RE: exception handler on memory management

[Vincenzo Mallozzi <vinjunior@xxxxxxxx>]

--- B Srinivas  <b.srinivas@xxxxxxxxxxxx> ha scritto:
> 
> 
> Hi all,
> I'm developing a LKM. I'm working on threads that,
> as
> obvious, share the same process address space. I' ve
> already setted the shared portion of memory as not
> writable.
> Now I've to manage the access to this memory by
> having
> a notification any time a thread tries to write on.
> I think the solution is to change an exception
> handler
> but I've not an idea of what exception handler is
> called when a process tries to write on a "not
> writable" portion of memory...
> 
>> AFAIK it is the page fault handler which is called
>> while traversing the page table.
> 
> Can anyone help me or give me other suggests?
> Thanks.
> Vincenzo.
> 

I know that the page fault handler is the one called
also when a COW occurres. So I've implemented a
function like this:

asmlinkage void cmc_handler(struct pt_regs * regs,long
err_code)
{
  void (*cmc_old_int_handler)(struct pt_regs *,long) =
(void *) cmc_old_handler;
  printk(KERN_DEBUG "Hijacking of page_fault\n");
  (*cmc_old_int_handler)(regs,err_code);
  return;
}

that, later in the module, substitues the
do_page_handler function (cmc_old_handler) in the idt.

I then prove a user mode program by wich I try to
write on a not writable memory region. I try also a
user mode program that do a fork.
Theorically, the "Hijacking of page fault" string must
be returned in these cases, but no string of this type
is returned.
Can anyone suggest me a solution?
Thanks.
Vincenzo Mallozzi.

P.S. What's about general_protection handler?


		
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