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/virtio_disk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/virtio_disk.c') diff --git a/kernel/virtio_disk.c b/kernel/virtio_disk.c index 1a29ce7..6620037 100644 --- a/kernel/virtio_disk.c +++ b/kernel/virtio_disk.c @@ -199,7 +199,7 @@ virtio_disk_rw(struct buf *b) buf0.reserved = 0; buf0.sector = sector; - desc[idx[0]].addr = (uint64) &buf0; + desc[idx[0]].addr = (uint64) kernelpa((uint64) &buf0); desc[idx[0]].len = sizeof(buf0); desc[idx[0]].flags = VRING_DESC_F_NEXT; desc[idx[0]].next = idx[1]; -- cgit v1.2.3