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 <[email protected]>
Cc: Michal Marek <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Kees Cook <[email protected]>
Reviewed-by: Miguel Ojeda <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Acked-by: Nick Desaulniers <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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.

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

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+