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>

1 files changed, 15 insertions, 15 deletions

diff --git a/arch/arm/mm/cache-v7.S b/arch/arm/mm/cache-v7.S
index 615c99e..b966656 100644
--- a/arch/arm/mm/cache-v7.S
+++ b/arch/arm/mm/cache-v7.S
@@ -61,7 +61,7 @@ ENTRY(v7_invalidate_l1)
        bgt     1b
        dsb     st
        isb
-       mov     pc, lr
+       ret     lr
 ENDPROC(v7_invalidate_l1)
 
 /*
@@ -76,7 +76,7 @@ ENTRY(v7_flush_icache_all)
 	mov	r0, #0
 	ALT_SMP(mcr	p15, 0, r0, c7, c1, 0)		@ invalidate I-cache inner shareable
 	ALT_UP(mcr	p15, 0, r0, c7, c5, 0)		@ I+BTB cache invalidate
-	mov	pc, lr
+	ret	lr
 ENDPROC(v7_flush_icache_all)
 
  /*
@@ -94,7 +94,7 @@ ENTRY(v7_flush_dcache_louis)
 	ALT_UP(ands	r3, r0, #(7 << 27))	@ extract LoUU from clidr
 #ifdef CONFIG_ARM_ERRATA_643719
 	ALT_SMP(mrceq	p15, 0, r2, c0, c0, 0)	@ read main ID register
-	ALT_UP(moveq	pc, lr)			@ LoUU is zero, so nothing to do
+	ALT_UP(reteq	lr)			@ LoUU is zero, so nothing to do
 	ldreq	r1, =0x410fc090                 @ ID of ARM Cortex A9 r0p?
 	biceq	r2, r2, #0x0000000f             @ clear minor revision number
 	teqeq	r2, r1                          @ test for errata affected core and if so...
@@ -102,7 +102,7 @@ ENTRY(v7_flush_dcache_louis)
 #endif
 	ALT_SMP(mov	r3, r3, lsr #20)	@ r3 = LoUIS * 2
 	ALT_UP(mov	r3, r3, lsr #26)	@ r3 = LoUU * 2
-	moveq	pc, lr				@ return if level == 0
+	reteq	lr				@ return if level == 0
 	mov	r10, #0				@ r10 (starting level) = 0
 	b	flush_levels			@ start flushing cache levels
 ENDPROC(v7_flush_dcache_louis)
@@ -168,7 +168,7 @@ finished:
 	mcr	p15, 2, r10, c0, c0, 0		@ select current cache level in cssr
 	dsb	st
 	isb
-	mov	pc, lr
+	ret	lr
 ENDPROC(v7_flush_dcache_all)
 
 /*
@@ -191,7 +191,7 @@ ENTRY(v7_flush_kern_cache_all)
 	ALT_UP(mcr	p15, 0, r0, c7, c5, 0)	@ I+BTB cache invalidate
  ARM(	ldmfd	sp!, {r4-r5, r7, r9-r11, lr}	)
  THUMB(	ldmfd	sp!, {r4-r7, r9-r11, lr}	)
-	mov	pc, lr
+	ret	lr
 ENDPROC(v7_flush_kern_cache_all)
 
  /*
@@ -209,7 +209,7 @@ ENTRY(v7_flush_kern_cache_louis)
 	ALT_UP(mcr	p15, 0, r0, c7, c5, 0)	@ I+BTB cache invalidate
  ARM(	ldmfd	sp!, {r4-r5, r7, r9-r11, lr}	)
  THUMB(	ldmfd	sp!, {r4-r7, r9-r11, lr}	)
-	mov	pc, lr
+	ret	lr
 ENDPROC(v7_flush_kern_cache_louis)
 
 /*
@@ -235,7 +235,7 @@ ENTRY(v7_flush_user_cache_all)
  *	- we have a VIPT cache.
  */
 ENTRY(v7_flush_user_cache_range)
-	mov	pc, lr
+	ret	lr
 ENDPROC(v7_flush_user_cache_all)
 ENDPROC(v7_flush_user_cache_range)
 
@@ -296,7 +296,7 @@ ENTRY(v7_coherent_user_range)
 	ALT_UP(mcr	p15, 0, r0, c7, c5, 6)	@ invalidate BTB
 	dsb	ishst
 	isb
-	mov	pc, lr
+	ret	lr
 
 /*
  * Fault handling for the cache operation above. If the virtual address in r0
@@ -307,7 +307,7 @@ ENTRY(v7_coherent_user_range)
 	dsb
 #endif
 	mov	r0, #-EFAULT
-	mov	pc, lr
+	ret	lr
  UNWIND(.fnend		)
 ENDPROC(v7_coherent_kern_range)
 ENDPROC(v7_coherent_user_range)
@@ -336,7 +336,7 @@ ENTRY(v7_flush_kern_dcache_area)
 	cmp	r0, r1
 	blo	1b
 	dsb	st
-	mov	pc, lr
+	ret	lr
 ENDPROC(v7_flush_kern_dcache_area)
 
 /*
@@ -369,7 +369,7 @@ v7_dma_inv_range:
 	cmp	r0, r1
 	blo	1b
 	dsb	st
-	mov	pc, lr
+	ret	lr
 ENDPROC(v7_dma_inv_range)
 
 /*
@@ -391,7 +391,7 @@ v7_dma_clean_range:
 	cmp	r0, r1
 	blo	1b
 	dsb	st
-	mov	pc, lr
+	ret	lr
 ENDPROC(v7_dma_clean_range)
 
 /*
@@ -413,7 +413,7 @@ ENTRY(v7_dma_flush_range)
 	cmp	r0, r1
 	blo	1b
 	dsb	st
-	mov	pc, lr
+	ret	lr
 ENDPROC(v7_dma_flush_range)
 
 /*
@@ -439,7 +439,7 @@ ENTRY(v7_dma_unmap_area)
 	add	r1, r1, r0
 	teq	r2, #DMA_TO_DEVICE
 	bne	v7_dma_inv_range
-	mov	pc, lr
+	ret	lr
 ENDPROC(v7_dma_unmap_area)
 
 	__INITDATA