最近做opengl模拟器的时候，需要从用户虚拟地址得到实际的物理地址，在网上找到一个不错的参考（http://www.eefocus.com/html/09-05/71993s.shtml），稍微修改了一下（用current替代了find_task_by_pid.

1. #include <linux/sched.h>
2. #include <linux/mm.h>
3. #include <asm/pgtable.h>
4. #include <asm/page.h>
5. static int v2p(unsigned long va)
6. {
7. unsigned long pa = 0;
8. struct task_struct *pcb_tmp;
9. pgd_t *pgd_tmp = NULL;
10. pud_t *pud_tmp = NULL;
11. pmd_t *pmd_tmp = NULL;
12. pte_t *pte_tmp = NULL;
13. printk(KERN_INFO"PAGE_OFFSET = 0x%lx\n",PAGE_OFFSET);
14. printk(KERN_INFO"PGDIR_SHIFT = %d\n",PGDIR_SHIFT);
15. printk(KERN_INFO"PUD_SHIFT = %d\n",PUD_SHIFT);
16. printk(KERN_INFO"PMD_SHIFT = %d\n",PMD_SHIFT);
17. printk(KERN_INFO"PAGE_SHIFT = %d\n",PAGE_SHIFT);
18. printk(KERN_INFO"PTRS_PER_PGD = %d\n",PTRS_PER_PGD);
19. printk(KERN_INFO"PTRS_PER_PUD = %d\n",PTRS_PER_PUD);
20. printk(KERN_INFO"PTRS_PER_PMD = %d\n",PTRS_PER_PMD);
21. printk(KERN_INFO"PTRS_PER_PTE = %d\n",PTRS_PER_PTE);
22. printk(KERN_INFO"PAGE_MASK = 0x%lx\n",PAGE_MASK);
23. pcb_tmp = current;
24. printk(KERN_INFO"pgd = 0x%p\n",pcb_tmp->mm->pgd);
25. if(!find_vma(pcb_tmp->mm,va)){
26. printk(KERN_INFO"virt_addr 0x%lx not available.\n",va);
27. return 0;
28. }
29. pgd_tmp = pgd_offset(pcb_tmp->mm,va);
30. printk(KERN_INFO"pgd_tmp = 0x%p\n",pgd_tmp);
31. printk(KERN_INFO"pgd_val(*pgd_tmp) = 0x%lx\n",pgd_val(*pgd_tmp));
32. if(pgd_none(*pgd_tmp)){
33. printk(KERN_INFO"Not mapped in pgd.\n");
34. return 0;
35. }
36. pud_tmp = pud_offset(pgd_tmp,va);
37. printk(KERN_INFO"pud_tmp = 0x%p\n",pud_tmp);
38. printk(KERN_INFO"pud_val(*pud_tmp) = 0x%lx\n",pud_val(*pud_tmp));
39. if(pud_none(*pud_tmp)){
40. printk(KERN_INFO"Not mapped in pud.\n");
41. return 0;
42. }
43. pmd_tmp = pmd_offset(pud_tmp,va);
44. printk(KERN_INFO"pmd_tmp = 0x%p\n",pmd_tmp);
45. printk(KERN_INFO"pmd_val(*pmd_tmp) = 0x%lx\n",pmd_val(*pmd_tmp));
46. if(pmd_none(*pmd_tmp)){
47. printk(KERN_INFO"Not mapped in pmd.\n");
48. return 0;
49. }
50. pte_tmp = pte_offset_kernel(pmd_tmp,va);
51. printk(KERN_INFO"pte_tmp = 0x%p\n",pte_tmp);
52. printk(KERN_INFO"pte_val(*pte_tmp) = 0x%lx\n",pte_val(*pte_tmp));
53. if(pte_none(*pte_tmp)){
54. printk(KERN_INFO"Not mapped in pte.\n");
55. return 0;
56. }
57. if(!pte_present(*pte_tmp)){
58. printk(KERN_INFO"pte not in RAM.\n");
59. return 0;
60. }
61. pa = (pte_val(*pte_tmp) & PAGE_MASK) |(va & ~PAGE_MASK);
62. printk(KERN_INFO"virt_addr 0x%lx in RAM is 0x%lx .\n",va,pa);
63. printk(KERN_INFO"contect in 0x%lx is 0x%lx\n",pa,
64. *(unsigned long *)((char *)pa + PAGE_OFFSET));
65. return 0;
66. }