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 10 enum 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 29 static inline unsigned long trap_address(s32 *p) 30 { 31 return (unsigned long)((long)p + (long)*p); 32 } 33 34 static 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`. */ 48 void 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 69 static 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 */ 85 static inline bool is_module_cfi_trap(unsigned long addr) 86 { 87 return false; 88 } 89 #endif /* CONFIG_MODULES */ 90 91 extern s32 __start___kcfi_traps[]; 92 extern s32 __stop___kcfi_traps[]; 93 94 bool 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