dlopen(1): a program that dlopens its arguments

Attempts to dlopen each command line argument then sleeps.  This allows
trivial demonstration of the impact of loading various libraries without
the need to write custom code.

Author: brooksdavis

bin/Makefile

@@ -9,6 +9,7 @@ SUBDIR= cat \
 	date \
 	dd \
 	df \
+	dlopen \
 	domainname \
 	echo \
 	ed \

bin/dlopen/Makefile

@@ -0,0 +1,6 @@
+PACKAGE=runtime
+PROG=	dlopen
+
+LIBADD=	util
+
+.include <bsd.prog.mk>

bin/dlopen/dlopen.1

@@ -0,0 +1,66 @@
+.\"-
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.\" Copyright (c) 2025 (holder)
+.\"
+.\" This software was developed by SRI International, the University of
+.\" Cambridge Computer Laboratory (Department of Computer Science and
+.\" Technology), and Capabilities Limited under Defense Advanced Research
+.\" Projects Agency (DARPA) Contract No. FA8750-24-C-B047 ("DEC").
+.\"
+.Dd February 25, 2025
+.Dt DLOPEN 1
+.Os
+.Sh Name
+.Nm dlopen
+.Nd load libraries with dlopen(3) and sleep for analysis
+.Sh SYNOPSIS
+.Nm
+.Op Brq Fl L | Fl N
+.Op Brq Fl g | Fl l
+.Op Fl v
+.Op Fl s Ar seconds
+.Ar library ...
+.Sh DESCRIPTION
+The
+.Nm
+utility supports analysis of the linkage and loading behavior of dynamiclly
+loaded libraries without the need for custom software.
+It loads each library listed on the command line and then sleeps for a
+number of second specified by the
+.Fl s
+argument (999999 by default).
+.Pp
+The
+.Fl L
+and
+.Fl N
+flags control the use of
+.Dv RTLD_LAZY
+vs
+.Dv RTLD_NOW
+flags.
+.Dv RTLD_NOW is
+the
+.Nm
+utility's default.
+Likewise
+.Fl g
+and
+.Fl l
+control the use of
+.Dv RTLD_GLOBAL
+or
+.Dv RTLD_LOCAL .
+The
+.Fl v
+flag enables verbose mode.
+.Sh EXIT STATUS
+.Ex -std
+.Sh AUTHORS
+This software and this manual page were
+developed by SRI International, the University of Cambridge Computer
+Laboratory (Department of Computer Science and Technology), and
+Capabilities Limited under contract
+.Pq FA8750-24-C-B047
+.Pq Do DEC Dc .

bin/dlopen/dlopen.c

@@ -0,0 +1,84 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2025 SRI International
+ *
+ * This software was developed by SRI International, the University of
+ * Cambridge Computer Laboratory (Department of Computer Science and
+ * Technology), and Capabilities Limited under Defense Advanced Research
+ * Projects Agency (DARPA) Contract No. FA8750-24-C-B047 ("DEC").
+ */
+
+#include <sys/cdefs.h>
+
+#include <dlfcn.h>
+#include <err.h>
+#include <libutil.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+
+static bool verbose = false;
+static int seconds = 999999;
+static int dlopen_mode = RTLD_NOW;
+static int dlopen_local_global = 0; /* dlopen(3)'s default is RTLD_LOCAL */
+
+static void _Noreturn
+usage(void)
+{
+	printf("usage: dlopen [-L|N] [-g|l] [-s <seconds>] [-v] <library> [...]\n");
+	exit (1);
+}
+
+int
+main(int argc, char **argv)
+{
+	int ch;
+	uint64_t num;
+
+	while((ch = getopt(argc, argv, "gLlNs:v")) != -1) {
+		switch (ch) {
+		case 'g':
+			dlopen_local_global = RTLD_GLOBAL;
+			break;
+		case 'l':
+			dlopen_local_global = RTLD_LOCAL;
+			break;
+		case 'L':
+			dlopen_mode = RTLD_LAZY;
+			break;
+		case 'N':
+			dlopen_mode = RTLD_NOW;
+			break;
+		case 's':
+			if (expand_number(optarg, &num) != 0)
+				err(1, "bad number '%s'", optarg);
+			if (num > INT_MAX)
+				seconds = INT_MAX;
+			else
+				seconds = num;
+			break;
+		case 'v':
+			verbose = true;
+			break;
+		case '?':
+		default:
+			usage();
+		}
+	}
+	argc -= optind;
+	argv += optind;
+
+	for (int i = 0; i < argc; i++) {
+		if (dlopen(argv[i], dlopen_mode | dlopen_local_global) == NULL)
+			errx(1, "dlopen(%s)", argv[i]);
+		if (verbose)
+			printf("loaded %s\n", argv[i]);
+	}
+	if (seconds != 0 && verbose)
+		printf("sleeping for %d seconds\n", seconds);
+	sleep(seconds);
+	return (0);
+}