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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 1A895C3F2D7 for ; Thu, 5 Mar 2020 17:24:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E9D25207FD for ; Thu, 5 Mar 2020 17:24:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583429052; bh=kJdYtdkXoUJqBCbsGNBYogiLr8GIFp4ngkilDarlmMY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=rqikmV0QQcDppSvCp8pySZ2XjswgHnTpxNrt1BqBMPKtSHsxR3oWfSIfedCrIwGgl OM0QhsFwPGJVkwrGyAveCfQiXUU6pN513nZVXnhIWaIsfo9OLvlXvYJfRGdqFxgg9m OPE9WnY9rpfmUa4O06zYbhOjZE16Je9waVS2yvEI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727883AbgCERYK (ORCPT ); Thu, 5 Mar 2020 12:24:10 -0500 Received: from mail.kernel.org ([198.145.29.99]:38818 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726565AbgCERNZ (ORCPT ); Thu, 5 Mar 2020 12:13:25 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BC8AB21556; Thu, 5 Mar 2020 17:13:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583428403; bh=kJdYtdkXoUJqBCbsGNBYogiLr8GIFp4ngkilDarlmMY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=e8ZeQqPe8yLy8Kpys082g7lf12klGpp12kfomwXWEVW+HLPJvnL/E7ca+LQM2FYSN CPgW+GDoROKqhtstImWRaFy1VpVoCW5/IZfu2gjbTFDx9Qoz5F3bI3QVBTAyrdt6oh U+YMKSdMx5krzFEDL65L5P1oEE+GTvX6yG4f14Xw= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Victor Kamensky , Bruce Ashfield , Paul Burton , linux-mips@vger.kernel.org, Ralf Baechle , James Hogan , Vincenzo Frascino , richard.purdie@linuxfoundation.org, Sasha Levin Subject: [PATCH AUTOSEL 5.5 10/67] mips: vdso: fix 'jalr t9' crash in vdso code Date: Thu, 5 Mar 2020 12:12:11 -0500 Message-Id: <20200305171309.29118-10-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200305171309.29118-1-sashal@kernel.org> References: <20200305171309.29118-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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(+) diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile index e05938997e696..96afd73c94e8a 100644 --- a/arch/mips/vdso/Makefile +++ b/arch/mips/vdso/Makefile @@ -29,6 +29,7 @@ endif cflags-vdso := $(ccflags-vdso) \ $(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \ -O3 -g -fPIC -fno-strict-aliasing -fno-common -fno-builtin -G 0 \ + -mrelax-pic-calls -mexplicit-relocs \ -fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \ $(call cc-option, -fno-asynchronous-unwind-tables) \ $(call cc-option, -fno-stack-protector) -- 2.20.1