Re: build failure on ia64 (+ patch), "relocation truncated to fit: GPREL22 against `.text'"

[Sam James <sam@gentoo.org>]

Adhemerval Zanella Netto via Libc-alpha <libc-alpha@sourceware.org> writes:

> On 30/07/23 05:10, Florian Weimer wrote:
>> * Andreas K. Huettel via Libc-alpha:
>> 
>>> diff --git a/sysdeps/unix/sysv/linux/ia64/dl-sysdep.h b/sysdeps/unix/sysv/linux/ia64/dl-sysdep.h
>>> index 3e4d5da820..eb7681b704 100644
>>> --- a/sysdeps/unix/sysv/linux/ia64/dl-sysdep.h
>>> +++ b/sysdeps/unix/sysv/linux/ia64/dl-sysdep.h
>>> @@ -32,7 +32,9 @@
>>>  #ifndef __ASSEMBLER__
>>>  /* Don't declare this as a function---we want it's entry-point, not
>>>     it's function descriptor... */
>>> -extern int _dl_sysinfo_break attribute_hidden;
>>> +/* Use section ".text" to force far GPREL64 relocation instead of
>>> +   GPREL22 . */
>>> +extern int _dl_sysinfo_break attribute_hidden __attribute__((section(".text")));
>> 
>> More context:
>> 
>> | /* Don't declare this as a function---we want it's entry-point, not
>> |    it's function descriptor... */
>> | extern int _dl_sysinfo_break attribute_hidden;
>> | # define DL_SYSINFO_DEFAULT ((uintptr_t) &_dl_sysinfo_break)
>> | # define DL_SYSINFO_IMPLEMENTATION              \
>> |   asm (".text\n\t"                              \
>> |        ".hidden _dl_sysinfo_break\n\t"          \
>> |        ".proc _dl_sysinfo_break\n\t"            \
>> |        "_dl_sysinfo_break:\n\t"                 \
>> |        ".prologue\n\t"                          \
>> |        ".altrp b6\n\t"                          \
>> |        ".body\n\t"                              \
>> |        "break 0x100000;\n\t"                    \
>> |        "br.ret.sptk.many b6;\n\t"               \
>> |        ".endp _dl_sysinfo_break\n\t"            \
>> |        ".previous");
>> | #endif
>> 
>> So this seems actually correct because the symbol is defined in .text.
>> (I was wondered why this would make .text writable.)
>
> That was my understanding back then as well, and I tested myself the testcase
> Sergei has created [1] and at least with gcc from 6 to 13 built with 
> build-many-glibcs.py I don't see any relocation failure.  But at same time
> I don't see any relocation failure with current code either, so I am not
> sure why this is happening with Gentoo toolchain (maybe a incomplete backport?).

I don't think we do much interesting there though. We had a user report
this again a few days ago with 13.

Our patchset at the moment is
https://gitweb.gentoo.org/proj/gcc-patches.git/tree/13.2.0/gentoo.

with
```
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/ia64-unknown-linux-gnu/13/lto-wrapper
Target: ia64-unknown-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-13.2.0/work/gcc-13.2.0/configure --host=ia64-unknown-linux-gnu --build=ia64-unknown-linux-gnu --prefix=/usr --bindir=/usr/ia64-unknown-linux-gnu/gcc-bin/13 --includedir=/usr/lib/gcc/ia64-unknown-linux-gnu/13/include --datadir=/usr/share/gcc-data/ia64-unknown-linux-gnu/13 --mandir=/usr/share/gcc-data/ia64-unknown-linux-gnu/13/man --infodir=/usr/share/gcc-data/ia64-unknown-linux-gnu/13/info --with-gxx-include-dir=/usr/lib/gcc/ia64-unknown-linux-gnu/13/include/g++-v13 --with-python-dir=/share/gcc-data/ia64-unknown-linux-gnu/13/python --enable-languages=c,c++,fortran --enable-obsolete --enable-secureplt --disable-werror --with-system-zlib --enable-nls --without-included-gettext --disable-libunwind-exceptions --enable-checking=release --with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo 13.2.0 p3' --with-gcc-major-version-only --enable-libstdcxx-time --enable-lto --disable-libstdcxx-pch --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --disable-multilib --disable-fixed-point --enable-libgomp --disable-libssp --disable-libada --disable-cet --disable-systemtap --disable-valgrind-annotations --disable-vtable-verify --disable-libvtv --without-zstd --without-isl --disable-libsanitizer --enable-default-pie --enable-default-ssp
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 13.2.0 (Gentoo 13.2.0 p3)
```

>
> ---
> $ cat mk.bash
> #!/usr/bin/bash
>
> if [ $# -eq 0 ]; then
>   echo "usage: mk.bash compiler"
>   exit 0;
> fi
>
> CC=$1
>
> cat > conftest.c << EOF
> #ifdef USE_TEXT
> extern int asm_f __attribute__((visibility("hidden"))) __attribute__((section(".text")));
> #else
> extern int asm_f __attribute__((visibility("hidden")));
> #endif
>
> long asm_f_ref;
>
> asm (
> ".text\n\t" \
>    ".hidden asm_f\n\t"
>    ".proc asm_f\n\t"
> "asm_f:\n\t"
>    ".prologue\n\t"
>    ".body\n\t"
>    "br.ret.sptk.many b0;\n\t"
>    ".endp asm_f\n\t"
> ".previous"
> );
> EOF
>
> for define in "" "-DUSE_TEST"; do
>  for static in "" "-static"; do
>   for fpie in "" "-fPIE"; do
>    for common in "-fcommon" "-fno-common"; do
>     echo -n "define=${define} static=${static} common=${common} fpie=${fpie}: "
>     $CC conftest.c -o a -O2 -nostdlib -nostartfiles -e asm_f_ref \
>             ${static} ${define} ${fpie} ${common} 2>&1 >/dev/null
>     if [ $? -eq 0 ]; then
>       echo "OK"
>     else
>       echo "FAIL"
>     fi
>    done
>   done
>  done
> done
>
> rm conftest.c
> ---
>
>
> [1] https://sourceware.org/pipermail/libc-alpha/2020-May/114493.html