From bfd170d56505bf21cb636b0f1f169eaa815bdfe4 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 2 Aug 2012 11:49:43 +0400 Subject: [PATCH] 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 --- arch/arm/include/asm/ptrace.h | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h index 355ece5..44fe998 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__ */ -- 2.7.4