Messages in this thread Patch in this message | | | Date | Fri, 19 Feb 2016 10:30:09 +0800 | Subject | Re: [PATCH] arm64: add architecture specified current_pt_regs | From | Zhi-zhou <> |
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On Thu, Feb 18, 2016 at 7:58 PM, Catalin Marinas <catalin.marinas@arm.com> wrote: > > On Thu, Feb 18, 2016 at 07:48:35PM +0800, Zhi-zhou Zhang wrote: > > From: zhizhou <zhizhou.zh@gmail.com> > > > > This patch is based on the implementation of arm. The generic > > current_pt_regs is implemented with current->stack. It need to access > > memory that would be too expensive. > > Do you have any performance numbers?
I'm using QEMU, so no. Actually this macro isn't heavily used. I just think using the generic implementation is not very nice. It get task_struct from sp_el0, then get stack(which is equal to sp_el0) from task_struct. There are two unnecessary memory accesses. > > > > diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h > > index e9e5467..1865d54 100644 > > --- a/arch/arm64/include/asm/ptrace.h > > +++ b/arch/arm64/include/asm/ptrace.h > > @@ -185,5 +185,9 @@ static inline int valid_user_regs(struct user_pt_regs *regs) > > > > extern unsigned long profile_pc(struct pt_regs *regs); > > > > +#define current_pt_regs(void) ({ (struct pt_regs *) \ > > + ((current_stack_pointer | (THREAD_SIZE - 1)) - 0xf) - 1; \ > > +}) > > I don't think this works well with the separate IRQ stack that we merged > in 4.5-rc1. current_thread_info() explicitly uses "sp_el0" while > current_stack_pointer is just "sp" (though I don't think we ever use > current_pt_regs in interrupt context). > Thank you, that's a problem. So how about write it like this?
diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index e9e5467..b68e01c 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -185,5 +185,10 @@ static inline int valid_user_regs(struct user_pt_regs *regs)
extern unsigned long profile_pc(struct pt_regs *regs);
+#define current_pt_regs(void) ({ (struct pt_regs *) \ + (((unsigned long)current_thread_info() | \ + (THREAD_SIZE - 1)) - 0xf) - 1; \ +}) + #endif /* __ASSEMBLY__ */ #endif > -- > Catalin
-- Regards, Zhi-zhou
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