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    SubjectRe: [PATCH] perf report: fix crash showing warning related to kernel maps
    Hi Arnaldo:

    Haven't seen this one come through your urgent queue.

    On 4/10/12 10:15 AM, David Ahern wrote:
    > While testing https://lkml.org/lkml/2012/4/10/123 I hit this crash:
    >
    > (gdb) bt
    > 0 0x000000000042000f in __cmd_report (rep=0x7fff80cec580) at builtin-report.c:380
    > 1 cmd_report (argc=0, argv=<optimized out>, prefix=<optimized out>) at builtin-report.c:759
    > 2 0x0000000000414513 in run_builtin (p=0x7724a8, argc=3, argv=0x7fff80ceca70) at perf.c:273
    > 3 0x0000000000413d41 in handle_internal_command (argv=0x7fff80ceca70, argc=3) at perf.c:345
    > 4 run_argv (argv=0x7fff80cec880, argcp=0x7fff80cec88c) at perf.c:389
    > 5 main (argc=3, argv=0x7fff80ceca70) at perf.c:487
    >
    > kernel_map can be NULL, so need to handle it while dumping a warning
    > to user.
    >
    > Signed-off-by: David Ahern<dsahern@gmail.com>
    > ---
    > tools/perf/builtin-report.c | 17 ++++++++++++-----
    > 1 files changed, 12 insertions(+), 5 deletions(-)
    >
    > diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
    > index 2e31743..002c644 100644
    > --- a/tools/perf/builtin-report.c
    > +++ b/tools/perf/builtin-report.c
    > @@ -374,16 +374,23 @@ static int __cmd_report(struct perf_report *rep)
    > (kernel_map->dso->hit&&
    > (kernel_kmap->ref_reloc_sym == NULL ||
    > kernel_kmap->ref_reloc_sym->addr == 0))) {
    > - const struct dso *kdso = kernel_map->dso;
    > + const char *desc =
    > + "As no suitable kallsyms nor vmlinux was found, kernel samples\n"
    > + "can't be resolved.";
    > +
    > + if (kernel_map) {
    > + const struct dso *kdso = kernel_map->dso;
    > + if (RB_EMPTY_ROOT(&kdso->symbols[MAP__FUNCTION])) {
    > + desc = "If some relocation was applied (e.g. "
    > + "kexec) symbols may be misresolved.";
    > + }
    > + }
    >
    > ui__warning(
    > "Kernel address maps (/proc/{kallsyms,modules}) were restricted.\n\n"
    > "Check /proc/sys/kernel/kptr_restrict before running 'perf record'.\n\n%s\n\n"
    > "Samples in kernel modules can't be resolved as well.\n\n",
    > - RB_EMPTY_ROOT(&kdso->symbols[MAP__FUNCTION]) ?
    > -"As no suitable kallsyms nor vmlinux was found, kernel samples\n"
    > -"can't be resolved." :
    > -"If some relocation was applied (e.g. kexec) symbols may be misresolved.");
    > + desc);
    > }
    >
    > if (dump_trace) {



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