cfi_types.h

 1/* SPDX-License-Identifier: GPL-2.0 */
 2/*
 3 * Clang Control Flow Integrity (CFI) type definitions.
 4 */
 5#ifndef _LINUX_CFI_TYPES_H
 6#define _LINUX_CFI_TYPES_H
 7
 8#ifdef __ASSEMBLY__
 9#include <linux/linkage.h>
10
11#ifdef CONFIG_CFI
12/*
13 * Use the __kcfi_typeid_<function> type identifier symbol to
14 * annotate indirectly called assembly functions. The compiler emits
15 * these symbols for all address-taken function declarations in C
16 * code.
17 */
18#ifndef __CFI_TYPE
19#define __CFI_TYPE(name)				\
20	.4byte __kcfi_typeid_##name
21#endif
22
23#define SYM_TYPED_ENTRY(name, linkage, align...)	\
24	linkage(name) ASM_NL				\
25	align ASM_NL					\
26	__CFI_TYPE(name) ASM_NL				\
27	name:
28
29#define SYM_TYPED_START(name, linkage, align...)	\
30	SYM_TYPED_ENTRY(name, linkage, align)
31
32#else /* CONFIG_CFI */
33
34#define SYM_TYPED_START(name, linkage, align...)	\
35	SYM_START(name, linkage, align)
36
37#endif /* CONFIG_CFI */
38
39#ifndef SYM_TYPED_FUNC_START
40#define SYM_TYPED_FUNC_START(name) 			\
41	SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)
42#endif
43
44#else /* __ASSEMBLY__ */
45
46#ifdef CONFIG_CFI
47#define DEFINE_CFI_TYPE(name, func)						\
48	/*									\
49	 * Force a reference to the function so the compiler generates		\
50	 * __kcfi_typeid_<func>.						\
51	 */									\
52	__ADDRESSABLE(func);							\
53	/* u32 name __ro_after_init = __kcfi_typeid_<func> */			\
54	extern u32 name;							\
55	asm (									\
56	"	.pushsection	.data..ro_after_init,\"aw\",\%progbits	\n"	\
57	"	.type	" #name ",\%object				\n"	\
58	"	.globl	" #name "					\n"	\
59	"	.p2align	2, 0x0					\n"	\
60	#name ":							\n"	\
61	"	.4byte	__kcfi_typeid_" #func "				\n"	\
62	"	.size	" #name ", 4					\n"	\
63	"	.popsection						\n"	\
64	);
65#endif
66
67#endif /* __ASSEMBLY__ */
68#endif /* _LINUX_CFI_TYPES_H */