Revamp the symbol lookup algorithm to cope better with objects

loaded separately by dlopen that have global symbols with identical
names.  Viewing each dlopened object as a DAG which is linked by its
DT_NEEDED entries in the dynamic table, the search order is as
follows:

  * If the referencing object was linked with -Bsymbolic, search it
    internally.
  * Search all dlopened DAGs containing the referencing object.
  * Search all objects loaded at program start up.
  * Search all objects which were dlopened() using the RTLD_GLOBAL
    flag (which is now supported too).

The search terminates as soon as a strong definition is found.
Lacking that, the first weak definition is used.

These rules match those of Solaris, as best I could determine them
from its vague manual pages and the results of experiments I performed.

PR:		misc/12438

1 files changed, 15 insertions, 2 deletions

diff --git a/libexec/rtld-elf/rtld.h b/libexec/rtld-elf/rtld.h
index 2fe8b15..d23932b 100644
--- a/libexec/rtld-elf/rtld.h
+++ b/libexec/rtld-elf/rtld.h
@@ -29,6 +29,7 @@
 #define RTLD_H 1
 
 #include <sys/types.h>
+#include <sys/queue.h>
 
 #include <link.h>
 #include <elf.h>
@@ -50,6 +51,13 @@ typedef unsigned char bool;
 
 struct Struct_Obj_Entry;
 
+typedef struct Struct_Objlist_Entry {
+    STAILQ_ENTRY(Struct_Objlist_Entry) link;
+    struct Struct_Obj_Entry *obj;
+} Objlist_Entry;
+
+typedef STAILQ_HEAD(Struct_Objlist, Struct_Objlist_Entry) Objlist;
+
 typedef struct Struct_Needed_Entry {
     struct Struct_Needed_Entry *next;
     struct Struct_Obj_Entry *obj;
@@ -71,7 +79,10 @@ typedef struct Struct_Obj_Entry {
     Elf_Word version;		/* Version number of struct format */
 
     struct Struct_Obj_Entry *next;
+    Objlist dldags;		/* Object belongs to these dlopened DAGs (%) */
+    Objlist dagmembers;		/* DAG has these members (%) */
     char *path;			/* Pathname of underlying file (%) */
+    unsigned long mark;		/* Set to "curmark" to avoid repeat visits */
     int refcount;
     int dl_refcount;		/* Number of times loaded by dlopen */
 
@@ -135,9 +146,11 @@ extern Elf_Addr _GLOBAL_OFFSET_TABLE_[];
  */
 int do_copy_relocations(Obj_Entry *);
 unsigned long elf_hash(const char *);
-const Elf_Sym *find_symdef(unsigned long, const Obj_Entry *,
-  const Obj_Entry **, bool);
+const Elf_Sym *find_symdef(unsigned long, Obj_Entry *, const Obj_Entry **,
+  bool);
 void init_pltgot(Obj_Entry *);
+void obj_free(Obj_Entry *);
+Obj_Entry *obj_new(void);
 int reloc_non_plt(Obj_Entry *, Obj_Entry *);
 int reloc_plt(Obj_Entry *, bool);
 void _rtld_bind_start(void);