Re: MAP_FIXED for ELF mappings

[Oleg Nesterov]

On 10/04, Michal Hocko wrote:
>
> On Wed 04-10-17 23:12:38, Baoquan He wrote:
> >  	if (total_size) {
> >  		total_size = ELF_PAGEALIGN(total_size);
> > -		map_addr = vm_mmap(filep, addr, total_size, prot, flags, off);
> > -		if (!BAD_ADDR(map_addr))
> > -			vm_munmap(map_addr+size, total_size-size);
> > -	} else
> > -		map_addr = vm_mmap(filep, addr, size, prot, flags, off);
> > +		addr = get_unmapped_area(file, addr, total_size, off, flags);
>
> So how does this prevent clobbering an existing VMA when flags contains
> MAP_FIXED?

I got lost...

this is just cleanup, it should not change the behaviour, with or without
MAP_FIXED. It just avoids the mmap(total_size) + munmap(extra_size).

Oleg.