kernel/linux.git/samples/trace_events, branch v6.6.132

tracing: Verify event formats that have "%*p.."

2025-05-02T05:50:37+00:00

[ Upstream commit ea8d7647f9ddf1f81e2027ed305299797299aa03 ] The trace event verifier checks the formats of trace events to make sure that they do not point at memory that is not in the trace event itself or in data that will never be freed. If an event references data that was allocated when the event triggered and that same data is freed before the event is read, then the kernel can crash by reading freed memory. The verifier runs at boot up (or module load) and scans the print formats of the events and checks their arguments to make sure that dereferenced pointers are safe. If the format uses "%*p.." the verifier will ignore it, and that could be dangerous. Cover this case as well. Also add to the sample code a use case of "%*pbl". Link: https://lore.kernel.org/all/bcba4d76-2c3f-4d11-baf0-02905db953dd@oracle.com/ Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Fixes: 5013f454a352c ("tracing: Add check of trace event print fmts for dereferencing pointers") Link: https://lore.kernel.org/20250327195311.2d89ec66@gandalf.local.home Reported-by: Libo Chen Reviewed-by: Libo Chen Tested-by: Libo Chen Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin

tracing: Add __print_dynamic_array() helper

2025-05-02T05:50:37+00:00

[ Upstream commit e52750fb1458ae9ea5860a08ed7a149185bc5b97 ] When printing a dynamic array in a trace event, the method is rather ugly. It has the format of: __print_array(__get_dynamic_array(array), __get_dynmaic_array_len(array) / el_size, el_size) Since dynamic arrays are known to the tracing infrastructure, create a helper macro that does the above for you. __print_dynamic_array(array, el_size) Which would expand to the same output. Signed-off-by: Steven Rostedt (Google) Signed-off-by: Avadhut Naik Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Qiuxu Zhuo Link: https://lore.kernel.org/r/20241022194158.110073-3-avadhut.naik@amd.com Stable-dep-of: ea8d7647f9dd ("tracing: Verify event formats that have "%*p.."") Signed-off-by: Sasha Levin

tracing: Add __string_len() example

2025-05-02T05:50:36+00:00

[ Upstream commit dd6ae6d90a84d4bec49887c7aa2b22aa1c8b2897 ] There's no example code that uses __string_len(), and since the sample code is used for testing the event logic, add a use case. Link: https://lore.kernel.org/linux-trace-kernel/20240223152827.5f9f78e2@gandalf.local.home Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Signed-off-by: Steven Rostedt (Google) Stable-dep-of: ea8d7647f9dd ("tracing: Verify event formats that have "%*p.."") Signed-off-by: Sasha Levin

tracing: Fix cpumask() example typo

2022-12-14T16:17:55+00:00

The sample code for using cpumask used the wrong field for the __get_cpumask() helper. It used "cpus" which is the bitmask (but would still give a proper example) instead of the "cpum" that was there to be used. Although it produces the same output, fix it, because it's an example and is confusing in how to properly use the cpumask() macro. Link: https://lore.kernel.org/linux-trace-kernel/20221213221227.56560374@gandalf.local.home Cc: Andrew Morton Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google)

tracing: Add __cpumask to denote a trace event field that is a cpumask_t

2022-11-24T00:08:30+00:00

The trace events have a __bitmask field that can be used for anything that requires bitmasks. Although currently it is only used for CPU masks, it could be used in the future for any type of bitmasks. There is some user space tooling that wants to know if a field is a CPU mask and not just some random unsigned long bitmask. Introduce "__cpumask()" helper functions that work the same as the current __bitmask() helpers but displays in the format file: field:__data_loc cpumask_t *[] mask; offset:36; size:4; signed:0; Instead of: field:__data_loc unsigned long[] mask; offset:32; size:4; signed:0; The main difference is the type. Instead of "unsigned long" it is "cpumask_t *". Note, this type field needs to be a real type in the __dynamic_array() logic that both __cpumask and__bitmask use, but the comparison field requires it to be a scalar type whereas cpumask_t is a structure (non-scalar). But everything works when making it a pointer. Valentin added changes to remove the need of passing in "nr_bits" and the __cpumask will always use nr_cpumask_bits as its size. Link: https://lkml.kernel.org/r/20221014080456.1d32b989@rorschach.local.home Requested-by: Valentin Schneider Reviewed-by: Valentin Schneider Signed-off-by: Valentin Schneider Signed-off-by: Steven Rostedt (Google)

tracing: Add example and documentation for new __vstring() macro

2022-07-24T23:11:17+00:00

Update the sample trace events to include an example that uses the new __vstring() helpers for TRACE_EVENTS. Link: https://lkml.kernel.org/r/20220715175555.16375a3b@gandalf.local.home Signed-off-by: Steven Rostedt (Google)

sched/tracing: Append prev_state to tp args instead

2022-05-11T22:37:11+00:00

Commit fa2c3254d7cf (sched/tracing: Don't re-read p->state when emitting sched_switch event, 2022-01-20) added a new prev_state argument to the sched_switch tracepoint, before the prev task_struct pointer. This reordering of arguments broke BPF programs that use the raw tracepoint (e.g. tp_btf programs). The type of the second argument has changed and existing programs that assume a task_struct* argument (e.g. for bpf_task_storage access) will now fail to verify. If we instead append the new argument to the end, all existing programs would continue to work and can conditionally extract the prev_state argument on supported kernel versions. Fixes: fa2c3254d7cf (sched/tracing: Don't re-read p->state when emitting sched_switch event, 2022-01-20) Signed-off-by: Delyan Kratunov Signed-off-by: Peter Zijlstra (Intel) Acked-by: Steven Rostedt (Google) Link: https://lkml.kernel.org/r/c8a6930dfdd58a4a5755fc01732675472979732b.camel@fb.com

Merge tag 'trace-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

2022-03-23T18:40:25+00:00

Pull tracing updates from Steven Rostedt: - New user_events interface. User space can register an event with the kernel describing the format of the event. Then it will receive a byte in a page mapping that it can check against. A privileged task can then enable that event like any other event, which will change the mapped byte to true, telling the user space application to start writing the event to the tracing buffer. - Add new "ftrace_boot_snapshot" kernel command line parameter. When set, the tracing buffer will be saved in the snapshot buffer at boot up when the kernel hands things over to user space. This will keep the traces that happened at boot up available even if user space boot up has tracing as well. - Have TRACE_EVENT_ENUM() also update trace event field type descriptions. Thus if a static array defines its size with an enum, the user space trace event parsers can still know how to parse that array. - Add new TRACE_CUSTOM_EVENT() macro. This acts the same as the TRACE_EVENT() macro, but will attach to an existing tracepoint. This will make one tracepoint be able to trace different content and not be stuck at only what the original TRACE_EVENT() macro exports. - Fixes to tracing error logging. - Better saving of cmdlines to PIDs when tracing (use the wakeup events for mapping). * tag 'trace-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (30 commits) tracing: Have type enum modifications copy the strings user_events: Add trace event call as root for low permission cases tracing/user_events: Use alloc_pages instead of kzalloc() for register pages tracing: Add snapshot at end of kernel boot up tracing: Have TRACE_DEFINE_ENUM affect trace event types as well tracing: Fix strncpy warning in trace_events_synth.c user_events: Prevent dyn_event delete racing with ioctl add/delete tracing: Add TRACE_CUSTOM_EVENT() macro tracing: Move the defines to create TRACE_EVENTS into their own files tracing: Add sample code for custom trace events tracing: Allow custom events to be added to the tracefs directory tracing: Fix last_cmd_set() string management in histogram code user_events: Fix potential uninitialized pointer while parsing field tracing: Fix allocation of last_cmd in last_cmd_set() user_events: Add documentation file user_events: Add sample code for typical usage user_events: Add self-test for validator boundaries user_events: Add self-test for perf_event integration user_events: Add self-test for dynamic_events integration user_events: Add self-test for ftrace integration ...

tracing: Add TRACE_CUSTOM_EVENT() macro

2022-03-11T16:49:24+00:00

To make it really easy to add custom events from modules, add a TRACE_CUSTOM_EVENT() macro that acts just like the TRACE_EVENT() macro, but creates a custom event to an already existing tracepoint. The trace_custom_sched.[ch] has been updated to use this new macro to show how simple it is. Link: https://lkml.kernel.org/r/20220303220625.738622494@goodmis.org Cc: Ingo Molnar Cc: Andrew Morton Cc: Joel Fernandes Cc: Peter Zijlstra Cc: Masami Hiramatsu Cc: Tom Zanussi Signed-off-by: Steven Rostedt (Google)

tracing: Add sample code for custom trace events

2022-03-11T16:48:43+00:00

Add sample code to show how to create custom trace events in the tracefs directory that can be enabled and modified like any event in tracefs (including triggers, histograms, synthetic events and event probes). The example is creating a custom sched_switch and a sched_waking to limit what is recorded: If the custom sched switch only records the prev_prio, next_prio and next_pid, it can bring the size from 64 bytes per event, down to just 16 bytes! If sched_waking only records the prio and pid of the woken event, it will bring the size down from 36 bytes to 12 bytes per event. This will allow for a much smaller footprint into the ring buffer and keep more events from dropping. Link: https://lkml.kernel.org/r/20220303220625.369226746@goodmis.org Cc: Ingo Molnar Cc: Andrew Morton Cc: Peter Zijlstra Cc: Masami Hiramatsu Cc: Tom Zanussi Suggested-by: Joel Fernandes Signed-off-by: Steven Rostedt (Google)