linux-kernel - Re: linux-next: Tree for Oct 28 (objtool)

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Date:   Mon, 28 Oct 2019 11:02:15 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: linux-next: Tree for Oct 28 (objtool)

On Mon, Oct 28, 2019 at 08:31:28AM -0700, Randy Dunlap wrote:
> On 10/28/19 1:51 AM, Stephen Rothwell wrote:
> > Hi all,
> > 
> > Changes since 20191025:
> > 
> 
> 
> on x86_64:
> 
> kernel/exit.o: warning: objtool: __x64_sys_exit_group()+0x14: unreachable instruction
> 
> .o file is attached.

Silly GCC.  Does this fix it?

diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 4b1c3b664f51..d58587391b96 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -83,7 +83,7 @@ static inline void exit_thread(struct task_struct *tsk)
 {
 }
 #endif
-extern void do_group_exit(int);
+extern void __noreturn do_group_exit(int);
 
 extern void exit_files(struct task_struct *);
 extern void exit_itimers(struct signal_struct *);
diff --git a/kernel/exit.c b/kernel/exit.c
index f2d20ab74422..bdc4122d904d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -894,7 +894,7 @@ SYSCALL_DEFINE1(exit, int, error_code)
  * Take down every thread in the group.  This is called by fatal signals
  * as well as by sys_exit_group (below).
  */
-void
+void __noreturn
 do_group_exit(int exit_code)
 {
 	struct signal_struct *sig = current->signal;
@@ -931,7 +931,6 @@ SYSCALL_DEFINE1(exit_group, int, error_code)
 {
 	do_group_exit((error_code & 0xff) << 8);
 	/* NOTREACHED */
-	return 0;
 }
 
 struct waitid_info {
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 543c068096b1..97919469c787 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -135,6 +135,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 		"__stack_chk_fail",
 		"panic",
 		"do_exit",
+		"do_group_exit",
 		"do_task_dead",
 		"__module_put_and_exit",
 		"complete_and_exit",