Re: MIPS stack tracing

[Daniel Jacobowitz <drow@mvista.com>]

On Thu, Feb 07, 2002 at 09:55:57AM -0500, Don Bowman wrote:
> > > 
> > > Upon examination of gas, the .pdr section is only emitted if
> > > MIPS_STABS_ELF is defined.  Am I to assume that if I'm using
> > > DWARF2 this won't occur? The code which actually emits it
> > > seems to be in ecoff.c.
> > 
> > No.  It should be emitted unless we are emitting .mdebug, which we
> > don't do any more for mips-*-linux.
> 
> The code in gas is wrapped in #ifdef MIPS_STABS_ELF.

Yes.  That affects any assembler that supports stabs, not any assembler
currently emitting stabs :)  Bad naming perhaps.

> > > This doesn't seem right to me, if I dump my .pdr section I get:
> > > Contents of section .pdr:
> > >  0000 00400080 00000000 00000000 00000000  .@..............
> > >  0010 00000000 00000000 00000000 00000000  ................
> > >  0020 74430080 00000000 00000000 00000000  tC..............
> > >  0030 00000000 00000000 00000000 00000000  ................
> > >  0040 b8430080 00000000 00000000 00000000  .C..............
> > >  ...
> > > 
> > > But all of my addresses start @ 0x80000000.
> > 
> > Careful, it has relocations if you look at it in an object.  Also
> > careful, you have a host-target endian mismatch.  That first word is
> > 0x80000400.
> 
> If I run objdump -r, there are no relocations, my image is fully
> located.
> 
> Interestingly, my host is little endian, my target is little endian.
> Any guess on why those addresses whould show up as big endian?

No idea...

> Also, from gas, it appears a .pdr record is 7 words long, but the
> .pdr shows an 8-word recurrence of the address. I assume it aligns?

No, the first word is the address of the symbol and the other 7 are
data.

> So should the endianess be swapped here [ie reverse of both my host
> and target]? Or do I have a bug in gas to fix first :) Is PDR a
> standard of any sort, or is it just a gas invention?

Not sure.  But no bug in gas - only a bug in perhaps objdump.
-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer