Index: sys/kern/imgact_elf.c
===================================================================
--- sys/kern/imgact_elf.c
+++ sys/kern/imgact_elf.c
@@ -1533,33 +1533,58 @@
 }
 
 static int
-core_output(void *base, size_t len, off_t offset, struct coredump_params *p,
+core_output(char *base, size_t len, off_t offset, struct coredump_params *p,
     void *tmpbuf)
 {
-	int error;
+	vm_map_t map;
+	struct mount *mp;
+	size_t runlen;
+	int error, error1;
 
 	if (p->comp != NULL)
 		return (compress_chunk(p, base, tmpbuf, len));
 
-	/*
-	 * EFAULT is a non-fatal error that we can get, for example,
-	 * if the segment is backed by a file but extends beyond its
-	 * end.
-	 */
-	error = core_write(p, base, len, offset, UIO_USERSPACE);
-	if (error == EFAULT) {
-		log(LOG_WARNING, "Failed to fully fault in a core file segment "
-		    "at VA %p with size 0x%zx to be written at offset 0x%jx "
-		    "for process %s\n", base, len, offset, curproc->p_comm);
-
+	map = &p->td->td_proc->p_vmspace->vm_map;
+	do {
 		/*
-		 * Write a "real" zero byte at the end of the target region
-		 * in the case this is the last segment.
-		 * The intermediate space will be implicitly zero-filled.
+		 * Attempt to page in all virtual pages in the range.  If a
+		 * virtual page is not backed by the pager, it is represented as
+		 * a hole in the file.  This can occur with zero-filled
+		 * anonymous memory or truncated files, for example.
 		 */
-		error = core_write(p, zero_region, 1, offset + len - 1,
-		    UIO_SYSSPACE);
-	}
+		for (runlen = 0; runlen < len; runlen += PAGE_SIZE) {
+			error1 = vm_fault(map, (uintptr_t)base + runlen,
+			    VM_PROT_READ | VM_PROT_FAULT_NOFILL,
+			    VM_FAULT_NORMAL, NULL);
+			if (runlen == 0)
+				error = error1;
+			else if (error != error1)
+				break;
+		}
+
+		if (error == KERN_SUCCESS) {
+			error = core_write(p, base, runlen, offset,
+			    UIO_USERSPACE);
+			if (error != 0)
+				break;
+		} else {
+			error = vn_start_write(p->vp, &mp, V_WAIT);
+			if (error != 0)
+				break;
+			vn_lock(p->vp, LK_EXCLUSIVE | LK_RETRY);
+			error = vn_truncate_locked(p->vp, offset + runlen,
+			    false, p->td->td_ucred);
+			VOP_UNLOCK(p->vp);
+			vn_finished_write(mp);
+			if (error != 0)
+				break;
+		}
+
+		base += runlen;
+		offset += runlen;
+		len -= runlen;
+	} while (len > 0);
+
 	return (error);
 }
 
Index: sys/vm/vm.h
===================================================================
--- sys/vm/vm.h
+++ sys/vm/vm.h
@@ -80,9 +80,11 @@
 #define	VM_PROT_WRITE		((vm_prot_t) 0x02)
 #define	VM_PROT_EXECUTE		((vm_prot_t) 0x04)
 #define	VM_PROT_COPY		((vm_prot_t) 0x08)	/* copy-on-read */
-#define	VM_PROT_PRIV_FLAG	((vm_prot_t) 0x10)
-#define	VM_PROT_FAULT_LOOKUP	VM_PROT_PRIV_FLAG
-#define	VM_PROT_QUICK_NOFAULT	VM_PROT_PRIV_FLAG	/* same to save bits */
+#define	VM_PROT_PRIV_FLAG1	((vm_prot_t) 0x10)
+#define	VM_PROT_PRIV_FLAG2	((vm_prot_t) 0x20)
+#define	VM_PROT_FAULT_LOOKUP	VM_PROT_PRIV_FLAG1
+#define	VM_PROT_QUICK_NOFAULT	VM_PROT_PRIV_FLAG1	/* same to save bits */
+#define	VM_PROT_FAULT_NOFILL	VM_PROT_PRIV_FLAG2
 
 #define	VM_PROT_ALL		(VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE)
 #define VM_PROT_RW		(VM_PROT_READ|VM_PROT_WRITE)
Index: sys/vm/vm_fault.c
===================================================================
--- sys/vm/vm_fault.c
+++ sys/vm/vm_fault.c
@@ -1476,6 +1476,12 @@
 		 */
 		if (vm_fault_next(&fs))
 			continue;
+		if ((fs.fault_type & VM_PROT_FAULT_NOFILL) != 0) {
+			if (fs.first_object == fs.object)
+				fault_page_free(&fs.first_m);
+			unlock_and_deallocate(&fs);
+			return (KERN_RESTART);
+		}
 		VM_OBJECT_WUNLOCK(fs.object);
 		vm_fault_zerofill(&fs);
 		/* Don't try to prefault neighboring pages. */