Commit 9aebb3d3 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Greg Kroah-Hartman

objtool: Fix "noreturn" detection for recursive sibling calls

commit 0afd0d9e0e7879d666c1df2fa1bea4d8716909fe upstream.

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: default avatarRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: default avatarPeter 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.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 603a2cdf
......@@ -207,9 +207,13 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
/* local sibling call */
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,
......
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