From 91566327012cad2ca99df47f9321dfc012d8a7ff Mon Sep 17 00:00:00 2001 From: Frans Kaashoek Date: Fri, 19 Jul 2019 08:38:51 -0400 Subject: One way of supporting a guard page below kstack: allocate kstacks in procinit() and map them high up (below TRAMPOLNE) with an empty mapping below each stack. Never free a kernel stack. Another way would be to allocate and map them dynamically, but then we need to reload page table when switching processes in scheduler() and/or have a kernel pagetable per proc (if we want k->stack to be the same virtual address in each process). One gotcha: kernel addresses are not equal to physical addresses for stack addresses. A stack address must be translated if we need its physical address (e.g., virtio passes a stack address to the disk). --- kernel/defs.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel/defs.h') diff --git a/kernel/defs.h b/kernel/defs.h index bd89af0..3172cb3 100644 --- a/kernel/defs.h +++ b/kernel/defs.h @@ -193,6 +193,8 @@ uint64 walkaddr(pagetable_t, uint64); int copyout(pagetable_t, uint64, char *, uint64); int copyin(pagetable_t, char *, uint64, uint64); int copyinstr(pagetable_t pagetable, char *dst, uint64 srcva, uint64 max); +char* map_kstack(); +uint64 kernelpa(uint64); // plic.c void plicinit(void); -- cgit v1.2.3