* Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> > > Add UNWIND_HINT_FUNC on kretporbe_trampoline code so that ORC > information is generated on the kretprobe_trampoline correctly. What is a 'kretporbe'? > Note that when the CONFIG_FRAME_POINTER=y, since the > kretprobe_trampoline skips updating frame pointer, the stack frame > of the kretprobe_trampoline seems non-standard. So this marks it > is STACK_FRAME_NON_STANDARD() and undefine UNWIND_HINT_FUNC. What does 'marks it is' mean? 'undefine' UNWIND_HINT_FUNC? Doesn't the patch do the exact opposite: > +#define UNWIND_HINT_FUNC \ > + UNWIND_HINT(ORC_REG_SP, 8, UNWIND_HINT_TYPE_FUNC, 0) But it does undefine it in a specific spot: > Anyway, with the frame pointer, FP unwinder can unwind the stack > frame correctly without that hint. > > Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> > Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> > Tested-by: Andrii Nakryik <andrii@xxxxxxxxxx> I have to say these changelogs are very careless. > +#else > + In headers, in longer CPP blocks, please always mark the '#else' branch with what it is the else branch of. See the output of: kepler:~/tip> git grep '#else' arch/x86/include/asm/ | head > +#ifdef CONFIG_FRAME_POINTER > +/* > + * kretprobe_trampoline skips updating frame pointer. The frame pointer > + * saved in trampoline_handler points to the real caller function's > + * frame pointer. Thus the kretprobe_trampoline doesn't seems to have a > + * standard stack frame with CONFIG_FRAME_POINTER=y. > + * Let's mark it non-standard function. Anyway, FP unwinder can correctly > + * unwind without the hint. s/doesn't seems to have a standard stack frame /doesn't have a standard stack frame There's nothing 'seems' about the situation - it's a non-standard function entry and stack frame situation, and the unwinder needs to know about it. > +STACK_FRAME_NON_STANDARD(kretprobe_trampoline); > +#undef UNWIND_HINT_FUNC > +#define UNWIND_HINT_FUNC > +#endif > /* > * When a retprobed function returns, this code saves registers and > * calls trampoline_handler() runs, which calls the kretprobe's handler. > @@ -1031,6 +1044,7 @@ asm( > /* We don't bother saving the ss register */ > #ifdef CONFIG_X86_64 > " pushq %rsp\n" > + UNWIND_HINT_FUNC > " pushfq\n" > SAVE_REGS_STRING > " movq %rsp, %rdi\n" > @@ -1041,6 +1055,7 @@ asm( > " popfq\n" > #else > " pushl %esp\n" > + UNWIND_HINT_FUNC > " pushfl\n" > SAVE_REGS_STRING > " movl %esp, %eax\n" Why not provide an appropriate annotation method in <asm/unwind_hints.h>, so that other future code can use it too instead of reinventing the wheel? Thanks, Ingo
