From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 33FE82F3C0E for ; Tue, 10 Mar 2026 14:35:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773153354; cv=none; b=FsGu9hxf9bWaGoNSVMcyJIpWj0tLHg33x0FXNr4mie7RNq5Obs2911F+DJwKjH29XHweLL8myj2nmITLCPcEdV5F+X9qr4FnOvwaEX5R9UUMP3ps4JVIeCL0YdNV6rZ7ICPPGSZizexWeaV5dP1+eYA1Be4DSab2Rno4FwG1YW8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773153354; c=relaxed/simple; bh=m+AXGtGr9Wc0yOUUD88NFqcn26FV9ZVrr9knxPb4/qk=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=ZTa+mgF4Mpo+Wi4eGT/IObU+8B9JqkSnX/F37RwIZy07WbESK8+SSOlTnD/Dg3Ckuq6fizyaERk6dRO92JKwyClg3oapvjZuiNLcPOvZFaTYy442SOKWuIoyF5d8G8gej+/L2s6aLMAqILrvVQ+M2vBJgUIzNXw/SIHKnX4m79k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XW+Kgz0H; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XW+Kgz0H" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 07200C2BCB3; Tue, 10 Mar 2026 14:35:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773153354; bh=m+AXGtGr9Wc0yOUUD88NFqcn26FV9ZVrr9knxPb4/qk=; h=Date:From:To:Cc:Subject:References:From; b=XW+Kgz0HiCLq6ZpdBKH+P+OKyPVpIZAA1hw5H4QvDyP3AD/iGw1Oc2PEj12u1axCu 2nYxDClgUsB4WytU5WxQnEEeZWzmPp06SNXSH0SgVraElfgIb2+wSYy3nVL0m4ZFV3 JWnK7YDsHGQRiyYHmD+IfYD6GOx1dMs2RHKQejcG4zO7iJdF5et5AWZ8V045z39Kgm DWrprbmzzT/h0yy2ESJfUUF+qzdB+ChwJSIfmJMfhyUJT8rt5ZCl0MJ0oWJrr9TCkT Q+ET3yDgCE9333VhQ6EV7ed5lDv+/2MfaLMAsT0VUjqr9891cxO9alKOwgRvpxP3tH dWt2UMFhddRHw== Received: from rostedt by gandalf with local (Exim 4.99.1) (envelope-from ) id 1vzyBo-00000002Zdm-0Va2; Tue, 10 Mar 2026 10:36:04 -0400 Message-ID: <20260310143603.983354111@kernel.org> User-Agent: quilt/0.69 Date: Tue, 10 Mar 2026 10:35:24 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Vincent Donnefort Subject: [for-next][PATCH 09/18] tracing: Add events to trace remotes References: <20260310143515.132579088@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 From: Vincent Donnefort An event is predefined point in the writer code that allows to log data. Following the same scheme as kernel events, add remote events, described to user-space within the events/ tracefs directory found in the corresponding trace remote. Remote events are expected to be described during the trace remote registration. Add also a .enable_event callback for trace_remote to toggle the event logging, if supported. Link: https://patch.msgid.link/20260309162516.2623589-10-vdonnefort@google.com Reviewed-by: Steven Rostedt (Google) Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt (Google) --- include/linux/trace_remote.h | 7 +- include/linux/trace_remote_event.h | 23 +++ kernel/trace/trace_remote.c | 264 ++++++++++++++++++++++++++++- 3 files changed, 288 insertions(+), 6 deletions(-) create mode 100644 include/linux/trace_remote_event.h diff --git a/include/linux/trace_remote.h b/include/linux/trace_remote.h index 090c58b7d92b..fcd1d46ea466 100644 --- a/include/linux/trace_remote.h +++ b/include/linux/trace_remote.h @@ -5,6 +5,7 @@ #include #include +#include /** * struct trace_remote_callbacks - Callbacks used by Tracefs to control the remote @@ -23,6 +24,8 @@ * @reset: Called on `echo 0 > trace`. It is expected from the * remote to reset all ring-buffer pages. * new reader-page from the @cpu ring-buffer. + * @enable_event: Called on events/event_name/enable. It is expected from + * the remote to allow the writing event @id. */ struct trace_remote_callbacks { int (*init)(struct dentry *d, void *priv); @@ -31,9 +34,11 @@ struct trace_remote_callbacks { int (*enable_tracing)(bool enable, void *priv); int (*swap_reader_page)(unsigned int cpu, void *priv); int (*reset)(unsigned int cpu, void *priv); + int (*enable_event)(unsigned short id, bool enable, void *priv); }; -int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs, void *priv); +int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs, void *priv, + struct remote_event *events, size_t nr_events); int trace_remote_alloc_buffer(struct trace_buffer_desc *desc, size_t desc_size, size_t buffer_size, const struct cpumask *cpumask); diff --git a/include/linux/trace_remote_event.h b/include/linux/trace_remote_event.h new file mode 100644 index 000000000000..a4449008a075 --- /dev/null +++ b/include/linux/trace_remote_event.h @@ -0,0 +1,23 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef _LINUX_TRACE_REMOTE_EVENTS_H +#define _LINUX_TRACE_REMOTE_EVENTS_H + +struct trace_remote; +struct trace_event_fields; + +struct remote_event_hdr { + unsigned short id; +}; + +#define REMOTE_EVENT_NAME_MAX 30 +struct remote_event { + char name[REMOTE_EVENT_NAME_MAX]; + unsigned short id; + bool enabled; + struct trace_remote *remote; + struct trace_event_fields *fields; + char *print_fmt; + void (*print)(void *evt, struct trace_seq *seq); +}; +#endif diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c index 294d051dcef1..0d0af53c0ce9 100644 --- a/kernel/trace/trace_remote.c +++ b/kernel/trace/trace_remote.c @@ -31,6 +31,7 @@ struct trace_remote_iterator { u64 ts; struct ring_buffer_iter *rb_iter; struct ring_buffer_iter **rb_iters; + struct remote_event_hdr *evt; int cpu; int evt_cpu; loff_t pos; @@ -42,6 +43,10 @@ struct trace_remote { void *priv; struct trace_buffer *trace_buffer; struct trace_buffer_desc *trace_buffer_desc; + struct dentry *dentry; + struct eventfs_inode *eventfs; + struct remote_event *events; + unsigned long nr_events; unsigned long trace_buffer_size; struct ring_buffer_remote rb_remote; struct mutex lock; @@ -168,7 +173,8 @@ static void trace_remote_reset(struct trace_remote *remote, int cpu) static ssize_t tracing_on_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos) { - struct trace_remote *remote = filp->private_data; + struct seq_file *seq = filp->private_data; + struct trace_remote *remote = seq->private; unsigned long val; int ret; @@ -197,7 +203,8 @@ DEFINE_SHOW_STORE_ATTRIBUTE(tracing_on); static ssize_t buffer_size_kb_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos) { - struct trace_remote *remote = filp->private_data; + struct seq_file *seq = filp->private_data; + struct trace_remote *remote = seq->private; unsigned long val; int ret; @@ -484,16 +491,19 @@ __peek_event(struct trace_remote_iterator *iter, int cpu, u64 *ts, unsigned long static bool trace_remote_iter_read_event(struct trace_remote_iterator *iter) { struct trace_buffer *trace_buffer = iter->remote->trace_buffer; + struct ring_buffer_event *rb_evt; int cpu = iter->cpu; if (cpu != RING_BUFFER_ALL_CPUS) { if (ring_buffer_empty_cpu(trace_buffer, cpu)) return false; - if (!__peek_event(iter, cpu, &iter->ts, &iter->lost_events)) + rb_evt = __peek_event(iter, cpu, &iter->ts, &iter->lost_events); + if (!rb_evt) return false; iter->evt_cpu = cpu; + iter->evt = ring_buffer_event_data(rb_evt); return true; } @@ -505,7 +515,8 @@ static bool trace_remote_iter_read_event(struct trace_remote_iterator *iter) if (ring_buffer_empty_cpu(trace_buffer, cpu)) continue; - if (!__peek_event(iter, cpu, &ts, &lost_events)) + rb_evt = __peek_event(iter, cpu, &ts, &lost_events); + if (!rb_evt) continue; if (ts >= iter->ts) @@ -513,6 +524,7 @@ static bool trace_remote_iter_read_event(struct trace_remote_iterator *iter) iter->ts = ts; iter->evt_cpu = cpu; + iter->evt = ring_buffer_event_data(rb_evt); iter->lost_events = lost_events; } @@ -533,8 +545,11 @@ static void trace_remote_iter_move(struct trace_remote_iterator *iter) } } +static struct remote_event *trace_remote_find_event(struct trace_remote *remote, unsigned short id); + static int trace_remote_iter_print_event(struct trace_remote_iterator *iter) { + struct remote_event *evt; unsigned long usecs_rem; u64 ts = iter->ts; @@ -548,6 +563,12 @@ static int trace_remote_iter_print_event(struct trace_remote_iterator *iter) trace_seq_printf(&iter->seq, "[%03d]\t%5llu.%06lu: ", iter->evt_cpu, ts, usecs_rem); + evt = trace_remote_find_event(iter->remote, iter->evt->id); + if (!evt) + trace_seq_printf(&iter->seq, "UNKNOWN id=%d\n", iter->evt->id); + else + evt->print(iter->evt, &iter->seq); + return trace_seq_has_overflowed(&iter->seq) ? -EOVERFLOW : 0; } @@ -829,6 +850,8 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo goto err; } + remote->dentry = remote_d; + return 0; err: @@ -842,6 +865,9 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo return -ENOMEM; } +static int trace_remote_register_events(const char *remote_name, struct trace_remote *remote, + struct remote_event *events, size_t nr_events); + /** * trace_remote_register() - Register a Tracefs remote * @name: Name of the remote, used for the Tracefs remotes/ directory. @@ -860,7 +886,8 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo * * Return: 0 on success, negative error code on failure. */ -int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs, void *priv) +int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs, void *priv, + struct remote_event *events, size_t nr_events) { struct trace_remote *remote; int ret; @@ -881,6 +908,13 @@ int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs, return -ENOMEM; } + ret = trace_remote_register_events(name, remote, events, nr_events); + if (ret) { + pr_err("Failed to register events for trace remote '%s' (%d)\n", + name, ret); + return ret; + } + ret = cbs->init ? cbs->init(remote->dentry, priv) : 0; if (ret) pr_err("Init failed for trace remote '%s' (%d)\n", name, ret); @@ -976,3 +1010,223 @@ int trace_remote_alloc_buffer(struct trace_buffer_desc *desc, size_t desc_size, return ret; } EXPORT_SYMBOL_GPL(trace_remote_alloc_buffer); + +static int +trace_remote_enable_event(struct trace_remote *remote, struct remote_event *evt, bool enable) +{ + int ret; + + lockdep_assert_held(&remote->lock); + + if (evt->enabled == enable) + return 0; + + ret = remote->cbs->enable_event(evt->id, enable, remote->priv); + if (ret) + return ret; + + evt->enabled = enable; + + return 0; +} + +static int remote_event_enable_show(struct seq_file *s, void *unused) +{ + struct remote_event *evt = s->private; + + seq_printf(s, "%d\n", evt->enabled); + + return 0; +} + +static ssize_t remote_event_enable_write(struct file *filp, const char __user *ubuf, + size_t count, loff_t *ppos) +{ + struct seq_file *seq = filp->private_data; + struct remote_event *evt = seq->private; + struct trace_remote *remote = evt->remote; + u8 enable; + int ret; + + ret = kstrtou8_from_user(ubuf, count, 10, &enable); + if (ret) + return ret; + + guard(mutex)(&remote->lock); + + ret = trace_remote_enable_event(remote, evt, enable); + if (ret) + return ret; + + return count; +} +DEFINE_SHOW_STORE_ATTRIBUTE(remote_event_enable); + +static int remote_event_id_show(struct seq_file *s, void *unused) +{ + struct remote_event *evt = s->private; + + seq_printf(s, "%d\n", evt->id); + + return 0; +} +DEFINE_SHOW_ATTRIBUTE(remote_event_id); + +static int remote_event_format_show(struct seq_file *s, void *unused) +{ + size_t offset = sizeof(struct remote_event_hdr); + struct remote_event *evt = s->private; + struct trace_event_fields *field; + + seq_printf(s, "name: %s\n", evt->name); + seq_printf(s, "ID: %d\n", evt->id); + seq_puts(s, + "format:\n\tfield:unsigned short common_type;\toffset:0;\tsize:2;\tsigned:0;\n\n"); + + field = &evt->fields[0]; + while (field->name) { + seq_printf(s, "\tfield:%s %s;\toffset:%zu;\tsize:%u;\tsigned:%d;\n", + field->type, field->name, offset, field->size, + field->is_signed); + offset += field->size; + field++; + } + + if (field != &evt->fields[0]) + seq_puts(s, "\n"); + + seq_printf(s, "print fmt: %s\n", evt->print_fmt); + + return 0; +} +DEFINE_SHOW_ATTRIBUTE(remote_event_format); + +static int remote_event_callback(const char *name, umode_t *mode, void **data, + const struct file_operations **fops) +{ + if (!strcmp(name, "enable")) { + *mode = TRACEFS_MODE_WRITE; + *fops = &remote_event_enable_fops; + return 1; + } + + if (!strcmp(name, "id")) { + *mode = TRACEFS_MODE_READ; + *fops = &remote_event_id_fops; + return 1; + } + + if (!strcmp(name, "format")) { + *mode = TRACEFS_MODE_READ; + *fops = &remote_event_format_fops; + return 1; + } + + return 0; +} + +static int trace_remote_init_eventfs(const char *remote_name, struct trace_remote *remote, + struct remote_event *evt) +{ + struct eventfs_inode *eventfs = remote->eventfs; + static struct eventfs_entry entries[] = { + { + .name = "enable", + .callback = remote_event_callback, + }, { + .name = "id", + .callback = remote_event_callback, + }, { + .name = "format", + .callback = remote_event_callback, + } + }; + bool eventfs_create = false; + + if (!eventfs) { + eventfs = eventfs_create_events_dir("events", remote->dentry, NULL, 0, NULL); + if (IS_ERR(eventfs)) + return PTR_ERR(eventfs); + + /* + * Create similar hierarchy as local events even if a single system is supported at + * the moment + */ + eventfs = eventfs_create_dir(remote_name, eventfs, NULL, 0, NULL); + if (IS_ERR(eventfs)) + return PTR_ERR(eventfs); + + remote->eventfs = eventfs; + eventfs_create = true; + } + + eventfs = eventfs_create_dir(evt->name, eventfs, entries, ARRAY_SIZE(entries), evt); + if (IS_ERR(eventfs)) { + if (eventfs_create) { + eventfs_remove_events_dir(remote->eventfs); + remote->eventfs = NULL; + } + return PTR_ERR(eventfs); + } + + return 0; +} + +static int trace_remote_attach_events(struct trace_remote *remote, struct remote_event *events, + size_t nr_events) +{ + int i; + + for (i = 0; i < nr_events; i++) { + struct remote_event *evt = &events[i]; + + if (evt->remote) + return -EEXIST; + + evt->remote = remote; + + /* We need events to be sorted for efficient lookup */ + if (i && evt->id <= events[i - 1].id) + return -EINVAL; + } + + remote->events = events; + remote->nr_events = nr_events; + + return 0; +} + +static int trace_remote_register_events(const char *remote_name, struct trace_remote *remote, + struct remote_event *events, size_t nr_events) +{ + int i, ret; + + ret = trace_remote_attach_events(remote, events, nr_events); + if (ret) + return ret; + + for (i = 0; i < nr_events; i++) { + struct remote_event *evt = &events[i]; + + ret = trace_remote_init_eventfs(remote_name, remote, evt); + if (ret) + pr_warn("Failed to init eventfs for event '%s' (%d)", + evt->name, ret); + } + + return 0; +} + +static int __cmp_events(const void *key, const void *data) +{ + const struct remote_event *evt = data; + int id = (int)((long)key); + + return id - (int)evt->id; +} + +static struct remote_event *trace_remote_find_event(struct trace_remote *remote, unsigned short id) +{ + return bsearch((const void *)(unsigned long)id, remote->events, remote->nr_events, + sizeof(*remote->events), __cmp_events); +} -- 2.51.0