[RFC PATCH 5/6] perf bpf: Process debuginfo for generating bpf prologue

[He Kuang <hekuang@huawei.com>]

Process debuginfo for bpf prologue, the process function is copied and
modified from debuginfo__find_trace_events(), but use a different
callback function for generating bpf prologue bytecode.

Signed-off-by: He Kuang <hekuang@huawei.com>
---
 tools/perf/util/probe-event.c  | 27 +++++++++++++
 tools/perf/util/probe-event.h  |  2 +
 tools/perf/util/probe-finder.c | 90 ++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/probe-finder.h |  4 ++
 4 files changed, 123 insertions(+)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index c307cd7..fbdda4d 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -906,6 +906,33 @@ out:
 	return ret;
 }
 
+int get_bpf_prologue(struct perf_probe_event *pev, char **result, int *count)
+{
+	int ret;
+	struct debuginfo *dinfo;
+	bool need_dwarf;
+
+	ret = init_symbol_maps(false);
+	if (ret < 0)
+		return ret;
+
+	need_dwarf = perf_probe_event_need_dwarf(pev);
+
+	dinfo = open_debuginfo(NULL, !need_dwarf);
+
+	if (!dinfo) {
+		if (need_dwarf)
+			return -ENOENT;
+		pr_debug("Could not open debuginfo. Try to use symbols.\n");
+		return 0;
+	}
+
+	pr_debug("Try to generate bpf prologue from debuginfo.\n");
+
+	ret = debuginfo__find_bpf_prologue(dinfo, pev, result, count);
+
+	return ret;
+}
 #else	/* !HAVE_DWARF_SUPPORT */
 
 static int
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index 3b6c284..5a6b86e 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -115,6 +115,8 @@ extern int synthesize_probe_trace_arg_bpf(struct probe_trace_arg *arg,
 extern int synthesize_probe_trace_arg_bpf_begin(struct strbuf *buf);
 extern int synthesize_probe_trace_arg_bpf_end(struct probe_trace_arg *arg,
 					struct strbuf *buf, int num);
+extern int get_bpf_prologue(struct perf_probe_event *pev,
+			char **result, int *count);
 
 /* Check the perf_probe_event needs debuginfo */
 extern bool perf_probe_event_need_dwarf(struct perf_probe_event *pev);
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 249e6cb..bfb7625 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1164,6 +1164,71 @@ static int expand_probe_args(Dwarf_Die *sc_die, struct probe_finder *pf,
 	return n;
 }
 
+#define BPF_PROLOGUE_MAX_LEN (1024)
+static int generate_bpf_prologue(Dwarf_Die *sc_die, struct probe_finder *pf)
+{
+	struct perf_probe_arg *args;
+	int ret = 0, i;
+	Dwarf_Die vr_die;
+	struct strbuf buf;
+	int narg;
+
+	if (pf->tvar)
+		return -ERANGE;
+
+	pf->tvar = (struct probe_trace_arg *)
+		malloc(sizeof(struct probe_trace_arg));
+	if (pf->tvar == NULL)
+		return -ENOMEM;
+
+	/* Expand special probe argument if exist */
+	args = zalloc(sizeof(struct perf_probe_arg) * MAX_PROBE_ARGS);
+	if (args == NULL)
+		return -ENOMEM;
+
+	narg = expand_probe_args(sc_die, pf, args);
+	if (narg <= 0)
+		goto end;
+
+	strbuf_init(&buf, BPF_PROLOGUE_MAX_LEN);
+	synthesize_probe_trace_arg_bpf_begin(&buf);
+
+	/* Find each argument */
+	for (i = 0; i < narg; i++) {
+		pf->pvar = &args[i];
+
+		memset(pf->tvar, 0, sizeof(struct probe_trace_arg));
+		/* Search child die for local variables and parameters. */
+		if (!die_find_variable_at(sc_die, pf->pvar->var,
+						pf->addr, &vr_die)) {
+			/* Search again in global variables */
+			if (!die_find_variable_at(&pf->cu_die, pf->pvar->var,
+							0, &vr_die)) {
+				pr_warning("Failed to find '%s' in this function.\n",
+					pf->pvar->var);
+				ret = -ENOENT;
+			}
+		}
+
+		if (ret >= 0)
+			ret = convert_variable(&vr_die, pf);
+		if (ret != 0)
+			break;
+
+		ret = synthesize_probe_trace_arg_bpf(pf->tvar, &buf, i);
+		if (ret)
+			goto end;
+	}
+
+	synthesize_probe_trace_arg_bpf_end(pf->tvar, &buf, narg);
+
+	pr_debug("bpf_prologue: insn num=%d\n", pf->tvar->insns_cnt);
+
+end:
+	free(args);
+	return ret;
+}
+
 /* Add a found probe point into trace event list */
 static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
 {
@@ -1248,6 +1313,31 @@ int debuginfo__find_trace_events(struct debuginfo *dbg,
 	return (ret < 0) ? ret : tf.ntevs;
 }
 
+int debuginfo__find_bpf_prologue(struct debuginfo *dbg,
+				struct perf_probe_event *pev,
+				char **result, int *count)
+{
+	struct probe_finder pf = {.pev = pev,
+				  .callback = generate_bpf_prologue};
+	int ret;
+
+	pf.tvar = NULL;
+	ret = debuginfo__find_probes(dbg, &pf);
+	if (ret == -ERANGE)
+		ret = 0;
+
+	if (pf.tvar) {
+		*result = pf.tvar->insns;
+		*count = pf.tvar->insns_cnt;
+		free(pf.tvar);
+	} else {
+		*result = NULL;
+		*count = 0;
+	}
+
+	return ret;
+}
+
 #define MAX_VAR_LEN 64
 
 /* Collect available variables in this scope */
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index ebf8c8c..28437978 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -40,6 +40,10 @@ extern int debuginfo__find_trace_events(struct debuginfo *dbg,
 					struct probe_trace_event **tevs,
 					int max_tevs);
 
+extern int debuginfo__find_bpf_prologue(struct debuginfo *dbg,
+					struct perf_probe_event *pev,
+					char **result, int *count);
+
 /* Find a perf_probe_point from debuginfo */
 extern int debuginfo__find_probe_point(struct debuginfo *dbg,
 				       unsigned long addr,
-- 
1.8.5.2