> As a side note: I hope you use the macros in linux/list.h, so it's not
> a stupid thinko in the list walking code somewhere.
>
Oh! No, I'm not using the macros in linux/list.h. I've used a simple C list.
The definition of this list is:
1. struct mtpmc_wrprotected_pages{
2. unsigned long address;
3. struct mtpmc_wrprotected_pages *next_page;
4. };
5.
6. struct mtpmc_vm_wrprotected{
7. unsigned long vm_start;
8. unsigned long vm_end;
9.
10. struct mtpmc_wrprotected_pages *pages;
11. struct mtpmc_vm_wrprotected *vm_next;
12. };
13.
14. static struct mtpmc_vm_wrprotected *mtpmc_mm_wrprotected;
in which I records the vmas and the corresponding pages that I've
write-protected.
Now I post also the other pieces of code I'm using:
The exception handler function hijacked:
15. static asmlinkage void mtpmc_handler(struct pt_regs * regs,
long error_code)
16. {
17. unsigned long address;
18. struct mm_struct *mm;
19. struct mtpmc_address_fault *temp;
20.
21. unsigned long pid = current->pid;
22. int hijack = 0;
23.
24. /* store the old_exception handler pointer in mtpmc_old_int_handler */
25. void (*mtpmc_old_int_handler)(struct pt_regs *,long) =
(void*)mtpmc_old_handler;
26.
27. /* get the address */
28. __asm__("movl %%cr2,%0":"=r" (address));
29.
30. mm = current->mm;
31. if ((current->pid>=mtpmc_min_pid) && (current->pid<=mtpmc_max_pid))
32. if ((error_code & 3) == 3)
33. if (mtpmc_protected_by_us(address) == 1) /*ERROR IN CALLING THIS
FUNCTION*/
34. {
35. send_sig(SIGSTOP, current, 1);
36. hijack = 1;*/
37. }
38.
39. if (hijack != 1)
40. (*mtpmc_old_int_handler)(regs,error_code);/*call the original handler*/
41.
42. return;
43. }
The line that causes the error is the 33.th, when during the call to the
mtpmc_protected_by_us() function. This function scan the list created by me
in which I store the value of memory pages write-protected by me.
44. #define INSIDE(a, b, c) ( ((c) <= (b)) && ((c) >= (a)) )
45.
46. int mtpmc_protected_by_us(unsigned long addr)
47. {
48. struct mtpmc_vm_wrprotected *wr_vma;
49. struct mtpmc_wrprotected_pages *wr_page;
50.
51. for (wr_vma=mtpmc_mm_wrprotected; wr_vma!=NULL; wr_vma=wr_vma->vm_next)
52. if (INSIDE(wr_vma->vm_start, wr_vma->vm_end, addr)){
53. for (wr_page=wr_vma->pages; wr_page!=NULL; wr_page=wr_page->next_page)
54. if ((addr >= wr_page->address) && (addr <(wr_page->address +
PAGE_SIZE)))
55. return 1;
56. return 0;
57. }
58.
59. return 0;
60. }
I hope these are not too much lines of code and that I've well explained them.
Thanks.
VM
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