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binutils-gdb/gold/i386.cc

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// i386.cc -- i386 target support for gold.
// Copyright 2006, 2007 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 "elfcpp.h"
#include "parameters.h"
#include "reloc.h"
#include "i386.h"
#include "object.h"
#include "symtab.h"
#include "layout.h"
#include "output.h"
#include "target.h"
#include "target-reloc.h"
#include "target-select.h"
#include "tls.h"
namespace
{
using namespace gold;
class Output_data_plt_i386;
// The i386 target class.
// TLS info comes from
// http://people.redhat.com/drepper/tls.pdf
// http://www.lsd.ic.unicamp.br/~oliva/writeups/TLS/RFC-TLSDESC-x86.txt
class Target_i386 : public Sized_target<32, false>
{
public:
typedef Output_data_reloc<elfcpp::SHT_REL, true, 32, false> Reloc_section;
Target_i386()
: Sized_target<32, false>(&i386_info),
got_(NULL), plt_(NULL), got_plt_(NULL), rel_dyn_(NULL),
copy_relocs_(NULL), dynbss_(NULL)
{ }
// Scan the relocations to look for symbol adjustments.
void
scan_relocs(const General_options& options,
Symbol_table* symtab,
Layout* layout,
Sized_relobj<32, false>* object,
unsigned int data_shndx,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
size_t local_symbol_count,
const unsigned char* plocal_symbols,
Symbol** global_symbols);
// Finalize the sections.
void
do_finalize_sections(Layout*);
// Return the value to use for a dynamic which requires special
// treatment.
uint64_t
do_dynsym_value(const Symbol*) const;
// Relocate a section.
void
relocate_section(const Relocate_info<32, false>*,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
unsigned char* view,
elfcpp::Elf_types<32>::Elf_Addr view_address,
off_t view_size);
// Return a string used to fill a code section with nops.
std::string
do_code_fill(off_t length);
// Return the size of the GOT section.
off_t
got_size()
{
gold_assert(this->got_ != NULL);
return this->got_->data_size();
}
private:
// The class which scans relocations.
struct Scan
{
inline void
local(const General_options& options, Symbol_table* symtab,
Layout* layout, Target_i386* target,
Sized_relobj<32, false>* object,
unsigned int data_shndx,
const elfcpp::Rel<32, false>& reloc, unsigned int r_type,
const elfcpp::Sym<32, false>& lsym);
inline void
global(const General_options& options, Symbol_table* symtab,
Layout* layout, Target_i386* target,
Sized_relobj<32, false>* object,
unsigned int data_shndx,
const elfcpp::Rel<32, false>& reloc, unsigned int r_type,
Symbol* gsym);
static void
unsupported_reloc_local(Sized_relobj<32, false>*, unsigned int r_type);
static void
unsupported_reloc_global(Sized_relobj<32, false>*, unsigned int r_type,
Symbol*);
};
// The class which implements relocation.
class Relocate
{
public:
Relocate()
: skip_call_tls_get_addr_(false),
local_dynamic_type_(LOCAL_DYNAMIC_NONE)
{ }
~Relocate()
{
if (this->skip_call_tls_get_addr_)
{
// FIXME: This needs to specify the location somehow.
gold_error(_("missing expected TLS relocation"));
}
}
// Return whether the static relocation needs to be applied.
inline bool
should_apply_static_reloc(const Sized_symbol<32>* gsym,
bool is_pcrel,
bool is_32bit);
// Do a relocation. Return false if the caller should not issue
// any warnings about this relocation.
inline bool
relocate(const Relocate_info<32, false>*, Target_i386*, size_t relnum,
const elfcpp::Rel<32, false>&,
unsigned int r_type, const Sized_symbol<32>*,
const Symbol_value<32>*,
unsigned char*, elfcpp::Elf_types<32>::Elf_Addr,
off_t);
private:
// Do a TLS relocation.
inline void
relocate_tls(const Relocate_info<32, false>*, size_t relnum,
const elfcpp::Rel<32, false>&,
unsigned int r_type, const Sized_symbol<32>*,
const Symbol_value<32>*,
unsigned char*, elfcpp::Elf_types<32>::Elf_Addr, off_t);
// Do a TLS General-Dynamic to Local-Exec transition.
inline void
tls_gd_to_le(const Relocate_info<32, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rel<32, false>&, unsigned int r_type,
elfcpp::Elf_types<32>::Elf_Addr value,
unsigned char* view,
off_t view_size);
// Do a TLS Local-Dynamic to Local-Exec transition.
inline void
tls_ld_to_le(const Relocate_info<32, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rel<32, false>&, unsigned int r_type,
elfcpp::Elf_types<32>::Elf_Addr value,
unsigned char* view,
off_t view_size);
// Do a TLS Initial-Exec to Local-Exec transition.
static inline void
tls_ie_to_le(const Relocate_info<32, false>*, size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rel<32, false>&, unsigned int r_type,
elfcpp::Elf_types<32>::Elf_Addr value,
unsigned char* view,
off_t view_size);
// We need to keep track of which type of local dynamic relocation
// we have seen, so that we can optimize R_386_TLS_LDO_32 correctly.
enum Local_dynamic_type
{
LOCAL_DYNAMIC_NONE,
LOCAL_DYNAMIC_SUN,
LOCAL_DYNAMIC_GNU
};
// This is set if we should skip the next reloc, which should be a
// PLT32 reloc against ___tls_get_addr.
bool skip_call_tls_get_addr_;
// The type of local dynamic relocation we have seen in the section
// being relocated, if any.
Local_dynamic_type local_dynamic_type_;
};
// Adjust TLS relocation type based on the options and whether this
// is a local symbol.
static tls::Tls_optimization
optimize_tls_reloc(bool is_final, int r_type);
// Get the GOT section, creating it if necessary.
Output_data_got<32, false>*
got_section(Symbol_table*, Layout*);
// Get the GOT PLT section.
Output_data_space*
got_plt_section() const
{
gold_assert(this->got_plt_ != NULL);
return this->got_plt_;
}
// Create a PLT entry for a global symbol.
void
make_plt_entry(Symbol_table*, Layout*, Symbol*);
// Get the PLT section.
const Output_data_plt_i386*
plt_section() const
{
gold_assert(this->plt_ != NULL);
return this->plt_;
}
// Get the dynamic reloc section, creating it if necessary.
Reloc_section*
rel_dyn_section(Layout*);
// Copy a relocation against a global symbol.
void
copy_reloc(const General_options*, Symbol_table*, Layout*,
Sized_relobj<32, false>*, unsigned int,
Symbol*, const elfcpp::Rel<32, false>&);
// Information about this specific target which we pass to the
// general Target structure.
static const Target::Target_info i386_info;
// The GOT section.
Output_data_got<32, false>* got_;
// The PLT section.
Output_data_plt_i386* plt_;
// The GOT PLT section.
Output_data_space* got_plt_;
// The dynamic reloc section.
Reloc_section* rel_dyn_;
// Relocs saved to avoid a COPY reloc.
Copy_relocs<32, false>* copy_relocs_;
// Space for variables copied with a COPY reloc.
Output_data_space* dynbss_;
};
const Target::Target_info Target_i386::i386_info =
{
32, // size
false, // is_big_endian
elfcpp::EM_386, // machine_code
false, // has_make_symbol
false, // has_resolve
true, // has_code_fill
true, // is_default_stack_executable
"/usr/lib/libc.so.1", // dynamic_linker
0x08048000, // default_text_segment_address
0x1000, // abi_pagesize
0x1000 // common_pagesize
};
// Get the GOT section, creating it if necessary.
Output_data_got<32, false>*
Target_i386::got_section(Symbol_table* symtab, Layout* layout)
{
if (this->got_ == NULL)
{
gold_assert(symtab != NULL && layout != NULL);
this->got_ = new Output_data_got<32, false>();
layout->add_output_section_data(".got", elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
this->got_);
// The old GNU linker creates a .got.plt section. We just
// create another set of data in the .got section. Note that we
// always create a PLT if we create a GOT, although the PLT
// might be empty.
this->got_plt_ = new Output_data_space(4);
layout->add_output_section_data(".got", elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
this->got_plt_);
// The first three entries are reserved.
this->got_plt_->set_space_size(3 * 4);
// Define _GLOBAL_OFFSET_TABLE_ at the start of the PLT.
symtab->define_in_output_data(this, "_GLOBAL_OFFSET_TABLE_", NULL,
this->got_plt_,
0, 0, elfcpp::STT_OBJECT,
elfcpp::STB_LOCAL,
elfcpp::STV_HIDDEN, 0,
false, false);
}
return this->got_;
}
// Get the dynamic reloc section, creating it if necessary.
Target_i386::Reloc_section*
Target_i386::rel_dyn_section(Layout* layout)
{
if (this->rel_dyn_ == NULL)
{
gold_assert(layout != NULL);
this->rel_dyn_ = new Reloc_section();
layout->add_output_section_data(".rel.dyn", elfcpp::SHT_REL,
elfcpp::SHF_ALLOC, this->rel_dyn_);
}
return this->rel_dyn_;
}
// A class to handle the PLT data.
class Output_data_plt_i386 : public Output_section_data
{
public:
typedef Output_data_reloc<elfcpp::SHT_REL, true, 32, false> Reloc_section;
Output_data_plt_i386(Layout*, Output_data_space*);
// Add an entry to the PLT.
void
add_entry(Symbol* gsym);
// Return the .rel.plt section data.
const Reloc_section*
rel_plt() const
{ return this->rel_; }
protected:
void
do_adjust_output_section(Output_section* os);
private:
// The size of an entry in the PLT.
static const int plt_entry_size = 16;
// The first entry in the PLT for an executable.
static unsigned char exec_first_plt_entry[plt_entry_size];
// The first entry in the PLT for a shared object.
static unsigned char dyn_first_plt_entry[plt_entry_size];
// Other entries in the PLT for an executable.
static unsigned char exec_plt_entry[plt_entry_size];
// Other entries in the PLT for a shared object.
static unsigned char dyn_plt_entry[plt_entry_size];
// Set the final size.
void
do_set_address(uint64_t, off_t)
{ this->set_data_size((this->count_ + 1) * plt_entry_size); }
// Write out the PLT data.
void
do_write(Output_file*);
// The reloc section.
Reloc_section* rel_;
// The .got.plt section.
Output_data_space* got_plt_;
// The number of PLT entries.
unsigned int count_;
};
// Create the PLT section. The ordinary .got section is an argument,
// since we need to refer to the start. We also create our own .got
// section just for PLT entries.
Output_data_plt_i386::Output_data_plt_i386(Layout* layout,
Output_data_space* got_plt)
: Output_section_data(4), got_plt_(got_plt), count_(0)
{
this->rel_ = new Reloc_section();
layout->add_output_section_data(".rel.plt", elfcpp::SHT_REL,
elfcpp::SHF_ALLOC, this->rel_);
}
void
Output_data_plt_i386::do_adjust_output_section(Output_section* os)
{
// UnixWare sets the entsize of .plt to 4, and so does the old GNU
// linker, and so do we.
os->set_entsize(4);
}
// Add an entry to the PLT.
void
Output_data_plt_i386::add_entry(Symbol* gsym)
{
gold_assert(!gsym->has_plt_offset());
// Note that when setting the PLT offset we skip the initial
// reserved PLT entry.
gsym->set_plt_offset((this->count_ + 1) * plt_entry_size);
++this->count_;
off_t got_offset = this->got_plt_->data_size();
// Every PLT entry needs a GOT entry which points back to the PLT
// entry (this will be changed by the dynamic linker, normally
// lazily when the function is called).
this->got_plt_->set_space_size(got_offset + 4);
// Every PLT entry needs a reloc.
gsym->set_needs_dynsym_entry();
this->rel_->add_global(gsym, elfcpp::R_386_JUMP_SLOT, this->got_plt_,
got_offset);
// Note that we don't need to save the symbol. The contents of the
// PLT are independent of which symbols are used. The symbols only
// appear in the relocations.
}
// The first entry in the PLT for an executable.
unsigned char Output_data_plt_i386::exec_first_plt_entry[plt_entry_size] =
{
0xff, 0x35, // pushl contents of memory address
0, 0, 0, 0, // replaced with address of .got + 4
0xff, 0x25, // jmp indirect
0, 0, 0, 0, // replaced with address of .got + 8
0, 0, 0, 0 // unused
};
// The first entry in the PLT for a shared object.
unsigned char Output_data_plt_i386::dyn_first_plt_entry[plt_entry_size] =
{
0xff, 0xb3, 4, 0, 0, 0, // pushl 4(%ebx)
0xff, 0xa3, 8, 0, 0, 0, // jmp *8(%ebx)
0, 0, 0, 0 // unused
};
// Subsequent entries in the PLT for an executable.
unsigned char Output_data_plt_i386::exec_plt_entry[plt_entry_size] =
{
0xff, 0x25, // jmp indirect
0, 0, 0, 0, // replaced with address of symbol in .got
0x68, // pushl immediate
0, 0, 0, 0, // replaced with offset into relocation table
0xe9, // jmp relative
0, 0, 0, 0 // replaced with offset to start of .plt
};
// Subsequent entries in the PLT for a shared object.
unsigned char Output_data_plt_i386::dyn_plt_entry[plt_entry_size] =
{
0xff, 0xa3, // jmp *offset(%ebx)
0, 0, 0, 0, // replaced with offset of symbol in .got
0x68, // pushl immediate
0, 0, 0, 0, // replaced with offset into relocation table
0xe9, // jmp relative
0, 0, 0, 0 // replaced with offset to start of .plt
};
// Write out the PLT. This uses the hand-coded instructions above,
// and adjusts them as needed. This is all specified by the i386 ELF
// Processor Supplement.
void
Output_data_plt_i386::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);
const off_t got_file_offset = this->got_plt_->offset();
const off_t got_size = this->got_plt_->data_size();
unsigned char* const got_view = of->get_output_view(got_file_offset,
got_size);
unsigned char* pov = oview;
elfcpp::Elf_types<32>::Elf_Addr plt_address = this->address();
elfcpp::Elf_types<32>::Elf_Addr got_address = this->got_plt_->address();
if (parameters->output_is_shared())
memcpy(pov, dyn_first_plt_entry, plt_entry_size);
else
{
memcpy(pov, exec_first_plt_entry, plt_entry_size);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 2, got_address + 4);
elfcpp::Swap<32, false>::writeval(pov + 8, got_address + 8);
}
pov += plt_entry_size;
unsigned char* got_pov = got_view;
memset(got_pov, 0, 12);
got_pov += 12;
const int rel_size = elfcpp::Elf_sizes<32>::rel_size;
unsigned int plt_offset = plt_entry_size;
unsigned int plt_rel_offset = 0;
unsigned int got_offset = 12;
const unsigned int count = this->count_;
for (unsigned int i = 0;
i < count;
++i,
pov += plt_entry_size,
got_pov += 4,
plt_offset += plt_entry_size,
plt_rel_offset += rel_size,
got_offset += 4)
{
// Set and adjust the PLT entry itself.
if (parameters->output_is_shared())
{
memcpy(pov, dyn_plt_entry, plt_entry_size);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 2, got_offset);
}
else
{
memcpy(pov, exec_plt_entry, plt_entry_size);
elfcpp::Swap_unaligned<32, false>::writeval(pov + 2,
(got_address
+ got_offset));
}
elfcpp::Swap_unaligned<32, false>::writeval(pov + 7, plt_rel_offset);
elfcpp::Swap<32, false>::writeval(pov + 12,
- (plt_offset + plt_entry_size));
// Set the entry in the GOT.
elfcpp::Swap<32, false>::writeval(got_pov, plt_address + plt_offset + 6);
}
gold_assert(pov - oview == oview_size);
gold_assert(got_pov - got_view == got_size);
of->write_output_view(offset, oview_size, oview);
of->write_output_view(got_file_offset, got_size, got_view);
}
// Create a PLT entry for a global symbol.
void
Target_i386::make_plt_entry(Symbol_table* symtab, Layout* layout, Symbol* gsym)
{
if (gsym->has_plt_offset())
return;
if (this->plt_ == NULL)
{
// Create the GOT sections first.
this->got_section(symtab, layout);
this->plt_ = new Output_data_plt_i386(layout, this->got_plt_);
layout->add_output_section_data(".plt", elfcpp::SHT_PROGBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_EXECINSTR),
this->plt_);
}
this->plt_->add_entry(gsym);
}
// Handle a relocation against a non-function symbol defined in a
// dynamic object. The traditional way to handle this is to generate
// a COPY relocation to copy the variable at runtime from the shared
// object into the executable's data segment. However, this is
// undesirable in general, as if the size of the object changes in the
// dynamic object, the executable will no longer work correctly. If
// this relocation is in a writable section, then we can create a
// dynamic reloc and the dynamic linker will resolve it to the correct
// address at runtime. However, we do not want do that if the
// relocation is in a read-only section, as it would prevent the
// readonly segment from being shared. And if we have to eventually
// generate a COPY reloc, then any dynamic relocations will be
// useless. So this means that if this is a writable section, we need
// to save the relocation until we see whether we have to create a
// COPY relocation for this symbol for any other relocation.
void
Target_i386::copy_reloc(const General_options* options,
Symbol_table* symtab,
Layout* layout,
Sized_relobj<32, false>* object,
unsigned int data_shndx, Symbol* gsym,
const elfcpp::Rel<32, false>& rel)
{
Sized_symbol<32>* ssym;
ssym = symtab->get_sized_symbol SELECT_SIZE_NAME(32) (gsym
SELECT_SIZE(32));
if (!Copy_relocs<32, false>::need_copy_reloc(options, object,
data_shndx, ssym))
{
// So far we do not need a COPY reloc. Save this relocation.
// If it turns out that we never need a COPY reloc for this
// symbol, then we will emit the relocation.
if (this->copy_relocs_ == NULL)
this->copy_relocs_ = new Copy_relocs<32, false>();
this->copy_relocs_->save(ssym, object, data_shndx, rel);
}
else
{
// Allocate space for this symbol in the .bss section.
elfcpp::Elf_types<32>::Elf_WXword symsize = ssym->symsize();
// There is no defined way to determine the required alignment
// of the symbol. We pick the alignment based on the size. We
// set an arbitrary maximum of 256.
unsigned int align;
for (align = 1; align < 512; align <<= 1)
if ((symsize & align) != 0)
break;
if (this->dynbss_ == NULL)
{
this->dynbss_ = new Output_data_space(align);
layout->add_output_section_data(".bss",
elfcpp::SHT_NOBITS,
(elfcpp::SHF_ALLOC
| elfcpp::SHF_WRITE),
this->dynbss_);
}
Output_data_space* dynbss = this->dynbss_;
if (align > dynbss->addralign())
dynbss->set_space_alignment(align);
off_t dynbss_size = dynbss->data_size();
dynbss_size = align_address(dynbss_size, align);
off_t offset = dynbss_size;
dynbss->set_space_size(dynbss_size + symsize);
symtab->define_with_copy_reloc(this, ssym, dynbss, offset);
// Add the COPY reloc.
Reloc_section* rel_dyn = this->rel_dyn_section(layout);
rel_dyn->add_global(ssym, elfcpp::R_386_COPY, dynbss, offset);
}
}
// Optimize the TLS relocation type based on what we know about the
// symbol. IS_FINAL is true if the final address of this symbol is
// known at link time.
tls::Tls_optimization
Target_i386::optimize_tls_reloc(bool is_final, int r_type)
{
// If we are generating a shared library, then we can't do anything
// in the linker.
if (parameters->output_is_shared())
return tls::TLSOPT_NONE;
switch (r_type)
{
case elfcpp::R_386_TLS_GD:
case elfcpp::R_386_TLS_GOTDESC:
case elfcpp::R_386_TLS_DESC_CALL:
// These are General-Dynamic which permits fully general TLS
// access. Since we know that we are generating an executable,
// we can convert this to Initial-Exec. If we also know that
// this is a local symbol, we can further switch to Local-Exec.
if (is_final)
return tls::TLSOPT_TO_LE;
return tls::TLSOPT_TO_IE;
case elfcpp::R_386_TLS_LDM:
// This is Local-Dynamic, which refers to a local symbol in the
// dynamic TLS block. Since we know that we generating an
// executable, we can switch to Local-Exec.
return tls::TLSOPT_TO_LE;
case elfcpp::R_386_TLS_LDO_32:
// Another type of Local-Dynamic relocation.
return tls::TLSOPT_TO_LE;
case elfcpp::R_386_TLS_IE:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_IE_32:
// These are Initial-Exec relocs which get the thread offset
// from the GOT. If we know that we are linking against the
// local symbol, we can switch to Local-Exec, which links the
// thread offset into the instruction.
if (is_final)
return tls::TLSOPT_TO_LE;
return tls::TLSOPT_NONE;
case elfcpp::R_386_TLS_LE:
case elfcpp::R_386_TLS_LE_32:
// When we already have Local-Exec, there is nothing further we
// can do.
return tls::TLSOPT_NONE;
default:
gold_unreachable();
}
}
// Report an unsupported relocation against a local symbol.
void
Target_i386::Scan::unsupported_reloc_local(Sized_relobj<32, false>* object,
unsigned int r_type)
{
gold_error(_("%s: unsupported reloc %u against local symbol"),
object->name().c_str(), r_type);
}
// Scan a relocation for a local symbol.
inline void
Target_i386::Scan::local(const General_options&,
Symbol_table* symtab,
Layout* layout,
Target_i386* target,
Sized_relobj<32, false>* object,
unsigned int data_shndx,
const elfcpp::Rel<32, false>& reloc,
unsigned int r_type,
const elfcpp::Sym<32, false>&)
{
switch (r_type)
{
case elfcpp::R_386_NONE:
case elfcpp::R_386_GNU_VTINHERIT:
case elfcpp::R_386_GNU_VTENTRY:
break;
case elfcpp::R_386_32:
case elfcpp::R_386_16:
case elfcpp::R_386_8:
// If building a shared library (or a position-independent
// executable), we need to create a dynamic relocation for
// this location. The relocation applied at link time will
// apply the link-time value, so we flag the location with
// an R_386_RELATIVE relocation so the dynamic loader can
// relocate it easily.
if (parameters->output_is_position_independent())
{
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
if (r_type == elfcpp::R_386_32)
rel_dyn->add_local(object, 0, elfcpp::R_386_RELATIVE, data_shndx,
reloc.get_r_offset());
else
{
unsigned int r_sym = elfcpp::elf_r_sym<32>(reloc.get_r_info());
rel_dyn->add_local(object, r_sym, r_type, data_shndx,
reloc.get_r_offset());
}
}
break;
case elfcpp::R_386_PC32:
case elfcpp::R_386_PC16:
case elfcpp::R_386_PC8:
break;
case elfcpp::R_386_PLT32:
// Since we know this is a local symbol, we can handle this as a
// PC32 reloc.
break;
case elfcpp::R_386_GOTOFF:
case elfcpp::R_386_GOTPC:
// We need a GOT section.
target->got_section(symtab, layout);
break;
case elfcpp::R_386_GOT32:
{
// The symbol requires a GOT entry.
Output_data_got<32, false>* got = target->got_section(symtab, layout);
unsigned int r_sym = elfcpp::elf_r_sym<32>(reloc.get_r_info());
if (got->add_local(object, r_sym))
{
// If we are generating a shared object, we need to add a
// dynamic RELATIVE relocation for this symbol.
if (parameters->output_is_position_independent())
{
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
rel_dyn->add_local(object, 0, elfcpp::R_386_RELATIVE,
data_shndx, reloc.get_r_offset());
}
}
}
break;
// These are relocations which should only be seen by the
// dynamic linker, and should never be seen here.
case elfcpp::R_386_COPY:
case elfcpp::R_386_GLOB_DAT:
case elfcpp::R_386_JUMP_SLOT:
case elfcpp::R_386_RELATIVE:
case elfcpp::R_386_TLS_TPOFF:
case elfcpp::R_386_TLS_DTPMOD32:
case elfcpp::R_386_TLS_DTPOFF32:
case elfcpp::R_386_TLS_TPOFF32:
case elfcpp::R_386_TLS_DESC:
gold_error(_("%s: unexpected reloc %u in object file"),
object->name().c_str(), r_type);
break;
// These are initial TLS relocs, which are expected when
// linking.
case elfcpp::R_386_TLS_GD: // Global-dynamic
case elfcpp::R_386_TLS_GOTDESC: // Global-dynamic (from ~oliva url)
case elfcpp::R_386_TLS_DESC_CALL:
case elfcpp::R_386_TLS_LDM: // Local-dynamic
case elfcpp::R_386_TLS_LDO_32: // Alternate local-dynamic
case elfcpp::R_386_TLS_IE: // Initial-exec
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_LE: // Local-exec
case elfcpp::R_386_TLS_LE_32:
{
bool output_is_shared = parameters->output_is_shared();
const tls::Tls_optimization optimized_type
= Target_i386::optimize_tls_reloc(!output_is_shared, r_type);
switch (r_type)
{
case elfcpp::R_386_TLS_GD: // Global-dynamic
case elfcpp::R_386_TLS_GOTDESC: // Global-dynamic (from ~oliva)
case elfcpp::R_386_TLS_DESC_CALL:
// FIXME: If not relaxing to LE, we need to generate
// DTPMOD32 and DTPOFF32 relocs.
if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_local(object, r_type);
break;
case elfcpp::R_386_TLS_LDM: // Local-dynamic
// FIXME: If not relaxing to LE, we need to generate a
// DTPMOD32 reloc.
if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_local(object, r_type);
break;
case elfcpp::R_386_TLS_LDO_32: // Alternate local-dynamic
break;
case elfcpp::R_386_TLS_IE: // Initial-exec
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTIE:
// FIXME: If not relaxing to LE, we need to generate a
// TPOFF or TPOFF32 reloc.
if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_local(object, r_type);
break;
case elfcpp::R_386_TLS_LE: // Local-exec
case elfcpp::R_386_TLS_LE_32:
// FIXME: If generating a shared object, we need to copy
// this relocation into the object.
gold_assert(!output_is_shared);
break;
default:
gold_unreachable();
}
}
break;
case elfcpp::R_386_32PLT:
case elfcpp::R_386_TLS_GD_32:
case elfcpp::R_386_TLS_GD_PUSH:
case elfcpp::R_386_TLS_GD_CALL:
case elfcpp::R_386_TLS_GD_POP:
case elfcpp::R_386_TLS_LDM_32:
case elfcpp::R_386_TLS_LDM_PUSH:
case elfcpp::R_386_TLS_LDM_CALL:
case elfcpp::R_386_TLS_LDM_POP:
case elfcpp::R_386_USED_BY_INTEL_200:
default:
unsupported_reloc_local(object, r_type);
break;
}
}
// Report an unsupported relocation against a global symbol.
void
Target_i386::Scan::unsupported_reloc_global(Sized_relobj<32, false>* object,
unsigned int r_type,
Symbol* gsym)
{
gold_error(_("%s: unsupported reloc %u against global symbol %s"),
object->name().c_str(), r_type, gsym->name());
}
// Scan a relocation for a global symbol.
inline void
Target_i386::Scan::global(const General_options& options,
Symbol_table* symtab,
Layout* layout,
Target_i386* target,
Sized_relobj<32, false>* object,
unsigned int data_shndx,
const elfcpp::Rel<32, false>& reloc,
unsigned int r_type,
Symbol* gsym)
{
switch (r_type)
{
case elfcpp::R_386_NONE:
case elfcpp::R_386_GNU_VTINHERIT:
case elfcpp::R_386_GNU_VTENTRY:
break;
case elfcpp::R_386_32:
case elfcpp::R_386_PC32:
case elfcpp::R_386_16:
case elfcpp::R_386_PC16:
case elfcpp::R_386_8:
case elfcpp::R_386_PC8:
{
bool is_pcrel = (r_type == elfcpp::R_386_PC32
|| r_type == elfcpp::R_386_PC16
|| r_type == elfcpp::R_386_PC8);
if (gsym->is_from_dynobj()
|| (parameters->output_is_shared()
&& gsym->is_preemptible()))
{
// (a) This symbol is defined in a dynamic object. If it is a
// function, we make a PLT entry. Otherwise we need to
// either generate a COPY reloc or copy this reloc.
// (b) We are building a shared object and this symbol is
// preemptible. If it is a function, we make a PLT entry.
// Otherwise, we copy the reloc.
if (gsym->type() == elfcpp::STT_FUNC)
{
target->make_plt_entry(symtab, layout, gsym);
// If this is not a PC relative reference, then we may
// be taking the address of the function. In that case
// we need to set the entry in the dynamic symbol table
// to the address of the PLT entry. We will also need to
// create a dynamic relocation.
if (!is_pcrel)
{
if (gsym->is_from_dynobj())
gsym->set_needs_dynsym_value();
if (parameters->output_is_position_independent())
{
Reloc_section* rel_dyn =
target->rel_dyn_section(layout);
rel_dyn->add_global(gsym, r_type, object, data_shndx,
reloc.get_r_offset());
}
}
}
else if (parameters->output_is_shared())
{
// We do not make COPY relocs in shared objects.
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
rel_dyn->add_global(gsym, r_type, object, data_shndx,
reloc.get_r_offset());
}
else
target->copy_reloc(&options, symtab, layout, object, data_shndx,
gsym, reloc);
}
else if (!is_pcrel && parameters->output_is_position_independent())
{
// This is not a PC-relative reference, so we need to generate
// a dynamic relocation. At this point, we know the symbol
// is not preemptible, so we can use the RELATIVE relocation.
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
if (r_type == elfcpp::R_386_32)
rel_dyn->add_local(object, 0, elfcpp::R_386_RELATIVE, data_shndx,
reloc.get_r_offset());
else
rel_dyn->add_global(gsym, r_type, object, data_shndx,
reloc.get_r_offset());
}
}
break;
case elfcpp::R_386_GOT32:
{
// The symbol requires a GOT entry.
Output_data_got<32, false>* got = target->got_section(symtab, layout);
if (got->add_global(gsym))
{
// If this symbol is not fully resolved, we need to add a
// dynamic relocation for it.
if (!gsym->final_value_is_known())
{
Reloc_section* rel_dyn = target->rel_dyn_section(layout);
rel_dyn->add_global(gsym, elfcpp::R_386_GLOB_DAT, got,
gsym->got_offset());
}
}
}
break;
case elfcpp::R_386_PLT32:
// If the symbol is fully resolved, this is just a PC32 reloc.
// Otherwise we need a PLT entry.
if (gsym->final_value_is_known())
break;
// If building a shared library, we can also skip the PLT entry
// if the symbol is defined in the output file and is protected
// or hidden.
if (gsym->is_defined()
&& !gsym->is_from_dynobj()
&& !gsym->is_preemptible())
break;
target->make_plt_entry(symtab, layout, gsym);
break;
case elfcpp::R_386_GOTOFF:
case elfcpp::R_386_GOTPC:
// We need a GOT section.
target->got_section(symtab, layout);
break;
// These are relocations which should only be seen by the
// dynamic linker, and should never be seen here.
case elfcpp::R_386_COPY:
case elfcpp::R_386_GLOB_DAT:
case elfcpp::R_386_JUMP_SLOT:
case elfcpp::R_386_RELATIVE:
case elfcpp::R_386_TLS_TPOFF:
case elfcpp::R_386_TLS_DTPMOD32:
case elfcpp::R_386_TLS_DTPOFF32:
case elfcpp::R_386_TLS_TPOFF32:
case elfcpp::R_386_TLS_DESC:
gold_error(_("%s: unexpected reloc %u in object file"),
object->name().c_str(), r_type);
break;
// These are initial tls relocs, which are expected when
// linking.
case elfcpp::R_386_TLS_GD: // Global-dynamic
case elfcpp::R_386_TLS_GOTDESC: // Global-dynamic (from ~oliva url)
case elfcpp::R_386_TLS_DESC_CALL:
case elfcpp::R_386_TLS_LDM: // Local-dynamic
case elfcpp::R_386_TLS_LDO_32: // Alternate local-dynamic
case elfcpp::R_386_TLS_IE: // Initial-exec
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_LE: // Local-exec
case elfcpp::R_386_TLS_LE_32:
{
const bool is_final = gsym->final_value_is_known();
const tls::Tls_optimization optimized_type
= Target_i386::optimize_tls_reloc(is_final, r_type);
switch (r_type)
{
case elfcpp::R_386_TLS_GD: // Global-dynamic
case elfcpp::R_386_TLS_GOTDESC: // Global-dynamic (~oliva url)
case elfcpp::R_386_TLS_DESC_CALL:
// FIXME: If not relaxing to LE, we need to generate
// DTPMOD32 and DTPOFF32 relocs.
if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_global(object, r_type, gsym);
break;
case elfcpp::R_386_TLS_LDM: // Local-dynamic
// FIXME: If not relaxing to LE, we need to generate a
// DTPMOD32 reloc.
if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_global(object, r_type, gsym);
break;
case elfcpp::R_386_TLS_LDO_32: // Alternate local-dynamic
break;
case elfcpp::R_386_TLS_IE: // Initial-exec
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTIE:
// FIXME: If not relaxing to LE, we need to generate a
// TPOFF or TPOFF32 reloc.
if (optimized_type != tls::TLSOPT_TO_LE)
unsupported_reloc_global(object, r_type, gsym);
break;
case elfcpp::R_386_TLS_LE: // Local-exec
case elfcpp::R_386_TLS_LE_32:
// FIXME: If generating a shared object, we need to copy
// this relocation into the object.
gold_assert(!parameters->output_is_shared());
break;
default:
gold_unreachable();
}
}
break;
case elfcpp::R_386_32PLT:
case elfcpp::R_386_TLS_GD_32:
case elfcpp::R_386_TLS_GD_PUSH:
case elfcpp::R_386_TLS_GD_CALL:
case elfcpp::R_386_TLS_GD_POP:
case elfcpp::R_386_TLS_LDM_32:
case elfcpp::R_386_TLS_LDM_PUSH:
case elfcpp::R_386_TLS_LDM_CALL:
case elfcpp::R_386_TLS_LDM_POP:
case elfcpp::R_386_USED_BY_INTEL_200:
default:
unsupported_reloc_global(object, r_type, gsym);
break;
}
}
// Scan relocations for a section.
void
Target_i386::scan_relocs(const General_options& options,
Symbol_table* symtab,
Layout* layout,
Sized_relobj<32, false>* object,
unsigned int data_shndx,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
size_t local_symbol_count,
const unsigned char* plocal_symbols,
Symbol** global_symbols)
{
if (sh_type == elfcpp::SHT_RELA)
{
gold_error(_("%s: unsupported RELA reloc section"),
object->name().c_str());
return;
}
gold::scan_relocs<32, false, Target_i386, elfcpp::SHT_REL,
Target_i386::Scan>(
options,
symtab,
layout,
this,
object,
data_shndx,
prelocs,
reloc_count,
local_symbol_count,
plocal_symbols,
global_symbols);
}
// Finalize the sections.
void
Target_i386::do_finalize_sections(Layout* layout)
{
// Fill in some more dynamic tags.
Output_data_dynamic* const odyn = layout->dynamic_data();
if (odyn != NULL)
{
if (this->got_plt_ != NULL)
odyn->add_section_address(elfcpp::DT_PLTGOT, this->got_plt_);
if (this->plt_ != NULL)
{
const Output_data* od = this->plt_->rel_plt();
odyn->add_section_size(elfcpp::DT_PLTRELSZ, od);
odyn->add_section_address(elfcpp::DT_JMPREL, od);
odyn->add_constant(elfcpp::DT_PLTREL, elfcpp::DT_REL);
}
if (this->rel_dyn_ != NULL)
{
const Output_data* od = this->rel_dyn_;
odyn->add_section_address(elfcpp::DT_REL, od);
odyn->add_section_size(elfcpp::DT_RELSZ, od);
odyn->add_constant(elfcpp::DT_RELENT,
elfcpp::Elf_sizes<32>::rel_size);
}
if (!parameters->output_is_shared())
{
// The value of the DT_DEBUG tag is filled in by the dynamic
// linker at run time, and used by the debugger.
odyn->add_constant(elfcpp::DT_DEBUG, 0);
}
}
// Emit any relocs we saved in an attempt to avoid generating COPY
// relocs.
if (this->copy_relocs_ == NULL)
return;
if (this->copy_relocs_->any_to_emit())
{
Reloc_section* rel_dyn = this->rel_dyn_section(layout);
this->copy_relocs_->emit(rel_dyn);
}
delete this->copy_relocs_;
this->copy_relocs_ = NULL;
}
// Return whether a direct absolute static relocation needs to be applied.
// In cases where Scan::local() or Scan::global() has created
// a dynamic relocation other than R_386_RELATIVE, the addend
// of the relocation is carried in the data, and we must not
// apply the static relocation.
inline bool
Target_i386::Relocate::should_apply_static_reloc(const Sized_symbol<32>* gsym,
bool is_pcrel,
bool is_32bit)
{
// For local symbols, return FALSE if a non-RELATIVE dynamic
// relocation was created; return TRUE otherwise.
if (gsym == NULL)
return (!parameters->output_is_position_independent() || is_32bit);
// For global symbols, mimic the logic in Scan::global()
// to decide whether a non-RELATIVE dynamic relocation was
// created.
// FIXME: This is ugly. Try to refactor this logic so it can be
// shared by Scan::global() and Relocate::relocate().
if (gsym->is_from_dynobj()
|| (parameters->output_is_shared()
&& gsym->is_preemptible()))
{
if (gsym->type() == elfcpp::STT_FUNC)
{
if (!is_pcrel && parameters->output_is_position_independent())
return false;
}
else
return false;
}
else if (!is_pcrel && parameters->output_is_position_independent())
return is_32bit;
// For all other cases, return TRUE
return true;
}
// Perform a relocation.
inline bool
Target_i386::Relocate::relocate(const Relocate_info<32, false>* relinfo,
Target_i386* target,
size_t relnum,
const elfcpp::Rel<32, false>& rel,
unsigned int r_type,
const Sized_symbol<32>* gsym,
const Symbol_value<32>* psymval,
unsigned char* view,
elfcpp::Elf_types<32>::Elf_Addr address,
off_t view_size)
{
if (this->skip_call_tls_get_addr_)
{
if (r_type != elfcpp::R_386_PLT32
|| gsym == NULL
|| strcmp(gsym->name(), "___tls_get_addr") != 0)
gold_error_at_location(relinfo, relnum, rel.get_r_offset(),
_("missing expected TLS relocation"));
else
{
this->skip_call_tls_get_addr_ = false;
return false;
}
}
// Pick the value to use for symbols defined in shared objects.
Symbol_value<32> symval;
if (gsym != NULL
&& (gsym->is_from_dynobj()
|| (parameters->output_is_shared()
&& gsym->is_preemptible()))
&& gsym->has_plt_offset())
{
symval.set_output_value(target->plt_section()->address()
+ gsym->plt_offset());
psymval = &symval;
}
const Sized_relobj<32, false>* object = relinfo->object;
// Get the GOT offset if needed.
// The GOT pointer points to the end of the GOT section.
// We need to subtract the size of the GOT section to get
// the actual offset to use in the relocation.
bool have_got_offset = false;
unsigned int got_offset = 0;
switch (r_type)
{
case elfcpp::R_386_GOT32:
if (gsym != NULL)
{
gold_assert(gsym->has_got_offset());
got_offset = gsym->got_offset() - target->got_size();
}
else
{
unsigned int r_sym = elfcpp::elf_r_sym<32>(rel.get_r_info());
got_offset = object->local_got_offset(r_sym) - target->got_size();
}
have_got_offset = true;
break;
default:
break;
}
switch (r_type)
{
case elfcpp::R_386_NONE:
case elfcpp::R_386_GNU_VTINHERIT:
case elfcpp::R_386_GNU_VTENTRY:
break;
case elfcpp::R_386_32:
if (should_apply_static_reloc(gsym, false, true))
Relocate_functions<32, false>::rel32(view, object, psymval);
break;
case elfcpp::R_386_PC32:
if (should_apply_static_reloc(gsym, true, true))
Relocate_functions<32, false>::pcrel32(view, object, psymval, address);
break;
case elfcpp::R_386_16:
if (should_apply_static_reloc(gsym, false, false))
Relocate_functions<32, false>::rel16(view, object, psymval);
break;
case elfcpp::R_386_PC16:
if (should_apply_static_reloc(gsym, true, false))
Relocate_functions<32, false>::pcrel16(view, object, psymval, address);
break;
case elfcpp::R_386_8:
if (should_apply_static_reloc(gsym, false, false))
Relocate_functions<32, false>::rel8(view, object, psymval);
break;
case elfcpp::R_386_PC8:
if (should_apply_static_reloc(gsym, true, false))
Relocate_functions<32, false>::pcrel8(view, object, psymval, address);
break;
case elfcpp::R_386_PLT32:
gold_assert(gsym == NULL
|| gsym->has_plt_offset()
|| gsym->final_value_is_known());
Relocate_functions<32, false>::pcrel32(view, object, psymval, address);
break;
case elfcpp::R_386_GOT32:
gold_assert(have_got_offset);
Relocate_functions<32, false>::rel32(view, got_offset);
break;
case elfcpp::R_386_GOTOFF:
{
elfcpp::Elf_types<32>::Elf_Addr value;
value = (psymval->value(object, 0)
- target->got_plt_section()->address());
Relocate_functions<32, false>::rel32(view, value);
}
break;
case elfcpp::R_386_GOTPC:
{
elfcpp::Elf_types<32>::Elf_Addr value;
value = target->got_plt_section()->address();
Relocate_functions<32, false>::pcrel32(view, value, address);
}
break;
case elfcpp::R_386_COPY:
case elfcpp::R_386_GLOB_DAT:
case elfcpp::R_386_JUMP_SLOT:
case elfcpp::R_386_RELATIVE:
// These are outstanding tls relocs, which are unexpected when
// linking.
case elfcpp::R_386_TLS_TPOFF:
case elfcpp::R_386_TLS_DTPMOD32:
case elfcpp::R_386_TLS_DTPOFF32:
case elfcpp::R_386_TLS_TPOFF32:
case elfcpp::R_386_TLS_DESC:
gold_error_at_location(relinfo, relnum, rel.get_r_offset(),
_("unexpected reloc %u in object file"),
r_type);
break;
// These are initial tls relocs, which are expected when
// linking.
case elfcpp::R_386_TLS_GD: // Global-dynamic
case elfcpp::R_386_TLS_GOTDESC: // Global-dynamic (from ~oliva url)
case elfcpp::R_386_TLS_DESC_CALL:
case elfcpp::R_386_TLS_LDM: // Local-dynamic
case elfcpp::R_386_TLS_LDO_32: // Alternate local-dynamic
case elfcpp::R_386_TLS_IE: // Initial-exec
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_LE: // Local-exec
case elfcpp::R_386_TLS_LE_32:
this->relocate_tls(relinfo, relnum, rel, r_type, gsym, psymval, view,
address, view_size);
break;
case elfcpp::R_386_32PLT:
case elfcpp::R_386_TLS_GD_32:
case elfcpp::R_386_TLS_GD_PUSH:
case elfcpp::R_386_TLS_GD_CALL:
case elfcpp::R_386_TLS_GD_POP:
case elfcpp::R_386_TLS_LDM_32:
case elfcpp::R_386_TLS_LDM_PUSH:
case elfcpp::R_386_TLS_LDM_CALL:
case elfcpp::R_386_TLS_LDM_POP:
case elfcpp::R_386_USED_BY_INTEL_200:
default:
gold_error_at_location(relinfo, relnum, rel.get_r_offset(),
_("unsupported reloc %u"),
r_type);
break;
}
return true;
}
// Perform a TLS relocation.
inline void
Target_i386::Relocate::relocate_tls(const Relocate_info<32, false>* relinfo,
size_t relnum,
const elfcpp::Rel<32, false>& rel,
unsigned int r_type,
const Sized_symbol<32>* gsym,
const Symbol_value<32>* psymval,
unsigned char* view,
elfcpp::Elf_types<32>::Elf_Addr,
off_t view_size)
{
Output_segment* tls_segment = relinfo->layout->tls_segment();
if (tls_segment == NULL)
{
gold_error_at_location(relinfo, relnum, rel.get_r_offset(),
_("TLS reloc but no TLS segment"));
return;
}
elfcpp::Elf_types<32>::Elf_Addr value = psymval->value(relinfo->object, 0);
const bool is_final = (gsym == NULL
? !parameters->output_is_position_independent()
: gsym->final_value_is_known());
const tls::Tls_optimization optimized_type
= Target_i386::optimize_tls_reloc(is_final, r_type);
switch (r_type)
{
case elfcpp::R_386_TLS_GD: // Global-dynamic
if (optimized_type == tls::TLSOPT_TO_LE)
{
this->tls_gd_to_le(relinfo, relnum, tls_segment,
rel, r_type, value, view,
view_size);
break;
}
gold_error_at_location(relinfo, relnum, rel.get_r_offset(),
_("unsupported reloc %u"),
r_type);
break;
case elfcpp::R_386_TLS_GOTDESC: // Global-dynamic (from ~oliva url)
case elfcpp::R_386_TLS_DESC_CALL:
gold_error_at_location(relinfo, relnum, rel.get_r_offset(),
_("unsupported reloc %u"),
r_type);
break;
case elfcpp::R_386_TLS_LDM: // Local-dynamic
if (this->local_dynamic_type_ == LOCAL_DYNAMIC_SUN)
{
gold_error_at_location(relinfo, relnum, rel.get_r_offset(),
_("both SUN and GNU model "
"TLS relocations"));
break;
}
this->local_dynamic_type_ = LOCAL_DYNAMIC_GNU;
if (optimized_type == tls::TLSOPT_TO_LE)
{
this->tls_ld_to_le(relinfo, relnum, tls_segment, rel, r_type,
value, view, view_size);
break;
}
gold_error_at_location(relinfo, relnum, rel.get_r_offset(),
_("unsupported reloc %u"),
r_type);
break;
case elfcpp::R_386_TLS_LDO_32: // Alternate local-dynamic
// This reloc can appear in debugging sections, in which case we
// won't see the TLS_LDM reloc. The local_dynamic_type field
// tells us this.
if (optimized_type != tls::TLSOPT_TO_LE
|| this->local_dynamic_type_ == LOCAL_DYNAMIC_NONE)
value = value - tls_segment->vaddr();
else if (this->local_dynamic_type_ == LOCAL_DYNAMIC_GNU)
value = value - (tls_segment->vaddr() + tls_segment->memsz());
else
value = tls_segment->vaddr() + tls_segment->memsz() - value;
Relocate_functions<32, false>::rel32(view, value);
break;
case elfcpp::R_386_TLS_IE: // Initial-exec
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_IE_32:
if (optimized_type == tls::TLSOPT_TO_LE)
{
Target_i386::Relocate::tls_ie_to_le(relinfo, relnum, tls_segment,
rel, r_type, value, view,
view_size);
break;
}
gold_error_at_location(relinfo, relnum, rel.get_r_offset(),
_("unsupported reloc %u"),
r_type);
break;
case elfcpp::R_386_TLS_LE: // Local-exec
value = value - (tls_segment->vaddr() + tls_segment->memsz());
Relocate_functions<32, false>::rel32(view, value);
break;
case elfcpp::R_386_TLS_LE_32:
value = tls_segment->vaddr() + tls_segment->memsz() - value;
Relocate_functions<32, false>::rel32(view, value);
break;
}
}
// Do a relocation in which we convert a TLS General-Dynamic to a
// Local-Exec.
inline void
Target_i386::Relocate::tls_gd_to_le(const Relocate_info<32, false>* relinfo,
size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rel<32, false>& rel,
unsigned int,
elfcpp::Elf_types<32>::Elf_Addr value,
unsigned char* view,
off_t view_size)
{
// leal foo(,%reg,1),%eax; call ___tls_get_addr
// ==> movl %gs:0,%eax; subl $foo@tpoff,%eax
// leal foo(%reg),%eax; call ___tls_get_addr
// ==> movl %gs:0,%eax; subl $foo@tpoff,%eax
tls::check_range(relinfo, relnum, rel.get_r_offset(), view_size, -2);
tls::check_range(relinfo, relnum, rel.get_r_offset(), view_size, 9);
unsigned char op1 = view[-1];
unsigned char op2 = view[-2];
tls::check_tls(relinfo, relnum, rel.get_r_offset(),
op2 == 0x8d || op2 == 0x04);
tls::check_tls(relinfo, relnum, rel.get_r_offset(), view[4] == 0xe8);
int roff = 5;
if (op2 == 0x04)
{
tls::check_range(relinfo, relnum, rel.get_r_offset(), view_size, -3);
tls::check_tls(relinfo, relnum, rel.get_r_offset(), view[-3] == 0x8d);
tls::check_tls(relinfo, relnum, rel.get_r_offset(),
((op1 & 0xc7) == 0x05 && op1 != (4 << 3)));
memcpy(view - 3, "\x65\xa1\0\0\0\0\x81\xe8\0\0\0", 12);
}
else
{
tls::check_tls(relinfo, relnum, rel.get_r_offset(),
(op1 & 0xf8) == 0x80 && (op1 & 7) != 4);
if (static_cast<off_t>(rel.get_r_offset() + 9) < view_size
&& view[9] == 0x90)
{
// There is a trailing nop. Use the size byte subl.
memcpy(view - 2, "\x65\xa1\0\0\0\0\x81\xe8\0\0\0", 12);
roff = 6;
}
else
{
// Use the five byte subl.
memcpy(view - 2, "\x65\xa1\0\0\0\0\x2d\0\0\0", 11);
}
}
value = tls_segment->vaddr() + tls_segment->memsz() - value;
Relocate_functions<32, false>::rel32(view + roff, value);
// The next reloc should be a PLT32 reloc against __tls_get_addr.
// We can skip it.
this->skip_call_tls_get_addr_ = true;
}
// Do a relocation in which we convert a TLS Local-Dynamic to a
// Local-Exec.
inline void
Target_i386::Relocate::tls_ld_to_le(const Relocate_info<32, false>* relinfo,
size_t relnum,
Output_segment*,
const elfcpp::Rel<32, false>& rel,
unsigned int,
elfcpp::Elf_types<32>::Elf_Addr,
unsigned char* view,
off_t view_size)
{
// leal foo(%reg), %eax; call ___tls_get_addr
// ==> movl %gs:0,%eax; nop; leal 0(%esi,1),%esi
tls::check_range(relinfo, relnum, rel.get_r_offset(), view_size, -2);
tls::check_range(relinfo, relnum, rel.get_r_offset(), view_size, 9);
// FIXME: Does this test really always pass?
tls::check_tls(relinfo, relnum, rel.get_r_offset(),
view[-2] == 0x8d && view[-1] == 0x83);
tls::check_tls(relinfo, relnum, rel.get_r_offset(), view[4] == 0xe8);
memcpy(view - 2, "\x65\xa1\0\0\0\0\x90\x8d\x74\x26\0", 11);
// The next reloc should be a PLT32 reloc against __tls_get_addr.
// We can skip it.
this->skip_call_tls_get_addr_ = true;
}
// Do a relocation in which we convert a TLS Initial-Exec to a
// Local-Exec.
inline void
Target_i386::Relocate::tls_ie_to_le(const Relocate_info<32, false>* relinfo,
size_t relnum,
Output_segment* tls_segment,
const elfcpp::Rel<32, false>& rel,
unsigned int r_type,
elfcpp::Elf_types<32>::Elf_Addr value,
unsigned char* view,
off_t view_size)
{
// We have to actually change the instructions, which means that we
// need to examine the opcodes to figure out which instruction we
// are looking at.
if (r_type == elfcpp::R_386_TLS_IE)
{
// movl %gs:XX,%eax ==> movl $YY,%eax
// movl %gs:XX,%reg ==> movl $YY,%reg
// addl %gs:XX,%reg ==> addl $YY,%reg
tls::check_range(relinfo, relnum, rel.get_r_offset(), view_size, -1);
tls::check_range(relinfo, relnum, rel.get_r_offset(), view_size, 4);
unsigned char op1 = view[-1];
if (op1 == 0xa1)
{
// movl XX,%eax ==> movl $YY,%eax
view[-1] = 0xb8;
}
else
{
tls::check_range(relinfo, relnum, rel.get_r_offset(), view_size, -2);
unsigned char op2 = view[-2];
if (op2 == 0x8b)
{
// movl XX,%reg ==> movl $YY,%reg
tls::check_tls(relinfo, relnum, rel.get_r_offset(),
(op1 & 0xc7) == 0x05);
view[-2] = 0xc7;
view[-1] = 0xc0 | ((op1 >> 3) & 7);
}
else if (op2 == 0x03)
{
// addl XX,%reg ==> addl $YY,%reg
tls::check_tls(relinfo, relnum, rel.get_r_offset(),
(op1 & 0xc7) == 0x05);
view[-2] = 0x81;
view[-1] = 0xc0 | ((op1 >> 3) & 7);
}
else
tls::check_tls(relinfo, relnum, rel.get_r_offset(), 0);
}
}
else
{
// subl %gs:XX(%reg1),%reg2 ==> subl $YY,%reg2
// movl %gs:XX(%reg1),%reg2 ==> movl $YY,%reg2
// addl %gs:XX(%reg1),%reg2 ==> addl $YY,$reg2
tls::check_range(relinfo, relnum, rel.get_r_offset(), view_size, -2);
tls::check_range(relinfo, relnum, rel.get_r_offset(), view_size, 4);
unsigned char op1 = view[-1];
unsigned char op2 = view[-2];
tls::check_tls(relinfo, relnum, rel.get_r_offset(),
(op1 & 0xc0) == 0x80 && (op1 & 7) != 4);
if (op2 == 0x8b)
{
// movl %gs:XX(%reg1),%reg2 ==> movl $YY,%reg2
view[-2] = 0xc7;
view[-1] = 0xc0 | ((op1 >> 3) & 7);
}
else if (op2 == 0x2b)
{
// subl %gs:XX(%reg1),%reg2 ==> subl $YY,%reg2
view[-2] = 0x81;
view[-1] = 0xe8 | ((op1 >> 3) & 7);
}
else if (op2 == 0x03)
{
// addl %gs:XX(%reg1),%reg2 ==> addl $YY,$reg2
view[-2] = 0x81;
view[-1] = 0xc0 | ((op1 >> 3) & 7);
}
else
tls::check_tls(relinfo, relnum, rel.get_r_offset(), 0);
}
value = tls_segment->vaddr() + tls_segment->memsz() - value;
if (r_type == elfcpp::R_386_TLS_IE || r_type == elfcpp::R_386_TLS_GOTIE)
value = - value;
Relocate_functions<32, false>::rel32(view, value);
}
// Relocate section data.
void
Target_i386::relocate_section(const Relocate_info<32, false>* relinfo,
unsigned int sh_type,
const unsigned char* prelocs,
size_t reloc_count,
unsigned char* view,
elfcpp::Elf_types<32>::Elf_Addr address,
off_t view_size)
{
gold_assert(sh_type == elfcpp::SHT_REL);
gold::relocate_section<32, false, Target_i386, elfcpp::SHT_REL,
Target_i386::Relocate>(
relinfo,
this,
prelocs,
reloc_count,
view,
address,
view_size);
}
// Return the value to use for a dynamic which requires special
// treatment. This is how we support equality comparisons of function
// pointers across shared library boundaries, as described in the
// processor specific ABI supplement.
uint64_t
Target_i386::do_dynsym_value(const Symbol* gsym) const
{
gold_assert(gsym->is_from_dynobj() && gsym->has_plt_offset());
return this->plt_section()->address() + gsym->plt_offset();
}
// Return a string used to fill a code section with nops to take up
// the specified length.
std::string
Target_i386::do_code_fill(off_t length)
{
if (length >= 16)
{
// Build a jmp instruction to skip over the bytes.
unsigned char jmp[5];
jmp[0] = 0xe9;
elfcpp::Swap_unaligned<32, false>::writeval(jmp + 1, length - 5);
return (std::string(reinterpret_cast<char*>(&jmp[0]), 5)
+ std::string(length - 5, '\0'));
}
// Nop sequences of various lengths.
const char nop1[1] = { 0x90 }; // nop
const char nop2[2] = { 0x66, 0x90 }; // xchg %ax %ax
const char nop3[3] = { 0x8d, 0x76, 0x00 }; // leal 0(%esi),%esi
const char nop4[4] = { 0x8d, 0x74, 0x26, 0x00}; // leal 0(%esi,1),%esi
const char nop5[5] = { 0x90, 0x8d, 0x74, 0x26, // nop
0x00 }; // leal 0(%esi,1),%esi
const char nop6[6] = { 0x8d, 0xb6, 0x00, 0x00, // leal 0L(%esi),%esi
0x00, 0x00 };
const char nop7[7] = { 0x8d, 0xb4, 0x26, 0x00, // leal 0L(%esi,1),%esi
0x00, 0x00, 0x00 };
const char nop8[8] = { 0x90, 0x8d, 0xb4, 0x26, // nop
0x00, 0x00, 0x00, 0x00 }; // leal 0L(%esi,1),%esi
const char nop9[9] = { 0x89, 0xf6, 0x8d, 0xbc, // movl %esi,%esi
0x27, 0x00, 0x00, 0x00, // leal 0L(%edi,1),%edi
0x00 };
const char nop10[10] = { 0x8d, 0x76, 0x00, 0x8d, // leal 0(%esi),%esi
0xbc, 0x27, 0x00, 0x00, // leal 0L(%edi,1),%edi
0x00, 0x00 };
const char nop11[11] = { 0x8d, 0x74, 0x26, 0x00, // leal 0(%esi,1),%esi
0x8d, 0xbc, 0x27, 0x00, // leal 0L(%edi,1),%edi
0x00, 0x00, 0x00 };
const char nop12[12] = { 0x8d, 0xb6, 0x00, 0x00, // leal 0L(%esi),%esi
0x00, 0x00, 0x8d, 0xbf, // leal 0L(%edi),%edi
0x00, 0x00, 0x00, 0x00 };
const char nop13[13] = { 0x8d, 0xb6, 0x00, 0x00, // leal 0L(%esi),%esi
0x00, 0x00, 0x8d, 0xbc, // leal 0L(%edi,1),%edi
0x27, 0x00, 0x00, 0x00,
0x00 };
const char nop14[14] = { 0x8d, 0xb4, 0x26, 0x00, // leal 0L(%esi,1),%esi
0x00, 0x00, 0x00, 0x8d, // leal 0L(%edi,1),%edi
0xbc, 0x27, 0x00, 0x00,
0x00, 0x00 };
const char nop15[15] = { 0xeb, 0x0d, 0x90, 0x90, // jmp .+15
0x90, 0x90, 0x90, 0x90, // nop,nop,nop,...
0x90, 0x90, 0x90, 0x90,
0x90, 0x90, 0x90 };
const char* nops[16] = {
NULL,
nop1, nop2, nop3, nop4, nop5, nop6, nop7,
nop8, nop9, nop10, nop11, nop12, nop13, nop14, nop15
};
return std::string(nops[length], length);
}
// The selector for i386 object files.
class Target_selector_i386 : public Target_selector
{
public:
Target_selector_i386()
: Target_selector(elfcpp::EM_386, 32, false)
{ }
Target*
recognize(int machine, int osabi, int abiversion);
private:
Target_i386* target_;
};
// Recognize an i386 object file when we already know that the machine
// number is EM_386.
Target*
Target_selector_i386::recognize(int, int, int)
{
if (this->target_ == NULL)
this->target_ = new Target_i386();
return this->target_;
}
Target_selector_i386 target_selector_i386;
} // End anonymous namespace.
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