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=-8.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 B4D30C433E7 for ; Sun, 30 Aug 2020 02:23:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 928F720838 for ; Sun, 30 Aug 2020 02:23:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598754213; bh=dXTTvvUTH4ze8YE/wK5hp4N4rIH/LzeYfhV5j6PFUWE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=zCB4GsLfR0xeyU71m2HNm7GeaPl6GkEX1j2KlXy5LQRJy/J4RfEdCYGe956C1zv3Q 5HDRPiJG9wlEUezzu+sOGRjtOLIP5MOhU6dsDndiIVXzcjrCMuhgag+39wSv5KDapQ TTMMUKso1AiYs8J1U/SOKM71o79//FjtHQy/sLxk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728614AbgH3CXc (ORCPT ); Sat, 29 Aug 2020 22:23:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:47746 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728609AbgH3CXc (ORCPT ); Sat, 29 Aug 2020 22:23:32 -0400 Received: from localhost (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6C6E420776; Sun, 30 Aug 2020 02:23:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598754211; bh=dXTTvvUTH4ze8YE/wK5hp4N4rIH/LzeYfhV5j6PFUWE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ziuXrkGcW3IS9YeYrKruFhO2o6MBX9552VS8jGjrQajKayxIcNmHxG7RpsDx3swt9 UeDE4pKRaJPdleBPoPok81iOnHuKfyvHsGlKoLZZxcrkKphvmS7U8JUGh5c+h1Lqsa 76Wz78sMFKalEB0JU38zeyYx7B7LkFlDrLxmpFZs= Date: Sat, 29 Aug 2020 22:23:30 -0400 From: Sasha Levin To: Hauke Mehrtens Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Victor Kamensky , Bruce Ashfield , Paul Burton , linux-mips@vger.kernel.org, Ralf Baechle , James Hogan , Vincenzo Frascino , richard.purdie@linuxfoundation.org, Tony Ambardar Subject: Re: [PATCH AUTOSEL 5.4 10/58] mips: vdso: fix 'jalr t9' crash in vdso code Message-ID: <20200830022330.GY8670@sasha-vm> References: <20200305171420.29595-1-sashal@kernel.org> <20200305171420.29595-10-sashal@kernel.org> <20200829135656.GX8670@sasha-vm> <3c275203-8df8-4746-0941-c142cf72bee4@hauke-m.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3c275203-8df8-4746-0941-c142cf72bee4@hauke-m.de> Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Sat, Aug 29, 2020 at 04:37:32PM +0200, Hauke Mehrtens wrote: >On 8/29/20 3:56 PM, Sasha Levin wrote: >> On Sat, Aug 29, 2020 at 03:08:01PM +0200, Hauke Mehrtens wrote: >>> On 3/5/20 6:13 PM, Sasha Levin wrote: >>>> From: Victor Kamensky >>>> >>>> [ Upstream commit d3f703c4359ff06619b2322b91f69710453e6b6d ] >>>> >>>> Observed that when kernel is built with Yocto mips64-poky-linux-gcc, >>>> and mips64-poky-linux-gnun32-gcc toolchain, resulting vdso contains >>>> 'jalr t9' instructions in its code and since in vdso case nobody >>>> sets GOT table code crashes when instruction reached. On other hand >>>> observed that when kernel is built mips-poky-linux-gcc toolchain, the >>>> same 'jalr t9' instruction are replaced with PC relative function >>>> calls using 'bal' instructions. >>>> >>>> The difference boils down to -mrelax-pic-calls and -mexplicit-relocs >>>> gcc options that gets different default values depending on gcc >>>> target triplets and corresponding binutils. -mrelax-pic-calls got >>>> enabled by default only in mips-poky-linux-gcc case. MIPS binutils >>>> ld relies on R_MIPS_JALR relocation to convert 'jalr t9' into 'bal' >>>> and such relocation is generated only if -mrelax-pic-calls option >>>> is on. >>>> >>>> Please note 'jalr t9' conversion to 'bal' can happen only to static >>>> functions. These static PIC calls use mips local GOT entries that >>>> are supposed to be filled with start of DSO value by run-time linker >>>> (missing in VDSO case) and they do not have dynamic relocations. >>>> Global mips GOT entries must have dynamic relocations and they should >>>> be prevented by cmd_vdso_check Makefile rule. >>>> >>>> Solution call out -mrelax-pic-calls and -mexplicit-relocs options >>>> explicitly while compiling MIPS vdso code. That would get correct >>>> and consistent between different toolchains behaviour. >>>> >>>> Reported-by: Bruce Ashfield >>>> Signed-off-by: Victor Kamensky >>>> Signed-off-by: Paul Burton >>>> Cc: linux-mips@vger.kernel.org >>>> Cc: Ralf Baechle >>>> Cc: James Hogan >>>> Cc: Vincenzo Frascino >>>> Cc: richard.purdie@linuxfoundation.org >>>> Signed-off-by: Sasha Levin >>>> --- >>>>  arch/mips/vdso/Makefile | 1 + >>>>  1 file changed, 1 insertion(+) >>>> >>> >>> Hi Sasha, >>> >>> Why was this not added to the 5.4 stable branch? >>> >>> Some OpenWrt users ran into this problem with kernel 5.4 on MIPS64 [0]. >>> We backported this patch on our own in OpenWrt [1], but it should be >>> added to the sable branch in my opinion as it fixes a real problem. >>> >>> @Sasha: Can you add it to the 5.4 stable branch or should I send some >>> special email? >> >> It failed building on 5.4. If you'd like it included, please send me a >> tested backport for 5.4. >> > >I successfully compiled a kernel 5.4.61 with this patch on top with GCC >8.4 for MIPS 64 big and little Endian. > >What was broken in your compile test? See https://lore.kernel.org/stable/bfdce3ef-5fe9-8dab-1695-be3d33727529@roeck-us.net/ -- Thanks, Sasha