| // ehframe.cc -- handle exception frame sections for gold |
| |
| // Copyright (C) 2006-2021 Free Software Foundation, Inc. |
| // Written by Ian Lance Taylor <iant@google.com>. |
| |
| // 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. |
| |
| #include "gold.h" |
| |
| #include <cstring> |
| #include <algorithm> |
| |
| #include "elfcpp.h" |
| #include "dwarf.h" |
| #include "symtab.h" |
| #include "reloc.h" |
| #include "ehframe.h" |
| |
| namespace gold |
| { |
| |
| // This file handles generation of the exception frame header that |
| // gcc's runtime support libraries use to find unwind information at |
| // runtime. This file also handles discarding duplicate exception |
| // frame information. |
| |
| // The exception frame header starts with four bytes: |
| |
| // 0: The version number, currently 1. |
| |
| // 1: The encoding of the pointer to the exception frames. This can |
| // be any DWARF unwind encoding (DW_EH_PE_*). It is normally a 4 |
| // byte PC relative offset (DW_EH_PE_pcrel | DW_EH_PE_sdata4). |
| |
| // 2: The encoding of the count of the number of FDE pointers in the |
| // lookup table. This can be any DWARF unwind encoding, and in |
| // particular can be DW_EH_PE_omit if the count is omitted. It is |
| // normally a 4 byte unsigned count (DW_EH_PE_udata4). |
| |
| // 3: The encoding of the lookup table entries. Currently gcc's |
| // libraries will only support DW_EH_PE_datarel | DW_EH_PE_sdata4, |
| // which means that the values are 4 byte offsets from the start of |
| // the table. |
| |
| // The exception frame header is followed by a pointer to the contents |
| // of the exception frame section (.eh_frame). This pointer is |
| // encoded as specified in the byte at offset 1 of the header (i.e., |
| // it is normally a 4 byte PC relative offset). |
| |
| // If there is a lookup table, this is followed by the count of the |
| // number of FDE pointers, encoded as specified in the byte at offset |
| // 2 of the header (i.e., normally a 4 byte unsigned integer). |
| |
| // This is followed by the table, which should start at an 4-byte |
| // aligned address in memory. Each entry in the table is 8 bytes. |
| // Each entry represents an FDE. The first four bytes of each entry |
| // are an offset to the starting PC for the FDE. The last four bytes |
| // of each entry are an offset to the FDE data. The offsets are from |
| // the start of the exception frame header information. The entries |
| // are in sorted order by starting PC. |
| |
| const int eh_frame_hdr_size = 4; |
| |
| // Construct the exception frame header. |
| |
| Eh_frame_hdr::Eh_frame_hdr(Output_section* eh_frame_section, |
| const Eh_frame* eh_frame_data) |
| : Output_section_data(4), |
| eh_frame_section_(eh_frame_section), |
| eh_frame_data_(eh_frame_data), |
| fde_offsets_(), |
| any_unrecognized_eh_frame_sections_(false) |
| { |
| } |
| |
| // Set the size of the exception frame header. |
| |
| void |
| Eh_frame_hdr::set_final_data_size() |
| { |
| unsigned int data_size = eh_frame_hdr_size + 4; |
| if (!this->any_unrecognized_eh_frame_sections_) |
| { |
| unsigned int fde_count = this->eh_frame_data_->fde_count(); |
| if (fde_count != 0) |
| data_size += 4 + 8 * fde_count; |
| this->fde_offsets_.reserve(fde_count); |
| } |
| this->set_data_size(data_size); |
| } |
| |
| // Write the data to the file. |
| |
| void |
| Eh_frame_hdr::do_write(Output_file* of) |
| { |
| switch (parameters->size_and_endianness()) |
| { |
| #ifdef HAVE_TARGET_32_LITTLE |
| case Parameters::TARGET_32_LITTLE: |
| this->do_sized_write<32, false>(of); |
| break; |
| #endif |
| #ifdef HAVE_TARGET_32_BIG |
| case Parameters::TARGET_32_BIG: |
| this->do_sized_write<32, true>(of); |
| break; |
| #endif |
| #ifdef HAVE_TARGET_64_LITTLE |
| case Parameters::TARGET_64_LITTLE: |
| this->do_sized_write<64, false>(of); |
| break; |
| #endif |
| #ifdef HAVE_TARGET_64_BIG |
| case Parameters::TARGET_64_BIG: |
| this->do_sized_write<64, true>(of); |
| break; |
| #endif |
| default: |
| gold_unreachable(); |
| } |
| } |
| |
| // Write the data to the file with the right endianness. |
| |
| template<int size, bool big_endian> |
| void |
| Eh_frame_hdr::do_sized_write(Output_file* of) |
| { |
| const off_t off = this->offset(); |
| const off_t oview_size = this->data_size(); |
| unsigned char* const oview = of->get_output_view(off, oview_size); |
| |
| // Version number. |
| oview[0] = 1; |
| |
| // Write out a 4 byte PC relative offset to the address of the |
| // .eh_frame section. |
| oview[1] = elfcpp::DW_EH_PE_pcrel | elfcpp::DW_EH_PE_sdata4; |
| uint64_t eh_frame_address = this->eh_frame_section_->address(); |
| uint64_t eh_frame_hdr_address = this->address(); |
| uint64_t eh_frame_offset = (eh_frame_address - |
| (eh_frame_hdr_address + 4)); |
| elfcpp::Swap<32, big_endian>::writeval(oview + 4, eh_frame_offset); |
| |
| if (this->any_unrecognized_eh_frame_sections_ |
| || this->fde_offsets_.empty()) |
| { |
| // There are no FDEs, or we didn't recognize the format of the |
| // some of the .eh_frame sections, so we can't write out the |
| // sorted table. |
| oview[2] = elfcpp::DW_EH_PE_omit; |
| oview[3] = elfcpp::DW_EH_PE_omit; |
| |
| gold_assert(oview_size == 8); |
| } |
| else |
| { |
| oview[2] = elfcpp::DW_EH_PE_udata4; |
| oview[3] = elfcpp::DW_EH_PE_datarel | elfcpp::DW_EH_PE_sdata4; |
| |
| elfcpp::Swap<32, big_endian>::writeval(oview + 8, |
| this->fde_offsets_.size()); |
| |
| // We have the offsets of the FDEs in the .eh_frame section. We |
| // couldn't easily get the PC values before, as they depend on |
| // relocations which are, of course, target specific. This code |
| // is run after all those relocations have been applied to the |
| // output file. Here we read the output file again to find the |
| // PC values. Then we sort the list and write it out. |
| |
| Fde_addresses<size> fde_addresses(this->fde_offsets_.size()); |
| this->get_fde_addresses<size, big_endian>(of, &this->fde_offsets_, |
| &fde_addresses); |
| |
| std::sort(fde_addresses.begin(), fde_addresses.end(), |
| Fde_address_compare<size>()); |
| |
| typename elfcpp::Elf_types<size>::Elf_Addr output_address; |
| output_address = this->address(); |
| |
| unsigned char* pfde = oview + 12; |
| for (typename Fde_addresses<size>::iterator p = fde_addresses.begin(); |
| p != fde_addresses.end(); |
| ++p) |
| { |
| elfcpp::Swap<32, big_endian>::writeval(pfde, |
| p->first - output_address); |
| elfcpp::Swap<32, big_endian>::writeval(pfde + 4, |
| p->second - output_address); |
| pfde += 8; |
| } |
| |
| gold_assert(pfde - oview == oview_size); |
| } |
| |
| of->write_output_view(off, oview_size, oview); |
| } |
| |
| // Given the offset FDE_OFFSET of an FDE in the .eh_frame section, and |
| // the contents of the .eh_frame section EH_FRAME_CONTENTS, where the |
| // FDE's encoding is FDE_ENCODING, return the output address of the |
| // FDE's PC. |
| |
| template<int size, bool big_endian> |
| typename elfcpp::Elf_types<size>::Elf_Addr |
| Eh_frame_hdr::get_fde_pc( |
| typename elfcpp::Elf_types<size>::Elf_Addr eh_frame_address, |
| const unsigned char* eh_frame_contents, |
| section_offset_type fde_offset, |
| unsigned char fde_encoding) |
| { |
| // The FDE starts with a 4 byte length and a 4 byte offset to the |
| // CIE. The PC follows. |
| const unsigned char* p = eh_frame_contents + fde_offset + 8; |
| |
| typename elfcpp::Elf_types<size>::Elf_Addr pc; |
| bool is_signed = (fde_encoding & elfcpp::DW_EH_PE_signed) != 0; |
| int pc_size = fde_encoding & 7; |
| if (pc_size == elfcpp::DW_EH_PE_absptr) |
| { |
| if (size == 32) |
| pc_size = elfcpp::DW_EH_PE_udata4; |
| else if (size == 64) |
| pc_size = elfcpp::DW_EH_PE_udata8; |
| else |
| gold_unreachable(); |
| } |
| |
| switch (pc_size) |
| { |
| case elfcpp::DW_EH_PE_udata2: |
| pc = elfcpp::Swap<16, big_endian>::readval(p); |
| if (is_signed) |
| pc = (pc ^ 0x8000) - 0x8000; |
| break; |
| |
| case elfcpp::DW_EH_PE_udata4: |
| pc = elfcpp::Swap<32, big_endian>::readval(p); |
| if (size > 32 && is_signed) |
| pc = (pc ^ 0x80000000) - 0x80000000; |
| break; |
| |
| case elfcpp::DW_EH_PE_udata8: |
| gold_assert(size == 64); |
| pc = elfcpp::Swap_unaligned<64, big_endian>::readval(p); |
| break; |
| |
| default: |
| // All other cases were rejected in Eh_frame::read_cie. |
| gold_unreachable(); |
| } |
| |
| switch (fde_encoding & 0x70) |
| { |
| case 0: |
| break; |
| |
| case elfcpp::DW_EH_PE_pcrel: |
| pc += eh_frame_address + fde_offset + 8; |
| break; |
| |
| case elfcpp::DW_EH_PE_datarel: |
| pc += parameters->target().ehframe_datarel_base(); |
| break; |
| |
| default: |
| // If other cases arise, then we have to handle them, or we have |
| // to reject them by returning false in Eh_frame::read_cie. |
| gold_unreachable(); |
| } |
| |
| gold_assert((fde_encoding & elfcpp::DW_EH_PE_indirect) == 0); |
| |
| return pc; |
| } |
| |
| // Given an array of FDE offsets in the .eh_frame section, return an |
| // array of offsets from the exception frame header to the FDE's |
| // output PC and to the output address of the FDE itself. We get the |
| // FDE's PC by actually looking in the .eh_frame section we just wrote |
| // to the output file. |
| |
| template<int size, bool big_endian> |
| void |
| Eh_frame_hdr::get_fde_addresses(Output_file* of, |
| const Fde_offsets* fde_offsets, |
| Fde_addresses<size>* fde_addresses) |
| { |
| typename elfcpp::Elf_types<size>::Elf_Addr eh_frame_address; |
| eh_frame_address = this->eh_frame_section_->address(); |
| off_t eh_frame_offset = this->eh_frame_section_->offset(); |
| off_t eh_frame_size = this->eh_frame_section_->data_size(); |
| const unsigned char* eh_frame_contents = of->get_input_view(eh_frame_offset, |
| eh_frame_size); |
| |
| for (Fde_offsets::const_iterator p = fde_offsets->begin(); |
| p != fde_offsets->end(); |
| ++p) |
| { |
| typename elfcpp::Elf_types<size>::Elf_Addr fde_pc; |
| fde_pc = this->get_fde_pc<size, big_endian>(eh_frame_address, |
| eh_frame_contents, |
| p->first, p->second); |
| fde_addresses->push_back(fde_pc, eh_frame_address + p->first); |
| } |
| |
| of->free_input_view(eh_frame_offset, eh_frame_size, eh_frame_contents); |
| } |
| |
| // Class Fde. |
| |
| // Write the FDE to OVIEW starting at OFFSET. CIE_OFFSET is the |
| // offset of the CIE in OVIEW. OUTPUT_OFFSET is the offset of the |
| // Eh_frame section within the output section. FDE_ENCODING is the |
| // encoding, from the CIE. ADDRALIGN is the required alignment. |
| // ADDRESS is the virtual address of OVIEW. Record the FDE pc for |
| // EH_FRAME_HDR. Return the new offset. |
| |
| template<int size, bool big_endian> |
| section_offset_type |
| Fde::write(unsigned char* oview, section_offset_type output_offset, |
| section_offset_type offset, uint64_t address, unsigned int addralign, |
| section_offset_type cie_offset, unsigned char fde_encoding, |
| Eh_frame_hdr* eh_frame_hdr) |
| { |
| gold_assert((offset & (addralign - 1)) == 0); |
| |
| size_t length = this->contents_.length(); |
| |
| // We add 8 when getting the aligned length to account for the |
| // length word and the CIE offset. |
| size_t aligned_full_length = align_address(length + 8, addralign); |
| |
| // Write the length of the FDE as a 32-bit word. The length word |
| // does not include the four bytes of the length word itself, but it |
| // does include the offset to the CIE. |
| elfcpp::Swap<32, big_endian>::writeval(oview + offset, |
| aligned_full_length - 4); |
| |
| // Write the offset to the CIE as a 32-bit word. This is the |
| // difference between the address of the offset word itself and the |
| // CIE address. |
| elfcpp::Swap<32, big_endian>::writeval(oview + offset + 4, |
| offset + 4 - cie_offset); |
| |
| // Copy the rest of the FDE. Note that this is run before |
| // relocation processing is done on this section, so the relocations |
| // will later be applied to the FDE data. |
| memcpy(oview + offset + 8, this->contents_.data(), length); |
| |
| // If this FDE is associated with a PLT, fill in the PLT's address |
| // and size. |
| if (this->object_ == NULL) |
| { |
| gold_assert(memcmp(oview + offset + 8, "\0\0\0\0\0\0\0\0", 8) == 0); |
| uint64_t paddress; |
| off_t psize; |
| parameters->target().plt_fde_location(this->u_.from_linker.plt, |
| oview + offset + 8, |
| &paddress, &psize); |
| uint64_t poffset = paddress - (address + offset + 8); |
| int32_t spoffset = static_cast<int32_t>(poffset); |
| uint32_t upsize = static_cast<uint32_t>(psize); |
| if (static_cast<uint64_t>(static_cast<int64_t>(spoffset)) != poffset |
| || static_cast<off_t>(upsize) != psize) |
| gold_warning(_("overflow in PLT unwind data; " |
| "unwinding through PLT may fail")); |
| elfcpp::Swap<32, big_endian>::writeval(oview + offset + 8, spoffset); |
| elfcpp::Swap<32, big_endian>::writeval(oview + offset + 12, upsize); |
| } |
| |
| if (aligned_full_length > length + 8) |
| memset(oview + offset + length + 8, 0, aligned_full_length - (length + 8)); |
| |
| // Tell the exception frame header about this FDE. |
| if (eh_frame_hdr != NULL) |
| eh_frame_hdr->record_fde(output_offset + offset, fde_encoding); |
| |
| return offset + aligned_full_length; |
| } |
| |
| // Class Cie. |
| |
| // Destructor. |
| |
| Cie::~Cie() |
| { |
| for (std::vector<Fde*>::iterator p = this->fdes_.begin(); |
| p != this->fdes_.end(); |
| ++p) |
| delete *p; |
| } |
| |
| // Set the output offset of a CIE. Return the new output offset. |
| |
| section_offset_type |
| Cie::set_output_offset(section_offset_type output_offset, |
| unsigned int addralign, |
| Output_section_data *output_data) |
| { |
| size_t length = this->contents_.length(); |
| |
| // Add 4 for length and 4 for zero CIE identifier tag. |
| length += 8; |
| |
| if (this->object_ != NULL) |
| { |
| // Add a mapping so that relocations are applied correctly. |
| this->object_->add_merge_mapping(output_data, this->shndx_, |
| this->input_offset_, length, |
| output_offset); |
| } |
| |
| length = align_address(length, addralign); |
| |
| for (std::vector<Fde*>::const_iterator p = this->fdes_.begin(); |
| p != this->fdes_.end(); |
| ++p) |
| { |
| (*p)->add_mapping(output_offset + length, output_data); |
| |
| size_t fde_length = (*p)->length(); |
| fde_length = align_address(fde_length, addralign); |
| length += fde_length; |
| } |
| |
| return output_offset + length; |
| } |
| |
| // Write the CIE to OVIEW starting at OFFSET. OUTPUT_OFFSET is the |
| // offset of the Eh_frame section within the output section. Round up |
| // the bytes to ADDRALIGN. ADDRESS is the virtual address of OVIEW. |
| // EH_FRAME_HDR is the exception frame header for FDE recording. |
| // POST_FDES stashes FDEs created after mappings were done, for later |
| // writing. Return the new offset. |
| |
| template<int size, bool big_endian> |
| section_offset_type |
| Cie::write(unsigned char* oview, section_offset_type output_offset, |
| section_offset_type offset, uint64_t address, |
| unsigned int addralign, Eh_frame_hdr* eh_frame_hdr, |
| Post_fdes* post_fdes) |
| { |
| gold_assert((offset & (addralign - 1)) == 0); |
| |
| section_offset_type cie_offset = offset; |
| |
| size_t length = this->contents_.length(); |
| |
| // We add 8 when getting the aligned length to account for the |
| // length word and the CIE tag. |
| size_t aligned_full_length = align_address(length + 8, addralign); |
| |
| // Write the length of the CIE as a 32-bit word. The length word |
| // does not include the four bytes of the length word itself. |
| elfcpp::Swap<32, big_endian>::writeval(oview + offset, |
| aligned_full_length - 4); |
| |
| // Write the tag which marks this as a CIE: a 32-bit zero. |
| elfcpp::Swap<32, big_endian>::writeval(oview + offset + 4, 0); |
| |
| // Write out the CIE data. |
| memcpy(oview + offset + 8, this->contents_.data(), length); |
| |
| if (aligned_full_length > length + 8) |
| memset(oview + offset + length + 8, 0, aligned_full_length - (length + 8)); |
| |
| offset += aligned_full_length; |
| |
| // Write out the associated FDEs. |
| unsigned char fde_encoding = this->fde_encoding_; |
| for (std::vector<Fde*>::const_iterator p = this->fdes_.begin(); |
| p != this->fdes_.end(); |
| ++p) |
| { |
| if ((*p)->post_map()) |
| post_fdes->push_back(Post_fde(*p, cie_offset, fde_encoding)); |
| else |
| offset = (*p)->write<size, big_endian>(oview, output_offset, offset, |
| address, addralign, cie_offset, |
| fde_encoding, eh_frame_hdr); |
| } |
| |
| return offset; |
| } |
| |
| // We track all the CIEs we see, and merge them when possible. This |
| // works because each FDE holds an offset to the relevant CIE: we |
| // rewrite the FDEs to point to the merged CIE. This is worthwhile |
| // because in a typical C++ program many FDEs in many different object |
| // files will use the same CIE. |
| |
| // An equality operator for Cie. |
| |
| bool |
| operator==(const Cie& cie1, const Cie& cie2) |
| { |
| return (cie1.personality_name_ == cie2.personality_name_ |
| && cie1.contents_ == cie2.contents_); |
| } |
| |
| // A less-than operator for Cie. |
| |
| bool |
| operator<(const Cie& cie1, const Cie& cie2) |
| { |
| if (cie1.personality_name_ != cie2.personality_name_) |
| return cie1.personality_name_ < cie2.personality_name_; |
| return cie1.contents_ < cie2.contents_; |
| } |
| |
| // Class Eh_frame. |
| |
| Eh_frame::Eh_frame() |
| : Output_section_data(Output_data::default_alignment()), |
| eh_frame_hdr_(NULL), |
| cie_offsets_(), |
| unmergeable_cie_offsets_(), |
| mappings_are_done_(false), |
| final_data_size_(0) |
| { |
| } |
| |
| // Skip an LEB128, updating *PP to point to the next character. |
| // Return false if we ran off the end of the string. |
| |
| bool |
| Eh_frame::skip_leb128(const unsigned char** pp, const unsigned char* pend) |
| { |
| const unsigned char* p; |
| for (p = *pp; p < pend; ++p) |
| { |
| if ((*p & 0x80) == 0) |
| { |
| *pp = p + 1; |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| // Add input section SHNDX in OBJECT to an exception frame section. |
| // SYMBOLS is the contents of the symbol table section (size |
| // SYMBOLS_SIZE), SYMBOL_NAMES is the symbol names section (size |
| // SYMBOL_NAMES_SIZE). RELOC_SHNDX is the index of a relocation |
| // section applying to SHNDX, or 0 if none, or -1U if more than one. |
| // RELOC_TYPE is the type of the reloc section if there is one, either |
| // SHT_REL or SHT_RELA. We try to parse the input exception frame |
| // data into our data structures. If we can't do it, we return false |
| // to mean that the section should be handled as a normal input |
| // section. |
| |
| template<int size, bool big_endian> |
| Eh_frame::Eh_frame_section_disposition |
| Eh_frame::add_ehframe_input_section( |
| Sized_relobj_file<size, big_endian>* object, |
| const unsigned char* symbols, |
| section_size_type symbols_size, |
| const unsigned char* symbol_names, |
| section_size_type symbol_names_size, |
| unsigned int shndx, |
| unsigned int reloc_shndx, |
| unsigned int reloc_type) |
| { |
| // Get the section contents. |
| section_size_type contents_len; |
| const unsigned char* pcontents = object->section_contents(shndx, |
| &contents_len, |
| false); |
| if (contents_len == 0) |
| return EH_EMPTY_SECTION; |
| |
| // If this is the marker section for the end of the data, then |
| // return false to force it to be handled as an ordinary input |
| // section. If we don't do this, we won't correctly handle the case |
| // of unrecognized .eh_frame sections. |
| if (contents_len == 4 |
| && elfcpp::Swap<32, big_endian>::readval(pcontents) == 0) |
| return EH_END_MARKER_SECTION; |
| |
| New_cies new_cies; |
| if (!this->do_add_ehframe_input_section(object, symbols, symbols_size, |
| symbol_names, symbol_names_size, |
| shndx, reloc_shndx, |
| reloc_type, pcontents, |
| contents_len, &new_cies)) |
| { |
| if (this->eh_frame_hdr_ != NULL) |
| this->eh_frame_hdr_->found_unrecognized_eh_frame_section(); |
| |
| for (New_cies::iterator p = new_cies.begin(); |
| p != new_cies.end(); |
| ++p) |
| delete p->first; |
| |
| return EH_UNRECOGNIZED_SECTION; |
| } |
| |
| // Now that we know we are using this section, record any new CIEs |
| // that we found. |
| for (New_cies::const_iterator p = new_cies.begin(); |
| p != new_cies.end(); |
| ++p) |
| { |
| if (p->second) |
| this->cie_offsets_.insert(p->first); |
| else |
| this->unmergeable_cie_offsets_.push_back(p->first); |
| } |
| |
| return EH_OPTIMIZABLE_SECTION; |
| } |
| |
| // The bulk of the implementation of add_ehframe_input_section. |
| |
| template<int size, bool big_endian> |
| bool |
| Eh_frame::do_add_ehframe_input_section( |
| Sized_relobj_file<size, big_endian>* object, |
| const unsigned char* symbols, |
| section_size_type symbols_size, |
| const unsigned char* symbol_names, |
| section_size_type symbol_names_size, |
| unsigned int shndx, |
| unsigned int reloc_shndx, |
| unsigned int reloc_type, |
| const unsigned char* pcontents, |
| section_size_type contents_len, |
| New_cies* new_cies) |
| { |
| Track_relocs<size, big_endian> relocs; |
| |
| const unsigned char* p = pcontents; |
| const unsigned char* pend = p + contents_len; |
| |
| // Get the contents of the reloc section if any. |
| if (!relocs.initialize(object, reloc_shndx, reloc_type)) |
| return false; |
| |
| // Keep track of which CIEs are at which offsets. |
| Offsets_to_cie cies; |
| |
| while (p < pend) |
| { |
| if (pend - p < 4) |
| return false; |
| |
| // There shouldn't be any relocations here. |
| if (relocs.advance(p + 4 - pcontents) > 0) |
| return false; |
| |
| unsigned int len = elfcpp::Swap<32, big_endian>::readval(p); |
| p += 4; |
| if (len == 0) |
| { |
| // We should only find a zero-length entry at the end of the |
| // section. |
| if (p < pend) |
| return false; |
| break; |
| } |
| // We don't support a 64-bit .eh_frame. |
| if (len == 0xffffffff) |
| return false; |
| if (static_cast<unsigned int>(pend - p) < len) |
| return false; |
| |
| const unsigned char* const pentend = p + len; |
| |
| if (pend - p < 4) |
| return false; |
| if (relocs.advance(p + 4 - pcontents) > 0) |
| return false; |
| |
| unsigned int id = elfcpp::Swap<32, big_endian>::readval(p); |
| p += 4; |
| |
| if (id == 0) |
| { |
| // CIE. |
| if (!this->read_cie(object, shndx, symbols, symbols_size, |
| symbol_names, symbol_names_size, |
| pcontents, p, pentend, &relocs, &cies, |
| new_cies)) |
| return false; |
| } |
| else |
| { |
| // FDE. |
| if (!this->read_fde(object, shndx, symbols, symbols_size, |
| pcontents, id, p, pentend, &relocs, &cies)) |
| return false; |
| } |
| |
| p = pentend; |
| } |
| |
| return true; |
| } |
| |
| // Read a CIE. Return false if we can't parse the information. |
| |
| template<int size, bool big_endian> |
| bool |
| Eh_frame::read_cie(Sized_relobj_file<size, big_endian>* object, |
| unsigned int shndx, |
| const unsigned char* symbols, |
| section_size_type symbols_size, |
| const unsigned char* symbol_names, |
| section_size_type symbol_names_size, |
| const unsigned char* pcontents, |
| const unsigned char* pcie, |
| const unsigned char* pcieend, |
| Track_relocs<size, big_endian>* relocs, |
| Offsets_to_cie* cies, |
| New_cies* new_cies) |
| { |
| bool mergeable = true; |
| |
| // We need to find the personality routine if there is one, since we |
| // can only merge CIEs which use the same routine. We also need to |
| // find the FDE encoding if there is one, so that we can read the PC |
| // from the FDE. |
| |
| const unsigned char* p = pcie; |
| |
| if (pcieend - p < 1) |
| return false; |
| unsigned char version = *p++; |
| if (version != 1 && version != 3) |
| return false; |
| |
| const unsigned char* paug = p; |
| const void* paugendv = memchr(p, '\0', pcieend - p); |
| const unsigned char* paugend = static_cast<const unsigned char*>(paugendv); |
| if (paugend == NULL) |
| return false; |
| p = paugend + 1; |
| |
| if (paug[0] == 'e' && paug[1] == 'h') |
| { |
| // This is a CIE from gcc before version 3.0. We can't merge |
| // these. We can still read the FDEs. |
| mergeable = false; |
| paug += 2; |
| if (*paug != '\0') |
| return false; |
| if (pcieend - p < size / 8) |
| return false; |
| p += size / 8; |
| } |
| |
| // Skip the code alignment. |
| if (!skip_leb128(&p, pcieend)) |
| return false; |
| |
| // Skip the data alignment. |
| if (!skip_leb128(&p, pcieend)) |
| return false; |
| |
| // Skip the return column. |
| if (version == 1) |
| { |
| if (pcieend - p < 1) |
| return false; |
| ++p; |
| } |
| else |
| { |
| if (!skip_leb128(&p, pcieend)) |
| return false; |
| } |
| |
| if (*paug == 'z') |
| { |
| ++paug; |
| // Skip the augmentation size. |
| if (!skip_leb128(&p, pcieend)) |
| return false; |
| } |
| |
| unsigned char fde_encoding = elfcpp::DW_EH_PE_absptr; |
| int per_offset = -1; |
| while (*paug != '\0') |
| { |
| switch (*paug) |
| { |
| case 'L': // LSDA encoding. |
| if (pcieend - p < 1) |
| return false; |
| ++p; |
| break; |
| |
| case 'R': // FDE encoding. |
| if (pcieend - p < 1) |
| return false; |
| fde_encoding = *p; |
| switch (fde_encoding & 7) |
| { |
| case elfcpp::DW_EH_PE_absptr: |
| case elfcpp::DW_EH_PE_udata2: |
| case elfcpp::DW_EH_PE_udata4: |
| case elfcpp::DW_EH_PE_udata8: |
| break; |
| default: |
| // We don't expect to see any other cases here, and |
| // we're not prepared to handle them. |
| return false; |
| } |
| ++p; |
| break; |
| |
| case 'S': |
| break; |
| |
| case 'P': |
| // Personality encoding. |
| { |
| if (pcieend - p < 1) |
| return false; |
| unsigned char per_encoding = *p; |
| ++p; |
| |
| if ((per_encoding & 0x60) == 0x60) |
| return false; |
| unsigned int per_width; |
| switch (per_encoding & 7) |
| { |
| case elfcpp::DW_EH_PE_udata2: |
| per_width = 2; |
| break; |
| case elfcpp::DW_EH_PE_udata4: |
| per_width = 4; |
| break; |
| case elfcpp::DW_EH_PE_udata8: |
| per_width = 8; |
| break; |
| case elfcpp::DW_EH_PE_absptr: |
| per_width = size / 8; |
| break; |
| default: |
| return false; |
| } |
| |
| if ((per_encoding & 0xf0) == elfcpp::DW_EH_PE_aligned) |
| { |
| unsigned int len = p - pcie; |
| len += per_width - 1; |
| len &= ~ (per_width - 1); |
| if (static_cast<unsigned int>(pcieend - p) < len) |
| return false; |
| p += len; |
| } |
| |
| per_offset = p - pcontents; |
| |
| if (static_cast<unsigned int>(pcieend - p) < per_width) |
| return false; |
| p += per_width; |
| } |
| break; |
| |
| default: |
| return false; |
| } |
| |
| ++paug; |
| } |
| |
| const char* personality_name = ""; |
| if (per_offset != -1) |
| { |
| if (relocs->advance(per_offset) > 0) |
| return false; |
| if (relocs->next_offset() != per_offset) |
| return false; |
| |
| unsigned int personality_symndx = relocs->next_symndx(); |
| if (personality_symndx == -1U) |
| return false; |
| |
| if (personality_symndx < object->local_symbol_count()) |
| { |
| // We can only merge this CIE if the personality routine is |
| // a global symbol. We can still read the FDEs. |
| mergeable = false; |
| } |
| else |
| { |
| const int sym_size = elfcpp::Elf_sizes<size>::sym_size; |
| if (personality_symndx >= symbols_size / sym_size) |
| return false; |
| elfcpp::Sym<size, big_endian> sym(symbols |
| + (personality_symndx * sym_size)); |
| unsigned int name_offset = sym.get_st_name(); |
| if (name_offset >= symbol_names_size) |
| return false; |
| personality_name = (reinterpret_cast<const char*>(symbol_names) |
| + name_offset); |
| } |
| |
| int r = relocs->advance(per_offset + 1); |
| gold_assert(r == 1); |
| } |
| |
| if (relocs->advance(pcieend - pcontents) > 0) |
| return false; |
| |
| Cie cie(object, shndx, (pcie - 8) - pcontents, fde_encoding, |
| personality_name, pcie, pcieend - pcie); |
| Cie* cie_pointer = NULL; |
| if (mergeable) |
| { |
| Cie_offsets::iterator find_cie = this->cie_offsets_.find(&cie); |
| if (find_cie != this->cie_offsets_.end()) |
| cie_pointer = *find_cie; |
| else |
| { |
| // See if we already saw this CIE in this object file. |
| for (New_cies::const_iterator pc = new_cies->begin(); |
| pc != new_cies->end(); |
| ++pc) |
| { |
| if (*(pc->first) == cie) |
| { |
| cie_pointer = pc->first; |
| break; |
| } |
| } |
| } |
| } |
| |
| if (cie_pointer == NULL) |
| { |
| cie_pointer = new Cie(cie); |
| new_cies->push_back(std::make_pair(cie_pointer, mergeable)); |
| } |
| else |
| { |
| // We are deleting this CIE. Record that in our mapping from |
| // input sections to the output section. At this point we don't |
| // know for sure that we are doing a special mapping for this |
| // input section, but that's OK--if we don't do a special |
| // mapping, nobody will ever ask for the mapping we add here. |
| object->add_merge_mapping(this, shndx, (pcie - 8) - pcontents, |
| pcieend - (pcie - 8), -1); |
| } |
| |
| // Record this CIE plus the offset in the input section. |
| cies->insert(std::make_pair(pcie - pcontents, cie_pointer)); |
| |
| return true; |
| } |
| |
| // Read an FDE. Return false if we can't parse the information. |
| |
| template<int size, bool big_endian> |
| bool |
| Eh_frame::read_fde(Sized_relobj_file<size, big_endian>* object, |
| unsigned int shndx, |
| const unsigned char* symbols, |
| section_size_type symbols_size, |
| const unsigned char* pcontents, |
| unsigned int offset, |
| const unsigned char* pfde, |
| const unsigned char* pfdeend, |
| Track_relocs<size, big_endian>* relocs, |
| Offsets_to_cie* cies) |
| { |
| // OFFSET is the distance between the 4 bytes before PFDE to the |
| // start of the CIE. The offset we recorded for the CIE is 8 bytes |
| // after the start of the CIE--after the length and the zero tag. |
| unsigned int cie_offset = (pfde - 4 - pcontents) - offset + 8; |
| Offsets_to_cie::const_iterator pcie = cies->find(cie_offset); |
| if (pcie == cies->end()) |
| return false; |
| Cie* cie = pcie->second; |
| |
| int pc_size = 0; |
| switch (cie->fde_encoding() & 7) |
| { |
| case elfcpp::DW_EH_PE_udata2: |
| pc_size = 2; |
| break; |
| case elfcpp::DW_EH_PE_udata4: |
| pc_size = 4; |
| break; |
| case elfcpp::DW_EH_PE_udata8: |
| gold_assert(size == 64); |
| pc_size = 8; |
| break; |
| case elfcpp::DW_EH_PE_absptr: |
| pc_size = size == 32 ? 4 : 8; |
| break; |
| default: |
| // All other cases were rejected in Eh_frame::read_cie. |
| gold_unreachable(); |
| } |
| |
| // The FDE should start with a reloc to the start of the code which |
| // it describes. |
| if (relocs->advance(pfde - pcontents) > 0) |
| return false; |
| if (relocs->next_offset() != pfde - pcontents) |
| { |
| // In an object produced by a relocatable link, gold may have |
| // discarded a COMDAT group in the previous link, but not the |
| // corresponding FDEs. In that case, gold will have discarded |
| // the relocations, so the FDE will have a non-relocatable zero |
| // (regardless of whether the PC encoding is absolute, pc-relative, |
| // or data-relative) instead of a pointer to the start of the code. |
| |
| uint64_t pc_value = 0; |
| switch (pc_size) |
| { |
| case 2: |
| pc_value = elfcpp::Swap<16, big_endian>::readval(pfde); |
| break; |
| case 4: |
| pc_value = elfcpp::Swap<32, big_endian>::readval(pfde); |
| break; |
| case 8: |
| pc_value = elfcpp::Swap_unaligned<64, big_endian>::readval(pfde); |
| break; |
| default: |
| gold_unreachable(); |
| } |
| |
| if (pc_value == 0) |
| { |
| // This FDE applies to a discarded function. We |
| // can discard this FDE. |
| object->add_merge_mapping(this, shndx, (pfde - 8) - pcontents, |
| pfdeend - (pfde - 8), -1); |
| return true; |
| } |
| |
| // Otherwise, reject the FDE. |
| return false; |
| } |
| |
| unsigned int symndx = relocs->next_symndx(); |
| if (symndx == -1U) |
| return false; |
| |
| // There can be another reloc in the FDE, if the CIE specifies an |
| // LSDA (language specific data area). We currently don't care. We |
| // will care later if we want to optimize the LSDA from an absolute |
| // pointer to a PC relative offset when generating a shared library. |
| relocs->advance(pfdeend - pcontents); |
| |
| // Find the section index for code that this FDE describes. |
| // If we have discarded the section, we can also discard the FDE. |
| unsigned int fde_shndx; |
| const int sym_size = elfcpp::Elf_sizes<size>::sym_size; |
| if (symndx >= symbols_size / sym_size) |
| return false; |
| elfcpp::Sym<size, big_endian> sym(symbols + symndx * sym_size); |
| bool is_ordinary; |
| fde_shndx = object->adjust_sym_shndx(symndx, sym.get_st_shndx(), |
| &is_ordinary); |
| bool is_discarded = (is_ordinary |
| && fde_shndx != elfcpp::SHN_UNDEF |
| && fde_shndx < object->shnum() |
| && !object->is_section_included(fde_shndx)); |
| |
| // Fetch the address range field from the FDE. The offset and size |
| // of the field depends on the PC encoding given in the CIE, but |
| // it is always an absolute value. If the address range is 0, this |
| // FDE corresponds to a function that was discarded during optimization |
| // (too late to discard the corresponding FDE). |
| uint64_t address_range = 0; |
| switch (pc_size) |
| { |
| case 2: |
| address_range = elfcpp::Swap<16, big_endian>::readval(pfde + 2); |
| break; |
| case 4: |
| address_range = elfcpp::Swap<32, big_endian>::readval(pfde + 4); |
| break; |
| case 8: |
| address_range = elfcpp::Swap_unaligned<64, big_endian>::readval(pfde + 8); |
| break; |
| default: |
| gold_unreachable(); |
| } |
| |
| if (is_discarded || address_range == 0) |
| { |
| // This FDE applies to a discarded function. We |
| // can discard this FDE. |
| object->add_merge_mapping(this, shndx, (pfde - 8) - pcontents, |
| pfdeend - (pfde - 8), -1); |
| return true; |
| } |
| |
| cie->add_fde(new Fde(object, shndx, (pfde - 8) - pcontents, |
| pfde, pfdeend - pfde)); |
| |
| return true; |
| } |
| |
| // Add unwind information for a PLT. |
| |
| void |
| Eh_frame::add_ehframe_for_plt(Output_data* plt, const unsigned char* cie_data, |
| size_t cie_length, const unsigned char* fde_data, |
| size_t fde_length) |
| { |
| Cie cie(NULL, 0, 0, elfcpp::DW_EH_PE_pcrel | elfcpp::DW_EH_PE_sdata4, "", |
| cie_data, cie_length); |
| Cie_offsets::iterator find_cie = this->cie_offsets_.find(&cie); |
| Cie* pcie; |
| if (find_cie != this->cie_offsets_.end()) |
| pcie = *find_cie; |
| else |
| { |
| gold_assert(!this->mappings_are_done_); |
| pcie = new Cie(cie); |
| this->cie_offsets_.insert(pcie); |
| } |
| |
| Fde* fde = new Fde(plt, fde_data, fde_length, this->mappings_are_done_); |
| pcie->add_fde(fde); |
| |
| if (this->mappings_are_done_) |
| this->final_data_size_ += align_address(fde_length + 8, this->addralign()); |
| } |
| |
| // Remove all post-map unwind information for a PLT. |
| |
| void |
| Eh_frame::remove_ehframe_for_plt(Output_data* plt, |
| const unsigned char* cie_data, |
| size_t cie_length) |
| { |
| if (!this->mappings_are_done_) |
| return; |
| |
| Cie cie(NULL, 0, 0, elfcpp::DW_EH_PE_pcrel | elfcpp::DW_EH_PE_sdata4, "", |
| cie_data, cie_length); |
| Cie_offsets::iterator find_cie = this->cie_offsets_.find(&cie); |
| gold_assert (find_cie != this->cie_offsets_.end()); |
| Cie* pcie = *find_cie; |
| |
| while (pcie->fde_count() != 0) |
| { |
| const Fde* fde = pcie->last_fde(); |
| if (!fde->post_map(plt)) |
| break; |
| size_t length = fde->length(); |
| this->final_data_size_ -= align_address(length + 8, this->addralign()); |
| pcie->remove_fde(); |
| } |
| } |
| |
| // Return the number of FDEs. |
| |
| unsigned int |
| Eh_frame::fde_count() const |
| { |
| unsigned int ret = 0; |
| for (Unmergeable_cie_offsets::const_iterator p = |
| this->unmergeable_cie_offsets_.begin(); |
| p != this->unmergeable_cie_offsets_.end(); |
| ++p) |
| ret += (*p)->fde_count(); |
| for (Cie_offsets::const_iterator p = this->cie_offsets_.begin(); |
| p != this->cie_offsets_.end(); |
| ++p) |
| ret += (*p)->fde_count(); |
| return ret; |
| } |
| |
| // Set the final data size. |
| |
| void |
| Eh_frame::set_final_data_size() |
| { |
| // We can be called more than once if Layout::set_segment_offsets |
| // finds a better mapping. We don't want to add all the mappings |
| // again. |
| if (this->mappings_are_done_) |
| { |
| this->set_data_size(this->final_data_size_); |
| return; |
| } |
| |
| section_offset_type output_start = 0; |
| if (this->is_offset_valid()) |
| output_start = this->offset() - this->output_section()->offset(); |
| section_offset_type output_offset = output_start; |
| |
| for (Unmergeable_cie_offsets::iterator p = |
| this->unmergeable_cie_offsets_.begin(); |
| p != this->unmergeable_cie_offsets_.end(); |
| ++p) |
| output_offset = (*p)->set_output_offset(output_offset, |
| this->addralign(), |
| this); |
| |
| for (Cie_offsets::iterator p = this->cie_offsets_.begin(); |
| p != this->cie_offsets_.end(); |
| ++p) |
| output_offset = (*p)->set_output_offset(output_offset, |
| this->addralign(), |
| this); |
| |
| this->mappings_are_done_ = true; |
| this->final_data_size_ = output_offset - output_start; |
| |
| gold_assert((output_offset & (this->addralign() - 1)) == 0); |
| this->set_data_size(this->final_data_size_); |
| } |
| |
| // Return an output offset for an input offset. |
| |
| bool |
| Eh_frame::do_output_offset(const Relobj* object, unsigned int shndx, |
| section_offset_type offset, |
| section_offset_type* poutput) const |
| { |
| return object->merge_output_offset(shndx, offset, poutput); |
| } |
| |
| // Write the data to the output file. |
| |
| void |
| Eh_frame::do_write(Output_file* of) |
| { |
| const off_t offset = this->offset(); |
| const off_t oview_size = this->data_size(); |
| unsigned char* const oview = of->get_output_view(offset, oview_size); |
| |
| switch (parameters->size_and_endianness()) |
| { |
| #ifdef HAVE_TARGET_32_LITTLE |
| case Parameters::TARGET_32_LITTLE: |
| this->do_sized_write<32, false>(oview); |
| break; |
| #endif |
| #ifdef HAVE_TARGET_32_BIG |
| case Parameters::TARGET_32_BIG: |
| this->do_sized_write<32, true>(oview); |
| break; |
| #endif |
| #ifdef HAVE_TARGET_64_LITTLE |
| case Parameters::TARGET_64_LITTLE: |
| this->do_sized_write<64, false>(oview); |
| break; |
| #endif |
| #ifdef HAVE_TARGET_64_BIG |
| case Parameters::TARGET_64_BIG: |
| this->do_sized_write<64, true>(oview); |
| break; |
| #endif |
| default: |
| gold_unreachable(); |
| } |
| |
| of->write_output_view(offset, oview_size, oview); |
| } |
| |
| // Write the data to the output file--template version. |
| |
| template<int size, bool big_endian> |
| void |
| Eh_frame::do_sized_write(unsigned char* oview) |
| { |
| uint64_t address = this->address(); |
| unsigned int addralign = this->addralign(); |
| section_offset_type o = 0; |
| const off_t output_offset = this->offset() - this->output_section()->offset(); |
| Post_fdes post_fdes; |
| for (Unmergeable_cie_offsets::iterator p = |
| this->unmergeable_cie_offsets_.begin(); |
| p != this->unmergeable_cie_offsets_.end(); |
| ++p) |
| o = (*p)->write<size, big_endian>(oview, output_offset, o, address, |
| addralign, this->eh_frame_hdr_, |
| &post_fdes); |
| for (Cie_offsets::iterator p = this->cie_offsets_.begin(); |
| p != this->cie_offsets_.end(); |
| ++p) |
| o = (*p)->write<size, big_endian>(oview, output_offset, o, address, |
| addralign, this->eh_frame_hdr_, |
| &post_fdes); |
| for (Post_fdes::iterator p = post_fdes.begin(); |
| p != post_fdes.end(); |
| ++p) |
| o = (*p).fde->write<size, big_endian>(oview, output_offset, o, address, |
| addralign, (*p).cie_offset, |
| (*p).fde_encoding, |
| this->eh_frame_hdr_); |
| } |
| |
| #ifdef HAVE_TARGET_32_LITTLE |
| template |
| Eh_frame::Eh_frame_section_disposition |
| Eh_frame::add_ehframe_input_section<32, false>( |
| Sized_relobj_file<32, false>* object, |
| const unsigned char* symbols, |
| section_size_type symbols_size, |
| const unsigned char* symbol_names, |
| section_size_type symbol_names_size, |
| unsigned int shndx, |
| unsigned int reloc_shndx, |
| unsigned int reloc_type); |
| #endif |
| |
| #ifdef HAVE_TARGET_32_BIG |
| template |
| Eh_frame::Eh_frame_section_disposition |
| Eh_frame::add_ehframe_input_section<32, true>( |
| Sized_relobj_file<32, true>* object, |
| const unsigned char* symbols, |
| section_size_type symbols_size, |
| const unsigned char* symbol_names, |
| section_size_type symbol_names_size, |
| unsigned int shndx, |
| unsigned int reloc_shndx, |
| unsigned int reloc_type); |
| #endif |
| |
| #ifdef HAVE_TARGET_64_LITTLE |
| template |
| Eh_frame::Eh_frame_section_disposition |
| Eh_frame::add_ehframe_input_section<64, false>( |
| Sized_relobj_file<64, false>* object, |
| const unsigned char* symbols, |
| section_size_type symbols_size, |
| const unsigned char* symbol_names, |
| section_size_type symbol_names_size, |
| unsigned int shndx, |
| unsigned int reloc_shndx, |
| unsigned int reloc_type); |
| #endif |
| |
| #ifdef HAVE_TARGET_64_BIG |
| template |
| Eh_frame::Eh_frame_section_disposition |
| Eh_frame::add_ehframe_input_section<64, true>( |
| Sized_relobj_file<64, true>* object, |
| const unsigned char* symbols, |
| section_size_type symbols_size, |
| const unsigned char* symbol_names, |
| section_size_type symbol_names_size, |
| unsigned int shndx, |
| unsigned int reloc_shndx, |
| unsigned int reloc_type); |
| #endif |
| |
| } // End namespace gold. |