From: Will Deacon Date: Tue, 11 Dec 2018 13:41:32 +0000 (+0000) Subject: arm64: preempt: Fix big-endian when checking preempt count in assembly X-Git-Tag: for-linus-20190104~119^2~26 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=7faa313f05cad184e8b17750f0cbe5216ac6debb;p=linux-2.6-block.git arm64: preempt: Fix big-endian when checking preempt count in assembly Commit 396244692232 ("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 Reported-by: "kernelci.org bot" Tested-by: Kevin Hilman Signed-off-by: Will Deacon --- diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index ce985f13dce5..4feb6119c3c9 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -722,11 +722,9 @@ USER(\label, ic ivau, \tmp2) // invalidate I line PoU .macro if_will_cond_yield_neon #ifdef CONFIG_PREEMPT get_thread_info x0 - ldr w1, [x0, #TSK_TI_PREEMPT] - ldr x0, [x0, #TSK_TI_FLAGS] - cmp w1, #PREEMPT_DISABLE_OFFSET - csel x0, x0, xzr, eq - tbnz x0, #TIF_NEED_RESCHED, .Lyield_\@ // needs rescheduling? + ldr x0, [x0, #TSK_TI_PREEMPT] + sub x0, x0, #PREEMPT_DISABLE_OFFSET + cbz x0, .Lyield_\@ /* fall through to endif_yield_neon */ .subsection 1 .Lyield_\@ : diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index c7d050207e53..763f03dc4d9e 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -619,10 +619,8 @@ el1_irq: irq_handler #ifdef CONFIG_PREEMPT - ldr w24, [tsk, #TSK_TI_PREEMPT] // get preempt count - cbnz w24, 1f // preempt count != 0 - ldr x0, [tsk, #TSK_TI_FLAGS] // get flags - tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling? + ldr x24, [tsk, #TSK_TI_PREEMPT] // get preempt count + cbnz x24, 1f // preempt count != 0 bl el1_preempt 1: #endif