Add support for the LD_BIND_NOW environment variable. If it is set to a

nonempty string, then function calls are relocated at program start-up
rather than lazily.  This variable is standard on Sun and SVR4 systems.

The dlopen() function now supports both lazy and immediate binding, as
determined by its "mode" argument, which can be either 1 (RTLD_LAZY) or
2 (RTLD_NOW).  I will add defines of these symbols to <dlfcn.h> as soon
as I've done a little more checking to make sure they won't cause
collisions or bootstrapping problems that would break "make world".

The "LD_*" environment variables which alter dynamic linker behavior are
now treated as unset if they are set to the empty string.  This agrees
with the standard SVR4 conventions for the dynamic linker.

Add a work-around for programs compiled with certain buggy versions of
crt0.o.  The buggy versions failed to set the "crt_ldso" member of the
interface structure.  This caused certain error messages from the
dynamic linker to begin with "(null)" instead of the pathname of the
dynamic linker.

1 files changed, 37 insertions, 16 deletions

diff --git a/libexec/rtld-aout/rtld.c b/libexec/rtld-aout/rtld.c
index 9353721..88e5b27 100644
--- a/libexec/rtld-aout/rtld.c
+++ b/libexec/rtld-aout/rtld.c
@@ -27,7 +27,7 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- *	$Id: rtld.c,v 1.39 1996/10/10 23:16:50 jdp Exp $
+ *	$Id: rtld.c,v 1.40 1996/10/24 16:24:19 jdp Exp $
  */
 
 #include <sys/param.h>
@@ -186,6 +186,7 @@ static gid_t		gid, egid;
 static int		careful;
 static int		anon_fd = -1;
 
+static char		*ld_bind_now;
 static char		*ld_library_path;
 static char		*ld_preload;
 static char		*ld_tracing;
@@ -212,7 +213,7 @@ static struct so_map	*map_object __P((	char *,
 						struct so_map *));
 static int		map_preload __P((void));
 static int		map_sods __P((struct so_map *));
-static int		reloc_and_init __P((struct so_map *));
+static int		reloc_and_init __P((struct so_map *, int));
 static void		unmap_object __P((struct so_map	*, int));
 static struct so_map	*alloc_link_map __P((	char *, struct sod *,
 						struct so_map *, caddr_t,
@@ -221,7 +222,7 @@ static void		free_link_map __P((struct so_map *));
 static inline int	check_text_reloc __P((	struct relocation_info *,
 						struct so_map *,
 						caddr_t));
-static int		reloc_map __P((struct so_map *));
+static int		reloc_map __P((struct so_map *, int));
 static void		reloc_copy __P((struct so_map *));
 static void		init_object __P((struct so_map *));
 static void		init_sods __P((struct so_list *));
@@ -305,6 +306,10 @@ struct _dynamic		*dp;
 	if (version >= CRT_VERSION_BSD_3)
 		main_progname = crtp->crt_prog;
 
+	/* Some buggy versions of crt0.o have crt_ldso filled in as NULL. */
+	if (__progname == NULL)
+		__progname = us;
+
 	/* Fill in some fields in _DYNAMIC or crt structure */
 	if (version >= CRT_VERSION_BSD_4)
 		crtp->crt_ldentry = &ld_entry;		/* crt */
@@ -356,7 +361,7 @@ struct _dynamic		*dp;
 
 	/* Map in LD_PRELOADs before the main program's shared objects so we
 	   can intercept those calls */
-	if (ld_preload != NULL && *ld_preload != '\0') {
+	if (ld_preload != NULL) {
 	        if(map_preload() == -1)			/* Failed */
 			die();
 	}
@@ -373,7 +378,7 @@ struct _dynamic		*dp;
 	crtp->crt_dp->d_un.d_sdt->sdt_loaded = link_map_head->som_next;
 
 	/* Relocate and initialize all mapped objects */
-	if(reloc_and_init(main_map) == -1)		/* Failed */
+	if(reloc_and_init(main_map, ld_bind_now != NULL) == -1)	/* Failed */
 		die();
 
 	ddp = crtp->crt_dp->d_debug;
@@ -903,8 +908,9 @@ map_sods(parent)
  * an error message can be retrieved via dlerror().
  */
 	static int
-reloc_and_init(root)
+reloc_and_init(root, bind_now)
 	struct so_map	*root;
+	int		bind_now;
 {
 	struct so_map	*smp;
 
@@ -925,7 +931,7 @@ reloc_and_init(root)
 	 */
 	for(smp = root;  smp != NULL;  smp = smp->som_next) {
 		if(!(LM_PRIVATE(smp)->spd_flags & RTLD_RTLD)) {
-			if(reloc_map(smp) < 0)
+			if(reloc_map(smp, bind_now) < 0)
 				return -1;
 		}
 	}
@@ -1066,8 +1072,9 @@ caddr_t			addr;
 }
 
 static int
-reloc_map(smp)
+reloc_map(smp, bind_now)
 	struct so_map		*smp;
+	int			bind_now;
 {
 	/*
 	 * Caching structure for reducing the number of calls to
@@ -1140,7 +1147,7 @@ reloc_map(smp)
 			struct nzlist	*p, *np;
 			long	relocation;
 
-			if (RELOC_LAZY_P(r))
+			if (RELOC_JMPTAB_P(r) && !bind_now)
 				continue;
 
 			p = (struct nzlist *)
@@ -1159,7 +1166,7 @@ reloc_map(smp)
 			if(np != NULL)	/* Symbol already cached */
 				src_map = symcache[RELOC_SYMBOL(r)].src_map;
 			else {	/* Symbol not cached yet */
-				np = lookup(sym, &src_map, 0/*XXX-jumpslots!*/);
+				np = lookup(sym, &src_map, RELOC_JMPTAB_P(r));
 				/*
 				 * Record the needed information about
 				 * the symbol in the caching vector,
@@ -1184,11 +1191,17 @@ reloc_map(smp)
 			 * Otherwise it's a run-time allocated common
 			 * whose value is already up-to-date.
 			 */
-			relocation = md_get_addend(r, addr);
-			relocation += np->nz_value;
+			relocation = np->nz_value;
 			if (src_map)
 				relocation += (long)src_map->som_addr;
 
+			if (RELOC_JMPTAB_P(r)) {
+				md_bind_jmpslot(relocation, addr);
+				continue;
+			}
+
+			relocation += md_get_addend(r, addr);
+
 			if (RELOC_PCREL_P(r))
 				relocation -= (long)smp->som_addr;
 
@@ -1200,8 +1213,8 @@ reloc_map(smp)
 					np->nz_size, src_map);
 				continue;
 			}
-			md_relocate(r, relocation, addr, 0);
 
+			md_relocate(r, relocation, addr, 0);
 		} else {
 			md_relocate(r,
 #ifdef SUN_COMPAT
@@ -1817,6 +1830,9 @@ __dlopen(path, mode)
 {
 	struct so_map	*old_tail = link_map_tail;
 	struct so_map	*smp;
+	int		bind_now = mode == 2;
+	/* XXX - s/2/RTLD_NOW/ in the above line, after putting the necessary
+	   defines into <dlfcn.h> and testing for problems. */
 
 	/*
 	 * path == NULL is handled by map_object()
@@ -1832,7 +1848,7 @@ __dlopen(path, mode)
 
 	/* Relocate and initialize all newly-mapped objects */
 	if(link_map_tail != old_tail) {  /* We have mapped some new objects */
-		if(reloc_and_init(smp) == -1)	/* Failed */
+		if(reloc_and_init(smp, bind_now) == -1)	/* Failed */
 			return NULL;
 	}
 
@@ -1989,6 +2005,9 @@ char	*fmt;
  * except that the environment is scanned once only to pick up all
  * known variables, rather than scanned multiple times for each
  * variable.
+ *
+ * If an environment variable of interest is set to the empty string, we
+ * treat it as if it were unset.
  */
 
 #define L(n, u, v) { n, sizeof(n) - 1, u, v },
@@ -2001,13 +2020,14 @@ struct env_scan_tab {
 	L("LD_LIBRARY_PATH=",		1, &ld_library_path)
 	L("LD_PRELOAD=",		1, &ld_preload)
 	L("LD_TRACE_LOADED_OBJECTS=",	0, &ld_tracing)
+	L("LD_BIND_NOW=",		0, &ld_bind_now)
 	L("LD_SUPPRESS_WARNINGS=",	0, &ld_suppress_warnings)
 	L("LD_WARN_NON_PURE_CODE=",	0, &ld_warn_non_pure_code)
 	{ NULL, 0, NULL }
 };
 #undef L
 
-void
+static void
 rt_readenv()
 {
 	char **p = environ;
@@ -2025,7 +2045,8 @@ rt_readenv()
 			if (careful && t->unsafe)
 				continue;	/* skip for set[ug]id */
 			if (strncmp(t->name, v, t->len) == 0) {
-				*t->value = v + t->len;
+				if (*(v + t->len) != '\0')	/* Not empty */
+					*t->value = v + t->len;
 				break;
 			}
 		}