3 files changed, 14 insertions, 0 deletions

diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index 4f170932b31b..9489753f9ade 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -194,6 +194,10 @@ static void freebsd4_sendsig(sig_t catcher, int sig, sigset_t *mask,
 long Maxmem = 0;
 long realmem = 0;
 
+#ifdef PAE
+FEATURE(pae, "Physical Address Extensions");
+#endif
+
 #define PHYSMAP_SIZE	(2 * 16)
 
 vm_paddr_t phys_avail[PHYSMAP_SIZE + 2];
diff --git a/sys/kern/kern_mib.c b/sys/kern/kern_mib.c
index 16755d477ed1..319651060722 100644
--- a/sys/kern/kern_mib.c
+++ b/sys/kern/kern_mib.c
@@ -302,6 +302,8 @@ SYSCTL_STRING(_kern, KERN_NISDOMAINNAME, domainname, CTLFLAG_RW,
 u_long hostid;
 SYSCTL_ULONG(_kern, KERN_HOSTID, hostid, CTLFLAG_RW, &hostid, 0, "Host ID");
 
+SYSCTL_NODE(_kern, OID_AUTO, features, CTLFLAG_RD, 0, "Kernel Features");
+
 /*
  * This is really cheating.  These actually live in the libc, something
  * which I'm not quite sure is a good idea anyway, but in order for
diff --git a/sys/sys/sysctl.h b/sys/sys/sysctl.h
index 26ccb9dbb3d3..951c191a1686 100644
--- a/sys/sys/sysctl.h
+++ b/sys/sys/sysctl.h
@@ -305,6 +305,13 @@ TAILQ_HEAD(sysctl_ctx_list, sysctl_ctx_entry);
 	sysctl_add_oid(ctx, parent, nbr, name, (access),			    \
 	ptr, arg, handler, fmt, __DESCR(descr))
 
+/*
+ * A macro to generate a read-only sysctl to indicate the presense of optional
+ * kernel features.
+ */
+#define	FEATURE(name, desc)						\
+	SYSCTL_INT(_kern_features, OID_AUTO, name, CTLFLAG_RD, 0, 1, desc)
+	
 #endif /* _KERNEL */
 
 /*
@@ -597,6 +604,7 @@ TAILQ_HEAD(sysctl_ctx_list, sysctl_ctx_entry);
  */
 extern struct sysctl_oid_list sysctl__children;
 SYSCTL_DECL(_kern);
+SYSCTL_DECL(_kern_features);
 SYSCTL_DECL(_sysctl);
 SYSCTL_DECL(_vm);
 SYSCTL_DECL(_vfs);