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.

Signed-off-by: Song Liu <songliubrav...@fb.com>
---
 tools/perf/util/header.c | 111 ++++++++++++++++++++++++++++++++++++++-
 tools/perf/util/header.h |   1 +
 2 files changed, 111 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index cd19b7891db7..1a329da6011b 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1124,6 +1124,45 @@ static int write_bpf_prog_info(struct feat_fd *ff,
        return ret;
 }
 
+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;
+       u32 count = 0;
+       int ret;
+
+       down_read(&env->bpf_progs.lock);
+
+       root = &env->bpf_progs.btfs;
+       next = rb_first(root);
+       while (next) {
+               ++count;
+               next = rb_next(next);
+       }
+
+       ret = do_write(ff, &count, sizeof(count));
+
+       if (ret < 0)
+               goto out;
+
+       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;
@@ -1627,6 +1666,28 @@ 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;
@@ -2732,6 +2793,53 @@ static int process_bpf_prog_info(struct feat_fd *ff,
        return err;
 }
 
+static int process_bpf_btf(struct feat_fd *ff, void *data __maybe_unused)
+{
+       struct perf_env *env = &ff->ph->env;
+       u32 count, i;
+
+       if (do_read_u32(ff, &count))
+               return -1;
+
+       if (ff->ph->needs_swap)
+               pr_warning("interpreting btf from systems with endianity is not 
yet supported\n");
+
+       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;
+               }
+
+               /* endian mismatch, drop the btf, continue */
+               if (ff->ph->needs_swap) {
+                       free(node);
+                       continue;
+               }
+
+               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);
@@ -2792,7 +2900,8 @@ static const struct feature_ops 
feat_ops[HEADER_LAST_FEATURE] = {
        FEAT_OPR(SAMPLE_TIME,   sample_time,    false),
        FEAT_OPR(MEM_TOPOLOGY,  mem_topology,   true),
        FEAT_OPR(CLOCKID,       clockid,        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 0785c91b4c3a..9e7d931f7c0d 100644
--- a/tools/perf/util/header.h
+++ b/tools/perf/util/header.h
@@ -40,6 +40,7 @@ enum {
        HEADER_MEM_TOPOLOGY,
        HEADER_CLOCKID,
        HEADER_BPF_PROG_INFO,
+       HEADER_BPF_BTF,
        HEADER_LAST_FEATURE,
        HEADER_FEAT_BITS        = 256,
 };
-- 
2.17.1

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