kernel/linux.git/include/trace/trace_events.h, branch v7.0-rc7

tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast

2026-01-30T15:44:11+00:00

The current use of guard(preempt_notrace)() within __DECLARE_TRACE() to protect invocation of __DO_TRACE_CALL() means that BPF programs attached to tracepoints are non-preemptible. This is unhelpful in real-time systems, whose users apparently wish to use BPF while also achieving low latencies. (Who knew?) One option would be to use preemptible RCU, but this introduces many opportunities for infinite recursion, which many consider to be counterproductive, especially given the relatively small stacks provided by the Linux kernel. These opportunities could be shut down by sufficiently energetic duplication of code, but this sort of thing is considered impolite in some circles. Therefore, use the shiny new SRCU-fast API, which provides somewhat faster readers than those of preemptible RCU, at least on Paul E. McKenney's laptop, where task_struct access is more expensive than access to per-CPU variables. And SRCU-fast provides way faster readers than does SRCU, courtesy of being able to avoid the read-side use of smp_mb(). Also, it is quite straightforward to create srcu_read_{,un}lock_fast_notrace() functions. Link: https://lore.kernel.org/all/20250613152218.1924093-1-bigeasy@linutronix.de/ Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Cc: Sebastian Andrzej Siewior Cc: Alexei Starovoitov Link: https://patch.msgid.link/20260126231256.499701982@kernel.org Co-developed-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Signed-off-by: Steven Rostedt (Google)

tracing/ftrace: Add might_fault check to syscall probes

2024-10-09T21:09:36+00:00

Add a might_fault() check to validate that the ftrace sys_enter/sys_exit probe callbacks are indeed called from a context where page faults can be handled. Cc: Michael Jeanson Cc: Masami Hiramatsu Cc: Peter Zijlstra Cc: Alexei Starovoitov Cc: Yonghong Song Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Mark Rutland Cc: Alexander Shishkin Cc: Namhyung Kim Cc: Andrii Nakryiko Cc: bpf@vger.kernel.org Cc: Joel Fernandes Link: https://lore.kernel.org/20241009010718.2050182-7-mathieu.desnoyers@efficios.com Acked-by: Masami Hiramatsu (Google) Signed-off-by: Mathieu Desnoyers Signed-off-by: Steven Rostedt (Google)

tracing/ftrace: disable preemption in syscall probe

2024-10-09T21:07:00+00:00

In preparation for allowing system call enter/exit instrumentation to handle page faults, make sure that ftrace can handle this change by explicitly disabling preemption within the ftrace system call tracepoint probes to respect the current expectations within ftrace ring buffer code. This change does not yet allow ftrace to take page faults per se within its probe, but allows its existing probes to adapt to the upcoming change. Cc: Michael Jeanson Cc: Masami Hiramatsu Cc: Peter Zijlstra Cc: Alexei Starovoitov Cc: Yonghong Song Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Mark Rutland Cc: Alexander Shishkin Cc: Namhyung Kim Cc: Andrii Nakryiko Cc: bpf@vger.kernel.org Cc: Joel Fernandes Link: https://lore.kernel.org/20241009010718.2050182-3-mathieu.desnoyers@efficios.com Acked-by: Masami Hiramatsu (Google) Signed-off-by: Mathieu Desnoyers Signed-off-by: Steven Rostedt (Google)

tracing: Declare system call tracepoints with TRACE_EVENT_SYSCALL

2024-10-09T21:05:54+00:00

In preparation for allowing system call tracepoints to handle page faults, introduce TRACE_EVENT_SYSCALL to declare the sys_enter/sys_exit tracepoints. Move the common code between __DECLARE_TRACE and __DECLARE_TRACE_SYSCALL into __DECLARE_TRACE_COMMON. This change is not meant to alter the generated code, and only prepares the following modifications. Cc: Michael Jeanson Cc: Masami Hiramatsu Cc: Peter Zijlstra Cc: Alexei Starovoitov Cc: Yonghong Song Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Mark Rutland Cc: Alexander Shishkin Cc: Namhyung Kim Cc: Andrii Nakryiko Cc: bpf@vger.kernel.org Cc: Joel Fernandes Link: https://lore.kernel.org/20241009010718.2050182-2-mathieu.desnoyers@efficios.com Signed-off-by: Mathieu Desnoyers Signed-off-by: Steven Rostedt (Google)

tracing: Rename the staging files for trace_events

2022-04-02T12:40:04+00:00

When looking for implementation of different phases of the creation of the TRACE_EVENT() macro, it is pretty useless when all helper macro redefinitions are in files labeled "stageX_defines.h". Rename them to state which phase the files are for. For instance, when looking for the defines that are used to create the event fields, seeing "stage4_event_fields.h" gives the developer a good idea that the defines are in that file. Signed-off-by: Steven Rostedt (Google)

tracing: Move the defines to create TRACE_EVENTS into their own files

2022-03-11T16:49:23+00:00

In an effort to add custom event macros that can be used to create your own custom events based on existing tracepoints, move the defines of the special macros used in TRACE_EVENT() into their own files such that they can be reused for TRACE_CUSTOM_EVENT(). Link: https://lkml.kernel.org/r/20220303220625.553406495@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/perf: Avoid -Warray-bounds warning for __rel_loc macro

2022-01-28T00:15:45+00:00

As done for trace_events.h, also fix the __rel_loc macro in perf.h, which silences the -Warray-bounds warning: In file included from ./include/linux/string.h:253, from ./include/linux/bitmap.h:11, from ./include/linux/cpumask.h:12, from ./include/linux/mm_types_task.h:14, from ./include/linux/mm_types.h:5, from ./include/linux/buildid.h:5, from ./include/linux/module.h:14, from samples/trace_events/trace-events-sample.c:2: In function '__fortify_strcpy', inlined from 'perf_trace_foo_rel_loc' at samples/trace_events/./trace-events-sample.h:519:1: ./include/linux/fortify-string.h:47:33: warning: '__builtin_strcpy' offset 12 is out of the bounds [ 0, 4] [-Warray-bounds] 47 | #define __underlying_strcpy __builtin_strcpy | ^ ./include/linux/fortify-string.h:445:24: note: in expansion of macro '__underlying_strcpy' 445 | return __underlying_strcpy(p, q); | ^~~~~~~~~~~~~~~~~~~ Also make __data struct member a proper flexible array to avoid future problems. Link: https://lkml.kernel.org/r/20220125220037.2738923-1-keescook@chromium.org Cc: Steven Rostedt Cc: Masami Hiramatsu Fixes: 55de2c0b5610c ("tracing: Add '__rel_loc' using trace event macros") Reported-by: Stephen Rothwell Signed-off-by: Kees Cook Signed-off-by: Steven Rostedt (Google)

tracing: Avoid -Warray-bounds warning for __rel_loc macro

2022-01-28T00:15:45+00:00

Since -Warray-bounds checks the destination size from the type of given pointer, __assign_rel_str() macro gets warned because it passes the pointer to the 'u32' field instead of 'trace_event_raw_*' data structure. Pass the data address calculated from the 'trace_event_raw_*' instead of 'u32' __rel_loc field. Link: https://lkml.kernel.org/r/20220125233154.dac280ed36944c0c2fe6f3ac@kernel.org Cc: Stephen Rothwell Cc: Kees Cook Signed-off-by: Masami Hiramatsu [ This did not fix the warning, but is still a nice clean up ] Signed-off-by: Steven Rostedt (Google)

tracing: Add '__rel_loc' using trace event macros

2021-12-06T20:37:21+00:00

Add '__rel_loc' using trace event macros. These macros are usually not used in the kernel, except for testing purpose. This also add "rel_" variant of macros for dynamic_array string, and bitmask. Link: https://lkml.kernel.org/r/163757342119.510314.816029622439099016.stgit@devnote2 Cc: Beau Belgrave Cc: Namhyung Kim Cc: Tom Zanussi Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware)

tracing: Add trace_event helper macros __string_len() and __assign_str_len()

2021-08-17T15:47:52+00:00

There's a few cases that a string that is to be recorded in a trace event, does not have a terminating 'nul' character, and instead, the tracepoint passes in the length of the string to record. Add two helper macros to the trace event code that lets this work easier, than tricks with "%.*s" logic. __string_len() which is similar to __string() for declaration, but takes a length argument. __assign_str_len() which is similar to __assign_str() for assiging the string, but it too takes a length argument. Note, the TRACE_EVENT() macro will allocate the location on the ring buffer to 'len + 1', that will be used to store the string into. It is a requirement that the 'len' used for this is a most the length of the string being recorded. This string can still use __get_str() just like strings created with __string() can use to retrieve the string. Link: https://lore.kernel.org/linux-nfs/20210513105018.7539996a@gandalf.local.home/ Tested-by: Chuck Lever Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Chuck Lever