1 files changed, 194 insertions, 51 deletions

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index f40d46e24bcc..5409f6f6c48d 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -18,6 +18,7 @@
 #include <string.h>
 #include <stdlib.h>
 
+#include "builtin.h"
 #include "check.h"
 #include "elf.h"
 #include "special.h"
@@ -33,7 +34,6 @@ struct alternative {
 };
 
 const char *objname;
-static bool no_fp;
 struct cfi_state initial_func_cfi;
 
 struct instruction *find_insn(struct objtool_file *file,
@@ -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)
@@ -496,6 +497,7 @@ static int add_jump_destinations(struct objtool_file *file)
 			 * disguise, so convert them accordingly.
 			 */
 			insn->type = INSN_JUMP_DYNAMIC;
+			insn->retpoline_safe = true;
 			continue;
 		} else {
 			/* sibling call */
@@ -543,18 +545,15 @@ 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);
+				if (retpoline)
+					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 +597,7 @@ 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 +613,30 @@ 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 +649,8 @@ 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 +659,14 @@ 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 +681,8 @@ 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 +739,6 @@ 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 +854,14 @@ 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 +883,25 @@ 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;
 
@@ -900,20 +925,42 @@ static struct rela *find_switch_table(struct objtool_file *file,
 		if (find_symbol_containing(file->rodata, text_rela->addend))
 			continue;
 
-		return find_rela_by_dest(file->rodata, text_rela->addend);
+		rodata_rela = find_rela_by_dest(file->rodata, text_rela->addend);
+		if (!rodata_rela)
+			continue;
+
+		return rodata_rela;
 	}
 
 	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;
 
@@ -1067,6 +1114,41 @@ static int read_unwind_hints(struct objtool_file *file)
 	return 0;
 }
 
+static int read_retpoline_hints(struct objtool_file *file)
+{
+	struct section *sec;
+	struct instruction *insn;
+	struct rela *rela;
+
+	sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
+	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 %s", sec->name);
+			return -1;
+		}
+
+		insn = find_insn(file, rela->sym->sec, rela->addend);
+		if (!insn) {
+			WARN("bad .discard.retpoline_safe entry");
+			return -1;
+		}
+
+		if (insn->type != INSN_JUMP_DYNAMIC &&
+		    insn->type != INSN_CALL_DYNAMIC) {
+			WARN_FUNC("retpoline_safe hint not an indirect jump/call",
+				  insn->sec, insn->offset);
+			return -1;
+		}
+
+		insn->retpoline_safe = true;
+	}
+
+	return 0;
+}
+
 static int decode_sections(struct objtool_file *file)
 {
 	int ret;
@@ -1089,11 +1171,11 @@ 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;
 
@@ -1105,6 +1187,10 @@ static int decode_sections(struct objtool_file *file)
 	if (ret)
 		return ret;
 
+	ret = read_retpoline_hints(file);
+	if (ret)
+		return ret;
+
 	return 0;
 }
 
@@ -1300,6 +1386,17 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
 				state->vals[op->dest.reg].offset = -state->stack_size;
 			}
 
+			else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
+				 cfa->base == CFI_BP) {
+
+				/*
+				 * mov %rbp, %rsp
+				 *
+				 * Restore the original stack pointer (Clang).
+				 */
+				state->stack_size = -state->regs[CFI_BP].offset;
+			}
+
 			else if (op->dest.reg == cfa->base) {
 
 				/* mov %reg, %rsp */
@@ -1720,10 +1817,12 @@ 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) {
@@ -1848,6 +1947,38 @@ static int validate_unwind_hints(struct objtool_file *file)
 	return warnings;
 }
 
+static int validate_retpoline(struct objtool_file *file)
+{
+	struct instruction *insn;
+	int warnings = 0;
+
+	for_each_insn(file, insn) {
+		if (insn->type != INSN_JUMP_DYNAMIC &&
+		    insn->type != INSN_CALL_DYNAMIC)
+			continue;
+
+		if (insn->retpoline_safe)
+			continue;
+
+		/*
+		 * .init.text code is ran before userspace and thus doesn't
+		 * strictly need retpolines, except for modules which are
+		 * loaded late, they very much do need retpoline in their
+		 * .init.text
+		 */
+		if (!strcmp(insn->sec->name, ".init.text") && !module)
+			continue;
+
+		WARN_FUNC("indirect %s found in RETPOLINE build",
+			  insn->sec, insn->offset,
+			  insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
+
+		warnings++;
+	}
+
+	return warnings;
+}
+
 static bool is_kasan_insn(struct instruction *insn)
 {
 	return (insn->type == INSN_CALL &&
@@ -1893,13 +2024,19 @@ 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);
 	}
 
@@ -1973,13 +2110,12 @@ static void cleanup(struct objtool_file *file)
 	elf_close(file->elf);
 }
 
-int check(const char *_objname, bool _no_fp, bool no_unreachable, bool orc)
+int check(const char *_objname, bool orc)
 {
 	struct objtool_file file;
 	int ret, warnings = 0;
 
 	objname = _objname;
-	no_fp = _no_fp;
 
 	file.elf = elf_open(objname, orc ? O_RDWR : O_RDONLY);
 	if (!file.elf)
@@ -2003,6 +2139,13 @@ int check(const char *_objname, bool _no_fp, bool no_unreachable, bool orc)
 	if (list_empty(&file.insn_list))
 		goto out;
 
+	if (retpoline) {
+		ret = validate_retpoline(&file);
+		if (ret < 0)
+			return ret;
+		warnings += ret;
+	}
+
 	ret = validate_functions(&file);
 	if (ret < 0)
 		goto out;