Commit dbd1b2da authored Jun 30, 2014 by Russell King Committed by Samuel Pascua Feb 27, 2018

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>

Backported from Linux 3.17 to Linux 3.4.

Following commands were used :

find arch/arm -name '*.S' -exec sed -i -e 's/mov pc, /ret /g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/moveq pc, /reteq /g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movne pc, /retne /g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movhs pc, /reths /g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movls pc, /retls /g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movlo pc, /retlo /g' {} \;

find arch/arm -name '*.S' -exec sed -i -e 's/mov\tpc, /ret\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/moveq\tpc, /reteq\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movne\tpc, /retne\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movhs\tpc, /reths\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movls\tpc, /retls\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movlo\tpc, /retlo\t/g' {} \;

find arch/arm -name '*.S' -exec sed -i -e 's/mov\tpc,/ret\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/moveq\tpc,/reteq\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movw_pc/ret.w/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movne\tpc,/retne\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movhs\tpc,/reths\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movls\tpc,/retls\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movlo\tpc,/retlo\t/g' {} \;

find arch/arm -name '*.S' -exec sed -i -e 's/mov\t\tpc, /ret\t\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/moveq\t\tpc, /reteq\t\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movne\t\tpc, /retne\t\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movhs\t\tpc, /reths\t\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movls\t\tpc, /retls\t\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movlo\t\tpc, /retlo\t\t/g' {} \;

find arch/arm -name '*.S' -exec sed -i -e 's/mov\t\tpc,/ret\t\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/moveq\t\tpc,/reteq\t\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movne\t\tpc,/retne\t\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movhs\t\tpc,/reths\t\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movls\t\tpc,/retls\t\t/g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movlo\t\tpc,/retlo\t\t/g' {} \;

find arch/arm -name '*.S' -exec sed -i -e 's/mov pc,/ret /g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/moveq pc,/reteq /g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movne pc,/retne /g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movhs pc,/reths /g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movls pc,/retls /g' {} \;
find arch/arm -name '*.S' -exec sed -i -e 's/movlo pc,/retlo /g' {} \;

git checkout -- arch/arm/mm/proc-v7-2level.S arch/arm/boot/compressed/head.S
sed -i -e 's/mov pc, /bx /g' arch/arm/mm/proc-v7-2level.S
sed -i -e 's/mov pc, /bx /g' arch/arm/mm/proc-v7-2level.S
sed -i -e 's/mov\tpc, /bx\t/g' arch/arm/mm/proc-v7-2level.S
sed -i -e 's/mov\tpc,/bx\t/g' arch/arm/mm/proc-v7-2level.S
sed -i -e 's/mov\t\tpc, /bx\t\t/g' arch/arm/mm/proc-v7-2level.S
sed -i -e 's/mov\t\tpc,/bx\t\t/g' arch/arm/mm/proc-v7-2level.S
sed -i -e 's/mov pc,/bx /g' arch/arm/mm/proc-v7-2level.S

EOF

- Patch arch/arm/include/asm/assembler.h
- Patch arch/arm/kernel/entry-header.S
- Add '#include <asm/assembler.h>' to missing files.
- Manually patch 'arch/arm/mm/proc-v7.S' to add bx

Signed-off-by: arter97 <qkrwngud825@gmail.com>
Signed-off-by: Samuel Pascua <pascua.samuel.14@gmail.com>

parent 957d4110

arch/arm/boot/bootp/init.S

+1 −1

Original line number	Diff line number	Diff line
		@@ -69,7 +69,7 @@ move: ldmia r4!, {r7 - r10} @ move 32-bytes at a time
		stmia r5!, {r7 - r10}
		subs r6, r6, #8 * 4
		bcs move
		mov pc, lr
		ret lr

		.size _start, . - _start

arch/arm/boot/compressed/head-shark.S

+2 −2

Original line number	Diff line number	Diff line
		@@ -61,7 +61,7 @@ __beginning: mov r4, r0 @ save the entry to the firmware
		bic r3, r3, #0x1 @ MMU
		mcr p15, 0, r3, c1, c0 @ disabled

		mov pc, r2
		ret r2

		__copy_target: .long 0x08507FFC
		__copy_end: .long 0x08607FFC
		@@ -126,7 +126,7 @@ __Copy: ldr r2, [r0], #-4
		ldr r0, __copy_target @ and add 0850 8000 instead
		add r0, r0, #4
		add r2, r2, r0
		mov pc, r2 @ and jump there
		ret r2 @ and jump there

		__go_on:
		adr sp, __temp_stack

arch/arm/boot/compressed/head-sharpsl.S

+1 −1

Original line number	Diff line number	Diff line
		@@ -145,6 +145,6 @@ get_flash_ids:
		beq .fids1
		ldrb r2, [r1, #20] @ NAND Manufacturer ID
		ldrb r3, [r1, #20] @ NAND Chip ID
		mov pc, lr
		ret lr

		.SHARPEND:

arch/arm/include/asm/assembler.h

+21 −0

Original line number	Diff line number	Diff line
		@@ -315,4 +315,25 @@
		#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__ */

arch/arm/include/asm/entry-macro-multi.S

+1 −1

Original line number	Diff line number	Diff line
		@@ -42,5 +42,5 @@
		\symbol_name:
		mov r4, lr
		arch_irq_handler_default
		mov pc, r4
		ret r4
		.endm