Re: 2.4.x oops with X

[Andreas Hartmann <andihartmann@01019freenet.de>]

Andreas Hartmann schrieb:
[...]
> But now, the question is:
> Why does X crash running kernel 2.4.x with glibc 2.3.4 and not with kernel
> 2.6.10? Why does X run fine using kernel 2.4 and 2.6 with glibc 2.3.3?
> 
> ----------------------------------------------
> 	|		glibc
> 	|	2.3.3		2.3.4
> ------|-------------------------------------
> kernel|
> 2.4	|	X ok		X segfaults
> 2.6	|	X ok		X ok


Meanwhile, I could find where X crashes using glibc 2.3.4 with kernel 2.4.
It's this piece of code in linux_vm86.c:267

static int
vm86_rep(struct vm86_struct *ptr)
{
    int __res;

#ifdef __PIC__
    /* When compiling with -fPIC, we can't use asm constraint "b" because
       %ebx is already taken by gcc. */
    __asm__ __volatile__("pushl %%ebx\n\t"
                         "movl %2,%%ebx\n\t"
                         "movl %1,%%eax\n\t"
                         "int $0x80\n\t"
                         "popl %%ebx"
                         :"=a" (__res)
                         :"n" ((int)113), "r" ((struct vm86_struct *)ptr));
#else
    __asm__ __volatile__("int $0x80\n\t"
                         :"=a" (__res):"a" ((int)113),
                         "b" ((struct vm86_struct *)ptr));
#endif

            if (__res < 0) {
                errno = -__res;
                __res = -1;
            }
            else errno = 0;
            return __res;
}


The function ExecX86int10 (vbe.c) calls do_vm86 (linux_vm86.c), which
calls vm86_rep (linux_vm86.c).


I don't understand, why this piece of assembler code works fine with glibc
2.3.3, but not with glibc 2.3.4, running kernel 2.4.x. It works fine again
with kernel 2.6.



Kind regards,
Andreas Hartmann