Subject: Re: [PATCH v9 perf,bpf 09/15] perf, bpf: save btf information as headers to perf.data

From: Arnaldo Carvalho de Melo <[email-masked]>
Date: Tue, 12 Mar 2019 12:14:05 -0300

Em Mon, Mar 11, 2019 at 10:30:45PM -0700, Song Liu escreveu:
> 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 <[email-masked]>
> ---
>  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 a4ef8f657ad0..7decd2d1dbda 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -905,6 +905,39 @@ 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;
> +	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;
> @@ -1408,6 +1441,28 @@ 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);

So, I couldn't get this to work right now, and I have BPF programs that
are loaded and that have BTF info:

[root@quaco ~]# bpftool prog | tail -6
208: tracepoint  name sys_enter  tag 819967866022f1e1  gpl
	loaded_at 2019-03-12T11:16:55-0300  uid 0
	xlated 528B  jited 381B  memlock 4096B  map_ids 107,106,105
209: tracepoint  name sys_exit  tag c1bd85c092d6e4aa  gpl
	loaded_at 2019-03-12T11:16:55-0300  uid 0
	xlated 256B  jited 191B  memlock 4096B  map_ids 107,106
[root@quaco ~]#

[root@quaco ~]# bpftool map  | tail -6
105: perf_event_array  name __augmented_sys  flags 0x0
	key 4B  value 4B  max_entries 8  memlock 4096B
106: array  name syscalls  flags 0x0
	key 4B  value 1B  max_entries 512  memlock 8192B
107: hash  name pids_filtered  flags 0x0
	key 4B  value 1B  max_entries 64  memlock 8192B
[root@quaco ~]#

[root@quaco ~]# bpftool map dump id 107
[{
        "key": 8104,
        "value": true
    },{
        "key": 18868,
        "value": true
    }
]
[root@quaco ~]# ps ax|egrep 8104\|18868 | grep -v grep
 8104 pts/8    S+     0:07 trace -e recvmmsg
18868 ?        Ssl   21:21 /usr/libexec/gnome-terminal-server
[root@quaco ~]#

So I was expecting to see those btf lines there :-\

All the patches up to this point I have already merged and tested in my
local branch.

Will continue right after lunch to try to figure out why this BTF info
isn't landing on this new header feature...

- Arnaldo

> +	}
> +
> +	up_read(&env->bpf_progs.lock);
> +}
> +
>  static void free_event_desc(struct perf_evsel *events)
>  {
>  	struct perf_evsel *evsel;
> @@ -2509,6 +2564,49 @@ 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 (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);
> @@ -2569,7 +2667,8 @@ 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

-- 

- Arnaldo