[RFC PATCH v2 13/15] perf bpf: Combine bpf prologue and bpf prog

[He Kuang <hekuang@huawei.com>]

Combine bpf prologue before attaching bpf progs to perf probe event. If
prologue is generated, it will be pasted in front of the original bpf
prog.

Signed-off-by: He Kuang <hekuang@huawei.com>
---
 tools/lib/bpf/libbpf.c       | 27 +++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h       |  2 ++
 tools/perf/util/bpf-loader.c | 27 +++++++++++++++++++++++++++
 3 files changed, 56 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 89c725a..c0b792f 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1087,3 +1087,30 @@ int bpf_prog_get_fd(struct bpf_prog_handler *handler, int *pfd)
 	*pfd = prog->fd;
 	return 0;
 }
+
+int bpf_obj_prologue(struct bpf_prog_handler *handler, char *result, int size)
+{
+	struct bpf_program *prog;
+	int new_count;
+	int count = size / sizeof(struct bpf_insn);
+
+	prog = handler_to_prog(handler);
+	if (!prog)
+		return -EINVAL;
+
+	new_count = prog->insns_cnt + count;
+	result = realloc(result,
+			new_count * sizeof(struct bpf_insn));
+	if (!result)
+		return -ENOMEM;
+
+	memcpy(result + count * sizeof(struct bpf_insn),
+		prog->insns,
+		prog->insns_cnt * sizeof(struct bpf_insn));
+
+	free(prog->insns);
+	prog->insns = (struct bpf_insn *)result;
+	prog->insns_cnt = new_count;
+
+	return 0;
+}
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 9d6d4f7..7df58fd 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -53,6 +53,8 @@ int bpf_prog_get_title(struct bpf_prog_handler *handler,
 
 int bpf_prog_get_fd(struct bpf_prog_handler *handler, int *pfd);
 
+int bpf_obj_prologue(struct bpf_prog_handler *handler, char *result, int count);
+
 /*
  * packed attribute is unnecessary for 'bpf_map_def'.
  */
diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index b793c69..3f93d04 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -168,6 +168,31 @@ void bpf_clear(void)
 		bpf_close_object(params.objects[i]);
 }
 
+static int bpf_prologue(void)
+{
+	int i, ret;
+
+	for (i = 0; i < (int)params.nr_progs; i++) {
+		struct bpf_prog_handler *prog =
+			params.progs[i].prog;
+		struct perf_probe_event *pevent =
+			params.progs[i].pevent;
+		int count;
+		char *result;
+
+		ret = get_bpf_prologue(pevent, &result, &count);
+		if (ret)
+			return ret;
+
+		if (count > 0)
+			ret = bpf_obj_prologue(prog, result, count);
+		else
+			pr_debug("bpf: no prologue generated\n");
+	}
+
+	return ret;
+}
+
 static bool is_probing = false;
 
 int bpf_unprobe(void)
@@ -220,6 +245,8 @@ int bpf_load(void)
 	size_t i;
 	int err;
 
+	bpf_prologue();
+
 	for (i = 0; i < params.nr_objects; i++) {
 		err = bpf_load_object(params.objects[i]);
 		if (err) {
-- 
1.8.5.2