From 2921f054ef3a2dca9a2cc48bbe956751a49b9d19 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Fri, 15 Jul 2016 13:07:09 +0200
Subject: [PATCH] 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.
---
 admin/CPP-DEFINES |  2 +-
 configure.ac      | 20 +++++++++++---------
 src/emacs.c       | 30 ++++++++++++++----------------
 3 files changed, 26 insertions(+), 26 deletions(-)

diff --git a/admin/CPP-DEFINES b/admin/CPP-DEFINES
index c7ec8ce..5e6146b 100644
--- a/admin/CPP-DEFINES
+++ b/admin/CPP-DEFINES
@@ -233,7 +233,7 @@ HAVE_NET_IF_DL_H
 HAVE_NET_IF_H
 HAVE_NLIST_H
 HAVE_OTF_GET_VARIATION_GLYPHS
-HAVE_PERSONALITY_LINUX32
+HAVE_PERSONALITY_ADDR_NO_RANDOMIZE
 HAVE_PNG
 HAVE_PNG_H
 HAVE_POSIX_MEMALIGN
diff --git a/configure.ac b/configure.ac
index dd1af5b..c94ecb6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1643,15 +1643,17 @@ AC_DEFUN
   sys/resource.h
   sys/utsname.h pwd.h utmp.h util.h)
 
-AC_MSG_CHECKING(if personality LINUX32 can be set)
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <sys/personality.h>]], [[personality (PER_LINUX32)]])],
-               emacs_cv_personality_linux32=yes,
-	       emacs_cv_personality_linux32=no)
-AC_MSG_RESULT($emacs_cv_personality_linux32)
-
-if test $emacs_cv_personality_linux32 = yes; then
-  AC_DEFINE(HAVE_PERSONALITY_LINUX32, 1,
-            [Define to 1 if personality LINUX32 can be set.])
+AC_CACHE_CHECK([for ADDR_NO_RANDOMIZE],
+  [emacs_cv_personality_addr_no_randomize],
+  [AC_COMPILE_IFELSE(
+     [AC_LANG_PROGRAM([[#include <sys/personality.h>]],
+		      [[personality (personality (0xffffffff)
+				     | ADDR_NO_RANDOMIZE)]])],
+     [emacs_cv_personality_addr_no_randomize=yes],
+     [emacs_cv_personality_addr_no_randomize=no])])
+if test $emacs_cv_personality_addr_no_randomize = yes; then
+  AC_DEFINE([HAVE_PERSONALITY_ADDR_NO_RANDOMIZE], [1],
+            [Define to 1 if personality flag ADDR_NO_RANDOMIZE exists.])
 fi
 
 # Note that Solaris has sys/sysinfo.h which defines struct
diff --git a/src/emacs.c b/src/emacs.c
index bb85733..b221984 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,
-- 
2.5.5

