[PATCH v6 6/6] Add sancov plugin

Emese Revfy
2016-04-07T21:21:40Z

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>
---
Makefile | 8 +-
arch/Kconfig | 9 +++
lib/Kconfig.debug | 2 +
scripts/Makefile.gcc-plugins | 9 +++
scripts/gcc-plugins/Makefile | 2 +
scripts/gcc-plugins/sancov_plugin.c | 143 ++++++++++++++++++++++++++++++++++++
6 files changed, 170 insertions(+), 3 deletions(-)
create mode 100644 scripts/gcc-plugins/sancov_plugin.c

diff --git a/Makefile b/Makefile
index 3af7b9e..e079cb4 100644
--- a/Makefile
+++ b/Makefile
@@ -686,10 +686,12 @@ endif
KBUILD_CFLAGS += $(stackp-flag)

ifdef CONFIG_KCOV
- ifeq ($(call cc-option, $(CFLAGS_KCOV)),)
- $(warning Cannot use CONFIG_KCOV: \
+ ifneq ($(CFLAGS_KCOV),)
+ ifeq ($(call cc-option, $(CFLAGS_KCOV)),)
+ $(warning Cannot use CONFIG_KCOV: \
-fsanitize-coverage=trace-pc is not supported by compiler)
- CFLAGS_KCOV =
+ CFLAGS_KCOV =
+ endif
endif
endif

diff --git a/arch/Kconfig b/arch/Kconfig
index e783429..5d856c8 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -380,6 +380,15 @@ config GCC_PLUGIN_CYC_COMPLEXITY
N = the number of nodes
P = the number of connected components (exit nodes).

+config GCC_PLUGIN_SANCOV
+ bool
+ depends on GCC_PLUGINS
+ help
+ This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
+ basic blocks. It supports all gcc versions with plugin support (from
+ gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
+ by Dmitry Vyukov <dvyukov@google.com>.
+
config HAVE_CC_STACKPROTECTOR
bool
help
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index f4b797a..507d3fc 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -707,6 +707,8 @@ config KCOV
bool "Code coverage for fuzzing"
depends on ARCH_HAS_KCOV
select DEBUG_FS
+ select GCC_PLUGINS
+ select GCC_PLUGIN_SANCOV
help
KCOV exposes kernel code coverage information in a form suitable
for coverage-guided fuzzing (randomized testing).
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 34ad58b..25a70fb 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -4,6 +4,15 @@ ifdef CONFIG_GCC_PLUGINS

gcc-plugin-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) += cyc_complexity_plugin.so

+ ifdef CONFIG_GCC_PLUGIN_SANCOV
+ ifeq ($(call cc-option, $(CFLAGS_KCOV)),)
+ gcc-plugin-$(CONFIG_GCC_PLUGIN_SANCOV) += sancov_plugin.so
+ ifneq ($(PLUGINCC),)
+ CFLAGS_KCOV =
+ endif
+ endif
+ endif
+
GCC_PLUGINS_CFLAGS := $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y))

ifeq ($(PLUGINCC),)
diff --git a/scripts/gcc-plugins/Makefile b/scripts/gcc-plugins/Makefile
index 31c72bf..97a923f 100644
--- a/scripts/gcc-plugins/Makefile
+++ b/scripts/gcc-plugins/Makefile
@@ -13,7 +13,9 @@ endif
export GCCPLUGINS_DIR HOSTLIBS

$(HOSTLIBS)-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) := cyc_complexity_plugin.so
+$(HOSTLIBS)-$(CONFIG_GCC_PLUGIN_SANCOV) += sancov_plugin.so

always := $($(HOSTLIBS)-y)

cyc_complexity_plugin-objs := cyc_complexity_plugin.o
+sancov_plugin-objs := sancov_plugin.o
diff --git a/scripts/gcc-plugins/sancov_plugin.c b/scripts/gcc-plugins/sancov_plugin.c
new file mode 100644
index 0000000..1311744
--- /dev/null
+++ b/scripts/gcc-plugins/sancov_plugin.c
@@ -0,0 +1,143 @@
+/*
+ * Copyright 2011-2016 by Emese Revfy <re.emese@gmail.com>
+ * Licensed under the GPL v2, or (at your option) v3
+ *
+ * Homepage:
+ * https://github.com/ephox-gcc-plugins/sancov
+ *
+ * This plugin inserts a __sanitizer_cov_trace_pc() call at the start of basic blocks.
+ * It supports all gcc versions with plugin support (from gcc-4.5 on).
+ * It is based on the commit "Add fuzzing coverage support" by Dmitry Vyukov <dvyukov@google.com>.
+ *
+ * You can read about it more here:
+ * https://gcc.gnu.org/viewcvs/gcc?limit_changes=0&view=revision&revision=231296
+ * http://lwn.net/Articles/674854/
+ * https://github.com/google/syzkaller
+ * https://lwn.net/Articles/677764/
+ *
+ * Usage:
+ * make run
+ */
+
+#include "gcc-common.h"
+
+int plugin_is_GPL_compatible;
+
+tree sancov_fndecl;
+
+static struct plugin_info sancov_plugin_info = {
+ .version = "20160402",
+ .help = "sancov plugin\n",
+};
+
+static unsigned int sancov_execute(void)
+{
+ basic_block bb;
+
+ /* Remove this line when this plugin and kcov will be in the kernel. */
+ if (!strcmp(DECL_NAME_POINTER(current_function_decl), DECL_NAME_POINTER(sancov_fndecl)))
+ return 0;
+
+ FOR_EACH_BB_FN(bb, cfun) {
+ const_gimple stmt;
+ gcall *gcall;
+ gimple_stmt_iterator gsi = gsi_after_labels(bb);
+
+ if (gsi_end_p(gsi))
+ continue;
+
+ stmt = gsi_stmt(gsi);
+ gcall = as_a_gcall(gimple_build_call(sancov_fndecl, 0));
+ gimple_set_location(gcall, gimple_location(stmt));
+ gsi_insert_before(&gsi, gcall, GSI_SAME_STMT);
+ }
+ return 0;
+}
+
+#define PASS_NAME sancov
+
+#define NO_GATE
+#define TODO_FLAGS_FINISH TODO_dump_func | TODO_verify_stmts | TODO_update_ssa_no_phi | TODO_verify_flow
+
+#include "gcc-generate-gimple-pass.h"
+
+static void sancov_start_unit(void __unused *gcc_data, void __unused *user_data)
+{
+ tree leaf_attr, nothrow_attr;
+ tree BT_FN_VOID = build_function_type_list(void_type_node, NULL_TREE);
+
+ sancov_fndecl = build_fn_decl("__sanitizer_cov_trace_pc", BT_FN_VOID);
+
+ DECL_ASSEMBLER_NAME(sancov_fndecl);
+ TREE_PUBLIC(sancov_fndecl) = 1;
+ DECL_EXTERNAL(sancov_fndecl) = 1;
+ DECL_ARTIFICIAL(sancov_fndecl) = 1;
+ DECL_PRESERVE_P(sancov_fndecl) = 1;
+ DECL_UNINLINABLE(sancov_fndecl) = 1;
+ TREE_USED(sancov_fndecl) = 1;
+
+ nothrow_attr = tree_cons(get_identifier("nothrow"), NULL, NULL);
+ decl_attributes(&sancov_fndecl, nothrow_attr, 0);
+ gcc_assert(TREE_NOTHROW(sancov_fndecl));
+#if BUILDING_GCC_VERSION > 4005
+ leaf_attr = tree_cons(get_identifier("leaf"), NULL, NULL);
+ decl_attributes(&sancov_fndecl, leaf_attr, 0);
+#endif
+}
+
+int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
+{
+ int i;
+ struct register_pass_info sancov_plugin_pass_info;
+ const char * const plugin_name = plugin_info->base_name;
+ const int argc = plugin_info->argc;
+ const struct plugin_argument * const argv = plugin_info->argv;
+ bool enable = true;
+
+ static const struct ggc_root_tab gt_ggc_r_gt_sancov[] = {
+ {
+ .base = &sancov_fndecl,
+ .nelt = 1,
+ .stride = sizeof(sancov_fndecl),
+ .cb = &gt_ggc_mx_tree_node,
+ .pchw = &gt_pch_nx_tree_node
+ },
+ LAST_GGC_ROOT_TAB
+ };
+
+ /* BBs can be split afterwards?? */
+ sancov_plugin_pass_info.pass = make_sancov_pass();
+#if BUILDING_GCC_VERSION >= 4009
+ sancov_plugin_pass_info.reference_pass_name = "asan";
+#else
+ sancov_plugin_pass_info.reference_pass_name = "nrv";
+#endif
+ sancov_plugin_pass_info.ref_pass_instance_number = 0;
+ sancov_plugin_pass_info.pos_op = PASS_POS_INSERT_BEFORE;
+
+ if (!plugin_default_version_check(version, &gcc_version)) {
+ error(G_("incompatible gcc/plugin versions"));
+ return 1;
+ }
+
+ for (i = 0; i < argc; ++i) {
+ if (!strcmp(argv[i].key, "no-sancov")) {
+ enable = false;
+ continue;
+ }
+ error(G_("unkown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
+ }
+
+ register_callback(plugin_name, PLUGIN_INFO, NULL, &sancov_plugin_info);
+
+ if (!enable)
+ return 0;
+
+#if BUILDING_GCC_VERSION < 6000
+ register_callback(plugin_name, PLUGIN_START_UNIT, &sancov_start_unit, NULL);
+ register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS, NULL, (void *)&gt_ggc_r_gt_sancov);
+ register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &sancov_plugin_pass_info);
+#endif
+
+ return 0;
+}
--
2.4.1