mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-08-29 04:09:39 +00:00
Code Issues Releases Wiki Activity
linux-stable/include/linux/cfi_types.h

46 lines
1.1 KiB
C
Raw Normal View History

cfi: Add type helper macros With CONFIG_CFI_CLANG, assembly functions called indirectly from C code must be annotated with type identifiers to pass CFI checking. In order to make this easier, the compiler emits a __kcfi_typeid_<function> symbol for each address-taken function declaration in C, which contains the expected type identifier that we can refer to in assembly code. Add a typed version of SYM_FUNC_START, which emits the type identifier before the function. Architectures that support KCFI can define their own __CFI_TYPE macro to override the default preamble format. As an example, for the x86_64 blowfish_dec_blk function, the compiler emits the following type symbol: $ readelf -sW vmlinux | grep __kcfi_typeid_blowfish_dec_blk 120204: 00000000ef478db5 0 NOTYPE WEAK DEFAULT ABS __kcfi_typeid_blowfish_dec_blk And SYM_TYPED_FUNC_START will generate the following preamble based on the __CFI_TYPE definition for the architecture: $ objdump -dr arch/x86/crypto/blowfish-x86_64-asm_64.o ... 0000000000000400 <__cfi_blowfish_dec_blk>: ... 40b: b8 00 00 00 00 mov $0x0,%eax 40c: R_X86_64_32 __kcfi_typeid_blowfish_dec_blk 0000000000000410 <blowfish_dec_blk>: ... Note that the address of all assembly functions annotated with SYM_TYPED_FUNC_START must be taken in C code that's linked into the binary or the missing __kcfi_typeid_ symbol will result in a linker error with CONFIG_CFI_CLANG. If the code that contains the indirect call is not always compiled in, __ADDRESSABLE(functionname) can be used to ensure that the __kcfi_typeid_ symbol is emitted. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Kees Cook <keescook@chromium.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220908215504.3686827-7-samitolvanen@google.com
2022-09-08 21:54:48 +00:00
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Clang Control Flow Integrity (CFI) type definitions.
*/
#ifndef _LINUX_CFI_TYPES_H
#define _LINUX_CFI_TYPES_H
#ifdef __ASSEMBLY__
#include <linux/linkage.h>
#ifdef CONFIG_CFI_CLANG
/*
* 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, linkage, align...) \
linkage(name) ASM_NL \
align ASM_NL \
__CFI_TYPE(name) ASM_NL \
name:
#define SYM_TYPED_START(name, linkage, align...) \
SYM_TYPED_ENTRY(name, linkage, align)
#else /* CONFIG_CFI_CLANG */
#define SYM_TYPED_START(name, linkage, align...) \
SYM_START(name, linkage, align)
#endif /* CONFIG_CFI_CLANG */
#ifndef SYM_TYPED_FUNC_START
#define SYM_TYPED_FUNC_START(name) \
SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)
#endif
#endif /* __ASSEMBLY__ */
#endif /* _LINUX_CFI_TYPES_H */
Reference in a new issue Copy permalink