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Message-ID: <20160618181437.GA2633@www.outflux.net>
Date: Sat, 18 Jun 2016 11:14:37 -0700
From: Kees Cook <keescook@...omium.org>
To: Emese Revfy <re.emese@...il.com>
Cc: Michal Marek <mmarek@...e.com>, linux-kbuild@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: [RFC][PATCH] gcc-plugins: abort builds cleanly when not supported
When the compiler doesn't support gcc plugins (either due to missing
headers or too old a version), report the problem and abort the build
instead of emitting a warning and letting the build founder with arcane
compiler errors.
Signed-off-by: Kees Cook <keescook@...omium.org>
---
I think this greatly improves the failure case when trying to use the
gcc plugin infrastructure. Emese, what do you think of this?
---
Makefile | 7 -------
scripts/Makefile.gcc-plugins | 34 +++++++++++++++++++++++++---------
scripts/gcc-plugin.sh | 14 ++++++++++++++
3 files changed, 39 insertions(+), 16 deletions(-)
diff --git a/Makefile b/Makefile
index ab124a0e5e0d..5c61a7155d50 100644
--- a/Makefile
+++ b/Makefile
@@ -633,13 +633,6 @@ endif
# Tell gcc to never replace conditional load with a non-conditional one
KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0)
-PHONY += gcc-plugins
-gcc-plugins: scripts_basic
-ifdef CONFIG_GCC_PLUGINS
- $(Q)$(MAKE) $(build)=scripts/gcc-plugins
-endif
- @:
-
include scripts/Makefile.gcc-plugins
ifdef CONFIG_READABLE_ASM
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index cd7902ccd119..61fc4bbe0c21 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -29,21 +29,37 @@ ifdef CONFIG_GCC_PLUGINS
export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN SANCOV_PLUGIN DISABLE_LATENT_ENTROPY_PLUGIN
+ ifneq ($(PLUGINCC),)
+ # SANCOV_PLUGIN can be only in CFLAGS_KCOV because avoid duplication.
+ GCC_PLUGINS_CFLAGS := $(filter-out $(SANCOV_PLUGIN), $(GCC_PLUGINS_CFLAGS))
+ endif
+
+ KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)
+ GCC_PLUGIN := $(gcc-plugin-y)
+endif
+
+# If plugins aren't supported, abort the build before hard-to-read compiler
+# errors start getting spewed by the main build.
+PHONY += gcc-plugins-check
+gcc-plugins-check: FORCE
+ifdef CONFIG_GCC_PLUGINS
ifeq ($(PLUGINCC),)
ifneq ($(GCC_PLUGINS_CFLAGS),)
ifeq ($(call cc-ifversion, -ge, 0405, y), y)
- PLUGINCC := $(shell $(CONFIG_SHELL) -x $(srctree)/scripts/gcc-plugin.sh "$(__PLUGINCC)" "$(HOSTCXX)" "$(CC)")
- $(warning warning: your gcc installation does not support plugins, perhaps the necessary headers are missing?)
+ $(Q)$(srctree)/scripts/gcc-plugin.sh --show-error "$(__PLUGINCC)" "$(HOSTCXX)" "$(CC)" || true
+ @echo "Cannot use CONFIG_GCC_PLUGINS: your gcc installation does not support plugins, perhaps the necessary headers are missing?" >&2 && exit 1
else
- $(warning warning: your gcc version does not support plugins, you should upgrade it to gcc 4.5 at least)
+ @echo "Cannot use CONFIG_GCC_PLUGINS: your gcc version does not support plugins, you should upgrade it to at least gcc 4.5" >&2 && exit 1
endif
endif
- else
- # SANCOV_PLUGIN can be only in CFLAGS_KCOV because avoid duplication.
- GCC_PLUGINS_CFLAGS := $(filter-out $(SANCOV_PLUGIN), $(GCC_PLUGINS_CFLAGS))
endif
+endif
+ @:
- KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)
- GCC_PLUGIN := $(gcc-plugin-y)
-
+# Actually do the build, if requested.
+PHONY += gcc-plugins
+gcc-plugins: scripts_basic gcc-plugins-check
+ifdef CONFIG_GCC_PLUGINS
+ $(Q)$(MAKE) $(build)=scripts/gcc-plugins
endif
+ @:
diff --git a/scripts/gcc-plugin.sh b/scripts/gcc-plugin.sh
index fb9207565471..b65224bfb847 100755
--- a/scripts/gcc-plugin.sh
+++ b/scripts/gcc-plugin.sh
@@ -1,5 +1,12 @@
#!/bin/sh
srctree=$(dirname "$0")
+
+SHOW_ERROR=
+if [ "$1" = "--show-error" ] ; then
+ SHOW_ERROR=1
+ shift || true
+fi
+
gccplugins_dir=$($3 -print-file-name=plugin)
plugincc=$($1 -E -x c++ - -o /dev/null -I"${srctree}"/gcc-plugins -I"${gccplugins_dir}"/include 2>&1 <<EOF
#include "gcc-common.h"
@@ -13,6 +20,9 @@ EOF
if [ $? -ne 0 ]
then
+ if [ -n "$SHOW_ERROR" ] ; then
+ echo "${plugincc}" >&2
+ fi
exit 1
fi
@@ -48,4 +58,8 @@ then
echo "$2"
exit 0
fi
+
+if [ -n "$SHOW_ERROR" ] ; then
+ echo "${plugincc}" >&2
+fi
exit 1
--
2.7.4
--
Kees Cook
Chrome OS & Brillo Security
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