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Message-ID: <CAGXu5jJyn4sxL2Rb467UyP1X1vF1ZkdBoL8GmResrNiLybztCg@mail.gmail.com>
Date: Wed, 17 Feb 2016 16:27:22 -0800
From: Kees Cook <keescook@...omium.org>
To: Emese Revfy <re.emese@...il.com>
Cc: linux-kbuild <linux-kbuild@...r.kernel.org>, PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Michal Marek <mmarek@...e.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [PATCH v2 2/3] Add Cyclomatic complexity GCC plugin
On Thu, Feb 11, 2016 at 2:41 PM, Emese Revfy <re.emese@...il.com> wrote:
> Add a very simple plugin to demonstrate the GCC plugin infrastructure. This GCC
> plugin computes the cyclomatic complexity of each function.
>
> The complexity M of a function's control flow graph is defined as:
> M = E - N + 2P
> where
> E = the number of edges
> N = the number of nodes
> P = the number of connected components (exit nodes).
Fun! :)
$ sort -nr -k3 /tmp/stderr.txt | head -n10
Cyclomatic Complexity 340 lib/swiotlb.c:swiotlb_late_init_with_tbl
Cyclomatic Complexity 302 drivers/hid/hid-input.c:hidinput_configure_usage
Cyclomatic Complexity 282 fs/pstore/ram.c:ramoops_probe
Cyclomatic Complexity 280 drivers/iommu/amd_iommu_init.c:early_amd_iommu_init
Cyclomatic Complexity 278 mm/page_alloc.c:alloc_large_system_hash
Cyclomatic Complexity 277 drivers/iommu/amd_iommu.c:alloc_coherent
Cyclomatic Complexity 274 lib/rhashtable.c:rhashtable_init
Cyclomatic Complexity 271 lib/swiotlb.c:swiotlb_free
Cyclomatic Complexity 265 drivers/iommu/amd_iommu_init.c:free_on_init_error
Cyclomatic Complexity 228 fs/ext4/super.c:ext4_fill_super
> ---
> arch/Kconfig | 12 ++++
> scripts/Makefile.gcc-plugins | 6 +-
> tools/gcc/Makefile | 4 ++
> tools/gcc/cyc_complexity_plugin.c | 120 ++++++++++++++++++++++++++++++++++++++
> 4 files changed, 141 insertions(+), 1 deletion(-)
> create mode 100644 tools/gcc/cyc_complexity_plugin.c
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index a95e5b1..a558ecb 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -365,6 +365,18 @@ config HAVE_GCC_PLUGINS
> An arch should select this symbol if it supports building with
> gcc plugins.
>
> +config GCC_PLUGIN_CYC_COMPLEXITY
> + bool "Compute the cyclomatic complexity of a function"
> + depends on HAVE_GCC_PLUGINS
> + help
> + The complexity M of a function's control flow graph is defined as:
> + M = E - N + 2P
> + where
> +
> + E = the number of edges
> + N = the number of nodes
> + P = the number of connected components (exit nodes).
> +
> endmenu # "GCC plugins"
>
> config HAVE_CC_STACKPROTECTOR
> diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
> index a60a88e..c49abcd 100644
> --- a/scripts/Makefile.gcc-plugins
> +++ b/scripts/Makefile.gcc-plugins
> @@ -4,7 +4,11 @@ else
> PLUGINCC := $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-plugin.sh "$(HOSTCC)" "$(HOSTCXX)" "$(CC)")
> endif
> ifneq ($(PLUGINCC),)
> -export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGINS_AFLAGS
> +ifdef CONFIG_GCC_PLUGIN_CYC_COMPLEXITY
> +GCC_PLUGIN_CYC_COMPLEXITY_CFLAGS := -fplugin=$(objtree)/tools/gcc/cyc_complexity_plugin.so
> +endif
> +GCC_PLUGINS_CFLAGS := $(GCC_PLUGIN_CYC_COMPLEXITY_CFLAGS)
> +export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGINS_AFLAGS GCC_PLUGIN_CYC_COMPLEXITY
> ifeq ($(KBUILD_EXTMOD),)
> gcc-plugins:
> $(Q)$(MAKE) $(build)=tools/gcc
> diff --git a/tools/gcc/Makefile b/tools/gcc/Makefile
> index b2d64af..31c72bf 100644
> --- a/tools/gcc/Makefile
> +++ b/tools/gcc/Makefile
> @@ -12,4 +12,8 @@ endif
>
> export GCCPLUGINS_DIR HOSTLIBS
>
> +$(HOSTLIBS)-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) := cyc_complexity_plugin.so
This doesn't seem to get cleaned up on a "make clean".
> +
> always := $($(HOSTLIBS)-y)
> +
> +cyc_complexity_plugin-objs := cyc_complexity_plugin.o
> diff --git a/tools/gcc/cyc_complexity_plugin.c b/tools/gcc/cyc_complexity_plugin.c
> new file mode 100644
> index 0000000..c6f0d58
> --- /dev/null
> +++ b/tools/gcc/cyc_complexity_plugin.c
> @@ -0,0 +1,120 @@
> +/*
> + * Copyright 2011-2016 by Emese Revfy <re.emese@...il.com>
> + * Licensed under the GPL v2, or (at your option) v3
> + *
> + * Homepage:
> + * https://github.com/ephox-gcc-plugins/cyclomatic_complexity
> + *
> + * http://en.wikipedia.org/wiki/Cyclomatic_complexity
> + * The complexity M is then defined as:
> + * M = E - N + 2P
> + * where
> + *
> + * E = the number of edges of the graph
> + * N = the number of nodes of the graph
> + * P = the number of connected components (exit nodes).
> + *
> + * Usage (4.5 - 5):
> + * $ make clean; make run
> + */
> +
> +#include "gcc-common.h"
> +
> +int plugin_is_GPL_compatible;
> +
> +static struct plugin_info cyc_complexity_plugin_info = {
> + .version = "20150523",
> + .help = "Cyclomatic Complexity\n",
> +};
> +
> +static unsigned int handle_function(void)
> +{
> + int complexity;
> + expanded_location xloc;
> +
> + // M = E - N + 2P
> + complexity = n_edges_for_fn(cfun) - n_basic_blocks_for_fn(cfun) + 2;
> +
> + xloc = expand_location(DECL_SOURCE_LOCATION(current_function_decl));
> + fprintf(stderr, "Cyclomatic Complexity %d %s:%s\n", complexity, xloc.file, DECL_NAME_POINTER(current_function_decl));
> +
> + return 0;
> +}
> +
> +#if BUILDING_GCC_VERSION >= 4009
> +namespace {
> +static const struct pass_data cyc_complexity_pass_data = {
> +#else
> +static struct gimple_opt_pass cyc_complexity_pass = {
> + .pass = {
> +#endif
> + .type = GIMPLE_PASS,
> + .name = "cyc_complexity",
> +#if BUILDING_GCC_VERSION >= 4008
> + .optinfo_flags = OPTGROUP_NONE,
> +#endif
> +#if BUILDING_GCC_VERSION >= 5000
> +#elif BUILDING_GCC_VERSION >= 4009
> + .has_gate = false,
> + .has_execute = true,
> +#else
> + .gate = NULL,
> + .execute = handle_function,
> + .sub = NULL,
> + .next = NULL,
> + .static_pass_number = 0,
> +#endif
> + .tv_id = TV_NONE,
> + .properties_required = 0,
> + .properties_provided = 0,
> + .properties_destroyed = 0,
> + .todo_flags_start = 0,
> + .todo_flags_finish = TODO_dump_func
> +#if BUILDING_GCC_VERSION < 4009
> + }
> +#endif
> +};
> +
> +#if BUILDING_GCC_VERSION >= 4009
> +class cyc_complexity_pass : public gimple_opt_pass {
> +public:
> + cyc_complexity_pass() : gimple_opt_pass(cyc_complexity_pass_data, g) {}
> +#if BUILDING_GCC_VERSION >= 5000
> + virtual unsigned int execute(function *) { return handle_function(); }
> +#else
> + unsigned int execute() { return handle_function(); }
> +#endif
> +};
> +}
> +
> +static struct opt_pass *make_cyc_complexity_pass(void)
> +{
> + return new cyc_complexity_pass();
> +}
> +#else
> +static struct opt_pass *make_cyc_complexity_pass(void)
> +{
> + return &cyc_complexity_pass.pass;
> +}
> +#endif
> +
> +int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
> +{
> + const char * const plugin_name = plugin_info->base_name;
> + struct register_pass_info cyc_complexity_pass_info;
> +
> + cyc_complexity_pass_info.pass = make_cyc_complexity_pass();
> + cyc_complexity_pass_info.reference_pass_name = "ssa";
> + cyc_complexity_pass_info.ref_pass_instance_number = 1;
> + cyc_complexity_pass_info.pos_op = PASS_POS_INSERT_AFTER;
> +
> + if (!plugin_default_version_check(version, &gcc_version)) {
> + error(G_("incompatible gcc/plugin versions"));
> + return 1;
> + }
> +
> + register_callback(plugin_name, PLUGIN_INFO, NULL, &cyc_complexity_plugin_info);
> + register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &cyc_complexity_pass_info);
> +
> + return 0;
> +}
> --
> 2.4.1
>
It's a shame there's been so much churn with gcc's plugin API. I
wonder if it might make sense to choose 5.0 as the supported compiler
version for this feature, just to cut down on all the ifdef noise. For
now, let's keep it as-is, though.
-Kees
--
Kees Cook
Chrome OS & Brillo Security
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