Replace __libc_multiple_libcs with __libc_initial flag

Change sbrk to fail for !__libc_initial (in the generic
implementation).  As a result, sbrk is (relatively) safe to use
for the __libc_initial case (from the main libc).  It is therefore
no longer necessary to avoid using it in that case (or updating the
brk cache), and the __libc_initial flag does not need to be updated
as part of dlmopen or static dlopen.

As before, direct brk system calls on Linux may lead to memory
corruption.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

2 files changed, 8 insertions, 15 deletions

diff --git a/csu/init-first.c b/csu/init-first.c
index 47aaacd..2115215 100644
--- a/csu/init-first.c
+++ b/csu/init-first.c
@@ -28,10 +28,6 @@
 
 #include <ldsodefs.h>
 
-/* Set nonzero if we have to be prepared for more than one libc being
-   used in the process.  Safe assumption if initializer never runs.  */
-int __libc_multiple_libcs attribute_hidden = 1;
-
 /* Remember the command line argument and enviroment contents for
    later calls of initializers for dynamic libraries.  */
 int __libc_argc attribute_hidden;
@@ -50,16 +46,16 @@ _init_first (int argc, char **argv, char **envp)
 {
 #endif
 
-  __libc_multiple_libcs = &_dl_starting_up && !_dl_starting_up;
-
   /* Make sure we don't initialize twice.  */
-  if (!__libc_multiple_libcs)
+#ifdef SHARED
+  if (__libc_initial)
     {
       /* Set the FPU control word to the proper default value if the
 	 kernel would use a different value.  */
       if (__fpu_control != GLRO(dl_fpu_control))
 	__setfpucw (__fpu_control);
     }
+#endif
 
   /* Save the command-line arguments.  */
   __libc_argc = argc;
diff --git a/csu/libc-start.c b/csu/libc-start.c
index 2d4d2ed..d330812 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -141,8 +141,6 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
   /* Result of the 'main' function.  */
   int result;
 
-  __libc_multiple_libcs = &_dl_starting_up && !_dl_starting_up;
-
 #ifndef SHARED
   _dl_relocate_static_pie ();
 
@@ -213,12 +211,11 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
 # endif
 
 # ifdef DL_SYSDEP_OSCHECK
-  if (!__libc_multiple_libcs)
-    {
-      /* This needs to run to initiliaze _dl_osversion before TLS
-	 setup might check it.  */
-      DL_SYSDEP_OSCHECK (__libc_fatal);
-    }
+  {
+    /* This needs to run to initiliaze _dl_osversion before TLS
+       setup might check it.  */
+    DL_SYSDEP_OSCHECK (__libc_fatal);
+  }
 # endif
 
   /* Initialize libpthread if linked in.  */