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

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Message-ID: <1432456091-73384-14-git-send-email-hekuang@huawei.com>
Date:	Sun, 24 May 2015 08:28:09 +0000
From:	He Kuang <hekuang@...wei.com>
To:	<wangnan0@...wei.com>, <paulus@...ba.org>,
	<a.p.zijlstra@...llo.nl>, <mingo@...hat.com>, <acme@...nel.org>,
	<namhyung@...nel.org>, <jolsa@...nel.org>, <ast@...mgrid.com>,
	<masami.hiramatsu.pt@...achi.com>, <dsahern@...il.com>,
	<brendan.d.gregg@...il.com>, <daniel@...earbox.net>
CC:	<lizefan@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH v2 13/15] perf bpf: Combine bpf prologue and bpf prog

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@...wei.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

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