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SubjectRe: Bug Report: Dereferencing a bad pointer
I get a seg fault on both 2.2 and 2.4 kernels by running the following
one-line C program:
int main() { int k = (int *)0x0; }

Debugging the offender,
int main() { int k = (int *)0xc0000000; }
is not very informative: single-stepping over the sole command just
hangs, and you have to press Control-C to interrupt gdb, at which point
you can single-step right into the same problem again.

When the program hangs, 'top' says that the CPU is fully utilized and
the system is spending 80% of its time in the kernel and 20% in the
offending process.

Have you not been able to duplicate it on a 2.4 kernel on x86? If not,
please tell me which 2.4 kernel correctly seg faults.


David Chandler

--

_____
David L. Chandler. GrammaTech, Inc.
mailto:chandler@grammatech.com http://www.grammatech.com


"Richard B. Johnson" wrote:
>
> On Thu, 8 Nov 2001, David Chandler wrote:
>
> > Dick,
> >
> > You're right that the one-liner below may not necessarily produce a seg
> > fault, but shouldn't it terminate normally if it doesn't? After all,
> > the program just *reads*. Hanging does not seem to be an option!
> >
> You may want to see if any deliberate seg-fault actually gets
> delivered. Try to read *(0). If that works (seg-faults), then
> there may be a problem with some boundary condition on paging.
>
> I can't duplicate the problem here. You can also try to trace
> the code execution to see if it falls into some user-space loop.
>
> Cheers,
> Dick Johnson
>
> Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips).
>
> I was going to compile a list of innovations that could be
> attributed to Microsoft. Once I realized that Ctrl-Alt-Del
> was handled in the BIOS, I found that there aren't any.
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