Require Linux 3.2 except on x86 / x86_64, 3.2 headers everywhere.

In <https://sourceware.org/ml/libc-alpha/2016-01/msg00885.html> I
proposed a minimum Linux kernel version of 3.2 for glibc 2.24, since
Linux 2.6.32 has reached EOL.

In the discussion in February, some concerns were expressed about
compatibility with OpenVZ containers.  It's not clear that these are
real issues, given OpenVZ backporting kernel features and faking the
kernel version for guest software, as discussed in
<https://sourceware.org/ml/libc-alpha/2016-02/msg00278.html>.  It's
also not clear that supporting running GNU/Linux distributions from
late 2016 (at the earliest) on a kernel series from 2009 is a sensible
expectation.  However, as an interim step, this patch increases the
requirement everywhere except x86 / x86_64 (since the controversy was
only about those architectures); the special caveats and settings can
easily be removed later when we're ready to increase the requirements
on x86 / x86_64 (and if someone would like to raise the issue on LWN
as suggested in the previous discussion, that would be welcome).  3.2
kernel headers are required everywhere by this patch.

(x32 already requires 3.4 or later, so is unaffected by this patch.)

As usual for such a change, this patch only changes the configure
scripts and associated documentation.  The intent is to follow up with
removal of dead __LINUX_KERNEL_VERSION conditionals.  Each __ASSUME_*
or other macro that becomes dead can then be removed independently.

Tested for x86_64 and x86.

	* sysdeps/unix/sysv/linux/configure.ac (LIBC_LINUX_VERSION):
	Define to 3.2.0.
	(arch_minimum_kernel): Likewise.
	* sysdeps/unix/sysv/linux/configure: Regenerated.
	* sysdeps/unix/sysv/linux/i386/configure.ac (arch_minimum_kernel):
	Define to 2.6.32.
	* sysdeps/unix/sysv/linux/i386/configure: Regenerated.
	* sysdeps/unix/sysv/linux/x86_64/64/configure.ac
	(arch_minimum_kernel): Define to 2.6.32.
	* sysdeps/unix/sysv/linux/x86_64/64/configure: Regenerated.
	* README: Document Linux 3.2 requirement.
	* manual/install.texi (Linux): Document Linux 3.2 headers
	requirement.
	* INSTALL: Regenerated.

ChangeLog

@@ -1,3 +1,20 @@
+2016-02-24  Joseph Myers  <joseph@codesourcery.com>
+
+	* sysdeps/unix/sysv/linux/configure.ac (LIBC_LINUX_VERSION):
+	Define to 3.2.0.
+	(arch_minimum_kernel): Likewise.
+	* sysdeps/unix/sysv/linux/configure: Regenerated.
+	* sysdeps/unix/sysv/linux/i386/configure.ac (arch_minimum_kernel):
+	Define to 2.6.32.
+	* sysdeps/unix/sysv/linux/i386/configure: Regenerated.
+	* sysdeps/unix/sysv/linux/x86_64/64/configure.ac
+	(arch_minimum_kernel): Define to 2.6.32.
+	* sysdeps/unix/sysv/linux/x86_64/64/configure: Regenerated.
+	* README: Document Linux 3.2 requirement.
+	* manual/install.texi (Linux): Document Linux 3.2 headers
+	requirement.
+	* INSTALL: Regenerated.
+
 2016-02-24  Andreas Schwab  <schwab@suse.de>
 
 	* math/test-math-isinff.cc (do_test): Only call isinfl and isnanl

INSTALL

@@ -426,7 +426,7 @@ Specific advice for GNU/Linux systems
 =====================================
 
 If you are installing the GNU C Library on GNU/Linux systems, you need
-to have the header files from a 2.6.32 or newer kernel around for
+to have the header files from a 3.2 or newer kernel around for
 reference.  These headers must be installed using 'make
 headers_install'; the headers present in the kernel source directory are
 not suitable for direct use by the GNU C Library.  You do not need to

NEWS

@@ -7,6 +7,13 @@ using `glibc' in the "product" field.
 
 Version 2.24
 
+* The minimum Linux kernel version that this version of the GNU C Library
+  can be used with is 3.2, except on i[4567]86 and x86_64, where Linux
+  kernel version 2.6.32 or later suffices (on architectures that already
+  required kernel versions more recent than 3.2, those requirements remain
+  unchanged).  Linux 3.2 or later kernel headers are required on all
+  architectures.
+
 * The pap_AN locale has been deleted.  This has been deprecated for a long
   time.  It has been replaced by pap_AW & pap_CW, both of which have long
   been included in previous releases.

README

@@ -17,7 +17,9 @@ GNU/Hurd support requires out-of-tree patches that will eventually be
 incorporated into an official GNU C Library release.
 
 When working with Linux kernels, this version of the GNU C Library
-requires Linux kernel version 2.6.32 or later.
+requires Linux kernel version 3.2 or later on all architectures except
+i[4567]86 and x86_64, where Linux kernel version 2.6.32 or later
+suffices.
 
 Also note that the shared version of the libgcc_s library must be
 installed for the pthread library to work correctly.

manual/install.texi

@@ -489,7 +489,7 @@ patches, although we try to avoid this.
 @cindex kernel header files
 
 If you are installing @theglibc{} on @gnulinuxsystems{}, you need to have
-the header files from a 2.6.32 or newer kernel around for reference.
+the header files from a 3.2 or newer kernel around for reference.
 These headers must be installed using @samp{make headers_install}; the
 headers present in the kernel source directory are not suitable for
 direct use by @theglibc{}.  You do not need to use that kernel, just have

sysdeps/unix/sysv/linux/configure

@@ -39,13 +39,13 @@ fi
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking installed Linux kernel header files" >&5
 $as_echo_n "checking installed Linux kernel header files... " >&6; }
-if ${libc_cv_linux2632+:} false; then :
+if ${libc_cv_linux320+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 #include <linux/version.h>
-#if !defined LINUX_VERSION_CODE || LINUX_VERSION_CODE <  (2 *65536+ 6 *256+ 32) /* 2.6.32 */
+#if !defined LINUX_VERSION_CODE || LINUX_VERSION_CODE <  (3 *65536+ 2 *256+ 0) /* 3.2.0 */
 # error kernel headers missing or too old
 #endif
 int
@@ -57,20 +57,20 @@ main ()
 }
 _ACEOF
 if ac_fn_c_try_compile "$LINENO"; then :
-  libc_cv_linux2632='2.6.32 or later'
+  libc_cv_linux320='3.2.0 or later'
 else
-  libc_cv_linux2632='missing or too old!'
+  libc_cv_linux320='missing or too old!'
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_linux2632" >&5
-$as_echo "$libc_cv_linux2632" >&6; }
-if test "$libc_cv_linux2632" != '2.6.32 or later'; then
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_linux320" >&5
+$as_echo "$libc_cv_linux320" >&6; }
+if test "$libc_cv_linux320" != '3.2.0 or later'; then
   as_fn_error $? "GNU libc requires kernel header files from
-Linux 2.6.32 or later to be installed before configuring.
+Linux 3.2.0 or later to be installed before configuring.
 The kernel header files are found usually in /usr/include/asm and
 /usr/include/linux; make sure these directories use files from
-Linux 2.6.32 or later.  This check uses <linux/version.h>, so
+Linux 3.2.0 or later.  This check uses <linux/version.h>, so
 make sure that file was built correctly when installing the kernel header
 files.  To use kernel headers not from /usr/include/linux, use the
 configure option --with-headers." "$LINENO" 5
@@ -82,7 +82,7 @@ fi
 # set arch_minimum_kernel already, let that override our defaults here.
 # Note that we presume such a fragment has set libc_cv_gcc_unwind_find_fde
 # if appropriate too.
-test -n "$arch_minimum_kernel" || arch_minimum_kernel=2.6.32
+test -n "$arch_minimum_kernel" || arch_minimum_kernel=3.2.0
 if test -n "$minimum_kernel"; then
 
   user_version=$((`echo "$minimum_kernel.0.0.0" | sed 's/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/\1 \* 65536 + \2 \* 256 + \3/'`))

sysdeps/unix/sysv/linux/configure.ac

@@ -1,7 +1,7 @@
 GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
 # Local configure fragment for sysdeps/unix/sysv/linux.
 
-define([LIBC_LINUX_VERSION],[2.6.32])dnl
+define([LIBC_LINUX_VERSION],[3.2.0])dnl
 if test -n "$sysheaders"; then
   OLD_CPPFLAGS=$CPPFLAGS
   CPPFLAGS="$CPPFLAGS $SYSINCLUDES"
@@ -33,7 +33,7 @@ fi
 # set arch_minimum_kernel already, let that override our defaults here.
 # Note that we presume such a fragment has set libc_cv_gcc_unwind_find_fde
 # if appropriate too.
-test -n "$arch_minimum_kernel" || arch_minimum_kernel=2.6.32
+test -n "$arch_minimum_kernel" || arch_minimum_kernel=3.2.0
 if test -n "$minimum_kernel"; then
   changequote(,)
   user_version=$((`echo "$minimum_kernel.0.0.0" | sed 's/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/\1 \* 65536 + \2 \* 256 + \3/'`))

sysdeps/unix/sysv/linux/i386/configure

@@ -1,5 +1,7 @@
 # This file is generated from configure.ac by Autoconf.  DO NOT EDIT!
  # Local configure fragment for sysdeps/unix/sysv/linux/i386.
 
+arch_minimum_kernel=2.6.32
+
 libc_cv_gcc_unwind_find_fde=yes
 ldd_rewrite_script=sysdeps/unix/sysv/linux/ldd-rewrite.sed

sysdeps/unix/sysv/linux/i386/configure.ac

@@ -1,5 +1,7 @@
 GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
 # Local configure fragment for sysdeps/unix/sysv/linux/i386.
 
+arch_minimum_kernel=2.6.32
+
 libc_cv_gcc_unwind_find_fde=yes
 ldd_rewrite_script=sysdeps/unix/sysv/linux/ldd-rewrite.sed

sysdeps/unix/sysv/linux/x86_64/64/configure

@@ -1,6 +1,8 @@
 # This file is generated from configure.ac by Autoconf.  DO NOT EDIT!
  # Local configure fragment for sysdeps/unix/sysv/linux/x86_64/64.
 
+arch_minimum_kernel=2.6.32
+
 test -n "$libc_cv_slibdir" ||
 case "$prefix" in
 /usr | /usr/)

sysdeps/unix/sysv/linux/x86_64/64/configure.ac

@@ -1,4 +1,6 @@
 GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
 # Local configure fragment for sysdeps/unix/sysv/linux/x86_64/64.
 
+arch_minimum_kernel=2.6.32
+
 LIBC_SLIBDIR_RTLDDIR([lib64], [lib64])