asm-generic/ptrace.h: add a comment about frame_pointer

PATCH New Dmitry V. Levin 1 participant 1 message Dec 10, 2018 Generic include/asm header files

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Dmitry V. Levin

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2018-12-10 21:31 UTC #0 lore raw

PATCH 1/1 asm-generic/ptrace.h: add a comment about frame_pointer

I have been misled by comments in asm-generic/ptrace.h into thinking that frame_pointer() is universally available across architectures, which resulted in a wrong design decision.

Add a comment about frame_pointer in a hope that it will help others to avoid this mistake in the future.

Cc Oleg Nesterov <[email protected]>

Cc Arnd Bergmann <[email protected]>

Cc [email protected]

Signed-off-by Dmitry V. Levin <[email protected]>

---
 include/asm-generic/ptrace.h | 4 ++++
 1 file changed, 4 insertions(+)

include/asm-generic/ptrace.h +4 -0

index 82e674f6b337..3186c30bd50d 100644
@@ -59,6 +59,10 @@ static inline void user_stack_pointer_set(struct pt_regs *regs,
 #define SET_FP(regs, val) (GET_FP(regs) = (val))
 #endif
 
+/*
+ * Unlike instruction_pointer and user_stack_pointer,
+ * frame_pointer is not universally available across architectures.
+ */
 static inline unsigned long frame_pointer(struct pt_regs *regs)
 {
 	return GET_FP(regs);

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