On 2023-05-10 21:06, Matt Turner wrote:
We're mmap'ing a 1-byte file, and since the pagesize on amd64 is 4096
bytes, only the first 4096 byte page (of two) is mapped. Accessing the
second page triggers the SIGBUS.
Ouch, I misread that part of the test. Thanks for reporting that. I
suppose we should go back to invoking getpagesize despite the hassle of
configuring it. I installed the attached further patch; please give it a
try.From 33c26d2700f927432c756ccf7a4fc89403d35b95 Mon Sep 17 00:00:00 2001
From: Paul Eggert <egg...@cs.ucla.edu>
Date: Wed, 10 May 2023 22:57:27 -0700
Subject: [PATCH] Fix port of AC_FUNC_MMAP
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Problem reported by Matt Turner in:
https://lists.gnu.org/r/bug-autoconf/2023-05/msg00005.html
* lib/autoconf/functions.m4 (AC_FUNC_MMAP): Go back to getting the
page size, since the zero-fill test needs this after all.
However, prefer sysconf (_SC_PAGESIZE) or sysconf (_SC_PAGE_SIZE)
to getpagesize (), and use ‘long’ not ‘int’ to store the page size.
Also, declare getpagesize if it is used as a function.
---
lib/autoconf/functions.m4 | 41 ++++++++++++++++++++++++++++++++++-----
1 file changed, 36 insertions(+), 5 deletions(-)
diff --git a/lib/autoconf/functions.m4 b/lib/autoconf/functions.m4
index 5a0f0185..3d6e4aca 100644
--- a/lib/autoconf/functions.m4
+++ b/lib/autoconf/functions.m4
@@ -1283,7 +1283,6 @@ AU_ALIAS([AM_FUNC_MKTIME], [AC_FUNC_MKTIME])
AN_FUNCTION([mmap], [AC_FUNC_MMAP])
AC_DEFUN([AC_FUNC_MMAP],
[AC_REQUIRE([AC_CANONICAL_HOST])dnl for cross-compiles
-dnl FIXME: Remove the unnecessary checks for unistd.h, sys/param.h, getpagesize.
AC_CHECK_HEADERS_ONCE([unistd.h sys/param.h])
AC_CHECK_FUNCS_ONCE([getpagesize])
AC_CACHE_CHECK([for working mmap], [ac_cv_func_mmap_fixed_mapped],
@@ -1311,17 +1310,49 @@ AC_CACHE_CHECK([for working mmap], [ac_cv_func_mmap_fixed_mapped],
#include <fcntl.h>
#include <sys/mman.h>
+#ifndef getpagesize
+# ifdef _SC_PAGESIZE
+# define getpagesize() sysconf (_SC_PAGESIZE)
+# elif defined _SC_PAGE_SIZE
+# define getpagesize() sysconf (_SC_PAGE_SIZE)
+# elif HAVE_GETPAGESIZE
+int getpagesize ();
+# else
+# ifdef HAVE_SYS_PARAM_H
+# include <sys/param.h>
+# ifdef EXEC_PAGESIZE
+# define getpagesize() EXEC_PAGESIZE
+# else /* no EXEC_PAGESIZE */
+# ifdef NBPG
+# define getpagesize() NBPG * CLSIZE
+# ifndef CLSIZE
+# define CLSIZE 1
+# endif /* no CLSIZE */
+# else /* no NBPG */
+# ifdef NBPC
+# define getpagesize() NBPC
+# else /* no NBPC */
+# ifdef PAGESIZE
+# define getpagesize() PAGESIZE
+# endif /* PAGESIZE */
+# endif /* no NBPC */
+# endif /* no NBPG */
+# endif /* no EXEC_PAGESIZE */
+# else /* no HAVE_SYS_PARAM_H */
+# define getpagesize() 8192 /* punt totally */
+# endif /* no HAVE_SYS_PARAM_H */
+# endif
+#endif
+
int
main (void)
{
char *data, *data2, *data3;
const char *cdata2;
- int i, pagesize;
+ long i, pagesize;
int fd, fd2;
- /* The "page size" need not equal the system page size,
- and need not even be a power of 2. */
- pagesize = 8192;
+ pagesize = getpagesize ();
/* First, make a file with some known garbage in it. */
data = (char *) malloc (pagesize);
--
2.39.2
