Re: port-i386/40143: Crash in i386:doreti_checkast()

[Andrew Doran <ad%netbsd.org@localhost>]

On Mon, Dec 22, 2008 at 02:22:18PM -0500, Arnaud Lacombe wrote:
> Andrew Doran wrote:
> > This code block is fragile and has been broken by changes to system call /
> > trap return:
> >
> > http://nxr.homeunix.org/source/xref/sys/arch/i386/i386/trap.c#427
> >
> at first sight, this is not this block which trigger the fault, but
> the test following:
> 
>     455               if (KERNELMODE(vframe->tf_cs, vframe->tf_eflags))
>     456                       goto we_re_toast;
> 
> not sure at all what this means, I'll try to dig a bit more. I can
> provide anything but a crash dump, I can easily reproduce this bug.

The code block I highlighted is there to prevent the fault by installing
default values in the descriptors. It handles application bugs that would
otherwise crash the kernel.

Andrew