0 siblings, 0 replies; 45+ messages in thread
From: tip-bot2 for Thomas Gleixner @ 2020-02-29 11:49 UTC (permalink / raw)
  To: linux-tip-commits; +Cc: Thomas Gleixner, Alexandre Chartre, x86, LKML

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

Commit-ID:     e441a2ae0e9e9bb12fd3fbe2d59d923fadfe8ef7
Gitweb:        https://git.kernel.org/tip/e441a2ae0e9e9bb12fd3fbe2d59d923fadfe8ef7
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Thu, 27 Feb 2020 15:24:29 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sat, 29 Feb 2020 12:45:54 +01:00

x86/entry/32: Remove the 0/-1 distinction from exception entries

Nothing cares about the -1 "mark as interrupt" in the errorcode of
exception entries. It's only used to fill the error code when a signal is
delivered, but this is already inconsistent vs. 64 bit as there all
exceptions which do not have an error code set it to 0. So if 32 bit
applications would care about this, then they would have noticed more than
a decade ago.

Just use 0 for all excpetions which do not have an errorcode consistently.

This does neither break /proc/$PID/syscall because this interface examines
the error code / syscall number which is on the stack and that is set to -1
(no syscall) in common_exception unconditionally for all exceptions. The
push in the entry stub is just there to fill the hardware error code slot
on the stack for consistency of the stack layout.

A transient observation of 0 is possible, but that's true for the other
exceptions which use 0 already as well and that interface is an unreliable
snapshot of dubious correctness anyway.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Link: https://lkml.kernel.org/r/87mu94m7ky.fsf@nanos.tec.linutronix.de

---
 arch/x86/entry/entry_32.S | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 0753f48..ddc87f2 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1290,7 +1290,7 @@ SYM_CODE_END(simd_coprocessor_error)
 
 SYM_CODE_START(device_not_available)
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 	pushl	$do_device_not_available
 	jmp	common_exception
 SYM_CODE_END(device_not_available)
@@ -1531,7 +1531,7 @@ SYM_CODE_START(debug)
 	 * Entry from sysenter is now handled in common_exception
 	 */
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 	pushl	$do_debug
 	jmp	common_exception
 SYM_CODE_END(debug)
@@ -1682,7 +1682,7 @@ SYM_CODE_END(nmi)
 
 SYM_CODE_START(int3)
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 	pushl	$do_int3
 	jmp	common_exception
 SYM_CODE_END(int3)

^ permalink raw reply	[flat|nested] 45+ messages in thread

end of thread, other threads:[~2020-02-29 11:49 UTC | newest]

Thread overview: 45+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
2020-02-25 21:36 ` [patch 01/10] x86/entry/32: Add missing ASM_CLAC to general_protection entry Thomas Gleixner
2020-02-26  1:00   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check() Thomas Gleixner
2020-02-26  1:13   ` Frederic Weisbecker
2020-02-26  5:29     ` Andy Lutomirski
2020-02-26 13:28       ` Peter Zijlstra
2020-02-26 15:10         ` Andy Lutomirski
2020-02-26 16:08           ` Peter Zijlstra
2020-02-26 17:28             ` Andy Lutomirski
2020-02-26 18:42               ` Borislav Petkov
2020-02-26 18:59                 ` Peter Zijlstra
2020-02-26 19:09                   ` Andy Lutomirski
2020-02-26 20:59                     ` Steven Rostedt
2020-02-26 11:18   ` Borislav Petkov
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Andy Lutomirski
2020-02-25 21:36 ` [patch 03/10] x86/entry/32: Force MCE through do_mce() Thomas Gleixner
2020-02-26  1:11   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 04/10] x86/traps: Remove pointless irq enable from do_spurious_interrupt_bug() Thomas Gleixner
2020-02-26  1:19   ` Frederic Weisbecker
2020-02-25 21:36 ` [patch 05/10] x86/traps: Document do_spurious_interrupt_bug() Thomas Gleixner
2020-02-26 17:08   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 06/10] x86/traps: Remove redundant declaration of do_double_fault() Thomas Gleixner
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 07/10] x86/irq: Remove useless return value from do_IRQ() Thomas Gleixner
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries Thomas Gleixner
2020-02-26  5:34   ` Andy Lutomirski
2020-02-26 18:42     ` Thomas Gleixner
2020-02-26 18:57       ` Andy Lutomirski
2020-02-26 19:15         ` Thomas Gleixner
2020-02-27 14:24           ` [patch V2 " Thomas Gleixner
2020-02-29 11:49             ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 09/10] x86/entry/entry_32: Route int3 through common_exception Thomas Gleixner
2020-02-26 17:35   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 10/10] x86/traps: Stop using ist_enter/exit() in do_int3() Thomas Gleixner
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-27 14:33   ` tip-bot2 for Andy Lutomirski
2020-02-26  5:26 ` [patch 00/10] x86/entry: Consolidation - Part I Andy Lutomirski
2020-02-26  5:35 ` Andy Lutomirski
2020-02-27 11:01 ` Alexandre Chartre

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