// ehframe.cc -- handle exception frame sections for gold
// Copyright (C) 2006-2024 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <
[email protected]>.
// 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.
