x86: update canary handling during switch

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>

1 files changed, 9 insertions, 6 deletions

diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h
index 52eb748a68af..2fcc70bc85f3 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