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Re: glibc 2.24 -- Release blockers


On 07/18/2016 08:49 AM, Sinny Kumari wrote:
Sadly, after applying this patch, build fails for Fedora rawhide on
both ppc64 and
ppc64le due to Memory exhausted problem.

koji scratch build link -
http://ppc.koji.fedoraproject.org/koji/taskinfo?taskID=3540001
Direct link to build log of ppc64 -
http://ppc.koji.fedoraproject.org/kojifiles/work/tasks/2/3540002/build.log

Thanks for checking. I thought about it for a bit and came up with the attached Emacs patch instead, which works for me on x86-64 and x86 Fedora 23. Can you please try it on ppc64? I assume __PPC64__ is defined, if not please feel to substitute the proper symbol and please let me know what that symbol is.

This patch applies to Emacs's emacs-25 branch; if it works I plan to port it to Emacs's master branch. The patch does not implement Florian's idea of re-enabling ASLR before Emacs execs a child process, as I want to keep the emacs-25 patch as simple as possible. However, I do plan to try Florian's idea in the master branch.

>From da7966b5870fc65897bda5adaa403bd5e5740238 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 19 Jul 2016 15:23:14 +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.  Do all this earlier, so as to avoid problems with calls
to brk in the interim.  When doing it, avoid functions like
putenv that may allocate memory.  Special case for __PPC64__,
which needs ASLR disabled in dumped Emacs too.
---
 admin/CPP-DEFINES |  2 +-
 configure.ac      | 20 +++++++++++---------
 src/emacs.c       | 53 ++++++++++++++++++++++++++++++-----------------------
 3 files changed, 42 insertions(+), 33 deletions(-)

diff --git a/admin/CPP-DEFINES b/admin/CPP-DEFINES
index 796b57d..d404dee 100644
--- a/admin/CPP-DEFINES
+++ b/admin/CPP-DEFINES
@@ -237,7 +237,7 @@ 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 678e98e..9da23d1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1615,15 +1615,17 @@ AC_CHECK_HEADERS_ONCE(
   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([if personality ADDR_NO_RANDOMIZE flag exists],
+  [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 5c187e7..b0e5a05 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -106,7 +106,7 @@ 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
 
@@ -674,6 +674,35 @@ main (int argc, char **argv)
 
   stack_base = &dummy;
 
+  dumping = !initialized && (strcmp (argv[argc - 1], "dump") == 0
+			     || strcmp (argv[argc - 1], "bootstrap") == 0);
+
+#ifdef HAVE_PERSONALITY_ADDR_NO_RANDOMIZE
+
+  /* True if address randomization interferes with memory allocaiton.  */
+# ifdef __PPC64__
+  bool disable_aslr = true;
+# else
+  bool disable_aslr = dumping;
+# endif
+
+  if (disable_aslr)
+    {
+      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, warn the user and then try without a
+	     clean slate.  */
+	  fprintf (stderr, "%s: %s\n", argv[0], strerror (errno));
+	}
+    }
+#endif
+
 #ifndef CANNOT_DUMP
   might_dump = !initialized;
 #endif
@@ -781,28 +810,6 @@ 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"))
-    {
-      /* 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);
-
-      /* If the exec fails, try to dump anyway.  */
-      emacs_perror (argv[0]);
-    }
-#endif /* HAVE_PERSONALITY_LINUX32 */
-
 #if defined (HAVE_SETRLIMIT) && defined (RLIMIT_STACK) && !defined (CYGWIN)
   /* Extend the stack space available.  Don't do that if dumping,
      since some systems (e.g. DJGPP) might define a smaller stack
-- 
2.5.5


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