Re: Size of emacs.pdmp changes between successive installs

[Paul Eggert <eggert@cs.ucla.edu>]

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>> Only when unexecing.

> Right, with this trivial patch I'm getting a reproducible size
> of emacs.pdmp, too:

Thanks to both of you. I installed the attached, which does something 
similar and simplifies the code a bit too.

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From 9ac586928bbef16b572bcb34bfcbcb5515c2335a Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 19 Nov 2019 18:23:01 -0800
Subject: [PATCH] Make .pdmp file more reproducible
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Problem reported by Ulrich Müller
<https://lists.gnu.org/r/emacs-devel/2019-11/msg00757.html>
and diagnosed by Andreas Schwab
<https://lists.gnu.org/r/emacs-devel/2019-11/msg00774.html>.
* src/sysdep.c (maybe_disable_address_randomization):
Disable ASLR if any kind of dumping, instead of merely if
unexec dumping.  Omit first arg for simplicity; all uses changed.
---
 src/emacs.c  | 3 +--
 src/lisp.h   | 4 ++--
 src/sysdep.c | 7 +++++--
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/emacs.c b/src/emacs.c
index 21a05d337e..8a6e34deda 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -1054,8 +1054,7 @@ main (int argc, char **argv)
     load_pdump (argc, argv);
 #endif
 
-  argc = maybe_disable_address_randomization (
-    will_dump_with_unexec_p (), argc, argv);
+  argc = maybe_disable_address_randomization (argc, argv);
 
 #if defined GNU_LINUX && defined HAVE_UNEXEC
   if (!initialized)
diff --git a/src/lisp.h b/src/lisp.h
index 1d25add928..e0ae2c4262 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4576,10 +4576,10 @@ #define DAEMON_RUNNING (w32_daemon_event != INVALID_HANDLE_VALUE)
 
 /* Defined in sysdep.c.  */
 #ifdef HAVE_PERSONALITY_ADDR_NO_RANDOMIZE
-extern int maybe_disable_address_randomization (bool, int, char **);
+extern int maybe_disable_address_randomization (int, char **);
 #else
 INLINE int
-maybe_disable_address_randomization (bool dumping, int argc, char **argv)
+maybe_disable_address_randomization (int argc, char **argv)
 {
   return argc;
 }
diff --git a/src/sysdep.c b/src/sysdep.c
index aa18ee22fd..e34ab2eb58 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -158,14 +158,17 @@ #define ULLONG_MAX TYPE_MAXIMUM (unsigned long long int)
 /* Try to disable randomization if the current process needs it and
    does not appear to have it already.  */
 int
-maybe_disable_address_randomization (bool dumping, int argc, char **argv)
+maybe_disable_address_randomization (int argc, char **argv)
 {
   /* Undocumented Emacs option used only by this function.  */
   static char const aslr_disabled_option[] = "--__aslr-disabled";
 
   if (argc < 2 || strcmp (argv[1], aslr_disabled_option) != 0)
     {
-      bool disable_aslr = dumping;
+      /* If dumping via unexec, ASLR must be disabled, as otherwise
+	 data may be scattered and undumpable as a simple executable.
+	 If pdumping, disabling ASLR makes the .pdmp file reproducible.  */
+      bool disable_aslr = will_dump_p ();
 # ifdef __PPC64__
       disable_aslr = true;
 # endif
-- 
2.23.0