I've searched through a lot of resources, but found nothing concrete on the matter:
I know that with some linux systems, a fork() syscall works with copy-on-write; that is, the parent and the child share the same address space, but PTE is now marked read-only, to be used later of COW. when either tries to access a page, a PAGE_FAULT occur and the page is copied to another place, where it can be modified.
However, I cannot understand how the OS reaches the shared PTEs to mark them as "read". I have hypothesized that when a fork() syscall occurs, the OS preforms a "page walk" on the parent's page table and marks them as read-only - but I find no confirmation for this, or any information regarding the process.
Does anyone know how the pages come to be marked as read only? Will appreciate any help. Thanks!