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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/entry-armv.S
parentaf040ffc9ba1e079ee4c0748aff64fa3d4716fa5 (diff)
downloadlinux-linaro-stable-6ebbf2ce437b33022d30badd49dc94d33ecfa498.tar.gz
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-K├Ânig <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/entry-armv.S')
-rw-r--r--arch/arm/kernel/entry-armv.S42
1 files changed, 21 insertions, 21 deletions
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 52a949a8077d..36276cdccfbc 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -224,7 +224,7 @@ svc_preempt:
1: bl preempt_schedule_irq @ irq en/disable is done inside
ldr r0, [tsk, #TI_FLAGS] @ get new tasks TI_FLAGS
tst r0, #_TIF_NEED_RESCHED
- moveq pc, r8 @ go again
+ reteq r8 @ go again
b 1b
#endif
@@ -490,7 +490,7 @@ ENDPROC(__und_usr)
.pushsection .fixup, "ax"
.align 2
4: str r4, [sp, #S_PC] @ retry current instruction
- mov pc, r9
+ ret r9
.popsection
.pushsection __ex_table,"a"
.long 1b, 4b
@@ -552,7 +552,7 @@ call_fpe:
#endif
tst r0, #0x08000000 @ only CDP/CPRT/LDC/STC have bit 27
tstne r0, #0x04000000 @ bit 26 set on both ARM and Thumb-2
- moveq pc, lr
+ reteq lr
and r8, r0, #0x00000f00 @ mask out CP number
THUMB( lsr r8, r8, #8 )
mov r7, #1
@@ -571,33 +571,33 @@ call_fpe:
THUMB( add pc, r8 )
nop
- movw_pc lr @ CP#0
+ ret.w lr @ CP#0
W(b) do_fpe @ CP#1 (FPE)
W(b) do_fpe @ CP#2 (FPE)
- movw_pc lr @ CP#3
+ ret.w lr @ CP#3
#ifdef CONFIG_CRUNCH
b crunch_task_enable @ CP#4 (MaverickCrunch)
b crunch_task_enable @ CP#5 (MaverickCrunch)
b crunch_task_enable @ CP#6 (MaverickCrunch)
#else
- movw_pc lr @ CP#4
- movw_pc lr @ CP#5
- movw_pc lr @ CP#6
+ ret.w lr @ CP#4
+ ret.w lr @ CP#5
+ ret.w lr @ CP#6
#endif
- movw_pc lr @ CP#7
- movw_pc lr @ CP#8
- movw_pc lr @ CP#9
+ ret.w lr @ CP#7
+ ret.w lr @ CP#8
+ ret.w lr @ CP#9
#ifdef CONFIG_VFP
W(b) do_vfp @ CP#10 (VFP)
W(b) do_vfp @ CP#11 (VFP)
#else
- movw_pc lr @ CP#10 (VFP)
- movw_pc lr @ CP#11 (VFP)
+ ret.w lr @ CP#10 (VFP)
+ ret.w lr @ CP#11 (VFP)
#endif
- movw_pc lr @ CP#12
- movw_pc lr @ CP#13
- movw_pc lr @ CP#14 (Debug)
- movw_pc lr @ CP#15 (Control)
+ ret.w lr @ CP#12
+ ret.w lr @ CP#13
+ ret.w lr @ CP#14 (Debug)
+ ret.w lr @ CP#15 (Control)
#ifdef NEED_CPU_ARCHITECTURE
.align 2
@@ -649,7 +649,7 @@ ENTRY(fp_enter)
.popsection
ENTRY(no_fp)
- mov pc, lr
+ ret lr
ENDPROC(no_fp)
__und_usr_fault_32:
@@ -745,7 +745,7 @@ ENDPROC(__switch_to)
#ifdef CONFIG_ARM_THUMB
bx \reg
#else
- mov pc, \reg
+ ret \reg
#endif
.endm
@@ -837,7 +837,7 @@ kuser_cmpxchg64_fixup:
#if __LINUX_ARM_ARCH__ < 6
bcc kuser_cmpxchg32_fixup
#endif
- mov pc, lr
+ ret lr
.previous
#else
@@ -905,7 +905,7 @@ kuser_cmpxchg32_fixup:
subs r8, r4, r7
rsbcss r8, r8, #(2b - 1b)
strcs r7, [sp, #S_PC]
- mov pc, lr
+ ret lr
.previous
#else