seen when building gmp 6.0.0a on ARM32 linux only, other architectures work fine: libtool: link: arm-linux-gnueabihf-gcc -std=gnu99 -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -O3 -Wl,-Bsymbolic-functions -Wl,-z -Wl,relro -o .libs/t-constants t-constants.o ./.libs/libtests.a /build/buildd/gmp-6.0.0+dfsg/build/.libs/libgmp.so ../.libs/libgmp.so /usr/bin/ld: copy reloc against protected `__gmp_binvert_limb_table' is invalid /usr/bin/ld: failed to set dynamic section sizes: Bad value collect2: error: ld returned 1 exit status Makefile:760: recipe for target 't-constants' failed likely exposed by the fixes for PR ld/pr15228, PR ld/pr17709
All ELF targets with copy relocation should set elf_backend_extern_protected_data to 1, like x86 in https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=031994d25c8c8dc392ceb43abc2dfd9a851bc384
Likely due to my PR 15228 fix. HJ's advice is only reasonable if you have glibc and gcc changes that a) make code generated for access to protected visibility variables in shared libraries effectively be the same as for default visibility variables, and b) you have glibc changes that ensure you keep the semantics of protected visibility variables. Otherwise all HJ's changes do is revert the PR 15228 fix, and you will silently generate buggy executables that have a copy of a protected variable in .dynbss that isn't used by the shared library defining that variable. ie. you've broken the semantics of protected variables. If either the executable or the shared library update the variable's value, then they see different values in a variable that has only one definition. I also think HJ's linker changes are unsafe since there is no attempt to detect shared libraries that are compiled without the as yet uncommitted gcc changes.
The master branch has been updated by Alan Modra <amodra@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=b84171287ffe60dd1e7c02262a0493862fa21a97 commit b84171287ffe60dd1e7c02262a0493862fa21a97 Author: Alan Modra <amodra@gmail.com> Date: Fri Mar 27 15:41:05 2015 +1030 Relax PR 15228 protected visibility restriction Allows .dynbss copy of shared library protected visibility variables if they are read-only. To recap: Copying a variable from a shared library into an executable's .dynbss is an old hack invented for non-PIC executables, to avoid the text relocations you'd otherwise need to access a shared library variable. This works with ELF shared libraries because global symbols can be overridden. The trouble is that protected visibility symbols can't be overridden. A shared library will continue to access it's own protected visibility variable while the executable accesses a copy. If either the shared library or the executable updates the value then the copy diverges from the original. This is wrong since there is only one definition of the variable in the application. So I made the linker report an error on attempting to copy protected visibility variables into .dynbss. However, you'll notice the above paragraph contains an "If". An application that does not modify the variable value remains correct even though two copies of the variable exist. The linker can detect this situation if the variable was defined in a read-only section. PR ld/15228 PR ld/18167 * elflink.c (elf_merge_st_other): Add "sec" parameter. Don't set protected_def when symbol section is read-only. Adjust all calls. * elf-bfd.h (struct elf_link_hash_entry): Update protected_def comment.
Matthias, please check that the patch I've just committed fixes the problem in gmp.
yes, the patch fixes the gmp build issue on ARM32.
The binutils-2_25-branch branch has been updated by Alan Modra <amodra@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=12aca65e0f9148bf136a9f4cfc2187aa485a143a commit 12aca65e0f9148bf136a9f4cfc2187aa485a143a Author: Alan Modra <amodra@gmail.com> Date: Fri Mar 27 15:41:05 2015 +1030 Relax PR 15228 protected visibility restriction Allows .dynbss copy of shared library protected visibility variables if they are read-only. To recap: Copying a variable from a shared library into an executable's .dynbss is an old hack invented for non-PIC executables, to avoid the text relocations you'd otherwise need to access a shared library variable. This works with ELF shared libraries because global symbols can be overridden. The trouble is that protected visibility symbols can't be overridden. A shared library will continue to access it's own protected visibility variable while the executable accesses a copy. If either the shared library or the executable updates the value then the copy diverges from the original. This is wrong since there is only one definition of the variable in the application. So I made the linker report an error on attempting to copy protected visibility variables into .dynbss. However, you'll notice the above paragraph contains an "If". An application that does not modify the variable value remains correct even though two copies of the variable exist. The linker can detect this situation if the variable was defined in a read-only section. PR ld/15228 PR ld/18167 * elflink.c (elf_merge_st_other): Add "sec" parameter. Don't set protected_def when symbol section is read-only. Adjust all calls. * elf-bfd.h (struct elf_link_hash_entry): Update protected_def comment.
Fixed