[PATCH 1/4] perf report: Fix crash showing warning related to kernel maps

From: Arnaldo Carvalho de Melo
Date: Fri Apr 20 2012 - 12:53:24 EST

From: David Ahern <dsahern@xxxxxxxxx>

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.

- fixed RB_EMPTY_ROOT check -- desc takes the altnerative output when RB_EMPTY_ROOT is false.

Signed-off-by: David Ahern <dsahern@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung.kim@xxxxxxx>
Link: http://lkml.kernel.org/r/1334544855-55021-1-git-send-email-dsahern@xxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
tools/perf/builtin-report.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 2e31743..cdae9b2 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.";
+ }
+ }

"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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