From nobody Thu Apr 2 17:23:46 2026 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (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 1A48D3ECBC5 for ; Mon, 9 Mar 2026 16:26:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773073578; cv=none; b=Og8Q8keg4b9CclwwkUQNpCkE3z/NxK43Tff8kzrU73NxO6WDu+XO4RVEZ5RHDTiB4gycX2AICH4RH9QkcVXw1MRuRfW06/Zmxtyygxgnu0ER+VY7KwHKmKVcd6OBmFHloltBDoBo+0ECYwDDjWlNjmB0o2mepf2ewlyb9gM5L64= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773073578; c=relaxed/simple; bh=aTgyHxDp9neVUk9ffxwEyT2L4BC7WI4Ggih1iyMO7Ts=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=QhLQRr9QJmntCY2YBwNjFBC7LuQsSBuQtRCYbgKXumQjP2gH2Qai0n+UFcMNXhfIJU+FoiLDOkrZ/7viXmb0YXoAVj6qdatbhtCfLAjBjdmLMX4UNNMX6g+HL/T3TLgz5Xg+gUQyFaWFIBWcnLKudUk4Mh6HA+LrkbEBO896OQ8= 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=Zy0tyG9t; arc=none smtp.client-ip=209.85.128.73 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="Zy0tyG9t" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-4853ac455b2so13016615e9.1 for ; Mon, 09 Mar 2026 09:26:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1773073574; x=1773678374; 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=/ni95EE5mzA8VHJclhnwkrJCQr8lmxEdLL8vuwYxm1Y=; b=Zy0tyG9t/F8aciYaO4eGWkqdo6mo5vGRlWap+faf6SsYbrlXzvM+LZcG8O6JsjNZr1 2LZbiW5SxDPGBEZCeXiPgCR4rMRC1q8IHnfX+bhq7h62nghPhkpbe6phmEcG6iS9Mv3p tLaUVhq2kwYz1hljnfx4JcAXuH15cLylYexPur3DoWSmWm1v5Owi3fJ8O5vnHPfZoCQb XDy799GRWqgqm0k/S6yeSUhN3HAiUHcVFceMvA4KhWekuPo0YdZ9KHAwAZz+xuQ/j1Bu o2/yCaGCp0lYRn5dIBBks7ZXAAFK1O9lL4gqhdAKSh6D99+furuhUmJNKe2VNjblGzwp 6c6Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1773073574; x=1773678374; 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=/ni95EE5mzA8VHJclhnwkrJCQr8lmxEdLL8vuwYxm1Y=; b=WnGtN5HPxJJPXXb0Sb7skkmp5EQ1HU3rgduyGwBChvaTJKNQkhyDukK+zJOWbW6Lgh yR70jRlDREvF56MwAMspQmIZh8nWhoag+xhKCWKBBJ1l+tfU6NsxBprfyJc7zhsSfcys ncEkghJuBnUE6tociX7/vby8xY9R9cf8QboN22JPoDt/ITl0JqP6Z+6k49SVz7spw4Dy UgJmQnDKepzaq7EuItbaZ8zq7VJSU0FdBgfcbJV/KkHOjYnQy3yv0bdu3TPnsH2hF8QY 3EL75K1McRH1M3tlrxMvfkWQYlN3sgQ20JOcGK/Ryc2wrMOcSU410cXhxATJTo4QrZTe 09hQ== X-Forwarded-Encrypted: i=1; AJvYcCWimRUKZWtKxBUAqC0FVDMppM9iqCHZoo24o+sEsH/JMeTFbNhop+Ao1nLdE65fSNuBe6yUFUc3ASLgb7I=@vger.kernel.org X-Gm-Message-State: AOJu0YwjnCEgTVSp50bhwDFtA2mGrxR9K2wiF1dGCWt44d+yAzVYD/pm ILliJCxQezHUNiGTatpFO2C5HuOFyxPBdrAmCVLeCQkx5kXrhPDJs6WPu1t9Zb27VcDvk3tb/I1 HvgJseAfXPKbh5Y10LReAXA== X-Received: from wmqu6.prod.google.com ([2002:a05:600c:19c6:b0:485:2d79:6c75]) (user=vdonnefort job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:1d1e:b0:483:709e:f239 with SMTP id 5b1f17b1804b1-48526951ca9mr205741045e9.22.1773073574278; Mon, 09 Mar 2026 09:26:14 -0700 (PDT) Date: Mon, 9 Mar 2026 16:25:00 +0000 In-Reply-To: <20260309162516.2623589-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260309162516.2623589-1-vdonnefort@google.com> X-Mailer: git-send-email 2.53.0.473.g4a7958ca14-goog Message-ID: <20260309162516.2623589-15-vdonnefort@google.com> Subject: [PATCH v14 14/30] tracing: Add a trace remote module for testing From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, linux-trace-kernel@vger.kernel.org, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, jstultz@google.com, qperret@google.com, will@kernel.org, aneesh.kumar@kernel.org, kernel-team@android.com, linux-kernel@vger.kernel.org, Vincent Donnefort Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a module to help testing the tracefs support for trace remotes. This module: * Use simple_ring_buffer to write into a ring-buffer. * Declare a single "selftest" event that can be triggered from user-space. * Register a "test" trace remote. This is intended to be used by trace remote selftests. Reviewed-by: Steven Rostedt (Google) Signed-off-by: Vincent Donnefort diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index 51c00c8fa175..edfdf139cb02 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -664,6 +664,7 @@ struct dentry *tracefs_create_file(const char *name, um= ode_t mode, fsnotify_create(d_inode(dentry->d_parent), dentry); return tracefs_end_creating(dentry); } +EXPORT_SYMBOL_GPL(tracefs_create_file); =20 static struct dentry *__create_dir(const char *name, struct dentry *parent, const struct inode_operations *ops) diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index edbdd7b38f61..e130da35808f 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -1287,4 +1287,12 @@ config TRACE_REMOTE config SIMPLE_RING_BUFFER bool =20 +config TRACE_REMOTE_TEST + tristate "Test module for remote tracing" + select TRACE_REMOTE + select SIMPLE_RING_BUFFER + help + This trace remote includes a ring-buffer writer implementation using + "simple_ring_buffer". This is solely intending for testing. + endif # FTRACE diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index 2e39b09398b3..d106beca8d7f 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -130,4 +130,6 @@ obj-$(CONFIG_RV) +=3D rv/ =20 obj-$(CONFIG_TRACE_REMOTE) +=3D trace_remote.o obj-$(CONFIG_SIMPLE_RING_BUFFER) +=3D simple_ring_buffer.o +obj-$(CONFIG_TRACE_REMOTE_TEST) +=3D remote_test.o + libftrace-y :=3D ftrace.o diff --git a/kernel/trace/remote_test.c b/kernel/trace/remote_test.c new file mode 100644 index 000000000000..6c1b7701ddae --- /dev/null +++ b/kernel/trace/remote_test.c @@ -0,0 +1,261 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2025 - Google LLC + * Author: Vincent Donnefort + */ + +#include +#include +#include +#include +#include + +#define REMOTE_EVENT_INCLUDE_FILE kernel/trace/remote_test_events.h +#include + +static DEFINE_PER_CPU(struct simple_rb_per_cpu *, simple_rbs); +static struct trace_buffer_desc *remote_test_buffer_desc; + +/* + * The trace_remote lock already serializes accesses from the trace_remote= _callbacks. + * However write_event can still race with load/unload. + */ +static DEFINE_MUTEX(simple_rbs_lock); + +static int remote_test_load_simple_rb(int cpu, struct ring_buffer_desc *rb= _desc) +{ + struct simple_rb_per_cpu *cpu_buffer; + struct simple_buffer_page *bpages; + int ret =3D -ENOMEM; + + cpu_buffer =3D kmalloc_obj(*cpu_buffer); + if (!cpu_buffer) + return ret; + + bpages =3D kmalloc_objs(*bpages, rb_desc->nr_page_va); + if (!bpages) + goto err_free_cpu_buffer; + + ret =3D simple_ring_buffer_init(cpu_buffer, bpages, rb_desc); + if (ret) + goto err_free_bpages; + + scoped_guard(mutex, &simple_rbs_lock) { + WARN_ON(*per_cpu_ptr(&simple_rbs, cpu)); + *per_cpu_ptr(&simple_rbs, cpu) =3D cpu_buffer; + } + + return 0; + +err_free_bpages: + kfree(bpages); + +err_free_cpu_buffer: + kfree(cpu_buffer); + + return ret; +} + +static void remote_test_unload_simple_rb(int cpu) +{ + struct simple_rb_per_cpu *cpu_buffer =3D *per_cpu_ptr(&simple_rbs, cpu); + struct simple_buffer_page *bpages; + + if (!cpu_buffer) + return; + + guard(mutex)(&simple_rbs_lock); + + bpages =3D cpu_buffer->bpages; + simple_ring_buffer_unload(cpu_buffer); + kfree(bpages); + kfree(cpu_buffer); + *per_cpu_ptr(&simple_rbs, cpu) =3D NULL; +} + +static struct trace_buffer_desc *remote_test_load(unsigned long size, void= *unused) +{ + struct ring_buffer_desc *rb_desc; + struct trace_buffer_desc *desc; + size_t desc_size; + int cpu, ret; + + if (WARN_ON(remote_test_buffer_desc)) + return ERR_PTR(-EINVAL); + + desc_size =3D trace_buffer_desc_size(size, num_possible_cpus()); + if (desc_size =3D=3D SIZE_MAX) { + ret =3D -E2BIG; + goto err; + } + + desc =3D kmalloc(desc_size, GFP_KERNEL); + if (!desc) { + ret =3D -ENOMEM; + goto err; + } + + ret =3D trace_remote_alloc_buffer(desc, desc_size, size, cpu_possible_mas= k); + if (ret) + goto err_free_desc; + + for_each_ring_buffer_desc(rb_desc, cpu, desc) { + ret =3D remote_test_load_simple_rb(rb_desc->cpu, rb_desc); + if (ret) + goto err_unload; + } + + remote_test_buffer_desc =3D desc; + + return remote_test_buffer_desc; + +err_unload: + for_each_ring_buffer_desc(rb_desc, cpu, remote_test_buffer_desc) + remote_test_unload_simple_rb(rb_desc->cpu); + trace_remote_free_buffer(remote_test_buffer_desc); + +err_free_desc: + kfree(desc); + +err: + return ERR_PTR(ret); +} + +static void remote_test_unload(struct trace_buffer_desc *desc, void *unuse= d) +{ + struct ring_buffer_desc *rb_desc; + int cpu; + + if (WARN_ON(desc !=3D remote_test_buffer_desc)) + return; + + for_each_ring_buffer_desc(rb_desc, cpu, desc) + remote_test_unload_simple_rb(rb_desc->cpu); + + remote_test_buffer_desc =3D NULL; + trace_remote_free_buffer(desc); + kfree(desc); +} + +static int remote_test_enable_tracing(bool enable, void *unused) +{ + struct ring_buffer_desc *rb_desc; + int cpu; + + if (!remote_test_buffer_desc) + return -ENODEV; + + for_each_ring_buffer_desc(rb_desc, cpu, remote_test_buffer_desc) + WARN_ON(simple_ring_buffer_enable_tracing(*per_cpu_ptr(&simple_rbs, rb_d= esc->cpu), + enable)); + return 0; +} + +static int remote_test_swap_reader_page(unsigned int cpu, void *unused) +{ + struct simple_rb_per_cpu *cpu_buffer; + + if (cpu >=3D NR_CPUS) + return -EINVAL; + + cpu_buffer =3D *per_cpu_ptr(&simple_rbs, cpu); + if (!cpu_buffer) + return -EINVAL; + + return simple_ring_buffer_swap_reader_page(cpu_buffer); +} + +static int remote_test_reset(unsigned int cpu, void *unused) +{ + struct simple_rb_per_cpu *cpu_buffer; + + if (cpu >=3D NR_CPUS) + return -EINVAL; + + cpu_buffer =3D *per_cpu_ptr(&simple_rbs, cpu); + if (!cpu_buffer) + return -EINVAL; + + return simple_ring_buffer_reset(cpu_buffer); +} + +static int remote_test_enable_event(unsigned short id, bool enable, void *= unused) +{ + if (id !=3D REMOTE_TEST_EVENT_ID) + return -EINVAL; + + /* + * Let's just use the struct remote_event enabled field that is turned on= and off by + * trace_remote. This is a bit racy but good enough for a simple test mod= ule. + */ + return 0; +} + +static ssize_t +write_event_write(struct file *filp, const char __user *ubuf, size_t cnt, = loff_t *pos) +{ + struct remote_event_format_selftest *evt_test; + struct simple_rb_per_cpu *cpu_buffer; + unsigned long val; + int ret; + + ret =3D kstrtoul_from_user(ubuf, cnt, 10, &val); + if (ret) + return ret; + + guard(mutex)(&simple_rbs_lock); + + if (!remote_event_selftest.enabled) + return -ENODEV; + + guard(preempt)(); + + cpu_buffer =3D *this_cpu_ptr(&simple_rbs); + if (!cpu_buffer) + return -ENODEV; + + evt_test =3D simple_ring_buffer_reserve(cpu_buffer, + sizeof(struct remote_event_format_selftest), + trace_clock_global()); + if (!evt_test) + return -ENODEV; + + evt_test->hdr.id =3D REMOTE_TEST_EVENT_ID; + evt_test->id =3D val; + + simple_ring_buffer_commit(cpu_buffer); + + return cnt; +} + +static const struct file_operations write_event_fops =3D { + .write =3D write_event_write, +}; + +static int remote_test_init_tracefs(struct dentry *d, void *unused) +{ + return tracefs_create_file("write_event", 0200, d, NULL, &write_event_fop= s) ? + 0 : -ENOMEM; +} + +static struct trace_remote_callbacks trace_remote_callbacks =3D { + .init =3D remote_test_init_tracefs, + .load_trace_buffer =3D remote_test_load, + .unload_trace_buffer =3D remote_test_unload, + .enable_tracing =3D remote_test_enable_tracing, + .swap_reader_page =3D remote_test_swap_reader_page, + .reset =3D remote_test_reset, + .enable_event =3D remote_test_enable_event, +}; + +static int __init remote_test_init(void) +{ + return trace_remote_register("test", &trace_remote_callbacks, NULL, + &remote_event_selftest, 1); +} + +module_init(remote_test_init); + +MODULE_DESCRIPTION("Test module for the trace remote interface"); +MODULE_AUTHOR("Vincent Donnefort"); +MODULE_LICENSE("GPL"); diff --git a/kernel/trace/remote_test_events.h b/kernel/trace/remote_test_e= vents.h new file mode 100644 index 000000000000..26b93b3406fc --- /dev/null +++ b/kernel/trace/remote_test_events.h @@ -0,0 +1,10 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#define REMOTE_TEST_EVENT_ID 1 + +REMOTE_EVENT(selftest, REMOTE_TEST_EVENT_ID, + RE_STRUCT( + re_field(u64, id) + ), + RE_PRINTK("id=3D%llu", __entry->id) +); --=20 2.53.0.473.g4a7958ca14-goog