Shadow call stacks will be available in GCC >= 12, this patch makes the corresponding kernel configuration available when compiling the kernel with the gcc.
Note that the implementation in GCC is slightly different from Clang. With SCS enabled, functions will only pop x30 once in the epilogue, like:
str x30, [x18], #8 stp x29, x30, [sp, #-16]! ...... - ldp x29, x30, [sp], #16 //clang + ldr x29, [sp], #16 //GCC ldr x30, [x18, #-8]!
Link: https://gcc.gnu.org/git/?p=gcc.git%3Ba=commit%3Bh=ce09ab17ddd21f73ff2caf6eec...
Reviewed-by: Nathan Chancellor nathan@kernel.org Reviewed-by: Kees Cook keescook@chromium.org Reviewed-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Dan Li ashimida@linux.alibaba.com --- arch/Kconfig | 19 ++++++++++--------- arch/arm64/Kconfig | 2 +- include/linux/compiler-gcc.h | 4 ++++ 3 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig index 678a80713b21..cbbe824fe8b2 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -599,21 +599,22 @@ config STACKPROTECTOR_STRONG config ARCH_SUPPORTS_SHADOW_CALL_STACK bool help - An architecture should select this if it supports Clang's Shadow - Call Stack and implements runtime support for shadow stack + An architecture should select this if it supports the compiler's + Shadow Call Stack and implements runtime support for shadow stack switching.
config SHADOW_CALL_STACK - bool "Clang Shadow Call Stack" - depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK + bool "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 - shadow stack to protect function return addresses from being - overwritten by an attacker. More information can be found in - Clang's documentation: + This option enables the compiler's Shadow Call Stack, which + uses a shadow stack to protect function return addresses from + being overwritten by an attacker. More information can be found + in the compiler's documentation:
- https://clang.llvm.org/docs/ShadowCallStack.html + - Clang: https://clang.llvm.org/docs/ShadowCallStack.html + - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentat...
Note that security guarantees in the kernel differ from the ones documented for user space. The kernel must store addresses diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 09b885cc4db5..b7145337efae 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1255,7 +1255,7 @@ config HW_PERF_EVENTS config ARCH_HAS_FILTER_PGPROT def_bool y
-# Supported by clang >= 7.0 +# Supported by clang >= 7.0 or GCC >= 12.0.0 config CC_HAVE_SHADOW_CALL_STACK def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index ccbbd31b3aae..deff5b308470 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -97,6 +97,10 @@ #define KASAN_ABI_VERSION 4 #endif
+#ifdef CONFIG_SHADOW_CALL_STACK +#define __noscs __attribute__((__no_sanitize__("shadow-call-stack"))) +#endif + #if __has_attribute(__no_sanitize_address__) #define __no_sanitize_address __attribute__((no_sanitize_address)) #else