From: Josh Poimboeuf <jpoimboe@redhat.com> To: Masami Hiramatsu <mhiramat@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@kernel.org>, X86 ML <x86@kernel.org>, Daniel Xu <dxu@dxuuu.xyz>, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kuba@kernel.org, mingo@redhat.com, ast@kernel.org, tglx@linutronix.de, kernel-team@fb.com, yhs@fb.com, linux-ia64@vger.kernel.org Subject: Re: [PATCH -tip v3 05/11] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code Date: Sun, 21 Mar 2021 12:52:03 -0500 [thread overview] Message-ID: <20210321175203.4kcptzgs6pwxh5oh@treble> (raw) In-Reply-To: <20210320220543.e1558ce3a351554c6be3ea26@kernel.org> 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@kernel.org> wrote: > > > On Fri, 19 Mar 2021 21:22:39 +0900 > > Masami Hiramatsu <mhiramat@kernel.org> wrote: > > > > > From: Josh Poimboeuf <jpoimboe@redhat.com> > > > > > > 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
WARNING: multiple messages have this Message-ID (diff)
From: Josh Poimboeuf <jpoimboe@redhat.com> To: Masami Hiramatsu <mhiramat@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@kernel.org>, X86 ML <x86@kernel.org>, Daniel Xu <dxu@dxuuu.xyz>, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kuba@kernel.org, mingo@redhat.com, ast@kernel.org, tglx@linutronix.de, kernel-team@fb.com, yhs@fb.com, linux-ia64@vger.kernel.org Subject: Re: [PATCH -tip v3 05/11] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code Date: Sun, 21 Mar 2021 17:52:03 +0000 [thread overview] Message-ID: <20210321175203.4kcptzgs6pwxh5oh@treble> (raw) In-Reply-To: <20210320220543.e1558ce3a351554c6be3ea26@kernel.org> 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@kernel.org> wrote: > > > On Fri, 19 Mar 2021 21:22:39 +0900 > > Masami Hiramatsu <mhiramat@kernel.org> wrote: > > > > > From: Josh Poimboeuf <jpoimboe@redhat.com> > > > > > > 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
next prev parent reply other threads:[~2021-03-21 17:53 UTC|newest] Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-03-19 12:21 [PATCH -tip v3 00/11] kprobes: Fix stacktrace with kretprobes on x86 Masami Hiramatsu 2021-03-19 12:21 ` Masami Hiramatsu 2021-03-19 12:21 ` [PATCH -tip v3 01/11] ia64: kprobes: Fix to pass correct trampoline address to the handler Masami Hiramatsu 2021-03-19 12:21 ` Masami Hiramatsu 2021-03-19 12:22 ` [PATCH -tip v3 02/11] kprobes: treewide: Replace arch_deref_entry_point() with dereference_function_descriptor() Masami Hiramatsu 2021-03-19 12:22 ` [PATCH -tip v3 02/11] kprobes: treewide: Replace arch_deref_entry_point() with dereference_function_ Masami Hiramatsu 2021-03-19 12:22 ` [PATCH -tip v3 03/11] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() Masami Hiramatsu 2021-03-19 12:22 ` [PATCH -tip v3 03/11] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler Masami Hiramatsu 2021-03-19 12:22 ` [PATCH -tip v3 04/11] kprobes: Add kretprobe_find_ret_addr() for searching return address Masami Hiramatsu 2021-03-19 12:22 ` Masami Hiramatsu 2021-03-19 12:22 ` [PATCH -tip v3 05/11] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code Masami Hiramatsu 2021-03-19 12:22 ` Masami Hiramatsu 2021-03-20 12:16 ` Masami Hiramatsu 2021-03-20 12:16 ` Masami Hiramatsu 2021-03-20 13:05 ` Masami Hiramatsu 2021-03-20 13:05 ` Masami Hiramatsu 2021-03-21 17:52 ` Josh Poimboeuf [this message] 2021-03-21 17:52 ` Josh Poimboeuf 2021-03-22 0:08 ` Masami Hiramatsu 2021-03-22 0:08 ` Masami Hiramatsu 2021-03-21 17:50 ` Josh Poimboeuf 2021-03-21 17:50 ` Josh Poimboeuf 2021-03-19 12:22 ` [PATCH -tip v3 06/11] ARC: Add instruction_pointer_set() API Masami Hiramatsu 2021-03-19 12:22 ` Masami Hiramatsu 2021-03-19 12:23 ` [PATCH -tip v3 07/11] ia64: " Masami Hiramatsu 2021-03-19 12:23 ` Masami Hiramatsu 2021-03-20 1:04 ` Masami Hiramatsu 2021-03-20 1:04 ` Masami Hiramatsu 2021-03-19 12:23 ` [PATCH -tip v3 08/11] kprobes: Setup instruction pointer in __kretprobe_trampoline_handler Masami Hiramatsu 2021-03-19 12:23 ` Masami Hiramatsu 2021-03-21 12:54 ` Masami Hiramatsu 2021-03-21 12:54 ` Masami Hiramatsu 2021-03-19 12:23 ` [PATCH -tip v3 09/11] x86/kprobes: Push a fake return address at kretprobe_trampoline Masami Hiramatsu 2021-03-19 12:23 ` Masami Hiramatsu 2021-03-19 12:23 ` [PATCH -tip v3 10/11] x86/unwind: Recover kretprobe trampoline entry Masami Hiramatsu 2021-03-19 12:23 ` Masami Hiramatsu 2021-03-19 12:23 ` [PATCH -tip v3 11/11] tracing: Show kretprobe unknown indicator only for kretprobe_trampoline Masami Hiramatsu 2021-03-19 12:23 ` Masami Hiramatsu
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