[Xen-devel] Problem with modify CR0 of xen kernel

[errik <waitingfor2009marry@xxxxxxxxx>]

Hi All,

    

   This is a function of a kernel module, but when I calls this function, a segment fault error happens, I don't know why because the code works well on other types of kernel such as PAE and default.

 unsigned long clear_and_return_cr0(void)
{
    unsigned long cr0 = 0;
    unsigned long ret;
#ifdef X86_64
    __asm__ __volatile("movq %%cr0, %%rax" : "=a"(cr0));
    ret = cr0;
    cr0 &= 0xfffffffffffeffff;
    __asm__ __volatile__("movq %%rax, %%cr0" : : "a"(cr0));
#else
    __asm__ __volatile("mov %%cr0, %%eax" : "=a"(cr0));
    ret = cr0;
    cr0 &= 0xfffeffff;
    __asm__ __volatile__("mov %%eax, %%cr0" : : "a"(cr0));
   
#endif
    return ret;
}

 

May anyone give me some suggestions?

 

Thanks a lot!

Eric

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