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1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Clang Control Flow Integrity (CFI) support.
4 *
5 * Copyright (C) 2022 Google LLC
6 */
7#ifndef _LINUX_CFI_H
8#define _LINUX_CFI_H
9
10#include <linux/bug.h>
11#include <linux/module.h>
12#include <asm/cfi.h>
13
14#ifdef CONFIG_CFI
15extern bool cfi_warn;
16
17enum bug_trap_type report_cfi_failure(struct pt_regs *regs, unsigned long addr,
18 unsigned long *target, u32 type);
19
20static inline enum bug_trap_type report_cfi_failure_noaddr(struct pt_regs *regs,
21 unsigned long addr)
22{
23 return report_cfi_failure(regs, addr, NULL, 0);
24}
25
26#ifndef cfi_get_offset
27/*
28 * Returns the CFI prefix offset. By default, the compiler emits only
29 * a 4-byte CFI type hash before the function. If an architecture
30 * uses -fpatchable-function-entry=N,M where M>0 to change the prefix
31 * offset, they must override this function.
32 */
33static inline int cfi_get_offset(void)
34{
35 return 4;
36}
37#endif
38
39#ifndef cfi_get_func_hash
40static inline u32 cfi_get_func_hash(void *func)
41{
42 u32 hash;
43
44 if (get_kernel_nofault(hash, func - cfi_get_offset()))
45 return 0;
46
47 return hash;
48}
49#endif
50
51/* CFI type hashes for BPF function types */
52extern u32 cfi_bpf_hash;
53extern u32 cfi_bpf_subprog_hash;
54
55#else /* CONFIG_CFI */
56
57static inline int cfi_get_offset(void) { return 0; }
58static inline u32 cfi_get_func_hash(void *func) { return 0; }
59
60#define cfi_bpf_hash 0U
61#define cfi_bpf_subprog_hash 0U
62
63#endif /* CONFIG_CFI */
64
65#ifdef CONFIG_ARCH_USES_CFI_TRAPS
66bool is_cfi_trap(unsigned long addr);
67#else
68static inline bool is_cfi_trap(unsigned long addr) { return false; }
69#endif
70
71#ifdef CONFIG_MODULES
72#ifdef CONFIG_ARCH_USES_CFI_TRAPS
73void module_cfi_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
74 struct module *mod);
75#else
76static inline void module_cfi_finalize(const Elf_Ehdr *hdr,
77 const Elf_Shdr *sechdrs,
78 struct module *mod) {}
79#endif /* CONFIG_ARCH_USES_CFI_TRAPS */
80#endif /* CONFIG_MODULES */
81
82#ifndef CFI_NOSEAL
83#define CFI_NOSEAL(x)
84#endif
85
86#endif /* _LINUX_CFI_H */