1 files changed, 96 insertions, 47 deletions

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index f40d46e24bcc..a8cb69a26576 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -138,6 +138,7 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 		"__reiserfs_panic",
 		"lbug_with_loc",
 		"fortify_panic",
+		"usercopy_abort",
 	};
 
 	if (func->bind == STB_WEAK)
@@ -543,18 +544,14 @@ static int add_call_destinations(struct objtool_file *file)
 			dest_off = insn->offset + insn->len + insn->immediate;
 			insn->call_dest = find_symbol_by_offset(insn->sec,
 								dest_off);
-			/*
-			 * FIXME: Thanks to retpolines, it's now considered
-			 * normal for a function to call within itself.  So
-			 * disable this warning for now.
-			 */
-#if 0
-			if (!insn->call_dest) {
-				WARN_FUNC("can't find call dest symbol at offset 0x%lx",
-					  insn->sec, insn->offset, dest_off);
+
+			if (!insn->call_dest && !insn->ignore) {
+				WARN_FUNC("unsupported intra-function call",
+					  insn->sec, insn->offset);
+				WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
 				return -1;
 			}
-#endif
+
 		} else if (rela->sym->type == STT_SECTION) {
 			insn->call_dest = find_symbol_by_offset(rela->sym->sec,
 								rela->addend+4);
@@ -598,7 +595,7 @@ static int handle_group_alt(struct objtool_file *file,
 			    struct instruction *orig_insn,
 			    struct instruction **new_insn)
 {
-	struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump;
+	struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
 	unsigned long dest_off;
 
 	last_orig_insn = NULL;
@@ -614,28 +611,30 @@ static int handle_group_alt(struct objtool_file *file,
 		last_orig_insn = insn;
 	}
 
-	if (!next_insn_same_sec(file, last_orig_insn)) {
-		WARN("%s: don't know how to handle alternatives at end of section",
-		     special_alt->orig_sec->name);
-		return -1;
-	}
-
-	fake_jump = malloc(sizeof(*fake_jump));
-	if (!fake_jump) {
-		WARN("malloc failed");
-		return -1;
+	if (next_insn_same_sec(file, last_orig_insn)) {
+		fake_jump = malloc(sizeof(*fake_jump));
+		if (!fake_jump) {
+			WARN("malloc failed");
+			return -1;
+		}
+		memset(fake_jump, 0, sizeof(*fake_jump));
+		INIT_LIST_HEAD(&fake_jump->alts);
+		clear_insn_state(&fake_jump->state);
+
+		fake_jump->sec = special_alt->new_sec;
+		fake_jump->offset = -1;
+		fake_jump->type = INSN_JUMP_UNCONDITIONAL;
+		fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
+		fake_jump->ignore = true;
 	}
-	memset(fake_jump, 0, sizeof(*fake_jump));
-	INIT_LIST_HEAD(&fake_jump->alts);
-	clear_insn_state(&fake_jump->state);
-
-	fake_jump->sec = special_alt->new_sec;
-	fake_jump->offset = -1;
-	fake_jump->type = INSN_JUMP_UNCONDITIONAL;
-	fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
-	fake_jump->ignore = true;
 
 	if (!special_alt->new_len) {
+		if (!fake_jump) {
+			WARN("%s: empty alternative at end of section",
+			     special_alt->orig_sec->name);
+			return -1;
+		}
+
 		*new_insn = fake_jump;
 		return 0;
 	}
@@ -648,6 +647,8 @@ static int handle_group_alt(struct objtool_file *file,
 
 		last_new_insn = insn;
 
+		insn->ignore = orig_insn->ignore_alts;
+
 		if (insn->type != INSN_JUMP_CONDITIONAL &&
 		    insn->type != INSN_JUMP_UNCONDITIONAL)
 			continue;
@@ -656,8 +657,14 @@ static int handle_group_alt(struct objtool_file *file,
 			continue;
 
 		dest_off = insn->offset + insn->len + insn->immediate;
-		if (dest_off == special_alt->new_off + special_alt->new_len)
+		if (dest_off == special_alt->new_off + special_alt->new_len) {
+			if (!fake_jump) {
+				WARN("%s: alternative jump to end of section",
+				     special_alt->orig_sec->name);
+				return -1;
+			}
 			insn->jump_dest = fake_jump;
+		}
 
 		if (!insn->jump_dest) {
 			WARN_FUNC("can't find alternative jump destination",
@@ -672,7 +679,8 @@ static int handle_group_alt(struct objtool_file *file,
 		return -1;
 	}
 
-	list_add(&fake_jump->list, &last_new_insn->list);
+	if (fake_jump)
+		list_add(&fake_jump->list, &last_new_insn->list);
 
 	return 0;
 }
@@ -729,10 +737,6 @@ static int add_special_section_alts(struct objtool_file *file)
 			goto out;
 		}
 
-		/* Ignore retpoline alternatives. */
-		if (orig_insn->ignore_alts)
-			continue;
-
 		new_insn = NULL;
 		if (!special_alt->group || special_alt->new_len) {
 			new_insn = find_insn(file, special_alt->new_sec,
@@ -848,8 +852,14 @@ static int add_switch_table(struct objtool_file *file, struct symbol *func,
  *    This is a fairly uncommon pattern which is new for GCC 6.  As of this
  *    writing, there are 11 occurrences of it in the allmodconfig kernel.
  *
+ *    As of GCC 7 there are quite a few more of these and the 'in between' code
+ *    is significant. Esp. with KASAN enabled some of the code between the mov
+ *    and jmpq uses .rodata itself, which can confuse things.
+ *
  *    TODO: Once we have DWARF CFI and smarter instruction decoding logic,
  *    ensure the same register is used in the mov and jump instructions.
+ *
+ *    NOTE: RETPOLINE made it harder still to decode dynamic jumps.
  */
 static struct rela *find_switch_table(struct objtool_file *file,
 				      struct symbol *func,
@@ -871,12 +881,25 @@ static struct rela *find_switch_table(struct objtool_file *file,
 						text_rela->addend + 4);
 		if (!rodata_rela)
 			return NULL;
+
 		file->ignore_unreachables = true;
 		return rodata_rela;
 	}
 
 	/* case 3 */
-	func_for_each_insn_continue_reverse(file, func, insn) {
+	/*
+	 * Backward search using the @first_jump_src links, these help avoid
+	 * much of the 'in between' code. Which avoids us getting confused by
+	 * it.
+	 */
+	for (insn = list_prev_entry(insn, list);
+
+	     &insn->list != &file->insn_list &&
+	     insn->sec == func->sec &&
+	     insn->offset >= func->offset;
+
+	     insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
+
 		if (insn->type == INSN_JUMP_DYNAMIC)
 			break;
 
@@ -906,14 +929,32 @@ static struct rela *find_switch_table(struct objtool_file *file,
 	return NULL;
 }
 
+
 static int add_func_switch_tables(struct objtool_file *file,
 				  struct symbol *func)
 {
-	struct instruction *insn, *prev_jump = NULL;
+	struct instruction *insn, *last = NULL, *prev_jump = NULL;
 	struct rela *rela, *prev_rela = NULL;
 	int ret;
 
 	func_for_each_insn(file, func, insn) {
+		if (!last)
+			last = insn;
+
+		/*
+		 * Store back-pointers for unconditional forward jumps such
+		 * that find_switch_table() can back-track using those and
+		 * avoid some potentially confusing code.
+		 */
+		if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
+		    insn->offset > last->offset &&
+		    insn->jump_dest->offset > insn->offset &&
+		    !insn->jump_dest->first_jump_src) {
+
+			insn->jump_dest->first_jump_src = insn;
+			last = insn->jump_dest;
+		}
+
 		if (insn->type != INSN_JUMP_DYNAMIC)
 			continue;
 
@@ -1089,11 +1130,11 @@ static int decode_sections(struct objtool_file *file)
 	if (ret)
 		return ret;
 
-	ret = add_call_destinations(file);
+	ret = add_special_section_alts(file);
 	if (ret)
 		return ret;
 
-	ret = add_special_section_alts(file);
+	ret = add_call_destinations(file);
 	if (ret)
 		return ret;
 
@@ -1720,10 +1761,12 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
 
 		insn->visited = true;
 
-		list_for_each_entry(alt, &insn->alts, list) {
-			ret = validate_branch(file, alt->insn, state);
-			if (ret)
-				return 1;
+		if (!insn->ignore_alts) {
+			list_for_each_entry(alt, &insn->alts, list) {
+				ret = validate_branch(file, alt->insn, state);
+				if (ret)
+					return 1;
+			}
 		}
 
 		switch (insn->type) {
@@ -1893,13 +1936,19 @@ static bool ignore_unreachable_insn(struct instruction *insn)
 		if (is_kasan_insn(insn) || is_ubsan_insn(insn))
 			return true;
 
-		if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
-			insn = insn->jump_dest;
-			continue;
+		if (insn->type == INSN_JUMP_UNCONDITIONAL) {
+			if (insn->jump_dest &&
+			    insn->jump_dest->func == insn->func) {
+				insn = insn->jump_dest;
+				continue;
+			}
+
+			break;
 		}
 
 		if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
 			break;
+
 		insn = list_next_entry(insn, list);
 	}