Re: Fixed strace [ was Re: ls -l is broken ]
> On Tue, May 05, 2009 at 03:46:57PM -0400, John David Anglin wrote:
> > > On Tue, May 05, 2009 at 03:09:50PM -0400, John David Anglin wrote:
> > > > Probably, the cast should be to int. __canonicalize_funcptr_for_compare
> > > > isn't used in the 64-bit runtime.
> > > >
> > > > Still, I'm not sure why this fixed the problem as
> > > > __canonicalize_funcptr_for_compare checks for -1.
> > > >
> > >
> > > If we cast both sides to int, then we don't generate a call there...
> >
> > That will certainly fix the problem but I'd really like to know
> > why we get a segv. I suspect we are not handling a deferred function
> > pointer correctly.
> >
>
> 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?
>
> (gdb) p/x $r3
> $3 = 0x407d2f18
> (gdb) p/x $r26
> $4 = 0x407d2f1a
>
> This looks like the sigaction handler, (it appears __canon..._compare
> detects -1 already.)
This all seems correct. r3 should be pointing to a function descriptor
for the sigaction handler (plabel bit is set). What is the interruption
generated by the ldw at 0x0002b3bc?
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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