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| author | Al Viro <viro@zeniv.linux.org.uk> | 2012-08-02 11:49:43 +0400 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2012-09-30 22:21:37 -0400 |
| commit | bfd170d56505bf21cb636b0f1f169eaa815bdfe4 (patch) | |
| tree | 9a783a04a5b8e013af113704c3d4b51a6db77cd2 | |
| parent | 583d632fb3f6d7e9d133a7260829dd7565f8cc99 (diff) | |
| download | linux-bfd170d56505bf21cb636b0f1f169eaa815bdfe4.tar.bz2 | |
arm: optimized current_pt_regs()
... no need to read current_thread_info()->task only to
feed it to task_thread_page() immediately afterwards.
Moreover, not using current_thread_info() at all ends
up with better assembler - we need a location very close
to the top of kernel stack page and it's actually better
to do or with 0x1fff, followed be subtracting a small
constant than and with ~0x1fff, followed by adding a large
one. Both & and | would be a couple of insns (mvn lsr/mvn lsl
for |, a pair of bic for &), but the following addition
would cost a pair of add while the subtraction ends up
as a single sub.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
| -rw-r--r-- | arch/arm/include/asm/ptrace.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h index 355ece523f41..44fe998269d9 100644 --- a/arch/arm/include/asm/ptrace.h +++ b/arch/arm/include/asm/ptrace.h @@ -254,6 +254,11 @@ static inline unsigned long user_stack_pointer(struct pt_regs *regs) return regs->ARM_sp; } +#define current_pt_regs(void) ({ \ + register unsigned long sp asm ("sp"); \ + (struct pt_regs *)((sp | (THREAD_SIZE - 1)) - 7) - 1; \ +}) + #endif /* __KERNEL__ */ #endif /* __ASSEMBLY__ */ |