1// SPDX-License-Identifier: GPL-2.0 2/* 3 * Clang Control Flow Integrity (CFI) error handling. 4 * 5 * Copyright (C) 2022 Google LLC 6 */ 7 8#include <linux/cfi.h> 9 10enum bug_trap_type report_cfi_failure(struct pt_regs *regs, unsigned long addr, 11 unsigned long *target, u32 type) 12{ 13 if (target) 14 pr_err("CFI failure at %pS (target: %pS; expected type: 0x%08x)\n", 15 (void *)addr, (void *)*target, type); 16 else 17 pr_err("CFI failure at %pS (no target information)\n", 18 (void *)addr); 19 20 if (IS_ENABLED(CONFIG_CFI_PERMISSIVE)) { 21 __warn(NULL, 0, (void *)addr, 0, regs, NULL); 22 return BUG_TRAP_TYPE_WARN; 23 } 24 25 return BUG_TRAP_TYPE_BUG; 26} 27 28#ifdef CONFIG_ARCH_USES_CFI_TRAPS 29static inline unsigned long trap_address(s32 *p) 30{ 31 return (unsigned long)((long)p + (long)*p); 32} 33 34static bool is_trap(unsigned long addr, s32 *start, s32 *end) 35{ 36 s32 *p; 37 38 for (p = start; p < end; ++p) { 39 if (trap_address(p) == addr) 40 return true; 41 } 42 43 return false; 44} 45 46#ifdef CONFIG_MODULES 47/* Populates `kcfi_trap(_end)?` fields in `struct module`. */ 48void module_cfi_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, 49 struct module *mod) 50{ 51 char *secstrings; 52 unsigned int i; 53 54 mod->kcfi_traps = NULL; 55 mod->kcfi_traps_end = NULL; 56 57 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 58 59 for (i = 1; i < hdr->e_shnum; i++) { 60 if (strcmp(secstrings + sechdrs[i].sh_name, "__kcfi_traps")) 61 continue; 62 63 mod->kcfi_traps = (s32 *)sechdrs[i].sh_addr; 64 mod->kcfi_traps_end = (s32 *)(sechdrs[i].sh_addr + sechdrs[i].sh_size); 65 break; 66 } 67} 68 69static bool is_module_cfi_trap(unsigned long addr) 70{ 71 struct module *mod; 72 bool found = false; 73 74 rcu_read_lock_sched_notrace(); 75 76 mod = __module_address(addr); 77 if (mod) 78 found = is_trap(addr, mod->kcfi_traps, mod->kcfi_traps_end); 79 80 rcu_read_unlock_sched_notrace(); 81 82 return found; 83} 84#else /* CONFIG_MODULES */ 85static inline bool is_module_cfi_trap(unsigned long addr) 86{ 87 return false; 88} 89#endif /* CONFIG_MODULES */ 90 91extern s32 __start___kcfi_traps[]; 92extern s32 __stop___kcfi_traps[]; 93 94bool is_cfi_trap(unsigned long addr) 95{ 96 if (is_trap(addr, __start___kcfi_traps, __stop___kcfi_traps)) 97 return true; 98 99 return is_module_cfi_trap(addr); 100} 101#endif /* CONFIG_ARCH_USES_CFI_TRAPS */ 102