gcc-plugins: Remove ARM_SSP_PER_TASK plugin

As part of trying to remove GCC plugins from Linux, drop the
ARM_SSP_PER_TASK plugin. The feature is available upstream since GCC
12, so anyone needing newer kernels with per-task ssp can update their
compiler[1].

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/all/08393aa3-05a3-4e3f-8004-f374a3ec4b7e@app.fastmail.com/ [1]
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250409160409.work.168-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

Author: kees

arch/arm/Kconfig

@@ -1380,8 +1380,7 @@ config CC_HAVE_STACKPROTECTOR_TLS
 config STACKPROTECTOR_PER_TASK
 	bool "Use a unique stack canary value for each task"
 	depends on STACKPROTECTOR && CURRENT_POINTER_IN_TPIDRURO && !XIP_DEFLATED_DATA
-	depends on GCC_PLUGINS || CC_HAVE_STACKPROTECTOR_TLS
-	select GCC_PLUGIN_ARM_SSP_PER_TASK if !CC_HAVE_STACKPROTECTOR_TLS
+	depends on CC_HAVE_STACKPROTECTOR_TLS
 	default y
 	help
 	  Due to the fact that GCC uses an ordinary symbol reference from

arch/arm/boot/compressed/Makefile

@@ -96,7 +96,7 @@ KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
 
 ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin \
 	     -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \
-	     -I$(obj) $(DISABLE_ARM_SSP_PER_TASK_PLUGIN)
+	     -I$(obj)
 ccflags-remove-$(CONFIG_FUNCTION_TRACER) += -pg
 asflags-y := -DZIMAGE
 

scripts/Makefile.gcc-plugins

@@ -36,12 +36,6 @@ ifdef CONFIG_GCC_PLUGIN_STACKLEAK
 endif
 export DISABLE_STACKLEAK_PLUGIN
 
-gcc-plugin-$(CONFIG_GCC_PLUGIN_ARM_SSP_PER_TASK) += arm_ssp_per_task_plugin.so
-ifdef CONFIG_GCC_PLUGIN_ARM_SSP_PER_TASK
-    DISABLE_ARM_SSP_PER_TASK_PLUGIN += -fplugin-arg-arm_ssp_per_task_plugin-disable
-endif
-export DISABLE_ARM_SSP_PER_TASK_PLUGIN
-
 # All the plugin CFLAGS are collected here in case a build target needs to
 # filter them out of the KBUILD_CFLAGS.
 GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y))

scripts/gcc-plugins/Kconfig

@@ -46,8 +46,4 @@ config GCC_PLUGIN_LATENT_ENTROPY
 	   * https://grsecurity.net/
 	   * https://pax.grsecurity.net/
 
-config GCC_PLUGIN_ARM_SSP_PER_TASK
-	bool
-	depends on GCC_PLUGINS && ARM
-
 endif