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authorRussell King <rmk+kernel@arm.linux.org.uk>2014-06-30 16:29:12 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2014-07-18 12:29:04 +0100
commit6ebbf2ce437b33022d30badd49dc94d33ecfa498 (patch)
treebc015e35b456a28bb0e501803a454dc0c0d3291a /arch/arm/kernel/head.S
parentaf040ffc9ba1e079ee4c0748aff64fa3d4716fa5 (diff)
downloadlinux-6ebbf2ce437b33022d30badd49dc94d33ecfa498.tar.bz2
ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+
ARMv6 and greater introduced a new instruction ("bx") which can be used to return from function calls. Recent CPUs perform better when the "bx lr" instruction is used rather than the "mov pc, lr" instruction, and this sequence is strongly recommended to be used by the ARM architecture manual (section A.4.1.1). We provide a new macro "ret" with all its variants for the condition code which will resolve to the appropriate instruction. Rather than doing this piecemeal, and miss some instances, change all the "mov pc" instances to use the new macro, with the exception of the "movs" instruction and the kprobes code. This allows us to detect the "mov pc, lr" case and fix it up - and also gives us the possibility of deploying this for other registers depending on the CPU selection. Reported-by: Will Deacon <will.deacon@arm.com> Tested-by: Stephen Warren <swarren@nvidia.com> # Tegra Jetson TK1 Tested-by: Robert Jarzmik <robert.jarzmik@free.fr> # mioa701_bootresume.S Tested-by: Andrew Lunn <andrew@lunn.ch> # Kirkwood Tested-by: Shawn Guo <shawn.guo@freescale.com> Tested-by: Tony Lindgren <tony@atomide.com> # OMAPs Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com> # Armada XP, 375, 385 Acked-by: Sekhar Nori <nsekhar@ti.com> # DaVinci Acked-by: Christoffer Dall <christoffer.dall@linaro.org> # kvm/hyp Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com> # PXA3xx Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> # Xen Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> # ARMv7M Tested-by: Simon Horman <horms+renesas@verge.net.au> # Shmobile Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/head.S')
-rw-r--r--arch/arm/kernel/head.S18
1 files changed, 9 insertions, 9 deletions
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 2c35f0ff2fdc..664eee8c4a26 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -140,7 +140,7 @@ ENTRY(stext)
mov r8, r4 @ set TTBR1 to swapper_pg_dir
ARM( add pc, r10, #PROCINFO_INITFUNC )
THUMB( add r12, r10, #PROCINFO_INITFUNC )
- THUMB( mov pc, r12 )
+ THUMB( ret r12 )
1: b __enable_mmu
ENDPROC(stext)
.ltorg
@@ -335,7 +335,7 @@ __create_page_tables:
sub r4, r4, #0x1000 @ point to the PGD table
mov r4, r4, lsr #ARCH_PGD_SHIFT
#endif
- mov pc, lr
+ ret lr
ENDPROC(__create_page_tables)
.ltorg
.align
@@ -383,7 +383,7 @@ ENTRY(secondary_startup)
ARM( add pc, r10, #PROCINFO_INITFUNC ) @ initialise processor
@ (return control reg)
THUMB( add r12, r10, #PROCINFO_INITFUNC )
- THUMB( mov pc, r12 )
+ THUMB( ret r12 )
ENDPROC(secondary_startup)
/*
@@ -468,7 +468,7 @@ ENTRY(__turn_mmu_on)
instr_sync
mov r3, r3
mov r3, r13
- mov pc, r3
+ ret r3
__turn_mmu_on_end:
ENDPROC(__turn_mmu_on)
.popsection
@@ -487,7 +487,7 @@ __fixup_smp:
orr r4, r4, #0x0000b000
orr r4, r4, #0x00000020 @ val 0x4100b020
teq r3, r4 @ ARM 11MPCore?
- moveq pc, lr @ yes, assume SMP
+ reteq lr @ yes, assume SMP
mrc p15, 0, r0, c0, c0, 5 @ read MPIDR
and r0, r0, #0xc0000000 @ multiprocessing extensions and
@@ -500,7 +500,7 @@ __fixup_smp:
orr r4, r4, #0x0000c000
orr r4, r4, #0x00000090
teq r3, r4 @ Check for ARM Cortex-A9
- movne pc, lr @ Not ARM Cortex-A9,
+ retne lr @ Not ARM Cortex-A9,
@ If a future SoC *does* use 0x0 as the PERIPH_BASE, then the
@ below address check will need to be #ifdef'd or equivalent
@@ -512,7 +512,7 @@ __fixup_smp:
ARM_BE8(rev r0, r0) @ byteswap if big endian
and r0, r0, #0x3 @ number of CPUs
teq r0, #0x0 @ is 1?
- movne pc, lr
+ retne lr
__fixup_smp_on_up:
adr r0, 1f
@@ -539,7 +539,7 @@ smp_on_up:
.text
__do_fixup_smp_on_up:
cmp r4, r5
- movhs pc, lr
+ reths lr
ldmia r4!, {r0, r6}
ARM( str r6, [r0, r3] )
THUMB( add r0, r0, r3 )
@@ -672,7 +672,7 @@ ARM_BE8(rev16 ip, ip)
2: cmp r4, r5
ldrcc r7, [r4], #4 @ use branch for delay slot
bcc 1b
- mov pc, lr
+ ret lr
#endif
ENDPROC(__fixup_a_pv_table)