From patchwork Mon Nov 1 06:04:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 12595807 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B15D2C4321E for ; Mon, 1 Nov 2021 06:05:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D4C56108F for ; Mon, 1 Nov 2021 06:05:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231543AbhKAGIO (ORCPT ); Mon, 1 Nov 2021 02:08:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55266 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230501AbhKAGHj (ORCPT ); Mon, 1 Nov 2021 02:07:39 -0400 Received: from mail-pj1-x102e.google.com (mail-pj1-x102e.google.com [IPv6:2607:f8b0:4864:20::102e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3F17EC061220; Sun, 31 Oct 2021 23:04:53 -0700 (PDT) Received: by mail-pj1-x102e.google.com with SMTP id gx15-20020a17090b124f00b001a695f3734aso681469pjb.0; Sun, 31 Oct 2021 23:04:53 -0700 (PDT) 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=LvSuBTtzWbrXgjb4RLiUJa0DKbJeUJhJDjpVybnmpmo=; b=Mons/lRRxlmoaqOVtmFZnSu86Gkf5r4H5cY0kniY9gdH+szl8upHhpaZR7MR4xQ4tw dE2pI6UqL1jzYM4vvLqKghrUPQDn79hRqU7KxiMF+5YggE6jafzi9LymBwddjrin53xA DS/vBbsVNijV75Vx09TumG5j4U1GZmxVHVKUrh58sYOCTTMBcRzBvqBQmlqQjnp9UiE6 CSWjjS2dsqFC7BDjyMH2pF3tVsU6TtlHkUNzoI8cXteZR0F4qZ685VNLWN0UoeXzxvyY 29Os19nVMJ2skD60ZUbljxErtaiTL7ovw6A0gtYiuQbZsZ494tasBFvKYe9V+eptBdn1 Gtvg== 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=LvSuBTtzWbrXgjb4RLiUJa0DKbJeUJhJDjpVybnmpmo=; b=Bz66TtPRSWcDegBj4jP7PKAeZsZxeB7kQy8Vq1BHUwiIVeEA6XTlqbQhwpkU+kmOp5 xamIhZMa3j3/pEbg8FMu9ssTWMXsbi1qkZRCDTs1BFQgEWk+2GC9VR1QOS6qemtVBE8l B90H2Q4k8uH/jqmKDzJlUleAP42DhqZTmDb3pXVT1HMVJ4L4doXgjOJGvfNb3UlkViq5 TaFTPcvhB6OAFv5cGRrqUucgLh467TgavzWDmKCsrk0dmVLFHnuA5lxwvzgEE9OM3V/U ukBmG6BMDTmUwaAkmJ6n4LLQNhcqlODWNw4tVaT24J2P1E/56yfOZvV3ZrU8IVedbqDa Fnfg== X-Gm-Message-State: AOAM532eyZHcHrIS9rE2jNz6K+MdjkMd+8FUs09r9Yq5zKYSnEHJbX9S djXgG/VhVI5p42+OKRyUDaU= X-Google-Smtp-Source: ABdhPJx4c5pscRjAJUsqapKZZ8TRE5l4wRfA5yn4IJZjx67PGHHeSXi7SUSuCfLV4PBYO3mVczta1w== X-Received: by 2002:a17:90b:3149:: with SMTP id ip9mr33599543pjb.45.1635746692795; Sun, 31 Oct 2021 23:04:52 -0700 (PDT) Received: from localhost.localdomain ([144.202.123.152]) by smtp.gmail.com with ESMTPSA id g8sm3277586pfc.65.2021.10.31.23.04.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 31 Oct 2021 23:04:52 -0700 (PDT) From: Yafang Shao To: akpm@linux-foundation.org, keescook@chromium.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, arnaldo.melo@gmail.com, pmladek@suse.com, peterz@infradead.org, viro@zeniv.linux.org.uk, valentin.schneider@arm.com, qiang.zhang@windriver.com, robdclark@chromium.org, christian@brauner.io, dietmar.eggemann@arm.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, davem@davemloft.net, kuba@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, dennis.dalessandro@cornelisnetworks.com, mike.marciniszyn@cornelisnetworks.com, dledford@redhat.com, jgg@ziepe.ca Cc: linux-rdma@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, oliver.sang@intel.com, lkp@intel.com, Yafang Shao , Alexei Starovoitov , Andrii Nakryiko Subject: [PATCH v7 10/11] sched.h: extend task comm from 16 to 24 Date: Mon, 1 Nov 2021 06:04:18 +0000 Message-Id: <20211101060419.4682-11-laoar.shao@gmail.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20211101060419.4682-1-laoar.shao@gmail.com> References: <20211101060419.4682-1-laoar.shao@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org When I was implementing a new per-cpu kthread cfs_migration, I found the comm of it "cfs_migration/%u" is truncated due to the limitation of TASK_COMM_LEN. For example, the comm of the percpu thread on CPU10~19 are all with the same name "cfs_migration/1", which will confuse the user. This issue is not critical, because we can get the corresponding CPU from the task's Cpus_allowed. But for kthreads correspoinding to other hardware devices, it is not easy to get the detailed device info from task comm, for example, jbd2/nvme0n1p2- xfs-reclaim/sdf We can also shorten the name to work around this problem, but I find there are so many truncated kthreads: rcu_tasks_kthre rcu_tasks_rude_ rcu_tasks_trace poll_mpt3sas0_s ext4-rsv-conver xfs-reclaim/sd{a, b, c, ...} xfs-blockgc/sd{a, b, c, ...} xfs-inodegc/sd{a, b, c, ...} audit_send_repl ecryptfs-kthrea vfio-irqfd-clea jbd2/nvme0n1p2- ... We should improve this problem fundamentally by extending comm size to 24 bytes. task_struct is growing rather regularly by 8 bytes. After this change, the truncated kthreads listed above will be displayed as: rcu_tasks_kthread rcu_tasks_rude_kthread rcu_tasks_trace_kthread poll_mpt3sas0_statu ext4-rsv-conversion xfs-reclaim/sdf1 xfs-blockgc/sdf1 xfs-inodegc/sdf1 audit_send_reply ecryptfs-kthread vfio-irqfd-cleanup jbd2/nvme0n1p2-8 As we have converted all the unsafe copy of task comm to the safe one, this change won't make any trouble to the kernel or the in-tree tools. The safe one and unsafe one of comm copy as follows, Unsafe Safe strlcpy strscpy_pad strncpy strscpy_pad bpf_probe_read_kernel bpf_probe_read_kernel_str bpf_core_read_str bpf_get_current_comm perf_event__prepare_comm prctl(2) Regarding the possible risk it may take to the out-of-tree user tools, if the user tools get the task comm through kernel API like prctl(2), bpf_get_current_comm() and etc, the tools still work well after this change. While If the user tools get the task comm through direct string copy, it must make sure the copied string should be with a nul terminator. Signed-off-by: Yafang Shao Cc: Mathieu Desnoyers Cc: Arnaldo Carvalho de Melo Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Al Viro Cc: Kees Cook Cc: Petr Mladek --- include/linux/sched.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 09ac13e54549..a8822e26653e 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -276,10 +276,11 @@ struct task_group; /* * Define the task command name length as enum, then it can be visible to - * BPF programs. + * BPF programs. The TASK_COMM_LEN_16 is kept for backward-compitability. */ enum { - TASK_COMM_LEN = 16, + TASK_COMM_LEN_16 = 16, + TASK_COMM_LEN = 24, }; extern void scheduler_tick(void);