# git rev-parse -q --verify 76426e238834f0927dee9925e8832179b8d56d6e^{commit}
# git fetch -q -n -f git://gitlab.ozlabs.ibm.com/mirror/linux-kbuild.git for-next
warning: The last gc run reported the following. Please correct the root cause
and remove .git/gc.log.
Automatic cleanup will not be performed until the file is removed.

warning: There are too many unreachable loose objects; run 'git prune' to remove them.

# git rev-parse -q --verify 76426e238834f0927dee9925e8832179b8d56d6e^{commit}
76426e238834f0927dee9925e8832179b8d56d6e
# git checkout -q -f -B kisskb 76426e238834f0927dee9925e8832179b8d56d6e
# git clean -qxdf
# < git log -1
# commit 76426e238834f0927dee9925e8832179b8d56d6e
# Author: Masahiro Yamada <masahiroy@kernel.org>
# Date:   Wed Apr 8 00:53:52 2020 +0900
# 
#     kbuild: add dummy toolchains to enable all cc-option etc. in Kconfig
#     
#     Staring v4.18, Kconfig evaluates compiler capabilities, and hides CONFIG
#     options your compiler does not support. This works well if you configure
#     and build the kernel on the same host machine.
#     
#     It is inconvenient if you prepare the .config that is carried to a
#     different build environment (typically this happens when you package
#     the kernel for distros) because using a different compiler potentially
#     produces different CONFIG options than the real build environment.
#     So, you probably want to make as many options visible as possible.
#     In other words, you need to create a super-set of CONFIG options that
#     cover any build environment. If some of the CONFIG options turned out
#     to be unsupported on the build machine, they are automatically disabled
#     by the nature of Kconfig.
#     
#     However, it is not feasible to get a full-featured compiler for every
#     arch.
#     
#     This issue was discussed here:
#     
#       https://lkml.org/lkml/2019/12/9/620
#     
#     Other than distros, savedefconfig is also a problem. Some arch sub-systems
#     periodically resync defconfig files. If you use a less-capable compiler
#     for savedefconfig, options that do not meet 'depends on $(cc-option,...)'
#     will be forcibly disabled. So, 'make defconfig && make savedefconfig'
#     may silently change the behavior.
#     
#     This commit adds a set of dummy toolchains that pretend to support any
#     feature.
#     
#     Most of compiler features are tested by cc-option, which simply checks
#     the exit code of $(CC). The dummy tools are shell scripts that always
#     exit with 0. So, $(cc-option, ...) is evaluated as 'y'.
#     
#     There are more complicated checks such as:
#     
#       scripts/gcc-x86_{32,64}-has-stack-protector.sh
#       scripts/gcc-plugin.sh
#       scripts/tools-support-relr.sh
#     
#     scripts/dummy-tools/gcc passes all checks.
#     
#     From the top directory of the source tree, you can do:
#     
#        $ make CROSS_COMPILE=scripts/dummy-tools/ oldconfig
#     
#     Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
#     Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
#     Tested-by: Jeremy Cline <jcline@redhat.com>
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-ld --version
# < git log --format=%s --max-count=1 76426e238834f0927dee9925e8832179b8d56d6e
# < make -s -j 48 ARCH=s390 O=/kisskb/build/kbuild_s390-defconfig_s390x-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-  defconfig
# < make -s -j 48 ARCH=s390 O=/kisskb/build/kbuild_s390-defconfig_s390x-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-  help
# make -s -j 48 ARCH=s390 O=/kisskb/build/kbuild_s390-defconfig_s390x-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-  olddefconfig
# make -s -j 48 ARCH=s390 O=/kisskb/build/kbuild_s390-defconfig_s390x-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-  
/kisskb/src/kernel/trace/ftrace.c: In function 'pid_open.isra.59':
/kisskb/src/kernel/trace/ftrace.c:7166:6: warning: 'seq_ops' may be used uninitialized in this function [-Wmaybe-uninitialized]
  ret = seq_open(file, seq_ops);
      ^
/kisskb/src/kernel/trace/ftrace.c: In function 'pid_write.isra.60':
/kisskb/src/kernel/trace/ftrace.c:7244:8: warning: 'filtered_pids' may be used uninitialized in this function [-Wmaybe-uninitialized]
  ret = trace_pid_write(filtered_pids, &pid_list, ubuf, cnt);
        ^
/kisskb/src/kernel/trace/ftrace.c:7261:22: warning: 'other_pids' may be used uninitialized in this function [-Wmaybe-uninitialized]
  } else if (pid_list && !other_pids) {
                      ^
/kisskb/src/kernel/futex.c: In function 'do_futex':
/kisskb/src/kernel/futex.c:1676:17: warning: 'oldval' may be used uninitialized in this function [-Wmaybe-uninitialized]
   return oldval == cmparg;
                 ^
/kisskb/src/kernel/futex.c:1652:6: note: 'oldval' was declared here
  int oldval, ret;
      ^
/kisskb/src/fs/btrfs/backref.c: In function 'is_shared_data_backref':
/kisskb/src/fs/btrfs/backref.c:394:9: warning: missing braces around initializer [-Wmissing-braces]
  struct prelim_ref target = {0};
         ^
/kisskb/src/fs/btrfs/backref.c:394:9: warning: (near initialization for 'target.rbnode') [-Wmissing-braces]
Completed OK
# rm -rf /kisskb/build/kbuild_s390-defconfig_s390x-gcc4.9
# Build took: 0:03:46.033817