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libperf mmap: In user mmap rdpmc avoid undefined behavior 

A shift left of a signed 64-bit s64 may overflow and result in
undefined behavior caught by ubsan. Switch to a u64 instead.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Ian Rogers 2025-09-14 11:24:37 -07:00 committed by Arnaldo Carvalho de Melo
parent de1111f91a
commit 8dc364fa48
1 changed files with 1 additions and 1 deletions
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2
tools/lib/perf/mmap.c
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@ -508,7 +508,7 @@ int perf_mmap__read_self(struct perf_mmap *map, struct perf_counts_values *count
idx = READ_ONCE(pc->index); idx = READ_ONCE(pc->index);
cnt = READ_ONCE(pc->offset); cnt = READ_ONCE(pc->offset);
if (pc->cap_user_rdpmc && idx) { if (pc->cap_user_rdpmc && idx) {
s64 evcnt = read_perf_counter(idx - 1); u64 evcnt = read_perf_counter(idx - 1);
u16 width = READ_ONCE(pc->pmc_width); u16 width = READ_ONCE(pc->pmc_width);
evcnt <<= 64 - width; evcnt <<= 64 - width;