mmap() doesn't zero the last page

[zooey]

According to POSIX, mmap() is supposed to fill the area in the last page that is not "covered" by the mapped file with zeros.

Our mmap does not do this, which causes gcc's fixincl program to crash, as it relies on these zeros to be there in order to invoke strlen(). If there's no zero in the "empty" area of the last page, strlen will try to access the following page and segfault.

The current implementation seems to just read the corresponding BFS block(s) until all pages have been filled, as fixincl always crashes with the same file, but will not crash on a copy of that file (which obviously happens to have a trailing zero somewhere).

This is with hrev31642.

[bonefish]

BFS (respectively any FS) isn't reponsible for clearing the unused part of the last page. At least that was the idea. ATM VMVnodeCache::Read() (the VM subsystem's interface to mapped files) clears the respective memory, but the file cache (respectively the VFS functions it uses) doesn't as far as I can see.

[axeld]

Fixed in hrev31669.

[zooey]

Reopening, since the problem is still present.

I'm going to attach a little test program, which exposes the bug.

[andreasf]

This could explain some weird Mono behavior I encountered...

[axeld]

This is actually a different bug with the same outcome, though; it should only affect the truncation case.

[axeld]

Fixed in hrev31732, and thanks for the test app!