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/kernel/fiqasm.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch/arm/kernel/fiqasm.S') diff --git a/arch/arm/kernel/fiqasm.S b/arch/arm/kernel/fiqasm.S index 207f9d652010..8dd26e1a9bd6 100644 --- a/arch/arm/kernel/fiqasm.S +++ b/arch/arm/kernel/fiqasm.S @@ -32,7 +32,7 @@ ENTRY(__set_fiq_regs) ldr lr, [r0] msr cpsr_c, r1 @ return to SVC mode mov r0, r0 @ avoid hazard prior to ARMv4 - mov pc, lr + ret lr ENDPROC(__set_fiq_regs) ENTRY(__get_fiq_regs) @@ -45,5 +45,5 @@ ENTRY(__get_fiq_regs) str lr, [r0] msr cpsr_c, r1 @ return to SVC mode mov r0, r0 @ avoid hazard prior to ARMv4 - mov pc, lr + ret lr ENDPROC(__get_fiq_regs) -- cgit v1.2.1