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| author | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-06-30 16:29:12 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-07-18 12:29:04 +0100 |
| commit | 6ebbf2ce437b33022d30badd49dc94d33ecfa498 (patch) | |
| tree | bc015e35b456a28bb0e501803a454dc0c0d3291a /arch/arm/kernel/entry-common.S | |
| parent | af040ffc9ba1e079ee4c0748aff64fa3d4716fa5 (diff) | |
| download | lwn-6ebbf2ce437b33022d30badd49dc94d33ecfa498.tar.gz lwn-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/kernel/entry-common.S')
| -rw-r--r-- | arch/arm/kernel/entry-common.S | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index 7139d4a7dea7..e52fe5a2d843 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -8,6 +8,7 @@ * published by the Free Software Foundation. */ +#include <asm/assembler.h> #include <asm/unistd.h> #include <asm/ftrace.h> #include <asm/unwind.h> @@ -88,7 +89,7 @@ ENTRY(ret_from_fork) cmp r5, #0 movne r0, r4 adrne lr, BSYM(1f) - movne pc, r5 + retne r5 1: get_thread_info tsk b ret_slow_syscall ENDPROC(ret_from_fork) @@ -290,7 +291,7 @@ ENDPROC(ftrace_graph_caller_old) .macro mcount_exit ldmia sp!, {r0-r3, ip, lr} - mov pc, ip + ret ip .endm ENTRY(__gnu_mcount_nc) @@ -298,7 +299,7 @@ UNWIND(.fnstart) #ifdef CONFIG_DYNAMIC_FTRACE mov ip, lr ldmia sp!, {lr} - mov pc, ip + ret ip #else __mcount #endif @@ -333,12 +334,12 @@ return_to_handler: bl ftrace_return_to_handler mov lr, r0 @ r0 has real ret addr ldmia sp!, {r0-r3} - mov pc, lr + ret lr #endif ENTRY(ftrace_stub) .Lftrace_stub: - mov pc, lr + ret lr ENDPROC(ftrace_stub) #endif /* CONFIG_FUNCTION_TRACER */ @@ -561,7 +562,7 @@ sys_mmap2: streq r5, [sp, #4] beq sys_mmap_pgoff mov r0, #-EINVAL - mov pc, lr + ret lr #else str r5, [sp, #4] b sys_mmap_pgoff |