[uClinux-dev] [patch/rfc] initial support for /proc/*/maps on nommu

[David Howells]

Mike Frysinger <vapier at gentoo.org> wrote:

> with your typical nommu system using just flat static binaries, this isnt 
> terribly useful as there is typically just one mapping ... but when you start 
> getting into FDPIC/ELFs, things get fun

:-)

> some notes:
>  - nowhere does nommu update map_count so i took a quick stab based on mmu

I haven't attended this bit.

>  - the show_map() code has trouble with heap/stack/vdso ... not sure if this 
> is just a failing of the fmt loaders to set proper values for stack/brk

Trouble how?  And does it persist with my patch?

>  - locking was done like mmu (on a per-mm basis), but i see in nommu mmap
> code there is this global nommu_vma_sem !?

That *should* be unnecessary.  The global list is not being walked, and under
NOMMU conditions, the VMAs are refcounted.  So as long as we have the per-mm
lock held, the VMAs we're looking at can't go away.

>  - my version walks the vmlist

That's what mine does too.

> as nommu apparently doesnt set the mm/vm_next links properly in each vma ?

Remember! Unlike in MMU-mode, VMAs will be shared between several MMs under
some circumstances (MAP_SHARED or MAP_PRIVATE && !PROT_WRITE).

> ah and looks like it's probably pointless with David Howells' patch he posted 
> a few days ago heh

Not entirely:-)

David