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- // SPDX-License-Identifier: GPL-2.0
- /*
- * Clang Control Flow Integrity (CFI) error handling.
- *
- * Copyright (C) 2022 Google LLC
- */
- #include <linux/cfi.h>
- enum bug_trap_type report_cfi_failure(struct pt_regs *regs, unsigned long addr,
- unsigned long *target, u32 type)
- {
- if (target)
- pr_err("CFI failure at %pS (target: %pS; expected type: 0x%08x)\n",
- (void *)addr, (void *)*target, type);
- else
- pr_err("CFI failure at %pS (no target information)\n",
- (void *)addr);
- if (IS_ENABLED(CONFIG_CFI_PERMISSIVE)) {
- __warn(NULL, 0, (void *)addr, 0, regs, NULL);
- return BUG_TRAP_TYPE_WARN;
- }
- return BUG_TRAP_TYPE_BUG;
- }
- #ifdef CONFIG_ARCH_USES_CFI_TRAPS
- static inline unsigned long trap_address(s32 *p)
- {
- return (unsigned long)((long)p + (long)*p);
- }
- static bool is_trap(unsigned long addr, s32 *start, s32 *end)
- {
- s32 *p;
- for (p = start; p < end; ++p) {
- if (trap_address(p) == addr)
- return true;
- }
- return false;
- }
- #ifdef CONFIG_MODULES
- /* Populates `kcfi_trap(_end)?` fields in `struct module`. */
- void module_cfi_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
- struct module *mod)
- {
- char *secstrings;
- unsigned int i;
- mod->kcfi_traps = NULL;
- mod->kcfi_traps_end = NULL;
- secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
- for (i = 1; i < hdr->e_shnum; i++) {
- if (strcmp(secstrings + sechdrs[i].sh_name, "__kcfi_traps"))
- continue;
- mod->kcfi_traps = (s32 *)sechdrs[i].sh_addr;
- mod->kcfi_traps_end = (s32 *)(sechdrs[i].sh_addr + sechdrs[i].sh_size);
- break;
- }
- }
- static bool is_module_cfi_trap(unsigned long addr)
- {
- struct module *mod;
- bool found = false;
- rcu_read_lock_sched_notrace();
- mod = __module_address(addr);
- if (mod)
- found = is_trap(addr, mod->kcfi_traps, mod->kcfi_traps_end);
- rcu_read_unlock_sched_notrace();
- return found;
- }
- #else /* CONFIG_MODULES */
- static inline bool is_module_cfi_trap(unsigned long addr)
- {
- return false;
- }
- #endif /* CONFIG_MODULES */
- extern s32 __start___kcfi_traps[];
- extern s32 __stop___kcfi_traps[];
- bool is_cfi_trap(unsigned long addr)
- {
- if (is_trap(addr, __start___kcfi_traps, __stop___kcfi_traps))
- return true;
- return is_module_cfi_trap(addr);
- }
- #endif /* CONFIG_ARCH_USES_CFI_TRAPS */
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