Commit 450abd38 authored by Ard Biesheuvel's avatar Ard Biesheuvel
Browse files

ARM: kernel: use relative references for UP/SMP alternatives 



Currently, the .alt.smp.init section contains the virtual addresses
of the patch sites. Since patching may occur both before and after
switching into virtual mode, this requires some manual handling of
the address when applying the UP alternative.

Let's simplify this by using relative offsets in the table entries:
this allows us to simply add each entry's address to its contents,
regardless of whether we are running in virtual mode or not.

Reviewed-by: default avatarNicolas Pitre <nico@fluxnic.net>
Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
parent 91580f0d

arch/arm/include/asm/assembler.h

+2 −2
Original line number Diff line number Diff line
@@ -259,7 +259,7 @@ 
 */

#define ALT_UP(instr...)					\

	.pushsection ".alt.smp.init", "a"			;\

	.long	9998b						;\

	.long	9998b - .					;\

9997:	instr							;\

	.if . - 9997b == 2					;\

		nop						;\
@@ -270,7 +270,7 @@ 
	.popsection

#define ALT_UP_B(label)					\

	.pushsection ".alt.smp.init", "a"			;\

	.long	9998b						;\

	.long	9998b - .					;\

	W(b)	. + (label - 9998b)					;\

	.popsection

#else

arch/arm/include/asm/processor.h

+1 −1
Original line number Diff line number Diff line
@@ -96,7 +96,7 @@ unsigned long get_wchan(struct task_struct *p); 
#define __ALT_SMP_ASM(smp, up)						\

	"9998:	" smp "\n"						\

	"	.pushsection \".alt.smp.init\", \"a\"\n"		\

	"	.long	9998b\n"					\

	"	.long	9998b - .\n"					\

	"	" up "\n"						\

	"	.popsection\n"

#else

arch/arm/kernel/head.S

+5 −5
Original line number Diff line number Diff line
@@ -546,14 +546,15 @@ smp_on_up: 
__do_fixup_smp_on_up:

	cmp	r4, r5

	reths	lr

	ldmia	r4!, {r0, r6}

 ARM(	str	r6, [r0, r3]	)

 THUMB(	add	r0, r0, r3	)

	ldmia	r4, {r0, r6}

 ARM(	str	r6, [r0, r4]	)

 THUMB(	add	r0, r0, r4	)

	add	r4, r4, #8

#ifdef __ARMEB__

 THUMB(	mov	r6, r6, ror #16	)	@ Convert word order for big-endian.

#endif

 THUMB(	strh	r6, [r0], #2	)	@ For Thumb-2, store as two halfwords

 THUMB(	mov	r6, r6, lsr #16	)	@ to be robust against misaligned r3.

 THUMB(	mov	r6, r6, lsr #16	)	@ to be robust against misaligned r0.

 THUMB(	strh	r6, [r0]	)

	b	__do_fixup_smp_on_up

ENDPROC(__do_fixup_smp_on_up)
@@ -562,7 +563,6 @@ ENTRY(fixup_smp) 
	stmfd	sp!, {r4 - r6, lr}

	mov	r4, r0

	add	r5, r0, r1

	mov	r3, #0

	bl	__do_fixup_smp_on_up

	ldmfd	sp!, {r4 - r6, pc}

ENDPROC(fixup_smp)

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