diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2014-12-10 12:09:26 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-12-10 12:09:26 -0800 |
| commit | 9d0cf6f56454c8a71e0aa2c3b9c6cbe470eb2788 (patch) | |
| tree | e13191d786b097bc6d81e41b2ae7f66f8c1ccb74 /arch/x86/include | |
| parent | d82012695ef29e4e1c8153ccf43098ec8e50369e (diff) | |
| parent | 3736708f034ae1e8c62789ed737e8b90d5b40210 (diff) | |
Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 asm updates from Ingo Molnar:
"Misc changes:
- context switch micro-optimization
- debug printout micro-optimization
- comment enhancements and typo fix"
* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86: Replace seq_printf() with seq_puts()
x86/asm: Fix typo in arch/x86/kernel/asm_offset_64.c
sched/x86: Add a comment clarifying LDT context switching
sched/x86_64: Don't save flags on context switch
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/mmu_context.h | 11 | ||||
| -rw-r--r-- | arch/x86/include/asm/switch_to.h | 12 |
2 files changed, 18 insertions, 5 deletions
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index be91d5736e08..40269a2bf6f9 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -52,7 +52,16 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, /* Stop flush ipis for the previous mm */ cpumask_clear_cpu(cpu, mm_cpumask(prev)); - /* Load the LDT, if the LDT is different: */ + /* + * Load the LDT, if the LDT is different. + * + * It's possible leave_mm(prev) has been called. If so, + * then prev->context.ldt could be out of sync with the + * LDT descriptor or the LDT register. This can only happen + * if prev->context.ldt is non-null, since we never free + * an LDT. But LDTs can't be shared across mms, so + * prev->context.ldt won't be equal to next->context.ldt. + */ if (unlikely(prev->context.ldt != next->context.ldt)) load_LDT_nolock(&next->context); } diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h index d7f3b3b78ac3..751bf4b7bf11 100644 --- a/arch/x86/include/asm/switch_to.h +++ b/arch/x86/include/asm/switch_to.h @@ -79,12 +79,12 @@ do { \ #else /* CONFIG_X86_32 */ /* frame pointer must be last for get_wchan */ -#define SAVE_CONTEXT "pushf ; pushq %%rbp ; movq %%rsi,%%rbp\n\t" -#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp ; popf\t" +#define SAVE_CONTEXT "pushq %%rbp ; movq %%rsi,%%rbp\n\t" +#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp\t" #define __EXTRA_CLOBBER \ , "rcx", "rbx", "rdx", "r8", "r9", "r10", "r11", \ - "r12", "r13", "r14", "r15" + "r12", "r13", "r14", "r15", "flags" #ifdef CONFIG_CC_STACKPROTECTOR #define __switch_canary \ @@ -100,7 +100,11 @@ do { \ #define __switch_canary_iparam #endif /* CC_STACKPROTECTOR */ -/* Save restore flags to clear handle leaking NT */ +/* + * There is no need to save or restore flags, because flags are always + * clean in kernel mode, with the possible exception of IOPL. Kernel IOPL + * has no effect. + */ #define switch_to(prev, next, last) \ asm volatile(SAVE_CONTEXT \ "movq %%rsp,%P[threadrsp](%[prev])\n\t" /* save RSP */ \ |