【u-boot】重定位（ARM32）-relocate_code

本文基于u-boot版本2016.03。

一、开篇

relocate_code实现在/arch/arm/lib/relocate.S中，汇编代码如下：

ENTRY(relocate_code)ldr	r1, =__image_copy_start	/* r1 <- SRC &__image_copy_start */subs	r4, r0, r1		/* r4 <- relocation offset */beq	relocate_done		/* skip relocation */ldr	r2, =__image_copy_end	/* r2 <- SRC &__image_copy_end */copy_loop:ldmia	r1!, {r10-r11}		/* copy from source address [r1]    */stmia	r0!, {r10-r11}		/* copy to   target address [r0]    */cmp	r1, r2			/* until source end address [r2]    */blo	copy_loop/** fix .rel.dyn relocations*/ldr	r2, =__rel_dyn_start	/* r2 <- SRC &__rel_dyn_start */ldr	r3, =__rel_dyn_end	/* r3 <- SRC &__rel_dyn_end */
fixloop:ldmia	r2!, {r0-r1}		/* (r0,r1) <- (SRC location,fixup) */and	r1, r1, #0xffcmp	r1, #23			/* relative fixup? */bne	fixnext/* relative fix: increase location by offset */add	r0, r0, r4ldr	r1, [r0]add	r1, r1, r4str	r1, [r0]
fixnext:cmp	r2, r3blo	fixlooprelocate_done:#ifdef __XSCALE__/** On xscale, icache must be invalidated and write buffers drained,* even with cache disabled - 4.2.7 of xscale core developer's manual*/mcr	p15, 0, r0, c7, c7, 0	/* invalidate icache */mcr	p15, 0, r0, c7, c10, 4	/* drain write buffer */
#endif/* ARMv4- don't know bx lr but the assembler fails to see that */#ifdef __ARM_ARCH_4__mov	pc, lr
#elsebx	lr
#endifENDPROC(relocate_code)

查看u-boot汇编如下：

从上述汇编可知，relocate_co