On Tue, Apr 29, 2025 at 09:28:05AM +0200, Vlastimil Babka wrote: > On 4/28/25 17:28, Lorenzo Stoakes wrote: > > Currently VMA allocation, freeing and duplication exist in kernel/fork.c, > > which is a violation of separation of concerns, and leaves these functions > > exposed to the rest of the kernel when they are in fact internal > > implementation details. > > > > Resolve this by moving this logic to mm, and making it internal to vma.c, > > vma.h. > > > > This also allows us, in future, to provide userland testing around this > > functionality. > > > > We additionally abstract dup_mmap() to mm, being careful to ensure > > kernel/fork.c acceses this via the mm internal header so it is not exposed > > elsewhere in the kernel. > > > > As part of this change, also abstract initial stack allocation performed in > > __bprm_mm_init() out of fs code into mm via the create_init_stack_vma(), as > > this code uses vm_area_alloc() and vm_area_free(). > > > > In order to do so sensibly, we introduce a new mm/vma_exec.c file, which > > contains the code that is shared by mm and exec. This file is added to both > > memory mapping and exec sections in MAINTAINERS so both sets of maintainers > > can maintain oversight. > > Note that kernel/fork.c itself belongs to no section. Maybe we could put it > somewhere too, maybe also multiple subsystems? I'm thinking something > between MM, SCHEDULER, EXEC, perhaps PIDFD? Thanks, indeed I was wondering about where this should be, and the fact we can put stuff in multiple places is actually pretty powerful! This is on my todo, will take a look at this.
