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Subject[PATCH v11 perf, bpf-next 7/9] perf tools: synthesize PERF_RECORD_* for loaded BPF programs
Date
This patch synthesize PERF_RECORD_KSYMBOL and PERF_RECORD_BPF_EVENT for
BPF programs loaded before perf-record. This is achieved by gathering
information about all BPF programs via sys_bpf.

Signed-off-by: Song Liu <songliubraving@fb.com>
---
tools/perf/builtin-record.c | 6 +
tools/perf/util/bpf-event.c | 241 ++++++++++++++++++++++++++++++++++++
tools/perf/util/bpf-event.h | 5 +
3 files changed, 252 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index deaf9b902094..88ea11d57c6f 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -41,6 +41,7 @@
#include "util/perf-hooks.h"
#include "util/time-utils.h"
#include "util/units.h"
+#include "util/bpf-event.h"
#include "asm/bug.h"

#include <errno.h>
@@ -1082,6 +1083,11 @@ static int record__synthesize(struct record *rec, bool tail)
return err;
}

+ err = perf_event__synthesize_bpf_events(tool, process_synthesized_event,
+ machine, opts);
+ if (err < 0)
+ pr_warning("Couldn't synthesize bpf events.\n");
+
err = __machine__synthesize_threads(machine, tool, &opts->target, rec->evlist->threads,
process_synthesized_event, opts->sample_address,
1);
diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
index 87004706874f..126f9728a756 100644
--- a/tools/perf/util/bpf-event.c
+++ b/tools/perf/util/bpf-event.c
@@ -1,10 +1,24 @@
// SPDX-License-Identifier: GPL-2.0
#include <errno.h>
#include <bpf/bpf.h>
+#include <bpf/btf.h>
+#include <linux/btf.h>
#include "bpf-event.h"
#include "debug.h"
#include "symbol.h"

+#define ptr_to_u64(ptr) ((__u64)(unsigned long)(ptr))
+
+static int snprintf_hex(char *buf, size_t size, unsigned char *data, size_t len)
+{
+ int ret = 0;
+ size_t i;
+
+ for (i = 0; i < len; i++)
+ ret += snprintf(buf + ret, size - ret, "%02x", data[i]);
+ return ret;
+}
+
int machine__process_bpf_event(struct machine *machine __maybe_unused,
union perf_event *event,
struct perf_sample *sample __maybe_unused)
@@ -13,3 +27,230 @@ int machine__process_bpf_event(struct machine *machine __maybe_unused,
perf_event__fprintf_bpf_event(event, stdout);
return 0;
}
+
+/*
+ * Synthesize PERF_RECORD_KSYMBOL and PERF_RECORD_BPF_EVENT for one bpf
+ * program. One PERF_RECORD_BPF_EVENT is generated for the program. And
+ * one PERF_RECORD_KSYMBOL is generated for each sub program.
+ *
+ * Returns:
+ * 0 for success;
+ * -1 for failures;
+ * -2 for lack of kernel support.
+ */
+static int perf_event__synthesize_one_bpf_prog(struct perf_tool *tool,
+ perf_event__handler_t process,
+ struct machine *machine,
+ int fd,
+ union perf_event *event,
+ struct record_opts *opts)
+{
+ struct ksymbol_event *ksymbol_event = &event->ksymbol_event;
+ struct bpf_event *bpf_event = &event->bpf_event;
+ u32 sub_prog_cnt, i, func_info_rec_size;
+ u8 (*prog_tags)[BPF_TAG_SIZE] = NULL;
+ struct bpf_prog_info info = {};
+ u32 info_len = sizeof(info);
+ void *func_infos = NULL;
+ u64 *prog_addrs = NULL;
+ struct btf *btf = NULL;
+ u32 *prog_lens = NULL;
+ bool has_btf = false;
+ char errbuf[512];
+ int err = 0;
+
+ /* Call bpf_obj_get_info_by_fd() to get sizes of arrays */
+ err = bpf_obj_get_info_by_fd(fd, &info, &info_len);
+
+ if (err) {
+ pr_debug("%s: failed to get BPF program info: %s, aborting\n",
+ __func__, str_error_r(errno, errbuf, sizeof(errbuf)));
+ return -1;
+ }
+ if (info_len < offsetof(struct bpf_prog_info, prog_tags)) {
+ pr_debug("%s: the kernel is too old, aborting\n", __func__);
+ return -2;
+ }
+
+ /* number of ksyms, func_lengths, and tags should match */
+ sub_prog_cnt = info.nr_jited_ksyms;
+ if (sub_prog_cnt != info.nr_prog_tags ||
+ sub_prog_cnt != info.nr_jited_func_lens)
+ return -1;
+
+ /* check BTF func info support */
+ if (info.btf_id && info.nr_func_info && info.func_info_rec_size) {
+ /* btf func info number should be same as sub_prog_cnt */
+ if (sub_prog_cnt != info.nr_func_info) {
+ pr_debug("%s: mismatch in BPF sub program count and BTF function info count, aborting\n", __func__);
+ return -1;
+ }
+ if (btf__get_from_id(info.btf_id, &btf)) {
+ pr_debug("%s: failed to get BTF of id %u, aborting\n", __func__, info.btf_id);
+ return -1;
+ }
+ func_info_rec_size = info.func_info_rec_size;
+ func_infos = calloc(sub_prog_cnt, func_info_rec_size);
+ if (!func_infos) {
+ pr_debug("%s: failed to allocate memory for func_infos, aborting\n", __func__);
+ return -1;
+ }
+ has_btf = true;
+ }
+
+ /*
+ * We need address, length, and tag for each sub program.
+ * Allocate memory and call bpf_obj_get_info_by_fd() again
+ */
+ prog_addrs = calloc(sub_prog_cnt, sizeof(u64));
+ if (!prog_addrs) {
+ pr_debug("%s: failed to allocate memory for prog_addrs, aborting\n", __func__);
+ goto out;
+ }
+ prog_lens = calloc(sub_prog_cnt, sizeof(u32));
+ if (!prog_lens) {
+ pr_debug("%s: failed to allocate memory for prog_lens, aborting\n", __func__);
+ goto out;
+ }
+ prog_tags = calloc(sub_prog_cnt, BPF_TAG_SIZE);
+ if (!prog_tags) {
+ pr_debug("%s: failed to allocate memory for prog_tags, aborting\n", __func__);
+ goto out;
+ }
+
+ memset(&info, 0, sizeof(info));
+ info.nr_jited_ksyms = sub_prog_cnt;
+ info.nr_jited_func_lens = sub_prog_cnt;
+ info.nr_prog_tags = sub_prog_cnt;
+ info.jited_ksyms = ptr_to_u64(prog_addrs);
+ info.jited_func_lens = ptr_to_u64(prog_lens);
+ info.prog_tags = ptr_to_u64(prog_tags);
+ info_len = sizeof(info);
+ if (has_btf) {
+ info.nr_func_info = sub_prog_cnt;
+ info.func_info_rec_size = func_info_rec_size;
+ info.func_info = ptr_to_u64(func_infos);
+ }
+
+ err = bpf_obj_get_info_by_fd(fd, &info, &info_len);
+ if (err) {
+ pr_debug("%s: failed to get BPF program info, aborting\n", __func__);
+ goto out;
+ }
+
+ /* Synthesize PERF_RECORD_KSYMBOL */
+ for (i = 0; i < sub_prog_cnt; i++) {
+ const struct bpf_func_info *finfo;
+ const char *short_name = NULL;
+ const struct btf_type *t;
+ int name_len;
+
+ *ksymbol_event = (struct ksymbol_event){
+ .header = {
+ .type = PERF_RECORD_KSYMBOL,
+ .size = sizeof(struct ksymbol_event),
+ },
+ .addr = prog_addrs[i],
+ .len = prog_lens[i],
+ .ksym_type = PERF_RECORD_KSYMBOL_TYPE_BPF,
+ .flags = 0,
+ };
+ name_len = snprintf(ksymbol_event->name, KSYM_NAME_LEN,
+ "bpf_prog_");
+ name_len += snprintf_hex(ksymbol_event->name + name_len,
+ KSYM_NAME_LEN - name_len,
+ prog_tags[i], BPF_TAG_SIZE);
+ if (has_btf) {
+ finfo = func_infos + i * info.func_info_rec_size;
+ t = btf__type_by_id(btf, finfo->type_id);
+ short_name = btf__name_by_offset(btf, t->name_off);
+ } else if (i == 0 && sub_prog_cnt == 1) {
+ /* no subprog */
+ if (info.name[0])
+ short_name = info.name;
+ } else
+ short_name = "F";
+ if (short_name)
+ name_len += snprintf(ksymbol_event->name + name_len,
+ KSYM_NAME_LEN - name_len,
+ "_%s", short_name);
+
+ ksymbol_event->header.size += PERF_ALIGN(name_len + 1,
+ sizeof(u64));
+ err = perf_tool__process_synth_event(tool, event,
+ machine, process);
+ }
+
+ /* Synthesize PERF_RECORD_BPF_EVENT */
+ if (opts->bpf_event) {
+ *bpf_event = (struct bpf_event){
+ .header = {
+ .type = PERF_RECORD_BPF_EVENT,
+ .size = sizeof(struct bpf_event),
+ },
+ .type = PERF_BPF_EVENT_PROG_LOAD,
+ .flags = 0,
+ .id = info.id,
+ };
+ memcpy(bpf_event->tag, prog_tags[i], BPF_TAG_SIZE);
+ err = perf_tool__process_synth_event(tool, event,
+ machine, process);
+ }
+
+out:
+ free(prog_tags);
+ free(prog_lens);
+ free(prog_addrs);
+ free(func_infos);
+ free(btf);
+ return err ? -1 : 0;
+}
+
+int perf_event__synthesize_bpf_events(struct perf_tool *tool,
+ perf_event__handler_t process,
+ struct machine *machine,
+ struct record_opts *opts)
+{
+ union perf_event *event;
+ __u32 id = 0;
+ int err;
+ int fd;
+
+ event = malloc(sizeof(event->bpf_event) + KSYM_NAME_LEN);
+ if (!event)
+ return -1;
+ while (true) {
+ err = bpf_prog_get_next_id(id, &id);
+ if (err) {
+ if (errno == ENOENT) {
+ err = 0;
+ break;
+ }
+ pr_debug("%s: can't get next program: %s%s",
+ __func__, strerror(errno),
+ errno == EINVAL ? " -- kernel too old?" : "");
+ /* don't report error on old kernel */
+ err = (errno == EINVAL) ? 0 : -1;
+ break;
+ }
+ fd = bpf_prog_get_fd_by_id(id);
+ if (fd < 0) {
+ pr_debug("%s: failed to get fd for prog_id %u\n",
+ __func__, id);
+ continue;
+ }
+
+ err = perf_event__synthesize_one_bpf_prog(tool, process,
+ machine, fd,
+ event, opts);
+ close(fd);
+ if (err) {
+ /* do not return error for old kernel */
+ if (err == -2)
+ err = 0;
+ break;
+ }
+ }
+ free(event);
+ return err;
+}
diff --git a/tools/perf/util/bpf-event.h b/tools/perf/util/bpf-event.h
index d5ca355dd298..38aee4040f12 100644
--- a/tools/perf/util/bpf-event.h
+++ b/tools/perf/util/bpf-event.h
@@ -8,4 +8,9 @@ int machine__process_bpf_event(struct machine *machine,
union perf_event *event,
struct perf_sample *sample);

+int perf_event__synthesize_bpf_events(struct perf_tool *tool,
+ perf_event__handler_t process,
+ struct machine *machine,
+ struct record_opts *opts);
+
#endif
--
2.17.1
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