[PATCH] tracing: Use flexible array for entry fetch code

[PATCH] tracing: Use flexible array for entry fetch code

[Rosen Penev]

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