On Sat, Mar 20, 2021 at 10:05:43PM +0900, Masami Hiramatsu wrote: > On Sat, 20 Mar 2021 21:16:16 +0900 > Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > > On Fri, 19 Mar 2021 21:22:39 +0900 > > 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. > > > > > > > Test bot also found a new warning for this. > > > > > >> arch/x86/kernel/kprobes/core.o: warning: objtool: kretprobe_trampoline()+0x25: call without frame pointer save/setup > > > > With CONFIG_FRAME_POINTER=y. > > > > Of course this can be fixed with additional "push %bp; mov %sp, %bp" before calling > > trampoline_handler. But actually we know that this function has a bit special > > stack frame too. > > > > Can I recover STACK_FRAME_NON_STANDARD(kretprobe_trampoline) when CONFIG_FRAME_POINTER=y ? > > So something like this. Does it work? > > diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c > index b31058a152b6..651f337dc880 100644 > --- a/arch/x86/kernel/kprobes/core.c > +++ b/arch/x86/kernel/kprobes/core.c > @@ -760,6 +760,10 @@ int kprobe_int3_handler(struct pt_regs *regs) > } > NOKPROBE_SYMBOL(kprobe_int3_handler); > > +#ifdef CONFIG_FRAME_POINTER > +#undef UNWIND_HINT_FUNC > +#define UNWIND_HINT_FUNC > +#endif This hunk isn't necessary. The unwind hints don't actually have an effect with frame pointers. > /* > * When a retprobed function returns, this code saves registers and > * calls trampoline_handler() runs, which calls the kretprobe's handler. > @@ -797,7 +801,14 @@ asm( > ".size kretprobe_trampoline, .-kretprobe_trampoline\n" > ); > NOKPROBE_SYMBOL(kretprobe_trampoline); > - > +#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. > + */ > +STACK_FRAME_NON_STANDARD(kretprobe_trampoline); > +#endif > > /* > * Called from kretprobe_trampoline Ack. -- Josh
