Can I open the macro "CONFIG_8xx" in function do_page_fault() in file kernel\linux-2.6.14-cgl\arch\ppc\mm\fault.c

[Hema <hema6093@gmail.com>]

Hi All,

For function do_page_fault(), my understanding is that if a "push
stack" actions occurs for a protected area (such as thread stack guard
area protected by "mprotect"), it will come here.

But it seems SIGSEGV can only be sent when CONFIG_8xx is defined. My
CPU is 8541 and I want to open this macro, but I also found there are
sveral parts in the kernel related to this macro. And I'm not sure
about it's impact.

Could any one give some proposals?

Thanks a lot.

Br.
Hema.
----------------------------------------------------------------------------------------
Below is my understanding/comments for the function.

int do_page_fault(struct pt_regs *regs, unsigned long address,
unsigned long error_code)
{
//..............
#if defined(CONFIG_8xx)
[
Comments:
  If MACO CONFIG_8xx is not defined, this part will not be run.  That
means we can not handle this kind of error(access a protected area),
hence SIGSEGV will not be triggered.

]
       /* The MPC8xx seems to always set 0x80000000, which is
        * "undefined".  Of those that can be set, this is the only
        * one which seems bad.
        */
 if (error_code & 0x10000000)
               /* Guarded storage error. */
     goto bad_area;
[  Comments:
  I think the error code defined in PPC platform is  0x10000000, so
goto "bad_area"
]
#endif /* CONFIG_8xx */

//..................
bad_area:
 up_read(&mm->mmap_sem);
 pte_errors++;

 /* User mode accesses cause a SIGSEGV */
 if (user_mode(regs)) {
[ Comments:  Yes, we are user mod, the signal SIGSEGV will be sent
out ]
 _exception(SIGSEGV, regs, code, address);
 trace_kernel_trap_exit();
 return 0;
 }

 return SIGSEGV;

//................