Re: COMPAT_40 broken in current amd64 kernel?

[Paul Goyette <paul%whooppee.com@localhost>]

On Sun, 7 Mar 2010, Paul Goyette wrote:

> On Sun, 7 Mar 2010, Christos Zoulas wrote:
>
> > > However, on a kernel built today, it gives me a core dump due to a "bad
> > > system call".  The backtrace shows that this is the code leading up to
> > > the bad syscall:
> > >
> > > (gdb) x/10i 0x47a598
> > > 0x47a598:       jmpq   0x490ba0
> > > 0x47a59d:       data16
> > > 0x47a59e:       data16
> > > 0x47a59f:       nop
> > > 0x47a5a0:       mov    $0x74,%eax
> > > 0x47a5a5:       mov    %rcx,%r10
> > > 0x47a5a8:       syscall
> > > 0x47a5aa:       jb     0x47a598
> > > 0x47a5ac:       retq
> > > 0x47a5ad:       nop
> > > (gdb)
> >
> > 0x74 == 116 is the old gettimeofday. Something is not loading compat_50.
>
> Well, as I indicated, COMPAT_50 (and COMPAT_40) were both built-in to both 
> kernels in question, so it shouldn't be a matter of "loading".
>
> Regardless, I built a new kernel in a clean $OBJDIR and installed it; 
> magically the problem did not reappear.

Hmmm, things get more and more interesting...

The problem reappeared this morning, after the system and the program in 
question had been running for several days!

Even more interesting is, when I tried to re-run the program I got a 
kernel crash!  (Unfortunately, this is amd64, so I did not get a system 
core dump.)  In the previous instance of this problem, re-running the 
program simply resulted in another user-mode core dump.

This is sounding to me like something is being initialized incorrectly. 
I've attached an old PS/2 keyboard to the machine and turned on 
ddb.onpanic so if this happens again maybe I can debug further.  (Of 
course, with my luck, the next time the problem occurs it will be on a 
machine that doesn't have the keyboard...)


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