On Wednesday 10 May 2017 07:11 PM, Manfred Schlaegl wrote:
Using u-boot-2017.05 on i.MX6UL we ran into following problem: Initially U-Boot could be started normally. If we added one random command in configuration, the newly generated image hung at startup (last output was DRAM: 256 MiB).
We tracked this down to a data abort within relocation (relocated_code).
relocated_code in arch/arm/lib/relocate.S copies 8 bytes per loop iteration until the source pointer is equal to __image_copy_end. In a good case __image_copy_end was aligned to 8 bytes, so the loop stopped as suggested, but in an errornous case __image_copy_end was not aligned to 8 bytes, so the loop ran out of bounds and caused a data abort exception.
Well I agree with this patch but I have a small query. Looking at the relocation code:
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
IIUC, this loops exits as soon as r1 >= r2
In your case r1 is __image_copy_start r0 is relocation address r2 is __image_copy_end (which is 4 byte aligned)
In the corner case you mentioned there will be extra memcpy of 4 bytes from address in r1 to address in r0. I assume you are running from DDR and relocation offset is calculated such that (aligned to previous 4K page) it should be able to accommodate extra 4 bytes(I assume). I am wondering why should this give a data abort.
Thanks and regards, Lokesh
This patches solves the issue by aligning __image_copy_end to 8 byte using the linker script related to arm.
I don't know if it's the correct way to solve this, so some review would be very appreciated.
arch/arm/cpu/u-boot.lds | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/cpu/u-boot.lds b/arch/arm/cpu/u-boot.lds index 37d4c60..70bee1a 100644 --- a/arch/arm/cpu/u-boot.lds +++ b/arch/arm/cpu/u-boot.lds @@ -165,7 +165,7 @@ SECTIONS *(.__efi_runtime_rel_stop) }
- . = ALIGN(4);
. = ALIGN(8);
.image_copy_end : {