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author | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-06-30 16:29:12 +0100 |
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committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-07-18 12:29:04 +0100 |
commit | 6ebbf2ce437b33022d30badd49dc94d33ecfa498 (patch) | |
tree | bc015e35b456a28bb0e501803a454dc0c0d3291a /arch/arm/kernel/head-nommu.S | |
parent | af040ffc9ba1e079ee4c0748aff64fa3d4716fa5 (diff) | |
download | linux-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/kernel/head-nommu.S')
-rw-r--r-- | arch/arm/kernel/head-nommu.S | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S index 716249cc2ee1..cc176b67c134 100644 --- a/arch/arm/kernel/head-nommu.S +++ b/arch/arm/kernel/head-nommu.S @@ -82,7 +82,7 @@ ENTRY(stext) adr lr, BSYM(1f) @ return (PIC) address ARM( add pc, r10, #PROCINFO_INITFUNC ) THUMB( add r12, r10, #PROCINFO_INITFUNC ) - THUMB( mov pc, r12 ) + THUMB( ret r12 ) 1: b __after_proc_init ENDPROC(stext) @@ -119,7 +119,7 @@ ENTRY(secondary_startup) mov r13, r12 @ __secondary_switched address ARM( add pc, r10, #PROCINFO_INITFUNC ) THUMB( add r12, r10, #PROCINFO_INITFUNC ) - THUMB( mov pc, r12 ) + THUMB( ret r12 ) ENDPROC(secondary_startup) ENTRY(__secondary_switched) @@ -164,7 +164,7 @@ __after_proc_init: #endif mcr p15, 0, r0, c1, c0, 0 @ write control reg #endif /* CONFIG_CPU_CP15 */ - mov pc, r13 + ret r13 ENDPROC(__after_proc_init) .ltorg @@ -254,7 +254,7 @@ ENTRY(__setup_mpu) orr r0, r0, #CR_M @ Set SCTRL.M (MPU on) mcr p15, 0, r0, c1, c0, 0 @ Enable MPU isb - mov pc,lr + ret lr ENDPROC(__setup_mpu) #endif #include "head-common.S" |