% cat a.c __attribute__((weak,tls_model("local-exec"))) extern __thread char tls; char *get() { return &tls; } % clang -target aarch64 -c a.c % readelf -r a.o Relocation section '.rela.text' at offset 0x158 contains 2 entries: Offset Info Type Symbol's Value Symbol's Name + Addend 0000000000000004 0000000500000225 R_AARCH64_TLSLE_ADD_TPREL_HI12 0000000000000000 tls + 0 0000000000000008 0000000500000227 R_AARCH64_TLSLE_ADD_TPREL_LO12_NC 0000000000000000 tls + 0 % ./ld-new a.o ./ld-new: warning: cannot find entry symbol _start; defaulting to 00000000004000b0 ./ld-new: BFD (GNU Binutils) 2.32.51.20190522 assertion fail ../../bfd/elfnn-aarch64.c:5059 [1] 153266 segmentation fault ./ld-new a.o static bfd_vma tpoff_base (struct bfd_link_info *info) { struct elf_link_hash_table *htab = elf_hash_table (info); /* If tls_sec is NULL, we should have signalled an error already. */ BFD_ASSERT (htab->tls_sec != NULL); bfd_vma base = align_power ((bfd_vma) TCB_SIZE, htab->tls_sec->alignment_power); return htab->tls_sec->vma - base; } BTW, the formula may be incorrect if p_vaddr%p_align != 0 (the offset should be chosen so that offset%p_align = p_vaddr%p_align, but that scenario may be unrealistic.
Confirmed, I'll take a look. Thanks for the report!
The master branch has been updated by Tamar Christina <tnfchris@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=652afeef247770b22c44ca292d1f4c65be40a696 commit 652afeef247770b22c44ca292d1f4c65be40a696 Author: Tamar Christina <tamar.christina@arm.com> Date: Thu Aug 22 11:35:35 2019 +0100 AArch64: Fix LD crash on weak and undefined TLS symbols. (PR/24602). This patch fixes a few linker crashes due to TLS code reaching an assert when it shouldn't. The first scenario is with weak TLS symbols that remain weak during linking. In this case the mid-end would not have seen a TLS symbol and so wouldn't have allocated the TLS section. We currently assert here and the linker crashes with a not very useful message. This patch changes this to return the value 0 for the TLS symbol in question emulating what lld and gold and other BFD targets do. However because weak TLS is implementation defined and we don't define any behavior for it I also emit a warning to the user to inform them of such. Secondly when a strong TLS reference is undefined. The linker crashes even after it correctly reported that there is an undefined reference. This changes it so that it gracefully exits and reports a useful error. bfd/ChangeLog: PR ld/24601 * elfnn-aarch64.c (aarch64_relocate): Handle weak TLS and undefined TLS. Also Pass input_bfd to _bfd_aarch64_elf_resolve_relocation. * elfxx-aarch64.c (_bfd_aarch64_elf_resolve_relocation): Use it. * elfxx-aarch64.h (_bfd_aarch64_elf_resolve_relocation): Emit warning for weak TLS. ld/ChangeLog: PR ld/24601 * testsuite/ld-aarch64/aarch64-elf.exp (undef-tls, weak-tls): New. * testsuite/ld-aarch64/undef-tls.d: New test. * testsuite/ld-aarch64/undef-tls.s: New test. * testsuite/ld-aarch64/weak-tls.d: New test. * testsuite/ld-aarch64/weak-tls.s: New test.
The binutils-2_32-branch branch has been updated by Tamar Christina <tnfchris@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=6795dba28d531a17a0800d532d555653415702bb commit 6795dba28d531a17a0800d532d555653415702bb Author: Tamar Christina <tamar.christina@arm.com> Date: Thu Aug 22 11:35:35 2019 +0100 AArch64: Fix LD crash on weak and undefined TLS symbols. (PR/24602). This patch fixes a few linker crashes due to TLS code reaching an assert when it shouldn't. The first scenario is with weak TLS symbols that remain weak during linking. In this case the mid-end would not have seen a TLS symbol and so wouldn't have allocated the TLS section. We currently assert here and the linker crashes with a not very useful message. This patch changes this to return the value 0 for the TLS symbol in question emulating what lld and gold and other BFD targets do. However because weak TLS is implementation defined and we don't define any behavior for it I also emit a warning to the user to inform them of such. Secondly when a strong TLS reference is undefined. The linker crashes even after it correctly reported that there is an undefined reference. This changes it so that it gracefully exits and reports a useful error. bfd/ChangeLog: PR ld/24601 * elfnn-aarch64.c (aarch64_relocate): Handle weak TLS and undefined TLS. Also Pass input_bfd to _bfd_aarch64_elf_resolve_relocation. * elfxx-aarch64.c (_bfd_aarch64_elf_resolve_relocation): Use it. * elfxx-aarch64.h (_bfd_aarch64_elf_resolve_relocation): Emit warning for weak TLS. ld/ChangeLog: PR ld/24601 * testsuite/ld-aarch64/aarch64-elf.exp (undef-tls, weak-tls): New. * testsuite/ld-aarch64/undef-tls.d: New test. * testsuite/ld-aarch64/undef-tls.s: New test. * testsuite/ld-aarch64/weak-tls.d: New test. * testsuite/ld-aarch64/weak-tls.s: New test. (cherry picked from commit 652afeef247770b22c44ca292d1f4c65be40a696)
Fixed and backported to 2.32 branch.