One point is that in the function apply_relocate_add a 4-byte aligned
address is created:
627 dot = (Elf64_Addr)loc & ~0x03;
628 loc64 = (Elf64_Xword *)loc;
and used as a 64-bit location
711 case R_PARISC_DIR64:
712 /* 64-bit effective address */
713 *loc64 = val + addend;
714 break;
So, 8-byte word is read with a 4-byte alignment.
I am busy building a parisc hardware emulator. It boots Linux, but it is
unstable yet. There are unaligned accesses in the emulation trace. I was
wandering whether it is normal behavior or caused by a bug in the
emulation.
The emulation trace gives a lot of accesses like this:
0-4011f968: translate_virtual_write unaligned_trap, va=0:416a20c
pa=1db1820c
0-4011f968: translate_virtual_write unaligned_trap, va=0:416a21c
pa=1db1821c
0-4011f968: translate_virtual_write unaligned_trap, va=0:416a224
pa=1db18224
They are indeed 4-byte aligned. The PC address matches
apply_relocate_add in the kernel map.
Thanks,
Artem
Kyle McMartin wrote:
On Wed, Aug 26, 2009 at 10:37:13AM +0200, Artem Alimarine wrote:
Hi guys,
I see unaligned access happening in apply_relocate_add. Is this
normal expected behavior?
Kernel 2.6.26.2, single CPU (Standard Debian 5.0.2). Address 0x4011f968.
No, definitely not. relocations are applied to instructions, which
should always be instruction-width (4 bytes) aligned... Since we do
modify-replace on placeholders, it should never be using anything other
than a store-word to do it... do you have any more data on this?
regards, Kyle
dr. Artem Alimarine <artem.alimarine@xxxxxxxxxxxxx
<mailto:artem.alimarine@xxxxxxxxxxxxx>>
Software Architect
STROMASYS SA
Kyle McMartin wrote:
On Wed, Aug 26, 2009 at 10:37:13AM +0200, Artem Alimarine wrote:
Hi guys,
I see unaligned access happening in apply_relocate_add. Is this normal
expected behavior?
Kernel 2.6.26.2, single CPU (Standard Debian 5.0.2). Address 0x4011f968.
No, definitely not. relocations are applied to instructions, which
should always be instruction-width (4 bytes) aligned... Since we do
modify-replace on placeholders, it should never be using anything other
than a store-word to do it... do you have any more data on this?
regards, Kyle
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email;internet:artem.alimarine@xxxxxxxxxxxxx
title:Software Architect
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tel;fax:+31-40-2390800
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