On Fri, Mar 2, 2012 at 9:36 PM, H.J. Lu <[email protected]> wrote:
> X86-64 linker optimizes TLS_MODEL_INITIAL_EXEC to TLS_MODEL_LOCAL_EXEC
> by checking
>
> movq foo@gottpoff(%rip), %reg
>
> and
>
> addq foo@gottpoff(%rip), %reg
>
> It uses the REX prefix to avoid the last byte of the previous
> instruction. With 32bit Pmode, we may not have the REX prefix and
> the last byte of the previous instruction may be an offset, which
> may look like a REX prefix. IE->LE optimization will generate corrupted
> binary. This patch makes sure we always output an REX pfrefix for
> UNSPEC_GOTNTPOFF. OK for trunk?
Actually, linker has:
case R_X86_64_GOTTPOFF:
/* Check transition from IE access model:
mov foo@gottpoff(%rip), %reg
add foo@gottpoff(%rip), %reg
*/
/* Check REX prefix first. */
if (offset >= 3 && (offset + 4) <= sec->size)
{
val = bfd_get_8 (abfd, contents + offset - 3);
if (val != 0x48 && val != 0x4c)
{
/* X32 may have 0x44 REX prefix or no REX prefix. */
if (ABI_64_P (abfd))
return FALSE;
}
}
else
{
/* X32 may not have any REX prefix. */
if (ABI_64_P (abfd))
return FALSE;
if (offset < 2 || (offset + 3) > sec->size)
return FALSE;
}
So, it should handle the case without REX just OK. If it doesn't, then
this is a bug in binutils.
Uros.
