Re: 2.6.11-rc3: Kylix application no longer works?

[Daniel Jacobowitz <dan@debian.org>]

On Tue, Feb 08, 2005 at 06:10:18PM -0800, Andrew Morton wrote:
> We could just remove the printk and stick a comment over it.  If the
> application later tries to access the not-there pages then it'll just
> fault.
> 
> However I worry if there is some way in which we can leave unzeroed memory
> accessible to the application, although it's hard to see how that could
> happen.
> 
> Daniel, Pavel cruelly chopped you off the Cc when replying.  What's your
> diagnosis on the below?

It's asking for a lot of unwritable zeroed space.  See this:

>   LOAD           0x000000 0x08048000 0x08048000 0xb7354 0x1b7354 R E 0x1000
>   LOAD           0x0b7354 0x08200354 0x08200354 0x1e3e4 0x1f648 RW  0x1000

The 0xb7354 is size to map from the file, the 0x1b7354 is size to map
in memory.  We're supposed to zero-fill the rest.  Now that I think
about it I can see why this is a problem - the kernel probably assumes
that any segment with MemSiz > FileSiz will be writable.  Certainly
it's a bit weird for the app to request unwritable zeroed pages.

clear_user's probably not the right way to provide the extra zeroing.

-- 
Daniel Jacobowitz
CodeSourcery, LLC