Messages in this thread Patch in this message | | | Date | Mon, 20 Jan 2014 18:05:14 +0100 | Subject | Re: [PATCH] ARM64: perf: support dwarf unwinding in compat mode | From | Jean Pihet <> |
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Hi Will,
Here is an updated version of the change, which uses compat_sp at only one place. The drawback is that compat_user_mode is checked when calling compat_user_stack_pointer, which seems unnecessary. Unfortunately the check is not optimized out by the complier as I could check with objdump -S.
What do you think?
diff --git a/arch/arm64/include/asm/compat.h b/arch/arm64/include/asm/compat.h index fda2704..e71f81f 100644 --- a/arch/arm64/include/asm/compat.h +++ b/arch/arm64/include/asm/compat.h @@ -228,7 +228,7 @@ static inline compat_uptr_t ptr_to_compat(void __user *uptr) return (u32)(unsigned long)uptr; }
-#define compat_user_stack_pointer() (current_pt_regs()->compat_sp) +#define compat_user_stack_pointer() (user_stack_pointer(current_pt_regs()))
static inline void __user *arch_compat_alloc_user_space(long len) { diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index fbb0020..86d5b54 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -133,7 +133,7 @@ struct pt_regs { (!((regs)->pstate & PSR_F_BIT))
#define user_stack_pointer(regs) \ - ((regs)->sp) + (!compat_user_mode(regs)) ? ((regs)->sp) : ((regs)->compat_sp)
/* * Are the current registers suitable for user mode? (used to maintain
Regards, Jean
On 17 January 2014 11:07, Will Deacon <will.deacon@arm.com> wrote: > On Fri, Jan 17, 2014 at 09:00:09AM +0000, Jean Pihet wrote: >> On 16 January 2014 14:47, Jean Pihet <jean.pihet@linaro.org> wrote: >> >> So the simplest thing would be to make compat_user_stack_pointer expand to >> >> user_stack_pointer(current_pt_regs()) on arm64 and merge that in with your >> >> original patch fixing user_stack_pointer. >> >> I see 2 issues in your proposal: >> >> 1) user_stack_pointer(regs) calls compat_user_stack_pointer if >> compat_user_mode(regs)) and compat_user_stack_pointer expands to >> user_stack_pointer. I see a circular dependency in the macros. > > Not today it doesn't, so you just need to avoid writing the circular > dependency and instead make user_stack_pointer access (regs)->compat_sp > instead. > >> 2) current_pt_regs() returns the current task regs although perf >> passes a regs struct that had been recorded previously. > > Yes, but compat_user_stack_pointer doesn't take a regs paramater anyway, so > there's no change in behaviour here. > > Will
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