From 89604523a76eb3e13014b2bdab7f8870becee284 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Tue, 18 Feb 2020 09:15:34 +0100 Subject: ARM: 8961/2: Fix Kbuild issue caused by per-task stack protector GCC plugin When using plugins, GCC requires that the -fplugin= options precedes any of its plugin arguments appearing on the command line as well. This is usually not a concern, but as it turns out, this requirement is causing some issues with ARM's per-task stack protector plugin and Kbuild's implementation of $(cc-option). When the per-task stack protector plugin is enabled, and we tweak the implementation of cc-option not to pipe the stderr output of GCC to /dev/null, the following output is generated when GCC is executed in the context of cc-option: cc1: error: plugin arm_ssp_per_task_plugin should be specified before \ -fplugin-arg-arm_ssp_per_task_plugin-tso=1 in the command line cc1: error: plugin arm_ssp_per_task_plugin should be specified before \ -fplugin-arg-arm_ssp_per_task_plugin-offset=24 in the command line These errors will cause any option passed to cc-option to be treated as unsupported, which is obviously incorrect. The cause of this issue is the fact that the -fplugin= argument is added to GCC_PLUGINS_CFLAGS, whereas the arguments above are added to KBUILD_CFLAGS, and the contents of the former get filtered out of the latter before being passed to the GCC running the cc-option test, and so the -fplugin= option does not appear at all on the GCC command line. Adding the arguments to GCC_PLUGINS_CFLAGS instead of KBUILD_CFLAGS would be the correct approach here, if it weren't for the fact that we are using $(eval) to defer the moment that they are added until after asm-offsets.h is generated, which is after the point where the contents of GCC_PLUGINS_CFLAGS are added to KBUILD_CFLAGS. So instead, we have to add our plugin arguments to both. For similar reasons, we cannot append DISABLE_ARM_SSP_PER_TASK_PLUGIN to KBUILD_CFLAGS, as it will be passed to GCC when executing in the context of cc-option, whereas the other plugin arguments will have been filtered out, resulting in a similar error and false negative result as above. So add it to ccflags-y instead. Fixes: 189af4657186da08 ("ARM: smp: add support for per-task stack canaries") Reported-by: Merlijn Wajer Tested-by: Tony Lindgren Acked-by: Kees Cook Reviewed-by: Masahiro Yamada Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King --- arch/arm/Makefile | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'arch/arm/Makefile') diff --git a/arch/arm/Makefile b/arch/arm/Makefile index db857d07114f..1fc32b611f8a 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -307,13 +307,15 @@ endif ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y) prepare: stack_protector_prepare stack_protector_prepare: prepare0 - $(eval KBUILD_CFLAGS += \ + $(eval SSP_PLUGIN_CFLAGS := \ -fplugin-arg-arm_ssp_per_task_plugin-tso=$(shell \ awk '{if ($$2 == "THREAD_SZ_ORDER") print $$3;}'\ include/generated/asm-offsets.h) \ -fplugin-arg-arm_ssp_per_task_plugin-offset=$(shell \ awk '{if ($$2 == "TI_STACK_CANARY") print $$3;}'\ include/generated/asm-offsets.h)) + $(eval KBUILD_CFLAGS += $(SSP_PLUGIN_CFLAGS)) + $(eval GCC_PLUGINS_CFLAGS += $(SSP_PLUGIN_CFLAGS)) endif all: $(notdir $(KBUILD_IMAGE)) -- cgit v1.2.3