From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B1D06C43381 for ; Thu, 7 Mar 2019 09:02:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8362E20675 for ; Thu, 7 Mar 2019 09:02:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726203AbfCGJCA (ORCPT ); Thu, 7 Mar 2019 04:02:00 -0500 Received: from mout.kundenserver.de ([212.227.126.135]:41079 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726102AbfCGJCA (ORCPT ); Thu, 7 Mar 2019 04:02:00 -0500 Received: from wuerfel.lan ([109.192.41.194]) by mrelayeu.kundenserver.de (mreue011 [212.227.15.129]) with ESMTPA (Nemesis) id 1MDhQt-1hCZjv0PiR-00Akoh; Thu, 07 Mar 2019 10:01:48 +0100 From: Arnd Bergmann To: linux-fsdevel@vger.kernel.org Cc: Nick Desaulniers , Alexander Viro , Andrew Morton , Andi Kleen , Christoph Hellwig , Eric Dumazet , Arnd Bergmann , "Darrick J. Wong" , Greg Kroah-Hartman , linux-kernel@vger.kernel.org Subject: [PATCH] fs/select: avoid clang stack usage warning Date: Thu, 7 Mar 2019 10:01:36 +0100 Message-Id: <20190307090146.1874906-1-arnd@arndb.de> X-Mailer: git-send-email 2.20.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Provags-ID: V03:K1:fHbTah3fz7WH6MIb/uyJkiMRtUkJq94xINrPv3mqYq0WpEmPXA6 57c4lGYafQ6Z29pxGltyEkAkHd2lzkRWUUs5AxaCpVb16diE/ppftcd5Xlqi1G+YN72yUBz L4VQNr/dUcvOb04V4ZEHSVLcx4BCP9KVk2kHU+ayVn+nDvvjQ+zDXFjgV5uWbP2F1coNQD1 lSP/D7BtDpsqxgIb+BqgQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:kzJk6NlwIrQ=:nIfv0Nj1msgRnH5vMlj8MG DPXm7o7HIAWLEQarTsssNudmTdjappWe6On0qJPjZuXN+4TSgPbzbmidbKKafvFCNaos0iICx naJCHKUkYmbeleSsZ6terzMciYiuOzWTFWGKQP8PDiAfnqDgQViV2DVlB/d2y3sT9F+VPWHix IbtvHTMzUvgnRJLeVnQPXJRpepxQQyQPaI8iZx+o0KjkRq/IFr2KbkqFN0yGIAfNBOh/owgW9 2vHt5afPNoPnkQRrQzaYBPS69bzrhHFZ8FNKgDyCndM4WvkAdDxziU6xKjR4VRbxrOdpV3qMc o8nFEep2cRlJeg5C+/+vXS1cPC6Ao5+/UKDkn+pTlfBmtVu8RkWi++SJC98wx9wvuzdXhDEVR PEqDtm9vUwtIc8BsW1biSpO8xBZ57hlQVQGw/T2tYj4VeGSoAbdBdpKx7qrFZKNz1VrJa6Qxm HdY4hCSEFd0OKW62FuPj3wJ6gXPzMIAz9VPvMVG9jSU7ZtboxS7t1LYWhFzl8K18fFSrk2+0u Lc1aFgLHeGM91orEo+w20Rkd4Iiii4cTDoD1wk+KWJjFHvwiVMFiss8uWBBcgLRgUC+HlN8Ji xZMTw+GkFo17Xhb1I/OJvQaIPk/iGqJNcMyrdMHXxwmHCIvTUQdF+WdHO0nd3iLfTCmZNIp9c IclhxM7+luawbQH+6SDPbwB+NJoynY0DJEaDk+CXexUYODqYA/MwMOHNuGEuFIOWhHYtgXjz2 tqdwh1f1NgCemIysG1Ss5hH3oSAUpoF7WSf6uQ== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The select() implementation is carefully tuned to put a sensible amount of data on the stack for holding a copy of the user space fd_set, but not too large to risk overflowing the kernel stack. When building a 32-bit kernel with clang, we need a little more space than with gcc, which often triggers a warning: fs/select.c:619:5: error: stack frame size of 1048 bytes in function 'core_sys_select' [-Werror,-Wframe-larger-than=] int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, I experimentally found that for 32-bit ARM, reducing the maximum stack usage by 64 bytes keeps us reliably under the warning limit again. Signed-off-by: Arnd Bergmann --- include/linux/poll.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/include/linux/poll.h b/include/linux/poll.h index 7e0fdcf905d2..1cdc32b1f1b0 100644 --- a/include/linux/poll.h +++ b/include/linux/poll.h @@ -16,7 +16,11 @@ extern struct ctl_table epoll_table[]; /* for sysctl */ /* ~832 bytes of stack space used max in sys_select/sys_poll before allocating additional memory. */ +#ifdef __clang__ +#define MAX_STACK_ALLOC 768 +#else #define MAX_STACK_ALLOC 832 +#endif #define FRONTEND_STACK_ALLOC 256 #define SELECT_STACK_ALLOC FRONTEND_STACK_ALLOC #define POLL_STACK_ALLOC FRONTEND_STACK_ALLOC -- 2.20.0