* [PATCH] tracing: Use flexible array for entry fetch code
@ 2026-05-20 21:58 Rosen Penev
2026-05-21 3:09 ` Masami Hiramatsu
0 siblings, 1 reply; 2+ messages in thread
From: Rosen Penev @ 2026-05-20 21:58 UTC (permalink / raw)
To: linux-trace-kernel
Cc: Steven Rostedt, Masami Hiramatsu, Mathieu Desnoyers, Kees Cook,
Gustavo A. R. Silva, open list:TRACING,
open list:KERNEL HARDENING (not covered by other areas):Keyword:b__counted_by(_le|_be|_ptr)?b
Store probe entry fetch instructions in the probe_entry_arg
allocation instead of allocating a separate instruction array.
This keeps the entry fetch code tied to the entry argument lifetime while
leaving regular probe_arg instruction arrays separately allocated and
freed.
Assisted-by: Codex:GPT-5.5
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
kernel/trace/trace_probe.c | 8 +-------
kernel/trace/trace_probe.h | 2 +-
2 files changed, 2 insertions(+), 8 deletions(-)
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index e0d3a0da26af..39f040c863e8 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -838,15 +838,10 @@ static int __store_entry_arg(struct trace_probe *tp, int argnum)
int i, offset, last_offset = 0;
if (!earg) {
- earg = kzalloc_obj(*tp->entry_arg);
+ earg = kzalloc_flex(*earg, code, 2 * tp->nr_args + 1);
if (!earg)
return -ENOMEM;
earg->size = 2 * tp->nr_args + 1;
- earg->code = kzalloc_objs(struct fetch_insn, earg->size);
- if (!earg->code) {
- kfree(earg);
- return -ENOMEM;
- }
/* Fill the code buffer with 'end' to simplify it */
for (i = 0; i < earg->size; i++)
earg->code[i].op = FETCH_OP_END;
@@ -2051,7 +2046,6 @@ void trace_probe_cleanup(struct trace_probe *tp)
traceprobe_free_probe_arg(&tp->args[i]);
if (tp->entry_arg) {
- kfree(tp->entry_arg->code);
kfree(tp->entry_arg);
tp->entry_arg = NULL;
}
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 262d8707a3df..1076f1df347b 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -238,8 +238,8 @@ struct probe_arg {
};
struct probe_entry_arg {
- struct fetch_insn *code;
unsigned int size; /* The entry data size */
+ struct fetch_insn code[] __counted_by(size);
};
struct trace_uprobe_filter {
--
2.54.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] tracing: Use flexible array for entry fetch code
2026-05-20 21:58 [PATCH] tracing: Use flexible array for entry fetch code Rosen Penev
@ 2026-05-21 3:09 ` Masami Hiramatsu
0 siblings, 0 replies; 2+ messages in thread
From: Masami Hiramatsu @ 2026-05-21 3:09 UTC (permalink / raw)
To: Rosen Penev
Cc: linux-trace-kernel, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Kees Cook, Gustavo A. R. Silva,
open list:TRACING,
open list:KERNEL HARDENING (not covered by other areas):Keyword:b__counted_by(_le|_be|_ptr)?b
On Wed, 20 May 2026 14:58:17 -0700
Rosen Penev <rosenp@gmail.com> wrote:
> Store probe entry fetch instructions in the probe_entry_arg
> allocation instead of allocating a separate instruction array.
>
> This keeps the entry fetch code tied to the entry argument lifetime while
> leaving regular probe_arg instruction arrays separately allocated and
> freed.
>
Thanks, this looks good to me.
> Assisted-by: Codex:GPT-5.5
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
> kernel/trace/trace_probe.c | 8 +-------
> kernel/trace/trace_probe.h | 2 +-
> 2 files changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index e0d3a0da26af..39f040c863e8 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -838,15 +838,10 @@ static int __store_entry_arg(struct trace_probe *tp, int argnum)
> int i, offset, last_offset = 0;
>
> if (!earg) {
> - earg = kzalloc_obj(*tp->entry_arg);
> + earg = kzalloc_flex(*earg, code, 2 * tp->nr_args + 1);
> if (!earg)
> return -ENOMEM;
> earg->size = 2 * tp->nr_args + 1;
> - earg->code = kzalloc_objs(struct fetch_insn, earg->size);
> - if (!earg->code) {
> - kfree(earg);
> - return -ENOMEM;
> - }
> /* Fill the code buffer with 'end' to simplify it */
> for (i = 0; i < earg->size; i++)
> earg->code[i].op = FETCH_OP_END;
> @@ -2051,7 +2046,6 @@ void trace_probe_cleanup(struct trace_probe *tp)
> traceprobe_free_probe_arg(&tp->args[i]);
>
> if (tp->entry_arg) {
> - kfree(tp->entry_arg->code);
> kfree(tp->entry_arg);
> tp->entry_arg = NULL;
> }
> diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
> index 262d8707a3df..1076f1df347b 100644
> --- a/kernel/trace/trace_probe.h
> +++ b/kernel/trace/trace_probe.h
> @@ -238,8 +238,8 @@ struct probe_arg {
> };
>
> struct probe_entry_arg {
> - struct fetch_insn *code;
> unsigned int size; /* The entry data size */
> + struct fetch_insn code[] __counted_by(size);
> };
>
> struct trace_uprobe_filter {
> --
> 2.54.0
>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
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