1 files changed, 101 insertions, 0 deletions
diff --git a/kernel/cfi.c b/kernel/cfi.c
new file mode 100644
index 000000000000..08caad776717
--- /dev/null
+++ b/kernel/cfi.c
@@ -0,0 +1,101 @@
+// 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 */