selftests/bpf: Add stacktrace map lookup_and_delete_elem test case

Add tests for stacktrace map lookup and delete:
1. use bpf_map_lookup_and_delete_elem to lookup and delete the target
   stack_id,
2. lookup the deleted stack_id again to double check.

Signed-off-by: Tao Chen <chen.dylane@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250925175030.1615837-3-chen.dylane@linux.dev

Author: Tao Chen

tools/testing/selftests/bpf/prog_tests/stacktrace_map.c

@@ -7,7 +7,8 @@ void test_stacktrace_map(void)
 	struct stacktrace_map *skel;
 	int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
 	int err, stack_trace_len;
-	__u32 key, val, duration = 0;
+	__u32 key, val, stack_id, duration = 0;
+	__u64 stack[PERF_MAX_STACK_DEPTH];
 
 	skel = stacktrace_map__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
@@ -48,6 +49,14 @@ void test_stacktrace_map(void)
 		  "err %d errno %d\n", err, errno))
 		goto out;
 
+	stack_id = skel->bss->stack_id;
+	err = bpf_map_lookup_and_delete_elem(stackmap_fd, &stack_id,  stack);
+	if (!ASSERT_OK(err, "lookup and delete target stack_id"))
+		goto out;
+
+	err = bpf_map_lookup_elem(stackmap_fd, &stack_id, stack);
+	if (!ASSERT_EQ(err, -ENOENT, "lookup deleted stack_id"))
+		goto out;
 out:
 	stacktrace_map__destroy(skel);
 }

tools/testing/selftests/bpf/progs/stacktrace_map.c

@@ -50,6 +50,7 @@ struct sched_switch_args {
 	int next_prio;
 };
 
+__u32 stack_id;
 SEC("tracepoint/sched/sched_switch")
 int oncpu(struct sched_switch_args *ctx)
 {
@@ -64,6 +65,7 @@ int oncpu(struct sched_switch_args *ctx)
 	/* The size of stackmap and stackid_hmap should be the same */
 	key = bpf_get_stackid(ctx, &stackmap, 0);
 	if ((int)key >= 0) {
+		stack_id = key;
 		bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
 		stack_p = bpf_map_lookup_elem(&stack_amap, &key);
 		if (stack_p)