diff options
| author | Russell King <[email protected]> | 2014-06-30 16:29:12 +0100 |
|---|---|---|
| committer | Russell King <[email protected]> | 2014-07-18 12:29:04 +0100 |
| commit | 6ebbf2ce437b33022d30badd49dc94d33ecfa498 (patch) | |
| tree | bc015e35b456a28bb0e501803a454dc0c0d3291a /arch/arm/kernel/relocate_kernel.S | |
| parent | af040ffc9ba1e079ee4c0748aff64fa3d4716fa5 (diff) | |
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 <[email protected]>
Tested-by: Stephen Warren <[email protected]> # Tegra Jetson TK1
Tested-by: Robert Jarzmik <[email protected]> # mioa701_bootresume.S
Tested-by: Andrew Lunn <[email protected]> # Kirkwood
Tested-by: Shawn Guo <[email protected]>
Tested-by: Tony Lindgren <[email protected]> # OMAPs
Tested-by: Gregory CLEMENT <[email protected]> # Armada XP, 375, 385
Acked-by: Sekhar Nori <[email protected]> # DaVinci
Acked-by: Christoffer Dall <[email protected]> # kvm/hyp
Acked-by: Haojian Zhuang <[email protected]> # PXA3xx
Acked-by: Stefano Stabellini <[email protected]> # Xen
Tested-by: Uwe Kleine-König <[email protected]> # ARMv7M
Tested-by: Simon Horman <[email protected]> # Shmobile
Signed-off-by: Russell King <[email protected]>
Diffstat (limited to 'arch/arm/kernel/relocate_kernel.S')
| -rw-r--r-- | arch/arm/kernel/relocate_kernel.S | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/arm/kernel/relocate_kernel.S b/arch/arm/kernel/relocate_kernel.S index 95858966d84e..35e72585ec1d 100644 --- a/arch/arm/kernel/relocate_kernel.S +++ b/arch/arm/kernel/relocate_kernel.S @@ -3,6 +3,7 @@ */ #include <linux/linkage.h> +#include <asm/assembler.h> #include <asm/kexec.h> .align 3 /* not needed for this code, but keeps fncpy() happy */ @@ -59,7 +60,7 @@ ENTRY(relocate_new_kernel) mov r0,#0 ldr r1,kexec_mach_type ldr r2,kexec_boot_atags - ARM( mov pc, lr ) + ARM( ret lr ) THUMB( bx lr ) .align |