gcc-plugins: Remove cyc_complexity

This plugin has no impact on the resulting binary, is disabled
under COMPILE_TEST, and is not enabled on any builds I'm aware of.
Additionally, given the clarified purpose of GCC plugins in the kernel,
remove cyc_complexity.

Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-hardening@vger.kernel.org
Cc: linux-kbuild@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20211020173554.38122-3-keescook@chromium.org

diff --git a/Documentation/kbuild/gcc-plugins.rst b/Documentation/kbuild/gcc-plugins.rst
index 4b28c7a..0ba7671 100644 (file)
--- a/Documentation/kbuild/gcc-plugins.rst
+++ b/Documentation/kbuild/gcc-plugins.rst
@@ -96,7 +96,6 @@ Enable the GCC plugin infrastructure and some plugin(s) you want to use
 in the kernel config::
 
        CONFIG_GCC_PLUGINS=y
-       CONFIG_GCC_PLUGIN_CYC_COMPLEXITY=y
        CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y
        ...
 
@@ -115,4 +114,3 @@ The GCC plugins are in scripts/gcc-plugins/. You need to put plugin source files
 right under scripts/gcc-plugins/. Creating subdirectories is not supported.
 It must be added to scripts/gcc-plugins/Makefile, scripts/Makefile.gcc-plugins
 and a relevant Kconfig file.
-See the cyc_complexity_plugin.c (CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) GCC plugin.

diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 952e468..6583ecf 100644 (file)
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -1,7 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 
-gcc-plugin-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) += cyc_complexity_plugin.so
-
 gcc-plugin-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) += latent_entropy_plugin.so
 gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY)          \
                += -DLATENT_ENTROPY_PLUGIN

diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
index 7c7ba3b..51d81c3 100644 (file)
--- a/scripts/gcc-plugins/Kconfig
+++ b/scripts/gcc-plugins/Kconfig
@@ -19,22 +19,6 @@ menuconfig GCC_PLUGINS
 
 if GCC_PLUGINS
 
-config GCC_PLUGIN_CYC_COMPLEXITY
-       bool "Compute the cyclomatic complexity of a function" if EXPERT
-       depends on !COMPILE_TEST        # too noisy
-       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).
-
-         Enabling this plugin reports the complexity to stderr during the
-         build. It mainly serves as a simple example of how to create a
-         gcc plugin for the kernel.
-
 config GCC_PLUGIN_SANCOV
        bool
        # Plugin can be removed once the kernel only supports GCC 6+

diff --git a/scripts/gcc-plugins/cyc_complexity_plugin.c b/scripts/gcc-plugins/cyc_complexity_plugin.c
deleted file mode 100644 (file)
index 73124c2..0000000
--- a/scripts/gcc-plugins/cyc_complexity_plugin.c
+++ /dev/null
@@ -1,69 +0,0 @@
-/*
- * 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/cyclomatic_complexity
- *
- * https://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"
-
-__visible int plugin_is_GPL_compatible;
-
-static struct plugin_info cyc_complexity_plugin_info = {
-       .version        = "20160225",
-       .help           = "Cyclomatic Complexity\n",
-};
-
-static unsigned int cyc_complexity_execute(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;
-}
-
-#define PASS_NAME cyc_complexity
-
-#define NO_GATE
-#define TODO_FLAGS_FINISH TODO_dump_func
-
-#include "gcc-generate-gimple-pass.h"
-
-__visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
-{
-       const char * const plugin_name = plugin_info->base_name;
-
-       PASS_INFO(cyc_complexity, "ssa", 1, 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;
-}