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Date: Tue, 21 Sep 2021 02:07:17 +0800 From: Dan Li <ashimida@...ux.alibaba.com> To: Nathan Chancellor <nathan@...nel.org> Cc: masahiroy@...nel.org, michal.lkml@...kovi.net, keescook@...omium.org, ndesaulniers@...gle.com, akpm@...ux-foundation.org, tglx@...utronix.de, peterz@...radead.org, samitolvanen@...gle.com, frederic@...nel.org, rppt@...nel.org, yifeifz2@...inois.edu, viresh.kumar@...aro.org, colin.king@...onical.com, andreyknvl@...il.com, mark.rutland@....com, ojeda@...nel.org, will@...nel.org, ardb@...nel.org, luc.vanoostenryck@...il.com, elver@...gle.com, nivedita@...m.mit.edu, linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, clang-built-linux@...glegroups.com Subject: Re: [PATCH] [RFC/RFT]SCS:Add gcc plugin to support Shadow Call Stack 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 >
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