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Subject[RFC PATCH] perf: workaround unaligned NEON vector load
Date
The mmap event buffer may end up in a location that violates the
alignment requirements for a NEON vector load, which GCC generates to
load consecutive values from the event structure. Fix this by copying
the event structure into a properly aligned buffer.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
tools/perf/util/machine.c | 29 ++++++++++++++++-------------
1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 143f7057d581..ab5500e85173 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1565,37 +1565,40 @@ static int machine__process_kernel_mmap_event(struct machine *machine,
}

int machine__process_mmap2_event(struct machine *machine,
- union perf_event *event,
+ union perf_event *event_in,
struct perf_sample *sample)
{
+ union perf_event event;
struct thread *thread;
struct map *map;
int ret = 0;

+ memcpy(&event, event_in, sizeof(union perf_event));
+
if (dump_trace)
- perf_event__fprintf_mmap2(event, stdout);
+ perf_event__fprintf_mmap2(&event, stdout);

if (sample->cpumode == PERF_RECORD_MISC_GUEST_KERNEL ||
sample->cpumode == PERF_RECORD_MISC_KERNEL) {
- ret = machine__process_kernel_mmap_event(machine, event);
+ ret = machine__process_kernel_mmap_event(machine, &event);
if (ret < 0)
goto out_problem;
return 0;
}

- thread = machine__findnew_thread(machine, event->mmap2.pid,
- event->mmap2.tid);
+ thread = machine__findnew_thread(machine, event.mmap2.pid,
+ event.mmap2.tid);
if (thread == NULL)
goto out_problem;

- map = map__new(machine, event->mmap2.start,
- event->mmap2.len, event->mmap2.pgoff,
- event->mmap2.maj,
- event->mmap2.min, event->mmap2.ino,
- event->mmap2.ino_generation,
- event->mmap2.prot,
- event->mmap2.flags,
- event->mmap2.filename, thread);
+ map = map__new(machine, event.mmap2.start,
+ event.mmap2.len, event.mmap2.pgoff,
+ event.mmap2.maj,
+ event.mmap2.min, event.mmap2.ino,
+ event.mmap2.ino_generation,
+ event.mmap2.prot,
+ event.mmap2.flags,
+ event.mmap2.filename, thread);

if (map == NULL)
goto out_problem_map;
--
2.20.1
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