Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull objtool fixes from Ingo Molnar:
 "A handful of objtool fixes related to unreachable code, plus a build
  fix for out of tree modules"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Enclose contents of unreachable() macro in a block
  objtool: Prevent GCC from merging annotate_unreachable()
  objtool: Improve detection of BUG() and other dead ends
  objtool: Fix CONFIG_STACK_VALIDATION=y warning for out-of-tree modules

3 files changed, 58 insertions, 10 deletions

diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index f7350fcedc70..a59e061c0b4a 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -31,9 +31,8 @@
 #define INSN_CALL_DYNAMIC	8
 #define INSN_RETURN		9
 #define INSN_CONTEXT_SWITCH	10
-#define INSN_BUG		11
-#define INSN_NOP		12
-#define INSN_OTHER		13
+#define INSN_NOP		11
+#define INSN_OTHER		12
 #define INSN_LAST		INSN_OTHER
 
 int arch_decode_instruction(struct elf *elf, struct section *sec,
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 039636ffb6c8..6ac99e3266eb 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -118,9 +118,6 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 			 op2 == 0x35)
 			/* sysenter, sysret */
 			*type = INSN_CONTEXT_SWITCH;
-		else if (op2 == 0x0b || op2 == 0xb9)
-			/* ud2 */
-			*type = INSN_BUG;
 		else if (op2 == 0x0d || op2 == 0x1f)
 			/* nopl/nopw */
 			*type = INSN_NOP;
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index e8a1f699058a..5fc52ee3264c 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -51,7 +51,7 @@ struct instruction {
 	unsigned int len, state;
 	unsigned char type;
 	unsigned long immediate;
-	bool alt_group, visited;
+	bool alt_group, visited, dead_end;
 	struct symbol *call_dest;
 	struct instruction *jump_dest;
 	struct list_head alts;
@@ -330,6 +330,54 @@ static int decode_instructions(struct objtool_file *file)
 }
 
 /*
+ * Find all uses of the unreachable() macro, which are code path dead ends.
+ */
+static int add_dead_ends(struct objtool_file *file)
+{
+	struct section *sec;
+	struct rela *rela;
+	struct instruction *insn;
+	bool found;
+
+	sec = find_section_by_name(file->elf, ".rela__unreachable");
+	if (!sec)
+		return 0;
+
+	list_for_each_entry(rela, &sec->rela_list, list) {
+		if (rela->sym->type != STT_SECTION) {
+			WARN("unexpected relocation symbol type in .rela__unreachable");
+			return -1;
+		}
+		insn = find_insn(file, rela->sym->sec, rela->addend);
+		if (insn)
+			insn = list_prev_entry(insn, list);
+		else if (rela->addend == rela->sym->sec->len) {
+			found = false;
+			list_for_each_entry_reverse(insn, &file->insn_list, list) {
+				if (insn->sec == rela->sym->sec) {
+					found = true;
+					break;
+				}
+			}
+
+			if (!found) {
+				WARN("can't find unreachable insn at %s+0x%x",
+				     rela->sym->sec->name, rela->addend);
+				return -1;
+			}
+		} else {
+			WARN("can't find unreachable insn at %s+0x%x",
+			     rela->sym->sec->name, rela->addend);
+			return -1;
+		}
+
+		insn->dead_end = true;
+	}
+
+	return 0;
+}
+
+/*
  * Warnings shouldn't be reported for ignored functions.
  */
 static void add_ignores(struct objtool_file *file)
@@ -843,6 +891,10 @@ static int decode_sections(struct objtool_file *file)
 	if (ret)
 		return ret;
 
+	ret = add_dead_ends(file);
+	if (ret)
+		return ret;
+
 	add_ignores(file);
 
 	ret = add_jump_destinations(file);
@@ -1037,13 +1089,13 @@ static int validate_branch(struct objtool_file *file,
 
 			return 0;
 
-		case INSN_BUG:
-			return 0;
-
 		default:
 			break;
 		}
 
+		if (insn->dead_end)
+			return 0;
+
 		insn = next_insn_same_sec(file, insn);
 		if (!insn) {
 			WARN("%s: unexpected end of section", sec->name);