Hello Stephan,
uvm_deallocate is a wrapper for uvm_unmap. It calls unmap after checking
3 things:
- size is not 0
- address starts at a page. If not, it is rounded
- address + size is at the end of a page, otherwise, size is also rounded
A thing to look out for here is that unmap takes a pointer to the end
while deallocate uses the size instead and it is not possible to set the
flags using deallocate.
From what I understand in regard to sys_shmdt (sysv_shm.c), the address
in this case cannot be influenced by the user/userland. This would make
the checks introduced by deallocate not necessary.
Kind regards
Am 13.01.25 um 14:06 schrieb Stephan:
Hello,
what is the difference between uvm_unmap() and uvm_deallocate()?
It does not become clear to me from what is written in uvm_map(9):
uvm_unmap() removes a valid mapping, from start to end, in map map, which
must be unlocked.
uvm_deallocate() deallocates kernel memory in map map from address start
to start + size.
uvm_deallocate() is used e.g. in sysv_shm.c, in which case I would
have expected uvm_unmap().
Thanks,
Stephan
