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arm64: preempt: Fix big-endian when checking preempt count in assembly
[ Upstream commit7faa313f05
] Commit3962446922
("arm64: preempt: Provide our own implementation of asm/preempt.h") extended the preempt count field in struct thread_info to 64 bits, so that it consists of a 32-bit count plus a 32-bit flag indicating whether or not the current task needs rescheduling. Whilst the asm-offsets definition of TSK_TI_PREEMPT was updated to point to this new field, the assembly usage was left untouched meaning that a 32-bit load from TSK_TI_PREEMPT on a big-endian machine actually returns the reschedule flag instead of the count. Whilst we could fix this by pointing TSK_TI_PREEMPT at the count field, we're actually better off reworking the two assembly users so that they operate on the whole 64-bit value in favour of inspecting the thread flags separately in order to determine whether a reschedule is needed. Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reported-by: "kernelci.org bot" <bot@kernelci.org> Tested-by: Kevin Hilman <khilman@baylibre.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
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2 changed files with 5 additions and 9 deletions
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@ -683,11 +683,9 @@ USER(\label, ic ivau, \tmp2) // invalidate I line PoU
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.macro if_will_cond_yield_neon
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#ifdef CONFIG_PREEMPT
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get_thread_info x0
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ldr w1, [x0, #TSK_TI_PREEMPT]
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ldr x0, [x0, #TSK_TI_FLAGS]
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cmp w1, #PREEMPT_DISABLE_OFFSET
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csel x0, x0, xzr, eq
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tbnz x0, #TIF_NEED_RESCHED, .Lyield_\@ // needs rescheduling?
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ldr x0, [x0, #TSK_TI_PREEMPT]
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sub x0, x0, #PREEMPT_DISABLE_OFFSET
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cbz x0, .Lyield_\@
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/* fall through to endif_yield_neon */
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.subsection 1
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.Lyield_\@ :
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@ -622,10 +622,8 @@ el1_irq:
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irq_handler
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#ifdef CONFIG_PREEMPT
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ldr w24, [tsk, #TSK_TI_PREEMPT] // get preempt count
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cbnz w24, 1f // preempt count != 0
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ldr x0, [tsk, #TSK_TI_FLAGS] // get flags
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tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling?
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ldr x24, [tsk, #TSK_TI_PREEMPT] // get preempt count
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cbnz x24, 1f // preempt count != 0
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bl el1_preempt
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1:
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#endif
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