[patch] using ldd on shared libraries

[Bjoern Fischer]

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)?

-Björn


--- 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);
                }

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