From f00ec48fadf5e37e7889f14cff900aa70d18b644 Mon Sep 17 00:00:00 2001 From: Russell King Date: Sat, 4 Sep 2010 10:47:48 +0100 Subject: ARM: Allow SMP kernels to boot on UP systems UP systems do not implement all the instructions that SMP systems have, so in order to boot a SMP kernel on a UP system, we need to rewrite parts of the kernel. Do this using an 'alternatives' scheme, where the kernel code and data is modified prior to initialization to replace the SMP instructions, thereby rendering the problematical code ineffectual. We use the linker to generate a list of 32-bit word locations and their replacement values, and run through these replacements when we detect a UP system. Signed-off-by: Russell King --- arch/arm/include/asm/assembler.h | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) (limited to 'arch/arm/include/asm/assembler.h') diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h index 6e8f05c8a1c..062b58c029a 100644 --- a/arch/arm/include/asm/assembler.h +++ b/arch/arm/include/asm/assembler.h @@ -154,16 +154,39 @@ .long 9999b,9001f; \ .popsection +#ifdef CONFIG_SMP +#define ALT_SMP(instr...) \ +9998: instr +#define ALT_UP(instr...) \ + .pushsection ".alt.smp.init", "a" ;\ + .long 9998b ;\ + instr ;\ + .popsection +#define ALT_UP_B(label) \ + .equ up_b_offset, label - 9998b ;\ + .pushsection ".alt.smp.init", "a" ;\ + .long 9998b ;\ + b . + up_b_offset ;\ + .popsection +#else +#define ALT_SMP(instr...) +#define ALT_UP(instr...) instr +#define ALT_UP_B(label) b label +#endif + /* * SMP data memory barrier */ .macro smp_dmb #ifdef CONFIG_SMP #if __LINUX_ARM_ARCH__ >= 7 - dmb + ALT_SMP(dmb) #elif __LINUX_ARM_ARCH__ == 6 - mcr p15, 0, r0, c7, c10, 5 @ dmb + ALT_SMP(mcr p15, 0, r0, c7, c10, 5) @ dmb +#else +#error Incompatible SMP platform #endif + ALT_UP(nop) #endif .endm -- cgit v1.2.3-70-g09d2