extern void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot);
extern void *__vmalloc_area(struct vm_struct *area, gfp_t gfp_mask,
pgprot_t prot);
extern void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot);
extern void *__vmalloc_area(struct vm_struct *area, gfp_t gfp_mask,
pgprot_t prot);