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    SubjectRe: [tip:perf/urgent] perf symbols: Handle /proc/sys/kernel/kptr_restrict

    * Arnaldo Carvalho de Melo <acme@redhat.com> wrote:

    > Em Thu, May 26, 2011 at 09:39:46PM +0200, Ingo Molnar escreveu:
    > > Secondly, even though i have the proper 'vmlinux' in cwd, i get half
    > > a page long warnings on perf record warning me about the vmlinux:
    > >
    > > WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted, check /proc/sys/kernel/kptr_restrict.
    > >
    > > Samples in kernel functions may not be resolved if a suitable
    > > vmlinux file is not found in the buildid cache or in the vmlinux
    > > path.
    > >
    > > ...
    > >
    > > But a vmlinux file *is* in the cwd.
    >
    > Well, there was no assumption that 'perf report' would run on the same
    > directory as 'perf record', the user may have moved to a different
    > directory or transferred the perf.data file to a different machine.
    >
    > Also it would have to check that the vmlinux on the path is suitable
    > (that build-id matches), currently it does that just at 'perf report'
    > time, that is when it will need to use it. At record time we just
    > collect the build-ids.
    >
    > With that in mind, how do you think it should be phrased?

    I think the biggest problem is that it is yelling at us even when i'm
    root - and root can access all the pointer values just fine:

    # id
    uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

    # perf report --stdio
    No kallsyms or vmlinux with build-id 122214021a666675f6e5ff97d70a85ce7139c0e7 was found
    [kernel.kallsyms] with build id 122214021a666675f6e5ff97d70a85ce7139c0e7 not found, continuing without s
    Kernel address maps (/proc/{kallsyms,modules}) were restricted, check /proc/sys/kernel/kptr_restrict bef

    # tail -1 /proc/kallsyms
    ffffffffff600d00 D __vvar_vsyscall_gtod_data

    Thanks,

    Ingo


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