perf: arm_spe: Make wakeup range check overflow safe

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The current code checks whether the wakeup point is in the current
writable range by comparing it with handle->head + handle->size.

The perf AUX head is a monotonically increasing index, so that addition
can overflow when head is close to ULONG_MAX. In that case, a wakeup
point which is still inside the free space range can be missed.

Use unsigned subtraction to compare the distance from head to wakeup
against the handle->size. This can dismiss the issue when addition
overflow.

This is unlikely to happen in practice, but the change makes the
watermark check logically correct.

Fixes: d5d9696b03 ("drivers/perf: Add support for ARMv8.2 Statistical Profiling Extension")
Signed-off-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

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Leo Yan 2026-07-02 18:05:21 +01:00 • committed by Will Deacon

parent 49f2413f9b

commit fcc5eaea2d

1 changed files with 1 additions and 1 deletions

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drivers/perf/arm_spe_pmu.c

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