From: Daniel Xu <dxu@dxuuu.xyz>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>, X86 ML <x86@kernel.org>,
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
Subject: Re: [PATCH -tip 0/5] kprobes: Fix stacktrace in kretprobes
Date: Fri, 5 Mar 2021 11:16:45 -0800 [thread overview]
Message-ID: <20210305191645.njvrsni3ztvhhvqw@maharaja.localdomain> (raw)
In-Reply-To: <161495873696.346821.10161501768906432924.stgit@devnote2>
Hi Masami,
On Sat, Mar 06, 2021 at 12:38:57AM +0900, Masami Hiramatsu wrote:
> Hello,
>
> Here is a series of patches for kprobes and stacktracer to fix the kretprobe
> entries in the kernel stack. This was reported by Daniel Xu. I thought that
> was in the bpftrace, but it is actually more generic issue.
> So I decided to fix the issue in arch independent part.
>
> While fixing the issue, I found a bug in ia64 related to kretprobe, which is
> fixed by [1/5]. [2/5] and [3/5] is a kind of cleanup before fixing the main
> issue. [4/5] is the patch to fix the stacktrace, which involves kretprobe
> internal change. And [5/5] removing the stacktrace kretprobe fixup code in
> ftrace.
>
> Daniel, can you also check that this fixes your issue too? I hope it is.
Unfortunately, this patch series does not fix the issue I reported.
I think the reason your tests work is because you're using ftrace and
the ORC unwinder is aware of ftrace trampolines (see
arch/x86/kernel/unwind_orc.c:orc_ftrace_find).
bpftrace kprobes go through perf event subsystem (ie not ftrace) so
naturally orc_ftrace_find() does not find an associated trampoline. ORC
unwinding fails in this case because
arch/x86/kernel/kprobes/core.c:trampoline_handler sets
regs->ip = (unsigned long)&kretprobe_trampoline;
and `kretprobe_trampoline` is marked
STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
so it doesn't have a valid ORC entry. Thus, ORC immediately bails when
trying to unwind past the first frame.
The only way I can think of to fix this issue is to make the ORC
unwinder aware of kretprobe (ie the patch I sent earlier). I'm hoping
you have another idea if my patch isn't acceptable.
Thanks,
Daniel
next prev parent reply other threads:[~2021-03-05 19:17 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-05 15:38 [PATCH -tip 0/5] kprobes: Fix stacktrace in kretprobes Masami Hiramatsu
2021-03-05 15:39 ` [PATCH -tip 1/5] ia64: kprobes: Fix to pass correct trampoline address to the handler Masami Hiramatsu
2021-03-05 15:39 ` [PATCH -tip 2/5] kprobes: treewide: Replace arch_deref_entry_point() with dereference_function_descriptor() Masami Hiramatsu
2021-03-05 15:39 ` [PATCH -tip 3/5] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() Masami Hiramatsu
2021-03-10 14:21 ` Miroslav Benes
2021-03-10 15:42 ` Masami Hiramatsu
2021-03-11 13:37 ` Masami Hiramatsu
2021-03-05 15:39 ` [PATCH -tip 4/5] kprobes: stacktrace: Recover the address changed by kretprobe Masami Hiramatsu
2021-03-05 15:39 ` [PATCH -tip 5/5] tracing: Remove kretprobe unknown indicator from stacktrace Masami Hiramatsu
2021-03-05 15:44 ` Steven Rostedt
2021-03-05 19:16 ` Daniel Xu [this message]
2021-03-06 1:13 ` [PATCH -tip 0/5] kprobes: Fix stacktrace in kretprobes Masami Hiramatsu
2021-03-07 21:23 ` Daniel Xu
2021-03-08 2:52 ` Masami Hiramatsu
2021-03-08 13:05 ` Masami Hiramatsu
2021-03-09 1:19 ` Josh Poimboeuf
2021-03-10 9:57 ` Masami Hiramatsu
2021-03-10 15:08 ` Josh Poimboeuf
2021-03-10 15:55 ` Masami Hiramatsu
2021-03-10 18:31 ` Josh Poimboeuf
2021-03-11 0:20 ` Masami Hiramatsu
2021-03-11 1:06 ` Josh Poimboeuf
2021-03-11 1:54 ` Masami Hiramatsu
2021-03-11 16:51 ` Josh Poimboeuf
2021-03-12 3:22 ` Masami Hiramatsu
2021-03-10 22:46 ` Daniel Xu
2021-03-09 21:34 ` Daniel Xu
2021-03-10 10:50 ` Masami Hiramatsu
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