[PATCH 0/3] objtool: GCC 8 support

[PATCH 0/3] objtool: GCC 8 support

[Josh Poimboeuf]

Now that GCC 8 is out, several people have complained about a bunch of
objtool warnings.  These patches fix all known warnings.

Patch 1 is a repost of a previous fix -- unrelated to GCC 8, but a
prereq for the following two patches.

Patch 2 fixes the vast majority of the warnings, caused by GCC 8's new
usage of "cold" subfunctions for unlikely text.

Patch 3 fixes a few more warnings, related to switch tables.

Josh Poimboeuf (3):
  objtool: Fix "noreturn" detection for recursive sibling calls
  objtool: Support GCC 8 cold subfunctions
  objtool: Support GCC 8 switch tables

 tools/objtool/check.c | 125 ++++++++++++++++++++++++++----------------
 tools/objtool/elf.c   |  42 +++++++++++++-
 tools/objtool/elf.h   |   2 +
 3 files changed, 121 insertions(+), 48 deletions(-)

-- 
2.17.0

[PATCH 1/3] objtool: Fix "noreturn" detection for recursive sibling calls

[Josh Poimboeuf]

Objtool has some crude logic for detecting static "noreturn" functions
(aka "dead ends").  This is necessary for being able to correctly follow
GCC code flow when such functions are called.

It's remotely possible for two functions to call each other via sibling
calls.  If they don't have RET instructions, objtool's noreturn
detection logic goes into a recursive loop:

  drivers/char/ipmi/ipmi_ssif.o: warning: objtool: return_hosed_msg()+0x0: infinite recursion (objtool bug!)
  drivers/char/ipmi/ipmi_ssif.o: warning: objtool: deliver_recv_msg()+0x0: infinite recursion (objtool bug!)

Instead of reporting an error in this case, consider the functions to be
non-dead-ends.

Reported-and-tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 tools/objtool/check.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5409f6f6c48d..264522d4e4af 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -190,9 +190,13 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 					continue;
 
 				if (recursion == 5) {
-					WARN_FUNC("infinite recursion (objtool bug!)",
-						  dest->sec, dest->offset);
-					return -1;
+					/*
+					 * Infinite recursion: two functions
+					 * have sibling calls to each other.
+					 * This is a very rare case.  It means
+					 * they aren't dead ends.
+					 */
+					return 0;
 				}
 
 				return __dead_end_function(file, dest_func,
-- 
2.17.0

[tip:core/urgent] objtool: Fix "noreturn" detection for recursive sibling calls

[tip-bot for Josh Poimboeuf]

Commit-ID:  0afd0d9e0e7879d666c1df2fa1bea4d8716909fe
Gitweb:     https://git.kernel.org/tip/0afd0d9e0e7879d666c1df2fa1bea4d8716909fe
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Wed, 9 May 2018 22:39:14 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 14 May 2018 10:20:53 +0200

objtool: Fix "noreturn" detection for recursive sibling calls

Objtool has some crude logic for detecting static "noreturn" functions
(aka "dead ends").  This is necessary for being able to correctly follow
GCC code flow when such functions are called.

It's remotely possible for two functions to call each other via sibling
calls.  If they don't have RET instructions, objtool's noreturn
detection logic goes into a recursive loop:

  drivers/char/ipmi/ipmi_ssif.o: warning: objtool: return_hosed_msg()+0x0: infinite recursion (objtool bug!)
  drivers/char/ipmi/ipmi_ssif.o: warning: objtool: deliver_recv_msg()+0x0: infinite recursion (objtool bug!)

Instead of reporting an error in this case, consider the functions to be
non-dead-ends.

Reported-and-tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: damian <damian.tometzki@icloud.com>
Link: http://lkml.kernel.org/r/7cc156408c5781a1f62085d352ced1fe39fe2f91.1525923412.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/objtool/check.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5409f6f6c48d..264522d4e4af 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -190,9 +190,13 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 					continue;
 
 				if (recursion == 5) {
-					WARN_FUNC("infinite recursion (objtool bug!)",
-						  dest->sec, dest->offset);
-					return -1;
+					/*
+					 * Infinite recursion: two functions
+					 * have sibling calls to each other.
+					 * This is a very rare case.  It means
+					 * they aren't dead ends.
+					 */
+					return 0;
 				}
 
 				return __dead_end_function(file, dest_func,

[PATCH 2/3] objtool: Support GCC 8 cold subfunctions

[Josh Poimboeuf]

GCC 8 moves a lot of unlikely code out of line to "cold" subfunctions in
.text.unlikely.  Properly detect the new subfunctions and treat them as
extensions of the original functions.

This fixes a bunch of warnings like:

  kernel/cgroup/cgroup.o: warning: objtool: parse_cgroup_root_flags()+0x33: sibling call from callable instruction with modified stack frame
  kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files()+0x290: sibling call from callable instruction with modified stack frame
  kernel/cgroup/cgroup.o: warning: objtool: cgroup_apply_control_enable()+0x25b: sibling call from callable instruction with modified stack frame
  kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems()+0x325: sibling call from callable instruction with modified stack frame

Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-and-tested-by: damian <damian.tometzki@icloud.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 tools/objtool/check.c | 93 ++++++++++++++++++++++++-------------------
 tools/objtool/elf.c   | 42 ++++++++++++++++++-
 tools/objtool/elf.h   |  2 +
 3 files changed, 93 insertions(+), 44 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 264522d4e4af..14daf6a27d9f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -59,6 +59,31 @@ static struct instruction *next_insn_same_sec(struct objtool_file *file,
 	return next;
 }
 
+static struct instruction *next_insn_same_func(struct objtool_file *file,
+					       struct instruction *insn)
+{
+	struct instruction *next = list_next_entry(insn, list);
+	struct symbol *func = insn->func;
+
+	if (!func)
+		return NULL;
+
+	if (&next->list != &file->insn_list && next->func == func)
+		return next;
+
+	/* Check if we're already in the subfunction: */
+	if (func == func->cfunc)
+		return NULL;
+
+	/* Move to the subfunction: */
+	return find_insn(file, func->cfunc->sec, func->cfunc->offset);
+}
+
+#define func_for_each_insn_all(file, func, insn)			\
+	for (insn = find_insn(file, func->sec, func->offset);		\
+	     insn;							\
+	     insn = next_insn_same_func(file, insn))
+
 #define func_for_each_insn(file, func, insn)				\
 	for (insn = find_insn(file, func->sec, func->offset);		\
 	     insn && &insn->list != &file->insn_list &&			\
@@ -149,10 +174,14 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 			if (!strcmp(func->name, global_noreturns[i]))
 				return 1;
 
-	if (!func->sec)
+	if (!func->len)
 		return 0;
 
-	func_for_each_insn(file, func, insn) {
+	insn = find_insn(file, func->sec, func->offset);
+	if (!insn->func)
+		return 0;
+
+	func_for_each_insn_all(file, func, insn) {
 		empty = false;
 
 		if (insn->type == INSN_RETURN)
@@ -167,28 +196,17 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 	 * case, the function's dead-end status depends on whether the target
 	 * of the sibling call returns.
 	 */
-	func_for_each_insn(file, func, insn) {
-		if (insn->sec != func->sec ||
-		    insn->offset >= func->offset + func->len)
-			break;
-
+	func_for_each_insn_all(file, func, insn) {
 		if (insn->type == INSN_JUMP_UNCONDITIONAL) {
 			struct instruction *dest = insn->jump_dest;
-			struct symbol *dest_func;
 
 			if (!dest)
 				/* sibling call to another file */
 				return 0;
 
-			if (dest->sec != func->sec ||
-			    dest->offset < func->offset ||
-			    dest->offset >= func->offset + func->len) {
-				/* local sibling call */
-				dest_func = find_symbol_by_offset(dest->sec,
-								  dest->offset);
-				if (!dest_func)
-					continue;
+			if (dest->func && dest->func->pfunc != insn->func->pfunc) {
 
+				/* local sibling call */
 				if (recursion == 5) {
 					/*
 					 * Infinite recursion: two functions
@@ -199,7 +217,7 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 					return 0;
 				}
 
-				return __dead_end_function(file, dest_func,
+				return __dead_end_function(file, dest->func,
 							   recursion + 1);
 			}
 		}
@@ -426,7 +444,7 @@ static void add_ignores(struct objtool_file *file)
 			if (!ignore_func(file, func))
 				continue;
 
-			func_for_each_insn(file, func, insn)
+			func_for_each_insn_all(file, func, insn)
 				insn->ignore = true;
 		}
 	}
@@ -786,9 +804,8 @@ static int add_special_section_alts(struct objtool_file *file)
 	return ret;
 }
 
-static int add_switch_table(struct objtool_file *file, struct symbol *func,
-			    struct instruction *insn, struct rela *table,
-			    struct rela *next_table)
+static int add_switch_table(struct objtool_file *file, struct instruction *insn,
+			    struct rela *table, struct rela *next_table)
 {
 	struct rela *rela = table;
 	struct instruction *alt_insn;
@@ -798,18 +815,13 @@ static int add_switch_table(struct objtool_file *file, struct symbol *func,
 		if (rela == next_table)
 			break;
 
-		if (rela->sym->sec != insn->sec ||
-		    rela->addend <= func->offset ||
-		    rela->addend >= func->offset + func->len)
+		alt_insn = find_insn(file, rela->sym->sec, rela->addend);
+		if (!alt_insn)
 			break;
 
-		alt_insn = find_insn(file, insn->sec, rela->addend);
-		if (!alt_insn) {
-			WARN("%s: can't find instruction at %s+0x%x",
-			     file->rodata->rela->name, insn->sec->name,
-			     rela->addend);
-			return -1;
-		}
+		/* Make sure the jmp dest is in the function or subfunction: */
+		if (alt_insn->func->pfunc != insn->func->pfunc)
+			break;
 
 		alt = malloc(sizeof(*alt));
 		if (!alt) {
@@ -947,7 +959,7 @@ static int add_func_switch_tables(struct objtool_file *file,
 	struct rela *rela, *prev_rela = NULL;
 	int ret;
 
-	func_for_each_insn(file, func, insn) {
+	func_for_each_insn_all(file, func, insn) {
 		if (!last)
 			last = insn;
 
@@ -978,8 +990,7 @@ static int add_func_switch_tables(struct objtool_file *file,
 		 * the beginning of another switch table in the same function.
 		 */
 		if (prev_jump) {
-			ret = add_switch_table(file, func, prev_jump, prev_rela,
-					       rela);
+			ret = add_switch_table(file, prev_jump, prev_rela, rela);
 			if (ret)
 				return ret;
 		}
@@ -989,7 +1000,7 @@ static int add_func_switch_tables(struct objtool_file *file,
 	}
 
 	if (prev_jump) {
-		ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
+		ret = add_switch_table(file, prev_jump, prev_rela, NULL);
 		if (ret)
 			return ret;
 	}
@@ -1753,15 +1764,13 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
 	while (1) {
 		next_insn = next_insn_same_sec(file, insn);
 
-
-		if (file->c_file && func && insn->func && func != insn->func) {
+		if (file->c_file && func && insn->func && func != insn->func->pfunc) {
 			WARN("%s() falls through to next function %s()",
 			     func->name, insn->func->name);
 			return 1;
 		}
 
-		if (insn->func)
-			func = insn->func;
+		func = insn->func ? insn->func->pfunc : NULL;
 
 		if (func && insn->ignore) {
 			WARN_FUNC("BUG: why am I validating an ignored function?",
@@ -1782,7 +1791,7 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
 
 				i = insn;
 				save_insn = NULL;
-				func_for_each_insn_continue_reverse(file, func, i) {
+				func_for_each_insn_continue_reverse(file, insn->func, i) {
 					if (i->save) {
 						save_insn = i;
 						break;
@@ -1869,7 +1878,7 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
 		case INSN_JUMP_UNCONDITIONAL:
 			if (insn->jump_dest &&
 			    (!func || !insn->jump_dest->func ||
-			     func == insn->jump_dest->func)) {
+			     insn->jump_dest->func->pfunc == func)) {
 				ret = validate_branch(file, insn->jump_dest,
 						      state);
 				if (ret)
@@ -2064,7 +2073,7 @@ static int validate_functions(struct objtool_file *file)
 
 	for_each_sec(file, sec) {
 		list_for_each_entry(func, &sec->symbol_list, list) {
-			if (func->type != STT_FUNC)
+			if (func->type != STT_FUNC || func->pfunc != func)
 				continue;
 
 			insn = find_insn(file, sec, func->offset);
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index c1c338661699..4e60e105583e 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -79,6 +79,19 @@ struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
 	return NULL;
 }
 
+struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
+{
+	struct section *sec;
+	struct symbol *sym;
+
+	list_for_each_entry(sec, &elf->sections, list)
+		list_for_each_entry(sym, &sec->symbol_list, list)
+			if (!strcmp(sym->name, name))
+				return sym;
+
+	return NULL;
+}
+
 struct symbol *find_symbol_containing(struct section *sec, unsigned long offset)
 {
 	struct symbol *sym;
@@ -203,10 +216,11 @@ static int read_sections(struct elf *elf)
 
 static int read_symbols(struct elf *elf)
 {
-	struct section *symtab;
-	struct symbol *sym;
+	struct section *symtab, *sec;
+	struct symbol *sym, *pfunc;
 	struct list_head *entry, *tmp;
 	int symbols_nr, i;
+	char *coldstr;
 
 	symtab = find_section_by_name(elf, ".symtab");
 	if (!symtab) {
@@ -281,6 +295,30 @@ static int read_symbols(struct elf *elf)
 		hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
 	}
 
+	/* Create parent/child links for any cold subfunctions */
+	list_for_each_entry(sec, &elf->sections, list) {
+		list_for_each_entry(sym, &sec->symbol_list, list) {
+			if (sym->type != STT_FUNC)
+				continue;
+			sym->pfunc = sym->cfunc = sym;
+			coldstr = strstr(sym->name, ".cold.");
+			if (coldstr) {
+				coldstr[0] = '\0';
+				pfunc = find_symbol_by_name(elf, sym->name);
+				coldstr[0] = '.';
+
+				if (!pfunc) {
+					WARN("%s(): can't find parent function",
+					     sym->name);
+					goto err;
+				}
+
+				sym->pfunc = pfunc;
+				pfunc->cfunc = sym;
+			}
+		}
+	}
+
 	return 0;
 
 err:
diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index d86e2ff14466..de5cd2ddded9 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -61,6 +61,7 @@ struct symbol {
 	unsigned char bind, type;
 	unsigned long offset;
 	unsigned int len;
+	struct symbol *pfunc, *cfunc;
 };
 
 struct rela {
@@ -86,6 +87,7 @@ struct elf {
 struct elf *elf_open(const char *name, int flags);
 struct section *find_section_by_name(struct elf *elf, const char *name);
 struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
+struct symbol *find_symbol_by_name(struct elf *elf, const char *name);
 struct symbol *find_symbol_containing(struct section *sec, unsigned long offset);
 struct rela *find_rela_by_dest(struct section *sec, unsigned long offset);
 struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
-- 
2.17.0

[tip:core/urgent] objtool: Support GCC 8's cold subfunctions

[tip-bot for Josh Poimboeuf]

Commit-ID:  13810435b9a7014fb92eb715f77da488f3b65b99
Gitweb:     https://git.kernel.org/tip/13810435b9a7014fb92eb715f77da488f3b65b99
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Wed, 9 May 2018 22:39:15 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 14 May 2018 10:20:53 +0200

objtool: Support GCC 8's cold subfunctions

GCC 8 moves a lot of unlikely code out of line to "cold" subfunctions in
.text.unlikely.  Properly detect the new subfunctions and treat them as
extensions of the original functions.

This fixes a bunch of warnings like:

  kernel/cgroup/cgroup.o: warning: objtool: parse_cgroup_root_flags()+0x33: sibling call from callable instruction with modified stack frame
  kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files()+0x290: sibling call from callable instruction with modified stack frame
  kernel/cgroup/cgroup.o: warning: objtool: cgroup_apply_control_enable()+0x25b: sibling call from callable instruction with modified stack frame
  kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems()+0x325: sibling call from callable instruction with modified stack frame

Reported-and-tested-by: damian <damian.tometzki@icloud.com>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/0965e7fcfc5f31a276f0c7f298ff770c19b68706.1525923412.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/objtool/check.c | 93 ++++++++++++++++++++++++++++-----------------------
 tools/objtool/elf.c   | 42 +++++++++++++++++++++--
 tools/objtool/elf.h   |  2 ++
 3 files changed, 93 insertions(+), 44 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 264522d4e4af..14daf6a27d9f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -59,6 +59,31 @@ static struct instruction *next_insn_same_sec(struct objtool_file *file,
 	return next;
 }
 
+static struct instruction *next_insn_same_func(struct objtool_file *file,
+					       struct instruction *insn)
+{
+	struct instruction *next = list_next_entry(insn, list);
+	struct symbol *func = insn->func;
+
+	if (!func)
+		return NULL;
+
+	if (&next->list != &file->insn_list && next->func == func)
+		return next;
+
+	/* Check if we're already in the subfunction: */
+	if (func == func->cfunc)
+		return NULL;
+
+	/* Move to the subfunction: */
+	return find_insn(file, func->cfunc->sec, func->cfunc->offset);
+}
+
+#define func_for_each_insn_all(file, func, insn)			\
+	for (insn = find_insn(file, func->sec, func->offset);		\
+	     insn;							\
+	     insn = next_insn_same_func(file, insn))
+
 #define func_for_each_insn(file, func, insn)				\
 	for (insn = find_insn(file, func->sec, func->offset);		\
 	     insn && &insn->list != &file->insn_list &&			\
@@ -149,10 +174,14 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 			if (!strcmp(func->name, global_noreturns[i]))
 				return 1;
 
-	if (!func->sec)
+	if (!func->len)
 		return 0;
 
-	func_for_each_insn(file, func, insn) {
+	insn = find_insn(file, func->sec, func->offset);
+	if (!insn->func)
+		return 0;
+
+	func_for_each_insn_all(file, func, insn) {
 		empty = false;
 
 		if (insn->type == INSN_RETURN)
@@ -167,28 +196,17 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 	 * case, the function's dead-end status depends on whether the target
 	 * of the sibling call returns.
 	 */
-	func_for_each_insn(file, func, insn) {
-		if (insn->sec != func->sec ||
-		    insn->offset >= func->offset + func->len)
-			break;
-
+	func_for_each_insn_all(file, func, insn) {
 		if (insn->type == INSN_JUMP_UNCONDITIONAL) {
 			struct instruction *dest = insn->jump_dest;
-			struct symbol *dest_func;
 
 			if (!dest)
 				/* sibling call to another file */
 				return 0;
 
-			if (dest->sec != func->sec ||
-			    dest->offset < func->offset ||
-			    dest->offset >= func->offset + func->len) {
-				/* local sibling call */
-				dest_func = find_symbol_by_offset(dest->sec,
-								  dest->offset);
-				if (!dest_func)
-					continue;
+			if (dest->func && dest->func->pfunc != insn->func->pfunc) {
 
+				/* local sibling call */
 				if (recursion == 5) {
 					/*
 					 * Infinite recursion: two functions
@@ -199,7 +217,7 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 					return 0;
 				}
 
-				return __dead_end_function(file, dest_func,
+				return __dead_end_function(file, dest->func,
 							   recursion + 1);
 			}
 		}
@@ -426,7 +444,7 @@ static void add_ignores(struct objtool_file *file)
 			if (!ignore_func(file, func))
 				continue;
 
-			func_for_each_insn(file, func, insn)
+			func_for_each_insn_all(file, func, insn)
 				insn->ignore = true;
 		}
 	}
@@ -786,9 +804,8 @@ out:
 	return ret;
 }
 
-static int add_switch_table(struct objtool_file *file, struct symbol *func,
-			    struct instruction *insn, struct rela *table,
-			    struct rela *next_table)
+static int add_switch_table(struct objtool_file *file, struct instruction *insn,
+			    struct rela *table, struct rela *next_table)
 {
 	struct rela *rela = table;
 	struct instruction *alt_insn;
@@ -798,18 +815,13 @@ static int add_switch_table(struct objtool_file *file, struct symbol *func,
 		if (rela == next_table)
 			break;
 
-		if (rela->sym->sec != insn->sec ||
-		    rela->addend <= func->offset ||
-		    rela->addend >= func->offset + func->len)
+		alt_insn = find_insn(file, rela->sym->sec, rela->addend);
+		if (!alt_insn)
 			break;
 
-		alt_insn = find_insn(file, insn->sec, rela->addend);
-		if (!alt_insn) {
-			WARN("%s: can't find instruction at %s+0x%x",
-			     file->rodata->rela->name, insn->sec->name,
-			     rela->addend);
-			return -1;
-		}
+		/* Make sure the jmp dest is in the function or subfunction: */
+		if (alt_insn->func->pfunc != insn->func->pfunc)
+			break;
 
 		alt = malloc(sizeof(*alt));
 		if (!alt) {
@@ -947,7 +959,7 @@ static int add_func_switch_tables(struct objtool_file *file,
 	struct rela *rela, *prev_rela = NULL;
 	int ret;
 
-	func_for_each_insn(file, func, insn) {
+	func_for_each_insn_all(file, func, insn) {
 		if (!last)
 			last = insn;
 
@@ -978,8 +990,7 @@ static int add_func_switch_tables(struct objtool_file *file,
 		 * the beginning of another switch table in the same function.
 		 */
 		if (prev_jump) {
-			ret = add_switch_table(file, func, prev_jump, prev_rela,
-					       rela);
+			ret = add_switch_table(file, prev_jump, prev_rela, rela);
 			if (ret)
 				return ret;
 		}
@@ -989,7 +1000,7 @@ static int add_func_switch_tables(struct objtool_file *file,
 	}
 
 	if (prev_jump) {
-		ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
+		ret = add_switch_table(file, prev_jump, prev_rela, NULL);
 		if (ret)
 			return ret;
 	}
@@ -1753,15 +1764,13 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
 	while (1) {
 		next_insn = next_insn_same_sec(file, insn);
 
-
-		if (file->c_file && func && insn->func && func != insn->func) {
+		if (file->c_file && func && insn->func && func != insn->func->pfunc) {
 			WARN("%s() falls through to next function %s()",
 			     func->name, insn->func->name);
 			return 1;
 		}
 
-		if (insn->func)
-			func = insn->func;
+		func = insn->func ? insn->func->pfunc : NULL;
 
 		if (func && insn->ignore) {
 			WARN_FUNC("BUG: why am I validating an ignored function?",
@@ -1782,7 +1791,7 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
 
 				i = insn;
 				save_insn = NULL;
-				func_for_each_insn_continue_reverse(file, func, i) {
+				func_for_each_insn_continue_reverse(file, insn->func, i) {
 					if (i->save) {
 						save_insn = i;
 						break;
@@ -1869,7 +1878,7 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
 		case INSN_JUMP_UNCONDITIONAL:
 			if (insn->jump_dest &&
 			    (!func || !insn->jump_dest->func ||
-			     func == insn->jump_dest->func)) {
+			     insn->jump_dest->func->pfunc == func)) {
 				ret = validate_branch(file, insn->jump_dest,
 						      state);
 				if (ret)
@@ -2064,7 +2073,7 @@ static int validate_functions(struct objtool_file *file)
 
 	for_each_sec(file, sec) {
 		list_for_each_entry(func, &sec->symbol_list, list) {
-			if (func->type != STT_FUNC)
+			if (func->type != STT_FUNC || func->pfunc != func)
 				continue;
 
 			insn = find_insn(file, sec, func->offset);
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index c1c338661699..4e60e105583e 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -79,6 +79,19 @@ struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
 	return NULL;
 }
 
+struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
+{
+	struct section *sec;
+	struct symbol *sym;
+
+	list_for_each_entry(sec, &elf->sections, list)
+		list_for_each_entry(sym, &sec->symbol_list, list)
+			if (!strcmp(sym->name, name))
+				return sym;
+
+	return NULL;
+}
+
 struct symbol *find_symbol_containing(struct section *sec, unsigned long offset)
 {
 	struct symbol *sym;
@@ -203,10 +216,11 @@ static int read_sections(struct elf *elf)
 
 static int read_symbols(struct elf *elf)
 {
-	struct section *symtab;
-	struct symbol *sym;
+	struct section *symtab, *sec;
+	struct symbol *sym, *pfunc;
 	struct list_head *entry, *tmp;
 	int symbols_nr, i;
+	char *coldstr;
 
 	symtab = find_section_by_name(elf, ".symtab");
 	if (!symtab) {
@@ -281,6 +295,30 @@ static int read_symbols(struct elf *elf)
 		hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
 	}
 
+	/* Create parent/child links for any cold subfunctions */
+	list_for_each_entry(sec, &elf->sections, list) {
+		list_for_each_entry(sym, &sec->symbol_list, list) {
+			if (sym->type != STT_FUNC)
+				continue;
+			sym->pfunc = sym->cfunc = sym;
+			coldstr = strstr(sym->name, ".cold.");
+			if (coldstr) {
+				coldstr[0] = '\0';
+				pfunc = find_symbol_by_name(elf, sym->name);
+				coldstr[0] = '.';
+
+				if (!pfunc) {
+					WARN("%s(): can't find parent function",
+					     sym->name);
+					goto err;
+				}
+
+				sym->pfunc = pfunc;
+				pfunc->cfunc = sym;
+			}
+		}
+	}
+
 	return 0;
 
 err:
diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index d86e2ff14466..de5cd2ddded9 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -61,6 +61,7 @@ struct symbol {
 	unsigned char bind, type;
 	unsigned long offset;
 	unsigned int len;
+	struct symbol *pfunc, *cfunc;
 };
 
 struct rela {
@@ -86,6 +87,7 @@ struct elf {
 struct elf *elf_open(const char *name, int flags);
 struct section *find_section_by_name(struct elf *elf, const char *name);
 struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
+struct symbol *find_symbol_by_name(struct elf *elf, const char *name);
 struct symbol *find_symbol_containing(struct section *sec, unsigned long offset);
 struct rela *find_rela_by_dest(struct section *sec, unsigned long offset);
 struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,

[PATCH 3/3] objtool: Support GCC 8 switch tables

[Josh Poimboeuf]

Add some additional checks to the switch jump table logic.  This fixes
the following warnings with GCC 8:

  drivers/block/virtio_blk.o: warning: objtool: virtio_queue_rq()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+72
  net/ipv6/icmp.o: warning: objtool: icmpv6_rcv()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64
  drivers/usb/core/quirks.o: warning: objtool: quirks_param_set()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+48
  drivers/mtd/nand/raw/nand_hynix.o: warning: objtool: hynix_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+24
  drivers/mtd/nand/raw/nand_samsung.o: warning: objtool: samsung_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+32
  drivers/gpu/drm/nouveau/nvkm/subdev/top/gk104.o: warning: objtool: gk104_top_oneinit()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64

Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 tools/objtool/check.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 14daf6a27d9f..6b6885e1e431 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -810,17 +810,28 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 	struct rela *rela = table;
 	struct instruction *alt_insn;
 	struct alternative *alt;
+	struct symbol *pfunc = insn->func->pfunc;
+	unsigned int prev_offset = 0;
 
 	list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
 		if (rela == next_table)
 			break;
 
+		/* Make sure the switch table entries are consecutive: */
+		if (prev_offset && rela->offset != prev_offset + sizeof(long))
+			break;
+
+		/* Detect function pointers from contiguous objects: */
+		if (rela->sym->sec == pfunc->sec &&
+		    rela->addend == pfunc->offset)
+			break;
+
 		alt_insn = find_insn(file, rela->sym->sec, rela->addend);
 		if (!alt_insn)
 			break;
 
 		/* Make sure the jmp dest is in the function or subfunction: */
-		if (alt_insn->func->pfunc != insn->func->pfunc)
+		if (alt_insn->func->pfunc != pfunc)
 			break;
 
 		alt = malloc(sizeof(*alt));
@@ -831,6 +842,13 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 
 		alt->insn = alt_insn;
 		list_add_tail(&alt->list, &insn->alts);
+		prev_offset = rela->offset;
+	}
+
+	if (!prev_offset) {
+		WARN_FUNC("can't find switch jump table",
+			  insn->sec, insn->offset);
+		return -1;
 	}
 
 	return 0;
@@ -887,7 +905,9 @@ static struct rela *find_switch_table(struct objtool_file *file,
 	struct instruction *orig_insn = insn;
 
 	text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
-	if (text_rela && text_rela->sym == file->rodata->sym) {
+	if (text_rela && text_rela->sym == file->rodata->sym &&
+	    !find_symbol_containing(file->rodata, text_rela->addend)) {
+
 		/* case 1 */
 		rodata_rela = find_rela_by_dest(file->rodata,
 						text_rela->addend);
-- 
2.17.0

Re: [PATCH 3/3] objtool: Support GCC 8 switch tables

[Peter Zijlstra]

On Wed, May 09, 2018 at 10:39:16PM -0500, Josh Poimboeuf wrote:
> Add some additional checks to the switch jump table logic.  This fixes
> the following warnings with GCC 8:
> 
>   drivers/block/virtio_blk.o: warning: objtool: virtio_queue_rq()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+72
>   net/ipv6/icmp.o: warning: objtool: icmpv6_rcv()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64
>   drivers/usb/core/quirks.o: warning: objtool: quirks_param_set()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+48
>   drivers/mtd/nand/raw/nand_hynix.o: warning: objtool: hynix_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+24
>   drivers/mtd/nand/raw/nand_samsung.o: warning: objtool: samsung_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+32
>   drivers/gpu/drm/nouveau/nvkm/subdev/top/gk104.o: warning: objtool: gk104_top_oneinit()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64

Could you maybe detail how the GCC8 switch tables are different? And
thus what needed fixing?

[PATCH v1.1 3/3] objtool: Support GCC 8 switch tables

[Josh Poimboeuf]

On Thu, May 10, 2018 at 10:41:25AM +0200, Peter Zijlstra wrote:
> On Wed, May 09, 2018 at 10:39:16PM -0500, Josh Poimboeuf wrote:
> > Add some additional checks to the switch jump table logic.  This fixes
> > the following warnings with GCC 8:
> > 
> >   drivers/block/virtio_blk.o: warning: objtool: virtio_queue_rq()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+72
> >   net/ipv6/icmp.o: warning: objtool: icmpv6_rcv()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64
> >   drivers/usb/core/quirks.o: warning: objtool: quirks_param_set()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+48
> >   drivers/mtd/nand/raw/nand_hynix.o: warning: objtool: hynix_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+24
> >   drivers/mtd/nand/raw/nand_samsung.o: warning: objtool: samsung_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+32
> >   drivers/gpu/drm/nouveau/nvkm/subdev/top/gk104.o: warning: objtool: gk104_top_oneinit()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64
> 
> Could you maybe detail how the GCC8 switch tables are different? And
> thus what needed fixing?

Good point, how about this?

----

From: Josh Poimboeuf <jpoimboe@redhat.com>
Subject: [PATCH v1.1 3/3] objtool: Support GCC 8 switch tables

With GCC 8, some issues were found with the objtool switch table
detection.

1) In the .rodata section, immediately after the switch table, there can
   be another object which contains a pointer to the function which had
   the switch statement.  In this case objtool wrongly considers the
   function pointer to be part of the switch table.  Fix it by:

   a) making sure there are no pointers to the beginning of the
      function; and

   b) making sure there are no gaps in the switch table.

   Only the former was needed, the latter adds additional protection for
   future optimizations.

2) In find_switch_table(), case 1 and case 2 are missing the check to
   ensure that the .rodata switch table data is anonymous, i.e. that it
   isn't already associated with an ELF symbol.  Fix it by adding the
   same find_symbol_containing() check which is used for case 3.

This fixes the following warnings with GCC 8:

  drivers/block/virtio_blk.o: warning: objtool: virtio_queue_rq()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+72
  net/ipv6/icmp.o: warning: objtool: icmpv6_rcv()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64
  drivers/usb/core/quirks.o: warning: objtool: quirks_param_set()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+48
  drivers/mtd/nand/raw/nand_hynix.o: warning: objtool: hynix_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+24
  drivers/mtd/nand/raw/nand_samsung.o: warning: objtool: samsung_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+32
  drivers/gpu/drm/nouveau/nvkm/subdev/top/gk104.o: warning: objtool: gk104_top_oneinit()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64

Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 tools/objtool/check.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 14daf6a27d9f..6b6885e1e431 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -810,17 +810,28 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 	struct rela *rela = table;
 	struct instruction *alt_insn;
 	struct alternative *alt;
+	struct symbol *pfunc = insn->func->pfunc;
+	unsigned int prev_offset = 0;
 
 	list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
 		if (rela == next_table)
 			break;
 
+		/* Make sure the switch table entries are consecutive: */
+		if (prev_offset && rela->offset != prev_offset + sizeof(long))
+			break;
+
+		/* Detect function pointers from contiguous objects: */
+		if (rela->sym->sec == pfunc->sec &&
+		    rela->addend == pfunc->offset)
+			break;
+
 		alt_insn = find_insn(file, rela->sym->sec, rela->addend);
 		if (!alt_insn)
 			break;
 
 		/* Make sure the jmp dest is in the function or subfunction: */
-		if (alt_insn->func->pfunc != insn->func->pfunc)
+		if (alt_insn->func->pfunc != pfunc)
 			break;
 
 		alt = malloc(sizeof(*alt));
@@ -831,6 +842,13 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 
 		alt->insn = alt_insn;
 		list_add_tail(&alt->list, &insn->alts);
+		prev_offset = rela->offset;
+	}
+
+	if (!prev_offset) {
+		WARN_FUNC("can't find switch jump table",
+			  insn->sec, insn->offset);
+		return -1;
 	}
 
 	return 0;
@@ -887,7 +905,9 @@ static struct rela *find_switch_table(struct objtool_file *file,
 	struct instruction *orig_insn = insn;
 
 	text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
-	if (text_rela && text_rela->sym == file->rodata->sym) {
+	if (text_rela && text_rela->sym == file->rodata->sym &&
+	    !find_symbol_containing(file->rodata, text_rela->addend)) {
+
 		/* case 1 */
 		rodata_rela = find_rela_by_dest(file->rodata,
 						text_rela->addend);
-- 
2.17.0

Re: [PATCH v1.1 3/3] objtool: Support GCC 8 switch tables

[Peter Zijlstra]

On Thu, May 10, 2018 at 07:44:24AM -0500, Josh Poimboeuf wrote:
> On Thu, May 10, 2018 at 10:41:25AM +0200, Peter Zijlstra wrote:

> > Could you maybe detail how the GCC8 switch tables are different? And
> > thus what needed fixing?
> 
> Good point, how about this?

Thanks!

For the series:

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

[PATCH v1.2 3/3] objtool: Support GCC 8 switch tables

[Josh Poimboeuf]

Add some additional checks to the switch jump table logic.  This fixes
the following warnings with GCC 8:

  drivers/block/virtio_blk.o: warning: objtool: virtio_queue_rq()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+72
  net/ipv6/icmp.o: warning: objtool: icmpv6_rcv()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64
  drivers/usb/core/quirks.o: warning: objtool: quirks_param_set()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+48
  drivers/mtd/nand/raw/nand_hynix.o: warning: objtool: hynix_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+24
  drivers/mtd/nand/raw/nand_samsung.o: warning: objtool: samsung_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+32
  drivers/gpu/drm/nouveau/nvkm/subdev/top/gk104.o: warning: objtool: gk104_top_oneinit()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64

Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
v1.2: replaced 'sizeof(long)' with '8' to fix cross-compilation of the
      64-bit target on a 32-bit host

 tools/objtool/check.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 14daf6a27d9f..9bb04fddd3c8 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -810,17 +810,28 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 	struct rela *rela = table;
 	struct instruction *alt_insn;
 	struct alternative *alt;
+	struct symbol *pfunc = insn->func->pfunc;
+	unsigned int prev_offset = 0;
 
 	list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
 		if (rela == next_table)
 			break;
 
+		/* Make sure the switch table entries are consecutive: */
+		if (prev_offset && rela->offset != prev_offset + 8)
+			break;
+
+		/* Detect function pointers from contiguous objects: */
+		if (rela->sym->sec == pfunc->sec &&
+		    rela->addend == pfunc->offset)
+			break;
+
 		alt_insn = find_insn(file, rela->sym->sec, rela->addend);
 		if (!alt_insn)
 			break;
 
 		/* Make sure the jmp dest is in the function or subfunction: */
-		if (alt_insn->func->pfunc != insn->func->pfunc)
+		if (alt_insn->func->pfunc != pfunc)
 			break;
 
 		alt = malloc(sizeof(*alt));
@@ -831,6 +842,13 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 
 		alt->insn = alt_insn;
 		list_add_tail(&alt->list, &insn->alts);
+		prev_offset = rela->offset;
+	}
+
+	if (!prev_offset) {
+		WARN_FUNC("can't find switch jump table",
+			  insn->sec, insn->offset);
+		return -1;
 	}
 
 	return 0;
@@ -887,7 +905,9 @@ static struct rela *find_switch_table(struct objtool_file *file,
 	struct instruction *orig_insn = insn;
 
 	text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
-	if (text_rela && text_rela->sym == file->rodata->sym) {
+	if (text_rela && text_rela->sym == file->rodata->sym &&
+	    !find_symbol_containing(file->rodata, text_rela->addend)) {
+
 		/* case 1 */
 		rodata_rela = find_rela_by_dest(file->rodata,
 						text_rela->addend);
-- 
2.17.0

[PATCH v1.3 3/3] objtool: Support GCC 8 switch tables

[Josh Poimboeuf]

With GCC 8, some issues were found with the objtool switch table
detection.

1) In the .rodata section, immediately after the switch table, there can
   be another object which contains a pointer to the function which had
   the switch statement.  In this case objtool wrongly considers the
   function pointer to be part of the switch table.  Fix it by:

   a) making sure there are no pointers to the beginning of the
      function; and

   b) making sure there are no gaps in the switch table.

   Only the former was needed, the latter adds additional protection for
   future optimizations.

2) In find_switch_table(), case 1 and case 2 are missing the check to
   ensure that the .rodata switch table data is anonymous, i.e. that it
   isn't already associated with an ELF symbol.  Fix it by adding the
   same find_symbol_containing() check which is used for case 3.

This fixes the following warnings with GCC 8:

  drivers/block/virtio_blk.o: warning: objtool: virtio_queue_rq()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+72
  net/ipv6/icmp.o: warning: objtool: icmpv6_rcv()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64
  drivers/usb/core/quirks.o: warning: objtool: quirks_param_set()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+48
  drivers/mtd/nand/raw/nand_hynix.o: warning: objtool: hynix_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+24
  drivers/mtd/nand/raw/nand_samsung.o: warning: objtool: samsung_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+32
  drivers/gpu/drm/nouveau/nvkm/subdev/top/gk104.o: warning: objtool: gk104_top_oneinit()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64

Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
v1.3: Combine improved patch description from 1.1 with 32-bit host
      cross-compile from 1.2.

 tools/objtool/check.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 14daf6a27d9f..9bb04fddd3c8 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -810,17 +810,28 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 	struct rela *rela = table;
 	struct instruction *alt_insn;
 	struct alternative *alt;
+	struct symbol *pfunc = insn->func->pfunc;
+	unsigned int prev_offset = 0;
 
 	list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
 		if (rela == next_table)
 			break;
 
+		/* Make sure the switch table entries are consecutive: */
+		if (prev_offset && rela->offset != prev_offset + 8)
+			break;
+
+		/* Detect function pointers from contiguous objects: */
+		if (rela->sym->sec == pfunc->sec &&
+		    rela->addend == pfunc->offset)
+			break;
+
 		alt_insn = find_insn(file, rela->sym->sec, rela->addend);
 		if (!alt_insn)
 			break;
 
 		/* Make sure the jmp dest is in the function or subfunction: */
-		if (alt_insn->func->pfunc != insn->func->pfunc)
+		if (alt_insn->func->pfunc != pfunc)
 			break;
 
 		alt = malloc(sizeof(*alt));
@@ -831,6 +842,13 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 
 		alt->insn = alt_insn;
 		list_add_tail(&alt->list, &insn->alts);
+		prev_offset = rela->offset;
+	}
+
+	if (!prev_offset) {
+		WARN_FUNC("can't find switch jump table",
+			  insn->sec, insn->offset);
+		return -1;
 	}
 
 	return 0;
@@ -887,7 +905,9 @@ static struct rela *find_switch_table(struct objtool_file *file,
 	struct instruction *orig_insn = insn;
 
 	text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
-	if (text_rela && text_rela->sym == file->rodata->sym) {
+	if (text_rela && text_rela->sym == file->rodata->sym &&
+	    !find_symbol_containing(file->rodata, text_rela->addend)) {
+
 		/* case 1 */
 		rodata_rela = find_rela_by_dest(file->rodata,
 						text_rela->addend);
-- 
2.17.0

[tip:core/urgent] objtool: Support GCC 8 switch tables

[tip-bot for Josh Poimboeuf]

Commit-ID:  fd35c88b74170d9335530d9abf271d5d73eb5401
Gitweb:     https://git.kernel.org/tip/fd35c88b74170d9335530d9abf271d5d73eb5401
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Thu, 10 May 2018 17:48:49 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 14 May 2018 10:20:54 +0200

objtool: Support GCC 8 switch tables

With GCC 8, some issues were found with the objtool switch table
detection.

1) In the .rodata section, immediately after the switch table, there can
   be another object which contains a pointer to the function which had
   the switch statement.  In this case objtool wrongly considers the
   function pointer to be part of the switch table.  Fix it by:

   a) making sure there are no pointers to the beginning of the
      function; and

   b) making sure there are no gaps in the switch table.

   Only the former was needed, the latter adds additional protection for
   future optimizations.

2) In find_switch_table(), case 1 and case 2 are missing the check to
   ensure that the .rodata switch table data is anonymous, i.e. that it
   isn't already associated with an ELF symbol.  Fix it by adding the
   same find_symbol_containing() check which is used for case 3.

This fixes the following warnings with GCC 8:

  drivers/block/virtio_blk.o: warning: objtool: virtio_queue_rq()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+72
  net/ipv6/icmp.o: warning: objtool: icmpv6_rcv()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64
  drivers/usb/core/quirks.o: warning: objtool: quirks_param_set()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+48
  drivers/mtd/nand/raw/nand_hynix.o: warning: objtool: hynix_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+24
  drivers/mtd/nand/raw/nand_samsung.o: warning: objtool: samsung_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+32
  drivers/gpu/drm/nouveau/nvkm/subdev/top/gk104.o: warning: objtool: gk104_top_oneinit()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64

Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: damian <damian.tometzki@icloud.com>
Link: http://lkml.kernel.org/r/20180510224849.xwi34d6tzheb5wgw@treble
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/objtool/check.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 14daf6a27d9f..9bb04fddd3c8 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -810,17 +810,28 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 	struct rela *rela = table;
 	struct instruction *alt_insn;
 	struct alternative *alt;
+	struct symbol *pfunc = insn->func->pfunc;
+	unsigned int prev_offset = 0;
 
 	list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
 		if (rela == next_table)
 			break;
 
+		/* Make sure the switch table entries are consecutive: */
+		if (prev_offset && rela->offset != prev_offset + 8)
+			break;
+
+		/* Detect function pointers from contiguous objects: */
+		if (rela->sym->sec == pfunc->sec &&
+		    rela->addend == pfunc->offset)
+			break;
+
 		alt_insn = find_insn(file, rela->sym->sec, rela->addend);
 		if (!alt_insn)
 			break;
 
 		/* Make sure the jmp dest is in the function or subfunction: */
-		if (alt_insn->func->pfunc != insn->func->pfunc)
+		if (alt_insn->func->pfunc != pfunc)
 			break;
 
 		alt = malloc(sizeof(*alt));
@@ -831,6 +842,13 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 
 		alt->insn = alt_insn;
 		list_add_tail(&alt->list, &insn->alts);
+		prev_offset = rela->offset;
+	}
+
+	if (!prev_offset) {
+		WARN_FUNC("can't find switch jump table",
+			  insn->sec, insn->offset);
+		return -1;
 	}
 
 	return 0;
@@ -887,7 +905,9 @@ static struct rela *find_switch_table(struct objtool_file *file,
 	struct instruction *orig_insn = insn;
 
 	text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
-	if (text_rela && text_rela->sym == file->rodata->sym) {
+	if (text_rela && text_rela->sym == file->rodata->sym &&
+	    !find_symbol_containing(file->rodata, text_rela->addend)) {
+
 		/* case 1 */
 		rodata_rela = find_rela_by_dest(file->rodata,
 						text_rela->addend);