From nobody Wed Apr 1 13:49:53 2026 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 D2ADC3D647F; Tue, 31 Mar 2026 08:36:33 +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=1774946193; cv=none; b=bOuvygwkJJWzHbhRA74CqNboYg30J1m+RUvyeKEdIfpULCE6jSlz2qJpPEMi/LxLJa8HOmDZqUgHHztE9spxoyfF13bl1MpKwBp0FyqtnTtmLtiMk87pKZ/fLYYUPzRhEUELeb1EBdfUpWbrigUsZfyI3vRF0+onRMMBLL5bBnM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774946193; c=relaxed/simple; bh=DnL/wn8OqAp+2CfNBRsbAhbshuKmA3OfJU3X1O9CUh8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=oYGqW0RGtid+EeVVkjTsqzx3qny1yQATvfmjWyV+q5jnPGAwxyiBh+7M7L8dbdQ2RR9OzAEqxpq+xcVOu3EP8u0LUwPUgAYIReKxgy2TQEHdw7QohvqenlUiUnpj5+uRd7iFkEP0zVb2lE9jIMLpOUCeYjt3lpENzJTpBGGYyOM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HpWe8+Hi; 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="HpWe8+Hi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5BC1DC2BCB0; Tue, 31 Mar 2026 08:36:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774946193; bh=DnL/wn8OqAp+2CfNBRsbAhbshuKmA3OfJU3X1O9CUh8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HpWe8+HihNBuyeuFMELMNnm2dwwQDMBMfFIj5GrcRQzY1hbilC9Sdwz8XWbToZ/TA 0jYaqqPXUYnIPltWNfBWti5hvue6CRPqXA3JQPveC2uj87giG2Ss1YTYmenhUoWuKR ZjmRkmQMTK2gsan+EoCOmpXh4LwuwRb0QZZbpKZlJjyAr1KddjR2c7X6AXKSzGJl6Q 99FpnSka1a3l1skFDetdXgW44Q3hxAsvTWGR76zEVReseiJHI3CU/Odm35epfO2ssY bHywj39L4lETi5LGIYQdVEfTY2r2xWKE8lMsoyr4HIHvM+TNoIgPjcWxOc83lFb/cr sWI5H2lYtjP6Q== From: "Masami Hiramatsu (Google)" To: Steven Rostedt , Catalin Marinas , Will Deacon Cc: Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Ian Rogers , linux-arm-kernel@lists.infradead.org Subject: [PATCH v15 4/5] ring-buffer: Add persistent ring buffer invalid-page inject test Date: Tue, 31 Mar 2026 17:36:30 +0900 Message-ID: <177494619065.71933.9842685686800241005.stgit@mhiramat.tok.corp.google.com> X-Mailer: git-send-email 2.53.0.1118.gaef5881109-goog In-Reply-To: <177494615421.71933.3679132057004156013.stgit@mhiramat.tok.corp.google.com> References: <177494615421.71933.3679132057004156013.stgit@mhiramat.tok.corp.google.com> User-Agent: StGit/0.19 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" Content-Transfer-Encoding: quoted-printable From: Masami Hiramatsu (Google) Add a self-destractive test for the persistent ring buffer. This will inject erroneous value to some sub-buffer pages (where the index is even or multiples of 5) in the persistent ring buffer when kernel gets panic, and check whether the number of detected invalid pages and the total entry_bytes are the same as recorded values after reboot. This can ensure the kernel correctly recover partially corrupted persistent ring buffer when boot. The test only runs on the persistent ring buffer whose name is "ptracingtest". And user has to fill it up with events before kernel panics. To run the test, enable CONFIG_RING_BUFFER_PERSISTENT_INJECT and you have to setup the kernel cmdline; reserve_mem=3D20M:2M:trace trace_instance=3Dptracingtest^traceoff@trace panic=3D1 And run following commands after the 1st boot; cd /sys/kernel/tracing/instances/ptracingtest echo 1 > tracing_on echo 1 > events/enable sleep 3 echo c > /proc/sysrq-trigger After panic message, the kernel will reboot and run the verification on the persistent ring buffer, e.g. Ring buffer meta [2] invalid buffer page detected Ring buffer meta [2] is from previous boot! (318 pages discarded) Ring buffer testing [2] invalid pages: PASSED (318/318) Ring buffer testing [2] entry_bytes: PASSED (1300476/1300476) Signed-off-by: Masami Hiramatsu (Google) --- Changes in v15: - Use pr_warn() for test result. - Inject errors on the page index is multiples of 5 so that this can reproduce contiguous empty pages. Changes in v14: - Rename config to CONFIG_RING_BUFFER_PERSISTENT_INJECT. - Clear meta->nr_invalid/entry_bytes after testing. - Add test commands in config comment. Changes in v10: - Add entry_bytes test. - Do not compile test code if CONFIG_RING_BUFFER_PERSISTENT_SELFTEST=3Dn. Changes in v9: - Test also reader pages. --- include/linux/ring_buffer.h | 1 + kernel/trace/Kconfig | 31 ++++++++++++++++++ kernel/trace/ring_buffer.c | 74 +++++++++++++++++++++++++++++++++++++++= ++++ kernel/trace/trace.c | 4 ++ 4 files changed, 110 insertions(+) diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index 994f52b34344..0670742b2d60 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -238,6 +238,7 @@ int ring_buffer_subbuf_size_get(struct trace_buffer *bu= ffer); =20 enum ring_buffer_flags { RB_FL_OVERWRITE =3D 1 << 0, + RB_FL_TESTING =3D 1 << 1, }; =20 #ifdef CONFIG_RING_BUFFER diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index e130da35808f..07305ed6d745 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -1202,6 +1202,37 @@ config RING_BUFFER_VALIDATE_TIME_DELTAS Only say Y if you understand what this does, and you still want it enabled. Otherwise say N =20 +config RING_BUFFER_PERSISTENT_INJECT + bool "Enable persistent ring buffer error injection test" + depends on RING_BUFFER + help + Run a selftest on the persistent ring buffer which names + "ptracingtest" (and its backup) when panic_on_reboot by + invalidating ring buffer pages. + To use this, boot kernel with "ptracingtest" persistent + ring buffer, e.g. + + reserve_mem=3D20M:2M:trace trace_instance=3Dptracingtest@trace panic= =3D1 + + And after the 1st boot, run test command, like; + + cd /sys/kernel/tracing/instances/ptracingtest + echo 1 > events/enable + echo 1 > tracing_on + sleep 3 + echo c > /proc/sysrq-trigger + + After panic message, the kernel reboots and show test results + on the boot log. + + Note that user has to enable events on the persistent ring + buffer manually to fill up ring buffers before rebooting. + Since this invalidates the data on test target ring buffer, + "ptracingtest" persistent ring buffer must not be used for + actual tracing, but only for testing. + + If unsure, say N + config MMIOTRACE_TEST tristate "Test module for mmiotrace" depends on MMIOTRACE && m diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 5ff632ca3858..fb098b0b4505 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -64,6 +64,10 @@ struct ring_buffer_cpu_meta { unsigned long commit_buffer; __u32 subbuf_size; __u32 nr_subbufs; +#ifdef CONFIG_RING_BUFFER_PERSISTENT_INJECT + __u32 nr_invalid; + __u32 entry_bytes; +#endif int buffers[]; }; =20 @@ -2079,6 +2083,21 @@ static void rb_meta_validate_events(struct ring_buff= er_per_cpu *cpu_buffer) if (discarded) pr_cont(" (%d pages discarded)", discarded); pr_cont("\n"); + +#ifdef CONFIG_RING_BUFFER_PERSISTENT_INJECT + if (meta->nr_invalid) + pr_warn("Ring buffer testing [%d] invalid pages: %s (%d/%d)\n", + cpu_buffer->cpu, + (discarded =3D=3D meta->nr_invalid) ? "PASSED" : "FAILED", + discarded, meta->nr_invalid); + if (meta->entry_bytes) + pr_warn("Ring buffer testing [%d] entry_bytes: %s (%ld/%ld)\n", + cpu_buffer->cpu, + (entry_bytes =3D=3D meta->entry_bytes) ? "PASSED" : "FAILED", + (long)entry_bytes, (long)meta->entry_bytes); + meta->nr_invalid =3D 0; + meta->entry_bytes =3D 0; +#endif return; =20 invalid: @@ -2559,12 +2578,67 @@ static void rb_free_cpu_buffer(struct ring_buffer_p= er_cpu *cpu_buffer) kfree(cpu_buffer); } =20 +#ifdef CONFIG_RING_BUFFER_PERSISTENT_INJECT +static void rb_test_inject_invalid_pages(struct trace_buffer *buffer) +{ + struct ring_buffer_per_cpu *cpu_buffer; + struct ring_buffer_cpu_meta *meta; + struct buffer_data_page *dpage; + u32 entry_bytes =3D 0; + unsigned long ptr; + int subbuf_size; + int invalid =3D 0; + int cpu; + int i; + + if (!(buffer->flags & RB_FL_TESTING)) + return; + + guard(preempt)(); + cpu =3D smp_processor_id(); + + cpu_buffer =3D buffer->buffers[cpu]; + meta =3D cpu_buffer->ring_meta; + ptr =3D (unsigned long)rb_subbufs_from_meta(meta); + subbuf_size =3D meta->subbuf_size; + + for (i =3D 0; i < meta->nr_subbufs; i++) { + int idx =3D meta->buffers[i]; + + dpage =3D (void *)(ptr + idx * subbuf_size); + /* Skip unused pages */ + if (!local_read(&dpage->commit)) + continue; + + /* + * Invalidate even pages or multiples of 5. This will lead 3 + * contiguous invalidated(empty) pages. + */ + if (!(i & 0x1) || !(i % 5)) { + local_add(subbuf_size + 1, &dpage->commit); + invalid++; + } else { + /* Count total commit bytes. */ + entry_bytes +=3D local_read(&dpage->commit); + } + } + + pr_info("Inject invalidated %d pages on CPU%d, total size: %ld\n", + invalid, cpu, (long)entry_bytes); + meta->nr_invalid =3D invalid; + meta->entry_bytes =3D entry_bytes; +} +#else /* !CONFIG_RING_BUFFER_PERSISTENT_INJECT */ +#define rb_test_inject_invalid_pages(buffer) do { } while (0) +#endif + /* Stop recording on a persistent buffer and flush cache if needed. */ static int rb_flush_buffer_cb(struct notifier_block *nb, unsigned long eve= nt, void *data) { struct trace_buffer *buffer =3D container_of(nb, struct trace_buffer, flu= sh_nb); =20 ring_buffer_record_off(buffer); + rb_test_inject_invalid_pages(buffer); arch_ring_buffer_flush_range(buffer->range_addr_start, buffer->range_addr= _end); return NOTIFY_DONE; } diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 4189ec9df6a5..108b0d16badf 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -9366,6 +9366,8 @@ static void setup_trace_scratch(struct trace_array *t= r, memset(tscratch, 0, size); } =20 +#define TRACE_TEST_PTRACING_NAME "ptracingtest" + static int allocate_trace_buffer(struct trace_array *tr, struct array_buffer *buf, un= signed long size) { @@ -9378,6 +9380,8 @@ allocate_trace_buffer(struct trace_array *tr, struct = array_buffer *buf, unsigned buf->tr =3D tr; =20 if (tr->range_addr_start && tr->range_addr_size) { + if (!strcmp(tr->name, TRACE_TEST_PTRACING_NAME)) + rb_flags |=3D RB_FL_TESTING; /* Add scratch buffer to handle 128 modules */ buf->buffer =3D ring_buffer_alloc_range(size, rb_flags, 0, tr->range_addr_start,