From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Thu, 27 Apr 2017 21:32:30 +0200 Subject: [PATCH] [stable v3.18.y] ARM: 8383/1: nommu: avoid deprecated source register on mov Message-ID: <20170427193230.2673449-1-arnd@arndb.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: Stefan Agner Commit 970d96f9a81b0dd83ddd8bce0e5e1ba31881c5f5 upstream. In Thumb2 mode, the stack register r13 is deprecated if the destination register is the program counter (r15). Similar to head.S, head-nommu.S uses r13 to store the return address used after configuring the CPU's CP15 register. However, since we do not enable a MMU, there will be no address switch and it is possible to use branch with link instruction to call __after_proc_init. Avoid using r13 completely by using bl to call __after_proc_init and get rid of __secondary_switched. Beside removing unnecessary complexity, this also fixes a compiler warning when compiling a !MMU kernel: Warning: Use of r13 as a source register is deprecated when r15 is the destination register. Tested-?by: Maxime Coquelin Signed-off-by: Stefan Agner Signed-off-by: Russell King Signed-off-by: Arnd Bergmann ---- I've backported this build fix to 3.18.y as the original patch did not apply cleanly. I rebased it one patch at a time, and each step was fairly straightforward, but I did not test it on hardware, so it would still be nice to have someone else look over the patch to see if I did something wrong. --- arch/arm/kernel/head-nommu.S | 20 +++++++------------- 1 file changed, 7 insertions(+), 13 deletions(-) diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S index cc176b67c134..c6c66dd4be89 100644 --- a/arch/arm/kernel/head-nommu.S +++ b/arch/arm/kernel/head-nommu.S @@ -77,13 +77,12 @@ ENTRY(stext) orr r6, r6, #(1 << MPU_RSR_EN) @ Set region enabled bit bl __setup_mpu #endif - ldr r13, =__mmap_switched @ address to jump to after - @ initialising sctlr adr lr, BSYM(1f) @ return (PIC) address ARM( add pc, r10, #PROCINFO_INITFUNC ) THUMB( add r12, r10, #PROCINFO_INITFUNC ) THUMB( ret r12 ) - 1: b __after_proc_init +1: bl __after_proc_init + b __mmap_switched ENDPROC(stext) #ifdef CONFIG_SMP @@ -106,8 +105,7 @@ ENTRY(secondary_startup) movs r10, r5 @ invalid processor? beq __error_p @ yes, error 'p' - adr r4, __secondary_data - ldmia r4, {r7, r12} + ldr r7, __secondary_data #ifdef CONFIG_ARM_MPU /* Use MPU region info supplied by __cpu_up */ @@ -115,23 +113,19 @@ ENTRY(secondary_startup) bl __setup_mpu @ Initialize the MPU #endif - adr lr, BSYM(__after_proc_init) @ return address - mov r13, r12 @ __secondary_switched address + adr lr, BSYM(1f) @ return (PIC) address ARM( add pc, r10, #PROCINFO_INITFUNC ) THUMB( add r12, r10, #PROCINFO_INITFUNC ) THUMB( ret r12 ) -ENDPROC(secondary_startup) - -ENTRY(__secondary_switched) +1: bl __after_proc_init ldr sp, [r7, #8] @ set up the stack pointer mov fp, #0 b secondary_start_kernel -ENDPROC(__secondary_switched) +ENDPROC(secondary_startup) .type __secondary_data, %object __secondary_data: .long secondary_data - .long __secondary_switched #endif /* CONFIG_SMP */ /* @@ -164,7 +158,7 @@ __after_proc_init: #endif mcr p15, 0, r0, c1, c0, 0 @ write control reg #endif /* CONFIG_CPU_CP15 */ - ret r13 + ret lr ENDPROC(__after_proc_init) .ltorg -- 2.9.0