Re: kernel debugging

[uma@email.unc.edu]

I am using Red Hat sources, which has function open_kcore() hardcoded to
return -EPERM always.

Changing this function to the way it is defined in the public sources (as
shown below) did the trick.

open_kcore(struct inode * inode, struct file * filp)
{
   return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
}

I am now able to use gdb to examine kernel symbols.

Uma.


Quoting UmaMaheswari Devi <uma@cs.unc.edu>:

> I am new to kernel hacking and am facing problems in tryingstatic int
to peek at the
> runtime values of some kernel variables using gdb.
>
> I am issuing the gdb command as follows:
>     gdb vmlinux /proc/kcore
> This displays the message
>    /proc/kcore: Operation not permitted
> before the (gdb) prompt is displayed.
> gdb then prints a value of 0 for any valid variable that is requested.
>
> vmlinux appears to be OK, as gdb correctly identifies undefined variables.
> The problem seems to be with /proc/kcore. This file has a permission 
> of 400. I
> am using the Red Hat distribution.
>
> Any help is appreciated. Thanks,
> Uma.
>
>
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