elf: Add initial flag argument to __libc_early_init

The rseq initialization should happen only for the libc in the base
namespace (in the dynamic case) or the statically linked libc.  The
__libc_multiple_libcs flag does not quite cover this case at present,
so this commit introduces a flag argument to __libc_early_init,
indicating whether the libc being libc is the primary one (of the main
program).

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

csu/libc-start.c

@@ -23,6 +23,7 @@
 #include <exit-thread.h>
 #include <libc-internal.h>
 #include <elf/libc-early-init.h>
+#include <stdbool.h>
 
 #include <elf/dl-tunables.h>
 
@@ -241,7 +242,7 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
 #ifndef SHARED
   /* Perform early initialization.  In the shared case, this function
      is called from the dynamic loader as early as possible.  */
-  __libc_early_init ();
+  __libc_early_init (true);
 
   /* Call the initializer of the libc.  This is only needed here if we
      are compiling for the static library in which case we haven't

elf/dl-call-libc-early-init.c

@@ -23,7 +23,7 @@
 #include <stddef.h>
 
 void
-_dl_call_libc_early_init (struct link_map *libc_map)
+_dl_call_libc_early_init (struct link_map *libc_map, _Bool initial)
 {
   /* There is nothing to do if we did not actually load libc.so.  */
   if (libc_map == NULL)
@@ -37,5 +37,5 @@ _dl_call_libc_early_init (struct link_map *libc_map)
   assert (sym != NULL);
   __typeof (__libc_early_init) *early_init
     = DL_SYMBOL_ADDRESS (libc_map, sym);
-  early_init ();
+  early_init (initial);
 }

elf/dl-open.c

@@ -748,9 +748,22 @@ dl_open_worker (void *a)
     LIBC_PROBE (reloc_complete, 3, args->nsid, r, new);
 
   /* If libc.so was not there before, attempt to call its early
-     initialization routine.  */
+     initialization routine.  Indicate to the initialization routine
+     whether the libc being initialized is the one in the base
+     namespace.  */
   if (!args->libc_already_loaded)
-    _dl_call_libc_early_init (GL(dl_ns)[args->nsid].libc_map);
+    {
+      struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
+#ifdef SHARED
+      bool initial = libc_map->l_ns == LM_ID_BASE;
+#else
+      /* In the static case, there is only one namespace, but it
+	 contains a secondary libc (the primary libc is statically
+	 linked).  */
+      bool initial = false;
+#endif
+      _dl_call_libc_early_init (libc_map, initial);
+    }
 
 #ifndef SHARED
   DL_STATIC_INIT (new);

elf/libc-early-init.h

@@ -22,14 +22,17 @@
 struct link_map;
 
 /* If LIBC_MAP is not NULL, look up the __libc_early_init symbol in it
-   and call this function.  */
-void _dl_call_libc_early_init (struct link_map *libc_map) attribute_hidden;
+   and call this function, with INITIAL as the argument.  */
+void _dl_call_libc_early_init (struct link_map *libc_map, _Bool initial)
+  attribute_hidden;
 
 /* In the shared case, this function is defined in libc.so and invoked
    from ld.so (or on the fist static dlopen) after complete relocation
    of a new loaded libc.so, but before user-defined ELF constructors
    run.  In the static case, this function is called directly from the
-   startup code.  */
-void __libc_early_init (void);
+   startup code.  If INITIAL is true, the libc being initialized is
+   the libc for the main program.  INITIAL is false for libcs loaded
+   for audit modules, dlmopen, and static dlopen.  */
+void __libc_early_init (_Bool initial);
 
 #endif /* _LIBC_EARLY_INIT_H */

elf/libc_early_init.c

@@ -20,7 +20,7 @@
 #include <libc-early-init.h>
 
 void
-__libc_early_init (void)
+__libc_early_init (_Bool initial)
 {
   /* Initialize ctype data.  */
   __ctype_init ();

elf/rtld.c

@@ -2373,8 +2373,10 @@ ERROR: '%s': cannot process note segment.\n", _dl_argv[0]);
       rtld_timer_accum (&relocate_time, start);
     }
 
-  /* Relocation is complete.  Perform early libc initialization.  */
-  _dl_call_libc_early_init (GL(dl_ns)[LM_ID_BASE].libc_map);
+  /* Relocation is complete.  Perform early libc initialization.  This
+     is the initial libc, even if audit modules have been loaded with
+     other libcs.  */
+  _dl_call_libc_early_init (GL(dl_ns)[LM_ID_BASE].libc_map, true);
 
   /* Do any necessary cleanups for the startup OS interface code.
      We do these now so that no calls are made after rtld re-relocation