On Tuesday 11 October 2022 08:46:58 Richard Biener wrote:
> On Mon, Oct 10, 2022 at 7:19 PM Pali Rohár via Gcc <gcc@gcc.gnu.org> wrote:
> >
> > Hello!
> >
> > During development and debugging of U-Boot bootloader I got strange
> > error from ARM GNU assembler, which looks like a bug in binutils or gcc.
> >
> > Below is simplified code which can trigger it:
> >
> > $ cat test.S
> > kernoffs:
> > .word KERNEL_OFFSET - (. - CONFIG_SYS_TEXT_BASE)
> >
> > $ arm-linux-gnueabi-gcc -DKERNEL_OFFSET=0x40000
> > -DCONFIG_SYS_TEXT_BASE=0x80008000 -pipe -c test.S
> > {standard input}: Assembler messages:
> > {standard input}: Error: attempt to get value of unresolved symbol `L0'
> >
> > I do not use any L0 symbol in the code, so error message seems to be
> > incorrect. And also I do not think that there is issue in that simple
> > assembler code.
>
> You are using (. - CONFIG_SYS_TEXT_BASE) where '.' is the "current"
> address, that's where L0 (a local label) gets introduced internally. I think
> this is an assembler issue or this use is not supported. Simplified testcase:
>
> > cat t.s
> kernoffs:
> .word - (. - 0x80008000)
> > as -o t.o t.s
> t.s: Assembler messages:
> t.s: Error: attempt to get value of unresolved symbol `L0'
>
> Richard.
Interesting... Another test case which is working fine:
kernoffs:
.word 0x40000 - (. - 0x0)
So which use case could not be supported? I still do not see pattern
what can be accepted and what not.
I have feeling that this is assembler issue somewhere...
> >
> > On the other hand, if I declare negated value then compilation passes
> > without any error/warning. Code is:
> >
> > kernoffs:
> > .word . - CONFIG_SYS_TEXT_BASE - KERNEL_OFFSET
> >
> > It is quite strange that negated value can be compiled by gcc/as without
> > issue here.
> >
> > I was told that I should report this issue, so I'm sending email to
> > binutils and gcc mailing list.
> >
> > Do you have any idea where is the issue? It is a bug in gcc / as or is
> > there some syntax / semantic error in that simple example?
> >
> > Just for the record I'm using standard ARM cross compiler available on
> > Debian 10 Buster system. Here are version information:
> >
> > $ arm-linux-gnueabi-gcc -v
> > Using built-in specs.
> > COLLECT_GCC=arm-linux-gnueabi-gcc
> > COLLECT_LTO_WRAPPER=/usr/lib/gcc-cross/arm-linux-gnueabi/8/lto-wrapper
> > Target: arm-linux-gnueabi
> > Configured with: ../src/configure -v --with-pkgversion='Debian 8.3.0-2'
> > --with-bugurl=file:///usr/share/doc/gcc-8/README.Bugs
> > --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++ --prefix=/usr
> > --with-gcc-major-version-only --program-suffix=-8 --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-libitm --disable-libquadmath --disable-libquadmath-support
> > --enable-plugin --enable-default-pie --with-system-zlib
> > --with-target-system-zlib --enable-multiarch --disable-sjlj-exceptions
> > --with-arch=armv5te --with-float=soft --disable-werror
> > --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
> > --target=arm-linux-gnueabi --program-prefix=arm-linux-gnueabi-
> > --includedir=/usr/arm-linux-gnueabi/include
> > Thread model: posix
> > gcc version 8.3.0 (Debian 8.3.0-2)
> >
> > $ arm-linux-gnueabi-as --version
> > GNU assembler (GNU Binutils for Debian) 2.31.1
> > Copyright (C) 2018 Free Software Foundation, Inc.
> > This program is free software; you may redistribute it under the terms of
> > the GNU General Public License version 3 or later.
> > This program has absolutely no warranty.
> > This assembler was configured for a target of `arm-linux-gnueabi'.
