From 7e05773767820b441b23a16628b55c98cb1aef46 Mon Sep 17 00:00:00 2001 From: Siddhesh Poyarekar Date: Tue, 19 May 2020 11:07:52 +0100 Subject: [PATCH] [PATCH v3] aarch64: Emit jump slot for conditional branch to undefined symbols The linker silently writes out a conditional branch to 0 if the target symbol in R_AARCH64_CONDBR19 or R_AARCH64_TSTBR14 relocations is undefined. Emit a PLT instead so that behaviour is the same for these relocations as the llvm linker. The special behaviour for undefined weak symbols, where conditional branches to such symbols result in a branch unto themselves, has been retained. This is because the weak-undefined.s test explicitly checks for that, leading me to conclude that it's expected behaviour. bfd * elfnn-aarch64.c (elfNN_aarch64_final_link_relocate): Club BFD_RELOC_AARCH64_BRANCH19 and BFD_RELOC_AARCH64_TSTBR14 cases with BFD_RELOC_AARCH64_JUMP26. (elfNN_aarch64_check_relocs): Likewise. ld * testsuite/ld-aarch64/aarch64-elf.exp: New test emit-relocs-560. * testsuite/ld-aarch64/emit-relocs-560.d: New file. * testsuite/ld-aarch64/emit-relocs-560.s: New file. --- bfd/ChangeLog | 7 +++++++ bfd/elfnn-aarch64.c | 22 ++++++++++++++++++---- ld/ChangeLog | 7 +++++++ ld/testsuite/ld-aarch64/aarch64-elf.exp | 1 + ld/testsuite/ld-aarch64/emit-relocs-560.d | 8 ++++++++ ld/testsuite/ld-aarch64/emit-relocs-560.s | 3 +++ 6 files changed, 44 insertions(+), 4 deletions(-) create mode 100644 ld/testsuite/ld-aarch64/emit-relocs-560.d create mode 100644 ld/testsuite/ld-aarch64/emit-relocs-560.s diff --git a/bfd/ChangeLog b/bfd/ChangeLog index d989223572..c10c1e93c9 100644 --- a/bfd/ChangeLog +++ b/bfd/ChangeLog @@ -1,3 +1,10 @@ +2020-05-19 Siddhesh Poyarekar + + * elfnn-aarch64.c (elfNN_aarch64_final_link_relocate): Club + BFD_RELOC_AARCH64_BRANCH19 and BFD_RELOC_AARCH64_TSTBR14 + cases with BFD_RELOC_AARCH64_JUMP26. + (elfNN_aarch64_check_relocs): Likewise. + 2020-05-19 Alan Modra * aix5ppc-core.c (xcoff64_core_file_matches_executable_p): Use diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c index 4bb5707d2f..02df893fcd 100644 --- a/bfd/elfnn-aarch64.c +++ b/bfd/elfnn-aarch64.c @@ -5494,6 +5494,7 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto, bfd_vma orig_value = value; bfd_boolean resolved_to_zero; bfd_boolean abs_symbol_p; + bfd_boolean via_plt_p; globals = elf_aarch64_hash_table (info); @@ -5515,6 +5516,8 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto, : bfd_is_und_section (sym_sec)); abs_symbol_p = h != NULL && bfd_is_abs_symbol (&h->root); + via_plt_p = (globals->root.splt != NULL && h != NULL + && h->plt.offset != (bfd_vma) - 1); /* Since STT_GNU_IFUNC symbol must go through PLT, we handle it here if it is defined in a non-shared object. */ @@ -5850,12 +5853,23 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto, value += signed_addend; break; + case BFD_RELOC_AARCH64_BRANCH19: + case BFD_RELOC_AARCH64_TSTBR14: + /* A conditional branch to an undefined weak symbol is converted to a + branch to itself. */ + if (weak_undef_p && !via_plt_p) + { + value = _bfd_aarch64_elf_resolve_relocation (input_bfd, bfd_r_type, + place, value, + signed_addend, + weak_undef_p); + break; + } + /* Fall through. */ case BFD_RELOC_AARCH64_CALL26: case BFD_RELOC_AARCH64_JUMP26: { asection *splt = globals->root.splt; - bfd_boolean via_plt_p = - splt != NULL && h != NULL && h->plt.offset != (bfd_vma) - 1; /* A call to an undefined weak symbol is converted to a jump to the next instruction unless a PLT entry will be created. @@ -5943,7 +5957,6 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto, case BFD_RELOC_AARCH64_32: #endif case BFD_RELOC_AARCH64_ADD_LO12: - case BFD_RELOC_AARCH64_BRANCH19: case BFD_RELOC_AARCH64_LDST128_LO12: case BFD_RELOC_AARCH64_LDST16_LO12: case BFD_RELOC_AARCH64_LDST32_LO12: @@ -5959,7 +5972,6 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto, case BFD_RELOC_AARCH64_MOVW_G2_NC: case BFD_RELOC_AARCH64_MOVW_G2_S: case BFD_RELOC_AARCH64_MOVW_G3: - case BFD_RELOC_AARCH64_TSTBR14: value = _bfd_aarch64_elf_resolve_relocation (input_bfd, bfd_r_type, place, value, signed_addend, weak_undef_p); @@ -8022,6 +8034,8 @@ elfNN_aarch64_check_relocs (bfd *abfd, struct bfd_link_info *info, break; } + case BFD_RELOC_AARCH64_BRANCH19: + case BFD_RELOC_AARCH64_TSTBR14: case BFD_RELOC_AARCH64_CALL26: case BFD_RELOC_AARCH64_JUMP26: /* If this is a local symbol then we resolve it diff --git a/ld/ChangeLog b/ld/ChangeLog index 730517124e..cf566b3255 100644 --- a/ld/ChangeLog +++ b/ld/ChangeLog @@ -1,3 +1,10 @@ +2020-05-19 Siddhesh Poyarekar + + * testsuite/ld-aarch64/aarch64-elf.exp: New test + emit-relocs-560. + * testsuite/ld-aarch64/emit-relocs-560.d: New file. + * testsuite/ld-aarch64/emit-relocs-560.s: New file. + 2020-05-19 Alan Modra * emultempl/beos.em (sort_by_file_name): Use bfd_get_filename diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp index 297a3e96db..4c44fa1642 100644 --- a/ld/testsuite/ld-aarch64/aarch64-elf.exp +++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp @@ -236,6 +236,7 @@ run_dump_test_lp64 "emit-relocs-557" run_dump_test_lp64 "emit-relocs-558" run_dump_test_lp64 "emit-relocs-558-overflow" run_dump_test_lp64 "emit-relocs-559" +run_dump_test_lp64 "emit-relocs-560" run_dump_test "reloc-overflow-bad" diff --git a/ld/testsuite/ld-aarch64/emit-relocs-560.d b/ld/testsuite/ld-aarch64/emit-relocs-560.d new file mode 100644 index 0000000000..153532457b --- /dev/null +++ b/ld/testsuite/ld-aarch64/emit-relocs-560.d @@ -0,0 +1,8 @@ +#source: emit-relocs-560.s +#ld: -shared +#readelf: -r + +Relocation section '.rela.plt' at offset 0x[0-9a-f]+ contains 2 entries: + Offset Info Type Sym. Value Sym. Name \+ Addend +[0-9a-f]+ 000100000402 R_AARCH64_JUMP_SL 0000000000000000 baz \+ 0 +[0-9a-f]+ 000200000402 R_AARCH64_JUMP_SL 0000000000000000 bar \+ 0 diff --git a/ld/testsuite/ld-aarch64/emit-relocs-560.s b/ld/testsuite/ld-aarch64/emit-relocs-560.s new file mode 100644 index 0000000000..9529e8fd5e --- /dev/null +++ b/ld/testsuite/ld-aarch64/emit-relocs-560.s @@ -0,0 +1,3 @@ +foo: + tbz x0, 1, bar + cbnz x1, baz -- 2.34.1