Re: [PATCH v11 perf, bpf-next 7/9] perf tools: synthesize PERF_RECORD_* for loaded BPF programs

On Tue, Jan 22, 2019 at 06:38:56PM +0000, Song Liu wrote:

SNIP

quoted

quoted

in perf_session__process_event, this happens right when processing
buildids in 'perf record', and also in 'perf report', so that is
something badly synthesized that hits perf.data for PERF_RECORD_KSYMBOL.

it's reproducible with simple:
 perf record -e cycles,instructions ls

as you said on irc, it's the machine->id_hdr_size size missing
there's one more glitch, attached patch fixes that for me
you can't use sizeof(struct ksymbol_event), because it includes
the name as well.. which screws the size

but I don't know that code that much.. might be still something
missing

jirka

Hi Arnaldo and Jiri,

Thanks for catching and fixing the bug. 

I guess the following is OK?

        *bpf_event = (struct bpf_event){
                .header = {
                        .type = PERF_RECORD_BPF_EVENT,
                        .size = sizeof(struct bpf_event),
                },
                .type = PERF_BPF_EVENT_PROG_LOAD,
                .flags = 0,
                .id = info.id,
        };

as struct bpf_event doesn't have variable length name:

        struct bpf_event {
                struct perf_event_header header;
                u16 type;
                u16 flags;
                u32 id;

                /* for bpf_prog types */
                u8 tag[BPF_TAG_SIZE];  // prog tag
        };

Or we need similar fix? 

yep, looks good.. also don't forget to add the 'machine->id_hdr_size'

jirka