From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f68.google.com ([209.85.218.68]:45745 "EHLO mail-oi0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726622AbeIKTzt (ORCPT ); Tue, 11 Sep 2018 15:55:49 -0400 From: Rob Herring To: Finn Thain , Stan Johnson , Frank Rowand , Benjamin Herrenschmidt Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, stable@vger.kernel.org Subject: [PATCH] of: fix phandle cache creation for DTs with no phandles Date: Tue, 11 Sep 2018 09:56:07 -0500 Message-Id: <20180911145607.6009-1-robh@kernel.org> Sender: stable-owner@vger.kernel.org List-ID: With commit 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of of_find_node_by_phandle()"), a G3 PowerMac fails to boot. The root cause is the DT for this system has no phandle properties when booted with BootX. of_populate_phandle_cache() does not handle the case of no phandles correctly. The problem is roundup_pow_of_two() for 0 is undefined. The implementation subtracts 1 underflowing and then things are in the weeds. Fixes: 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of of_find_node_by_phandle()") Cc: stable@vger.kernel.org # 4.17+ Reported-by: Finn Thain Tested-by: Stan Johnson Cc: Frank Rowand Cc: Benjamin Herrenschmidt Signed-off-by: Rob Herring --- Here's a formal patch of what Stan tested. Will send to Linus this week. Rob drivers/of/base.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/of/base.c b/drivers/of/base.c index a055cd1ef96d..17ae594b7014 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -140,6 +140,9 @@ void of_populate_phandle_cache(void) if (np->phandle && np->phandle != OF_PHANDLE_ILLEGAL) phandles++; + if (!phandles) + goto out; + cache_entries = roundup_pow_of_two(phandles); phandle_cache_mask = cache_entries - 1; -- 2.17.1