* Nicolas Pitre <nicolas.pitre@xxxxxxxxxx> [110421 06:18]: > On Thu, 21 Apr 2011, Tony Lindgren wrote: > > > Otherwise we end up overwriting ourselves. This fixes booting > > on n900 after commit 6d7d0ae51574943bf571d269da3243257a2d15db > > (ARM: 6750/1: improvements to compressed/head.S). > > > > Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx> > > I don't understand why this is needed. The copy loop is explicitly > copying from the end going backward exactly to cope with this > possibility. This one is starting to make sense now too after the stack corrupting the image issue is out of the way :) We can't overwrite the running code when relocating only a small amount, say 0x100 or so. There's no need to relocate all the way past the compressed kernel, we just need to relocate past the size of the code in head.o. Updated patch below using the GOT end instead of the compressed image end. Regards, Tony From: Tony Lindgren <tony@xxxxxxxxxxx> Date: Wed, 27 Apr 2011 02:06:13 -0700 Subject: [PATCH] ARM: Fix relocation to move past the running code Otherwise we end up overwriting ourselves partially when relocating less than size of the running code in head.S. Without this patch, a system will not boot if the compressed image load address is slightly less than where the compressed image gets relocated. For example, using mkimage to set the load address to something like zreladdr + uncompressed image size - 0x100 will make the system hang without this patch. Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx> --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -286,6 +286,7 @@ dtb_check_done: * r5 = start of this image * r9 = size of decompressed image * r10 = end of this image, including bss/stack/malloc space if non XIP + * r12 = GOT end, corrupted if relocating * We basically want: * r4 - 16k page directory >= r10 -> OK * r4 + image length <= r5 -> OK @@ -297,11 +298,20 @@ dtb_check_done: cmp r10, r5 bls wont_overwrite + /* + * Check if the relocate address overlaps the running code in + * head.S. In that case we need to relocate past the code + * to avoid overwriting some of the running code. + */ + add r12, r12, r5 @ use GOT end for upper limit + cmp r10, r12 @ relocating less than GOT end? + mov r10, r12 @ if so, relocate past GOT end + /* * Relocate ourselves past the end of the decompressed kernel. * r5 = start of this image * r6 = _edata - * r10 = end of the decompressed kernel + * r10 = end of the decompressed kernel or end of GOT end if larger * Because we always copy ahead, we need to do it from the end and go * backward in case the source and destination overlap. */ -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
