elfctl: allow features to be specified by value

This will allow elfctl on older releases to set bits that are not yet
known there, so that the binary will have the correct settings applied
if run on a later FreeBSD version.

PR:		252629 (related)
Suggested by:	kib
Reviewed by:	gbe (manpage, earlier), kib
MFC after:	3 days
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D28284

2 files changed, 35 insertions, 5 deletions

diff --git a/usr.bin/elfctl/elfctl.1 b/usr.bin/elfctl/elfctl.1
index f93b558fdf0d..23e2dabea49c 100644
--- a/usr.bin/elfctl/elfctl.1
+++ b/usr.bin/elfctl/elfctl.1
@@ -26,7 +26,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 12, 2021
+.Dd January 22, 2021
 .Dt ELFCTL 1
 .Os
 .Sh NAME
@@ -64,7 +64,8 @@ to turn on the features,
 to turn off the features,
 .Dq Li =
 to only turn on the given features.
-A comma separated list of feature names follows the operation.
+A comma separated list of feature names or numeric values follows the
+operation.
 .El
 .Pp
 If
@@ -86,6 +87,16 @@ command:
 elfctl file
 elfctl -e +aslr file
 .Ed
+.Pp
+Features may be specified as numerical values:
+.Bd -literal -offset -indent
+elfctl -e =0x0001,0x0004 file
+.Ed
+.Pp
+Features may also be specified as a single combined value:
+.Bd -literal -offset -indent
+elfctl -e =0x5 file
+.Ed
 .Sh HISTORY
 .Nm
 first appeared in
diff --git a/usr.bin/elfctl/elfctl.c b/usr.bin/elfctl/elfctl.c
index 20a2c5b95444..f641b63e32bd 100644
--- a/usr.bin/elfctl/elfctl.c
+++ b/usr.bin/elfctl/elfctl.c
@@ -33,7 +33,9 @@
 #include <sys/endian.h>
 #include <sys/stat.h>
 
+#include <ctype.h>
 #include <err.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <gelf.h>
 #include <getopt.h>
@@ -245,9 +247,26 @@ convert_to_feature_val(char *feature_str, uint32_t *feature_val)
 			}
 		}
 		if (i == len) {
-			warnx("%s is not a valid feature", feature);
-			if (!iflag)
-				return (false);
+			if (isdigit(feature[0])) {
+				char *eptr;
+				long val;
+
+				errno = 0;
+				val = strtol(feature, &eptr, 0);
+				if (eptr == feature || *eptr != '\0')
+					errno = EINVAL;
+				else if (val > UINT_MAX)
+					errno = ERANGE;
+				if (errno != 0) {
+					warn("%s invalid", feature);
+					return (false);
+				}
+				input != val;
+			} else {
+				warnx("%s is not a valid feature", feature);
+				if (!iflag)
+					return (false);
+			}
 		}
 	}