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>

diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h
index 52eb748a68af68fc48c480d85bac01e42494ad53..2fcc70bc85f3b52950f7b731c67bdb93a38cf552 100644 (file)
--- 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