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| author | Tejun Heo <tj@kernel.org> | 2009-01-20 03:29:19 (GMT) |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2009-01-20 03:29:19 (GMT) |
| commit | b4a8f7a262e79ecb0b39beb1449af524a78887f8 (patch) | |
| tree | 57d583acc09285170a7a364e6fb4a42b1fec0a98 | |
| parent | c6e50f93db5bd0895ec7c7d1b6f3886c6e1f11b6 (diff) | |
| download | linux-b4a8f7a262e79ecb0b39beb1449af524a78887f8.tar.xz | |
x86: conditionalize stack canary handling in hot path
Impact: no unnecessary stack canary swapping during context switch
There's no point in moving stack_canary around during context switch
if it's not enabled. Conditionalize it.
Signed-off-by: Tejun Heo <tj@kernel.org>
| -rw-r--r-- | arch/x86/include/asm/system.h | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h index 8cadfe9..b77bd8b 100644 --- a/arch/x86/include/asm/system.h +++ b/arch/x86/include/asm/system.h @@ -86,17 +86,28 @@ do { \ , "rcx", "rbx", "rdx", "r8", "r9", "r10", "r11", \ "r12", "r13", "r14", "r15" +#ifdef CONFIG_CC_STACKPROTECTOR +#define __switch_canary \ + "movq %P[task_canary](%%rsi),%%r8\n\t" \ + "movq %%r8,%%gs:%P[pda_canary]\n\t" +#define __switch_canary_param \ + , [task_canary] "i" (offsetof(struct task_struct, stack_canary)) \ + , [pda_canary] "i" (offsetof(struct x8664_pda, stack_canary)) +#else /* CC_STACKPROTECTOR */ +#define __switch_canary +#define __switch_canary_param +#endif /* CC_STACKPROTECTOR */ + /* Save restore flags to clear handle leaking NT */ #define switch_to(prev, next, last) \ - asm volatile(SAVE_CONTEXT \ + asm volatile(SAVE_CONTEXT \ "movq %%rsp,%P[threadrsp](%[prev])\n\t" /* save RSP */ \ "movq %P[threadrsp](%[next]),%%rsp\n\t" /* restore RSP */ \ "call __switch_to\n\t" \ ".globl thread_return\n" \ "thread_return:\n\t" \ "movq "__percpu_arg([current_task])",%%rsi\n\t" \ - "movq %P[task_canary](%%rsi),%%r8\n\t" \ - "movq %%r8,%%gs:%P[pda_canary]\n\t" \ + __switch_canary \ "movq %P[thread_info](%%rsi),%%r8\n\t" \ LOCK_PREFIX "btr %[tif_fork],%P[ti_flags](%%r8)\n\t" \ "movq %%rax,%%rdi\n\t" \ @@ -108,9 +119,8 @@ do { \ [ti_flags] "i" (offsetof(struct thread_info, flags)), \ [tif_fork] "i" (TIF_FORK), \ [thread_info] "i" (offsetof(struct task_struct, stack)), \ - [task_canary] "i" (offsetof(struct task_struct, stack_canary)),\ - [current_task] "m" (per_cpu_var(current_task)), \ - [pda_canary] "i" (offsetof(struct x8664_pda, stack_canary))\ + [current_task] "m" (per_cpu_var(current_task)) \ + __switch_canary_param \ : "memory", "cc" __EXTRA_CLOBBER) #endif |