Port to glibc 2.24 (pre-release) + ppc64

Inspired by a suggestion by Florian Weimer in:
https://sourceware.org/ml/libc-alpha/2016-07/msg00425.html
* configure.ac (HAVE_PERSONALITY_ADDR_NO_RANDOMIZE):
Rename from HAVE_PERSONALITY_LINUX32, and check for
ADDR_NO_RANDOMIZE (the crucial thing) instead of for LINUX32.
All uses changed.
* src/emacs.c (main) [HAVE_PERSONALITY_ADDR_NO_RANDOMIZE]:
Use ADDR_NO_RANDOMIZE from personality.h rather than inventing the
flag ourselves.  Just set that flag, rather than also setting the
persona.  When doing it, avoid functions like putenv that may
allocate memory.

1 files changed, 14 insertions, 16 deletions

diff --git a/src/emacs.c b/src/emacs.c
index bb85733a1f2..b2219844ca0 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -112,7 +112,7 @@ extern void moncontrol (int mode);
 #include <sys/resource.h>
 #endif
 
-#ifdef HAVE_PERSONALITY_LINUX32
+#ifdef HAVE_PERSONALITY_ADDR_NO_RANDOMIZE
 #include <sys/personality.h>
 #endif
 
@@ -796,24 +796,22 @@ main (int argc, char **argv)
   dumping = !initialized && (strcmp (argv[argc - 1], "dump") == 0
                              || strcmp (argv[argc - 1], "bootstrap") == 0);
 
-#ifdef HAVE_PERSONALITY_LINUX32
-  if (dumping && ! getenv ("EMACS_HEAP_EXEC"))
+#ifdef HAVE_PERSONALITY_ADDR_NO_RANDOMIZE
+  if (dumping)
     {
-      /* Set this so we only do this once.  */
-      xputenv ("EMACS_HEAP_EXEC=true");
-
-      /* A flag to turn off address randomization which is introduced
-         in linux kernel shipped with fedora core 4 */
-#define ADD_NO_RANDOMIZE 0x0040000
-      personality (PER_LINUX32 | ADD_NO_RANDOMIZE);
-#undef  ADD_NO_RANDOMIZE
-
-      execvp (argv[0], argv);
+      int pers = personality (0xffffffff);
+      if (! (pers & ADDR_NO_RANDOMIZE)
+          && 0 <= personality (pers | ADDR_NO_RANDOMIZE))
+        {
+          /* Address randomization was enabled, but is now disabled.
+             Re-execute Emacs to get a clean slate.  */
+          execvp (argv[0], argv);
 
-      /* If the exec fails, try to dump anyway.  */
-      emacs_perror (argv[0]);
+          /* If the exec fails, warn and then try without a clean slate.  */
+          perror (argv[0]);
+        }
     }
-#endif /* HAVE_PERSONALITY_LINUX32 */
+#endif
 
 #if defined (HAVE_SETRLIMIT) && defined (RLIMIT_STACK) && !defined (CYGWIN)
   /* Extend the stack space available.  Don't do that if dumping,