diff options
authorArd Biesheuvel <>2020-02-18 09:15:34 +0100
committerRussell King <>2020-02-21 17:03:22 +0000
commit89604523a76eb3e13014b2bdab7f8870becee284 (patch)
parentf87b1c49bc675da30d8e1e8f4b60b800312c7b90 (diff)
ARM: 8961/2: Fix Kbuild issue caused by per-task stack protector GCC pluginfor-linusfixes
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 <>
2 files changed, 5 insertions, 3 deletions
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
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;}'\
all: $(notdir $(KBUILD_IMAGE))
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index da599c3a1193..9c11e7490292 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -101,7 +101,6 @@ clean-files += piggy_data lib1funcs.S ashldi3.S bswapsdi2.S \
$(libfdt) $(libfdt_hdrs) hyp-stub.S
@@ -117,7 +116,8 @@ CFLAGS_fdt_ro.o := $(nossp-flags-y)
CFLAGS_fdt_rw.o := $(nossp-flags-y)
CFLAGS_fdt_wip.o := $(nossp-flags-y)
-ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin -I$(obj)
+ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin \
asflags-y := -DZIMAGE
# Supply kernel BSS size to the decompressor via a linker symbol.