From 6ebbf2ce437b33022d30badd49dc94d33ecfa498 Mon Sep 17 00:00:00 2001 From: Russell King Date: Mon, 30 Jun 2014 16:29:12 +0100 Subject: ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+ MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Tested-by: Stephen Warren # Tegra Jetson TK1 Tested-by: Robert Jarzmik # mioa701_bootresume.S Tested-by: Andrew Lunn # Kirkwood Tested-by: Shawn Guo Tested-by: Tony Lindgren # OMAPs Tested-by: Gregory CLEMENT # Armada XP, 375, 385 Acked-by: Sekhar Nori # DaVinci Acked-by: Christoffer Dall # kvm/hyp Acked-by: Haojian Zhuang # PXA3xx Acked-by: Stefano Stabellini # Xen Tested-by: Uwe Kleine-König # ARMv7M Tested-by: Simon Horman # Shmobile Signed-off-by: Russell King --- arch/arm/lib/getuser.S | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'arch/arm/lib/getuser.S') diff --git a/arch/arm/lib/getuser.S b/arch/arm/lib/getuser.S index 9b06bb41fca6..0f958e3d8180 100644 --- a/arch/arm/lib/getuser.S +++ b/arch/arm/lib/getuser.S @@ -36,7 +36,7 @@ ENTRY(__get_user_1) check_uaccess r0, 1, r1, r2, __get_user_bad 1: TUSER(ldrb) r2, [r0] mov r0, #0 - mov pc, lr + ret lr ENDPROC(__get_user_1) ENTRY(__get_user_2) @@ -56,20 +56,20 @@ rb .req r0 orr r2, rb, r2, lsl #8 #endif mov r0, #0 - mov pc, lr + ret lr ENDPROC(__get_user_2) ENTRY(__get_user_4) check_uaccess r0, 4, r1, r2, __get_user_bad 4: TUSER(ldr) r2, [r0] mov r0, #0 - mov pc, lr + ret lr ENDPROC(__get_user_4) __get_user_bad: mov r2, #0 mov r0, #-EFAULT - mov pc, lr + ret lr ENDPROC(__get_user_bad) .pushsection __ex_table, "a" -- cgit v1.2.3