Re: [PATCH] glibc: Support building with 2.6.32 kernels on x86 / x86_64

[Serhii Popovych <spopovyc@cisco.com>]

> 
>>
>>
>> On 3/28/17 11:57 AM, Serhii Popovych wrote:
>>> While glibc states that 2.6.32 kernels still supported
>>> for x86 / x86_64 builds are failing due to out of date
>>> LIBC_LINUX_VERSION macro checks for such architectures.
>>>
>>> This macro statically defined to 3.2.0 with commit 5b4ecd3
>>> (Require Linux 3.2 except on x86 / x86_64, 3.2 headers everywhere.)
>>> and additionally checked before --enable-kernel.
>>>
>>> Since both --enable-kernel and LIBC_LINUX_VERSION checks
>>> are the same and there is no users of last one we can
>>> safely get rid of it enabling glibc builds with 2.6.32
>>> kernel headers.
>>>
>>> Also add --enable-kernel to glibc-initial build so that we
>>> build it correctly with old headers.
>>>
>>> Cc: XE-Linux <xe-linux-external@cisco.com>
>>> Signed-off-by: Serhii Popovych <spopovyc@cisco.com>
>>> ---
>>>  meta/recipes-core/glibc/glibc-initial.inc          |   1 +
>>>  .../glibc/0028-Kill-LIBC_LINUX_VERSION-macro.patch | 113 +++++++++++++++++++++
>>>  meta/recipes-core/glibc/glibc_2.25.bb              |   1 +
>>>  3 files changed, 115 insertions(+)
>>>  create mode 100644 meta/recipes-core/glibc/glibc/0028-Kill-LIBC_LINUX_VERSION-macro.patch
>>>
>>> diff --git a/meta/recipes-core/glibc/glibc-initial.inc b/meta/recipes-core/glibc/glibc-initial.inc
>>> index f94603c..60b25dd 100644
>>> --- a/meta/recipes-core/glibc/glibc-initial.inc
>>> +++ b/meta/recipes-core/glibc/glibc-initial.inc
>>> @@ -12,6 +12,7 @@ do_configure () {
>>>  	find ${S} -name "configure" | xargs touch
>>>  	cfgscript=`python3 -c "import os; print(os.path.relpath('${S}', '.'))"`/configure
>>>  	$cfgscript --host=${TARGET_SYS} --build=${BUILD_SYS} \
>>> +		--enable-kernel=${OLDEST_KERNEL} \
>>>  		--prefix=/usr \
>>>  		--without-cvs --disable-sanity-checks \
>>>  		--with-headers=${STAGING_DIR_TARGET}${includedir} \
>>> diff --git a/meta/recipes-core/glibc/glibc/0028-Kill-LIBC_LINUX_VERSION-macro.patch b/meta/recipes-core/glibc/glibc/0028-Kill-LIBC_LINUX_VERSION-macro.patch
>>> new file mode 100644
>>> index 0000000..f5eaf1c
>>> --- /dev/null
>>> +++ b/meta/recipes-core/glibc/glibc/0028-Kill-LIBC_LINUX_VERSION-macro.patch
>>> @@ -0,0 +1,113 @@
>>> +From 88f83e4b5a8929dac9095ed264700fcb62d5e4dd Mon Sep 17 00:00:00 2001
>>> +From: Serhii Popovych <spopovyc@cisco.com>
>>> +Date: Fri, 17 Mar 2017 15:48:34 +0000
>>> +Subject: Kill LIBC_LINUX_VERSION macro
>>> +
>>> +After commit 5b4ecd3 (Require Linux 3.2 except on x86 / x86_64,
>>> +3.2 headers everywhere.) minimal kernel version raised from
>>> +2.6.32 to 3.2.0 for all architectures except x86 and x86_64
>>> +unless newer already used for architecture.
>>> +
>>> +However LIBC_LINUX_VERSION macro still is in effect and fails
>>> +configure even with --enable-kernel=2.6.32.
>>> +
>>> +While it is present in configure.ac it does not affect anything
>>> +except LINUX_VERSION_CODE check which already performed by
>>> +--enable-kernel.
>>> +
>>
>> --enable-kernel is forces the minimum kernel for glibc to configure for
>> kernel interfaces if not set it defaults to arch specific value but it
>> wont check for version of linux headers during compile time. Whereas
>> this check is checking and errors out during build time if minimum
>> kernel version is not met.
> 
> But why in configure.ac
> define([LIBC_LINUX_VERSION],[3.2.0])
> sets to version 3.2.0?
> 
> and then AC_TRY_COMPILE() sets libc_cv_linuxVER='missing or too old!'
> causing configure to fail due to missing kheaders >= 3.2.0, not 2.6.32.
> 
> Later in configure.ac I see minimum_kernel being checked with
> AC_TRY_COMPILE() and same code as for LIBC_LINUX_VERSION.
> 
> So we check for 3.2.0 and then check for minimum_kernel (--enable-
> kernel) 2.6.32 after this?

By looking at commit 5b4ecd3 (Require Linux 3.2 except on x86 / x86_64,
3.2 headers everywhere.) contents closer I found answer for this
question.

In NEWS file we have:

+  unchanged).  Linux 3.2 or later kernel headers are required on all
+  architectures.

For me that means we should use kernel headers from 3.2 to build glibc,
but for x86 / x86_64 we still may force minimum supported kernel version
of 2.6.32 with --enable-kernel.

I will submit v2 without patch to remove LIBC_LINUX_VERSION check (i.e.
just add --enable-kernel=${OLDEST_KERNEL}.

Thanks,
Serhii

> 
> 
>> If you were to make the LIBC_LINUX_VERSION
>> have a value that matches the arch_minimum_kernel version that would be
>> an improvement.
> 
> configure.ac (and thus configure) is only place where
> LIBC_LINUX_VERSION is used, so I decided to remove it as remnant from
> pre --enable-kernel option ages.
> 
>>
>> As such if you want to do quick fix then lower the value of
>> LIBC_LINUX_VERSION to 2.6.32 when building for x86/x86_64, we can accept
>> such a patch with a bit less happiness.
> 
> I do not want to get quick fix. I want to find way to fix it right.
> 
> Thanks.
> 
>>
>>
>>> +Upstream-Status: Pending
>>> +Signed-off-by: Serhii Popovych <spopovyc@cisco.com>
>>> +---
>>> + sysdeps/unix/sysv/linux/configure    | 39 ------------------------------------
>>> + sysdeps/unix/sysv/linux/configure.ac | 21 -------------------
>>> + 2 files changed, 60 deletions(-)
>>> +
>>> +diff --git a/sysdeps/unix/sysv/linux/configure b/sysdeps/unix/sysv/linux/configure
>>> +index cace758..ab5fabe 100644
>>> +--- a/sysdeps/unix/sysv/linux/configure
>>> ++++ b/sysdeps/unix/sysv/linux/configure
>>> +@@ -6,45 +6,6 @@ if test -n "$sysheaders"; then
>>> +   CPPFLAGS="$CPPFLAGS $SYSINCLUDES"
>>> + 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_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 <  (3 *65536+ 2 *256+ 0) /* 3.2.0 */
>>> +-# error kernel headers missing or too old
>>> +-#endif
>>> +-int
>>> +-main ()
>>> +-{
>>> +-
>>> +-  ;
>>> +-  return 0;
>>> +-}
>>> +-_ACEOF
>>> +-if ac_fn_c_try_compile "$LINENO"; then :
>>> +-  libc_cv_linux320='3.2.0 or later'
>>> +-else
>>> +-  libc_cv_linux320='missing or too old!'
>>> +-fi
>>> +-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
>>> +-fi
>>> +-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_linux320" >&5
>>> +-$as_echo "$libc_cv_linux320" >&6; }
>>> +-if test "$libc_cv_linux320" != '3.2.0 or later'; then
>>> +-  as_fn_error $? "GNU libc requires kernel header files from
>>> +-Linux 3.2.0 or later to be installed before configuring.
>>> +-The kernel header files are found usually in /usr/include/asm and
>>> +-/usr/include/linux; make sure these directories use files from
>>> +-Linux 3.2.0 or later.  This check uses <linux/version.h>, so
>>> +-make sure that file was built correctly when installing the kernel header
>>> +-files.  To use kernel headers not from /usr/include/linux, use the
>>> +-configure option --with-headers." "$LINENO" 5
>>> +-fi
>>> +-
>>> + # If the user gave a minimal version number test whether the available
>>> + # kernel headers are young enough.  Additionally we have minimal
>>> + # kernel versions for some architectures.  If a previous configure fragment
>>> +diff --git a/sysdeps/unix/sysv/linux/configure.ac b/sysdeps/unix/sysv/linux/configure.ac
>>> +index 13abda0..5b47db5 100644
>>> +--- a/sysdeps/unix/sysv/linux/configure.ac
>>> ++++ b/sysdeps/unix/sysv/linux/configure.ac
>>> +@@ -1,31 +1,10 @@
>>> + GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
>>> + # Local configure fragment for sysdeps/unix/sysv/linux.
>>> + 
>>> +-define([LIBC_LINUX_VERSION],[3.2.0])dnl
>>> + if test -n "$sysheaders"; then
>>> +   OLD_CPPFLAGS=$CPPFLAGS
>>> +   CPPFLAGS="$CPPFLAGS $SYSINCLUDES"
>>> + fi
>>> +-define([libc_cv_linuxVER], [libc_cv_linux]patsubst(LIBC_LINUX_VERSION,[\.]))dnl
>>> +-AC_CACHE_CHECK(installed Linux kernel header files, libc_cv_linuxVER, [dnl
>>> +-AC_TRY_COMPILE([#include <linux/version.h>
>>> +-#if !defined LINUX_VERSION_CODE || LINUX_VERSION_CODE < ]dnl
>>> +-patsubst(LIBC_LINUX_VERSION,[^\([^.]*\)\.\([^.]*\)\.\([^.]*\)$],dnl
>>> +-[ (\1 *65536+ \2 *256+ \3) /* \1.\2.\3 */])[
>>> +-# error kernel headers missing or too old
>>> +-#endif], [],
>>> +-	       [libc_cv_linuxVER='LIBC_LINUX_VERSION or later'],
>>> +-	       [libc_cv_linuxVER='missing or too old!'])])
>>> +-if test "$libc_cv_linuxVER" != 'LIBC_LINUX_VERSION or later'; then
>>> +-  AC_MSG_ERROR([GNU libc requires kernel header files from
>>> +-Linux LIBC_LINUX_VERSION 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 LIBC_LINUX_VERSION 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.])
>>> +-fi
>>> + 
>>> + # If the user gave a minimal version number test whether the available
>>> + # kernel headers are young enough.  Additionally we have minimal
>>> +-- 
>>> +2.7.4
>>> +
>>> diff --git a/meta/recipes-core/glibc/glibc_2.25.bb b/meta/recipes-core/glibc/glibc_2.25.bb
>>> index cf9c4f7..869d023 100644
>>> --- a/meta/recipes-core/glibc/glibc_2.25.bb
>>> +++ b/meta/recipes-core/glibc/glibc_2.25.bb
>>> @@ -42,6 +42,7 @@ SRC_URI = "${GLIBC_GIT_URI};branch=${SRCBRANCH};name=glibc \
>>>             file://0025-Define-DUMMY_LOCALE_T-if-not-defined.patch \
>>>             file://0026-elf-dl-deps.c-Make-_dl_build_local_scope-breadth-fir.patch \
>>>             file://0027-locale-fix-hard-coded-reference-to-gcc-E.patch \
>>> +           file://0028-Kill-LIBC_LINUX_VERSION-macro.patch \
>>>  "
>>>  
>>>  NATIVESDKFIXES ?= ""
>>>
>>