From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 7386021A0483B for ; Fri, 31 Mar 2017 01:59:30 -0700 (PDT) Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C9B95C20809F; Fri, 31 Mar 2017 08:59:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com C9B95C20809F Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=lersek@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com C9B95C20809F Received: from lacos-laptop-7.usersys.redhat.com (ovpn-116-31.phx2.redhat.com [10.3.116.31]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3778378375; Fri, 31 Mar 2017 08:59:27 +0000 (UTC) To: Ard Biesheuvel , edk2-devel@lists.01.org, leif.lindholm@linaro.org References: <20170331084013.4203-1-ard.biesheuvel@linaro.org> Cc: marc.zyngier@arm.com, yonghong.zhu@intel.com, liming.gao@intel.com From: Laszlo Ersek Message-ID: <2db957f3-f5a1-0ad6-5684-a0f489cabeec@redhat.com> Date: Fri, 31 Mar 2017 10:59:27 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20170331084013.4203-1-ard.biesheuvel@linaro.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Fri, 31 Mar 2017 08:59:30 +0000 (UTC) Subject: Re: [PATCH v2] BaseTools/GCC AARCH64: force disable PIC code generation X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 31 Mar 2017 08:59:30 -0000 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit On 03/31/17 10:40, Ard Biesheuvel wrote: > As a security measure, some distro toolchains now default to PIC code > generation, allowing executables (as opposed to shared libraries) using > the objects to be built as PIE binaries, which can be loaded at a random > virtual offset. > > However, our ELF to PE/COFF generation code does not deal with the > resulting relocation types (i.e., GOT based), and so the use of PIC code > leads to GenFw errors. > > Given that > a) our non-PIC PE/COFF executables are already relocatable, > b) PIC code leads to all symbol references to be indirected via GOT > entries containing absolute addresses, each requiring an entry in the > relocation table, > c) the AArch64 ISA makes it perfectly feasible to built PIE executables > from non-PIC code, > > there is absolutely no upside to using PIC code for building EDK2 modules, > and so we're better off simply disabling it unconditionally. > > Note that when running under the OS, the GOT has an additional advantage, > i.e., that all .text/.rodata pages remain clean and so can be shared between > processes. This does not apply to the UEFI environment, however. > > Contributed-under: TianoCore Contribution Agreement 1.0 > Signed-off-by: Ard Biesheuvel > --- > BaseTools/Conf/tools_def.template | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template > index 0aabdeb2d973..2c5cd5808912 100755 > --- a/BaseTools/Conf/tools_def.template > +++ b/BaseTools/Conf/tools_def.template > @@ -4341,7 +4341,7 @@ DEFINE GCC_X64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mno-red-zone -Wno-ad > DEFINE GCC_IPF_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -minline-int-divide-min-latency > DEFINE GCC_ARM_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -mabi=aapcs -fno-short-enums -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -fno-builtin -Wno-address -mthumb -mfloat-abi=soft > DEFINE GCC_ARM_CC_XIPFLAGS = -mno-unaligned-access > -DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char -ffunction-sections -fdata-sections -fno-builtin -Wno-address -fno-asynchronous-unwind-tables > +DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char -ffunction-sections -fdata-sections -fno-builtin -Wno-address -fno-asynchronous-unwind-tables -fno-pic > DEFINE GCC_AARCH64_CC_XIPFLAGS = -mstrict-align > DEFINE GCC_DLINK_FLAGS_COMMON = -nostdlib --pie > DEFINE GCC_DLINK2_FLAGS_COMMON = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/GccBase.lds > Sounds convincing enough to me. I find it quite annoying that such an important property of code generation (-fpic or -fno-pic by default) varies across distros. Well, security. Acked-by: Laszlo Ersek