[PATCH v3 1/2] ntdll: Add emulation for UMIP instructions.

[Alexandre Julliard]

Brendan Shanks <bshanks at codeweavers.com> writes:

> +extern int have_cpuid (void );
> +
> +extern void do_cpuid_cx( unsigned int ax, unsigned int cx, unsigned int *p );
> +__ASM_GLOBAL_FUNC( do_cpuid_cx,
> +                   "pushl %esi\n\t"
> +                   "pushl %ebx\n\t"
> +                   "movl 12(%esp),%eax\n\t"
> +                   "movl 16(%esp),%ecx\n\t"
> +                   "movl 20(%esp),%esi\n\t"
> +                   "cpuid\n\t"
> +                   "movl %eax,(%esi)\n\t"
> +                   "movl %ebx,4(%esi)\n\t"
> +                   "movl %ecx,8(%esi)\n\t"
> +                   "movl %edx,12(%esi)\n\t"
> +                   "popl %ebx\n\t"
> +                   "popl %esi\n\t"
> +                   "ret" )
> +
> +static int umip_enabled( void )
> +{
> +    /* Check cpuid to see if UMIP is supported.
> +     * UMIP bit is EAX=0x07,ECX=0x0, ECX bit 2
> +     * (CPUID.07H.0H:ECX:UMIP[bit 2] in Intel syntax)
> +     *
> +     * It would be preferable to check if UMIP is actually enabled
> +     * (CR4.UMIP), but that can't be done from userspace.
> +     */
> +    unsigned int regs[4];
> +
> +    if (!have_cpuid()) return 0;
> +
> +    do_cpuid_cx( 0x00000000, 0, regs );  /* get standard cpuid level and vendor name */
> +    if (regs[0] >= 0x00000007)   /* Check for supported cpuid version */
> +    {
> +        do_cpuid_cx( 0x00000007, 0, regs );
> +        if (regs[2] & (1 << 2))
> +            return 1;
> +    }
> +
> +    return 0;
> +}
> +#endif

There shouldn't be any reason to check this. If UMIP is not enabled you
won't get a fault in the first place.

Also I don't see why you use #ifdef linux, surely that code could work
on other platforms too.

-- 
Alexandre Julliard
julliard at winehq.org