From e6f3b3c9c109ed57230996cf4a4c1b8ae7e36a81 Mon Sep 17 00:00:00 2001 From: Sami Tolvanen Date: Tue, 5 Apr 2022 15:16:18 -0700 Subject: [PATCH] cfi: Use __builtin_function_start Clang 14 added support for the __builtin_function_start function, which allows us to implement the function_nocfi macro without architecture-specific inline assembly and in a way that also works with static initializers. Change CONFIG_CFI_CLANG to depend on Clang >= 14, define function_nocfi using __builtin_function_start, and remove the arm64 inline assembly implementation. Link: https://github.com/llvm/llvm-project/commit/ec2e26eaf63558934f5b73a6e530edc453cf9508 Link: https://github.com/ClangBuiltLinux/linux/issues/1353 Signed-off-by: Sami Tolvanen Reviewed-by: Nick Desaulniers Reviewed-by: Mark Rutland Tested-by: Mark Rutland Acked-by: Will Deacon # arm64 Reviewed-by: Nathan Chancellor Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220405221618.633743-1-samitolvanen@google.com --- arch/Kconfig | 5 +---- arch/arm64/include/asm/compiler.h | 16 ---------------- include/linux/compiler-clang.h | 10 ++++++++++ 3 files changed, 11 insertions(+), 20 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 29b0167c088b..c1627bce4a3a 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -723,10 +723,7 @@ config ARCH_SUPPORTS_CFI_CLANG config CFI_CLANG bool "Use Clang's Control Flow Integrity (CFI)" depends on LTO_CLANG && ARCH_SUPPORTS_CFI_CLANG - # Clang >= 12: - # - https://bugs.llvm.org/show_bug.cgi?id=46258 - # - https://bugs.llvm.org/show_bug.cgi?id=47479 - depends on CLANG_VERSION >= 120000 + depends on CLANG_VERSION >= 140000 select KALLSYMS help This option enables Clang’s forward-edge Control Flow Integrity diff --git a/arch/arm64/include/asm/compiler.h b/arch/arm64/include/asm/compiler.h index dc3ea4080e2e..6fb2e6bcc392 100644 --- a/arch/arm64/include/asm/compiler.h +++ b/arch/arm64/include/asm/compiler.h @@ -23,20 +23,4 @@ #define __builtin_return_address(val) \ (void *)(ptrauth_clear_pac((unsigned long)__builtin_return_address(val))) -#ifdef CONFIG_CFI_CLANG -/* - * With CONFIG_CFI_CLANG, the compiler replaces function address - * references with the address of the function's CFI jump table - * entry. The function_nocfi macro always returns the address of the - * actual function instead. - */ -#define function_nocfi(x) ({ \ - void *addr; \ - asm("adrp %0, " __stringify(x) "\n\t" \ - "add %0, %0, :lo12:" __stringify(x) \ - : "=r" (addr)); \ - addr; \ -}) -#endif - #endif /* __ASM_COMPILER_H */ diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h index babb1347148c..c84fec767445 100644 --- a/include/linux/compiler-clang.h +++ b/include/linux/compiler-clang.h @@ -69,6 +69,16 @@ #define __nocfi __attribute__((__no_sanitize__("cfi"))) #define __cficanonical __attribute__((__cfi_canonical_jump_table__)) +#if defined(CONFIG_CFI_CLANG) +/* + * With CONFIG_CFI_CLANG, the compiler replaces function address + * references with the address of the function's CFI jump table + * entry. The function_nocfi macro always returns the address of the + * actual function instead. + */ +#define function_nocfi(x) __builtin_function_start(x) +#endif + /* * Turn individual warnings and errors on and off locally, depending * on version.