diff options
Diffstat (limited to 'sys/boot/arm/uboot/start.S')
| -rw-r--r-- | sys/boot/arm/uboot/start.S | 48 |
1 files changed, 39 insertions, 9 deletions
diff --git a/sys/boot/arm/uboot/start.S b/sys/boot/arm/uboot/start.S index 6e8f117..1ef21f3 100644 --- a/sys/boot/arm/uboot/start.S +++ b/sys/boot/arm/uboot/start.S @@ -29,12 +29,38 @@ #include <machine/asm.h> #include <machine/armreg.h> + .text + .extern _C_LABEL(self_reloc), _C_LABEL(main) + .weak _DYNAMIC + /* * Entry point to the loader that U-Boot passes control to. */ - .text .globl _start _start: + +#ifdef _ARM_ARCH_6 + mrc p15, 0, ip, c1, c0, 0 + orr ip, ip, #(CPU_CONTROL_UNAL_ENABLE) + orr ip, ip, #(CPU_CONTROL_AFLT_ENABLE) + mcr p15, 0, ip, c1, c0, 0 +#endif + /* + * Do self-relocation when the weak external symbol _DYNAMIC is non-NULL. + * When linked as a dynamic relocatable file, the linker automatically + * defines _DYNAMIC with a value that is the offset of the dynamic + * relocation info section. + * Note that we're still on u-boot's stack here, but the self_reloc + * code uses only a couple dozen bytes of stack space. + */ + adr ip, .here_off /* .here_off is a symbol whose value */ + ldr r0, [ip] /* is its own offset in the text seg. */ + sub r0, ip, r0 /* Get its pc-relative address and */ + ldr r1, .dynamic_off /* subtract its value and we get */ + teq r1, #0 /* r0 = physaddr we were loaded at. */ + addne r1, r1, r0 /* r1 = dynamic section physaddr. */ + blne _C_LABEL(self_reloc) /* Do reloc if _DYNAMIC is non-NULL. */ + /* Hint where to look for the API signature */ ldr ip, =uboot_address str sp, [ip] @@ -44,16 +70,20 @@ _start: str r8, [ip, #0] str r9, [ip, #4] -#ifdef _ARM_ARCH_6 - mrc p15, 0, r2, c1, c0, 0 - orr r2, r2, #(CPU_CONTROL_UNAL_ENABLE) - orr r2, r2, #(CPU_CONTROL_AFLT_ENABLE) - mcr p15, 0, r2, c1, c0, 0 -#endif - - /* Start loader */ + /* + * Start loader. This is basically a tail-recursion call; if main() + * returns, it returns to u-boot (which reports the value returned r0). + */ b main + /* + * Data for self-relocation, in the text segment for pc-rel access. + */ +.here_off: + .word . +.dynamic_off: + .word _DYNAMIC + /* * syscall() */ |
