From: Gerd Moellmann <gerd@gnu.org>
Date: Sat, 10 Nov 2001 11:42:38 +0000 (+0000)
Subject: (unexec): Use mmap/munmap to allocate buffers
X-Git-Tag: emacs-21.2~338
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=027fa1d24cc21de3f4dcf754d41d8111b0de5286;p=emacs.git

(unexec): Use mmap/munmap to allocate buffers
instead of malloc/free.
---

diff --git a/src/ChangeLog b/src/ChangeLog
index 75fb6a029e4..deb7bd60d7b 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2001-11-10  Gerd Moellmann  <gerd@gnu.org>
+
+	* unexelf.c (unexec): Use mmap/munmap to allocate buffers 
+	instead of malloc/free.
+
 2001-11-05  Richard M. Stallman  <rms@gnu.org>
 
 	* m/news-risc.h (BROKEN_PROTOTYPES): Defined.
diff --git a/src/unexelf.c b/src/unexelf.c
index 5519625c783..6153adae2b4 100644
--- a/src/unexelf.c
+++ b/src/unexelf.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1985, 1986, 1987, 1988, 1990, 1992, 1999, 2000
+/* Copyright (C) 1985, 1986, 1987, 1988, 1990, 1992, 1999, 2000, 2001
    Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
@@ -683,6 +683,7 @@ unexec (new_name, old_name, data_start, bss_start, entry_address)
   int old_data_index, new_data2_index;
   int old_mdebug_index;
   struct stat stat_buf;
+  int old_file_size;
 
   /* Open the old file, allocate a buffer of the right size, and read
    * in the file contents. */
@@ -695,16 +696,16 @@ unexec (new_name, old_name, data_start, bss_start, entry_address)
   if (fstat (old_file, &stat_buf) == -1)
     fatal ("Can't fstat (%s): errno %d\n", old_name, errno);
 
-  old_base = malloc (stat_buf.st_size);
-
-  if (old_base == 0)
+  /* We cannot use malloc here because that may use sbrk.  If it does,
+     we'd dump our temporary buffers with Emacs, and we'd have to be
+     extra careful to use the correct value of sbrk(0) after
+     allocating all buffers in the code below, which we aren't.  */
+  old_file_size = stat_buf.st_size;
+  old_base = mmap (NULL, old_file_size, PROT_READ | PROT_WRITE,
+		   MAP_ANON | MAP_PRIVATE, -1, 0);
+  if (old_base == (caddr_t) -1)
     fatal ("Can't allocate buffer for %s\n", old_name);
 
-#ifdef DEBUG
-  fprintf (stderr, "%s: malloc(%d) -> %x\n", old_name, stat_buf.st_size,
-	   old_base);
-#endif
-
   if (read (old_file, old_base, stat_buf.st_size) != stat_buf.st_size)
     fatal ("Didn't read all of %s: errno %d\n", old_name, errno);
 
@@ -791,16 +792,11 @@ unexec (new_name, old_name, data_start, bss_start, entry_address)
   if (ftruncate (new_file, new_file_size))
     fatal ("Can't ftruncate (%s): errno %d\n", new_name, errno);
 
-  new_base = malloc (new_file_size);
-
-  if (new_base == 0)
+  new_base = mmap (NULL, new_file_size, PROT_READ | PROT_WRITE,
+		   MAP_ANON | MAP_PRIVATE, -1, 0);
+  if (new_base == (caddr_t) -1)
     fatal ("Can't allocate buffer for %s\n", old_name);
 
-#ifdef DEBUG
-  fprintf (stderr, "%s: malloc(%d) -> %x\n", new_name, new_file_size
-	   new_base);
-#endif
-
   new_file_h = (ElfW(Ehdr) *) new_base;
   new_program_h = (ElfW(Phdr) *) ((byte *) new_base + old_file_h->e_phoff);
   new_section_h = (ElfW(Shdr) *)
@@ -1227,14 +1223,14 @@ unexec (new_name, old_name, data_start, bss_start, entry_address)
   if (close (new_file))
     fatal ("Can't close (%s): errno %d\n", new_name, errno);
 
-  free (new_base);
+  munmap (new_base, new_file_size);
 
   /* Close old_file, and free the corresponding buffer */
 
   if (close (old_file))
     fatal ("Can't close (%s): errno %d\n", old_name, errno);
 
-  free (old_base);
+  munmap (old_base, old_file_size);
 
   /* Make the new file executable */