commit d2f8ae0e4c5c754f1b2a7b8388d19a1a977e698a upstream.

syncconfig is responsible for keeping auto.conf up-to-date, so if it
fails for any reason, the build must be terminated immediately.

However, since commit 9390dff66a52 ("kbuild: invoke syncconfig if
include/config/auto.conf.cmd is missing"), Kbuild continues running
even after syncconfig fails.

You can confirm this by intentionally making syncconfig error out:

#  diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
#  index 08ba146..307b9de 100644
#  --- a/scripts/kconfig/confdata.c
#  +++ b/scripts/kconfig/confdata.c
#  @@ -1023,6 +1023,9 @@ int conf_write_autoconf(int overwrite)
#          FILE *out, *tristate, *out_h;
#          int i;
#
#  +       if (overwrite)
#  +               return 1;
#  +
#          if (!overwrite && is_present(autoconf_name))
#                  return 0;

Then, syncconfig fails, but Make would not stop:

  $ make -s mrproper allyesconfig defconfig
  $ make
  scripts/kconfig/conf  --syncconfig Kconfig

  *** Error during sync of the configuration.

  make[2]: *** [scripts/kconfig/Makefile;69: syncconfig] Error 1
  make[1]: *** [Makefile;557: syncconfig] Error 2
  make: *** [include/config/auto.conf.cmd] Deleting file 'include/config/tristate.conf'
  make: Failed to remake makefile 'include/config/auto.conf'.
    SYSTBL  arch/x86/include/generated/asm/syscalls_32.h
    SYSHDR  arch/x86/include/generated/asm/unistd_32_ia32.h
    SYSHDR  arch/x86/include/generated/asm/unistd_64_x32.h
    SYSTBL  arch/x86/include/generated/asm/syscalls_64.h
  [ continue running ... ]

The reason is in the behavior of a pattern rule with multi-targets.

  %/auto.conf %/auto.conf.cmd %/tristate.conf: $(KCONFIG_CONFIG)
          $(Q)$(MAKE) -f $(srctree)/Makefile syncconfig

GNU Make knows this rule is responsible for making all the three files
simultaneously. As far as examined, auto.conf.cmd is the target in
question when this rule is invoked. It is probably because auto.conf.cmd
is included below the inclusion of auto.conf.

The inclusion of auto.conf is mandatory, while that of auto.conf.cmd
is optional. GNU Make does not care about the failure in the process
of updating optional include files.

I filed this issue (https://savannah.gnu.org/bugs/?56301) in case this
behavior could be improved somehow in future releases of GNU Make.
Anyway, it is quite easy to fix our Makefile.

Given that auto.conf is already a mandatory include file, there is no
reason to stick auto.conf.cmd optional. Make it mandatory as well.

Cc: linux-stable <stable@vger.kernel.org> # 5.0+
Fixes: 9390dff66a52 ("kbuild: invoke syncconfig if include/config/auto.conf.cmd is missing")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
[commented out diff above to keep patch happy - gregkh]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

[ Upstream commit 221cc2d27ddc49b3e06d4637db02bf78e70c573c ]

When Make recurses to the top Makefile with sub-make-done unset,
the code block surrounded by 'ifneq ($(sub-make-done),1) ... endif'
is parsed multiple times. This happens for in-tree building of
include/config/auto.conf, *-pkg, etc. with GNU Make 4.x.

This is a slight regression by commit 688931a5ad4e ("kbuild: skip
sub-make for in-tree build with GNU Make 4.x") in terms of performance
since that code block contains one $(shell ...) invocation.

Fix it by exporting the variable irrespective of sub-make being run.
I renamed it because GNU Make cannot properly export variables
containing hyphens. This is probably a bug of GNU Make, and the issue
in Kbuild had already been reported by commit 2bfbe7881ee0 ("kbuild:
Do not use hyphen in exported variable name").

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>