From patchwork Fri May 10 14:04:32 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Donnefort X-Patchwork-Id: 13661639 Received: from mail-wm1-f74.google.com (mail-wm1-f74.google.com [209.85.128.74]) (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 49C6217082E for ; Fri, 10 May 2024 14:04:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715349890; cv=none; b=qreSa+flXFqpcAFSgJytADYHMPZCoQvPqMzNBrr5WtXIo5sjP1kzBYGR9BqlYSpCTujAwMj2QP7P+3BC7hatEFISJ5y1tv76IacPMyk18WzZg5X7Bu7awrUlZQsDVUiAWMTey0PhDtfRnFboJlGBR9p7KUS5M/0M0j8P55Suxm8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715349890; c=relaxed/simple; bh=aRlFwN6lm5I2Rw2uHCFf4kzQfwJ7ZvwKSUHjdJiCmPA=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=dd9VNXb4cwACUZxny8zghYaI/QEjeKxe3Kt2yyxlrphSnYJbU/p6R9fTIqmhayYbrzVqY6GODziuyGu5fkuCbujIPlNjxD8x1PlCGy9f9D6/d6CgBrKU1OUeK+BCK69c8oS0YKPiHzprB1EuUSzoKl3tSyZt02LKL4fmVSS9GG4= 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=kZcL8/m3; arc=none smtp.client-ip=209.85.128.74 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="kZcL8/m3" Received: by mail-wm1-f74.google.com with SMTP id 5b1f17b1804b1-41fda32e6c0so8198025e9.1 for ; Fri, 10 May 2024 07:04:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1715349887; x=1715954687; 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=7zdfkQQHQ+TrC3jj6DAXbeUjEu5Qb/gD5sIE30hR3P0=; b=kZcL8/m3ihofupDQPBTi+mNqFnxGO52580kyED2H6LeCkEoRpg3FiVaPZ3emqPKQIu ZAb/liSTgUXpr4CnAZDs3dFjPivBCDxVluKSiPSj8w1X2pemBXR54B3JgtBDewOmKL+T S40GFhSrzELbhtxYke3A1dJaH56BfPlweudeI3HFWpAQKfaVZda/1uZUnuB7bsSNzxOJ bISk1O8sn+VmbqHSMazPEjBvQqC7KeAcue07W3zFZG4bzV0w0h7d4X0+J41d8SpXzcVu mfMM6srpImno7waog2o20YAPtYeqHtFc2JKDY+VCuFRszUR8G6lM9EJGIfA54bqW5z0V sQyQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1715349887; x=1715954687; 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=7zdfkQQHQ+TrC3jj6DAXbeUjEu5Qb/gD5sIE30hR3P0=; b=KWBxwCOKoe1HI92va67JWo29P70rJ7leY/MXY+Lwh0Yb8c5BQxM0GSD67pEzWxq+35 eepPoNV58djMsx1KEn7WbCAZvz+wrEVqYrlRB4Sg5uWKA41c3pinYpeUWFpsr0BBxnAn Dz2fd6umIDN09R56HBshTYY0TqWmtfvQSGP39vIxS1Y2B+P0vjS+M4ghtz/XiBePeUY8 t4DAnoWGvQaQ5Y6QT3R4xsB/gTTHOA8RwntaTd0ezuG7LNITetGkdoOZdifcsrLdxEyO EVfbKqtuBc0CvvxcyCkhxT0+Y3uqgyuZMfaLKyWrqCtGObLMu63czPLYxZxkhK+Ywm/G 6VRg== X-Forwarded-Encrypted: i=1; AJvYcCV4mOTFcj6J8dlII33HgTaYaLm47xIMn/+ObhI7wcSqtr4DWQmw0/nOzTTtYNiO0R+5ShjXmM/EHTvmcMGqQHIjwfWFQrAoH16mkXSOhiIYNTFq X-Gm-Message-State: AOJu0Yy/cCj8QjDXlOOC2Dt7yVLbRoIlEJDnykWlPDG9NQuJb/XjY2ZB 5GOxAjgIKgPdZ9RA1cl68UV/7pQ/jSLjas1day3+6c3aOCSIVEpwTo3ah/csoyTlQhYmjFEvmSz /6thSiWAu932NQG+ayw== X-Google-Smtp-Source: AGHT+IFmbfbkyt1cuaCw7Z9TpcR3i/kvhX4wMWaVaTY6+kkbiriQkTVeu4WPHk+cGdtSa64MbF2oPERzDLCphX/v X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a05:600c:580a:b0:41b:e416:31e3 with SMTP id 5b1f17b1804b1-41fbd0b952cmr185995e9.3.1715349886925; Fri, 10 May 2024 07:04:46 -0700 (PDT) Date: Fri, 10 May 2024 15:04:32 +0100 In-Reply-To: <20240510140435.3550353-1-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: <20240510140435.3550353-1-vdonnefort@google.com> X-Mailer: git-send-email 2.45.0.118.g7fe29c98d7-goog Message-ID: <20240510140435.3550353-4-vdonnefort@google.com> Subject: [PATCH v23 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 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;