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

From: Song Liu <songliubraving@fb.com>
To: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Cc: "bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	Networking <netdev@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Kernel Team <Kernel-team@fb.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	"Jiri Olsa" <jolsa@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	"sdf@fomichev.me" <sdf@fomichev.me>
Subject: Re: [PATCH v9 perf,bpf 09/15] perf, bpf: save btf information as headers to perf.data
Date: Tue, 12 Mar 2019 16:26:17 +0000	[thread overview]
Message-ID: <61901DA6-47B4-44E0-A0C9-9F2DBD6C34C1@fb.com> (raw)
In-Reply-To: <20190312151608.GH4939@kernel.org>

> On Mar 12, 2019, at 8:16 AM, Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> wrote:
> 
> Em Tue, Mar 12, 2019 at 12:14:05PM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Mon, Mar 11, 2019 at 10:30:45PM -0700, Song Liu escreveu:
>>> +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...
> 
> I've pushed what I have to my git.kernel.org repo, branch
> tmp.perf/bpf-annotate.
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git tmp.perf/bpf-annotate
> 
> The HEAD is this cset.
> 
> - Arnaldo

I am not sure I fully understand the problem here. 

I can get BTF information from this version:

# ~/perf report --header-only  | grep btf
# btf info of id 504

Thanks,
Song