Commit 0afd0d9e authored May 09, 2018 by Josh Poimboeuf Committed by Ingo Molnar May 14, 2018

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>

parent 4fe875e4

tools/objtool/check.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -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,