From owner-freebsd-hackers  Tue Feb  5 19: 8:54 2002
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From: Bjoern Fischer <bfischer@Techfak.Uni-Bielefeld.DE>
Date: Wed, 6 Feb 2002 04:03:57 +0100
To: John Polstra <jdp@polstra.com>
Cc: hackers@FreeBSD.ORG
Subject: [patch] using ldd on shared libraries
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References: <20020201201018.GB2992@frolic.no-support.loc> <20020201212028.GC2992@frolic.no-support.loc> <200202020424.g124OXD03238@vashon.polstra.com> <20020202125107.GA481@frolic.no-support.loc>
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Hello John,

I had to closer look into shared objects wrt self-containedness.
Here is a patch for ldd(1), that extends it to be used w/ shared
libraries, too. The patch probably needs some cleanup, but it works.
ldd-stub should be in /usr/libexec. Is /usr/libexec/elf preferable?

Do you have an idea how to generate an ldd-stub without a DT_NEEDED
for libc.so (and still working with ldd, of course)?

-Bj=F6rn


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--- ldd.c	2002/02/06 02:17:46	1.1
+++ ldd.c	2002/02/06 02:39:49
@@ -42,6 +42,8 @@
 #include <stdlib.h>
 #include <unistd.h>
 
+#define LDD_STUB "/usr/libexec/ldd-stub"
+
 extern void	dump_file __P((const char *));
 extern int	error_count;
 
@@ -116,6 +118,9 @@
 		int	n;
 		int	status;
 		int	file_ok;
+		int	shared_object;
+
+		shared_object = 0;
 
 		if ((fd = open(*argv, O_RDONLY, 0)) < 0) {
 			warn("%s", *argv);
@@ -152,6 +157,10 @@
 				warnx("%s: can't read program header", *argv);
 				file_ok = 0;
 			} else {
+				if (ehdr.e_type == ET_DYN) {
+					shared_object = 1;
+					dynamic = 1;
+				} else { /* need to fix white spaces */
 				for (i = 0; i < ehdr.e_phnum; i++) {
 					if (read(fd, &phdr, ehdr.e_phentsize)
 					   != sizeof phdr) {
@@ -163,6 +172,7 @@
 					if (phdr.p_type == PT_DYNAMIC)
 						dynamic = 1;
 				}
+				}
 			}
 			if (!dynamic) {
 				warnx("%s: not a dynamic executable", *argv);
@@ -204,7 +214,11 @@
 			}
 			break;
 		case 0:
-			rval |= execl(*argv, *argv, NULL) != 0;
+			if (shared_object) {
+				setenv("LD_PRELOAD", *argv, 1);
+				rval |= execl(LDD_STUB, LDD_STUB, NULL) != 0;
+			} else
+				rval |= execl(*argv, *argv, NULL) != 0;
 			warn("%s", *argv);
 			_exit(1);
 		}

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int main(int argc, char *argv[]) { }

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