New mmap(2) flag: MAP_CONCEAL.

MAP_CONCEAL'd memory is not written to disk in the event of a core dump.
It may grow other qualities in the future.

Wanted by libressl, probably useful elsewhere, too.

Prompted by deraadt@, concept from deraadt@/kettenis@.  With input from
deraadt@, cjeker@, kettenis@, otto@, bcook@, matthew@, guenther@, djm@,
and tedu@.

ok otto@ deraadt@

6 files changed, 24 insertions, 9 deletions

diff --git a/sys/sys/mman.h b/sys/sys/mman.h
index a75b2069ba5..47972b5ea88 100644
--- a/sys/sys/mman.h
+++ b/sys/sys/mman.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mman.h,v 1.33 2019/01/11 18:46:30 deraadt Exp $	*/
+/*	$OpenBSD: mman.h,v 1.34 2019/03/01 01:46:18 cheloha Exp $	*/
 /*	$NetBSD: mman.h,v 1.11 1995/03/26 20:24:23 jtc Exp $	*/
 
 /*-
@@ -60,8 +60,9 @@
 #define	MAP_ANONYMOUS	MAP_ANON	/* alternate POSIX spelling */
 #define	__MAP_NOFAULT	0x2000
 #define	MAP_STACK	0x4000	/* mapping is used for a stack */
+#define	MAP_CONCEAL	0x8000	/* omit from dumps */
 
-#define	MAP_FLAGMASK	0x7ff7
+#define	MAP_FLAGMASK	0xfff7
 
 #ifndef _KERNEL
 /*
diff --git a/sys/uvm/uvm.h b/sys/uvm/uvm.h
index 7a93862dd97..c895eb5ea1d 100644
--- a/sys/uvm/uvm.h
+++ b/sys/uvm/uvm.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm.h,v 1.63 2018/10/31 08:50:25 kettenis Exp $	*/
+/*	$OpenBSD: uvm.h,v 1.64 2019/03/01 01:46:18 cheloha Exp $	*/
 /*	$NetBSD: uvm.h,v 1.24 2000/11/27 08:40:02 chs Exp $	*/
 
 /*
@@ -90,6 +90,7 @@ struct uvm {
 #define UVM_ET_NOFAULT		0x0020	/* don't fault */
 #define UVM_ET_STACK		0x0040	/* this is a stack */
 #define UVM_ET_WC		0x0080	/* write combining */
+#define UVM_ET_CONCEAL		0x0100	/* omit from dumps */
 #define UVM_ET_FREEMAPPED	0x8000	/* map entry is on free list (DEBUG) */
 
 #define UVM_ET_ISOBJ(E)		(((E)->etype & UVM_ET_OBJ) != 0)
@@ -100,6 +101,7 @@ struct uvm {
 #define UVM_ET_ISNOFAULT(E)	(((E)->etype & UVM_ET_NOFAULT) != 0)
 #define UVM_ET_ISSTACK(E)	(((E)->etype & UVM_ET_STACK) != 0)
 #define UVM_ET_ISWC(E)		(((E)->etype & UVM_ET_WC) != 0)
+#define UVM_ET_ISCONCEAL(E)	(((E)->etype & UVM_ET_CONCEAL) != 0)
 
 #ifdef _KERNEL
 
diff --git a/sys/uvm/uvm_extern.h b/sys/uvm/uvm_extern.h
index a473f251229..24ddcd98ccd 100644
--- a/sys/uvm/uvm_extern.h
+++ b/sys/uvm/uvm_extern.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_extern.h,v 1.144 2018/10/31 08:50:25 kettenis Exp $	*/
+/*	$OpenBSD: uvm_extern.h,v 1.145 2019/03/01 01:46:18 cheloha Exp $	*/
 /*	$NetBSD: uvm_extern.h,v 1.57 2001/03/09 01:02:12 chs Exp $	*/
 
 /*
@@ -112,7 +112,8 @@ typedef int		vm_prot_t;
 #define UVM_FLAG_NOFAULT 0x0800000 /* don't fault */
 #define UVM_FLAG_UNMAP   0x1000000 /* unmap to make space */
 #define UVM_FLAG_STACK   0x2000000 /* page may contain a stack */
-#define UVM_FLAG_WC      0x4000000 /* write combining */ 
+#define UVM_FLAG_WC      0x4000000 /* write combining */
+#define UVM_FLAG_CONCEAL 0x8000000 /* omit from dumps */
 
 /* macros to extract info */
 #define UVM_PROTECTION(X)	((X) & PROT_MASK)
diff --git a/sys/uvm/uvm_map.c b/sys/uvm/uvm_map.c
index fcb6e16b43f..ac9309edc89 100644
--- a/sys/uvm/uvm_map.c
+++ b/sys/uvm/uvm_map.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_map.c,v 1.241 2019/02/15 16:46:59 deraadt Exp $	*/
+/*	$OpenBSD: uvm_map.c,v 1.242 2019/03/01 01:46:18 cheloha Exp $	*/
 /*	$NetBSD: uvm_map.c,v 1.86 2000/11/27 08:40:03 chs Exp $	*/
 
 /*
@@ -1081,6 +1081,8 @@ uvm_mapanon(struct vm_map *map, vaddr_t *addr, vsize_t sz,
 		if ((flags & UVM_FLAG_OVERLAY) == 0)
 			entry->etype |= UVM_ET_NEEDSCOPY;
 	}
+	if (flags & UVM_FLAG_CONCEAL)
+		entry->etype |= UVM_ET_CONCEAL;
 	if (flags & UVM_FLAG_OVERLAY) {
 		KERNEL_LOCK();
 		entry->aref.ar_pageoff = 0;
@@ -1350,6 +1352,8 @@ uvm_map(struct vm_map *map, vaddr_t *addr, vsize_t sz,
 		if ((flags & UVM_FLAG_OVERLAY) == 0)
 			entry->etype |= UVM_ET_NEEDSCOPY;
 	}
+	if (flags & UVM_FLAG_CONCEAL)
+		entry->etype |= UVM_ET_CONCEAL;
 	if (flags & UVM_FLAG_OVERLAY) {
 		entry->aref.ar_pageoff = 0;
 		entry->aref.ar_amap = amap_alloc(sz, M_WAITOK, 0);
diff --git a/sys/uvm/uvm_mmap.c b/sys/uvm/uvm_mmap.c
index 48d23f3880c..b667730e388 100644
--- a/sys/uvm/uvm_mmap.c
+++ b/sys/uvm/uvm_mmap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_mmap.c,v 1.153 2019/01/11 18:46:30 deraadt Exp $	*/
+/*	$OpenBSD: uvm_mmap.c,v 1.154 2019/03/01 01:46:18 cheloha Exp $	*/
 /*	$NetBSD: uvm_mmap.c,v 1.49 2001/02/18 21:19:08 chs Exp $	*/
 
 /*
@@ -284,7 +284,6 @@ sys_mmap(struct proc *p, void *v, register_t *retval)
 			return (EINVAL);
 		if (vm_min_address > 0 && addr < vm_min_address)
 			return (EINVAL);
-
 	}
 
 	/* check for file mappings (i.e. not anonymous) and verify file. */
@@ -911,6 +910,8 @@ uvm_mmapanon(vm_map_t map, vaddr_t *addr, vsize_t size, vm_prot_t prot,
 		uvmflag |= UVM_FLAG_OVERLAY;
 	if (flags & MAP_STACK)
 		uvmflag |= UVM_FLAG_STACK;
+	if (flags & MAP_CONCEAL)
+		uvmflag |= UVM_FLAG_CONCEAL;
 
 	/* set up mapping flags */
 	uvmflag = UVM_MAPFLAG(prot, maxprot,
@@ -1019,6 +1020,8 @@ uvm_mmapfile(vm_map_t map, vaddr_t *addr, vsize_t size, vm_prot_t prot,
 		uvmflag |= (UVM_FLAG_NOFAULT | UVM_FLAG_OVERLAY);
 	if (flags & MAP_STACK)
 		uvmflag |= UVM_FLAG_STACK;
+	if (flags & MAP_CONCEAL)
+		uvmflag |= UVM_FLAG_CONCEAL;
 
 	/* set up mapping flags */
 	uvmflag = UVM_MAPFLAG(prot, maxprot,
diff --git a/sys/uvm/uvm_unix.c b/sys/uvm/uvm_unix.c
index 0a6c89c5390..4618ce03559 100644
--- a/sys/uvm/uvm_unix.c
+++ b/sys/uvm/uvm_unix.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_unix.c,v 1.64 2017/03/09 20:27:41 guenther Exp $	*/
+/*	$OpenBSD: uvm_unix.c,v 1.65 2019/03/01 01:46:18 cheloha Exp $	*/
 /*	$NetBSD: uvm_unix.c,v 1.18 2000/09/13 15:00:25 thorpej Exp $	*/
 
 /*
@@ -227,6 +227,10 @@ uvm_should_coredump(struct proc *p, struct vm_map_entry *entry)
 	if ((entry->protection & PROT_READ) == 0)
 		return 0;
 
+	/* Skip ranges excluded from coredumps. */
+	if (UVM_ET_ISCONCEAL(entry))
+		return 0;
+
 	/* Don't dump mmaped devices. */
 	if (entry->object.uvm_obj != NULL &&
 	    UVM_OBJ_IS_DEVICE(entry->object.uvm_obj))