Re: 16k or 64k PAGE_SIZE and "illegal instruction" (signal -4) errors

[Ralf Baechle <ralf@linux-mips.org>]

On Tue, Aug 26, 2014 at 09:16:56AM -0400, Joshua Kinard wrote:

> On 08/26/2014 08:03, Ralf Baechle wrote:
> > On Tue, Aug 26, 2014 at 07:06:56AM -0400, Joshua Kinard wrote:
> > 
> >> o32 userland is the primary on both systems.  However, the last SIGILL was
> >> under the 64k PAGE_SIZE kernel inside of an n32 chroot compiling the 'boost'
> >> package on the Octane, which I restarted that and it's not complained since.
> >>  Also got SIGILL on the 16k PAGE_SIZE kernel when I booted 16k PAGE_SIZE the
> >> first time and ran 'ps'.  Subsequent runs of 'ps' didn't reproduce the
> >> error.  Also saw SIGILLs in the bootlog of the 16k PAGE_SIZE kernel when
> >> "rm" was ran once (couldn't reproduce) and when mdadm tried to put one of
> >> the arrays back together.  Subsequent runs using similar argument lines
> >> don't reproduce once I got to a root shell.
> >>
> >> Being it's a Gentoo install...the o32 userland is pretty fresh.  Especially
> >> on the Octane, where I literally rebuilt the old userland over 2-3 times
> >> just to make sure all the old 5-year cruft was gone.  The n32 userland
> >> chroot is brand-spanking new.  gcc-4.7.x only for now on both, because of
> >> PR61538 in gcc.  Latest binutils.
> >>
> >> The O2 is chugging away happily so far in updating a bunch of packages.  So
> >> I am leaning towards this being another quirk I have to hunt down in the
> >> Octane's code again.  There isn't much in the Octane-specific code that
> >> deals with memory, though -- it seems the higher-level MIPS memory code
> >> handles most things just fine.
> > 
> > Can you enable core dumps?  I'm wondering about the EPC of the crashed
> > process.  If it's at a function entry or the beginning of a page that
> > might indicate there is an issue with flushing caches after the containing
> > page got loaded.  Also interesting to know if this possibly happened in a
> > signal trampoline or VDSO.
> > 
> > These are just the usual suspects - nothing indicates this case is actually
> > related.
> 
> (Missed the reply all on the last one)
> 
> Enabled coredumps and got the 'shash' program to fail a second time (first
> program to do so)...so I'll rebuild that with debugging symbols and try to
> trip it up again later on.
> 
> Is a core file from a binary w/o debugging of any value?

Yes - it will contain registers etc.  Just what really matters in this case.
We don't need the debug info because we're not interested in debugging the
application.

  Ralf