On Mon, 5 Jul 2021 10:02:47 +0200 Ingo Molnar <mingo@xxxxxxxxxx> wrote: > > * 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'? Oops, it's a typo. > > > 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? Sorry, I meant, this marks the kretprobe_trampoline as non-standard stack frame by STACK_FRAME_NON_STANDARD(). > > '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: Yes, if you think this is not correct way, what about the following? #ifdef CONFIG_FRAME_POINTER STACK_FRAME_NON_STANDARD(kretprobe_trampoline); #define KRETPROBE_UNWIND_HINT_FUNC #else #define KRETPROBE_UNWIND_HINT_FUNC UNWIND_HINT_FUNC #endif > > 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. Sorry for inconvenience... > > > +#else > > + > > In headers, in longer CPP blocks, please always mark the '#else' branch > with what it is the else branch of. OK. > > See the output of: > > kepler:~/tip> git grep '#else' arch/x86/include/asm/ | head Thanks for the hint! > > > +#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. OK. > > > +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? Would you mean we should define the UNWIND_HINT_FUNC as a macro which depends on CONFIG_FRAME_POINTER, in <asm/unwind_hints.h>? Josh, what would you think? Thank you, -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
