perf_counter/powerpc: Check oprofile_cpu_type for NULL before using it

If the current CPU doesn't support performance counters,
cur_cpu_spec->oprofile_cpu_type can be NULL. The current
perf_counter modules don't test for that case and would thus
crash at boot time.

Bug reported by David Woodhouse.

Reported-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Paul Mackerras <paulus@samba.org>
LKML-Reference: <19066.48028.446975.501454@cargo.ozlabs.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/power6-pmu.c b/arch/powerpc/kernel/power6-pmu.c
index 09ae5bf5bda7..fa21890531da 100644
--- a/arch/powerpc/kernel/power6-pmu.c
+++ b/arch/powerpc/kernel/power6-pmu.c
@@ -537,7 +537,8 @@ static struct power_pmu power6_pmu = {
 
 static int init_power6_pmu(void)
 {
-        if (strcmp(cur_cpu_spec->oprofile_cpu_type, "ppc64/power6"))
+        if (!cur_cpu_spec->oprofile_cpu_type ||
+            strcmp(cur_cpu_spec->oprofile_cpu_type, "ppc64/power6"))
                 return -ENODEV;
 
         return register_power_pmu(&power6_pmu);