Subject: Re: [PATCH v2 perf,bpf 08/11] perf, bpf: save btf information as headers to perf.data

From: Arnaldo Carvalho de Melo <[email-masked]>
Date: Fri, 15 Feb 2019 12:26:43 -0200

Em Thu, Feb 14, 2019 at 04:00:09PM -0800, Song Liu escreveu:
> This patch enables perf-record to save btf information as headers to
> perf.data A new header type HEADER_BTF is introduced for this data.

Jiri,

	Wouldn't it be better for this HEADER_BTF to be introduced
already as an user space event, Song, see:

  tools/perf/util/event.h

and:

  tools/perf/util/event.c

perf_event__synthesize_cpu_map()

- Arnaldo

> Signed-off-by: Song Liu <[email-masked]>
> ---
>  tools/perf/util/header.c | 99 +++++++++++++++++++++++++++++++++++++++-
>  tools/perf/util/header.h |  1 +
>  2 files changed, 99 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index 2ae76a9d06f6..3f1562afe8e5 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -1125,6 +1125,45 @@ static int write_bpf_prog_info(struct feat_fd *ff,
>  	return ret;
>  }
>  
> +static int write_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_info_lock);
> +
> +	root = &env->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,
> +			       sizeof(struct btf_node) + node->data_size);
> +		if (ret < 0)
> +			goto out;
> +	}
> +out:
> +	up_read(&env->bpf_info_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;
> @@ -1628,6 +1667,28 @@ static void print_bpf_prog_info(struct feat_fd *ff, FILE *fp)
>  	up_read(&env->bpf_info_lock);
>  }
>  
> +static void print_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_info_lock);
> +
> +	root = &env->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, "# bpf_prog_info of id %u\n", node->id);
> +	}
> +
> +	up_read(&env->bpf_info_lock);
> +}
> +
>  static void free_event_desc(struct perf_evsel *events)
>  {
>  	struct perf_evsel *evsel;
> @@ -2723,6 +2784,41 @@ static int process_bpf_prog_info(struct feat_fd *ff,
>  	return err;
>  }
>  
> +static int process_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;
> +
> +	down_write(&env->bpf_info_lock);
> +
> +	for (i = 0; i < count; ++i) {
> +		struct btf_node btf_node;
> +		struct btf_node *node;
> +
> +		if (__do_read(ff, &btf_node, sizeof(struct btf_node)))
> +			return -1;
> +
> +		node = malloc(sizeof(struct btf_node) + btf_node.data_size);
> +		if (!node)
> +			return -1;
> +
> +		node->id = btf_node.id;
> +		node->data_size = btf_node.data_size;
> +
> +		if (__do_read(ff, node->data, btf_node.data_size)) {
> +			free(node);
> +			return -1;
> +		}
> +		perf_env__insert_btf(env, node);
> +	}
> +
> +	up_write(&env->bpf_info_lock);
> +	return 0;
> +}
> +
>  struct feature_ops {
>  	int (*write)(struct feat_fd *ff, struct perf_evlist *evlist);
>  	void (*print)(struct feat_fd *ff, FILE *fp);
> @@ -2783,7 +2879,8 @@ 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(BTF,           btf,            false)
>  };
>  
>  struct header_print_data {
> diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
> index 0785c91b4c3a..ba51d8e43c53 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_BTF,
>  	HEADER_LAST_FEATURE,
>  	HEADER_FEAT_BITS	= 256,
>  };
> -- 
> 2.17.1