amd64: Populate the KMSAN shadow maps and integrate with the VM

- During boot, allocate PDP pages for the shadow maps.  The region above
  KERNBASE is currently not shadowed.
- Create a dummy shadow for the vm page array.  For now, this array is
  not protected by the shadow map to help reduce kernel memory usage.
- Grow shadows when growing the kernel map.
- Increase the default kernel stack size when KMSAN is enabled.  As with
  KASAN, sanitizer instrumentation appears to create stack frames large
  enough that the default value is not sufficient.
- Disable UMA's use of the direct map when KMSAN is configured.  KMSAN
  cannot validate the direct map.
- Disable unmapped I/O when KMSAN configured.
- Lower the limit on paging buffers when KMSAN is configured.  Each
  buffer has a static MAXPHYS-sized allocation of KVA, which in turn
  eats 2*MAXPHYS of space in the shadow map.

Reviewed by:	alc, kib
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D31295

1 files changed, 9 insertions, 0 deletions

diff --git a/sys/vm/vm_pager.c b/sys/vm/vm_pager.c
index 640e3d977e99..69f0a2dc2bbb 100644
--- a/sys/vm/vm_pager.c
+++ b/sys/vm/vm_pager.c
@@ -217,6 +217,15 @@ pbuf_zsecond_create(const char *name, int max)
 
 	zone = uma_zsecond_create(name, pbuf_ctor, pbuf_dtor, NULL, NULL,
 	    pbuf_zone);
+
+#ifdef KMSAN
+	/*
+	 * Shrink the size of the pbuf pools if KMSAN is enabled, otherwise the
+	 * shadows of the large KVA allocations eat up too much memory.
+	 */
+	max /= 3;
+#endif
+
 	/*
 	 * uma_prealloc() rounds up to items per slab. If we would prealloc
 	 * immediately on every pbuf_zsecond_create(), we may accumulate too