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:
- 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.
- 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