Re: [PATCH] BaseTools/tools_def IA32: disable PIE code generation explicitly

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 11 June 2018 at 18:00, Gao, Liming <liming.gao@intel.com> wrote:
> Ard:
>   Is this option required in GCC49 tool chain? Or, this option is only required when lto is enabled?
>

It has nothing to do with LTO.

In theory, it could be required for any toolchain that supports -fpic
and or -fpie. However, not all 4.x toolchains support -fpie and so
they don't support -fno-pie either.

Given that the distros only changed this default recently (in the 5.x
timeframe or later), it makes sense to only disable it for GCC5,
although it is safe to disable it for GCC49 as well.

>> -----Original Message-----
>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Ard Biesheuvel
>> Sent: Monday, June 11, 2018 4:53 PM
>> To: Gao, Liming <liming.gao@intel.com>
>> Cc: edk2-devel@lists.01.org; lersek@redhat.com; zenith432@users.sourceforge.net
>> Subject: Re: [edk2] [PATCH] BaseTools/tools_def IA32: disable PIE code generation explicitly
>>
>> On 11 June 2018 at 10:38, Gao, Liming <liming.gao@intel.com> wrote:
>> > Ard:
>> >   Do you mean the default GCC compiler disables PIC and PIE for IA32 arch? But now, some distribution GCC compiler enables PIC
>> and PIE by default. So, we have to obviously disable PIC and PIE in tools_def.txt.
>> >
>>
>> Yes. On my x86 Ubuntu 18.04 LTS system:
>>
>> $ gcc -v
>> Using built-in specs.
>> COLLECT_GCC=gcc
>> COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/7/lto-wrapper
>> OFFLOAD_TARGET_NAMES=nvptx-none
>> OFFLOAD_TARGET_DEFAULT=1
>> Target: x86_64-linux-gnu
>> Configured with: ../src/configure -v --with-pkgversion='Ubuntu
>> 7.3.0-16ubuntu3' --with-bugurl=file:///usr/share/doc/gcc-7/README.Bugs
>> --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++
>> --prefix=/usr --with-gcc-major-version-only
>> --with-as=/usr/bin/x86_64-linux-gnu-as
>> --with-ld=/usr/bin/x86_64-linux-gnu-ld --program-suffix=-7
>> --program-prefix=x86_64-linux-gnu- --enable-shared
>> --enable-linker-build-id --libexecdir=/usr/lib
>> --without-included-gettext --enable-threads=posix --libdir=/usr/lib
>> --enable-nls --with-sysroot=/ --enable-clocale=gnu
>> --enable-libstdcxx-debug --enable-libstdcxx-time=yes
>> --with-default-libstdcxx-abi=new --enable-gnu-unique-object
>> --disable-vtable-verify --enable-libmpx --enable-plugin
>> --enable-default-pie --with-system-zlib --with-target-system-zlib
>> --enable-objc-gc=auto --enable-multiarch --disable-werror
>> --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32
>> --enable-multilib --with-tune=generic
>> --enable-offload-targets=nvptx-none --without-cuda-driver
>> --enable-checking=release --build=x86_64-linux-gnu
>> --host=x86_64-linux-gnu --target=x86_64-linux-gnu
>> Thread model: posix
>> gcc version 7.3.0 (Ubuntu 7.3.0-16ubuntu3)
>>
>>
>> Notice the '--enable-default-pie' 4 lines from the bottom.
>>
>>
>>
>> >>-----Original Message-----
>> >>From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
>> >>Sent: Monday, June 11, 2018 3:42 PM
>> >>To: edk2-devel@lists.01.org
>> >>Cc: Zhu, Yonghong <yonghong.zhu@intel.com>; Gao, Liming
>> >><liming.gao@intel.com>; lersek@redhat.com; Shi, Steven
>> >><steven.shi@intel.com>; zenith432@users.sourceforge.net; Ard Biesheuvel
>> >><ard.biesheuvel@linaro.org>
>> >>Subject: [PATCH] BaseTools/tools_def IA32: disable PIE code generation
>> >>explicitly
>> >>
>> >>As a security measure, some distros now build their GCC toolchains with
>> >>PIE code generation enabled by default, because it is a prerequisite
>> >>for ASLR to be enabled when running the executable.
>> >>
>> >>This typically results in slightly larger code, but it also generates
>> >>ELF relocations that our tooling cannot deal with, so let's disable it
>> >>explicitly when using GCC5 for IA32. (Note that this does not apply to
>> >>X64: it uses PIE code deliberately in some cases, and our tooling does
>> >>deal with the resuling relocations)
>> >>
>> >>Contributed-under: TianoCore Contribution Agreement 1.1
>> >>Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> >>---
>> >> BaseTools/Conf/tools_def.template | 6 +++---
>> >> 1 file changed, 3 insertions(+), 3 deletions(-)
>> >>
>> >>diff --git a/BaseTools/Conf/tools_def.template
>> >>b/BaseTools/Conf/tools_def.template
>> >>index 7e9c915755ed..ab57f9c706e3 100755
>> >>--- a/BaseTools/Conf/tools_def.template
>> >>+++ b/BaseTools/Conf/tools_def.template
>> >>@@ -4670,7 +4670,7 @@ DEFINE GCC49_AARCH64_DLINK2_FLAGS    =
>> >>DEF(GCC48_AARCH64_DLINK2_FLAGS)
>> >> DEFINE GCC49_ARM_ASLDLINK_FLAGS      =
>> >>DEF(GCC48_ARM_ASLDLINK_FLAGS)
>> >> DEFINE GCC49_AARCH64_ASLDLINK_FLAGS  =
>> >>DEF(GCC48_AARCH64_ASLDLINK_FLAGS)
>> >>
>> >>-DEFINE GCC5_IA32_CC_FLAGS            = DEF(GCC49_IA32_CC_FLAGS)
>> >>+DEFINE GCC5_IA32_CC_FLAGS            = DEF(GCC49_IA32_CC_FLAGS) -fno-pic
>> >>-fno-pie
>> >> DEFINE GCC5_X64_CC_FLAGS             = DEF(GCC49_X64_CC_FLAGS)
>> >> DEFINE GCC5_IA32_X64_DLINK_COMMON    =
>> >>DEF(GCC49_IA32_X64_DLINK_COMMON)
>> >> DEFINE GCC5_IA32_X64_ASLDLINK_FLAGS  =
>> >>DEF(GCC49_IA32_X64_ASLDLINK_FLAGS)
>> >>@@ -5502,9 +5502,9 @@ RELEASE_GCC49_AARCH64_DLINK_FLAGS  =
>> >>DEF(GCC49_AARCH64_DLINK_FLAGS)
>> >> *_GCC5_IA32_RC_PATH              = DEF(GCC5_IA32_PREFIX)objcopy
>> >>
>> >> *_GCC5_IA32_ASLCC_FLAGS          = DEF(GCC_ASLCC_FLAGS) -m32 -fno-lto
>> >>-*_GCC5_IA32_ASLDLINK_FLAGS       = DEF(GCC5_IA32_X64_ASLDLINK_FLAGS)
>> >>-Wl,-m,elf_i386
>> >>+*_GCC5_IA32_ASLDLINK_FLAGS       =
>> >>DEF(GCC5_IA32_X64_ASLDLINK_FLAGS) -Wl,-m,elf_i386 -no-pie
>> >> *_GCC5_IA32_ASM_FLAGS            = DEF(GCC5_ASM_FLAGS) -m32 -
>> >>march=i386
>> >>-*_GCC5_IA32_DLINK2_FLAGS         = DEF(GCC5_IA32_DLINK2_FLAGS)
>> >>+*_GCC5_IA32_DLINK2_FLAGS         = DEF(GCC5_IA32_DLINK2_FLAGS) -no-
>> >>pie
>> >> *_GCC5_IA32_RC_FLAGS             = DEF(GCC_IA32_RC_FLAGS)
>> >> *_GCC5_IA32_OBJCOPY_FLAGS        =
>> >> *_GCC5_IA32_NASM_FLAGS           = -f elf32
>> >>--
>> >>2.17.1
>> >
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