Re: Is the address space of a process continous

[Arjan van de Ven <arjan@infradead.org>]

On Sun, 2005-12-04 at 15:37 -0600, Mohamed El Dawy wrote:
> Hi,
>  I have a question. In the vma_memory_address struct, there are 2
> fields "vm_start" and "vm_end". I was wondering, does the process
> address space include all addresses between those 2 addresses? or
> could there be holes inside this range?
> 
> The main reason I am asking is because I tried to call __follow_page()
> on some of those addresses and got NULL as a result. I am not sure if
> this is a hole, or just a problem with my code!

the kernel does this on demand; eg
user mmaps a range
user touches (read or writes) part of that range

each time the user gets to a page that wasn't touched/used before, the
kernel takes a fault and fills in the address.

if you get nulls it's just pages that haven't been used yet.


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