Re: [microblaze-uclinux] microblaze: Use of sigaction() leads to crash on exit

["Steven J. Magnani" <steve@xxxxxxxxxxxxxxx>]

On Wed, 2009-11-11 at 21:13 -0600, Steven J. Magnani wrote:
> Hi John,
> 
> On Thu, 2009-11-12 at 10:14 +1000, John Williams wrote:
> >
> > On Wed, Nov 11, 2009 at 2:01 AM, Steven J. Magnani
> > <steve@xxxxxxxxxxxxxxx> wrote:
> > 
> > > I've finished porting my noMMU kernel to 2.6.31 and believe I've adapted
> > > my uClibc to the ABI changes (typedefs, system call changes,
> > > SA_RESTORER, etc.) in that release. Most things run fine, which is a
> > > great improvement over my initial port attempt that crashed and burned.
> > >
> > > What I see now (and have ever since 2.6.30) is that quitting the 'top'
> > > program (the procps one, not the busybox one) crashes the entire system.
> > > If I comment out the calls to sigaction() in top.c, I can quit the
> > > program just fine (as long as it's running at the serial console) and
> > > the system stays up. The system still crashes if I try to quit a 'top'
> > > running in a telnet session, which I think is a separate issue.
> > >
> > > Has anyone else running 2.6.3x encountered similar problems, or can
> > > confirm this behavior?
> > 
> > I remember when I did some work to bring uClibc up to 0.9.30.1, that
> > MicroBlaze sighandling had bit-rotted somewhat in the uclibc.org
> > trees, because they'd changed the internal structure and made fairly
> > mechanical and incorrect attempts to bring microblaze forward.
> 
> I'm still working with 0.9.27, if that's an issue. I have the 0.9.30
> tarball, I'll look it over.
> 
> > 
> > I'll dig out some patches that may help.
> 
> Thanks!!
> 
> > 
> > > I noticed that 2.6.31 made some changes to Microblaze signal handling
> > > that bring it more in line with the generic kernel code. Were there also
> > > problems that were being addressed by those changes?
> > 
> > I think more likely is the change to sighandling internals in uClibc.
> > We didn't have to do anything magical to glibc for example, to get the
> > new sighandling in place for the MMU variant.
> 
> It seems to be a problem in uClibc's __libc_sigaction(). If my 'top'
> program goes in there at all, the system crashes when 'top' exits.
> That's true even if I change the function so it returns immediately. I
> suspect scribbling on the program stack, but can't find the culprit.
> Could it be a gcc "weak_alias" thing?

Late breaking update...
It appears that 'top' is subject to the FLT translation bug we discussed
earlier in the year:

    romfs-inst.sh -e CONFIG_USER_PROCPS_TOP //bin/top
    fixflt.sh: Repairing data mismatch detected in top

This is with microblaze-uclinux-gcc 3.4.1. If I recompile with the shiny
new microblaze-unknown-uclinux-uclibc-gcc 4.1.2 and friends, everything
seems to work fine. Unfortunately I can't use that toolchain, at least
not for everything, since there is no g++ available.

Any news on g++ availability for NOMMU? In the meantime I will see if I
can hack my Makefiles to use the older toolchain for just the g
++-dependent parts.

-- Steve


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