Copy on write vs illegal access

Question

在Linux内核中，当进程尝试访问只读页面时，页面错误处理程序如何区分写时复制机制和非法内存访问？

Answer 1

arch/<arch>/mm/fault.c的do_page_fault()函数arch/<arch>/mm/fault.c “多路分解”发生页面错误的各种原因，并将控制权传递给适当的处理程序。

Answer 2

If the faulting page is in the userspace region of the address space, the page fault handler looks up the memory map of the current task. If the page is within a writable VMA (and the fault is a write fault) then it knows that it's a COW fault.