ring-buffer: Add persistent ring buffer invalid-page inject test

Add a self-corrupting test for the persistent ring buffer.

This will inject an erroneous value to some sub-buffer pages (where
the index is even or multiples of 5) in the persistent ring buffer
when the kernel panics, and checks whether the number of detected
invalid pages and the total entry_bytes are the same as the recorded
values after reboot.

This ensures that the kernel can correctly recover a partially
corrupted persistent ring buffer after a reboot or panic.

The test only runs on the persistent ring buffer whose name is
"ptracingtest". The user has to fill it with events before a
kernel panic.

To run the test, enable CONFIG_RING_BUFFER_PERSISTENT_INJECT
and add the following kernel cmdline:

 reserve_mem=20M:2M:trace trace_instance=ptracingtest^traceoff@trace
 panic=1

Run the 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)

Link: https://patch.msgid.link/20260522171051.260140328@kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index e130da35808f..084f34dc6c9f 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -1202,6 +1202,40 @@ 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_INJECT
+	bool "Enable persistent ring buffer error injection test"
+	depends on RING_BUFFER
+	help
+	  This option will have the kernel check if the persistent ring
+	  buffer is named "ptracingtest". and if so, it will corrupt some
+	  of its pages on a kernel panic. This is used to test if the
+	  persistent ring buffer can recover from some of its sub-buffers
+	  being corrupted.
+	  To use this, boot a kernel with a "ptracingtest" persistent
+	  ring buffer, e.g.
+
+	   reserve_mem=20M:2M:trace trace_instance=ptracingtest@trace panic=1
+
+	  And after the 1st boot, run the following commands:
+
+	   cd /sys/kernel/tracing/instances/ptracingtest
+	   echo 1 > events/enable
+	   echo 1 > tracing_on
+	   sleep 3
+	   echo c > /proc/sysrq-trigger
+
+	  After the panic message, the kernel will reboot and will show
+	  the test results in the console output.
+
+	  Note that events for the test ring buffer needs to be enabled
+	  prior to crashing the kernel so that the ring buffer has content
+	  that the test will corrupt.
+	  As the test will corrupt events in the "ptracingtest" persistent
+	  ring buffer, it should not be used for any other purpose other
+	  than this test.
+
+	  If unsure, say N
+
 config MMIOTRACE_TEST
 	tristate "Test module for mmiotrace"
 	depends on MMIOTRACE && m