From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>, X86 ML <x86@kernel.org>,
Daniel Xu <dxu@dxuuu.xyz>,
open list <linux-kernel@vger.kernel.org>,
bpf <bpf@vger.kernel.org>, Jakub Kicinski <kuba@kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Alexei Starovoitov <ast@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Kernel Team <kernel-team@fb.com>, Yonghong Song <yhs@fb.com>,
linux-ia64@vger.kernel.org,
Abhishek Sagar <sagar.abhishek@gmail.com>
Subject: Re: [PATCH -tip v7 09/13] kprobes: Setup instruction pointer in __kretprobe_trampoline_handler
Date: Thu, 17 Jun 2021 13:21:59 -0500 [thread overview]
Message-ID: <20210617182159.ka227nkmhe4yu2de@treble> (raw)
In-Reply-To: <CAEf4Bzbob_M0aS-GUY5XaqePZr_prxUag3RLHtp=HY8Uu__10g@mail.gmail.com>
On Thu, Jun 17, 2021 at 10:45:41AM -0700, Andrii Nakryiko wrote:
> > > > > I know I suggested this patch, but I believe it would only be useful in
> > > > > combination with the use of UNWIND_HINT_REGS in SAVE_REGS_STRING. But I
> > > > > think that would be tricky to pull off correctly. Instead, we have
> > > > > UNWIND_HINT_FUNC, which is working fine.
> > > > >
> > > > > So I'd suggest dropping this patch, as the unwinder isn't actually
> > > > > reading regs->ip after all.
> > > >
> > > > ... and I guess this means patches 6-8 are no longer necessary.
> > >
> > > OK, I also confirmed that dropping those patche does not make any change
> > > on the stacktrace.
> > > Let me update the series without those.
> >
> > Oops, Andrii, can you also test the kernel without this patch?
> > (you don't need to drop patch 6-8)
>
> Hi Masami,
>
> Dropping this patch and leaving all the other in place breaks stack
> traces from kretprobes for BPF. I double checked with and without this
> patch. Without this patch we are back to having broken stack traces. I
> see either
>
> kretprobe_trampoline+0x0
>
> or
>
> ftrace_trampoline+0xc8
> kretprobe_trampoline+0x0
>
> Is there any problem if you leave this patch as is?
Hm, I must be missing something then. The patch is probably fine to
keep, we just may need to improve the commit log so that it makes sense
to me.
Which unwinder are you using (CONFIG_UNWINDER_*)?
--
Josh
next prev parent reply other threads:[~2021-06-17 18:22 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 6:39 [PATCH -tip v7 00/13] kprobes: Fix stacktrace with kretprobes on x86 Masami Hiramatsu
2021-05-27 6:39 ` [PATCH -tip v7 01/13] ia64: kprobes: Fix to pass correct trampoline address to the handler Masami Hiramatsu
2021-05-27 6:39 ` [PATCH -tip v7 02/13] kprobes: treewide: Replace arch_deref_entry_point() with dereference_symbol_descriptor() Masami Hiramatsu
2021-05-27 6:39 ` [PATCH -tip v7 03/13] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() Masami Hiramatsu
2021-06-14 15:46 ` Naveen N. Rao
2021-06-15 0:06 ` Masami Hiramatsu
2021-05-27 6:39 ` [PATCH -tip v7 04/13] kprobes: Add kretprobe_find_ret_addr() for searching return address Masami Hiramatsu
2021-05-27 6:39 ` [PATCH -tip v7 05/13] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code Masami Hiramatsu
2021-05-27 6:40 ` [PATCH -tip v7 06/13] ARC: Add instruction_pointer_set() API Masami Hiramatsu
2021-05-27 6:40 ` [PATCH -tip v7 07/13] ia64: " Masami Hiramatsu
2021-05-27 6:40 ` [PATCH -tip v7 08/13] arm: kprobes: Make a space for regs->ARM_pc at kretprobe_trampoline Masami Hiramatsu
2021-05-27 6:40 ` [PATCH -tip v7 09/13] kprobes: Setup instruction pointer in __kretprobe_trampoline_handler Masami Hiramatsu
2021-06-17 4:39 ` Josh Poimboeuf
2021-06-17 4:40 ` Josh Poimboeuf
2021-06-17 14:40 ` Masami Hiramatsu
2021-06-17 15:02 ` Masami Hiramatsu
2021-06-17 17:45 ` Andrii Nakryiko
2021-06-17 18:21 ` Josh Poimboeuf [this message]
2021-06-17 18:31 ` Andrii Nakryiko
2021-06-17 19:26 ` Josh Poimboeuf
2021-06-17 19:46 ` Andrii Nakryiko
2021-06-18 0:33 ` Masami Hiramatsu
2021-06-18 1:03 ` Josh Poimboeuf
2021-06-17 23:58 ` Masami Hiramatsu
2021-06-18 0:58 ` Josh Poimboeuf
2021-05-27 6:40 ` [PATCH -tip v7 10/13] x86/kprobes: Push a fake return address at kretprobe_trampoline Masami Hiramatsu
2021-06-17 4:41 ` Josh Poimboeuf
2021-05-27 6:40 ` [PATCH -tip v7 11/13] x86/unwind: Recover kretprobe trampoline entry Masami Hiramatsu
2021-06-17 4:41 ` Josh Poimboeuf
2021-05-27 6:40 ` [PATCH -tip v7 12/13] tracing: Show kretprobe unknown indicator only for kretprobe_trampoline Masami Hiramatsu
2021-05-27 6:41 ` [PATCH -tip v7 13/13] x86/kprobes: Fixup return address in generic trampoline handler Masami Hiramatsu
2021-05-27 16:41 ` [PATCH -tip v7 00/13] kprobes: Fix stacktrace with kretprobes on x86 Andrii Nakryiko
2021-06-10 3:40 ` Masami Hiramatsu
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