[RFC PATCH v2 10/15] 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(), with 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 | 93 ++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/probe-finder.h |  4 ++
 4 files changed, 126 insertions(+)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 7f9f431..ccbf4d9 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -914,6 +914,33 @@ 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 6c19395..3eb0183 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -106,6 +106,8 @@ extern char *synthesize_perf_probe_command(struct perf_probe_event *pev);
 extern char *synthesize_probe_trace_command(struct probe_trace_event *tev);
 extern int synthesize_perf_probe_arg(struct perf_probe_arg *pa, char *buf,
 				     size_t len);
+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 4de7649..6785eab 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -39,6 +39,7 @@
 #include "util.h"
 #include "symbol.h"
 #include "probe-finder.h"
+#include <bpf/libbpf.h>
 
 /* Kprobe tracer basic type is up to u64 */
 #define MAX_BASIC_TYPE_BITS	64
@@ -1177,6 +1178,70 @@ static int expand_probe_args(Dwarf_Die *sc_die, struct probe_finder *pf,
 	return n;
 }
 
+static int generate_bpf_prologue(Dwarf_Die *sc_die, struct probe_finder *pf)
+{
+	struct trace_event_finder *tf =
+			container_of(pf, struct trace_event_finder, pf);
+	struct probe_trace_event *tev;
+	struct perf_probe_arg *args;
+	int ret, i;
+	Dwarf_Die vr_die;
+
+	/* Check number of tevs */
+	if (tf->ntevs == tf->max_tevs) {
+		pr_warning("Too many( > %d) probe point found.\n",
+			   tf->max_tevs);
+		return -ERANGE;
+	}
+	tev = &tf->tevs[tf->ntevs++];
+
+	/* Expand special probe argument if exist */
+	args = zalloc(sizeof(struct perf_probe_arg) * MAX_PROBE_ARGS);
+	if (args == NULL)
+		return -ENOMEM;
+
+	ret = expand_probe_args(sc_die, pf, args);
+	if (ret <= 0)
+		goto end;
+
+	/* restrict nargs <= BPF_PROLOGUE_NRARGS_MAX */
+	if (ret > BPF_PROLOGUE_NRARGS_MAX)
+		ret = BPF_PROLOGUE_NRARGS_MAX;
+
+	tev->nargs = ret;
+	tev->args = zalloc(sizeof(struct probe_trace_arg) * tev->nargs);
+	if (tev->args == NULL) {
+		ret = -ENOMEM;
+		goto end;
+	}
+
+	/* Find each argument */
+	for (i = 0; i < tev->nargs; i++) {
+		pf->pvar = &args[i];
+		pf->tvar = &tev->args[i];
+
+		/* 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;
+	}
+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)
 {
@@ -1261,6 +1326,34 @@ int debuginfo__find_trace_events(struct debuginfo *dbg,
 	return (ret < 0) ? ret : tf.ntevs;
 }
 
+#define BPF_MAX_TEVS	(1)
+int debuginfo__find_bpf_prologue(struct debuginfo *dbg,
+				struct perf_probe_event *pev,
+				char **result, int *count)
+{
+	struct trace_event_finder tf = {
+			.pf = {.pev = pev, .callback = generate_bpf_prologue},
+			.mod = dbg->mod, .max_tevs = BPF_MAX_TEVS};
+	struct probe_trace_event *tevs;
+	int ret;
+
+	/* Allocate result tevs array */
+	tevs = zalloc(sizeof(struct probe_trace_event) * BPF_MAX_TEVS);
+	if (tevs == NULL)
+		return -ENOMEM;
+
+	tf.tevs = tevs;
+	tf.ntevs = 0;
+
+	ret = debuginfo__find_probes(dbg, &tf.pf);
+
+	*result = NULL;
+	*count = 0;
+
+	free(tevs);
+	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 f53553d..f046c63 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -43,6 +43,10 @@ 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