On Dec 20 17:48, Ken Brown wrote:
> On 12/20/2024 10:37 AM, Corinna Vinschen wrote:
> > No worries. The expression
> >
> > size_t commit_len = u_len - (start_addr - u_addr);
> >
> > may be right, but it's not generally intelligible. If you'd like
> > to take a stab of changing the code to be more clear, I'm happy.
> I'll give it a try.
>
> By the way, the answer to my original question seems to be remarkably easy.
> The question was whether we could allow mmap with MAP_FIXED to succeed if
> the requested area is contained in an existing anonymous mapping, even if
> the corresponding pages have not been unmapped first. If I'm not mistaken,
> all that's required is to delete the following lines starting at
> mmap.cc:497:
>
> /* First check if the area is unused right now. */
> for (SIZE_T l = 0; l < len; ++l)
> if (MAP_ISSET (off + l))
> {
> set_errno (EINVAL);
> return false;
> }
>
> That seems to work in preliminary testing, but I'll have to test it more
> thoroughly before I'm sure.
>
> If I convince myself that this works, is it OK with you if I commit it (to
> main only) while you're on vacation? That way it can get wider testing, and
> I can always revert it if it breaks something.
Given this is used only for anonymous mappings, go ahead.
Corinna
