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Date: Mon, 08 Feb 2016 00:05:15 +0100
From: Rasmus Villemoes <linux@...musvillemoes.dk>
To: Emese Revfy <re.emese@...il.com>
Cc: linux-kbuild@...r.kernel.org, pageexec@...email.hu, spender@...ecurity.net, kernel-hardening@...ts.openwall.com, mmarek@...e.com, keescook@...omium.org
Subject: Re: [PATCH 2/3] Add Cyclomatic complexity GCC plugin
On Sun, Feb 07 2016, 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).
>
> ---
> Makefile | 6 +-
> arch/Kconfig | 16 +++++
> tools/gcc/Makefile | 4 ++
> tools/gcc/cyc_complexity_plugin.c | 120 ++++++++++++++++++++++++++++++++++++++
> 4 files changed, 145 insertions(+), 1 deletion(-)
> create mode 100644 tools/gcc/cyc_complexity_plugin.c
>
> diff --git a/Makefile b/Makefile
> index 96ce015..9f76c26 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -628,7 +628,11 @@ 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 -DGCC_PLUGIN_CYC_COMPLEXITY
> +endif
> +GCC_PLUGINS_CFLAGS := $(GCC_PLUGIN_CYC_COMPLEXITY_CFLAGS)
> +export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGINS_AFLAGS GCC_PLUGIN_CYC_COMPLEXITY
Hm, when the number of plugins grow, I think it'll be somewhat ugly
having all this in the main makefile. Can't all the plugin-related stuff
live in a separate makefile? The same goes for the Kconfig part.
Also, I think the compile command lines are already complicated enough
(I sometimes use V=1 to see what's going on), so I think it's better
that the plugins that need to make themselves known do so "from within"
gcc; something like
static void define_feature_macro(void __unused *event_data, void __unused *data)
{
cpp_define(parse_in, "HAVE_ATTRIBUTE_FOOBAR");
}
...
register_callback(plugin_name, PLUGIN_START_UNIT, &define_feature_macro, NULL);
> +
> +#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
> +};
> +
This is really yucky. Is there any way a mere mortal could figure out
how to write this? Or could the compatibility layer provide some utility
macros that would take care of the boilerplate?
Rasmus
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