4.9-stable review patch. If anyone has any objections, please let me know.
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From: Josh Poimboeuf jpoimboe@redhat.com
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: 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... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- tools/objtool/check.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
--- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -207,9 +207,13 @@ static int __dead_end_function(struct ob
/* 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,