On Mon, Feb 22, 2016 at 12:07:00PM +0100, Roger Pau Monné wrote:
El 20/2/16 a les 3:41, Kevin O'Connor ha escrit:
On Tue, Feb 16, 2016 at 06:21:10PM +0100, Roger Pau Monné wrote:
El 16/2/16 a les 17:33, Kevin O'Connor ha escrit:
On Tue, Feb 16, 2016 at 01:56:26PM +0100, Roger Pau Monne wrote:
According to the output from readelf, the .text section should be aligned to 16:
Section Headers: [Nr] Name Type Addr Off Size ES Flg Lk Inf Al [ 0] (null) NULL 00000000 000000 000000 00 0 0 0 [ 1] .text PROGBITS 000de300 000300 021d00 00 AX 0 0 16 [...]
This however doesn't seem to be enforced when the relocations are generated. The following patch tries to address this by making sure the space used for the relocations it also aligned to the same value as the .text section.
Thanks. What goes wrong if the .text section is not aligned? The code has already been assigned physical addresses by this point, so it should not impact the runtime code.
It seems like ELF toolchain objcopy chokes if a section address is not aligned to the alignment specified by the section, see:
The snippet shown above has addr aligned to 16 (which matches latest upstream), so it's not a problem, but the current SeaBIOS version shipped in Xen 4.5 (1.7.5 IIRC) ends up with an addr that's not a multiple of 16, as shown in the bug report, and objcopy complains with:
objcopy: elf_update() failed: Layout constraint violation
Thanks. I agree it should be fixed. However, I think there are a few other cases that could cause the ".text" section alignment to be off. Are you okay with the patch below instead?
Yes, looks fine to me. AFAICT SeaBIOS packs all the sections (.text, .data, .rodata) ibnside of the .text section, which I didn't realize before.
Thanks, I committed the change.