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.

6 files changed, 20 insertions, 12 deletions

diff --git a/sysdeps/unix/sysv/linux/configure b/sysdeps/unix/sysv/linux/configure
index ef9d4256d3..ab96601f0c 100644
--- a/sysdeps/unix/sysv/linux/configure
+++ b/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/'`))
diff --git a/sysdeps/unix/sysv/linux/configure.ac b/sysdeps/unix/sysv/linux/configure.ac
index 6738e2d653..b3e74bd2e2 100644
--- a/sysdeps/unix/sysv/linux/configure.ac
+++ b/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/'`))
diff --git a/sysdeps/unix/sysv/linux/i386/configure b/sysdeps/unix/sysv/linux/i386/configure
index f119e62fc3..eb72659dc3 100644
--- a/sysdeps/unix/sysv/linux/i386/configure
+++ b/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
diff --git a/sysdeps/unix/sysv/linux/i386/configure.ac b/sysdeps/unix/sysv/linux/i386/configure.ac
index 64ab2cc2c8..1a11da6dad 100644
--- a/sysdeps/unix/sysv/linux/i386/configure.ac
+++ b/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
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/configure b/sysdeps/unix/sysv/linux/x86_64/64/configure
index 9d1a8d271d..4d3f84567b 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/configure
+++ b/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/)
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/configure.ac b/sysdeps/unix/sysv/linux/x86_64/64/configure.ac
index 8e863b94ad..81114e8b27 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/configure.ac
+++ b/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])