kernel/linux.git/include/linux/trace_events.h, branch v6.19.11

tracing: Wake up poll waiters for hist files when removing an event

2026-03-04T12:21:46+00:00

[ Upstream commit 9678e53179aa7e907360f5b5b275769008a69b80 ] The event_hist_poll() function attempts to verify whether an event file is being removed, but this check may not occur or could be unnecessarily delayed. This happens because hist_poll_wakeup() is currently invoked only from event_hist_trigger() when a hist command is triggered. If the event file is being removed, no associated hist command will be triggered and a waiter will be woken up only after an unrelated hist command is triggered. Fix the issue by adding a call to hist_poll_wakeup() in remove_event_file_dir() after setting the EVENT_FILE_FL_FREED flag. This ensures that a task polling on a hist file is woken up and receives EPOLLERR. Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers Cc: Tom Zanussi Acked-by: Masami Hiramatsu (Google) Link: https://patch.msgid.link/20260219162737.314231-3-petr.pavlu@suse.com Fixes: 1bd13edbbed6 ("tracing/hist: Add poll(POLLIN) support on hist file") Signed-off-by: Petr Pavlu Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin

tracing: Fix enabling of tracing on file release

2025-12-05T20:17:56+00:00

The trace file will pause tracing if the tracing instance has the "pause-on-trace" option is set. This happens when the file is opened, and it is unpaused when the file is closed. When this was first added, there was only one user that paused tracing. On open, the check to pause was: if (!iter->snapshot && (tr->trace_flags & TRACE_ITER(PAUSE_ON_TRACE))) Where if it is not the snapshot tracer and the "pause-on-trace" option is set, then it increments a "stop_count" of the trace instance. On close, the check is: if (!iter->snapshot && tr->stop_count) That is, if it is not the snapshot buffer and it was stopped, it will re-enable tracing. Now there's more places that stop tracing. This means, if something else stops tracing the tr->stop_count will be non-zero, and that means if the trace file is closed, it will decrement the stop_count even though it never incremented it. This causes a warning because when the user that stopped tracing enables it again, the stop_count goes below zero. Instead of relying on the stop_count being set to know if the close of the trace file should enable tracing again, add a new flag to the trace iterator. The trace iterator is unique per open of the trace file, and if the open stops tracing set the trace iterator PAUSE flag. On close, if the PAUSE flag is set, then re-enable it again. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://patch.msgid.link/20251202161751.24abaaf1@gandalf.local.home Fixes: 06e0a548bad0f ("tracing: Do not disable tracing when reading the trace file") Reported-by: syzbot+ccdec3bfe0beec58a38d@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/692f44a5.a70a0220.2ea503.00c8.GAE@google.com/ Signed-off-by: Steven Rostedt (Google)

tracing: Remove EVENT_FILE_FL_SOFT_MODE flag

2025-07-23T00:15:51+00:00

When soft disabling of trace events was first created, it needed to have a way to know if a file had a user that was using it with soft disabled (for triggers that need to enable or disable events from a context that can not really enable or disable the event, it would set SOFT_DISABLED to state it is disabled). The flag SOFT_MODE was used to denote that an event had a user that would enable or disable it via the SOFT_DISABLED flag. Commit 1cf4c0732db3c ("tracing: Modify soft-mode only if there's no other referrer") fixed a bug where if two users were using the SOFT_DISABLED flag the accounting would get messed up as the SOFT_MODE flag could only handle one user. That commit added the sm_ref counter which kept track of how many users were using the event in "soft mode". This made the SOFT_MODE flag redundant as it should only be set if the sm_ref counter is non zero. Remove the SOFT_MODE flag and just use the sm_ref counter to know the event is in soft mode or not. This makes the code a bit simpler. Link: https://lore.kernel.org/all/20250702111908.03759998@batman.local.home/ Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Gabriele Paoloni Link: https://lore.kernel.org/20250702143657.18dd1882@batman.local.home Signed-off-by: Steven Rostedt (Google)

tracing: Remove orphaned event_trace_printk

2025-03-06T18:35:26+00:00

The event_trace_printk macro has no callers since commit b8e65554d80b ("tracing: remove deprecated TRACE_FORMAT"). So drop it. Link: https://lore.kernel.org/20250213113951.813258-1-hengqi.chen@gmail.com Signed-off-by: Hengqi Chen 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

2025-01-24T01:51:16+00:00

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

2025-01-07T16:44:49+00:00

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: Constify string literal data member in struct trace_event_call

2024-12-24T02:53:43+00:00

The name member of the struct trace_event_call is assigned with generated string literals; declare them pointer to read-only. Reported by clang: security/landlock/syscalls.c:179:1: warning: initializing 'char *' with an expression of type 'const char[34]' discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers] 179 | SYSCALL_DEFINE3(landlock_create_ruleset, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 180 | const struct landlock_ruleset_attr __user *const, attr, | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 181 | const size_t, size, const __u32, flags) | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ./include/linux/syscalls.h:226:36: note: expanded from macro 'SYSCALL_DEFINE3' 226 | #define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name, __VA_ARGS__) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ./include/linux/syscalls.h:234:2: note: expanded from macro 'SYSCALL_DEFINEx' 234 | SYSCALL_METADATA(sname, x, __VA_ARGS__) \ | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ./include/linux/syscalls.h:184:2: note: expanded from macro 'SYSCALL_METADATA' 184 | SYSCALL_TRACE_ENTER_EVENT(sname); \ | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ./include/linux/syscalls.h:151:30: note: expanded from macro 'SYSCALL_TRACE_ENTER_EVENT' 151 | .name = "sys_enter"#sname, \ | ^~~~~~~~~~~~~~~~~ Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Mickaël Salaün Cc: Günther Noack Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Bill Wendling Cc: Justin Stitt Link: https://lore.kernel.org/20241125105028.42807-1-cgoettsche@seltendoof.de Fixes: b77e38aa240c3 ("tracing: add event trace infrastructure") Signed-off-by: Christian Göttsche Signed-off-by: Steven Rostedt (Google)

tracing: Check "%s" dereference via the field and not the TP_printk format

2024-12-17T16:40:11+00:00

The TP_printk() portion of a trace event is executed at the time a event is read from the trace. This can happen seconds, minutes, hours, days, months, years possibly later since the event was recorded. If the print format contains a dereference to a string via "%s", and that string was allocated, there's a chance that string could be freed before it is read by the trace file. To protect against such bugs, there are two functions that verify the event. The first one is test_event_printk(), which is called when the event is created. It reads the TP_printk() format as well as its arguments to make sure nothing may be dereferencing a pointer that was not copied into the ring buffer along with the event. If it is, it will trigger a WARN_ON(). For strings that use "%s", it is not so easy. The string may not reside in the ring buffer but may still be valid. Strings that are static and part of the kernel proper which will not be freed for the life of the running system, are safe to dereference. But to know if it is a pointer to a static string or to something on the heap can not be determined until the event is triggered. This brings us to the second function that tests for the bad dereferencing of strings, trace_check_vprintf(). It would walk through the printf format looking for "%s", and when it finds it, it would validate that the pointer is safe to read. If not, it would produces a WARN_ON() as well and write into the ring buffer "[UNSAFE-MEMORY]". The problem with this is how it used va_list to have vsnprintf() handle all the cases that it didn't need to check. Instead of re-implementing vsnprintf(), it would make a copy of the format up to the %s part, and call vsnprintf() with the current va_list ap variable, where the ap would then be ready to point at the string in question. For architectures that passed va_list by reference this was possible. For architectures that passed it by copy it was not. A test_can_verify() function was used to differentiate between the two, and if it wasn't possible, it would disable it. Even for architectures where this was feasible, it was a stretch to rely on such a method that is undocumented, and could cause issues later on with new optimizations of the compiler. Instead, the first function test_event_printk() was updated to look at "%s" as well. If the "%s" argument is a pointer outside the event in the ring buffer, it would find the field type of the event that is the problem and mark the structure with a new flag called "needs_test". The event itself will be marked by TRACE_EVENT_FL_TEST_STR to let it be known that this event has a field that needs to be verified before the event can be printed using the printf format. When the event fields are created from the field type structure, the fields would copy the field type's "needs_test" value. Finally, before being printed, a new function ignore_event() is called which will check if the event has the TEST_STR flag set (if not, it returns false). If the flag is set, it then iterates through the events fields looking for the ones that have the "needs_test" flag set. Then it uses the offset field from the field structure to find the pointer in the ring buffer event. It runs the tests to make sure that pointer is safe to print and if not, it triggers the WARN_ON() and also adds to the trace output that the event in question has an unsafe memory access. The ignore_event() makes the trace_check_vprintf() obsolete so it is removed. Link: https://lore.kernel.org/all/CAHk-=wh3uOnqnZPpR0PeLZZtyWbZLboZ7cHLCKRWsocvs9Y7hQ@mail.gmail.com/ Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Cc: Al Viro Cc: Linus Torvalds Link: https://lore.kernel.org/20241217024720.848621576@goodmis.org Fixes: 5013f454a352c ("tracing: Add check of trace event print fmts for dereferencing pointers") Signed-off-by: Steven Rostedt (Google)

tracing: Record task flag NEED_RESCHED_LAZY.

2024-11-22T22:49:39+00:00

The scheduler added NEED_RESCHED_LAZY scheduling. Record this state as part of trace flags and expose it in the need_resched field. Record and expose NEED_RESCHED_LAZY. [bigeasy: Commit description, documentation bits.] Cc: Peter Zijlstra Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20241122202849.7DfYpJR0@linutronix.de Reviewed-by: Ankur Arora Reviewed-by: Steven Rostedt (Google) Signed-off-by: Thomas Gleixner Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (Google)

tracing: Remove TRACE_FLAG_IRQS_NOSUPPORT

2024-11-01T18:37:30+00:00

It was possible to enable tracing with no IRQ tracing support. The tracing infrastructure would then record TRACE_FLAG_IRQS_NOSUPPORT as the only tracing flag and show an 'X' in the output. The last user of this feature was PPC32 which managed to implement it during PowerPC merge in 2009. Since then, it was unused and the PPC32 dependency was finally removed in commit 0ea5ee035133a ("tracing: Remove PPC32 wart from config TRACING_SUPPORT"). Since the PowerPC merge the code behind !CONFIG_TRACE_IRQFLAGS_SUPPORT with TRACING enabled can no longer be selected used and the 'X' is not displayed or recorded. Remove the CONFIG_TRACE_IRQFLAGS_SUPPORT from the tracing code. Remove TRACE_FLAG_IRQS_NOSUPPORT. Cc: Peter Zijlstra Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20241022110112.XJI8I9T2@linutronix.de Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (Google)