linux-kernel - [PATCH 5/7] kbuild: remove partial section mismatch detection for built-in.a

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Date:   Mon, 19 Mar 2018 20:26:11 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     linux-kbuild@...r.kernel.org
Cc:     Sam Ravnborg <sam@...nborg.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kernel@...r.kernel.org, Nicholas Piggin <npiggin@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Subject: [PATCH 5/7] kbuild: remove partial section mismatch detection for built-in.a

When built-in.o was incrementally linked with 'ld -r', the section
mismatch analysis for the individual built-in.o was possible when
CONFIG_DEBUG_SECTION_MISMATCH was enabled.

With the migration to the thin archive, built-in.a (former, built-in.o)
is no longer an ELF file.  So, the modpost does nothing useful.
scripts/mod/modpost.c just checks the header to bail out, as follows:

        /* Is this a valid ELF file? */
        if ((hdr->e_ident[EI_MAG0] != ELFMAG0) ||
            (hdr->e_ident[EI_MAG1] != ELFMAG1) ||
            (hdr->e_ident[EI_MAG2] != ELFMAG2) ||
            (hdr->e_ident[EI_MAG3] != ELFMAG3)) {
                /* Not an ELF file - silently ignore it */
                return 0;
        }

We have the full analysis in the final link stage anyway, so we would
not miss the section mismatching.

I do not see a good reason to require extra linking only for the
purpose of the per-directory analysis.  Just get rid of this part.

Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
---

 scripts/Makefile.build | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 316cb95..66461e9 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -456,8 +456,7 @@ quiet_cmd_link_o_target = AR      $@
 
 # If the list of objects to link is empty, just create an empty built-in.a
 cmd_link_o_target = $(if $(strip $(real-obj-y)),\
-		      $(cmd_make_builtin) $@ $(filter $(real-obj-y), $^) \
-		      $(cmd_secanalysis),\
+		      $(cmd_make_builtin) $@ $(filter $(real-obj-y), $^), \
 		      $(cmd_make_empty_builtin) $@)
 
 $(builtin-target): $(real-obj-y) FORCE
-- 
2.7.4