Re: Fixed strace [ was Re: ls -l is broken ]
>
> On Wed, May 06, 2009 at 12:04:42PM -0400, Kyle McMartin wrote:
> ...
> > At a guess, you're probably right, the faulting insn is a load:
> >
> > 0x0002b3a8 <__canonicalize_funcptr_for_compare+48>: bb,>= r26,1e,0x2b394 <__canonicalize_funcptr_for_compare+28>
> > 0x0002b3ac <__canonicalize_funcptr_for_compare+52>: copy r26,r3
> > 0x0002b3b0 <__canonicalize_funcptr_for_compare+56>: addil L%800,dp,r1
> > 0x0002b3b4 <__canonicalize_funcptr_for_compare+60>: ldw 294(r1),ret1
> > 0x0002b3b8 <__canonicalize_funcptr_for_compare+64>: depwi 0,31,2,r3
> > 0x0002b3bc <__canonicalize_funcptr_for_compare+68>: ldw 0(r3),r26
> >
> > god knows I can't recall how DEP*I work, but I guess this is clearing
> > the bottom two bits of %r3 if bit 31 is set in %r26?
>
> Wouldn't 1e == bit 30?
Yes. This is the 'L' field in the procedure label layout. Bit 31
is X field and reserved.
> And yes, "depwi 0,31,2,XX" is clearing the bottom 2 bits of XX.
>
> I'm a bit confused about the ">=" conditional since only one bit is tested.
> So is the copy only executed on branch not taken case?
The conditions for bb are unique. The word conditions are < and >=.
The double word conditions are *< and *>=. See Table D-15 on page D-9
in arch.
This code sequence is used for indirect calls (e.g., $$dyncall).
Dave
--
J. David Anglin dave.anglin@nrc-cnrc.gc.ca
National Research Council of Canada (613) 990-0752 (FAX: 952-6602)
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