From patchwork Thu Mar 19 13:03:52 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 11447229 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7AB9A17E6 for ; Thu, 19 Mar 2020 13:30:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5828120789 for ; Thu, 19 Mar 2020 13:30:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584624617; bh=2+JddXm05lMAvMt7a5HtaUlUsXMzX06xKsrUO7VAvF8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=exQIM2Mg6T1reDF1qYd9X06I3vPHGebvr+0l2QPdGCwngsmXAGOJlLe/065WYqI04 42NlZM1ZL1UmitJybboQBE9UbyoawzAm4UQ46YJjDgBpqb5xMAFeViCgtJRoyJPday pAjBXUVwtbBdjx9mQ7rMhjhF3WUuIWr0sruDIBLo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728489AbgCSNaM (ORCPT ); Thu, 19 Mar 2020 09:30:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:46986 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728927AbgCSNWC (ORCPT ); Thu, 19 Mar 2020 09:22:02 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 6A54420724; Thu, 19 Mar 2020 13:22:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584624120; bh=2+JddXm05lMAvMt7a5HtaUlUsXMzX06xKsrUO7VAvF8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ye9CSkUKT/3f+pmUOp0MLi/8cCcc5kR+VhrkJIONf/x22DSMN/CB9qO9XNX1ERdT1 cEGjXqNoXmfHk52OPIc8lUUgI3hfpE00A26hebthUwePtFCwB5i9nppcZ/5Grc0Jbh aVlKP9zyQWKQO5uIm51PS4NmLMYJLrmf1npNKQGg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Bruce Ashfield , Victor Kamensky , Paul Burton , linux-mips@vger.kernel.org, Ralf Baechle , James Hogan , Vincenzo Frascino , richard.purdie@linuxfoundation.org, Sasha Levin Subject: [PATCH 5.4 14/60] mips: vdso: fix jalr t9 crash in vdso code Date: Thu, 19 Mar 2020 14:03:52 +0100 Message-Id: <20200319123923.535642309@linuxfoundation.org> X-Mailer: git-send-email 2.25.2 In-Reply-To: <20200319123919.441695203@linuxfoundation.org> References: <20200319123919.441695203@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@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 996a934ece7d6..3fa4bbe1bae53 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)