From: Masami Hiramatsu (Google) <[email protected]> Add a self-destractive test for the persistent ring buffer. This will invalidate some sub-buffer pages 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 record 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_SELFTEST and you have to setup the kernel cmdline; reserve_mem=20M:2M:trace trace_instance=ptracingtest^traceoff@trace panic=1 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) <[email protected]> --- Changes in v10: - Add entry_bytes test. - Do not compile test code if CONFIG_RING_BUFFER_PERSISTENT_SELFTEST=n. Changes in v9: - Test also reader pages. --- 0 files changed 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 *buffer); enum ring_buffer_flags { RB_FL_OVERWRITE = 1 << 0, + RB_FL_TESTING = 1 << 1, }; #ifdef CONFIG_RING_BUFFER diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index e130da35808f..094d5511bb17 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -1202,6 +1202,21 @@ config RING_BUFFER_VALIDATE_TIME_DELTAS Only say Y if you understand what this does, and you still want it enabled. Otherwise say N +config RING_BUFFER_PERSISTENT_SELFTEST + bool "Enable persistent ring buffer selftest" + 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. + 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 b436d2982c5e..cfd895d6b56e 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_SELFTEST + __u32 nr_invalid; + __u32 entry_bytes; +#endif int buffers[]; }; @@ -2077,6 +2081,19 @@ static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer) pr_info("Ring buffer meta [%d] is from previous boot! (%d pages discarded)\n", cpu_buffer->cpu, discarded); + +#ifdef CONFIG_RING_BUFFER_PERSISTENT_SELFTEST + if (meta->nr_invalid) + pr_info("Ring buffer testing [%d] invalid pages: %s (%d/%d)\n", + cpu_buffer->cpu, + (discarded == meta->nr_invalid) ? "PASSED" : "FAILED", + discarded, meta->nr_invalid); + if (meta->entry_bytes) + pr_info("Ring buffer testing [%d] entry_bytes: %s (%ld/%ld)\n", + cpu_buffer->cpu, + (entry_bytes == meta->entry_bytes) ? "PASSED" : "FAILED", + (long)entry_bytes, (long)meta->entry_bytes); +#endif return; invalid: @@ -2557,12 +2574,64 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) kfree(cpu_buffer); } +#ifdef CONFIG_RING_BUFFER_PERSISTENT_SELFTEST +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 = 0; + unsigned long ptr; + int subbuf_size; + int invalid = 0; + int cpu; + int i; + + if (!(buffer->flags & RB_FL_TESTING)) + return; + + guard(preempt)(); + cpu = smp_processor_id(); + + cpu_buffer = buffer->buffers[cpu]; + meta = cpu_buffer->ring_meta; + ptr = (unsigned long)rb_subbufs_from_meta(meta); + subbuf_size = meta->subbuf_size; + + for (i = 0; i < meta->nr_subbufs; i++) { + int idx = meta->buffers[i]; + + dpage = (void *)(ptr + idx * subbuf_size); + /* Skip unused pages */ + if (!local_read(&dpage->commit)) + continue; + + /* Invalidate even pages. */ + if (!(i & 0x1)) { + local_add(subbuf_size + 1, &dpage->commit); + invalid++; + } else { + /* Count total commit bytes. */ + entry_bytes += 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 = invalid; + meta->entry_bytes = entry_bytes; +} +#else /* !CONFIG_RING_BUFFER_PERSISTENT_SELFTEST */ +#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 event, void *data) { struct trace_buffer *buffer = container_of(nb, struct trace_buffer, flush_nb); 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 5e1129b011cb..dc23fa63c789 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -9349,6 +9349,8 @@ static void setup_trace_scratch(struct trace_array *tr, memset(tscratch, 0, size); } +#define TRACE_TEST_PTRACING_NAME "ptracingtest" + static int allocate_trace_buffer(struct trace_array *tr, struct array_buffer *buf, unsigned long size) { @@ -9361,6 +9363,8 @@ allocate_trace_buffer(struct trace_array *tr, struct array_buffer *buf, unsigned buf->tr = tr; if (tr->range_addr_start && tr->range_addr_size) { + if (!strcmp(tr->name, TRACE_TEST_PTRACING_NAME)) + rb_flags |= RB_FL_TESTING; /* Add scratch buffer to handle 128 modules */ buf->buffer = ring_buffer_alloc_range(size, rb_flags, 0, tr->range_addr_start,
