From patchwork Tue Jan 23 11:07:55 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Donnefort X-Patchwork-Id: 13527264 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 676DB5D900 for ; Tue, 23 Jan 2024 11:08:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706008093; cv=none; b=b4knoCIFEGU0WwB0gZrDfpiA92jU4rbRsQcpEC2ktAbIFIqT7L1+Jm6CWWL1Q87wwsPd27EYqLf6OfIfv/6iC1Q201UCCA4MNWvYpiIETgyHae+UNeSZQJYYYfL4WwsQeA4bnsAc+XLjHZdKaz2iHhpQNQAPDz2aJ/mh+cAQlTM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706008093; c=relaxed/simple; bh=LpOg75oVVjHVZ5zcMj1Cygednq+3XV9tdhxoOBosZSY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=P6KmHUll8tVYvHoHvZm1Tbkl6ZOPPrQDZtL0gIB5QxIMy2b1WAL6oA9d9D26eq8pIk/F6pqxUv9VuveEe3zUNiC/yaAECzi01YntI3QDlboRpgKEiOZmpLRUlUX+BWAaNN53iIkbakisQTMwWwSFO0+axOE8mdYvyV1oSFS/MHc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=j2q7MsmH; arc=none smtp.client-ip=209.85.219.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="j2q7MsmH" Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-dc37425c78eso775817276.2 for ; Tue, 23 Jan 2024 03:08:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1706008090; x=1706612890; darn=vger.kernel.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=Dr7C1cm+K+0sbZ2jJ1EOt2NrKO81ZGlkB1FGvQN+/xc=; b=j2q7MsmHrELBsmjUcQ82/8B0F4gwBmxh6LZ2io3YbAwEDEAxJVh3YLR/O0BgEwzqRe j8eAZeLjnbYP0HbcMR4ZCRmyFn5SbvaTx+tHAsNqcYAVC+kWuU6IlBavp2eaFIb8uEJa ptEKS01h8OLFKSK2waPcf5PYPJ2JX9UPHc8zPJs05vDnMrXYse9wSsIdwR4dwcYCDk1f Ib7m0sUqr8wLsqpYj7MRm5rm3wjRf9RBRdCuznL9RThnhMOC0EMXDolAC8j6CVBSdHOz 2lbdlFn04VXQeSgAvVv/vC9YHkBxBT/OmIND+wzih1WaiY1t/WexyGBdeC+SQ+bQ7jyM NmjQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706008090; x=1706612890; 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=Dr7C1cm+K+0sbZ2jJ1EOt2NrKO81ZGlkB1FGvQN+/xc=; b=XSlxGpxAvwYnP90X4VyuvZrX/BfePDV3GLaDxa7MNhVnnd8hr3uly/V6x1rLK1XjPV 7Me1QsCCje5CaQbf5qjIW9ADCNn9wv6zPYQM3uaIiz5WH4SI2gmZJGufx3HWOG/qvhwB HxbHu9Bz+xhF27+4dd2jqU57IyHDV2lLBNuCCP8EQJoTAAxiGs5X2Y/lBCc+Qnk9NDN1 MG5QJdUZo0HbDn5Nsf5tevTaEvExu7WblxyWUf5nfHo0+T369HoOUQ5oFSz4lt1kI6id kTX2In9l9tOXJHKKlbFrh7nObLeYv5I5d5GxddL5/lFdliQ+d5lR5EKMxUeytEyan5ca 9UMA== X-Gm-Message-State: AOJu0YxvaQNrmVl2ALWIH/bQW9BbCd9cfVadSSHPPpqV+yfYahLjlGBh 6cSk6gZsF2+XxoM86fwkcjNMnPb1XNDMpeN5gdl/W7k/2jdxyXLlstsTEO43bJTKW5ERea9iyBc Y8INeOxUQk35B9q9SRg== X-Google-Smtp-Source: AGHT+IFIyDVggOlHUuSF0i46wk6Y9mpErXwWsnI9RT508ATRbK2lbJzxqsXgHRS4RWrxxOVJKckQ9qtccIT8EXCj X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a05:6902:1b12:b0:db5:4766:e363 with SMTP id eh18-20020a0569021b1200b00db54766e363mr2514419ybb.6.1706008090555; Tue, 23 Jan 2024 03:08:10 -0800 (PST) Date: Tue, 23 Jan 2024 11:07:55 +0000 In-Reply-To: <20240123110757.3657908-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240123110757.3657908-1-vdonnefort@google.com> X-Mailer: git-send-email 2.43.0.429.g432eaa2c6b-goog Message-ID: <20240123110757.3657908-5-vdonnefort@google.com> Subject: [PATCH v12 4/6] 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, Vincent Donnefort 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. Signed-off-by: Vincent Donnefort diff --git a/include/uapi/linux/trace_mmap.h b/include/uapi/linux/trace_mmap.h index 5468afc94be7..09c4ae6d6e71 100644 --- a/include/uapi/linux/trace_mmap.h +++ b/include/uapi/linux/trace_mmap.h @@ -41,4 +41,6 @@ struct trace_buffer_meta { __u64 subbufs_lost; }; +#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 ac59321a8d95..eb9e829ecc12 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1175,6 +1175,12 @@ 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); @@ -1309,6 +1315,9 @@ static int tracing_arm_snapshot_locked(struct trace_array *tr) if (tr->snapshot == UINT_MAX) return -EBUSY; + if (tr->mapped) + return -EBUSY; + ret = tracing_alloc_snapshot_instance(tr); if (ret) return ret; @@ -6520,7 +6529,7 @@ 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) @@ -8637,15 +8646,31 @@ 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) - return -ENOIOCTLCMD; + 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); + if (err) + return err; + } + + 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); iter->wait_index++; @@ -8658,6 +8683,90 @@ static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned return 0; } +static vm_fault_t tracing_buffers_mmap_fault(struct vm_fault *vmf) +{ + struct ftrace_buffer_info *info = vmf->vma->vm_file->private_data; + struct trace_iterator *iter = &info->iter; + vm_fault_t ret = VM_FAULT_SIGBUS; + struct page *page; + + page = ring_buffer_map_fault(iter->array_buffer->buffer, iter->cpu_file, + vmf->pgoff); + if (!page) + return ret; + + get_page(page); + vmf->page = page; + vmf->page->mapping = vmf->vma->vm_file->f_mapping; + vmf->page->index = vmf->pgoff; + + return 0; +} + +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; + + ring_buffer_unmap(iter->array_buffer->buffer, iter->cpu_file); + +#ifdef CONFIG_TRACER_MAX_TRACE + mutex_lock(&trace_types_lock); + if (!WARN_ON(!iter->tr->mapped)) + iter->tr->mapped--; + mutex_unlock(&trace_types_lock); +#endif +} + +static void tracing_buffers_mmap_open(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_map(iter->array_buffer->buffer, iter->cpu_file)); +} + +static const struct vm_operations_struct tracing_buffers_vmops = { + .open = tracing_buffers_mmap_open, + .close = tracing_buffers_mmap_close, + .fault = tracing_buffers_mmap_fault, +}; + +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; + + if (vma->vm_flags & VM_WRITE) + return -EPERM; + + vm_flags_mod(vma, VM_DONTCOPY | VM_DONTDUMP, VM_MAYWRITE); + vma->vm_ops = &tracing_buffers_vmops; + +#ifdef CONFIG_TRACER_MAX_TRACE + mutex_lock(&trace_types_lock); + if (iter->tr->snapshot || iter->tr->mapped == INT_MAX) { + ret = -EBUSY; + goto unlock; + } + + /* Wait for update_max_tr() to observe iter->tr->mapped */ + if (!iter->tr->mapped++) + synchronize_rcu(); +#endif + + ret = ring_buffer_map(iter->array_buffer->buffer, iter->cpu_file); + +#ifdef CONFIG_TRACER_MAX_TRACE + if (ret) + iter->tr->mapped--; +unlock: + mutex_unlock(&trace_types_lock); +#endif + return ret; +} + static const struct file_operations tracing_buffers_fops = { .open = tracing_buffers_open, .read = tracing_buffers_read, @@ -8666,6 +8775,7 @@ 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 3aa06bd5e48d..25ec246d5f1e 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -335,6 +335,7 @@ struct trace_array { struct array_buffer max_buffer; bool allocated_snapshot; unsigned int snapshot; + int mapped; #endif #ifdef CONFIG_TRACER_MAX_TRACE unsigned long max_latency;