[okl4-developer] Roottask pagefault

[Nelson Tam]

Hi Ryan,

On 20/02/2008, at 18:37, Ryan Heffernan wrote:

> vbase is 0xa4000000, vend is 0xcfffffff
> addr is 0xa4000000, vbase is 0xa4000000
> roottask read pagefault at 33cc33c8, ip=800023e0 - deny

In addition to what Geoff said, the pointer that Iguana is  
dereferencing looks like it was taken from uninitialised bss.   
Normally the bootloader should zero-out the bss, and passing a pointer  
from a properly-initialised bss would yield a NULL pointer which will  
be caught by get_pd(), thus avoiding the bogus pagefault you're seeing.

Can you check whether your bss is initialised properly?  Although this  
is the responsibility of the bootloader to zero-out memory within the  
nobits sections of an elf file, sometimes lousy bootloaders don't do  
that, and you have to do tricks within the elf file to make sure the  
memory is zeroed.  What we do here is manipulate the elf so that  
nobits sections are replaced by progbits sections that contain all  
zeros.

For now probably the easiest way is to get OKL4 to manually zero-out  
the bss during system bootup.

Nelson.