[PATCH 01/10] x86: update canary handling during switch

Tejun Heo
2009-01-21T08:46:43Z

Impact: cleanup

In switch_to(), instead of taking offset to irq_stack_union.stack,
make it a proper percpu access using __percpu_arg() and per_cpu_var().

Signed-off-by: Tejun Heo <tj@kernel.org>
---
arch/x86/include/asm/system.h | 15 +++++++++------
1 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h
index 52eb748..2fcc70b 100644
--- a/arch/x86/include/asm/system.h
+++ b/arch/x86/include/asm/system.h
@@ -89,13 +89,15 @@ do { \
#ifdef CONFIG_CC_STACKPROTECTOR
#define __switch_canary \
"movq %P[task_canary](%%rsi),%%r8\n\t" \
- "movq %%r8,%%gs:%P[gs_canary]\n\t"
-#define __switch_canary_param \
- , [task_canary] "i" (offsetof(struct task_struct, stack_canary)) \
- , [gs_canary] "i" (offsetof(union irq_stack_union, stack_canary))
+ "movq %%r8,"__percpu_arg([gs_canary])"\n\t"
+#define __switch_canary_oparam \
+ , [gs_canary] "=m" (per_cpu_var(irq_stack_union.stack_canary))
+#define __switch_canary_iparam \
+ , [task_canary] "i" (offsetof(struct task_struct, stack_canary))
#else /* CC_STACKPROTECTOR */
#define __switch_canary
-#define __switch_canary_param
+#define __switch_canary_oparam
+#define __switch_canary_iparam
#endif /* CC_STACKPROTECTOR */

/* Save restore flags to clear handle leaking NT */
@@ -114,13 +116,14 @@ do { \
"jc ret_from_fork\n\t" \
RESTORE_CONTEXT \
: "=a" (last) \
+ __switch_canary_oparam \
: [next] "S" (next), [prev] "D" (prev), \
[threadrsp] "i" (offsetof(struct task_struct, thread.sp)), \
[ti_flags] "i" (offsetof(struct thread_info, flags)), \
[tif_fork] "i" (TIF_FORK), \
[thread_info] "i" (offsetof(struct task_struct, stack)), \
[current_task] "m" (per_cpu_var(current_task)) \
- __switch_canary_param \
+ __switch_canary_iparam \
: "memory", "cc" __EXTRA_CLOBBER)
#endif

--
1.6.0.2