mincore: expose capability presence information

Now that we're tracking capdirty, it might be informative to show
userland.  Once upon a time, we thought this might be part of the
revoker implementation, but now we think it's just diagnostics.

Author: nwf

sys/mips/mips/pmap.c

@@ -3365,6 +3365,8 @@ pmap_mincore(pmap_t pmap, vm_offset_t addr, vm_paddr_t *pap)
 	val = MINCORE_INCORE;
 	if (pte_test(&pte, PTE_D))
 		val |= MINCORE_MODIFIED | MINCORE_MODIFIED_OTHER;
+	if (!pte_test(&pte, PTE_SC))
+		val |= MINCORE_CAPDIRTY;
 	pa = TLBLO_PTE_TO_PA(pte);
 	if (pte_test(&pte, PTE_MANAGED)) {
 		/*

sys/sys/mman.h

@@ -197,6 +197,7 @@
 #define	MINCORE_REFERENCED_OTHER 0x8 /* Page has been referenced */
 #define	MINCORE_MODIFIED_OTHER	0x10 /* Page has been modified */
 #define	MINCORE_SUPER		0x20 /* Page is a "super" page */
+#define	MINCORE_CAPDIRTY	0x40 /* Page may contain capabilities */
 
 /*
  * Anonymous object constant for shm_open().

sys/vm/vm_mmap.c

@@ -1459,6 +1459,20 @@ kern_mincore(struct thread *td, uintptr_t addr0, size_t len,
 				    pmap_is_referenced(m) ||
 				    (m->a.flags & PGA_REFERENCED) != 0)
 					mincoreinfo |= MINCORE_REFERENCED_OTHER;
+
+				/*
+				 * The pmap may have told us that this
+				 * particular mapping is already capdirty,
+				 * and if so don't bother with the more
+				 * elaborate probes and especially not with
+				 * the expensive pmap_is_capdirty.
+				 */
+				if ((mincoreinfo & MINCORE_CAPDIRTY) == 0 &&
+				    ((m->a.flags & PGA_CAPDIRTY) != 0 ||
+				    (m->flags & VPO_FASTCAPDIRTY) != 0 ||
+				    pmap_is_capdirty(m) ||
+				    (m->a.flags & PGA_CAPDIRTY) != 0))
+					mincoreinfo |= MINCORE_CAPDIRTY;
 			}
 			if (object != NULL)
 				VM_OBJECT_WUNLOCK(object);