On Mon, May 13, 2013 at 03:37:32PM +0000, Leif Lindholm wrote:
> The import into the collaborative branch discarded the call to
> get_real_bss_start before starting the BSS zeroing operation.
>
> While get_real_bss_start might have been a bit of an ugly hack,
> simply discarding it means that we now end up doing unaligned
> STR operations, and any platform with MMU disabled fails to boot.
>
> The attached patch prepends a bytewise zeroing loop until
> word-aligned, and then continue as before.
>
> /
> Leif
> === modified file 'grub-core/kern/arm/uboot/startup.S'
> --- grub-core/kern/arm/uboot/startup.S 2013-05-03 13:07:39 +0000
> +++ grub-core/kern/arm/uboot/startup.S 2013-05-13 14:59:43 +0000
> @@ -100,7 +100,13 @@
> @ Since we _are_ the C run-time, we need to manually zero the BSS
> @ region before continuing
> ldr r0, =EXT_C(__bss_start) @ zero from here
> - ldr r1, =EXT_C(_end) @ to here
> + @ If unaligned, bytewise zero until base address aligned.
> + mov r1, #0
> +1: tst r0, #3
> + beq 2f
> + strb r1, [r0], #1
> + b 1b
> +2: ldr r1, =EXT_C(_end) @ to here
> mov r2, #0
> 1: str r2, [r0], #4
> cmp r0, r1
What if I have a 1 byte BSS aligned at 1 byte? You would zero 3 bytes
and overshoot _end and then what happens after the cmp in the last line?
MfG
Goswin
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