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powerpc/perf: Fix crashes with generic_compat_pmu & BHRB 

The bhrb_filter_map ("The Branch History Rolling Buffer") callback is
only defined in raw CPUs' power_pmu structs. The "architected" CPUs
use generic_compat_pmu, which does not have this callback, and crashes
occur if a user tries to enable branch stack for an event.

This add a NULL pointer check for bhrb_filter_map() which behaves as
if the callback returned an error.

This does not add the same check for config_bhrb() as the only caller
checks for cpuhw->bhrb_users which remains zero if bhrb_filter_map==0.

Fixes: be80e758d0 ("powerpc/perf: Add generic compat mode pmu driver")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200602025612.62707-1-aik@ozlabs.ru
This commit is contained in:
Alexey Kardashevskiy 2020-06-02 12:56:12 +10:00 committed by Michael Ellerman
parent b91eb51824
commit b460b51241
1 changed files with 14 additions and 5 deletions
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19
arch/powerpc/perf/core-book3s.c
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@ -1557,9 +1557,16 @@ static int power_pmu_add(struct perf_event *event, int ef_flags)
ret = 0;
out:
if (has_branch_stack(event)) {
power_pmu_bhrb_enable(event);
cpuhw->bhrb_filter = ppmu->bhrb_filter_map(
event->attr.branch_sample_type);
u64 bhrb_filter = -1;
if (ppmu->bhrb_filter_map)
bhrb_filter = ppmu->bhrb_filter_map(
event->attr.branch_sample_type);
if (bhrb_filter != -1) {
cpuhw->bhrb_filter = bhrb_filter;
power_pmu_bhrb_enable(event);
}
}
perf_pmu_enable(event->pmu);
@ -1881,7 +1888,6 @@ static int power_pmu_event_init(struct perf_event *event)
int n;
int err;
struct cpu_hw_events *cpuhw;
u64 bhrb_filter;
if (!ppmu)
return -ENOENT;
@ -1987,7 +1993,10 @@ static int power_pmu_event_init(struct perf_event *event)
err = power_check_constraints(cpuhw, events, cflags, n + 1);
if (has_branch_stack(event)) {
bhrb_filter = ppmu->bhrb_filter_map(
u64 bhrb_filter = -1;
if (ppmu->bhrb_filter_map)
bhrb_filter = ppmu->bhrb_filter_map(
event->attr.branch_sample_type);
if (bhrb_filter == -1) {