From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
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>,
Borislav Petkov <bp@alien8.de>,
Peter Zijlstra <peterz@infradead.org>,
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 v10 00/16] kprobes: Fix stacktrace with kretprobes on x86
Date: Mon, 23 Aug 2021 22:12:06 -0700 [thread overview]
Message-ID: <CAEf4Bzb2i4Z9kUWU+L-HF3k+XQ0V3hLH1Er7U2_oCdv1BTvaBw@mail.gmail.com> (raw)
In-Reply-To: <20210730083549.4e36df1cba88e408dc60b031@kernel.org>
On Thu, Jul 29, 2021 at 4:35 PM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> On Thu, 29 Jul 2021 23:05:56 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > Hello,
> >
> > This is the 10th version of the series to fix the stacktrace with kretprobe on x86.
> >
> > The previous version is here;
> >
> > https://lore.kernel.org/bpf/162601048053.1318837.1550594515476777588.stgit@devnote2/
> >
> > This version is rebased on top of new kprobes cleanup series(*1) and merging
> > Josh's objtool update series (*2)(*3) as [6/16] and [7/16].
> >
> > (*1) https://lore.kernel.org/bpf/162748615977.59465.13262421617578791515.stgit@devnote2/
> > (*2) https://lore.kernel.org/bpf/20210710192433.x5cgjsq2ksvaqnss@treble/
> > (*3) https://lore.kernel.org/bpf/20210710192514.ghvksi3ozhez4lvb@treble/
> >
> > Changes from v9:
> > - Add Josh's objtool update patches with a build error fix as [6/16] and [7/16].
> > - Add a API document for kretprobe_find_ret_addr() and check cur != NULL in [5/16].
> >
> > With this series, unwinder can unwind stack correctly from ftrace as below;
> >
> > # cd /sys/kernel/debug/tracing
> > # echo > trace
> > # echo 1 > options/sym-offset
> > # echo r vfs_read >> kprobe_events
> > # echo r full_proxy_read >> kprobe_events
> > # echo traceoff:1 > events/kprobes/r_vfs_read_0/trigger
> > # echo stacktrace:1 > events/kprobes/r_full_proxy_read_0/trigger
> > # echo 1 > events/kprobes/enable
> > # cat /sys/kernel/debug/kprobes/list
> > ffffffff8133b740 r full_proxy_read+0x0 [FTRACE]
> > ffffffff812560b0 r vfs_read+0x0 [FTRACE]
> > # echo 0 > events/kprobes/enable
> > # cat trace
> > # tracer: nop
> > #
> > # entries-in-buffer/entries-written: 3/3 #P:8
> > #
> > # _-----=> irqs-off
> > # / _----=> need-resched
> > # | / _---=> hardirq/softirq
> > # || / _--=> preempt-depth
> > # ||| / delay
> > # TASK-PID CPU# |||| TIMESTAMP FUNCTION
> > # | | | |||| | |
> > <...>-134 [007] ...1 16.185877: r_full_proxy_read_0: (vfs_read+0x98/0x180 <- full_proxy_read)
> > <...>-134 [007] ...1 16.185901: <stack trace>
> > => kretprobe_trace_func+0x209/0x300
> > => kretprobe_dispatcher+0x4a/0x70
> > => __kretprobe_trampoline_handler+0xd4/0x170
> > => trampoline_handler+0x43/0x60
> > => kretprobe_trampoline+0x2a/0x50
> > => vfs_read+0x98/0x180
> > => ksys_read+0x5f/0xe0
> > => do_syscall_64+0x37/0x90
> > => entry_SYSCALL_64_after_hwframe+0x44/0xae
> > <...>-134 [007] ...1 16.185902: r_vfs_read_0: (ksys_read+0x5f/0xe0 <- vfs_read)
> >
> > This shows the double return probes (vfs_read() and full_proxy_read()) on the stack
> > correctly unwinded. (vfs_read() returns to 'ksys_read+0x5f' and full_proxy_read()
> > returns to 'vfs_read+0x98')
> >
> > This also changes the kretprobe behavisor a bit, now the instraction pointer in
> > the 'pt_regs' passed to kretprobe user handler is correctly set the real return
> > address. So user handlers can get it via instruction_pointer() API, and can use
> > stack_trace_save_regs().
> >
> > You can also get this series from
> > git://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git kprobes/kretprobe-stackfix-v9
>
> Oops, this is of course 'kprobes/kretprobe-stackfix-v10'. And this branch includes above (*1) series.
Hi Masami,
Was this ever merged/applied? This is a very important functionality
for BPF kretprobes, so I hope this won't slip through the cracks.
Thanks!
>
> Thank you,
>
> --
> Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2021-08-24 5:12 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-29 14:05 [PATCH -tip v10 00/16] kprobes: Fix stacktrace with kretprobes on x86 Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 01/16] ia64: kprobes: Fix to pass correct trampoline address to the handler Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 02/16] kprobes: treewide: Replace arch_deref_entry_point() with dereference_symbol_descriptor() Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 03/16] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 04/16] kprobes: treewide: Make it harder to refer kretprobe_trampoline directly Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 05/16] kprobes: Add kretprobe_find_ret_addr() for searching return address Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 06/16] objtool: Add frame-pointer-specific function ignore Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 07/16] objtool: Ignore unwind hints for ignored functions Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 08/16] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline() Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 09/16] ARC: Add instruction_pointer_set() API Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 10/16] ia64: " Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 11/16] arm: kprobes: Make space for instruction pointer on stack Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 12/16] kprobes: Enable stacktrace from pt_regs in kretprobe handler Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 13/16] x86/kprobes: Push a fake return address at kretprobe_trampoline Masami Hiramatsu
2021-07-29 14:08 ` [PATCH -tip v10 14/16] x86/unwind: Recover kretprobe trampoline entry Masami Hiramatsu
2021-07-29 14:08 ` [PATCH -tip v10 15/16] tracing: Show kretprobe unknown indicator only for kretprobe_trampoline Masami Hiramatsu
2021-07-29 14:08 ` [PATCH -tip v10 16/16] x86/kprobes: Fixup return address in generic trampoline handler Masami Hiramatsu
2021-07-29 23:35 ` [PATCH -tip v10 00/16] kprobes: Fix stacktrace with kretprobes on x86 Masami Hiramatsu
2021-08-24 5:12 ` Andrii Nakryiko [this message]
2021-08-24 5:32 ` Masami Hiramatsu
2021-09-13 17:14 ` Andrii Nakryiko
2021-09-14 0:38 ` Masami Hiramatsu
2021-09-14 1:36 ` Andrii Nakryiko
2021-09-14 5:10 ` Masami Hiramatsu
2021-08-29 14:22 ` [RFC PATCH 0/1] Non stack-intrusive return probe event Masami Hiramatsu
2021-08-29 14:22 ` [RFC PATCH 1/1] [PoC] tracing: kprobe: Add non-stack intrusion " Masami Hiramatsu
2021-08-30 19:04 ` [RFC PATCH 0/1] Non stack-intrusive " Andrii Nakryiko
2021-08-31 6:06 ` Masami Hiramatsu
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