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Variables defined in shared libraries are copied into an executable's .bss section when code in the executable is non-PIC and thus would require dynamic text relocations to access the variable directly in the shared library. Recent x86 toolchains also copy variables into the executable to gain a small speed improvement. The problem is that if the variable was originally read-only, the copy in .bss is writable, potentially opening a security hole. This patch cures that problem by putting the copy in a section that becomes read-only after ld.so relocation, provided -z relro is in force. The patch also fixes a microblaze linker segfault on attempting to use dynamic bss variables. bfd/ PR ld/20995 * elf-bfd.h (struct elf_link_hash_table): Add sdynrelro and sreldynrelro. (struct elf_backend_data): Add want_dynrelro. * elfxx-target.h (elf_backend_want_dynrelro): Define. (elfNN_bed): Update initializer. * elflink.c (_bfd_elf_create_dynamic_sections): Create sdynrelro and sreldynrelro sections. * elf32-arm.c (elf32_arm_adjust_dynamic_symbol): Place variables copied into the executable from read-only sections into sdynrelro. (elf32_arm_size_dynamic_sections): Handle sdynrelro. (elf32_arm_finish_dynamic_symbol): Select sreldynrelro for dynamic relocs in sdynrelro. (elf_backend_want_dynrelro): Define. * elf32-hppa.c (elf32_hppa_adjust_dynamic_symbol) (elf32_hppa_size_dynamic_sections, elf32_hppa_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-i386.c (elf_i386_adjust_dynamic_symbol) (elf_i386_size_dynamic_sections, elf_i386_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-metag.c (elf_metag_adjust_dynamic_symbol) (elf_metag_size_dynamic_sections, elf_metag_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-microblaze.c (microblaze_elf_adjust_dynamic_symbol) (microblaze_elf_size_dynamic_sections) (microblaze_elf_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-nios2.c (nios2_elf32_finish_dynamic_symbol) (nios2_elf32_adjust_dynamic_symbol) (nios2_elf32_size_dynamic_sections) (elf_backend_want_dynrelro): As above. * elf32-or1k.c (or1k_elf_finish_dynamic_symbol) (or1k_elf_adjust_dynamic_symbol, or1k_elf_size_dynamic_sections) (elf_backend_want_dynrelro): As above. * elf32-ppc.c (ppc_elf_adjust_dynamic_symbol) (ppc_elf_size_dynamic_sections, ppc_elf_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-s390.c (elf_s390_adjust_dynamic_symbol) (elf_s390_size_dynamic_sections, elf_s390_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-tic6x.c (elf32_tic6x_adjust_dynamic_symbol) (elf32_tic6x_size_dynamic_sections) (elf32_tic6x_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf32-tilepro.c (tilepro_elf_adjust_dynamic_symbol) (tilepro_elf_size_dynamic_sections) (tilepro_elf_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf64-ppc.c (ppc64_elf_adjust_dynamic_symbol) (ppc64_elf_size_dynamic_sections, ppc64_elf_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf64-s390.c (elf_s390_adjust_dynamic_symbol) (elf_s390_size_dynamic_sections, elf_s390_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elf64-x86-64.c (elf_x86_64_adjust_dynamic_symbol) (elf_x86_64_size_dynamic_sections) (elf_x86_64_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elfnn-aarch64.c (elfNN_aarch64_adjust_dynamic_symbol) (elfNN_aarch64_size_dynamic_sections) (elfNN_aarch64_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elfnn-riscv.c (riscv_elf_adjust_dynamic_symbol) (riscv_elf_size_dynamic_sections, riscv_elf_finish_dynamic_symbol) (elf_backend_want_dynrelro): As above. * elfxx-mips.c (_bfd_mips_elf_adjust_dynamic_symbol) (_bfd_mips_elf_size_dynamic_sections) (_bfd_mips_vxworks_finish_dynamic_symbol): As above. * elfxx-sparc.c (_bfd_sparc_elf_adjust_dynamic_symbol) (_bfd_sparc_elf_size_dynamic_sections) (_bfd_sparc_elf_finish_dynamic_symbol): As above. * elfxx-tilegx.c (tilegx_elf_adjust_dynamic_symbol) (tilegx_elf_size_dynamic_sections) (tilegx_elf_finish_dynamic_symbol): As above. * elf32-mips.c (elf_backend_want_dynrelro): Define. * elf64-mips.c (elf_backend_want_dynrelro): Define. * elf32-sparc.c (elf_backend_want_dynrelro): Define. * elf64-sparc.c (elf_backend_want_dynrelro): Define. * elf32-tilegx.c (elf_backend_want_dynrelro): Define. * elf64-tilegx.c (elf_backend_want_dynrelro): Define. * elf32-microblaze.c (microblaze_elf_adjust_dynamic_symbol): Tidy. (microblaze_elf_size_dynamic_sections): Handle sdynbss. * elf32-nios2.c (nios2_elf32_size_dynamic_sections): Make use of linker shortcuts to dynamic sections rather than comparing names. Correctly set "got" flag. ld/ PR ld/20995 * testsuite/ld-arm/farcall-mixed-app-v5.d: Update to suit changed stub hash table traversal caused by section id increment. Accept the previous output too. * testsuite/ld-arm/farcall-mixed-app.d: Likewise. * testsuite/ld-arm/farcall-mixed-lib-v4t.d: Likewise. * testsuite/ld-arm/farcall-mixed-lib.d: Likewise. * testsuite/ld-elf/pr20995a.s, * testsuite/ld-elf/pr20995b.s, * testsuite/ld-elf/pr20995.r: New test. * testsuite/ld-elf/elf.exp: Run it.
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.