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

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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: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Ard Biesheuvel 2020-09-14 11:48:20 +03:00
parent 91580f0dbf
commit 450abd38fe
3 changed files with 8 additions and 8 deletions
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4
arch/arm/include/asm/assembler.h
View file

@ -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

2
arch/arm/include/asm/processor.h
View file

@ -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

10
arch/arm/kernel/head.S
View file

@ -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)