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    SubjectRe: [PATCH 13/24] perf tools: Allow mmap2 event to synthesize kernel image
    On Tue, Nov 17, 2020 at 09:44:37AM -0300, Arnaldo Carvalho de Melo wrote:
    > Em Tue, Nov 17, 2020 at 12:00:42PM +0100, Jiri Olsa escreveu:
    > > Allow mmap2 event to synthesize kernel image,
    > > so we can synthesize kernel build id data in
    > > following changes.
    > >
    > > It's enabled by new symbol_conf.buildid_mmap2
    > > bool, which will be switched in following
    > > changes.
    >
    > Why make this an option? MMAP2 goes back years:
    >
    > 13d7a2410fa637f45 (Stephane Eranian 2013-08-21 12:10:24 +0200 904) * The MMAP2 records are an augmented version of MMAP, they add
    > 13d7a2410fa637f45 (Stephane Eranian 2013-08-21 12:10:24 +0200 905) * maj, min, ino numbers to be used to uniquely identify each mapping
    >
    > Also we unconditionally generate MMAP2 events if the kernel supports it,
    > from evsel__config():
    >
    > attr->mmap = track;
    > attr->mmap2 = track && !perf_missing_features.mmap2;
    >
    > So perhaps we should reuse that logic? I.e. use mmap2 if the kernel
    > supports it?

    mmap2 itself is not a problem, the problem is the new
    bit (PERF_RECORD_MISC_MMAP_BUILD_ID) that says there's
    build id in mmap2.. older perf tool won't understand
    that and report will crash

    jirka

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