On 8/23/05, Vincenzo Mallozzi <vinjunior@xxxxxxxx> wrote:
> Hi all,
> as I've already described in other mails, I'm hijacking the page fault handler
> function. All works well but there's a little problem.
> To show the problem, I post the code of my handler with I replace the original
> handler.
>
> A preliminary statement:
> mtpmc_old_handler contains the address of the original handler
>
> 1. static asmlinkage void mtpmc_handler(struct pt_regs * regs,long
> error_code)
> 2. {
> 3. unsigned long address;
> 4. struct task_struct *task;
> 5. struct mm_struct *mm;
>
> 6. pid_t pid = current->pid;
> 7. int hijack = 0;
>
> 8. /* gets the address */
> 9. __asm__("movl %%cr2,%0":"=r" (address));
>
> 10. if (the error is a writing error on one of the pages that we've setted
> as not writable)
> 11. {
> 12. printk(KERN_DEBUG "page fault handling\n");
> 13. send_sig(SIGSTOP, current, 1);
> 14. mtpmc_restore_page_writable(current->mm, address);
> 15. mtpmc_restore_page_not_writable(current->mm, address);
for this, its important to know what exactly you are doing in these
two function, can you paste the code of these functions, I think these
are function of your module.
regards,
-Gaurav
> 16. hijack = 1;
> 17. }
>
> 18. if (hijack != 1)
> 19. (*mtpmc_old_int_handler)(regs,error_code);
>
> 20. return;
> 21. }
>
> Note the line 14 and 15. These lines, respectively, make the page at the given
> address first as writable and then as not writable. The result should be the
> same by deleting them and let the page that cause page fault remain not
> writable.
> But if I delete lines 14 and 15,, in the moment of a page fault the system
> blocks. If I don't delete them, instead, all works very well.
> I don't understand why it happens.
> Vincenzo Mallozzi,
>
>
>
>
>
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