linux-stable.git/kernel/tracepoint.c, branch v6.18.32

tracepoint: balance regfunc() on func_add() failure in tracepoint_add_func()

2026-05-14T13:30:11+00:00

commit fad217e16fded7f3c09f8637b0f6a224d58b5f2e upstream.

When a tracepoint goes through the 0 -> 1 transition, tracepoint_add_func()
invokes the subsystem's ext->regfunc() before attempting to install the
new probe via func_add(). If func_add() then fails (for example, when
allocate_probes() cannot allocate a new probe array under memory pressure
and returns -ENOMEM), the function returns the error without calling the
matching ext->unregfunc(), leaving the side effects of regfunc() behind
with no installed probe to justify them.

For syscall tracepoints this is particularly unpleasant: syscall_regfunc()
bumps sys_tracepoint_refcount and sets SYSCALL_TRACEPOINT on every task.
After a leaked failure, the refcount is stuck at a non-zero value with no
consumer, and every task continues paying the syscall trace entry/exit
overhead until reboot. Other subsystems providing regfunc()/unregfunc()
pairs exhibit similarly scoped persistent state.

Mirror the existing 1 -> 0 cleanup and call ext->unregfunc() in the
func_add() error path, gated on the same condition used there so the
unwind is symmetric with the registration.

Fixes: 8cf868affdc4 ("tracing: Have the reg function allow to fail")
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Link: https://patch.msgid.link/20260413190601.21993-1-devnexen@gmail.com
Signed-off-by: David Carlier 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

tracepoint: Print the function symbol when tracepoint_debug is set

2025-03-21T19:30:10+00:00

When tracepoint_debug is set, we may get the output in kernel log:
     [  380.013843] Probe 0 : 00000000f0d68cda

It is not readable, so change to print the function symbol.
After this patch, the output may becomes:
     [   55.225555] Probe 0 : perf_trace_sched_wakeup_template+0x0/0x20

Link: https://lore.kernel.org/20250307033858.4134-1-shijie@os.amperecomputing.com
Signed-off-by: Huang Shijie 
Signed-off-by: Steven Rostedt (Google)

tracing: Fix syscall tracepoint use-after-free

2024-11-01T18:37:31+00:00

The grace period used internally within tracepoint.c:release_probes()
uses call_rcu() to batch waiting for quiescence of old probe arrays,
rather than using the tracepoint_synchronize_unregister() which blocks
while waiting for quiescence.

With the introduction of faultable syscall tracepoints, this causes
use-after-free issues reproduced with syzkaller.

Fix this by using the appropriate call_rcu() or call_rcu_tasks_trace()
before invoking the rcu_free_old_probes callback. This can be chosen
using the tracepoint_is_faultable() API.

A similar issue exists in bpf use of call_rcu(). Fixing this is left to
a separate change.

Reported-by: syzbot+b390c8062d8387b6272a@syzkaller.appspotmail.com
Fixes: a363d27cdbc2 ("tracing: Allow system call tracepoints to handle page faults")
Tested-by: Jordan Rife 
Cc: Michael Jeanson 
Cc: Thomas Gleixner 
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 
Cc: Jordan Rife 
Cc: linux-trace-kernel@vger.kernel.org
Link: https://lore.kernel.org/20241031152056.744137-4-mathieu.desnoyers@efficios.com
Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Steven Rostedt (Google)

tracing: Introduce tracepoint extended structure

2024-11-01T18:37:31+00:00

Shrink the struct tracepoint size from 80 bytes to 72 bytes on x86-64 by
moving the (typically NULL) regfunc/unregfunc pointers to an extended
structure.

Tested-by: Jordan Rife 
Cc: Michael Jeanson 
Cc: Thomas Gleixner 
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 
Cc: Jordan Rife 
Cc: linux-trace-kernel@vger.kernel.org
Link: https://lore.kernel.org/20241031152056.744137-2-mathieu.desnoyers@efficios.com
Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Steven Rostedt (Google)

tracepoint: Remove SRCU protection

2024-10-09T01:17:39+00:00

With the removal of the trace_*_rcuidle() tracepoints, there is no reason
to protect tracepoints with SRCU. The reason the SRCU protection was
added, was because it can protect tracepoints when RCU is not "watching".
Now that tracepoints are only used when RCU is watching, remove the SRCU
protection. It just made things more complex and confusing anyway.

Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Cc: Joel Fernandes 
Link: https://lore.kernel.org/20241003184220.0dc21d35@gandalf.local.home
Acked-by: Peter Zijlstra (Intel) 
Signed-off-by: Steven Rostedt (Google)

tracepoints: Use new static branch API

2024-10-09T01:17:39+00:00

The old static key API is deprecated.  Switch to the new one.

Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Cc: Alice Ryhl 
Link: https://lore.kernel.org/7a08dae3c5eddb14b13864923c1b58ac1f4af83c.1728414936.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf 
Signed-off-by: Steven Rostedt (Google)

tracepoint: Support iterating tracepoints in a loading module

2024-09-25T14:23:44+00:00

Add for_each_tracepoint_in_module() function to iterate tracepoints in
a module. This API is needed for handling tracepoints in a loading
module from tracepoint_module_notifier callback function.
This also update for_each_module_tracepoint() to pass the module to
callback function so that it can find module easily.

Link: https://lore.kernel.org/all/172397778740.286558.15781131277732977643.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google)

tracepoint: Support iterating over tracepoints on modules

2024-09-25T14:23:44+00:00

Add for_each_module_tracepoint() for iterating over tracepoints
on modules. This is similar to the for_each_kernel_tracepoint()
but only for the tracepoints on modules (not including kernel
built-in tracepoints).

Link: https://lore.kernel.org/all/172397777800.286558.14554748203446214056.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google)

tracepoint: Allow livepatch module add trace event

2023-02-18T19:34:36+00:00

In the case of keeping the system running, the preferred method for
tracing the kernel is dynamic tracing (kprobe), but the drawback of
this method is that events are lost, especially when tracing packages
in the network stack.

Livepatching provides a potential solution, which is to reimplement the
function you want to replace and insert a static tracepoint.
In such a way, custom stable static tracepoints can be expanded without
rebooting the system.

Link: https://lkml.kernel.org/r/20221102160236.11696-1-iecedge@gmail.com

Signed-off-by: Jianlin Lv 
Signed-off-by: Steven Rostedt (Google)

tracepoint: Optimize the critical region of mutex_lock in tracepoint_module_coming()

2022-09-26T17:01:18+00:00

The memory allocation of 'tp_mod' does not require mutex_lock()
protection, move it out.

Link: https://lkml.kernel.org/r/20220914061416.1630-1-thunder.leizhen@huawei.com

Signed-off-by: Zhen Lei 
Signed-off-by: Steven Rostedt (Google)