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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/mach-ep93xx
parentaf040ffc9ba1e079ee4c0748aff64fa3d4716fa5 (diff)
downloadop-kernel-dev-6ebbf2ce437b33022d30badd49dc94d33ecfa498.zip
op-kernel-dev-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-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/mach-ep93xx')
-rw-r--r--arch/arm/mach-ep93xx/crunch-bits.S6
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/arm/mach-ep93xx/crunch-bits.S b/arch/arm/mach-ep93xx/crunch-bits.S
index e96923a..ee0be2a 100644
--- a/arch/arm/mach-ep93xx/crunch-bits.S
+++ b/arch/arm/mach-ep93xx/crunch-bits.S
@@ -198,7 +198,7 @@ crunch_load:
get_thread_info r10
#endif
2: dec_preempt_count r10, r3
- mov pc, lr
+ ret lr
/*
* Back up crunch regs to save area and disable access to them
@@ -277,7 +277,7 @@ ENTRY(crunch_task_copy)
mov r3, lr @ preserve return address
bl crunch_save
msr cpsr_c, ip @ restore interrupt mode
- mov pc, r3
+ ret r3
/*
* Restore crunch state from given memory address
@@ -310,4 +310,4 @@ ENTRY(crunch_task_restore)
mov r3, lr @ preserve return address
bl crunch_load
msr cpsr_c, ip @ restore interrupt mode
- mov pc, r3
+ ret r3
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