From patchwork Tue Jan 31 16:15:03 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13123146 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F99DC636CC for ; Tue, 31 Jan 2023 16:15:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229742AbjAaQPM (ORCPT ); Tue, 31 Jan 2023 11:15:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54366 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229934AbjAaQPL (ORCPT ); Tue, 31 Jan 2023 11:15:11 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3329E53E73; Tue, 31 Jan 2023 08:15:10 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D658CB81D12; Tue, 31 Jan 2023 16:15:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 141D2C433EF; Tue, 31 Jan 2023 16:15:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1675181707; bh=On6dk7QxcXuk5ZrUhYfXctjO795dxCDztPU8h5Zx/64=; h=From:To:Cc:Subject:Date:From; b=kRtnAixxwqsW1e2PcXXP4D5YNhGZ1zzAbm1i8tSAmFwVApOdZ6lwzIJS7qQfJCX9D SaRTwi9lICKi1/CFNZmF+3CeBW8YwQEvBjCaHeoPlQSCgb10J0PDYazE4yhsWTh1Me +/jG/vBuyprnJIUipsRWtRfs9/67velv0IAdCGEBc2Mn2qbEP04exQswgse4prSjoD P6/XN1OXS+uCcwg5tXNvkKbKjbav4J2iymEWamyMjtAaUfsazUof8cRJIlfuy4EYBx ZE+VSYLuN/3cw+wDMafAXIYz1lgxe1dgi2U6nb9/Fsq3QfBa/HsN+sc26kfI99DeFK l9snyOkiWEymw== From: "Masami Hiramatsu (Google)" To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Steven Rostedt , mhiramat@kernel.org, Florent Revest , Mark Rutland , Will Deacon Subject: [PATCH v2 00/10] tracing: Add fprobe events Date: Wed, 1 Feb 2023 01:15:03 +0900 Message-Id: <167518170369.336834.15310137713178284219.stgit@mhiramat.roam.corp.google.com> X-Mailer: git-send-email 2.39.1.456.gfc5497dd1b-goog User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org Hi, Here is the 2nd version of improve fprobe and add a basic fprobe event support for ftrace (tracefs) and perf. Here is the previous version. https://lore.kernel.org/all/166792255429.919356.14116090269057513181.stgit@devnote3/T/#u This version has some fixes, update patch description with the reason why this is required, and add some testcases. With this fprobe events, we can continue to trace function entry/exit even if the CONFIG_KPROBES_ON_FTRACE is not available. Since CONFIG_KPROBES_ON_FTRACE requires the CONFIG_DYNAMIC_FTRACE_WITH_REGS, it is not available if the architecture only supports CONFIG_DYNAMIC_FTRACE_WITH_ARGS (e.g. arm64). And that means kprobe events can not probe function entry/exit effectively on such architecture. But this problem can be solved if the dynamic events supports fprobe events because fprobe events doesn't use kprobe but ftrace via fprobe. With this series, user can add new events on the entry and exit of kernel functions (which can be ftraced). Unlike kprobe events, the fprobe events can only probe the function entry and exit, the IP address will have some offsets from the symbol address. And it can only trace the function args, return value, and stacks. (no registers) For probing function body, users can continue to use the kprobe events. The fprobe events syntax is here; f[:[GRP/][EVENT]] FUNCTION [FETCHARGS] f[MAXACTIVE][:[GRP/][EVENT]] FUNCTION%return [FETCHARGS] E.g. # echo 'f vfs_read $arg1' >> dynamic_events # echo 'f vfs_read%return $retval' >> dynamic_events # cat dynamic_events f:fprobes/vfs_read_entry vfs_read arg1=$arg1 f:fprobes/vfs_read_exit vfs_read%return arg1=$retval # echo 1 > events/fprobes/enable # head -n 20 trace | tail # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | sh-142 [005] ...1. 448.386420: vfs_read_entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540 sh-142 [005] ..... 448.386436: vfs_read_exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1 sh-142 [005] ...1. 448.386451: vfs_read_entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540 sh-142 [005] ..... 448.386458: vfs_read_exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1 sh-142 [005] ...1. 448.386469: vfs_read_entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540 sh-142 [005] ..... 448.386476: vfs_read_exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1 sh-142 [005] ...1. 448.602073: vfs_read_entry: (vfs_read+0x4/0x340) arg1=0xffff888007f7c540 sh-142 [005] ..... 448.602089: vfs_read_exit: (ksys_read+0x75/0x100 <- vfs_read) arg1=0x1 Future works: - Trace multiple function entry/exit (wildcard). - Integrate it with the function graph tracer. - Use ftrace_regs instead of pt_regs and remove dependency of CONFIG_DYNAMIC_FTRACE_WITH_REGS. - Support (limited) register access via ftrace_regs. - Support fprobe event by perf probe. - Support entry data accessing from exit event. - Support BTF for trace arguments. This fprobe event may eventually replace the kprobe events for function entry and exit on some archs (e.g. arm64). Here's my current migration (kretprobe to fprobe) idea: Phase 1. introduce fprobe events. (THIS) Phase 2. introduce generic function graph shadow stack Phase 3. Replace the rethook with function shadow stack and use ftrace_regs in fprobe handlers. Phase 4. Extend this fprobe support to other archs. Even if kretprobe event is replaced with fprobe event, tracefs user can transparently use fprobe events for function entry/exit with 'p:...' and 'r:...' syntax (for backward compatibility.) Thank you, --- Masami Hiramatsu (Google) (10): fprobe: Pass entry_data to handlers lib/test_fprobe: Add private entry_data testcases fprobe: Add nr_maxactive to specify rethook_node pool size lib/test_fprobe: Add a test case for nr_maxactive fprobe: Skip exit_handler if entry_handler returns !0 lib/test_fprobe: Add a testcase for skipping exit_handler docs: tracing: Update fprobe documentation fprobe: Pass return address to the handlers tracing/probes: Add fprobe events for tracing function entry and exit. selftests/ftrace: Add fprobe related testcases Documentation/trace/fprobe.rst | 16 include/linux/fprobe.h | 17 include/linux/rethook.h | 2 include/linux/trace_events.h | 3 kernel/kprobes.c | 1 kernel/trace/Kconfig | 14 kernel/trace/Makefile | 1 kernel/trace/bpf_trace.c | 19 kernel/trace/fprobe.c | 45 + kernel/trace/rethook.c | 3 kernel/trace/trace.c | 3 kernel/trace/trace.h | 11 kernel/trace/trace_fprobe.c | 1125 ++++++++++++++++++++ kernel/trace/trace_probe.c | 4 kernel/trace/trace_probe.h | 3 lib/test_fprobe.c | 109 ++ samples/fprobe/fprobe_example.c | 11 .../ftrace/test.d/dynevent/add_remove_fprobe.tc | 26 .../ftrace/test.d/dynevent/fprobe_syntax_errors.tc | 88 ++ 19 files changed, 1470 insertions(+), 31 deletions(-) create mode 100644 kernel/trace/trace_fprobe.c create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe.tc create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc -- Masami Hiramatsu (Google)