Johannes Berg bfc58e2b98 um: remove process stub VMA ... This mostly reverts the old commit 3963333fe6 ("uml: cover stubs with a VMA") which had added a VMA to the existing PTEs. However, there's no real reason to have the PTEs in the first place and the VMA cannot be 'fixed' in place, which leads to bugs that userspace could try to unmap them and be forcefully killed, or such. Also, there's a bit of an ugly hole in userspace's address space. Simplify all this: just install the stub code/page at the top of the (inner) address space, i.e. put it just above TASK_SIZE. The pages are simply hard-coded to be mapped in the userspace process we use to implement an mm context, and they're out of reach of the inner mmap/munmap/mprotect etc. since they're above TASK_SIZE. Getting rid of the VMA also makes vma_merge() no longer hit one of the VM_WARN_ON()s there because we installed a VMA while the code assumes the stack VMA is the first one. It also removes a lockdep warning about mmap_sem usage since we no longer have uml_setup_stubs() and thus no longer need to do any manipulation that would require mmap_sem in activate_mm(). Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: Richard Weinberger <richard@nod.at>		2021-02-12 21:37:38 +01:00
..
Makefile	um: Add SPDX headers for files in arch/um/os-Linux	2019-09-15 21:37:17 +02:00
mem.c	um: rework userspace stubs to not hard-code stub location	2021-02-12 21:35:02 +01:00
process.c	um: remove process stub VMA	2021-02-12 21:37:38 +01:00