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Currently on S/390 the .got.plt always comes first which prevents the GNU_RELRO segment from being extended across the non-plt GOT entries. Just swapping both unfortunately is not that simple since our ABI requires the _GLOBAL_OFFSET_TABLE_ symbol to point to the very beginning of the entire GOT. Of the 3 magic GOT entries the first is accessed via got pointer while second and third are being accessed via DT_PLTGOT. In order to keep them together we make DT_PLTGOT to point to the .got instead of .got.plt. However, this violates an assumption in the dynamic linker prelink undo code about the GOTPLT entries starting at DT_PLTGOT + 3. We got rid of this requirement with a Glibc patch already in version 2.24: https://sourceware.org/ml/libc-alpha/2016-06/msg01302.html So the S/390 relro GOT layout will look like this with this patch: +----------------------------------+ |got[0]: DYNAMIC | <--- _GLOBAL_OFFSET_TABLE_ == DT_PLTGOT .got |got[1]: link_map parm | |got[2]: &_dl_runtime_resolve | +----------------------------------+ | | non-plt GOT entries | | | | +----------------------------------+ | | <--- .gotplt, PLT GOT entries | | | | | | +----------------------------------+ The patch detects the current layout in size_dynamic_section in order to deal also with linker scripts not generated by this ld version. With partial relro enabled we pick a linker script where .got and .got.plt are swapped which then triggers the rest of the logic. ld/ChangeLog: 2018-07-18 Andreas Krebbel <krebbel@linux.ibm.com> * emulparams/elf64_s390.sh: Define GENERATE_RELRO_SCRIPT and SEPARATE_GOTPLT. * testsuite/ld-s390/gotreloc_64-relro-1.dd: New test. * testsuite/ld-s390/gotreloc_64-norelro-1.dd: Renamed from ... * testsuite/ld-s390/gotreloc_64-1.dd: ... this. * testsuite/ld-s390/s390.exp: Split the GOT testcase into two. bfd/ChangeLog: 2018-07-18 Andreas Krebbel <krebbel@linux.ibm.com> * elf-s390-common.c (s390_gotplt_after_got_p): New function. (s390_got_pointer): New function. (s390_got_offset): New function. (s390_gotplt_offset): New function. * elf64-s390.c (allocate_dynrelocs): Adjust comment. (elf_s390_size_dynamic_sections): Move space for magic GOT entries from .got.plt to .got if necessary and pick the right location for _GLOBAL_OFFSET_TABLE_. (elf_s390_relocate_section): Use the wrapper functions from elf-s390-common.c to deal with both possible layouts (either .got or .got.plt first). (elf_s390_finish_dynamic_sections): Likewise. (elf_s390_finish_dynamic_symbol): Make the location of the GOT magic entries conditional.
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.