pkru: Fix handling of 1GB largepage mappings

pmap_pkru_update_range() did not handle the case where a PDPE has PG_PS
set.  More generally, the SET_PKRU and CLEAR_PKRU sysarch
implementations did not check whether the request covers a "boundary" vm
map entry.  Fix this, add the missing PG_PS test, and add some tests.

Approved by:	so
Security:	FreeBSD-SA-26:11.amd64
Security:	CVE-2026-6386
Reported by:	Nicholas Carlini <npc@anthropic.com>
Reviewed by:	kib, alc
Differential Revision:	https://reviews.freebsd.org/D56184

1 files changed, 32 insertions, 0 deletions

diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
index 28cf309f86c3..9df3fa44ba18 100644
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -4136,6 +4136,38 @@ vm_map_check_protection(vm_map_t map, vm_offset_t start, vm_offset_t end,
 }
 
 /*
+ * Check whether the specified range partially overlaps a map entry with
+ * fixed boundaries, and return false if so.
+ *
+ * The map must be locked.
+ */
+bool
+vm_map_check_boundary(vm_map_t map, vm_offset_t start, vm_offset_t end)
+{
+	vm_map_entry_t entry;
+	int bdry_idx;
+
+	if (!vm_map_range_valid(map, start, end))
+		return (false);
+	if (start == end)
+		return (true);
+
+	if (vm_map_lookup_entry(map, start, &entry)) {
+		bdry_idx = MAP_ENTRY_SPLIT_BOUNDARY_INDEX(entry);
+		if (bdry_idx != 0 &&
+		    (start & (pagesizes[bdry_idx] - 1)) != 0)
+			return (false);
+	}
+	if (vm_map_lookup_entry(map, end - 1, &entry)) {
+		bdry_idx = MAP_ENTRY_SPLIT_BOUNDARY_INDEX(entry);
+		if (bdry_idx != 0 &&
+		    (end & (pagesizes[bdry_idx] - 1)) != 0)
+			return (false);
+	}
+	return (true);
+}
+
+/*
  *
  *	vm_map_copy_swap_object:
  *