linux/kernel/trace/trace_events.c, branch v6.14

tracing: Fix memory leak when reading set_event file

2025-02-21T14:36:12Z

kmemleak reports the following memory leak after reading set_event file: # cat /sys/kernel/tracing/set_event # cat /sys/kernel/debug/kmemleak unreferenced object 0xff110001234449e0 (size 16): comm "cat", pid 13645, jiffies 4294981880 hex dump (first 16 bytes): 01 00 00 00 00 00 00 00 a8 71 e7 84 ff ff ff ff .........q...... backtrace (crc c43abbc): __kmalloc_cache_noprof+0x3ca/0x4b0 s_start+0x72/0x2d0 seq_read_iter+0x265/0x1080 seq_read+0x2c9/0x420 vfs_read+0x166/0xc30 ksys_read+0xf4/0x1d0 do_syscall_64+0x79/0x150 entry_SYSCALL_64_after_hwframe+0x76/0x7e The issue can be reproduced regardless of whether set_event is empty or not. Here is an example about the valid content of set_event. # cat /sys/kernel/tracing/set_event sched:sched_process_fork sched:sched_switch sched:sched_wakeup *:*:mod:trace_events_sample The root cause is that s_next() returns NULL when nothing is found. This results in s_stop() attempting to free a NULL pointer because its parameter is NULL. Fix the issue by freeing the memory appropriately when s_next() fails to find anything. Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20250220031528.7373-1-ahuang12@lenovo.com Fixes: b355247df104 ("tracing: Cache ":mod:" events for modules not loaded yet") Signed-off-by: Adrian Huang Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google)

Merge tag 'trace-v6.14-3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2025-01-24T01:51:16Z

Pull tracing updates from Steven Rostedt: - Cleanup with guard() and free() helpers There were several places in the code that had a lot of "goto out" in the error paths to either unlock a lock or free some memory that was allocated. But this is error prone. Convert the code over to use the guard() and free() helpers that let the compiler unlock locks or free memory when the function exits. - Update the Rust tracepoint code to use the C code too There was some duplication of the tracepoint code for Rust that did the same logic as the C code. Add a helper that makes it possible for both algorithms to use the same logic in one place. - Add poll to trace event hist files It is useful to know when an event is triggered, or even with some filtering. Since hist files of events get updated when active and the event is triggered, allow applications to poll the hist file and wake up when an event is triggered. This will let the application know that the event it is waiting for happened. - Add :mod: command to enable events for current or future modules The function tracer already has a way to enable functions to be traced in modules by writing ":mod:" into set_ftrace_filter. That will enable either all the functions for the module if it is loaded, or if it is not, it will cache that command, and when the module is loaded that matches , its functions will be enabled. This also allows init functions to be traced. But currently events do not have that feature. Add the command where if ':mod:' is written into set_event, then either all the modules events are enabled if it is loaded, or cache it so that the module's events are enabled when it is loaded. This also works from the kernel command line, where "trace_event=:mod:", when the module is loaded at boot up, its events will be enabled then. * tag 'trace-v6.14-3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (26 commits) tracing: Fix output of set_event for some cached module events tracing: Fix allocation of printing set_event file content tracing: Rename update_cache() to update_mod_cache() tracing: Fix #if CONFIG_MODULES to #ifdef CONFIG_MODULES selftests/ftrace: Add test that tests event :mod: commands tracing: Cache ":mod:" events for modules not loaded yet tracing: Add :mod: command to enabled module events selftests/tracing: Add hist poll() support test tracing/hist: Support POLLPRI event for poll on histogram tracing/hist: Add poll(POLLIN) support on hist file tracing: Fix using ret variable in tracing_set_tracer() tracepoint: Reduce duplication of __DO_TRACE_CALL tracing/string: Create and use __free(argv_free) in trace_dynevent.c tracing: Switch trace_stat.c code over to use guard() tracing: Switch trace_stack.c code over to use guard() tracing: Switch trace_osnoise.c code over to use guard() and __free() tracing: Switch trace_events_synth.c code over to use guard() tracing: Switch trace_events_filter.c code over to use guard() tracing: Switch trace_events_trigger.c code over to use guard() tracing: Switch trace_events_hist.c code over to use guard() ...

tracing: Fix output of set_event for some cached module events

2025-01-21T20:23:07Z

The following works fine: ~# echo ':mod:trace_events_sample' > /sys/kernel/tracing/set_event ~# cat /sys/kernel/tracing/set_event *:*:mod:trace_events_sample ~# But if a name is given without a ':' where it can match an event name or system name, the output of the cached events does not include a new line: ~# echo 'foo_bar:mod:trace_events_sample' > /sys/kernel/tracing/set_event ~# cat /sys/kernel/tracing/set_event foo_bar:mod:trace_events_sample~# Add the '\n' to that as well. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20250121151336.6c491844@gandalf.local.home Fixes: b355247df104e ("tracing: Cache ":mod:" events for modules not loaded yet") Signed-off-by: Steven Rostedt (Google)

tracing: Fix allocation of printing set_event file content

2025-01-21T20:22:41Z

The adding of cached events for modules not loaded yet required a descriptor to separate the iteration of events with the iteration of cached events for a module. But the allocation used the size of the pointer and not the size of the contents to allocate its data and caused a slab-out-of-bounds. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Linus Torvalds Link: https://lore.kernel.org/20250121151236.47fcf433@gandalf.local.home Reported-by: Sasha Levin Closes: https://lore.kernel.org/all/Z4_OHKESRSiJcr-b@lappy/ Fixes: b355247df104e ("tracing: Cache ":mod:" events for modules not loaded yet") Signed-off-by: Steven Rostedt (Google)

tracing: Rename update_cache() to update_mod_cache()

2025-01-21T00:09:16Z

The static function in trace_events.c called update_cache() is too generic and conflicts with the function defined in arch/openrisc/include/asm/pgtable.h Rename it to update_mod_cache() to make it less generic. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20250120172756.4ecfb43f@batman.local.home Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202501210550.Ufrj5CRn-lkp@intel.com/ Fixes: b355247df104e ("tracing: Cache ":mod:" events for modules not loaded yet") Signed-off-by: Steven Rostedt (Google)

tracing: Fix #if CONFIG_MODULES to #ifdef CONFIG_MODULES

2025-01-20T18:03:23Z

A typo was introduced when adding the ":mod:" command that did a "#if CONFIG_MODULES" instead of a "#ifdef CONFIG_MODULES". Fix it. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Linus Torvalds Link: https://lore.kernel.org/20250120125745.4ac90ca6@gandalf.local.home Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202501190121.E2CIJuUj-lkp@intel.com/ Fixes: b355247df104e ("tracing: Cache ":mod:" events for modules not loaded yet") Signed-off-by: Steven Rostedt (Google)

tracing: Cache ":mod:" events for modules not loaded yet

2025-01-16T14:41:08Z

When the :mod: command is written into /sys/kernel/tracing/set_event (or that file within an instance), if the module specified after the ":mod:" is not yet loaded, it will store that string internally. When the module is loaded, it will enable the events as if the module was loaded when the string was written into the set_event file. This can also be useful to enable events that are in the init section of the module, as the events are enabled before the init section is executed. This also works on the kernel command line: trace_event=:mod: Will enable the events for when it is loaded. Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Link: https://lore.kernel.org/20250116143533.514730995@goodmis.org Signed-off-by: Steven Rostedt (Google)

tracing: Add :mod: command to enabled module events

2025-01-16T14:41:07Z

Add a :mod: command to enable only events from a given module from the set_events file. echo '*:mod:' > set_events Or echo ':mod:' > set_events Will enable all events for that module. Specific events can also be enabled via: echo ':mod:' > set_events Or echo '::mod:' > set_events Or echo '*::mod:' > set_events The ":mod:" keyword is consistent with the function tracing filter to enable functions from a given module. Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Link: https://lore.kernel.org/20250116143533.214496360@goodmis.org Signed-off-by: Steven Rostedt (Google)

tracing/hist: Add poll(POLLIN) support on hist file

2025-01-07T16:44:49Z

Add poll syscall support on the `hist` file. The Waiter will be waken up when the histogram is updated with POLLIN. Currently, there is no way to wait for a specific event in userspace. So user needs to peek the `trace` periodicaly, or wait on `trace_pipe`. But it is not a good idea to peek at the `trace` for an event that randomly happens. And `trace_pipe` is not coming back until a page is filled with events. This allows a user to wait for a specific event on the `hist` file. User can set a histogram trigger on the event which they want to monitor and poll() on its `hist` file. Since this poll() returns POLLIN, the next poll() will return soon unless a read() happens on that hist file. NOTE: To read the hist file again, you must set the file offset to 0, but just for monitoring the event, you may not need to read the histogram. Cc: Shuah Khan Cc: Mathieu Desnoyers Link: https://lore.kernel.org/173527247756.464571.14236296701625509931.stgit@devnote2 Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Tom Zanussi Signed-off-by: Steven Rostedt (Google)

tracing: Have process_string() also allow arrays

2024-12-31T05:10:32Z

In order to catch a common bug where a TRACE_EVENT() TP_fast_assign() assigns an address of an allocated string to the ring buffer and then references it in TP_printk(), which can be executed hours later when the string is free, the function test_event_printk() runs on all events as they are registered to make sure there's no unwanted dereferencing. It calls process_string() to handle cases in TP_printk() format that has "%s". It returns whether or not the string is safe. But it can have some false positives. For instance, xe_bo_move() has: TP_printk("move_lacks_source:%s, migrate object %p [size %zu] from %s to %s device_id:%s", __entry->move_lacks_source ? "yes" : "no", __entry->bo, __entry->size, xe_mem_type_to_name[__entry->old_placement], xe_mem_type_to_name[__entry->new_placement], __get_str(device_id)) Where the "%s" references into xe_mem_type_to_name[]. This is an array of pointers that should be safe for the event to access. Instead of flagging this as a bad reference, if a reference points to an array, where the record field is the index, consider it safe. Link: https://lore.kernel.org/all/9dee19b6185d325d0e6fa5f7cbba81d007d99166.camel@sapience.com/ Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20241231000646.324fb5f7@gandalf.local.home Fixes: 65a25d9f7ac02 ("tracing: Add "%s" check in test_event_printk()") Reported-by: Genes Lists Tested-by: Gene C Signed-off-by: Steven Rostedt (Google)