From patchwork Tue Apr 23 23:27:26 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Donnefort X-Patchwork-Id: 13640880 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E2868C10F15 for ; Tue, 23 Apr 2024 23:27:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 10B166B019B; Tue, 23 Apr 2024 19:27:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0BBD46B019D; Tue, 23 Apr 2024 19:27:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E79436B019E; Tue, 23 Apr 2024 19:27:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id C63836B019B for ; Tue, 23 Apr 2024 19:27:50 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 7FA5940EAA for ; Tue, 23 Apr 2024 23:27:50 +0000 (UTC) X-FDA: 82042386300.10.1F5B3EC Received: from mail-wm1-f74.google.com (mail-wm1-f74.google.com [209.85.128.74]) by imf25.hostedemail.com (Postfix) with ESMTP id A289EA000C for ; Tue, 23 Apr 2024 23:27:48 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=o0n1XgpH; spf=pass (imf25.hostedemail.com: domain of 380MoZgoKCFQHzA9901ADF2AA270.yA8749GJ-886Hwy6.AD2@flex--vdonnefort.bounces.google.com designates 209.85.128.74 as permitted sender) smtp.mailfrom=380MoZgoKCFQHzA9901ADF2AA270.yA8749GJ-886Hwy6.AD2@flex--vdonnefort.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1713914868; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=kaFaT9yjXtresVS5HFOg4DBcxHZeTWd1pZVR5Za+Mxc=; b=QC3TTG+z0hBvmYGXZ8of8rJCqUy/q2/uLHiZLzlHe5XGsJPBbQoGLUPPdoGwnqkIl48tDX 5DGjEop22t0dcvRVCV8+I8SG0krXhEn+0goAL4hD/BtZK+XYu93abaJHEmZ9nFdK3szqiR 9CvkmPuKgBerHsYRXLH9gYU3LEZ8E4U= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=o0n1XgpH; spf=pass (imf25.hostedemail.com: domain of 380MoZgoKCFQHzA9901ADF2AA270.yA8749GJ-886Hwy6.AD2@flex--vdonnefort.bounces.google.com designates 209.85.128.74 as permitted sender) smtp.mailfrom=380MoZgoKCFQHzA9901ADF2AA270.yA8749GJ-886Hwy6.AD2@flex--vdonnefort.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1713914868; a=rsa-sha256; cv=none; b=ICExlDLY6uPzCeqShLFsRHxs0A9Hm1yXNufP9SK7jMdBn2BrzxzOyf6NRahoVmFSguGuXT 28r1Nz39M33tOlTJL8FG3utrH/OLeFkScBQ0B6sXuWnCay6N656jF9pr2B0MRbtcb4Z9AE 59LwipKyi4Zx1ngO2OKGlps8mM59lGs= Received: by mail-wm1-f74.google.com with SMTP id 5b1f17b1804b1-41681022d82so29763925e9.1 for ; Tue, 23 Apr 2024 16:27:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1713914867; x=1714519667; darn=kvack.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=kaFaT9yjXtresVS5HFOg4DBcxHZeTWd1pZVR5Za+Mxc=; b=o0n1XgpHdyL09zPd8+aR+vQX/dciTp+wFveBn90vSTPhPGKpOGcatGCo+9wq72nHoY TQQDdmvZztUsVX80xEdEEEEkMVMeQ5QS0IcnoYco8wVx3HtfJjKw99lx75n1X3hUw3Qh HEMRwhF4DVGYXm6Qx67kALIw+H96nbns6AgmMsQc+Eli734nJ/eUbBIc6xAN2zIoPTkj UF4wUJ+3QOSM0UVW1aJhhCI/VPbNvsxOXm0q4KlQJlgQCjGxdjuL0pRkolj80mdg3R1n LYX2pK7vMo1cg6jTh4mB8PCB9+9DBELiX5+AU7UISGsJTbYYiBk8x67pm1FJlryiRzUe lrtg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713914867; x=1714519667; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=kaFaT9yjXtresVS5HFOg4DBcxHZeTWd1pZVR5Za+Mxc=; b=twEkc1UIomdVVfHiPBY9TrYecnHdAv0TmOpcZI6B1456dSYIvgrKilcvlendC35F+U ctwqj2O4sqYSduTcC2XvwCCZPdg77n3f+XcptMBVXS0qcrwVChIVPdEU24OVAySzIxdN Z8fcVnEj8jx1MqXYuRfbpjX+8ROtWKZtVOpIKfNAZhEYIJ6T9+artFQ5btxnsMnG5wD2 T5uDMI4qcYE2roO9sgd8PJq1x59sizhffG+gx+Khrj4cm6GF2Cfg7rfFLTA/L9l+0UNp +6Z0W+ImMbIH/Zxg+rOYb/9xmGoFjFAMY3wqQX+HWAZRugsE7Be8x6gUaAJ0Aeh5loW6 VLHw== X-Forwarded-Encrypted: i=1; AJvYcCWdN4ArmEUq7mYPLhmBO/Jp3dxlXHTJ7vdxsAzaJIApCc3kKSZi++YOaQIFyp+jg3PePBHDhYYOTf4W6JL21qby79w= X-Gm-Message-State: AOJu0Yzd2o+SEQcokAl/87CTG2kyTGMvi38pD3VJNfT7a6HGVda3ldXV 5aNIy+gDw31pLpSQjkaT0HEL8Xm26bazigtx5rymcGax1qOM3kRjxPcBhM5ObUIQ0GRujiy8VWF kL26Kfx4ny23YKJUddw== X-Google-Smtp-Source: AGHT+IFCDABCADdFLnD0phykkbD9Gu5AIQBZ62UxA/EhQAKHMu7J7egaT2rm+tUe6aiIMaJ0/Tc/k/iDgGFOOjAe X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a05:600c:5352:b0:41a:3485:19c4 with SMTP id hi18-20020a05600c535200b0041a348519c4mr3395wmb.3.1713914867196; Tue, 23 Apr 2024 16:27:47 -0700 (PDT) Date: Wed, 24 Apr 2024 00:27:26 +0100 In-Reply-To: <20240423232728.1492340-1-vdonnefort@google.com> Mime-Version: 1.0 References: <20240423232728.1492340-1-vdonnefort@google.com> X-Mailer: git-send-email 2.44.0.769.g3c40516874-goog Message-ID: <20240423232728.1492340-4-vdonnefort@google.com> Subject: [PATCH v21 3/5] tracing: Allow user-space mapping of the ring-buffer From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, rdunlap@infradead.org, rppt@kernel.org, david@redhat.com, Vincent Donnefort , linux-mm@kvack.org X-Stat-Signature: 1za8w4aq3aju3fe8rz7zqqbpkriumect X-Rspamd-Queue-Id: A289EA000C X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1713914868-444192 X-HE-Meta: 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 sY9XRR/i 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Currently, user-space extracts data from the ring-buffer via splice, which is handy for storage or network sharing. However, due to splice limitations, it is imposible to do real-time analysis without a copy. A solution for that problem is to let the user-space map the ring-buffer directly. The mapping is exposed via the per-CPU file trace_pipe_raw. The first element of the mapping is the meta-page. It is followed by each subbuffer constituting the ring-buffer, ordered by their unique page ID: * Meta-page -- include/uapi/linux/trace_mmap.h for a description * Subbuf ID 0 * Subbuf ID 1 ... It is therefore easy to translate a subbuf ID into an offset in the mapping: reader_id = meta->reader->id; reader_offset = meta->meta_page_size + reader_id * meta->subbuf_size; When new data is available, the mapper must call a newly introduced ioctl: TRACE_MMAP_IOCTL_GET_READER. This will update the Meta-page reader ID to point to the next reader containing unread data. Mapping will prevent snapshot and buffer size modifications. CC: Signed-off-by: Vincent Donnefort diff --git a/include/uapi/linux/trace_mmap.h b/include/uapi/linux/trace_mmap.h index b682e9925539..bd1066754220 100644 --- a/include/uapi/linux/trace_mmap.h +++ b/include/uapi/linux/trace_mmap.h @@ -43,4 +43,6 @@ struct trace_buffer_meta { __u64 Reserved2; }; +#define TRACE_MMAP_IOCTL_GET_READER _IO('T', 0x1) + #endif /* _TRACE_MMAP_H_ */ diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 233d1af39fff..a35e7f598233 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1191,6 +1191,12 @@ static void tracing_snapshot_instance_cond(struct trace_array *tr, return; } + if (tr->mapped) { + trace_array_puts(tr, "*** BUFFER MEMORY MAPPED ***\n"); + trace_array_puts(tr, "*** Can not use snapshot (sorry) ***\n"); + return; + } + local_irq_save(flags); update_max_tr(tr, current, smp_processor_id(), cond_data); local_irq_restore(flags); @@ -1323,7 +1329,7 @@ static int tracing_arm_snapshot_locked(struct trace_array *tr) lockdep_assert_held(&trace_types_lock); spin_lock(&tr->snapshot_trigger_lock); - if (tr->snapshot == UINT_MAX) { + if (tr->snapshot == UINT_MAX || tr->mapped) { spin_unlock(&tr->snapshot_trigger_lock); return -EBUSY; } @@ -6068,7 +6074,7 @@ static void tracing_set_nop(struct trace_array *tr) { if (tr->current_trace == &nop_trace) return; - + tr->current_trace->enabled--; if (tr->current_trace->reset) @@ -8194,15 +8200,32 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, return ret; } -/* An ioctl call with cmd 0 to the ring buffer file will wake up all waiters */ static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { struct ftrace_buffer_info *info = file->private_data; struct trace_iterator *iter = &info->iter; + int err; + + if (cmd == TRACE_MMAP_IOCTL_GET_READER) { + if (!(file->f_flags & O_NONBLOCK)) { + err = ring_buffer_wait(iter->array_buffer->buffer, + iter->cpu_file, + iter->tr->buffer_percent, + NULL, NULL); + if (err) + return err; + } - if (cmd) - return -ENOIOCTLCMD; + return ring_buffer_map_get_reader(iter->array_buffer->buffer, + iter->cpu_file); + } else if (cmd) { + return -ENOTTY; + } + /* + * An ioctl call with cmd 0 to the ring buffer file will wake up all + * waiters + */ mutex_lock(&trace_types_lock); /* Make sure the waiters see the new wait_index */ @@ -8214,6 +8237,76 @@ static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned return 0; } +#ifdef CONFIG_TRACER_MAX_TRACE +static int get_snapshot_map(struct trace_array *tr) +{ + int err = 0; + + /* + * Called with mmap_lock held. lockdep would be unhappy if we would now + * take trace_types_lock. Instead use the specific + * snapshot_trigger_lock. + */ + spin_lock(&tr->snapshot_trigger_lock); + + if (tr->snapshot || tr->mapped == UINT_MAX) + err = -EBUSY; + else + tr->mapped++; + + spin_unlock(&tr->snapshot_trigger_lock); + + /* Wait for update_max_tr() to observe iter->tr->mapped */ + if (tr->mapped == 1) + synchronize_rcu(); + + return err; + +} +static void put_snapshot_map(struct trace_array *tr) +{ + spin_lock(&tr->snapshot_trigger_lock); + if (!WARN_ON(!tr->mapped)) + tr->mapped--; + spin_unlock(&tr->snapshot_trigger_lock); +} +#else +static inline int get_snapshot_map(struct trace_array *tr) { return 0; } +static inline void put_snapshot_map(struct trace_array *tr) { } +#endif + +static void tracing_buffers_mmap_close(struct vm_area_struct *vma) +{ + struct ftrace_buffer_info *info = vma->vm_file->private_data; + struct trace_iterator *iter = &info->iter; + + WARN_ON(ring_buffer_unmap(iter->array_buffer->buffer, iter->cpu_file)); + put_snapshot_map(iter->tr); +} + +static const struct vm_operations_struct tracing_buffers_vmops = { + .close = tracing_buffers_mmap_close, +}; + +static int tracing_buffers_mmap(struct file *filp, struct vm_area_struct *vma) +{ + struct ftrace_buffer_info *info = filp->private_data; + struct trace_iterator *iter = &info->iter; + int ret = 0; + + ret = get_snapshot_map(iter->tr); + if (ret) + return ret; + + ret = ring_buffer_map(iter->array_buffer->buffer, iter->cpu_file, vma); + if (ret) + put_snapshot_map(iter->tr); + + vma->vm_ops = &tracing_buffers_vmops; + + return ret; +} + static const struct file_operations tracing_buffers_fops = { .open = tracing_buffers_open, .read = tracing_buffers_read, @@ -8223,6 +8316,7 @@ static const struct file_operations tracing_buffers_fops = { .splice_read = tracing_buffers_splice_read, .unlocked_ioctl = tracing_buffers_ioctl, .llseek = no_llseek, + .mmap = tracing_buffers_mmap, }; static ssize_t diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 64450615ca0c..749a182dab48 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -336,6 +336,7 @@ struct trace_array { bool allocated_snapshot; spinlock_t snapshot_trigger_lock; unsigned int snapshot; + unsigned int mapped; unsigned long max_latency; #ifdef CONFIG_FSNOTIFY struct dentry *d_max_latency;