Hi Nathan,
Thanks for your comments.
I rewrite the configuration as follows:
1) Change the plugin to be enabled by default, and add this option to CC_FLAGS_SCS to keep its behavior consistent with clang
---
diff --git a/Makefile b/Makefile
@@ -923,12 +923,6 @@ KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
-ifdef CONFIG_SHADOW_CALL_STACK
-CC_FLAGS_SCS := -fsanitize=shadow-call-stack
-KBUILD_CFLAGS += $(CC_FLAGS_SCS)
-export CC_FLAGS_SCS
-endif
@@ -1034,6 +1028,20 @@ include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins
include $(addprefix $(srctree)/, $(include-y))
+ifdef CONFIG_SHADOW_CALL_STACK
+
+ifdef CONFIG_CC_IS_CLANG
+CC_FLAGS_SCS := -fsanitize=shadow-call-stack
+endif
+
+ifdef CONFIG_CC_IS_GCC
+CC_FLAGS_SCS := $(ENABLE_SHADOW_CALL_STACK_PLUGIN)
+endif
+
+KBUILD_CFLAGS += $(CC_FLAGS_SCS)
+export CC_FLAGS_SCS
+endif
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
@@ -46,6 +46,13 @@ ifdef CONFIG_GCC_PLUGIN_ARM_SSP_PER_TASK
+gcc-plugin-$(CONFIG_GCC_PLUGIN_SHADOW_CALL_STACK) += arm64_scs_plugin.so
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_SHADOW_CALL_STACK) \
+ += -DSHADOW_CALL_STACK_PLUGIN
+ifdef CONFIG_GCC_PLUGIN_SHADOW_CALL_STACK
+ ENABLE_SHADOW_CALL_STACK_PLUGIN += -fplugin-arg-arm64_scs_plugin-enable
+endif
2) Whether SCS is turned on or not is determined by CONFIG_SHADOW_CALL_STACK
* GCC_PLUGIN_SHADOW_CALL_STACK is only used to indicate whether current platform needs the support of the gcc SCS plugin
- It only enabled on ARM64 platform with gcc which does not support SCS(!CC_HAVE_SHADOW_CALL_STACK)
- If one compiler supports SCS (clang or gcc), then CC_HAVE_SHADOW_CALL_STACK should be true at this time, and the plugin is automatically closed
* As long as the current platform can support SCS(compiler or plugin), ARCH_SUPPORTS_SHADOW_CALL_STACK is always selected
* CONFIG_SHADOW_CALL_STACK no longer depends on CC_IS_CLANG
---
diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
@@ -19,6 +19,15 @@ menuconfig GCC_PLUGINS
+config GCC_PLUGIN_SHADOW_CALL_STACK
+ bool "GCC Shadow Call Stack plugin"
+ depends on (!CC_HAVE_SHADOW_CALL_STACK) && ARM64
+ default y
+ help ....
diff --git a/arch/Kconfig b/arch/Kconfig
@@ -594,7 +594,7 @@ config ARCH_SUPPORTS_SHADOW_CALL_STACK
config SHADOW_CALL_STACK
bool "Clang Shadow Call Stack"
- depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
+ depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
help
This option enables Clang's Shadow Call Stack, which uses a
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
@@ -81,7 +81,7 @@ config ARM64
- select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK
+ select ARCH_SUPPORTS_SHADOW_CALL_STACK if (CC_HAVE_SHADOW_CALL_STACK || GCC_PLUGIN_SHADOW_CALL_STACK)
select ARCH_SUPPORTS_LTO_CLANG if CPU_LITTLE_ENDIAN
@@ -1060,9 +1060,13 @@ config HW_PERF_EVENTS
# Supported by clang >= 7.0
config CC_HAVE_SHADOW_CALL_STACK
- def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)
+ def_bool (CC_IS_CLANG && $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18))
On 9/20/21 5:45 AM, Nathan Chancellor wrote:
Hi Dan,
diff --git a/Makefile b/Makefile
ifdef CONFIG_SHADOW_CALL_STACK
I would rather see this become
ifeq ($(CONFIG_SHADOW_CALL_STACK)$(CONFIG_CC_IS_CLANG), yy)
...
endif
rather than just avoiding assigning to CC_FLAGS_SCS.
However, how does disabling the shadow call stack plugin work for a
whole translation unit or directory? There are a few places where
CC_FLAGS_SCS are filtered out and I am not sure I see where that happens
here? It looks like the plugin has a disabled option but I do not see it
hooked in anywhere.
In the new code, translation unit can only enable SCS when CC_FLAGS_SCS is specified.
This behavior will be consistent with clang.
If there are other problems in the future, those two can be modified together.
-CC_FLAGS_SCS := -fsanitize=shadow-call-stack
+CC_FLAGS_SCS := $(if $(CONFIG_CC_IS_CLANG),-fsanitize=shadow-call-stack,)
KBUILD_CFLAGS += $(CC_FLAGS_SCS)
export CC_FLAGS_SCS
endif
diff --git a/arch/Kconfig b/arch/Kconfig
index 98db634..81ff127 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -594,7 +594,7 @@ config ARCH_SUPPORTS_SHADOW_CALL_STACK
config SHADOW_CALL_STACK
bool "Clang Shadow Call Stack"
- depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
+ depends on (CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK) || GCC_PLUGIN_SHADOW_CALL_STACK
Is this logic right? SHADOW_CALL_STACK is only supported by arm64 (as
they set ARCH_SUPPORTS_SHADOW_CALL_STACK) but now you are enabling it
for any architecture, even though it seems like it still only works on
arm64. I think this wants to be
depends on (CC_IS_CLANG || GCC_PLUGIN_SHADOW_CALL_STACK) && ARCH_SUPPORTS_SHADOW_CALL_STACK
It's modified to rely only on ARCH_SUPPORTS_SHADOW_CALL_STACK
--- a/scripts/gcc-plugins/Kconfig
+++ b/scripts/gcc-plugins/Kconfig
@@ -19,6 +19,14 @@ menuconfig GCC_PLUGINS
if GCC_PLUGINS
+config GCC_PLUGIN_SHADOW_CALL_STACK
+ bool "GCC Shadow Call Stack plugin"
This should also have a
depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
if you are selecting SHADOW_CALL_STACK, as selecting does not account
for dependencies.
Select is removed from the code above
+ select SHADOW_CALL_STACK
+ help
+ This plugin is used to support the kernel CONFIG_SHADOW_CALL_STACK
+ compiled by gcc. Its principle is basically the same as that of CLANG.
+ For more information, please refer to "config SHADOW_CALL_STACK"
+
config GCC_PLUGIN_CYC_COMPLEXITY
bool "Compute the cyclomatic complexity of a function" if EXPERT
depends on !COMPILE_TEST # too noisy
Cheers,
Nathan
