linux-kernel - Re: [PATCH 1/2] kbuild: move shared library build rules to scripts/gcc-plugins/Makefile

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Date:   Wed, 29 Jul 2020 14:18:17 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, Emese Revfy <re.emese@...il.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] kbuild: move shared library build rules to
 scripts/gcc-plugins/Makefile

On Wed, Jul 29, 2020 at 12:15:36PM +0900, Masahiro Yamada wrote:
> The shared library build rules are currently implemented in
> scripts/Makefile.host, but actually GCC-plugin is the only user of
> them. Hence, they do not need to be treewide available.

Are none of the VDSOs intending to use these rules?

> Move all the relevant build rules to scripts/gcc-plugins/Makefile.
> 
> I also optimized the build steps so *.so is directly built from .c
> because every upstream plugin is compiled from a single source file.
> 
> I am still keeping the infrastructure to build a plugin from multiple
> files because Kees suggested to do so in my previous attempt.
> (https://lkml.org/lkml/2019/1/11/1107)
> 
> If the plugin, foo.so, is compiled from two files foo.c and foo2.c,
> then you can do like follows:
> 
>   foo-objs := foo.o foo2.o
> 
> Single-file plugins do not need the *-objs notation.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

But, yeah, sure!

Acked-by: Kees Cook <keescook@...omium.org>

Unrelated, but I do note that objtool maybe has the wrong indentation,
path name reporting, and tool names (HOSTLD vs CC)?

...
  HOSTCC  scripts/asn1_compiler
  HOSTCC  scripts/extract-cert
  HOSTCC  scripts/genksyms/genksyms.o
  YACC    scripts/genksyms/parse.tab.[ch]
  LEX     scripts/genksyms/lex.lex.c
  DESCEND  objtool
  HOSTCXX scripts/gcc-plugins/cyc_complexity_plugin.so
  HOSTCXX scripts/gcc-plugins/latent_entropy_plugin.so
  HOSTCXX scripts/gcc-plugins/structleak_plugin.so
  GENSEED scripts/gcc-plugins/randomize_layout_seed.h
  HOSTCXX scripts/gcc-plugins/stackleak_plugin.so
  HOSTCC  scripts/genksyms/parse.tab.o
  HOSTCC  scripts/genksyms/lex.lex.o
  HOSTCC   /home/kees/src/linux-build/plugins/tools/objtool/fixdep.o
  HOSTLD  arch/x86/tools/relocs
  HOSTLD   /home/kees/src/linux-build/plugins/tools/objtool/fixdep-in.o
  LINK     /home/kees/src/linux-build/plugins/tools/objtool/fixdep
  CC       /home/kees/src/linux-build/plugins/tools/objtool/exec-cmd.o
  CC       /home/kees/src/linux-build/plugins/tools/objtool/help.o
  CC       /home/kees/src/linux-build/plugins/tools/objtool/weak.o
...

-- 
Kees Cook