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[solved]Linux 5.9 arm64: ld.bfd: warning: -z norelro ignored
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Etal
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PostPosted: Fri Oct 16, 2020 11:31 pm    Post subject: [solved]Linux 5.9 arm64: ld.bfd: warning: -z norelro ignored Reply with quote

Anyone know what's causing this warning when I compile the Linux 5.9 kernel? I don't think I've seen it previously. This is vanilla-sources-5.9.0.

Code:
make LD=ld.bfd -j4
...
  GEN     .version
  CHK     include/generated/compile.h
  LD      vmlinux.o
  MODPOST vmlinux.symvers
  MODINFO modules.builtin.modinfo
  GEN     modules.builtin
  LD      .tmp_vmlinux.kallsyms1
ld.bfd: warning: -z norelro ignored
  KSYM    .tmp_vmlinux.kallsyms1.o
  LD      .tmp_vmlinux.kallsyms2
ld.bfd: warning: -z norelro ignored
  KSYM    .tmp_vmlinux.kallsyms2.o
  LD      vmlinux
ld.bfd: warning: -z norelro ignored
  SORTTAB vmlinux
  SYSMAP  System.map
  OBJCOPY arch/arm64/boot/Image
  GZIP    arch/arm64/boot/Image.gz


Last edited by Etal on Sun Nov 15, 2020 3:54 pm; edited 1 time in total
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erm67
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PostPosted: Sat Oct 17, 2020 4:52 pm    Post subject: Reply with quote

for me vanilla 5.9.1 & gcc 10.2.0 compiles flawlessly.
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Etal
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PostPosted: Sat Oct 17, 2020 7:36 pm    Post subject: Reply with quote

Thanks for confirming. Do you have CONFIG_RELOCATABLE on?

Yesterday I ended up cross-compiling with clang/lld (CC=clang LLVM=1) which built without issues.

But if I switch CONFIG_RELOCATABLE off, it builds fine with gcc as well.

I probably don't need it. I think it's only useful for CONFIG_RANDOMIZE_BASE but my bootloader doesn't provide entropy so I can't use it.
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erm67
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PostPosted: Sat Oct 17, 2020 8:49 pm    Post subject: Reply with quote

Code:
CONFIG_RELOCATABLE=y
CONFIG_RANDOMIZE_BASE=y


Code:
 ld.bfd -v
GNU ld (GNU Binutils) 2.35
 gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/aarch64-unknown-linux-gnu/10.2.0/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=https://github.com/archlinuxarm/PKGBUILDs/issues --enable-languages=c,c++,fortran,go,lto,objc,obj-c++,d --with-isl --with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit --enable-checking=release --enable-clocale=gnu --enable-default-pie --enable-default-ssp --enable-gnu-indirect-function --enable-gnu-unique-object --enable-install-libiberty --enable-linker-build-id --enable-lto --enable-plugin --enable-shared --enable-threads=posix --disable-libssp --disable-libstdcxx-pch --disable-libunwind-exceptions --disable-multilib --disable-werror --host=aarch64-unknown-linux-gnu --build=aarch64-unknown-linux-gnu --with-arch=armv8-a --enable-fix-cortex-a53-835769 --enable-fix-cortex-a53-843419 gdc_include_dir=/usr/include/dlang/gdc
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.2.0 (GCC)


Probably the -zrelro conflicts with relocatable but where does it come from?
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Ionen
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PostPosted: Sat Oct 17, 2020 9:02 pm    Post subject: Reply with quote

erm67 wrote:
Probably the -zrelro conflicts with relocatable but where does it come from?
Not familiar with arm to know what is happening here but binutils in gentoo is built with --enable-relro which makes it default for ELF targets.
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Etal
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PostPosted: Sat Oct 17, 2020 10:14 pm    Post subject: Reply with quote

Mine's slightly newer:

Code:
$ ld.bfd -v
GNU ld (Gentoo 2.35.1 p1) 2.35.1
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/aarch64-unknown-linux-gnu/10.2.0/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-10.2.0-r2/work/gcc-10.2.0/configure --host=aarch64-unknown-linux-gnu --target=aarch64-unknown-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr --bindir=/usr/aarch64-unknown-linux-gnu/gcc-bin/10.2.0 --includedir=/usr/lib/gcc/aarch64-unknown-linux-gnu/10.2.0/include --datadir=/usr/share/gcc-data/aarch64-unknown-linux-gnu/10.2.0 --mandir=/usr/share/gcc-data/aarch64-unknown-linux-gnu/10.2.0/man --infodir=/usr/share/gcc-data/aarch64-unknown-linux-gnu/10.2.0/info --with-gxx-include-dir=/usr/lib/gcc/aarch64-unknown-linux-gnu/10.2.0/include/g++-v10 --with-python-dir=/share/gcc-data/aarch64-unknown-linux-gnu/10.2.0/python --enable-languages=c,c++ --enable-obsolete --enable-secureplt --disable-werror --with-system-zlib --disable-nls --enable-checking=release --with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo 10.2.0-r2 p3' --disable-esp --enable-libstdcxx-time --with-build-config=bootstrap-lto --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --disable-multilib --disable-fixed-point --enable-libgomp --disable-libssp --disable-libada --disable-systemtap --enable-vtable-verify --without-zstd --enable-lto --without-isl --enable-default-pie --enable-default-ssp
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.2.0 (Gentoo 10.2.0-r2 p3)


The "-z norelro" comes from a kernel Makefile:
Code:
/usr/src/linux-5.9.0/arch/arm64/Makefile-ifeq ($(CONFIG_RELOCATABLE), y)
/usr/src/linux-5.9.0/arch/arm64/Makefile-# Pass --no-apply-dynamic-relocs to restore pre-binutils-2.27 behaviour
/usr/src/linux-5.9.0/arch/arm64/Makefile-# for relative relocs, since this leads to better Image compression
/usr/src/linux-5.9.0/arch/arm64/Makefile-# with the relocation offsets always being zero.
/usr/src/linux-5.9.0/arch/arm64/Makefile:LDFLAGS_vmlinux      += -shared -Bsymbolic -z notext -z norelro \
/usr/src/linux-5.9.0/arch/arm64/Makefile-         $(call ld-option, --no-apply-dynamic-relocs)
/usr/src/linux-5.9.0/arch/arm64/Makefile-endif
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Ionen
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PostPosted: Mon Nov 02, 2020 11:47 am    Post subject: Reply with quote

Seem 5.9.3 changed something regarding this:
Code:
arm64: link with -z norelro regardless of CONFIG_RELOCATABLE
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Etal
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PostPosted: Tue Nov 03, 2020 3:48 am    Post subject: Reply with quote

Now with 5.9.3 it shows the warning even if CONFIG_RELOCATABLE is off, because that patch made it so that, uh, it links "with -z norelro regardless of CONFIG_RELOCATABLE" :lol:

https://lore.kernel.org/linux-arm-kernel/20201016175339.2429280-1-ndesaulniers@google.com

Quote:
ld.lld defaults to -z relro while ld.bfd defaults to -z norelro. This
was previously fixed, but only for CONFIG_RELOCATABLE=y.

Does that mean the warning just says it's ignored because it's the default?
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Etal
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PostPosted: Sun Nov 15, 2020 3:53 pm    Post subject: Reply with quote

I updated to 5.9.8 and everything was fine despite the warnings, so marking as solved.
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erm67
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PostPosted: Sun Nov 15, 2020 6:28 pm    Post subject: Reply with quote

I think I should compile a kernel :-)

BTW I got the warning with one of the 5.10-rcs some time ago.
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