diff options
| author | Jeremy Fitzhardinge <jeremy@goop.org> | 2009-09-03 12:27:15 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-09-03 21:30:51 +0200 |
| commit | 1ea0d14e480c245683927eecc03a70faf06e80c8 (patch) | |
| tree | cc43a6966799aa55c0f076c1217c557fb107563c /arch/x86/include/asm | |
| parent | 23386d63bbb3199cf247313ec088878d72debcfd (diff) | |
x86/i386: Make sure stack-protector segment base is cache aligned
The Intel Optimization Reference Guide says:
In Intel Atom microarchitecture, the address generation unit
assumes that the segment base will be 0 by default. Non-zero
segment base will cause load and store operations to experience
a delay.
- If the segment base isn't aligned to a cache line
boundary, the max throughput of memory operations is
reduced to one [e]very 9 cycles.
[...]
Assembly/Compiler Coding Rule 15. (H impact, ML generality)
For Intel Atom processors, use segments with base set to 0
whenever possible; avoid non-zero segment base address that is
not aligned to cache line boundary at all cost.
We can't avoid having a non-zero base for the stack-protector
segment, but we can make it cache-aligned.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: <stable@kernel.org>
LKML-Reference: <4AA01893.6000507@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/include/asm')
| -rw-r--r-- | arch/x86/include/asm/processor.h | 12 | ||||
| -rw-r--r-- | arch/x86/include/asm/stackprotector.h | 4 | ||||
| -rw-r--r-- | arch/x86/include/asm/system.h | 2 |
3 files changed, 14 insertions, 4 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index c7768269b1cf..e597ecc8753c 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -403,7 +403,17 @@ extern unsigned long kernel_eflags; extern asmlinkage void ignore_sysret(void); #else /* X86_64 */ #ifdef CONFIG_CC_STACKPROTECTOR -DECLARE_PER_CPU(unsigned long, stack_canary); +/* + * Make sure stack canary segment base is cached-aligned: + * "For Intel Atom processors, avoid non zero segment base address + * that is not aligned to cache line boundary at all cost." + * (Optim Ref Manual Assembly/Compiler Coding Rule 15.) + */ +struct stack_canary { + char __pad[20]; /* canary at %gs:20 */ + unsigned long canary; +}; +DECLARE_PER_CPU(struct stack_canary, stack_canary) ____cacheline_aligned; #endif #endif /* X86_64 */ diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h index 44efdff3975d..157517763565 100644 --- a/arch/x86/include/asm/stackprotector.h +++ b/arch/x86/include/asm/stackprotector.h @@ -78,14 +78,14 @@ static __always_inline void boot_init_stack_canary(void) #ifdef CONFIG_X86_64 percpu_write(irq_stack_union.stack_canary, canary); #else - percpu_write(stack_canary, canary); + percpu_write(stack_canary.canary, canary); #endif } static inline void setup_stack_canary_segment(int cpu) { #ifdef CONFIG_X86_32 - unsigned long canary = (unsigned long)&per_cpu(stack_canary, cpu) - 20; + unsigned long canary = (unsigned long)&per_cpu(stack_canary, cpu); struct desc_struct *gdt_table = get_cpu_gdt_table(cpu); struct desc_struct desc; diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h index 75c49c782e20..f08f97374892 100644 --- a/arch/x86/include/asm/system.h +++ b/arch/x86/include/asm/system.h @@ -31,7 +31,7 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, "movl %P[task_canary](%[next]), %%ebx\n\t" \ "movl %%ebx, "__percpu_arg([stack_canary])"\n\t" #define __switch_canary_oparam \ - , [stack_canary] "=m" (per_cpu_var(stack_canary)) + , [stack_canary] "=m" (per_cpu_var(stack_canary.canary)) #define __switch_canary_iparam \ , [task_canary] "i" (offsetof(struct task_struct, stack_canary)) #else /* CC_STACKPROTECTOR */ |