the magic in do_page_fault() ???

["liyu@LAN" <liyu@ccoss.com.cn>]

Hi LKML:
  
   I am reading code of memory management. this process is so challengable.

   I have one quetion too.
  
   in do_page_fault() (kernel 2.6.11.11) include one piece of code as 
follow:

 
       if (!down_read_trylock(&mm->mmap_sem)) {
       if ((error_code & 4) == 0 &&
           !search_exception_tables(regs->eip))
           goto bad_area_nosemaphore;
       down_read(&mm->mmap_sem);
   }


   I think I can understand these operations on mm->mmap_sem and 
"error_code&4".
but how "search_exception_tables(regs->eip)" work here?

   In "Understanding Linux kernel 2ed" book,  the author say , kernel 
must difference two case:
  
     1. kernel memory access problem.
     2. Arguments of system call include address of memeory unit is 
unmapped.

   Well, That is OK. but I want to know what 's mechanism in it ?
  
   3ks. (in Chinese , number 3 read as 'th' :)


                                                            liyu
                                                               Mon Jul  
4 13:23:24 CST 2005     
  




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