From mboxrd@z Thu Jan 1 00:00:00 1970 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 8B8ACC433F5 for ; Sun, 30 Jan 2022 14:45:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355152AbiA3OpP (ORCPT ); Sun, 30 Jan 2022 09:45:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58738 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1355136AbiA3Oo6 (ORCPT ); Sun, 30 Jan 2022 09:44:58 -0500 Received: from mail-pj1-x1034.google.com (mail-pj1-x1034.google.com [IPv6:2607:f8b0:4864:20::1034]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2F87CC061749 for ; Sun, 30 Jan 2022 06:44:57 -0800 (PST) Received: by mail-pj1-x1034.google.com with SMTP id o16-20020a17090aac1000b001b62f629953so8242238pjq.3 for ; Sun, 30 Jan 2022 06:44:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=WGfvZ4r5TNIGEOPtoPqp/tnebkonKtzqdtDq9GKibjo=; b=DCQ4wOWh7wbjPwKsG2kS/BtCMPVysyqL9LOqvMGLG4V1toRNTEb16VJAT4wqd2pR1x 5hrF/f76JKpDU6AfJwPF9fztVwuonsFV+kNYBGGdhAh08FfUVUEEubME1MU+iZ6HrmPH dgc5C7ashZFBQuSFbJoGpAISr0s/6fb03gb/DLgPAq41JOAnOPYkTcoXsXPwRtjH1smI sjoji3hJt8ZuhXSwCTWaR1kMqu81Eq8Kf/5N2ueH7kfZOCdNdWwfOO3rlxh5t7VIL6Up e5IJxDqzhQR7v9ljussgD5QUXsPYoLonPyGdyDpTaB/nX0R5gr8EGWhQ4/K5oyP9win2 Az1Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=WGfvZ4r5TNIGEOPtoPqp/tnebkonKtzqdtDq9GKibjo=; b=l20EWyhUCvuP2XlUS6mzZYcT7Kb+7jAT2+LVywXLgmbV/RGWKfG6jMftgruRsOG0YM G2c003PIrfTzrN4vPZdMDtQGS9xoMifiEXju1DHNS5cGHWFyhA8wFXcZZbrBay3Lupa5 QIB6lmG4A2d4ZT3fQbgbVYvgZ157Idy3DI30+sV6QzX9FE6lGAXh0wRfxhY2UKxy1q7/ e5ka4XAbWRcCVedZAF5lzc90kZMtNDixQzksYmuGFp0kbSUIGEUKcQtl00nwnVp+dYHT Zlh+UIUvQzmOAOb/G/R3+J282sg52IeooeYJ20C13FV4x7EtR/UDClXcG624EcL2pe5q dZZw== X-Gm-Message-State: AOAM530I2C+icUwN4b2DtC8Tk20euwHd3/zRjQHHXZeTypJad7G5O58C Jdkz4pCat50A8zagPu7DCnc= X-Google-Smtp-Source: ABdhPJyAO/VWNHNdKZk29Qw2uZmLYX0jLr4thopMMI8bIQ/KbMZXevMquwGYprRYmUUNkwH3Sj/+6w== X-Received: by 2002:a17:90b:380f:: with SMTP id mq15mr20032842pjb.66.1643553897259; Sun, 30 Jan 2022 06:44:57 -0800 (PST) Received: from localhost.localdomain (li567-56.members.linode.com. [192.155.81.56]) by smtp.gmail.com with ESMTPSA id w8sm10502126pfu.128.2022.01.30.06.44.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 30 Jan 2022 06:44:56 -0800 (PST) From: Jeff Xie To: rostedt@goodmis.org Cc: mhiramat@kernel.org, mingo@redhat.com, zanussi@kernel.org, linux-kernel@vger.kernel.org, Jeff Xie Subject: [PATCH v8 4/4] trace/objtrace: Add documentation for objtrace Date: Sun, 30 Jan 2022 22:44:30 +0800 Message-Id: <20220130144430.453221-5-xiehuan09@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220130144430.453221-1-xiehuan09@gmail.com> References: <20220130144430.453221-1-xiehuan09@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Added documentation explaining how to use objtrace trigger to get the value of the object. Signed-off-by: Jeff Xie --- Documentation/trace/events.rst | 83 ++++++++++++++++++++++++++++++++++ 1 file changed, 83 insertions(+) diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst index c47f381d0c00..383fff5ca9ba 100644 --- a/Documentation/trace/events.rst +++ b/Documentation/trace/events.rst @@ -546,6 +546,89 @@ The following commands are supported: See Documentation/trace/histogram.rst for details and examples. +- objtrace + + This command provides a way to get the value of any object, The object + can be obtained from the dynamic event(kprobe_event/uprobe_event) or the + static event(tracepoint). + + Usage: + When using the kprobe event, only need to set the objtrace(a new trigger), + we can get the value of the object. The object is from the setting of the + kprobe event. + + For example: + For the function bio_add_page(): + + int bio_add_page(struct bio *bio, struct page *page, + unsigned int len, unsigned int offset) + + Firstly, we can set the base of the object, thus the first string "arg1" + stands for the value of the first parameter of this function bio_add_gage(), + + # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events + + Secondly, we can get the value dynamically based on above object. + + find the offset of the bi_size in struct bio: + $ gdb vmlinux + (gdb) p &(((struct bio *)0)->bi_iter.bi_size) + $1 = (unsigned int *) 0x28 + + # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/ \ + p_bio_add_page_0/trigger + + # cd /sys/kernel/debug/tracing/ + # echo 'p bio_add_page arg1=$arg1' > ./kprobe_events + # echo 'objtrace:add:arg1,0x28:u32:1 if comm == "cat"' > ./events/kprobes/p_bio_add_page_0/trigger + + # du -sh /test.txt + 12.0K /test.txt + + # cat /test.txt > /dev/null + # cat ./trace + # tracer: nop + # + # entries-in-buffer/entries-written: 128/128 #P:4 + # + # _-----=> irqs-off/BH-disabled + # / _----=> need-resched + # | / _---=> hardirq/softirq + # || / _--=> preempt-depth + # ||| / _-=> migrate-disable + # |||| / delay + # TASK-PID CPU# ||||| TIMESTAMP FUNCTION + # | | | ||||| | | + cat-117 [002] ...1. 1.602243: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x0 + cat-117 [002] ...1. 1.602244: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x0 + cat-117 [002] ...2. 1.602244: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x1000 + cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x1000 + cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x1000 + cat-117 [002] ...2. 1.602245: bio_add_page <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x2000 + cat-117 [002] ...1. 1.602245: __bio_try_merge_page <-bio_add_page object:0xffff88811bee4000 value:0x2000 + cat-117 [002] ...1. 1.602245: __bio_add_page <-bio_add_page object:0xffff88811bee4000 value:0x2000 + cat-117 [002] ...1. 1.602245: submit_bio <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602245: submit_bio_noacct <-ext4_mpage_readpages object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: __submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: submit_bio_checks <-__submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: __cond_resched <-submit_bio_checks object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: should_fail_bio <-submit_bio_checks object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: blk_mq_submit_bio <-submit_bio_noacct object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: blk_attempt_plug_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602246: blk_mq_sched_bio_merge <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602247: __rcu_read_lock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602247: __rcu_read_unlock <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + cat-117 [002] ...1. 1.602247: __blk_mq_alloc_requests <-blk_mq_submit_bio object:0xffff88811bee4000 value:0x3000 + -0 [002] d..3. 1.602298: bio_endio <-blk_update_request object:0xffff88811bee4000 value:0x0 + -0 [002] d..3. 1.602298: mpage_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0 + -0 [002] d..3. 1.602298: __read_end_io <-blk_update_request object:0xffff88811bee4000 value:0x0 + -0 [002] d..3. 1.602300: bio_put <-blk_update_request object:0xffff88811bee4000 value:0x0 + -0 [002] d..3. 1.602300: bio_free <-blk_update_request object:0xffff88811bee4000 value:0x0 + -0 [002] d..3. 1.602300: mempool_free <-blk_update_request object:0xffff88811bee4000 value:0x0 + -0 [002] d..3. 1.602300: mempool_free_slab <-blk_update_request object:0xffff88811bee4000 value:0x0 + -0 [002] d..3. 1.602300: kmem_cache_free <-blk_update_request object:0xffff88811bee4000 value:0x0 + ... + 7. In-kernel trace event API ============================ -- 2.25.1