diff options
| author | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-06-30 17:29:12 +0200 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-07-18 13:29:04 +0200 |
| commit | 6ebbf2ce437b33022d30badd49dc94d33ecfa498 (patch) | |
| tree | bc015e35b456a28bb0e501803a454dc0c0d3291a /arch/arm/include | |
| parent | ARM: make it easier to check the CPU part number correctly (diff) | |
| download | linux-6ebbf2ce437b33022d30badd49dc94d33ecfa498.tar.xz linux-6ebbf2ce437b33022d30badd49dc94d33ecfa498.zip | |
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/include')
| -rw-r--r-- | arch/arm/include/asm/assembler.h | 21 | ||||
| -rw-r--r-- | arch/arm/include/asm/entry-macro-multi.S | 2 |
2 files changed, 22 insertions, 1 deletions
diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h index 906703a5b564..f67fd3afebdf 100644 --- a/arch/arm/include/asm/assembler.h +++ b/arch/arm/include/asm/assembler.h @@ -427,4 +427,25 @@ THUMB( orr \reg , \reg , #PSR_T_BIT ) #endif .endm + .irp c,,eq,ne,cs,cc,mi,pl,vs,vc,hi,ls,ge,lt,gt,le,hs,lo + .macro ret\c, reg +#if __LINUX_ARM_ARCH__ < 6 + mov\c pc, \reg +#else + .ifeqs "\reg", "lr" + bx\c \reg + .else + mov\c pc, \reg + .endif +#endif + .endm + .endr + + .macro ret.w, reg + ret \reg +#ifdef CONFIG_THUMB2_KERNEL + nop +#endif + .endm + #endif /* __ASM_ASSEMBLER_H__ */ diff --git a/arch/arm/include/asm/entry-macro-multi.S b/arch/arm/include/asm/entry-macro-multi.S index 88d61815f0c0..469a2b30fa27 100644 --- a/arch/arm/include/asm/entry-macro-multi.S +++ b/arch/arm/include/asm/entry-macro-multi.S @@ -35,5 +35,5 @@ \symbol_name: mov r8, lr arch_irq_handler_default - mov pc, r8 + ret r8 .endm |