linux.git/kernel/trace/trace_remote.c, branch v7.2-rc5

tracing: Propagate errors from remote event bulk updates

2026-07-23T16:30:07+00:00

remote_events_dir_enable_write() ignores the return value from
trace_remote_enable_event(). If a remote rejects an event state change,
the write therefore reports success even though the affected event remains
in its previous state.

Keep trying all events, but retain and return the first error. This matches
__ftrace_set_clr_event_nolock(), which permits partial updates while
notifying userspace when an operation fails.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260715074455.3897-1-liu.yun@linux.dev
Fixes: 775cb093bc50 ("tracing: Add events/ root files to trace remotes")
Assisted-by: Codex:gpt-5.6-sol
Signed-off-by: Jackie Liu 
Reviewed-by: Vincent Donnefort 
Signed-off-by: Steven Rostedt

tracing/remotes: Fix page_va[] access before counter update in trace_remote_alloc_buffer()

2026-07-22T20:53:29+00:00

page_va[] is annotated __counted_by(nr_page_va), so nr_page_va must
cover an index before that element is accessed. The allocation loop
writes page_va[id] while nr_page_va is still id and increments it only
afterwards, so every write is one element past the declared count.

The store is out of bounds with respect to the annotation: a build with
CONFIG_UBSAN_BOUNDS on a toolchain that honours __counted_by
(clang >= 20.1, gcc >= 15.1) flags it as an array-index overflow.

Increment nr_page_va before writing the element it now covers. A failed
allocation then leaves the slot counted but NULL; the error path frees
it with free_page(0), which is a no-op.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260713072823.2668323-1-fuad.tabba@linux.dev
Fixes: 96e43537af546 ("tracing: Introduce trace remotes")
Signed-off-by: Fuad Tabba 
Reviewed-by: Vincent Donnefort 
Tested-by: Vincent Donnefort 
Signed-off-by: Steven Rostedt

tracing/remotes: Fix struct_len in trace_remote_alloc_buffer()

2026-07-10T18:04:26+00:00

Pre-calculate desc->struct_len up-front in trace_remote_alloc_buffer()
with trace_buffer_desc_size() to fix double-counting.

While at it, use the accessor __first_ring_buffer_desc().

Link: https://patch.msgid.link/20260709160017.1729517-3-vdonnefort@google.com
Fixes: 96e43537af54 ("tracing: Introduce trace remotes")
Reported-by: Sashiko 
Signed-off-by: Vincent Donnefort 
Signed-off-by: Steven Rostedt

tracing/remotes: Fix leak in trace_remote_alloc_buffer() error path

2026-07-10T18:04:26+00:00

If page allocation fails in trace_remote_alloc_buffer(), desc->nr_cpus
is not yet incremented for the current CPU. As a consequence, on error,
half-allocated rb_desc will not be freed in trace_remote_free_buffer().

Increment desc->nr_cpus as soon as the first allocation for the current
CPU has succeeded.

Link: https://patch.msgid.link/20260709160017.1729517-2-vdonnefort@google.com
Fixes: 96e43537af54 ("tracing: Introduce trace remotes")
Reported-by: Sashiko 
Signed-off-by: Vincent Donnefort 
Signed-off-by: Steven Rostedt

tracing: Remove redundant IS_ERR() check in trace_pipe_open()

2026-05-21T22:03:06+00:00

in trace_pipe_open() already check the IS_ERR(iter) and return early on
error,so iter after will be valid and it is safe to return 0 at end.

Link: https://patch.msgid.link/20260420101236.223919-1-yashsuthar983@gmail.com
Signed-off-by: Yash Suthar 
Signed-off-by: Steven Rostedt

tracing: Non-consuming read for trace remotes with an offline CPU

2026-04-02T13:16:09+00:00

When a trace_buffer is created while a CPU is offline, this CPU is
cleared from the trace_buffer CPU mask, preventing the creation of a
non-consuming iterator (ring_buffer_iter). For trace remotes, it means
the iterator fails to be allocated (-ENOMEM) even though there are
available ring buffers in the trace_buffer.

For non-consuming reads of trace remotes, skip missing ring_buffer_iter
to allow reading the available ring buffers.

Acked-by: Steven Rostedt (Google) 
Signed-off-by: Vincent Donnefort 
Link: https://patch.msgid.link/20260401045100.3394299-2-vdonnefort@google.com
Signed-off-by: Marc Zyngier

tracing: Add events/ root files to trace remotes

2026-03-09T16:33:54+00:00

Just like for the kernel events directory, add 'enable', 'header_page'
and 'header_event' at the root of the trace remote events/ directory.

Link: https://patch.msgid.link/20260309162516.2623589-11-vdonnefort@google.com
Reviewed-by: Steven Rostedt (Google) 
Signed-off-by: Vincent Donnefort 
Signed-off-by: Steven Rostedt (Google)

tracing: Add events to trace remotes

2026-03-09T16:33:54+00:00

An event is predefined point in the writer code that allows to log
data. Following the same scheme as kernel events, add remote events,
described to user-space within the events/ tracefs directory found in
the corresponding trace remote.

Remote events are expected to be described during the trace remote
registration.

Add also a .enable_event callback for trace_remote to toggle the event
logging, if supported.

Link: https://patch.msgid.link/20260309162516.2623589-10-vdonnefort@google.com
Reviewed-by: Steven Rostedt (Google) 
Signed-off-by: Vincent Donnefort 
Signed-off-by: Steven Rostedt (Google)

tracing: Add init callback to trace remotes

2026-03-09T16:33:54+00:00

Add a .init call back so the trace remote callers can add entries to the
tracefs directory.

Link: https://patch.msgid.link/20260309162516.2623589-9-vdonnefort@google.com
Reviewed-by: Steven Rostedt (Google) 
Signed-off-by: Vincent Donnefort 
Signed-off-by: Steven Rostedt (Google)

tracing: Add non-consuming read to trace remotes

2026-03-09T16:33:54+00:00

Allow reading the trace file for trace remotes. This performs a
non-consuming read of the trace buffer.

Link: https://patch.msgid.link/20260309162516.2623589-8-vdonnefort@google.com
Reviewed-by: Steven Rostedt (Google) 
Signed-off-by: Vincent Donnefort 
Signed-off-by: Steven Rostedt (Google)