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Subject[PATCH 34/44] perf bpf: Save BTF information as headers to perf.data
Date
From: Song Liu <songliubraving@fb.com>

This patch enables 'perf record' to save BTF information as headers to
perf.data.

A new header type HEADER_BPF_BTF is introduced for this data.

Committer testing:

As root, being on the kernel sources top level directory, run:

# perf trace -e tools/perf/examples/bpf/augmented_raw_syscalls.c -e *msg

Just to compile and load a BPF program that attaches to the
raw_syscalls:sys_{enter,exit} tracepoints to trace the syscalls ending
in "msg" (recvmsg, sendmsg, recvmmsg, sendmmsg, etc).

Make sure you have a recent enough clang, say version 9, to get the
BTF ELF sections needed for this testing:

# clang --version | head -1
clang version 9.0.0 (https://git.llvm.org/git/clang.git/ 7906282d3afec5dfdc2b27943fd6c0309086c507) (https://git.llvm.org/git/llvm.git/ a1b5de1ff8ae8bc79dc8e86e1f82565229bd0500)
# readelf -SW tools/perf/examples/bpf/augmented_raw_syscalls.o | grep BTF
[22] .BTF PROGBITS 0000000000000000 000ede 000b0e 00 0 0 1
[23] .BTF.ext PROGBITS 0000000000000000 0019ec 0002a0 00 0 0 1
[24] .rel.BTF.ext REL 0000000000000000 002fa8 000270 10 30 23 8

Then do a systemwide perf record session for a few seconds:

# perf record -a sleep 2s

Then look at:

# perf report --header-only | grep b[pt]f
# event : name = cycles:ppp, , id = { 1116204, 1116205, 1116206, 1116207, 1116208, 1116209, 1116210, 1116211 }, size = 112, { sample_period, sample_freq } = 4000, sample_type = IP|TID|TIME|PERIOD, read_format = ID, disabled = 1, inherit = 1, mmap = 1, comm = 1, freq = 1, enable_on_exec = 1, task = 1, precise_ip = 3, sample_id_all = 1, exclude_guest = 1, mmap2 = 1, comm_exec = 1, ksymbol = 1, bpf_event = 1
# bpf_prog_info of id 13
# bpf_prog_info of id 14
# bpf_prog_info of id 15
# bpf_prog_info of id 16
# bpf_prog_info of id 17
# bpf_prog_info of id 18
# bpf_prog_info of id 21
# bpf_prog_info of id 22
# bpf_prog_info of id 51
# bpf_prog_info of id 52
# btf info of id 8
#

We need to show more info about these BPF and BTF entries , but that can
be done later.

Signed-off-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: kernel-team@fb.com
Link: http://lkml.kernel.org/r/20190312053051.2690567-10-songliubraving@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/header.c | 101 ++++++++++++++++++++++++++++++++++++++-
tools/perf/util/header.h | 1 +
2 files changed, 101 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index e6a81af516f6..01dda2f65d36 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -928,6 +928,39 @@ static int write_bpf_prog_info(struct feat_fd *ff __maybe_unused,
}
#endif // HAVE_LIBBPF_SUPPORT

+static int write_bpf_btf(struct feat_fd *ff,
+ struct perf_evlist *evlist __maybe_unused)
+{
+ struct perf_env *env = &ff->ph->env;
+ struct rb_root *root;
+ struct rb_node *next;
+ int ret;
+
+ down_read(&env->bpf_progs.lock);
+
+ ret = do_write(ff, &env->bpf_progs.btfs_cnt,
+ sizeof(env->bpf_progs.btfs_cnt));
+
+ if (ret < 0)
+ goto out;
+
+ root = &env->bpf_progs.btfs;
+ next = rb_first(root);
+ while (next) {
+ struct btf_node *node;
+
+ node = rb_entry(next, struct btf_node, rb_node);
+ next = rb_next(&node->rb_node);
+ ret = do_write(ff, &node->id,
+ sizeof(u32) * 2 + node->data_size);
+ if (ret < 0)
+ goto out;
+ }
+out:
+ up_read(&env->bpf_progs.lock);
+ return ret;
+}
+
static int cpu_cache_level__sort(const void *a, const void *b)
{
struct cpu_cache_level *cache_a = (struct cpu_cache_level *)a;
@@ -1442,6 +1475,28 @@ static void print_bpf_prog_info(struct feat_fd *ff, FILE *fp)
up_read(&env->bpf_progs.lock);
}

+static void print_bpf_btf(struct feat_fd *ff, FILE *fp)
+{
+ struct perf_env *env = &ff->ph->env;
+ struct rb_root *root;
+ struct rb_node *next;
+
+ down_read(&env->bpf_progs.lock);
+
+ root = &env->bpf_progs.btfs;
+ next = rb_first(root);
+
+ while (next) {
+ struct btf_node *node;
+
+ node = rb_entry(next, struct btf_node, rb_node);
+ next = rb_next(&node->rb_node);
+ fprintf(fp, "# btf info of id %u\n", node->id);
+ }
+
+ up_read(&env->bpf_progs.lock);
+}
+
static void free_event_desc(struct perf_evsel *events)
{
struct perf_evsel *evsel;
@@ -2564,6 +2619,49 @@ static int process_bpf_prog_info(struct feat_fd *ff __maybe_unused, void *data _
}
#endif // HAVE_LIBBPF_SUPPORT

+static int process_bpf_btf(struct feat_fd *ff, void *data __maybe_unused)
+{
+ struct perf_env *env = &ff->ph->env;
+ u32 count, i;
+
+ if (ff->ph->needs_swap) {
+ pr_warning("interpreting btf from systems with endianity is not yet supported\n");
+ return 0;
+ }
+
+ if (do_read_u32(ff, &count))
+ return -1;
+
+ down_write(&env->bpf_progs.lock);
+
+ for (i = 0; i < count; ++i) {
+ struct btf_node *node;
+ u32 id, data_size;
+
+ if (do_read_u32(ff, &id))
+ return -1;
+ if (do_read_u32(ff, &data_size))
+ return -1;
+
+ node = malloc(sizeof(struct btf_node) + data_size);
+ if (!node)
+ return -1;
+
+ node->id = id;
+ node->data_size = data_size;
+
+ if (__do_read(ff, node->data, data_size)) {
+ free(node);
+ return -1;
+ }
+
+ perf_env__insert_btf(env, node);
+ }
+
+ up_write(&env->bpf_progs.lock);
+ return 0;
+}
+
struct feature_ops {
int (*write)(struct feat_fd *ff, struct perf_evlist *evlist);
void (*print)(struct feat_fd *ff, FILE *fp);
@@ -2625,7 +2723,8 @@ static const struct feature_ops feat_ops[HEADER_LAST_FEATURE] = {
FEAT_OPR(MEM_TOPOLOGY, mem_topology, true),
FEAT_OPR(CLOCKID, clockid, false),
FEAT_OPN(DIR_FORMAT, dir_format, false),
- FEAT_OPR(BPF_PROG_INFO, bpf_prog_info, false)
+ FEAT_OPR(BPF_PROG_INFO, bpf_prog_info, false),
+ FEAT_OPR(BPF_BTF, bpf_btf, false),
};

struct header_print_data {
diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
index 1dc85f0f895d..386da49e1bfa 100644
--- a/tools/perf/util/header.h
+++ b/tools/perf/util/header.h
@@ -41,6 +41,7 @@ enum {
HEADER_CLOCKID,
HEADER_DIR_FORMAT,
HEADER_BPF_PROG_INFO,
+ HEADER_BPF_BTF,
HEADER_LAST_FEATURE,
HEADER_FEAT_BITS = 256,
};
--
2.20.1
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