Commit 717321fc authored by Marc Zyngier's avatar Marc Zyngier Committed by Catalin Marinas
Browse files

arm64: fix access to preempt_count from assembly code 



preempt_count is defined as an int. Oddly enough, we access it
as a 64bit value. Things become interesting when running a BE
kernel, and looking at the current CPU number, which is stored
as an int next to preempt_count. Like in a per-cpu interrupt
handler, for example...

Using a 32bit access fixes the issue for good.

Cc: Matthew Leach <matthew.leach@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 7ade67b5

arch/arm64/kernel/entry.S

+11 −11
Original line number Diff line number Diff line
@@ -311,14 +311,14 @@ el1_irq: 
#endif

#ifdef CONFIG_PREEMPT

	get_thread_info tsk

	ldr	x24, [tsk, #TI_PREEMPT]		// get preempt count

	add	x0, x24, #1			// increment it

	str	x0, [tsk, #TI_PREEMPT]

	ldr	w24, [tsk, #TI_PREEMPT]		// get preempt count

	add	w0, w24, #1			// increment it

	str	w0, [tsk, #TI_PREEMPT]

#endif

	irq_handler

#ifdef CONFIG_PREEMPT

	str	x24, [tsk, #TI_PREEMPT]		// restore preempt count

	cbnz	x24, 1f				// preempt count != 0

	str	w24, [tsk, #TI_PREEMPT]		// restore preempt count

	cbnz	w24, 1f				// preempt count != 0

	ldr	x0, [tsk, #TI_FLAGS]		// get flags

	tbz	x0, #TIF_NEED_RESCHED, 1f	// needs rescheduling?

	bl	el1_preempt
@@ -509,15 +509,15 @@ el0_irq_naked: 
#endif

	get_thread_info tsk

#ifdef CONFIG_PREEMPT

	ldr	x24, [tsk, #TI_PREEMPT]		// get preempt count

	add	x23, x24, #1			// increment it

	str	x23, [tsk, #TI_PREEMPT]

	ldr	w24, [tsk, #TI_PREEMPT]		// get preempt count

	add	w23, w24, #1			// increment it

	str	w23, [tsk, #TI_PREEMPT]

#endif

	irq_handler

#ifdef CONFIG_PREEMPT

	ldr	x0, [tsk, #TI_PREEMPT]

	str	x24, [tsk, #TI_PREEMPT]

	cmp	x0, x23

	ldr	w0, [tsk, #TI_PREEMPT]

	str	w24, [tsk, #TI_PREEMPT]

	cmp	w0, w23

	b.eq	1f

	mov	x1, #0

	str	x1, [x1]			// BUG

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