On Sun, 21 Mar 2021 12:52:03 -0500 Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote: > 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. Without this, objtool shows the following warning with CONFIG_FRAME_POINTER=y. arch/x86/kernel/kprobes/core.o: warning: objtool: kretprobe_trampoline()+0x1: BUG: why am I validating an ignored function? It seems to complain about putting UNWIND_HINT on STACK_FRAME_NON_STANDARD function. > > > /* > > * 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. Thank you! > > -- > Josh > -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
