* Paolo Ornati <[email protected]> wrote:
> Wow, now I can reproduce it easly :)
>
> Just run under "gdb" a program that segfaults:
>
> void main(void)
> {
> *(int*)(0) = 1;
> }
>
> and it will trigger.
thanks - please try the fix below - it has solved the problem on my
testbox.
Ingo
-------------
Subject: irqflags tracing: fix x86_64 entry/exit
From: Ingo Molnar <[email protected]>
the x86_64 portion of the irqflags code did not properly trace the
"paranoid userspace" type of syscall/ptrace exit variant.
A testcase Paolo Ornati has discovered triggers a lock validator
assert due to this bug.
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86_64/kernel/entry.S | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
Index: linux/arch/x86_64/kernel/entry.S
===================================================================
--- linux.orig/arch/x86_64/kernel/entry.S
+++ linux/arch/x86_64/kernel/entry.S
@@ -50,9 +50,10 @@
#define retint_kernel retint_restore_args
#endif
-.macro TRACE_IRQS_IRETQ
+
+.macro TRACE_IRQS_IRETQ offset=ARGOFFSET
#ifdef CONFIG_TRACE_IRQFLAGS
- bt $9,EFLAGS-ARGOFFSET(%rsp) /* interrupts off? */
+ bt $9,EFLAGS-\offset(%rsp) /* interrupts off? */
jnc 1f
TRACE_IRQS_ON
1:
@@ -809,9 +810,9 @@ error_exit:
andl %edi,%edx
jnz retint_careful
/*
- * The iret will restore flags:
+ * The iret might restore flags:
*/
- TRACE_IRQS_ON
+ TRACE_IRQS_IRETQ
swapgs
RESTORE_ARGS 0,8,0
jmp iret_label
@@ -999,6 +1000,7 @@ paranoid_exit:
testl $3,CS(%rsp)
jnz paranoid_userspace
paranoid_swapgs:
+ TRACE_IRQS_IRETQ 0
swapgs
paranoid_restore:
RESTORE_ALL 8
-
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