[PATCH] gcc-plugins: make it possible to disable CONFIG_GCC_PLUGINS again

[PATCH] gcc-plugins: make it possible to disable CONFIG_GCC_PLUGINS again

[Arnd Bergmann]

I noticed that randconfig builds with gcc no longer produce a lot of
ccache hits, unlike with clang, and traced this back to plugins
now being enabled unconditionally if they are supported.

I am now working around this by adding

   export CCACHE_COMPILERCHECK=/usr/bin/size -A %compiler%

to my top-level Makefile. This changes the heuristic that ccache uses
to determine whether the plugins are the same after a 'make clean'.

However, it also seems that being able to just turn off the plugins is
generally useful, at least for build testing it adds noticeable overhead
but does not find a lot of bugs additional bugs, and may be easier for
ccache users than my workaround.

Fixes: 9f671e58159a ("security: Create "kernel hardening" config area")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 scripts/gcc-plugins/Kconfig | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
index d33de0b9f4f5..e3569543bdac 100644
--- a/scripts/gcc-plugins/Kconfig
+++ b/scripts/gcc-plugins/Kconfig
@@ -14,8 +14,8 @@ config HAVE_GCC_PLUGINS
 	  An arch should select this symbol if it supports building with
 	  GCC plugins.
 
-config GCC_PLUGINS
-	bool
+menuconfig GCC_PLUGINS
+	bool "GCC plugins"
 	depends on HAVE_GCC_PLUGINS
 	depends on PLUGIN_HOSTCC != ""
 	default y
@@ -25,8 +25,7 @@ config GCC_PLUGINS
 
 	  See Documentation/core-api/gcc-plugins.rst for details.
 
-menu "GCC plugins"
-	depends on GCC_PLUGINS
+if GCC_PLUGINS
 
 config GCC_PLUGIN_CYC_COMPLEXITY
 	bool "Compute the cyclomatic complexity of a function" if EXPERT
@@ -113,4 +112,4 @@ config GCC_PLUGIN_ARM_SSP_PER_TASK
 	bool
 	depends on GCC_PLUGINS && ARM
 
-endmenu
+endif
-- 
2.20.0

Re: [PATCH] gcc-plugins: make it possible to disable CONFIG_GCC_PLUGINS again

[Ard Biesheuvel]

On Wed, 11 Dec 2019 at 14:40, Arnd Bergmann <arnd@arndb.de> wrote:
>
> I noticed that randconfig builds with gcc no longer produce a lot of
> ccache hits, unlike with clang, and traced this back to plugins
> now being enabled unconditionally if they are supported.
>
> I am now working around this by adding
>
>    export CCACHE_COMPILERCHECK=/usr/bin/size -A %compiler%
>
> to my top-level Makefile. This changes the heuristic that ccache uses
> to determine whether the plugins are the same after a 'make clean'.
>
> However, it also seems that being able to just turn off the plugins is
> generally useful, at least for build testing it adds noticeable overhead
> but does not find a lot of bugs additional bugs, and may be easier for
> ccache users than my workaround.
>
> Fixes: 9f671e58159a ("security: Create "kernel hardening" config area")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Acked-by: Ard Biesheuvel <ardb@kernel.org>

> ---
>  scripts/gcc-plugins/Kconfig | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
> index d33de0b9f4f5..e3569543bdac 100644
> --- a/scripts/gcc-plugins/Kconfig
> +++ b/scripts/gcc-plugins/Kconfig
> @@ -14,8 +14,8 @@ config HAVE_GCC_PLUGINS
>           An arch should select this symbol if it supports building with
>           GCC plugins.
>
> -config GCC_PLUGINS
> -       bool
> +menuconfig GCC_PLUGINS
> +       bool "GCC plugins"
>         depends on HAVE_GCC_PLUGINS
>         depends on PLUGIN_HOSTCC != ""
>         default y
> @@ -25,8 +25,7 @@ config GCC_PLUGINS
>
>           See Documentation/core-api/gcc-plugins.rst for details.
>
> -menu "GCC plugins"
> -       depends on GCC_PLUGINS
> +if GCC_PLUGINS
>
>  config GCC_PLUGIN_CYC_COMPLEXITY
>         bool "Compute the cyclomatic complexity of a function" if EXPERT
> @@ -113,4 +112,4 @@ config GCC_PLUGIN_ARM_SSP_PER_TASK
>         bool
>         depends on GCC_PLUGINS && ARM
>
> -endmenu
> +endif
> --
> 2.20.0
>

Re: [PATCH] gcc-plugins: make it possible to disable CONFIG_GCC_PLUGINS again

[Masahiro Yamada]

On Wed, Dec 11, 2019 at 10:40 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> I noticed that randconfig builds with gcc no longer produce a lot of
> ccache hits, unlike with clang, and traced this back to plugins
> now being enabled unconditionally if they are supported.
>
> I am now working around this by adding
>
>    export CCACHE_COMPILERCHECK=/usr/bin/size -A %compiler%
>
> to my top-level Makefile. This changes the heuristic that ccache uses
> to determine whether the plugins are the same after a 'make clean'.
>
> However, it also seems that being able to just turn off the plugins is
> generally useful, at least for build testing it adds noticeable overhead
> but does not find a lot of bugs additional bugs, and may be easier for
> ccache users than my workaround.
>
> Fixes: 9f671e58159a ("security: Create "kernel hardening" config area")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---

Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>


-- 
Best Regards
Masahiro Yamada

Re: [PATCH] gcc-plugins: make it possible to disable CONFIG_GCC_PLUGINS again

[Arnd Bergmann]

On Thu, Dec 12, 2019 at 5:52 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Wed, Dec 11, 2019 at 10:40 PM Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > I noticed that randconfig builds with gcc no longer produce a lot of
> > ccache hits, unlike with clang, and traced this back to plugins
> > now being enabled unconditionally if they are supported.
> >
> > I am now working around this by adding
> >
> >    export CCACHE_COMPILERCHECK=/usr/bin/size -A %compiler%
> >
> > to my top-level Makefile. This changes the heuristic that ccache uses
> > to determine whether the plugins are the same after a 'make clean'.
> >
> > However, it also seems that being able to just turn off the plugins is
> > generally useful, at least for build testing it adds noticeable overhead
> > but does not find a lot of bugs additional bugs, and may be easier for
> > ccache users than my workaround.
> >
> > Fixes: 9f671e58159a ("security: Create "kernel hardening" config area")
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>
> Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>

On Wed, Dec 11, 2019 at 2:59 PM Ard Biesheuvel
<ard.biesheuvel@linaro.org> wrote:
>Acked-by: Ard Biesheuvel <ardb@kernel.org>

Thanks! Who would be the best person to pick up the patch?
Should I send it to Andrew?

    Arnd

Re: [PATCH] gcc-plugins: make it possible to disable CONFIG_GCC_PLUGINS again

[Kees Cook]

On Thu, Dec 12, 2019 at 10:59:40AM +0100, Arnd Bergmann wrote:
> On Thu, Dec 12, 2019 at 5:52 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > On Wed, Dec 11, 2019 at 10:40 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > >
> > > I noticed that randconfig builds with gcc no longer produce a lot of
> > > ccache hits, unlike with clang, and traced this back to plugins
> > > now being enabled unconditionally if they are supported.
> > >
> > > I am now working around this by adding
> > >
> > >    export CCACHE_COMPILERCHECK=/usr/bin/size -A %compiler%
> > >
> > > to my top-level Makefile. This changes the heuristic that ccache uses
> > > to determine whether the plugins are the same after a 'make clean'.
> > >
> > > However, it also seems that being able to just turn off the plugins is
> > > generally useful, at least for build testing it adds noticeable overhead
> > > but does not find a lot of bugs additional bugs, and may be easier for
> > > ccache users than my workaround.
> > >
> > > Fixes: 9f671e58159a ("security: Create "kernel hardening" config area")
> > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> >
> > Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
> 
> On Wed, Dec 11, 2019 at 2:59 PM Ard Biesheuvel
> <ard.biesheuvel@linaro.org> wrote:
> >Acked-by: Ard Biesheuvel <ardb@kernel.org>
> 
> Thanks! Who would be the best person to pick up the patch?
> Should I send it to Andrew?

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

I can take it in my tree, or I'm happy to have Masahiro take it.

-- 
Kees Cook

Re: [PATCH] gcc-plugins: make it possible to disable CONFIG_GCC_PLUGINS again

[Masahiro Yamada]

On Fri, Dec 13, 2019 at 2:44 AM Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, Dec 12, 2019 at 10:59:40AM +0100, Arnd Bergmann wrote:
> > On Thu, Dec 12, 2019 at 5:52 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> > >
> > > On Wed, Dec 11, 2019 at 10:40 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > > >
> > > > I noticed that randconfig builds with gcc no longer produce a lot of
> > > > ccache hits, unlike with clang, and traced this back to plugins
> > > > now being enabled unconditionally if they are supported.
> > > >
> > > > I am now working around this by adding
> > > >
> > > >    export CCACHE_COMPILERCHECK=/usr/bin/size -A %compiler%
> > > >
> > > > to my top-level Makefile. This changes the heuristic that ccache uses
> > > > to determine whether the plugins are the same after a 'make clean'.
> > > >
> > > > However, it also seems that being able to just turn off the plugins is
> > > > generally useful, at least for build testing it adds noticeable overhead
> > > > but does not find a lot of bugs additional bugs, and may be easier for
> > > > ccache users than my workaround.
> > > >
> > > > Fixes: 9f671e58159a ("security: Create "kernel hardening" config area")
> > > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > >
> > > Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
> >
> > On Wed, Dec 11, 2019 at 2:59 PM Ard Biesheuvel
> > <ard.biesheuvel@linaro.org> wrote:
> > >Acked-by: Ard Biesheuvel <ardb@kernel.org>
> >
> > Thanks! Who would be the best person to pick up the patch?
> > Should I send it to Andrew?
>
> Acked-by: Kees Cook <keescook@chromium.org>
>
> I can take it in my tree, or I'm happy to have Masahiro take it.
>
> --
> Kees Cook

Kees,
Please apply it to your tree.

Thanks.


-- 
Best Regards
Masahiro Yamada

Re: [PATCH] gcc-plugins: make it possible to disable CONFIG_GCC_PLUGINS again

[Kees Cook]

On Sat, Dec 14, 2019 at 05:56:34PM +0900, Masahiro Yamada wrote:
> On Fri, Dec 13, 2019 at 2:44 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Thu, Dec 12, 2019 at 10:59:40AM +0100, Arnd Bergmann wrote:
> > > On Thu, Dec 12, 2019 at 5:52 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> > > >
> > > > On Wed, Dec 11, 2019 at 10:40 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > > > >
> > > > > I noticed that randconfig builds with gcc no longer produce a lot of
> > > > > ccache hits, unlike with clang, and traced this back to plugins
> > > > > now being enabled unconditionally if they are supported.
> > > > >
> > > > > I am now working around this by adding
> > > > >
> > > > >    export CCACHE_COMPILERCHECK=/usr/bin/size -A %compiler%
> > > > >
> > > > > to my top-level Makefile. This changes the heuristic that ccache uses
> > > > > to determine whether the plugins are the same after a 'make clean'.
> > > > >
> > > > > However, it also seems that being able to just turn off the plugins is
> > > > > generally useful, at least for build testing it adds noticeable overhead
> > > > > but does not find a lot of bugs additional bugs, and may be easier for
> > > > > ccache users than my workaround.
> > > > >
> > > > > Fixes: 9f671e58159a ("security: Create "kernel hardening" config area")
> > > > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > > >
> > > > Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
> > >
> > > On Wed, Dec 11, 2019 at 2:59 PM Ard Biesheuvel
> > > <ard.biesheuvel@linaro.org> wrote:
> > > >Acked-by: Ard Biesheuvel <ardb@kernel.org>
> > >
> > > Thanks! Who would be the best person to pick up the patch?
> > > Should I send it to Andrew?
> >
> > Acked-by: Kees Cook <keescook@chromium.org>
> >
> > I can take it in my tree, or I'm happy to have Masahiro take it.
> >
> > --
> > Kees Cook
> 
> Kees,
> Please apply it to your tree.

Thanks, applied!

-- 
Kees Cook