From patchwork Tue Feb 20 20:23:08 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Donnefort X-Patchwork-Id: 13564483 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 3994E14A4F2 for ; Tue, 20 Feb 2024 20:23:24 +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=1708460607; cv=none; b=F6QgcMELTTyea7wnkkHunSiM/2AC5LivfYk8V0uFdj6ds/LSNReiA4wfqmc350rP56K3wdJacsdhPX3GzreZOJcdkhL+k+P8lQm9B+hOMsRB/h91Q7DL2AJ0CF75RGs1ew3c10pc9f7QylPDdFlzOPbcxi1ZssaLhVv5svhngig= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708460607; c=relaxed/simple; bh=3SHPrTsh291gPPSJVJYwpI6tTu40xoNN9n+YT4ukuDU=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=iMiJAA1T7h3y9sG0IWddAXH+IRoGIxrKHN9P21USzT1Z0WSupxSPL/lNeg2GUg/5gE863jSap8D0y3ZNsLCfvBTco0KOrld2k7cmgCFIY38skAxp+4J7TMsbw8ykN+dbbc2KzdELYIt3+ibiPNjQZZvtSMt22+DWT+h3MIZ1lq8= 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=PzN4T4M/; 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="PzN4T4M/" Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-dc6ceade361so11056928276.0 for ; Tue, 20 Feb 2024 12:23:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1708460604; x=1709065404; 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=L8QdSbGAViukHkPqIszfFAUwep1tq+aZItBmmeT/BG0=; b=PzN4T4M/JM9C0wO1w247nch8Ynuh8lB0pacXm3Xshsz+91cyqXgsObQIOkBbWIfQ57 t8yE4mVUyxwhiKaMA3I7jP0z5prFynpRXRoduS2i9jHqTUyqav+UvnAyi8gDlcQmn5OV JY61V6hX7/gzuI8rHeC/pTKHQ9TKRKyh1VJhgSRZ/C7ioRWcR285h3qPCdZZPW8lOPEX rY6a+g6RJzKXf6PYe1/2F0Kevz9cM4pSEWbXWUfJZCt+oN7045gcrl8cPNrfkIHkepPv 9MHSrwypxKa/3CB/4Mwdx5rReBqNOyB6CL4ikGm8+pTP+1zcRdPFcfuqd4GIhScRwVc3 lioA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708460604; x=1709065404; 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=L8QdSbGAViukHkPqIszfFAUwep1tq+aZItBmmeT/BG0=; b=vh7FQqANn21hx9fWzTOSVbA9Zv56zBLjDqLnKMcmaJ0C5KCEXjf/IPQWZdf8n9qI12 GEtsw901CPHUxpfrHKlRxuJMIRmOEZKlFA1vY7DGWHgLw/XF/HXm5Aw36a0MTJ6X21kK u/7W2pqt3ovKthkJ7/rheZb3mGj0OgSD+rAq6mY+4gVQtqyw/Gih9g822B9eKjniPts2 k4J87Q52mA+G2L1s3MdttiDyF8sAU6+Wiy7sMIvWYi82/oyKkKaKFcnq8w9t5XVZZvS6 ekySttQo5/TxHRbSljvji6t9/LZmn8mtC+nlGLX5g8fQ15HVVZfbaEAUQ3977xaTvxT3 9WOQ== X-Forwarded-Encrypted: i=1; AJvYcCWmwkhYmw3cbTVdxHvnFw919852Vy2s3lQBDeFu6ahLYQo9h+gwOP/+RaP2pjLP/dwGOsU+Z4pk1cfhsWvKia5gQHeYg9iuVacY8JdJsUA4z1+S X-Gm-Message-State: AOJu0YzC1nHavb57ilPYO22MSO4UrpxXbM21v34LRpB9Q/ONppXfWRqj 4Re6Ps8xkcBT8OlIfcxxGWsLZ3DSZsaz3hJjDmcNqamzesN+lXlbeOehALXWyr/7bAWNKxHdFXo laBasRVArWw5iKQ663Q== X-Google-Smtp-Source: AGHT+IE/ancGfEt3dVmtYkHD4N3MkOZIKbA3j7T/n8+lKl5omaui0C0RvM/YgDQURp401zWa0PNW73oikfY9sTEi X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a05:6902:1209:b0:dc6:9e4a:f950 with SMTP id s9-20020a056902120900b00dc69e4af950mr4085428ybu.3.1708460604213; Tue, 20 Feb 2024 12:23:24 -0800 (PST) Date: Tue, 20 Feb 2024 20:23:08 +0000 In-Reply-To: <20240220202310.2489614-1-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: <20240220202310.2489614-1-vdonnefort@google.com> X-Mailer: git-send-email 2.44.0.rc0.258.g7320e95886-goog Message-ID: <20240220202310.2489614-5-vdonnefort@google.com> Subject: [PATCH v18 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. Mapping will prevent snapshot and buffer size modifications. Signed-off-by: Vincent Donnefort diff --git a/include/uapi/linux/trace_mmap.h b/include/uapi/linux/trace_mmap.h index ffcd8dfcaa4f..d25b9d504a7c 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 8ae7c2cb63a0..67ce7b367edb 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1176,6 +1176,12 @@ 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); @@ -1308,7 +1314,7 @@ 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; } @@ -6535,7 +6541,7 @@ 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) @@ -8654,15 +8660,31 @@ 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++; @@ -8675,6 +8697,110 @@ 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; +} + +#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; + + ring_buffer_unmap(iter->array_buffer->buffer, iter->cpu_file); + put_snapshot_map(iter->tr); +} + +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 || vma->vm_flags & VM_EXEC) + return -EPERM; + + vm_flags_mod(vma, VM_DONTCOPY | VM_DONTDUMP, VM_MAYWRITE); + vma->vm_ops = &tracing_buffers_vmops; + + ret = get_snapshot_map(iter->tr); + if (ret) + return ret; + + ret = ring_buffer_map(iter->array_buffer->buffer, iter->cpu_file); + if (ret) + put_snapshot_map(iter->tr); + + return ret; +} + static const struct file_operations tracing_buffers_fops = { .open = tracing_buffers_open, .read = tracing_buffers_read, @@ -8683,6 +8809,7 @@ 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 bd312e9afe25..8a96e7a89e6b 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;