linux-stable.git/kernel/trace/trace_events_synth.c, branch v6.14.2

tracing: Do not use PERF enums when perf is not defined

2025-04-10T12:44:48+00:00

commit 8eb1518642738c6892bd629b46043513a3bf1a6a upstream.

An update was made to up the module ref count when a synthetic event is
registered for both trace and perf events. But if perf is not configured
in, the perf enums used will cause the kernel to fail to build.

Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Cc: Douglas Raillard 
Link: https://lore.kernel.org/20250323152151.528b5ced@batman.local.home
Fixes: 21581dd4e7ff ("tracing: Ensure module defining synth event cannot be unloaded while tracing")
Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202503232230.TeREVy8R-lkp@intel.com/
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

tracing: Fix synth event printk format for str fields

2025-04-10T12:44:47+00:00

commit 4d38328eb442dc06aec4350fd9594ffa6488af02 upstream.

The printk format for synth event uses "%.*s" to print string fields,
but then only passes the pointer part as var arg.

Replace %.*s with %s as the C string is guaranteed to be null-terminated.

The output in print fmt should never have been updated as __get_str()
handles the string limit because it can access the length of the string in
the string meta data that is saved in the ring buffer.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Fixes: 8db4d6bfbbf92 ("tracing: Change synthetic event string format to limit printed length")
Link: https://lore.kernel.org/20250325165202.541088-1-douglas.raillard@arm.com
Signed-off-by: Douglas Raillard 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

tracing: Ensure module defining synth event cannot be unloaded while tracing

2025-04-10T12:44:46+00:00

commit 21581dd4e7ff6c07d0ab577e3c32b13a74b31522 upstream.

Currently, using synth_event_delete() will fail if the event is being
used (tracing in progress), but that is normally done in the module exit
function. At that stage, failing is problematic as returning a non-zero
status means the module will become locked (impossible to unload or
reload again).

Instead, ensure the module exit function does not get called in the
first place by increasing the module refcnt when the event is enabled.

Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers 
Fixes: 35ca5207c2d11 ("tracing: Add synthetic event command generation functions")
Link: https://lore.kernel.org/20250318180906.226841-1-douglas.raillard@arm.com
Signed-off-by: Douglas Raillard 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

tracing: Switch trace_events_synth.c code over to use guard()

2024-12-26T15:38:37+00:00

There are a couple functions in trace_events_synth.c that have "goto out"
or equivalent on error in order to release locks that were taken. This can
be error prone or just simply make the code more complex.

Switch every location that ends with unlocking a mutex on error over to
using the guard(mutex)() infrastructure to let the compiler worry about
releasing locks. This makes the code easier to read and understand.

Cc: Masami Hiramatsu 
Cc: Mark Rutland 
Cc: Mathieu Desnoyers 
Cc: Andrew Morton 
Cc: Peter Zijlstra 
Link: https://lore.kernel.org/20241219201346.371082515@goodmis.org
Signed-off-by: Steven Rostedt (Google)

tracing/synthetic: Fix trace_string() return value

2024-02-15T16:40:01+00:00

Fix trace_string() by assigning the string length to the return variable
which got lost in commit ddeea494a16f ("tracing/synthetic: Use union
instead of casts") and caused trace_string() to always return 0.

Link: https://lore.kernel.org/linux-trace-kernel/20240214220555.711598-1-thorsten.blum@toblux.com

Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers 
Fixes: ddeea494a16f ("tracing/synthetic: Use union instead of casts")
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Thorsten Blum 
Signed-off-by: Steven Rostedt (Google)

tracing/synthetic: fix kernel-doc warnings

2023-12-20T17:51:03+00:00

scripts/kernel-doc warns about using @args: for variadic arguments to
functions. Documentation/doc-guide/kernel-doc.rst says that this should
be written as @...: instead, so update the source code to match that,
preventing the warnings.

trace_events_synth.c:1165: warning: Excess function parameter 'args' description in '__synth_event_gen_cmd_start'
trace_events_synth.c:1714: warning: Excess function parameter 'args' description in 'synth_event_trace'

Link: https://lore.kernel.org/linux-trace-kernel/20231220061226.30962-1-rdunlap@infradead.org

Cc: Mathieu Desnoyers 
Fixes: 35ca5207c2d11 ("tracing: Add synthetic event command generation functions")
Fixes: 8dcc53ad956d2 ("tracing: Add synth_event_trace() and related functions")
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Randy Dunlap 
Signed-off-by: Steven Rostedt (Google)

tracing: Have the user copy of synthetic event address use correct context

2023-11-02T03:46:05+00:00

A synthetic event is created by the synthetic event interface that can
read both user or kernel address memory. In reality, it reads any
arbitrary memory location from within the kernel. If the address space is
in USER (where CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE is set) then
it uses strncpy_from_user_nofault() to copy strings otherwise it uses
strncpy_from_kernel_nofault().

But since both functions use the same variable there's no annotation to
what that variable is (ie. __user). This makes sparse complain.

Quiet sparse by typecasting the strncpy_from_user_nofault() variable to
a __user pointer.

Link: https://lore.kernel.org/linux-trace-kernel/20231031151033.73c42e23@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Mark Rutland 
Fixes: 0934ae9977c2 ("tracing: Fix reading strings from synthetic events");
Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202311010013.fm8WTxa5-lkp@intel.com/
Signed-off-by: Steven Rostedt (Google)

tracing/synthetic: Print out u64 values properly

2023-09-11T22:23:10+00:00

The synth traces incorrectly print pointer to the synthetic event values
instead of the actual value when using u64 type. Fix by addressing the
contents of the union properly.

Link: https://lore.kernel.org/linux-trace-kernel/20230911141704.3585965-1-tero.kristo@linux.intel.com

Fixes: ddeea494a16f ("tracing/synthetic: Use union instead of casts")
Cc: stable@vger.kernel.org
Signed-off-by: Tero Kristo 
Signed-off-by: Steven Rostedt (Google)

tracing/synthetic: Allocate one additional element for size

2023-08-16T20:37:07+00:00

While debugging another issue I noticed that the stack trace contains one
invalid entry at the end:

-0       [008] d..4.    26.484201: wake_lat: pid=0 delta=2629976084 000000009cc24024 stack=STACK:
=> __schedule+0xac6/0x1a98
=> schedule+0x126/0x2c0
=> schedule_timeout+0x150/0x2c0
=> kcompactd+0x9ca/0xc20
=> kthread+0x2f6/0x3d8
=> __ret_from_fork+0x8a/0xe8
=> 0x6b6b6b6b6b6b6b6b

This is because the code failed to add the one element containing the
number of entries to field_size.

Link: https://lkml.kernel.org/r/20230816154928.4171614-4-svens@linux.ibm.com

Cc: Masami Hiramatsu 
Fixes: 00cf3d672a9d ("tracing: Allow synthetic events to pass around stacktraces")
Signed-off-by: Sven Schnelle 
Signed-off-by: Steven Rostedt (Google)

tracing/synthetic: Skip first entry for stack traces

2023-08-16T20:34:25+00:00

While debugging another issue I noticed that the stack trace output
contains the number of entries on top:

         -0       [000] d..4.   203.322502: wake_lat: pid=0 delta=2268270616 stack=STACK:
=> 0x10
=> __schedule+0xac6/0x1a98
=> schedule+0x126/0x2c0
=> schedule_timeout+0x242/0x2c0
=> __wait_for_common+0x434/0x680
=> __wait_rcu_gp+0x198/0x3e0
=> synchronize_rcu+0x112/0x138
=> ring_buffer_reset_online_cpus+0x140/0x2e0
=> tracing_reset_online_cpus+0x15c/0x1d0
=> tracing_set_clock+0x180/0x1d8
=> hist_register_trigger+0x486/0x670
=> event_hist_trigger_parse+0x494/0x1318
=> trigger_process_regex+0x1d4/0x258
=> event_trigger_write+0xb4/0x170
=> vfs_write+0x210/0xad0
=> ksys_write+0x122/0x208

Fix this by skipping the first element. Also replace the pointer
logic with an index variable which is easier to read.

Link: https://lkml.kernel.org/r/20230816154928.4171614-3-svens@linux.ibm.com

Cc: Masami Hiramatsu 
Fixes: 00cf3d672a9d ("tracing: Allow synthetic events to pass around stacktraces")
Signed-off-by: Sven Schnelle 
Signed-off-by: Steven Rostedt (Google)