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>
diff --git a/arch/arm/mm/proc-arm946.S b/arch/arm/mm/proc-arm946.S
index 0289cd90..b3dd9b2 100644
--- a/arch/arm/mm/proc-arm946.S
+++ b/arch/arm/mm/proc-arm946.S
@@ -38,7 +38,7 @@
*/
ENTRY(cpu_arm946_proc_init)
ENTRY(cpu_arm946_switch_mm)
- mov pc, lr
+ ret lr
/*
* cpu_arm946_proc_fin()
@@ -48,7 +48,7 @@
bic r0, r0, #0x00001000 @ i-cache
bic r0, r0, #0x00000004 @ d-cache
mcr p15, 0, r0, c1, c0, 0 @ disable caches
- mov pc, lr
+ ret lr
/*
* cpu_arm946_reset(loc)
@@ -65,7 +65,7 @@
bic ip, ip, #0x00000005 @ .............c.p
bic ip, ip, #0x00001000 @ i-cache
mcr p15, 0, ip, c1, c0, 0 @ ctrl register
- mov pc, r0
+ ret r0
ENDPROC(cpu_arm946_reset)
.popsection
@@ -75,7 +75,7 @@
.align 5
ENTRY(cpu_arm946_do_idle)
mcr p15, 0, r0, c7, c0, 4 @ Wait for interrupt
- mov pc, lr
+ ret lr
/*
* flush_icache_all()
@@ -85,7 +85,7 @@
ENTRY(arm946_flush_icache_all)
mov r0, #0
mcr p15, 0, r0, c7, c5, 0 @ invalidate I cache
- mov pc, lr
+ ret lr
ENDPROC(arm946_flush_icache_all)
/*
@@ -117,7 +117,7 @@
tst r2, #VM_EXEC
mcrne p15, 0, ip, c7, c5, 0 @ flush I cache
mcrne p15, 0, ip, c7, c10, 4 @ drain WB
- mov pc, lr
+ ret lr
/*
* flush_user_cache_range(start, end, flags)
@@ -156,7 +156,7 @@
blo 1b
tst r2, #VM_EXEC
mcrne p15, 0, ip, c7, c10, 4 @ drain WB
- mov pc, lr
+ ret lr
/*
* coherent_kern_range(start, end)
@@ -191,7 +191,7 @@
blo 1b
mcr p15, 0, r0, c7, c10, 4 @ drain WB
mov r0, #0
- mov pc, lr
+ ret lr
/*
* flush_kern_dcache_area(void *addr, size_t size)
@@ -212,7 +212,7 @@
mov r0, #0
mcr p15, 0, r0, c7, c5, 0 @ invalidate I cache
mcr p15, 0, r0, c7, c10, 4 @ drain WB
- mov pc, lr
+ ret lr
/*
* dma_inv_range(start, end)
@@ -239,7 +239,7 @@
cmp r0, r1
blo 1b
mcr p15, 0, r0, c7, c10, 4 @ drain WB
- mov pc, lr
+ ret lr
/*
* dma_clean_range(start, end)
@@ -260,7 +260,7 @@
blo 1b
#endif
mcr p15, 0, r0, c7, c10, 4 @ drain WB
- mov pc, lr
+ ret lr
/*
* dma_flush_range(start, end)
@@ -284,7 +284,7 @@
cmp r0, r1
blo 1b
mcr p15, 0, r0, c7, c10, 4 @ drain WB
- mov pc, lr
+ ret lr
/*
* dma_map_area(start, size, dir)
@@ -307,7 +307,7 @@
* - dir - DMA direction
*/
ENTRY(arm946_dma_unmap_area)
- mov pc, lr
+ ret lr
ENDPROC(arm946_dma_unmap_area)
.globl arm946_flush_kern_cache_louis
@@ -324,7 +324,7 @@
bhi 1b
#endif
mcr p15, 0, r0, c7, c10, 4 @ drain WB
- mov pc, lr
+ ret lr
.type __arm946_setup, #function
__arm946_setup:
@@ -392,7 +392,7 @@
#ifdef CONFIG_CPU_CACHE_ROUND_ROBIN
orr r0, r0, #0x00004000 @ .1.. .... .... ....
#endif
- mov pc, lr
+ ret lr
.size __arm946_setup, . - __arm946_setup