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Tue, 24 Aug 2021 01:13:01 -0400 Received: from mail-yb1-xb29.google.com (mail-yb1-xb29.google.com [IPv6:2607:f8b0:4864:20::b29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DE96EC061575; Mon, 23 Aug 2021 22:12:17 -0700 (PDT) Received: by mail-yb1-xb29.google.com with SMTP id k65so38517124yba.13; Mon, 23 Aug 2021 22:12:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=FrYRhpX8V2RxHliFgyoGiQz1nrfS1cZ96W8NbTEFTXA=; b=O3Hy0rGn0D/+9OlMmdod9ck0A1fu6zAHqpaf2Nq4mpXt5TvHelm3OyKSrv989Z4bnq 42MuPy7uN8aC1+Hvl/WFPT/MQvGusaeD12r1dDCFhhwzzBaOEQAmCF43lviPDBxNKbKf c18komufG6iRNJrHxv90dhY88N8lxAuvPLac5745qw0GNFOTAQ6T0Wq0McL0zmySg1fD A93O3b28P+eeycy7SsaBHu+LdtmJmib8geFUXxDceXv/dmNvohsR8In/F7jRE+Djov4p xqTzLCzVYGqKgt4MU/ISJyzjETCCOWQwE4jMLVzoLcFvH3CkOd8ABVJTUOjqHMie1Gvq oetQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=FrYRhpX8V2RxHliFgyoGiQz1nrfS1cZ96W8NbTEFTXA=; b=iQgtfv/VVMhu/bTdPeg6EWoWNyVyhVgTi9RCOG0v5FFT7cdl7u7BU/iT4+CE0rmTi9 7bBUHznnn93czKxyIFOXsajsxZjd5xYKEJBAWkWAOP2FWuTNZWm9c3/0LeCI2PFcX9+z ywQhnZInnqegD0dfFFWq4Hp+XoMgzhH+I9vKn87oqo1IcaJE+BCgy/6KXtY1EnhBvRKY fqKjmwVRtKBeciSaA866WGxmrykV9QhEiPbOlchHRlfsPllkVsCFc012EG54U0LOlr+6 ZBcRpmWIP/tSw+5pek6zH/zQ3T7nUASCIG+orZjdHydVeQJKfmIJbeXWIDK53rKMB8sS ZAkw== X-Gm-Message-State: AOAM532jTNwpyrZhdr4bkDj9XWh1xPCHIvRpoYrhf7r4ApamqnKDi68U Q8sxXJOoXQoEfYxhZon9UbXIqysAiEop09pYoJE= X-Google-Smtp-Source: ABdhPJy0Wx5/xOSiDxelaPuOpL34/4i2trBSGWHIlo/Heur7Lhrot/4g6kCCOg/uyGjN/ZNFBC433k5lcnHBXBE0A+s= X-Received: by 2002:a25:bb13:: with SMTP id z19mr50337899ybg.347.1629781937178; Mon, 23 Aug 2021 22:12:17 -0700 (PDT) MIME-Version: 1.0 References: <162756755600.301564.4957591913842010341.stgit@devnote2> <20210730083549.4e36df1cba88e408dc60b031@kernel.org> In-Reply-To: <20210730083549.4e36df1cba88e408dc60b031@kernel.org> From: Andrii Nakryiko Date: Mon, 23 Aug 2021 22:12:06 -0700 Message-ID: Subject: Re: [PATCH -tip v10 00/16] kprobes: Fix stacktrace with kretprobes on x86 To: Masami Hiramatsu Cc: Steven Rostedt , Josh Poimboeuf , Ingo Molnar , X86 ML , Daniel Xu , open list , bpf , Jakub Kicinski , Ingo Molnar , Alexei Starovoitov , Thomas Gleixner , Borislav Petkov , Peter Zijlstra , Kernel Team , Yonghong Song , linux-ia64@vger.kernel.org, Abhishek Sagar Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 29, 2021 at 4:35 PM Masami Hiramatsu wrote: > > On Thu, 29 Jul 2021 23:05:56 +0900 > Masami Hiramatsu 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: > > => 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 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrii Nakryiko Date: Tue, 24 Aug 2021 05:12:06 +0000 Subject: Re: [PATCH -tip v10 00/16] kprobes: Fix stacktrace with kretprobes on x86 Message-Id: List-Id: References: <162756755600.301564.4957591913842010341.stgit@devnote2> <20210730083549.4e36df1cba88e408dc60b031@kernel.org> In-Reply-To: <20210730083549.4e36df1cba88e408dc60b031@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Masami Hiramatsu Cc: Steven Rostedt , Josh Poimboeuf , Ingo Molnar , X86 ML , Daniel Xu , open list , bpf , Jakub Kicinski , Ingo Molnar , Alexei Starovoitov , Thomas Gleixner , Borislav Petkov , Peter Zijlstra , Kernel Team , Yonghong Song , linux-ia64@vger.kernel.org, Abhishek Sagar On Thu, Jul 29, 2021 at 4:35 PM Masami Hiramatsu wrote: > > On Thu, 29 Jul 2021 23:05:56 +0900 > Masami Hiramatsu 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: > > => 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