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Date: Thu, 11 Jun 2020 23:33:45 +0200
From: Mikhail Morfikov <mmorfikov@...il.com>
To: lkrg-users@...ts.openwall.com
Subject: Re: RE: ISRA optimized functions
On 11/06/2020 23:14, Mikhail Morfikov wrote:
> On 11/06/2020 22:34, Adam Zabrocki wrote:
>>
>> Sure, however, from the logs below it looks like you've compiled Linux kernel
>> using -O2 flag.
>>
>
> Yes, but in both cases this flag was used, and in the case of gcc9 it looks like
> it doesn't matter (because LKRG works well), and in the case of gcc10 it does
> (since it has the problem with the function). So the question here is why? All I
> did was using update-alternatives to configure the gcc/g++/cpp links, and nothing
> else have changed in my system. So why does it work with the kernel built with
> gcc9 and it doesn't work with kernel built with gcc10?
>
I just checked, and the flags aren't used in the kernel build process:
$ make ARCH="x86_64" -j3 bindeb-pkg
sh ./scripts/package/mkdebian
dpkg-buildpackage -r"fakeroot -u" -a$(cat debian/arch) -b -nc -uc
dpkg-buildpackage: info: source package linux-5.7.2-amd64
dpkg-buildpackage: info: source version 5.7.2-amd64-8
dpkg-buildpackage: info: source distribution sid
dpkg-buildpackage: info: source changed by Mikhail Morfikov <mmorfikov@...il.com>
dpkg-buildpackage: info: host architecture amd64
dpkg-source --before-build .
debian/rules build
dpkg-buildflags --status
dpkg-buildflags: status: environment variable DEB_BUILD_OPTIONS=parallel=4
dpkg-buildflags: status: environment variable DEB_HOST_ARCH=amd64
dpkg-buildflags: status: vendor is Debian
dpkg-buildflags: status: future features: lfs=no
dpkg-buildflags: status: hardening features: bindnow=no format=yes fortify=yes pie=yes relro=yes stackprotector=yes stackprotectorstrong=yes
dpkg-buildflags: status: qa features: bug=no canary=no
dpkg-buildflags: status: reproducible features: fixdebugpath=yes fixfilepath=no timeless=yes
dpkg-buildflags: status: sanitize features: address=no leak=no thread=no undefined=no
dpkg-buildflags: status: CFLAGS [user]: -g -fdebug-prefix-map=/media/debian_sources/git-kernel/linux-5.7=. -fstack-protector-strong -Wformat -Werror=format-security
dpkg-buildflags: status: CPPFLAGS [vendor]: -Wdate-time -D_FORTIFY_SOURCE=2
dpkg-buildflags: status: CXXFLAGS [user]: -g -fdebug-prefix-map=/media/debian_sources/git-kernel/linux-5.7=. -fstack-protector-strong -Wformat -Werror=format-security
dpkg-buildflags: status: FCFLAGS [user]: -g -fdebug-prefix-map=/media/debian_sources/git-kernel/linux-5.7=. -fstack-protector-strong
dpkg-buildflags: status: FFLAGS [user]: -g -fdebug-prefix-map=/media/debian_sources/git-kernel/linux-5.7=. -fstack-protector-strong
dpkg-buildflags: status: GCJFLAGS [user]: -g -fdebug-prefix-map=/media/debian_sources/git-kernel/linux-5.7=. -fstack-protector-strong
dpkg-buildflags: status: LDFLAGS [vendor]: -Wl,-z,relro
dpkg-buildflags: status: OBJCFLAGS [user]: -g -fdebug-prefix-map=/media/debian_sources/git-kernel/linux-5.7=. -fstack-protector-strong -Wformat -Werror=format-security
dpkg-buildflags: status: OBJCXXFLAGS [user]: -g -fdebug-prefix-map=/media/debian_sources/git-kernel/linux-5.7=. -fstack-protector-strong -Wformat -Werror=format-security
make KERNELRELEASE=5.7.2-amd64 ARCH=x86_64 KBUILD_BUILD_VERSION=8 -f ./Makefile
DESCEND objtool
CALL scripts/atomic/check-atomics.sh
CALL scripts/checksyscalls.sh
CHK include/generated/compile.h
UPD include/generated/compile.h
CC init/version.o
AR init/built-in.a
GEN .version
CHK include/generated/compile.h
LD vmlinux.o
MODPOST vmlinux.o
MODINFO modules.builtin.modinfo
GEN modules.builtin
LD .tmp_vmlinux.kallsyms1
KSYM .tmp_vmlinux.kallsyms1.o
LD .tmp_vmlinux.kallsyms2
KSYM .tmp_vmlinux.kallsyms2.o
LD vmlinux
SORTTAB vmlinux
SYSMAP System.map
MODPOST 0 modules
CC arch/x86/boot/version.o
VOFFSET arch/x86/boot/compressed/../voffset.h
OBJCOPY arch/x86/boot/compressed/vmlinux.bin
RELOCS arch/x86/boot/compressed/vmlinux.relocs
CC arch/x86/boot/compressed/kaslr.o
XZKERN arch/x86/boot/compressed/vmlinux.bin.xz
CC arch/x86/boot/compressed/misc.o
MKPIGGY arch/x86/boot/compressed/piggy.S
AS arch/x86/boot/compressed/piggy.o
LD arch/x86/boot/compressed/vmlinux
ZOFFSET arch/x86/boot/zoffset.h
OBJCOPY arch/x86/boot/vmlinux.bin
AS arch/x86/boot/header.o
LD arch/x86/boot/setup.elf
OBJCOPY arch/x86/boot/setup.bin
BUILD arch/x86/boot/bzImage
Setup is 14396 bytes (padded to 14848 bytes).
System is 10336 kB
CRC 514b895b
Kernel: arch/x86/boot/bzImage is ready (#9)
fakeroot -u debian/rules binary
make KERNELRELEASE=5.7.2-amd64 ARCH=x86_64 KBUILD_BUILD_VERSION=8 -f ./Makefile intdeb-pkg
sh ./scripts/package/builddeb
DEPMOD 5.7.2-amd64
dpkg-deb: building package 'linux-headers-5.7.2-amd64' in '../linux-headers-5.7.2-amd64_5.7.2-amd64-8_amd64.deb'.
INSTALL debian/linux-libc-dev/usr/include
dpkg-deb: building package 'linux-libc-dev' in '../linux-libc-dev_5.7.2-amd64-8_amd64.deb'.
dpkg-deb: building package 'linux-image-5.7.2-amd64' in '../linux-image-5.7.2-amd64_5.7.2-amd64-8_amd64.deb'.
dpkg-genbuildinfo --build=binary
dpkg-genchanges --build=binary >../linux-5.7.2-amd64_5.7.2-amd64-8_amd64.changes
dpkg-genchanges: info: binary-only upload (no source code included)
dpkg-source --after-build .
dpkg-buildpackage: info: binary-only upload (no source included)
Here I stripped the -02 (via ~/.config/dpkg/buildflags.conf) and as you can see
the kernel wasn't recompiled, so the flags weren't taken into consideration,
and probably it uses the default set of flags which all debian systems use. So
still what could be wrong with the gcc10 compared to gcc9?
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