Subject: Re: [PATCH v4 perf,bpf 06/15] perf, bpf: save bpf_prog_info in a rbtree in perf_env

From: Jiri Olsa <[email-masked]>
Date: Wed, 27 Feb 2019 14:21:23 +0100

On Mon, Feb 25, 2019 at 04:20:10PM -0800, Song Liu wrote:
> bpf_prog_info contains information necessary to annotate bpf programs.
> This patch saves bpf_prog_info for bpf programs loaded in the system.
> 
> Signed-off-by: Song Liu <[email-masked]>
> ---
>  tools/perf/util/bpf-event.c | 32 +++++++++++++-
>  tools/perf/util/bpf-event.h |  7 ++-
>  tools/perf/util/env.c       | 85 +++++++++++++++++++++++++++++++++++++
>  tools/perf/util/env.h       | 17 ++++++++
>  4 files changed, 139 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
> index ff7ee149ec46..ce81b2c43a51 100644
> --- a/tools/perf/util/bpf-event.c
> +++ b/tools/perf/util/bpf-event.c
> @@ -10,6 +10,7 @@
>  #include "debug.h"
>  #include "symbol.h"
>  #include "machine.h"
> +#include "env.h"
>  #include "session.h"
>  
>  #define ptr_to_u64(ptr)    ((__u64)(unsigned long)(ptr))
> @@ -54,17 +55,28 @@ static int perf_event__synthesize_one_bpf_prog(struct perf_session *session,
>  	struct bpf_event *bpf_event = &event->bpf_event;
>  	struct bpf_prog_info_linear *info_linear;
>  	struct perf_tool *tool = session->tool;
> +	struct bpf_prog_info_node *info_node;
>  	struct bpf_prog_info *info;
>  	struct btf *btf = NULL;
>  	bool has_btf = false;
> +	struct perf_env *env;
>  	u32 sub_prog_cnt, i;
>  	int err = 0;
>  	u64 arrays;
>  
> +	/*
> +	 * for perf-record and perf-report use header.env;
> +	 * otherwise, use global perf_env.
> +	 */
> +	env = session->data ? &session->header.env : &perf_env;
> +
>  	arrays = 1UL << BPF_PROG_INFO_JITED_KSYMS;
>  	arrays |= 1UL << BPF_PROG_INFO_JITED_FUNC_LENS;
>  	arrays |= 1UL << BPF_PROG_INFO_FUNC_INFO;
>  	arrays |= 1UL << BPF_PROG_INFO_PROG_TAGS;
> +	arrays |= 1UL << BPF_PROG_INFO_JITED_INSNS;
> +	arrays |= 1UL << BPF_PROG_INFO_LINE_INFO;
> +	arrays |= 1UL << BPF_PROG_INFO_JITED_LINE_INFO;
>  
>  	info_linear = bpf_program__get_prog_info_linear(fd, arrays);
>  	if (IS_ERR_OR_NULL(info_linear)) {
> @@ -153,8 +165,8 @@ static int perf_event__synthesize_one_bpf_prog(struct perf_session *session,
>  						     machine, process);
>  	}
>  
> -	/* Synthesize PERF_RECORD_BPF_EVENT */
>  	if (opts->bpf_event) {
> +		/* Synthesize PERF_RECORD_BPF_EVENT */
>  		*bpf_event = (struct bpf_event){
>  			.header = {
>  				.type = PERF_RECORD_BPF_EVENT,
> @@ -167,6 +179,24 @@ static int perf_event__synthesize_one_bpf_prog(struct perf_session *session,
>  		memcpy(bpf_event->tag, info->tag, BPF_TAG_SIZE);
>  		memset((void *)event + event->header.size, 0, machine->id_hdr_size);
>  		event->header.size += machine->id_hdr_size;
> +
> +		/* save bpf_prog_info to env */

why do we save this to perf_env in here? we just
synthesize the same data as event, so report and
top will read it and fill perf_env again, right?

could you please explain the whole flow of the
bpf events and its respective data in perf_env
and put it into the changelog

> +		info_node = malloc(sizeof(struct bpf_prog_info_node));
> +
> +		/*
> +		 * Do not bail out for !info_node, as we still want to
> +		 * call  perf_tool__process_synth_event()

well, we are out of memory, so I dont think perf_tool__process_synth_event
will get too far.. also the perf_env data would be inconsistent with what
you store as event.. how can that work?

thanks,
jirka

> +		 */
> +		if (info_node) {
> +			info_node->info_linear = info_linear;
> +			perf_env__insert_bpf_prog_info(env, info_node);
> +			info_linear = NULL;
> +		}
> +

SNIP