Add sancov plugin

The sancov gcc plugin inserts a __sanitizer_cov_trace_pc() call
at the start of basic blocks.

This plugin is a helper plugin for the kcov feature. It supports
all gcc versions with plugin support (from gcc-4.5 on).
It is based on the gcc commit "Add fuzzing coverage support" by Dmitry Vyukov
(https://gcc.gnu.org/viewcvs/gcc?limit_changes=0&view=revision&revision=231296).

Signed-off-by: Emese Revfy <re.emese@gmail.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michal Marek <mmarek@suse.com>

1 files changed, 20 insertions, 1 deletions

diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index b4a189c95a8a..5e22b60589c1 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -2,10 +2,26 @@ ifdef CONFIG_GCC_PLUGINS
   __PLUGINCC := $(call cc-ifversion, -ge, 0408, $(HOSTCXX), $(HOSTCC))
   PLUGINCC := $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-plugin.sh "$(__PLUGINCC)" "$(HOSTCXX)" "$(CC)")
 
+  SANCOV_PLUGIN := -fplugin=$(objtree)/scripts/gcc-plugins/sancov_plugin.so
+
   gcc-plugin-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY)        += cyc_complexity_plugin.so
+
+  ifdef CONFIG_GCC_PLUGIN_SANCOV
+    ifeq ($(CFLAGS_KCOV),)
+      # It is needed because of the gcc-plugin.sh and gcc version checks.
+      gcc-plugin-$(CONFIG_GCC_PLUGIN_SANCOV)           += sancov_plugin.so
+
+      ifneq ($(PLUGINCC),)
+        CFLAGS_KCOV := $(SANCOV_PLUGIN)
+      else
+        $(warning warning: cannot use CONFIG_KCOV: -fsanitize-coverage=trace-pc is not supported by compiler)
+      endif
+    endif
+  endif
+
   GCC_PLUGINS_CFLAGS := $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y))
 
-  export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN
+  export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN SANCOV_PLUGIN
 
   ifeq ($(PLUGINCC),)
     ifneq ($(GCC_PLUGINS_CFLAGS),)
@@ -16,6 +32,9 @@ ifdef CONFIG_GCC_PLUGINS
         $(warning warning: your gcc version does not support plugins, you should upgrade it to gcc 4.5 at least)
       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
 
   KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)