new type: ptraddr_t

ptraddr_t is an unsigned integer type that can hold the address of any
pointer.  It differes from uintptr_t in that it does not carry
provenance which is useful for CHERI in that it can disambigurate the
provenance of uintptr_t expressions.  It differes from size_t in that
some segmented architecture (not supported by FreeBSD) may have a size_t
that does not hold an address.

ptraddr_t is not yet standardized, but is currently proposed for
inclusion in C++2Y.

Prefer the compiler defined __PTRADDR_TYPE__ defintion where available
as this a new type and we don't need to worry about historical values.
Fall back to __size_t where unavailable.

Reviewed by:	kib, markj
Effort:		CHERI upstreaming
Sponsored by:	Innovate UK
Differential Revision:	https://reviews.freebsd.org/D53817

3 files changed, 17 insertions, 2 deletions

diff --git a/share/man/man7/arch.7 b/share/man/man7/arch.7
index 5170a27768b8..628d3837f011 100644
--- a/share/man/man7/arch.7
+++ b/share/man/man7/arch.7
@@ -24,7 +24,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd October 1, 2025
+.Dd November 27, 2025
 .Dt ARCH 7
 .Os
 .Sh NAME
@@ -48,7 +48,8 @@ and later, unless otherwise noted.
 .Fx
 uses a flat address space.
 Variables of types
-.Vt unsigned long
+.Vt unsigned long ,
+.Vt ptraddr_t ,
 and
 .Vt size_t
 have the same representation.
diff --git a/sys/sys/_types.h b/sys/sys/_types.h
index 6b70b8dc6e32..6e69b06f689d 100644
--- a/sys/sys/_types.h
+++ b/sys/sys/_types.h
@@ -103,6 +103,12 @@ typedef	__int32_t	__ptrdiff_t;	/* ptr1 - ptr2 */
 #error unsupported ptrdiff_t size
 #endif
 
+#ifdef __PTRADDR_TYPE__
+typedef	__PTRADDR_TYPE__	__ptraddr_t;
+#else
+typedef	__size_t		__ptraddr_t;
+#endif
+
 /*
  * Target-dependent type definitions.
  */
diff --git a/sys/sys/stddef.h b/sys/sys/stddef.h
index 73636f5a2370..90186eed7624 100644
--- a/sys/sys/stddef.h
+++ b/sys/sys/stddef.h
@@ -32,6 +32,14 @@
 #include <sys/cdefs.h>
 #include <sys/_null.h>
 #include <sys/_types.h>
+#include <sys/_visible.h>
+
+#if __BSD_VISIBLE
+#ifndef _PTRADDR_T_DECLARED
+typedef	__ptraddr_t	ptraddr_t;
+#define	_PTRADDR_T_DECLARED
+#endif
+#endif
 
 #ifndef _PTRDIFF_T_DECLARED
 typedef	__ptrdiff_t	ptrdiff_t;