[RFC PATCH 6/6] perf bpf: Generate bpf prologue for arguments

[He Kuang]

Generate 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@xxxxxxxxxx>
---
 tools/perf/util/bpf-loader.c | 66 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index c646ca4..8c746ef 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -900,6 +900,69 @@ bpf_perf_prog_load(struct bpf_obj *obj, struct bpf_perf_prog *prog)
 	return 0;
 }
 
+#ifdef HAVE_DWARF_SUPPORT
+#if 0
+static void show_bpf_insn(char *buf, int len)
+{
+	int i, j;
+	char *ptr = buf;
+
+	for (i = 0; i < len; i++) {
+		pr_debug("[%03d] ", i);
+		for (j = 0; j < 8; j++)
+			pr_debug("0x%02x, ", (*ptr++) & 0xff);
+		pr_debug("\\\n");
+	}
+}
+#endif
+
+static int bpf_obj_prologue(struct bpf_obj *obj)
+{
+	struct bpf_perf_prog *prog;
+	int ret = -1;
+
+	list_for_each_entry(prog, &obj->progs_list, list) {
+		int count;
+		char *result;
+		int new_count;
+
+		if (!prog->pev)
+			continue;
+
+		ret = get_bpf_prologue(prog->pev, &result, &count);
+		if (ret)
+			return ret;
+
+		if (count > 0) {
+			bpf_dump_prog((struct bpf_insn *)result, count);
+
+			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;
+		} else {
+			pr_debug("bpf: no prologue generated\n");
+		}
+	}
+
+	return ret;
+}
+#else
+static int bpf_progs_prologue(struct bpf_obj *obj __maybe_unused)
+{
+	return 0;
+}
+#endif
+
 static int
 bpf_obj_load_progs(struct bpf_obj *obj)
 {
@@ -946,6 +1009,9 @@ int bpf__load(const char *path)
 		goto out;
 	if ((err = bpf_obj_relocate(obj)))
 		goto out;
+	err = bpf_obj_prologue(obj);
+	if (err)
+		goto out;
 	if ((err = bpf_obj_load_progs(obj)))
 		goto out;
 
-- 
1.8.5.2

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