Lazy R_*_TLSDESC resolving has several problems (e.g. data race) and glibc has eagerly resolved R_*_TLSDESC for all(?) supported ports: arm (PR18572)/aarch64 (PR18034)/x86 (PR27137). It is also odd to overload .rela.plt (PLT) with TLSDESC which have quite different semantics. Currently GNU ld still uses .rela.plt, but it probably makes sense to switch to .rela.dyn instead. % cat x.c extern __thread int tlsdesc; int get(void) { return tlsdesc; } % gcc -fpic -mtls-dialect=gnu2 -shared x.c && readelf -r a.out ... Relocation section '.rela.plt' at offset 0x440 contains 1 entry: Offset Info Type Sym. Value Sym. Name + Addend 000000004018 000200000024 R_X86_64_TLSDESC 0000000000000000 tlsdesc + 0 % aarch64-linux-gnu-gcc -fpic -shared x.c && readelf -r a.out ... Relocation section '.rela.plt' at offset 0x400 contains 3 entries: Offset Info Type Sym. Value Sym. Name + Addend 000000011000 000300000402 R_AARCH64_JUMP_SL 0000000000000000 __cxa_finalize + 0 000000011008 000700000402 R_AARCH64_JUMP_SL 0000000000000000 __gmon_start__ + 0 000000011010 000400000407 R_AARCH64_TLSDESC 0000000000000000 tlsdesc + 0 % arm-linux-gnueabi-gcc -fpic -mtls-dialect=gnu2 -fuse-ld=bfd -shared x.c && readelf -r a.out ... Relocation section '.rel.plt' at offset 0x264 contains 3 entries: Offset Info Type Sym.Value Sym. Name 0001100c 00000316 R_ARM_JUMP_SLOT 00000000 __cxa_finalize 00011010 00000716 R_ARM_JUMP_SLOT 00000000 __gmon_start__ 00011014 0000040d R_ARM_TLS_DESC 00000000 tlsdesc
Created attachment 16281 [details] A patch I am testing this patch with GCC configured with --with-tls=gnu2.
The master branch has been updated by H.J. Lu <hjl@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=d5faa503bbd97015f7c9685322ace81211f5eb04 commit d5faa503bbd97015f7c9685322ace81211f5eb04 Author: H.J. Lu <hjl.tools@gmail.com> Date: Sun Aug 24 14:43:44 2025 -0700 x86: Don't put R_386_TLS_DESC/R_X86_64_TLSDESC in .rel.plt/.rela.plt Since lazy tlsdesc relocation has data races: https://sourceware.org/bugzilla/show_bug.cgi?id=27137 put R_386_TLS_DESC and R_X86_64_TLSDESC relocation in .rela.tls/.rel.tls section, instead of .rel.plt/.rela.plt section. Tested with glibc/i686 and glibc/x86-64 compiled with -mtls-dialect=gnu2 as well as GCC 16 configured with --with-tls=gnu2. bfd/ PR ld/28387 * elf32-i386.c (elf_i386_relocate_section): Put R_386_TLS_DESC in rel_tls_desc instead of elf.srelplt. * elf64-x86-64.c (elf_x86_64_relocate_section): Put R_X86_64_TLSDESC in rel_tls_desc instead of elf.srelplt. * elfxx-x86.c (elf_x86_allocate_dynrelocs): Use rel_tls_desc, instead of elf.srelplt, for GOT_TLS_GDESC_P. (_bfd_elf_x86_get_reloc_section): New function. (_bfd_x86_elf_late_size_sections): Use rel_tls_desc, instead of elf.srelplt, for GOT_TLS_GDESC_P. Remove next_tls_desc_index. (_bfd_x86_elf_link_setup_gnu_properties): Allocate .rela.tls/.rel.tls section for rel_tls_desc. * elfxx-x86.h (elf_x86_link_hash_table): Add rel_tls_desc. Remove next_tls_desc_index. (_bfd_elf_x86_get_reloc_section): New. (elf_backend_get_reloc_section): Likewise. ld/ PR ld/28387 * emulparams/elf32_x86_64.sh (OTHER_GOT_RELOC_SECTIONS): New. * emulparams/elf_i386.sh (OTHER_GOT_RELOC_SECTIONS): Likewise. * emulparams/elf_x86_64.sh (OTHER_GOT_RELOC_SECTIONS): Likewise. * testsuite/ld-i386/i386.exp: Run pr28387. * testsuite/ld-i386/pr17057.d: Adjusted * testsuite/ld-i386/tlsdesc.rd: Likewise. * testsuite/ld-i386/tlsdesc2.d: Likewise. * testsuite/ld-i386/tlsgdesc.rd: Likewise. * testsuite/ld-x86-64/tlsdesc.pd: Likewise. * testsuite/ld-x86-64/tlsdesc.rd: Likewise. * testsuite/ld-x86-64/tlsdesc2.d: Likewise. * testsuite/ld-x86-64/tlsgdesc.rd: Likewise. * testsuite/ld-i386/pr28387.d: New file. * testsuite/ld-i386/pr28387.s: Likewise. * testsuite/ld-x86-64/pr28387-x32.d: Likewise. * testsuite/ld-x86-64/pr28387.d: Likewise. * testsuite/ld-x86-64/pr28387.s: Likewise. * testsuite/ld-x86-64/x86-64.exp: Run pr28387 and pr28387-x32. Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Fixed for x86 so far.