* options.h (retpolineplt): New -z option to use retpoline PLT. * options.cc (General_options::finalize): Check if both retpolineplt and bndplt are turned on. * x86_64.cc (Output_data_plt_x86_64_retpoline): New class. (Target_x86_64<64>::do_make_data_plt): Create retpoline PLT when the option is used. * testsuite/Makefile.am (retpoline_plt_1.sh): New test. * testsuite/Makefile.in: Regenerate. * testsuite/retpoline_plt_1.sh: New test script. * testsuite/retpoline_plt_1.s: New test source. diff --git a/gold/options.cc b/gold/options.cc index f511ba1e79..a33fa31420 100644 --- a/gold/options.cc +++ b/gold/options.cc @@ -1367,6 +1367,11 @@ General_options::finalize() if (this->user_set_rosegment_gap()) this->set_rosegment(true); + if (this->bndplt() && this->retpolineplt()) + { + gold_fatal(_("-z,bndplt and -z,retpolineplt are mutually exclusive")); + } + // FIXME: we can/should be doing a lot more sanity checking here. } diff --git a/gold/options.h b/gold/options.h index d5b8fe43ac..035e48110f 100644 --- a/gold/options.h +++ b/gold/options.h @@ -1426,6 +1426,9 @@ class General_options DEFINE_bool(bndplt, options::DASH_Z, '\0', false, N_("(x86-64 only) Generate a BND PLT for Intel MPX"), N_("Generate a regular PLT")); + DEFINE_bool(retpolineplt, options::DASH_Z, '\0', false, + N_("(x86-64 only) Generate a retpoline PLT"), + N_("Generate a regular PLT")); DEFINE_bool(combreloc, options::DASH_Z, '\0', true, N_("Sort dynamic relocs"), N_("Do not sort dynamic relocs")); diff --git a/gold/testsuite/Makefile.am b/gold/testsuite/Makefile.am index 16cae8004c..8c04091c8d 100644 --- a/gold/testsuite/Makefile.am +++ b/gold/testsuite/Makefile.am @@ -3219,6 +3219,15 @@ split_x86_64_r.stdout: split_x86_64_1.o split_x86_64_n.o ../ld-new MOSTLYCLEANFILES += split_x86_64_1 split_x86_64_2 split_x86_64_3 \ split_x86_64_4 split_x86_64_r +check_SCRIPTS += retpoline_plt_1.sh +check_DATA += retpoline_plt_1.stdout +retpoline_plt_1.o: retpoline_plt_1.s + $(TEST_AS) --64 -o $@ $< +retpoline_plt_1.so: retpoline_plt_1.o ../ld-new + ../ld-new -shared -z retpolineplt retpoline_plt_1.o -o $@ +retpoline_plt_1.stdout: retpoline_plt_1.so + $(TEST_OBJDUMP) -dw $< > $@ + check_SCRIPTS += bnd_plt_1.sh check_DATA += bnd_plt_1.stdout bnd_plt_1.o: bnd_plt_1.s diff --git a/gold/testsuite/retpoline_plt_1.s b/gold/testsuite/retpoline_plt_1.s index e69de29bb2..0aa1be0228 100644 --- a/gold/testsuite/retpoline_plt_1.s +++ b/gold/testsuite/retpoline_plt_1.s @@ -0,0 +1,4 @@ + .text + .globl _start +_start: + call foo1@plt diff --git a/gold/testsuite/retpoline_plt_1.sh b/gold/testsuite/retpoline_plt_1.sh index e69de29bb2..28be2034cb 100755 --- a/gold/testsuite/retpoline_plt_1.sh +++ b/gold/testsuite/retpoline_plt_1.sh @@ -0,0 +1,33 @@ +#!/bin/sh + +# retpoline_plt_1.sh -- test -z retpolineplt for x86_64 + +# Copyright (C) 2016-2017 Free Software Foundation, Inc. +# Written by Sriraman Tallam . + +# This file is part of gold. + +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. + +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. + +# You should have received a copy of the GNU General Public License +# along with this program; if not, write to the Free Software +# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, +# MA 02110-1301, USA. + +noindirectjump() +{ + if egrep "$1" "$2" >/dev/null 2>&1; then + echo 1>&2 "Found indirect jump '$1' in $2" + exit 1 + fi +} + +noindirectjump 'jmpq[ ]*\*0x[0-9a-f]*\(%rip\)' retpoline_plt_1.stdout diff --git a/gold/x86_64.cc b/gold/x86_64.cc index a8140602b0..2eefe5d93e 100644 --- a/gold/x86_64.cc +++ b/gold/x86_64.cc @@ -542,6 +542,84 @@ class Output_data_plt_x86_64_bnd : public Output_data_plt_x86_64<64> static const unsigned char plt_eh_frame_fde[plt_eh_frame_fde_size]; }; +template +class Output_data_plt_x86_64_retpoline : public Output_data_plt_x86_64 +{ + public: + Output_data_plt_x86_64_retpoline(Layout* layout, + Output_data_got<64, false>* got, + Output_data_got_plt_x86_64* got_plt, + Output_data_space* got_irelative) + : Output_data_plt_x86_64(layout, plt_entry_size, + got, got_plt, got_irelative) + { } + + Output_data_plt_x86_64_retpoline(Layout* layout, + Output_data_got<64, false>* got, + Output_data_got_plt_x86_64* got_plt, + Output_data_space* got_irelative, + unsigned int plt_count) + : Output_data_plt_x86_64(layout, plt_entry_size, + got, got_plt, got_irelative, + plt_count) + { } + + protected: + virtual unsigned int + do_get_plt_entry_size() const + { return plt_entry_size; } + + virtual void + do_add_eh_frame(Layout* layout) + { + layout->add_eh_frame_for_plt(this, + this->plt_eh_frame_cie, + this->plt_eh_frame_cie_size, + plt_eh_frame_fde, + plt_eh_frame_fde_size); + } + + virtual void + do_fill_first_plt_entry(unsigned char* pov, + typename elfcpp::Elf_types::Elf_Addr got_addr, + typename elfcpp::Elf_types::Elf_Addr plt_addr); + + virtual unsigned int + do_fill_plt_entry(unsigned char* pov, + typename elfcpp::Elf_types::Elf_Addr got_address, + typename elfcpp::Elf_types::Elf_Addr plt_address, + unsigned int got_offset, + unsigned int plt_offset, + unsigned int plt_index); + + virtual void + do_fill_tlsdesc_entry(unsigned char* pov, + typename elfcpp::Elf_types::Elf_Addr got_address, + typename elfcpp::Elf_types::Elf_Addr plt_address, + typename elfcpp::Elf_types::Elf_Addr got_base, + unsigned int tlsdesc_got_offset, + unsigned int plt_offset); + + private: + // The size of an entry in the PLT. + static const int plt_entry_size = 32; + + // The first entry in the PLT. + // From the AMD64 ABI: "Unlike Intel386 ABI, this ABI uses the same + // procedure linkage table for both programs and shared objects." + static const unsigned char first_plt_entry[plt_entry_size]; + + // Other entries in the PLT for an executable. + static const unsigned char plt_entry[plt_entry_size]; + + // The reserved TLSDESC entry in the PLT for an executable. + static const unsigned char tlsdesc_plt_entry[plt_entry_size]; + + // The .eh_frame unwind information for the PLT. + static const int plt_eh_frame_fde_size = 32; + static const unsigned char plt_eh_frame_fde[plt_eh_frame_fde_size]; +}; + template class Lazy_view { @@ -1814,6 +1892,129 @@ Output_data_plt_x86_64_standard::do_fill_tlsdesc_entry( + 12))); } +// The first entry in the PLT for an executable. + +template +const unsigned char +Output_data_plt_x86_64_retpoline::first_plt_entry[plt_entry_size] = +{ + // Retpoline first PLT entry code sequence. + 0xff, 0x35, // pushq contents of memory address + 0, 0, 0, 0, // replaced with address of .got + 8 + 0x4c, 0x8b, 0x1d, // mov GOT(%rip), %r11 + 0, 0, 0, 0, + 0xe8, 0x04, 0, 0, 0, // callq next + 0xf3, 0x90, // loop: pause + 0xeb, 0xfc, // jmp loop + 0x4c, 0x89, 0x1c, 0x24, // next: mov r11, %(rsp) + 0xc3, // ret + 0xcc, 0xcc, 0xcc, 0xcc, 0xcc // 5 extra bytes +}; + +template +void +Output_data_plt_x86_64_retpoline::do_fill_first_plt_entry( + unsigned char* pov, + typename elfcpp::Elf_types::Elf_Addr got_address, + typename elfcpp::Elf_types::Elf_Addr plt_address) +{ + memcpy(pov, first_plt_entry, plt_entry_size); + // We do a jmp relative to the PC at the end of this instruction. + elfcpp::Swap_unaligned<32, false>::writeval(pov + 2, + (got_address + 8 + - (plt_address + 6))); + elfcpp::Swap<32, false>::writeval(pov + 9, + (got_address + 16 + - (plt_address + 13))); +} + +// The retpoline entries in the PLT for an executable. + +template +const unsigned char +Output_data_plt_x86_64_retpoline::plt_entry[plt_entry_size] = +{ + // Retpoline PLT code sequence. + 0x4c, 0x8b, 0x1d, 0, 0, 0, 0, // mov sym@GOTPLT(%rip), r11 + 0xe8, 0x04, 0, 0, 0, // callq next + 0xf3, 0x90, // loop: pause + 0xeb, 0xfc, // jmp loop + 0x4c, 0x89, 0x1c, 0x24, // next: mov r11, %(rsp) + 0xc3, // ret + 0x68, // pushq immediate + 0, 0, 0, 0, // replaced with offset into relocation table + 0xe9, // jmpq relative + 0, 0, 0, 0, // replaced with offset to start of .plt + 0xcc // extra byte +}; + +template +unsigned int +Output_data_plt_x86_64_retpoline::do_fill_plt_entry( + unsigned char* pov, + typename elfcpp::Elf_types::Elf_Addr got_address, + typename elfcpp::Elf_types::Elf_Addr plt_address, + unsigned int got_offset, + unsigned int plt_offset, + unsigned int plt_index) +{ + // Check PC-relative offset overflow in PLT entry. + uint64_t plt_got_pcrel_offset = (got_address + got_offset + - (plt_address + plt_offset + 7)); + if (Bits<32>::has_overflow(plt_got_pcrel_offset)) + gold_error(_("PC-relative offset overflow in PLT entry %d"), + plt_index + 1); + + memcpy(pov, plt_entry, plt_entry_size); + elfcpp::Swap_unaligned<32, false>::writeval(pov + 3, + plt_got_pcrel_offset); + + elfcpp::Swap_unaligned<32, false>::writeval(pov + 22, plt_index); + elfcpp::Swap<32, false>::writeval(pov + 27, + - (plt_offset + plt_entry_size - 1)); + + return 21; + +} + +// The reserved TLSDESC entry in the PLT for an executable. + +template +const unsigned char +Output_data_plt_x86_64_retpoline::tlsdesc_plt_entry[plt_entry_size] = +{ + // From Alexandre Oliva, "Thread-Local Storage Descriptors for IA32 + // and AMD64/EM64T", Version 0.9.4 (2005-10-10). + 0xff, 0x35, // pushq x(%rip) + 0, 0, 0, 0, // replaced with address of linkmap GOT entry (at PLTGOT + 8) + 0xff, 0x25, // jmpq *y(%rip) + 0, 0, 0, 0, // replaced with offset of reserved TLSDESC_GOT entry + 0x0f, 0x1f, // nop + 0x40, 0 +}; + +template +void +Output_data_plt_x86_64_retpoline::do_fill_tlsdesc_entry( + unsigned char* pov, + typename elfcpp::Elf_types::Elf_Addr got_address, + typename elfcpp::Elf_types::Elf_Addr plt_address, + typename elfcpp::Elf_types::Elf_Addr got_base, + unsigned int tlsdesc_got_offset, + unsigned int plt_offset) +{ + memcpy(pov, tlsdesc_plt_entry, plt_entry_size); + elfcpp::Swap_unaligned<32, false>::writeval(pov + 2, + (got_address + 8 + - (plt_address + plt_offset + + 6))); + elfcpp::Swap_unaligned<32, false>::writeval(pov + 8, + (got_base + + tlsdesc_got_offset + - (plt_address + plt_offset + + 12))); +} + // Return the APLT address to use for a global symbol (for -z bndplt). uint64_t @@ -2036,6 +2237,34 @@ Output_data_plt_x86_64_standard::plt_eh_frame_fde[plt_eh_frame_fde_size] = elfcpp::DW_CFA_nop }; +template +const unsigned char +Output_data_plt_x86_64_retpoline::plt_eh_frame_fde[plt_eh_frame_fde_size] = +{ + 0, 0, 0, 0, // Replaced with offset to .plt. + 0, 0, 0, 0, // Replaced with size of .plt. + 0, // Augmentation size. + elfcpp::DW_CFA_def_cfa_offset, 16, // DW_CFA_def_cfa_offset: 16. + elfcpp::DW_CFA_advance_loc + 6, // Advance 6 to __PLT__ + 6. + elfcpp::DW_CFA_def_cfa_offset, 24, // DW_CFA_def_cfa_offset: 24. + elfcpp::DW_CFA_advance_loc + 10, // Advance 10 to __PLT__ + 16. + elfcpp::DW_CFA_def_cfa_expression, // DW_CFA_def_cfa_expression. + 11, // Block length. + elfcpp::DW_OP_breg7, 8, // Push %rsp + 8. + elfcpp::DW_OP_breg16, 0, // Push %rip. + elfcpp::DW_OP_lit15, // Push 0xf. + elfcpp::DW_OP_and, // & (%rip & 0xf). + elfcpp::DW_OP_lit11, // Push 0xb. + elfcpp::DW_OP_ge, // >= ((%rip & 0xf) >= 0xb) + elfcpp::DW_OP_lit3, // Push 3. + elfcpp::DW_OP_shl, // << (((%rip & 0xf) >= 0xb) << 3) + elfcpp::DW_OP_plus, // + ((((%rip&0xf)>=0xb)<<3)+%rsp+8 + elfcpp::DW_CFA_nop, // Align to 32 bytes. + elfcpp::DW_CFA_nop, + elfcpp::DW_CFA_nop, + elfcpp::DW_CFA_nop +}; + // The .eh_frame unwind information for the BND PLT. const unsigned char Output_data_plt_x86_64_bnd::plt_eh_frame_fde[plt_eh_frame_fde_size] = @@ -2287,6 +2516,9 @@ Target_x86_64<64>::do_make_data_plt(Layout* layout, if (parameters->options().bndplt()) return new Output_data_plt_x86_64_bnd(layout, got, got_plt, got_irelative); + else if (parameters->options().retpolineplt()) + return new Output_data_plt_x86_64_retpoline<64>(layout, got, got_plt, + got_irelative); else return new Output_data_plt_x86_64_standard<64>(layout, got, got_plt, got_irelative); @@ -2316,6 +2548,9 @@ Target_x86_64<64>::do_make_data_plt(Layout* layout, if (parameters->options().bndplt()) return new Output_data_plt_x86_64_bnd(layout, got, got_plt, got_irelative, plt_count); + else if (parameters->options().retpolineplt()) + return new Output_data_plt_x86_64_retpoline<64>(layout, got, got_plt, + got_irelative, plt_count); else return new Output_data_plt_x86_64_standard<64>(layout, got, got_plt, got_irelative,