gcc-plugins: remove SANCOV gcc plugin

With the minimum gcc version raised to 8.1, all supported compilers
now understand the -fsanitize-coverage=trace-pc option, and there
is no longer a need for the separate compiler plugin.

Since only gcc-5 was able to use the plugin for several year now,
it was already likely unused.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Author: arndb

lib/Kconfig.debug

@@ -2153,18 +2153,12 @@ config ARCH_HAS_KCOV
 	  build and run with CONFIG_KCOV. This typically requires
 	  disabling instrumentation for some early boot code.
 
-config CC_HAS_SANCOV_TRACE_PC
-	def_bool $(cc-option,-fsanitize-coverage=trace-pc)
-
-
 config KCOV
 	bool "Code coverage for fuzzing"
 	depends on ARCH_HAS_KCOV
-	depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
 	depends on !ARCH_WANTS_NO_INSTR || HAVE_NOINSTR_HACK || \
 		   GCC_VERSION >= 120000 || CC_IS_CLANG
 	select DEBUG_FS
-	select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
 	select OBJTOOL if HAVE_NOINSTR_HACK
 	help
 	  KCOV exposes kernel code coverage information in a form suitable

scripts/Makefile.gcc-plugins

@@ -38,8 +38,6 @@ KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)
 
 # Some plugins are enabled outside of this Makefile, but they still need to
 # be included in GCC_PLUGIN so they can get built.
-gcc-plugin-external-$(CONFIG_GCC_PLUGIN_SANCOV)			\
-	+= sancov_plugin.so
 gcc-plugin-external-$(CONFIG_GCC_PLUGIN_RANDSTRUCT)		\
 	+= randomize_layout_plugin.so
 

scripts/Makefile.kcov

@@ -1,6 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
 kcov-flags-$(CONFIG_CC_HAS_SANCOV_TRACE_PC)	+= -fsanitize-coverage=trace-pc
 kcov-flags-$(CONFIG_KCOV_ENABLE_COMPARISONS)	+= -fsanitize-coverage=trace-cmp
-kcov-flags-$(CONFIG_GCC_PLUGIN_SANCOV)		+= -fplugin=$(objtree)/scripts/gcc-plugins/sancov_plugin.so
 
 export CFLAGS_KCOV := $(kcov-flags-y)

scripts/gcc-plugins/Kconfig

@@ -19,16 +19,6 @@ menuconfig GCC_PLUGINS
 
 if GCC_PLUGINS
 
-config GCC_PLUGIN_SANCOV
-	bool
-	# Plugin can be removed once the kernel only supports GCC 6+
-	depends on !CC_HAS_SANCOV_TRACE_PC
-	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 GCC_PLUGIN_LATENT_ENTROPY
 	bool "Generate some entropy during boot and runtime"
 	help