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Commit a18f3645 authored by Daniel Thompson's avatar Daniel Thompson Committed by Russell King
Browse files

ARM: 8266/1: Remove early stack deallocation from restore_user_regs 



Currently restore_user_regs deallocates the SVC stack early in
its execution and relies on no exception being taken between
the deallocation and the registers being restored. The introduction
of a default FIQ handler that also uses the SVC stack breaks this
assumption and can result in corrupted register state.

This patch works around the problem by removing the early
stack deallocation and using r2 as a temporary instead. I have
not found a way to do this without introducing an extra mov
instruction to the macro.

Signed-off-by: default avatarDaniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 1e347922

arch/arm/kernel/entry-header.S

+7 −6
Original line number Diff line number Diff line
@@ -253,21 +253,22 @@ 
	.endm



	.macro	restore_user_regs, fast = 0, offset = 0

	ldr	r1, [sp, #\offset + S_PSR]	@ get calling cpsr

	ldr	lr, [sp, #\offset + S_PC]!	@ get pc

	mov	r2, sp

	ldr	r1, [r2, #\offset + S_PSR]	@ get calling cpsr

	ldr	lr, [r2, #\offset + S_PC]!	@ get pc

	msr	spsr_cxsf, r1			@ save in spsr_svc

#if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_32v6K)

	@ We must avoid clrex due to Cortex-A15 erratum #830321

	strex	r1, r2, [sp]			@ clear the exclusive monitor

	strex	r1, r2, [r2]			@ clear the exclusive monitor

#endif

	.if	\fast

	ldmdb	sp, {r1 - lr}^			@ get calling r1 - lr

	ldmdb	r2, {r1 - lr}^			@ get calling r1 - lr

	.else

	ldmdb	sp, {r0 - lr}^			@ get calling r0 - lr

	ldmdb	r2, {r0 - lr}^			@ get calling r0 - lr

	.endif

	mov	r0, r0				@ ARMv5T and earlier require a nop

						@ after ldm {}^

	add	sp, sp, #S_FRAME_SIZE - S_PC

	add	sp, sp, #\offset + S_FRAME_SIZE

	movs	pc, lr				@ return & move spsr_svc into cpsr

	.endm