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ARM: 6504/1: Thumb-2: Fix long-distance conditional branches in head.S for Thumb-2.

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The 32-bit conditional branches in Thumb-2 have a shorter range
(+/-512K) than their ARM counterparts (+/-32MB).  The linker does
not currently generate trampolines to extend the range of these
Thumb-2 conditional branches, resulting in link errors when vmlinux
is sufficiently large, e.g.:

head.o:(.text+0x464): relocation truncated to fit: R_ARM_THM_JUMP19

This patch forces the longer-range, unconditional branch encoding
by use of an explicit IT instruction.  The resulting branches are
triggered on the same conditions as before.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Dave Martin 2010-11-29 19:43:28 +01:00 committed by Russell King
parent 26e5ca93dd
commit a75e5248c5
1 changed files with 3 additions and 0 deletions
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3
arch/arm/kernel/head.S
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@ -85,9 +85,11 @@ ENTRY(stext)
mrc p15, 0, r9, c0, c0 @ get processor id
bl __lookup_processor_type @ r5=procinfo r9=cpuid
movs r10, r5 @ invalid processor (r5=0)?
THUMB( it eq ) @ force fixup-able long branch encoding
beq __error_p @ yes, error 'p'
bl __lookup_machine_type @ r5=machinfo
movs r8, r5 @ invalid machine (r5=0)?
THUMB( it eq ) @ force fixup-able long branch encoding
beq __error_a @ yes, error 'a'
bl __vet_atags
#ifdef CONFIG_SMP_ON_UP
@ -283,6 +285,7 @@ ENTRY(secondary_startup)
bl __lookup_processor_type
movs r10, r5 @ invalid processor?
moveq r0, #'p' @ yes, error 'p'
THUMB( it eq ) @ force fixup-able long branch encoding
beq __error_p
/*