ARM: head: use PC-relative insn sequence for __smp_alt

mainline inclusion
from mainline-5.11-rc1
commit 59d2f282
category: bugfix
bugzilla: 46882
CVE: NA

-------------------------------------------------
Now that calling __do_fixup_smp_on_up() can be done without passing
the physical-to-virtual offset in r3, we can replace the open coded
PC relative offset calculations with a pair of adr_l invocations. This
removes some open coded arithmetic involving virtual addresses, avoids
literal pools on v7+, and slightly reduces the footprint of the code.
Reviewed-by: NNicolas Pitre <nico@fluxnic.net>
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
(cherry picked from commit 59d2f282)
Signed-off-by: NZhao Hongjiang <zhaohongjiang@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

arch/arm/kernel/head.S

@@ -524,19 +524,11 @@ ARM_BE8(rev	r0, r0)			@ byteswap if big endian
 	retne	lr
 
 __fixup_smp_on_up:
-	adr	r0, 1f
-	ldmia	r0, {r3 - r5}
-	sub	r3, r0, r3
-	add	r4, r4, r3
-	add	r5, r5, r3
+	adr_l	r4, __smpalt_begin
+	adr_l	r5, __smpalt_end
 	b	__do_fixup_smp_on_up
 ENDPROC(__fixup_smp)
 
-	.align
-1:	.word	.
-	.word	__smpalt_begin
-	.word	__smpalt_end
-
 	.pushsection .data
 	.align	2
 	.globl	smp_on_up