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/iwmmxt.S | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'arch/arm/kernel/iwmmxt.S') diff --git a/arch/arm/kernel/iwmmxt.S b/arch/arm/kernel/iwmmxt.S index a5599cfc43cb..0960be7953f0 100644 --- a/arch/arm/kernel/iwmmxt.S +++ b/arch/arm/kernel/iwmmxt.S @@ -179,7 +179,7 @@ concan_load: get_thread_info r10 #endif 4: dec_preempt_count r10, r3 - mov pc, lr + ret lr /* * Back up Concan regs to save area and disable access to them @@ -265,7 +265,7 @@ ENTRY(iwmmxt_task_copy) mov r3, lr @ preserve return address bl concan_dump msr cpsr_c, ip @ restore interrupt mode - mov pc, r3 + ret r3 /* * Restore Concan state from given memory address @@ -301,7 +301,7 @@ ENTRY(iwmmxt_task_restore) mov r3, lr @ preserve return address bl concan_load msr cpsr_c, ip @ restore interrupt mode - mov pc, r3 + ret r3 /* * Concan handling on task switch @@ -323,7 +323,7 @@ ENTRY(iwmmxt_task_switch) add r3, r0, #TI_IWMMXT_STATE @ get next task Concan save area ldr r2, [r2] @ get current Concan owner teq r2, r3 @ next task owns it? - movne pc, lr @ no: leave Concan disabled + retne lr @ no: leave Concan disabled 1: @ flip Concan access XSC(eor r1, r1, #0x3) @@ -350,7 +350,7 @@ ENTRY(iwmmxt_task_release) eors r0, r0, r1 @ if equal... streq r0, [r3] @ then clear ownership msr cpsr_c, r2 @ restore interrupts - mov pc, lr + ret lr .data concan_owner: -- cgit