Re: [PATCH] kbuild: mkcompile_h: Include $LD version in /proc/version

Nick Desaulniers
2020-04-02T18:22:15Z

On Thu, Apr 2, 2020 at 10:02 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> Hi Kees,
>
> On Thu, Apr 2, 2020 at 5:18 PM Kees Cook <keescook@chromium.org> wrote:
> >
> > When doing Clang builds of the kernel, it is possible to link with
> > either ld.bfd (binutils) or ld.lld (LLVM), but it is not possible to
> > discover this from a running kernel. Add the "$LD -v" output to
> > /proc/version.
> >
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > init/Makefile | 2 +-
> > scripts/mkcompile_h | 8 ++++++--
> > 2 files changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/init/Makefile b/init/Makefile
> > index 6246a06364d0..82c15bdb42d7 100644
> > --- a/init/Makefile
> > +++ b/init/Makefile
> > @@ -35,4 +35,4 @@ include/generated/compile.h: FORCE
> > @$($(quiet)chk_compile.h)
> > $(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkcompile_h $@ \
> > "$(UTS_MACHINE)" "$(CONFIG_SMP)" "$(CONFIG_PREEMPT)" \
> > - "$(CONFIG_PREEMPT_RT)" "$(CC) $(KBUILD_CFLAGS)"
> > + "$(CONFIG_PREEMPT_RT)" "$(LD)" "$(CC) $(KBUILD_CFLAGS)"
> > diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h
> > index 3a5a4b210c86..f98c07709370 100755
> > --- a/scripts/mkcompile_h
> > +++ b/scripts/mkcompile_h
> > @@ -6,7 +6,8 @@ ARCH=$2
> > SMP=$3
> > PREEMPT=$4
> > PREEMPT_RT=$5
> > -CC=$6
> > +LD=$6
> > +CC=$7
>
>
> Just a nit.
>
> If you just append 'LD',
> you do not need to touch the 'CC=$6' line.
>
>
> If you do not mind, I will fold the following
> on top of your patch.

With Kees patch + Masahiro's diff applied:
$ cat /proc/version
Linux version 5.6.0-rc7-next-20200330+ (ndesaulniers@<hostname
scrubbed>) (clang version 11.0.0 (git@github.com:llvm/llvm-project.git
6d71daed03ced011cd25f4e4f4122a368fdc757d), LLD 11.0.0
(git@github.com:llvm/llvm-project.git
6d71daed03ced011cd25f4e4f4122a368fdc757d)) #167 SMP Thu Apr 2 11:17:36
PDT 2020

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>

We could actually use this in Android for a VTS test I've, uh, been
meaning to write. Also, LOL at scrubbing the "compatible with" part,
reminds me of user agent strings in the browser, which are god awful.

> --- a/init/Makefile
> +++ b/init/Makefile
> @@ -35,4 +35,4 @@ include/generated/compile.h: FORCE
> @$($(quiet)chk_compile.h)
> $(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkcompile_h $@ \
> "$(UTS_MACHINE)" "$(CONFIG_SMP)" "$(CONFIG_PREEMPT)" \
> - "$(CONFIG_PREEMPT_RT)" "$(LD)" "$(CC) $(KBUILD_CFLAGS)"
> + "$(CONFIG_PREEMPT_RT)" "$(CC) $(KBUILD_CFLAGS)" "$(LD)"
> diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h
> index 8b38a96163e2..5b80a4699740 100755
> --- a/scripts/mkcompile_h
> +++ b/scripts/mkcompile_h
> @@ -6,8 +6,8 @@ ARCH=$2
> SMP=$3
> PREEMPT=$4
> PREEMPT_RT=$5
> -LD=$6
> -CC=$7
> +CC=$6
> +LD=$7

--
Thanks,
~Nick Desaulniers