Messages in this thread Patch in this message | | | Date | Fri, 13 May 2022 13:21:45 -0700 | Subject | [RFC PATCH v2 07/21] cfi: Add type helper macros | From | Sami Tolvanen <> |
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With CONFIG_CFI_CLANG, assembly functions called indirectly from C code must be annotated with type identifiers to pass CFI checking. The compiler emits a __kcfi_typeid_<function> symbol for each address-taken function declaration in C, which contains the expected type identifier. Add typed versions of SYM_FUNC_START and SYM_FUNC_START_ALIAS, which emit the type identifier before the function.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com> --- include/linux/cfi_types.h | 57 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 include/linux/cfi_types.h
diff --git a/include/linux/cfi_types.h b/include/linux/cfi_types.h new file mode 100644 index 000000000000..dd16e755a197 --- /dev/null +++ b/include/linux/cfi_types.h @@ -0,0 +1,57 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Clang Control Flow Integrity (CFI) type definitions. + */ +#ifndef _LINUX_CFI_TYPES_H +#define _LINUX_CFI_TYPES_H + +#ifdef CONFIG_CFI_CLANG +#include <linux/linkage.h> + +#ifdef __ASSEMBLY__ +/* + * Use the __kcfi_typeid_<function> type identifier symbol to + * annotate indirectly called assembly functions. The compiler emits + * these symbols for all address-taken function declarations in C + * code. + */ +#ifndef __CFI_TYPE +#define __CFI_TYPE(name) \ + .4byte __kcfi_typeid_##name +#endif + +#define SYM_TYPED_ENTRY(name, fname, linkage, align...) \ + linkage(name) ASM_NL \ + align ASM_NL \ + __CFI_TYPE(fname) ASM_NL \ + name: + +#define __SYM_TYPED_FUNC_START_ALIAS(name, fname) \ + SYM_TYPED_ENTRY(name, fname, SYM_L_GLOBAL, SYM_A_ALIGN) + +#define __SYM_TYPED_FUNC_START(name, fname) \ + SYM_TYPED_ENTRY(name, fname, SYM_L_GLOBAL, SYM_A_ALIGN) + +#endif /* __ASSEMBLY__ */ + +#else /* CONFIG_CFI_CLANG */ + +#ifdef __ASSEMBLY__ +#define __SYM_TYPED_FUNC_START_ALIAS(name, fname) \ + SYM_FUNC_START_ALIAS(name) + +#define __SYM_TYPED_FUNC_START(name, fname) \ + SYM_FUNC_START(name) +#endif /* __ASSEMBLY__ */ + +#endif /* CONFIG_CFI_CLANG */ + +#ifdef __ASSEMBLY__ +#define SYM_TYPED_FUNC_START_ALIAS(name) \ + __SYM_TYPED_FUNC_START_ALIAS(name, name) + +#define SYM_TYPED_FUNC_START(name) \ + __SYM_TYPED_FUNC_START(name, name) +#endif /* __ASSEMBLY__ */ + +#endif /* _LINUX_CFI_TYPES_H */ -- 2.36.0.550.gb090851708-goog
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