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16649710df
binutils-gdb/gold/i386.cc
Ian Lance Taylor 16649710df Can now dynamically link hello, world.
2006-12-01 16:51:25 +00:00

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// i386.cc -- i386 target support for gold.
#include "gold.h"
#include <cstring>
#include "elfcpp.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"
namespace
{
using namespace gold;
class Output_data_plt_i386;
// The i386 target class.
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(const General_options*, Layout*);
// 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);
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);
};
// The class which implements relocation.
class Relocate
{
public:
Relocate()
: skip_call_tls_get_addr_(false)
{ }
~Relocate()
{
if (this->skip_call_tls_get_addr_)
{
// FIXME: This needs to specify the location somehow.
fprintf(stderr, _("%s: missing expected TLS relocation\n"),
program_name);
gold_exit(false);
}
}
// 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>*,
elfcpp::Elf_types<32>::Elf_Addr,
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>*,
elfcpp::Elf_types<32>::Elf_Addr,
unsigned char*, elfcpp::Elf_types<32>::Elf_Addr, off_t);
// 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);
// Do a TLS Global-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);
// Check the range for a TLS relocation.
static inline void
check_range(const Relocate_info<32, false>*, size_t relnum,
const elfcpp::Rel<32, false>&, off_t, off_t);
// Check the validity of a TLS relocation. This is like assert.
static inline void
check_tls(const Relocate_info<32, false>*, size_t relnum,
const elfcpp::Rel<32, false>&, bool);
// 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_;
};
// Adjust TLS relocation type based on the options and whether this
// is a local symbol.
static unsigned int
optimize_tls_reloc(const General_options*, bool is_final, int r_type);
// Get the GOT section, creating it if necessary.
Output_data_got<32, false>*
got_section(const General_options*, Symbol_table*, Layout*);
// Create a PLT entry for a global symbol.
void
make_plt_entry(const General_options* options, Symbol_table*,
Layout*, Symbol*);
// Get the PLT section.
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
"/usr/lib/libc.so.1", // dynamic_linker
0x08048000, // 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(const General_options* options, Symbol_table* symtab,
Layout* layout)
{
if (this->got_ == NULL)
{
gold_assert(options != NULL && symtab != NULL && layout != NULL);
this->got_ = new Output_data_got<32, false>(options);
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_",
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*, bool is_shared);
// 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_;
// Whether we are generated a shared object.
bool is_shared_;
};
// 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,
bool is_shared)
: Output_section_data(4), got_plt_(got_plt), is_shared_(is_shared)
{
this->rel_ = new Reloc_section();
layout->add_output_section_data(".rel.plt", elfcpp::SHT_REL,
elfcpp::SHF_ALLOC, this->rel_);
}
// For some reason
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 (this->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 (this->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(const General_options* options,
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(options, symtab, layout);
this->plt_ = new Output_data_plt_i386(layout, this->got_plt_,
options->is_shared());
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);
// Define the symbol in the .dynbss section.
symtab->define_in_output_data(this, ssym->name(), dynbss, offset,
symsize, ssym->type(), ssym->binding(),
ssym->visibility(), ssym->nonvis(),
false, false);
// Add the COPY reloc.
ssym->set_needs_dynsym_entry();
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.
unsigned int
Target_i386::optimize_tls_reloc(const General_options* options,
bool is_final,
int r_type)
{
// If we are generating a shared library, then we can't do anything
// in the linker.
if (options->is_shared())
return r_type;
switch (r_type)
{
case elfcpp::R_386_TLS_GD:
case elfcpp::R_386_TLS_GOTDESC:
case elfcpp::R_386_TLS_DESC_CALL:
// These are Global-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 elfcpp::R_386_TLS_LE_32;
return elfcpp::R_386_TLS_IE_32;
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 elfcpp::R_386_TLS_LE_32;
case elfcpp::R_386_TLS_LDO_32:
// Another type of Local-Dynamic relocation.
return elfcpp::R_386_TLS_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 elfcpp::R_386_TLS_LE_32;
return r_type;
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 r_type;
default:
gold_unreachable();
}
}
// Scan a relocation for a local symbol.
inline void
Target_i386::Scan::local(const General_options& options,
Symbol_table* symtab,
Layout* layout,
Target_i386* target,
Sized_relobj<32, false>* object,
unsigned int,
const elfcpp::Rel<32, false>&,
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:
// FIXME: If we are generating a shared object we need to copy
// this relocation into the object.
gold_assert(!options.is_shared());
break;
case elfcpp::R_386_PC32:
case elfcpp::R_386_PC16:
case elfcpp::R_386_PC8:
break;
case elfcpp::R_386_GOTOFF:
case elfcpp::R_386_GOTPC:
// We need a GOT section.
target->got_section(&options, symtab, layout);
break;
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:
fprintf(stderr, _("%s: %s: unexpected reloc %u in object file\n"),
program_name, object->name().c_str(), r_type);
gold_exit(false);
break;
case elfcpp::R_386_TLS_IE:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_LE:
case elfcpp::R_386_TLS_GD:
case elfcpp::R_386_TLS_LDM:
case elfcpp::R_386_TLS_LDO_32:
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_LE_32:
case elfcpp::R_386_TLS_GOTDESC:
case elfcpp::R_386_TLS_DESC_CALL:
r_type = Target_i386::optimize_tls_reloc(&options,
!options.is_shared(),
r_type);
switch (r_type)
{
case elfcpp::R_386_TLS_LE:
case elfcpp::R_386_TLS_LE_32:
// FIXME: If generating a shared object, we need to copy
// this relocation into the object.
gold_assert(!options.is_shared());
break;
case elfcpp::R_386_TLS_IE:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_GD:
case elfcpp::R_386_TLS_LDM:
case elfcpp::R_386_TLS_LDO_32:
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTDESC:
case elfcpp::R_386_TLS_DESC_CALL:
fprintf(stderr,
_("%s: %s: unsupported reloc %u against local symbol\n"),
program_name, object->name().c_str(), r_type);
break;
}
break;
case elfcpp::R_386_GOT32:
case elfcpp::R_386_PLT32:
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:
fprintf(stderr, _("%s: %s: unsupported reloc %u against local symbol\n"),
program_name, object->name().c_str(), r_type);
break;
}
}
// 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:
// FIXME: If we are generating a shared object we may need to
// copy this relocation into the object. If this symbol is
// defined in a shared object, we may need to copy this
// relocation in order to avoid a COPY relocation.
gold_assert(!options.is_shared());
if (gsym->is_defined_in_dynobj())
{
// 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.
if (gsym->type() == elfcpp::STT_FUNC)
target->make_plt_entry(&options, symtab, layout, gsym);
else
target->copy_reloc(&options, symtab, layout, object, data_shndx,
gsym, reloc);
}
break;
case elfcpp::R_386_GOT32:
// The symbol requires a GOT entry.
if (target->got_section(&options, symtab, layout)->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(&options))
gold_unreachable();
}
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(&options))
break;
target->make_plt_entry(&options, symtab, layout, gsym);
break;
case elfcpp::R_386_GOTOFF:
case elfcpp::R_386_GOTPC:
// We need a GOT section.
target->got_section(&options, symtab, layout);
break;
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:
fprintf(stderr, _("%s: %s: unexpected reloc %u in object file\n"),
program_name, object->name().c_str(), r_type);
gold_exit(false);
break;
case elfcpp::R_386_TLS_IE:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_LE:
case elfcpp::R_386_TLS_GD:
case elfcpp::R_386_TLS_LDM:
case elfcpp::R_386_TLS_LDO_32:
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_LE_32:
case elfcpp::R_386_TLS_GOTDESC:
case elfcpp::R_386_TLS_DESC_CALL:
{
const bool is_final = gsym->final_value_is_known(&options);
r_type = Target_i386::optimize_tls_reloc(&options, is_final, r_type);
switch (r_type)
{
case elfcpp::R_386_TLS_LE:
case elfcpp::R_386_TLS_LE_32:
// FIXME: If generating a shared object, we need to copy
// this relocation into the object.
gold_assert(!options.is_shared());
break;
case elfcpp::R_386_TLS_IE:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_GD:
case elfcpp::R_386_TLS_LDM:
case elfcpp::R_386_TLS_LDO_32:
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_GOTDESC:
case elfcpp::R_386_TLS_DESC_CALL:
fprintf(stderr,
_("%s: %s: unsupported reloc %u "
"against global symbol %s\n"),
program_name, object->name().c_str(), r_type,
gsym->name());
break;
}
}
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:
fprintf(stderr,
_("%s: %s: unsupported reloc %u against global symbol %s\n"),
program_name, object->name().c_str(), r_type, gsym->name());
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)
{
fprintf(stderr, _("%s: %s: unsupported RELA reloc section\n"),
program_name, object->name().c_str());
gold_exit(false);
}
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(const General_options* options,
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 (!options->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;
}
// 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,
elfcpp::Elf_types<32>::Elf_Addr value,
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)
{
fprintf(stderr, _("%s: %s: missing expected TLS relocation\n"),
program_name,
relinfo->location(relnum, rel.get_r_offset()).c_str());
gold_exit(false);
}
this->skip_call_tls_get_addr_ = false;
return false;
}
// Pick the value to use for symbols defined in shared objects.
if (gsym != NULL && gsym->is_defined_in_dynobj())
{
if (gsym->has_plt_offset())
value = target->plt_section()->address() + gsym->plt_offset();
else
gold_unreachable();
}
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:
Relocate_functions<32, false>::rel32(view, value);
break;
case elfcpp::R_386_PC32:
Relocate_functions<32, false>::pcrel32(view, value, address);
break;
case elfcpp::R_386_16:
Relocate_functions<32, false>::rel16(view, value);
break;
case elfcpp::R_386_PC16:
Relocate_functions<32, false>::pcrel16(view, value, address);
break;
case elfcpp::R_386_8:
Relocate_functions<32, false>::rel8(view, value);
break;
case elfcpp::R_386_PC8:
Relocate_functions<32, false>::pcrel8(view, value, address);
break;
case elfcpp::R_386_PLT32:
gold_assert(gsym->has_plt_offset()
|| gsym->final_value_is_known(relinfo->options));
Relocate_functions<32, false>::pcrel32(view, value, address);
break;
case elfcpp::R_386_GOT32:
// Local GOT offsets not yet supported.
gold_assert(gsym);
gold_assert(gsym->has_got_offset());
value = gsym->got_offset();
Relocate_functions<32, false>::rel32(view, value);
break;
case elfcpp::R_386_GOTOFF:
value -= target->got_section(NULL, NULL, NULL)->address();
Relocate_functions<32, false>::rel32(view, value);
break;
case elfcpp::R_386_GOTPC:
value = target->got_section(NULL, NULL, NULL)->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:
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:
fprintf(stderr, _("%s: %s: unexpected reloc %u in object file\n"),
program_name,
relinfo->location(relnum, rel.get_r_offset()).c_str(),
r_type);
gold_exit(false);
break;
case elfcpp::R_386_TLS_IE:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_LE:
case elfcpp::R_386_TLS_GD:
case elfcpp::R_386_TLS_LDM:
case elfcpp::R_386_TLS_LDO_32:
case elfcpp::R_386_TLS_IE_32:
case elfcpp::R_386_TLS_LE_32:
case elfcpp::R_386_TLS_GOTDESC:
case elfcpp::R_386_TLS_DESC_CALL:
this->relocate_tls(relinfo, relnum, rel, r_type, gsym, value, 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:
fprintf(stderr, _("%s: %s: unsupported reloc %u\n"),
program_name,
relinfo->location(relnum, rel.get_r_offset()).c_str(),
r_type);
// gold_exit(false);
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,
elfcpp::Elf_types<32>::Elf_Addr value,
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)
{
fprintf(stderr, _("%s: %s: TLS reloc but no TLS segment\n"),
program_name,
relinfo->location(relnum, rel.get_r_offset()).c_str());
gold_exit(false);
}
const bool is_final = (gsym == NULL
? !relinfo->options->is_shared()
: gsym->final_value_is_known(relinfo->options));
const unsigned int opt_r_type =
Target_i386::optimize_tls_reloc(relinfo->options, is_final, r_type);
switch (r_type)
{
case elfcpp::R_386_TLS_LE_32:
value = tls_segment->vaddr() + tls_segment->memsz() - value;
Relocate_functions<32, false>::rel32(view, value);
break;
case elfcpp::R_386_TLS_LE:
value = value - (tls_segment->vaddr() + tls_segment->memsz());
Relocate_functions<32, false>::rel32(view, value);
break;
case elfcpp::R_386_TLS_IE:
case elfcpp::R_386_TLS_GOTIE:
case elfcpp::R_386_TLS_IE_32:
if (opt_r_type == elfcpp::R_386_TLS_LE_32)
{
Target_i386::Relocate::tls_ie_to_le(relinfo, relnum, tls_segment,
rel, r_type, value, view,
view_size);
break;
}
fprintf(stderr, _("%s: %s: unsupported reloc type %u\n"),
program_name,
relinfo->location(relnum, rel.get_r_offset()).c_str(),
r_type);
// gold_exit(false);
break;
case elfcpp::R_386_TLS_GD:
if (opt_r_type == elfcpp::R_386_TLS_LE_32)
{
this->tls_gd_to_le(relinfo, relnum, tls_segment,
rel, r_type, value, view,
view_size);
break;
}
fprintf(stderr, _("%s: %s: unsupported reloc %u\n"),
program_name,
relinfo->location(relnum, rel.get_r_offset()).c_str(),
r_type);
// gold_exit(false);
break;
case elfcpp::R_386_TLS_LDM:
case elfcpp::R_386_TLS_LDO_32:
case elfcpp::R_386_TLS_GOTDESC:
case elfcpp::R_386_TLS_DESC_CALL:
fprintf(stderr, _("%s: %s: unsupported reloc %u\n"),
program_name,
relinfo->location(relnum, rel.get_r_offset()).c_str(),
r_type);
// gold_exit(false);
break;
}
}
// 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
Target_i386::Relocate::check_range(relinfo, relnum, rel, view_size, -1);
Target_i386::Relocate::check_range(relinfo, relnum, rel, view_size, 4);
unsigned char op1 = view[-1];
if (op1 == 0xa1)
{
// movl XX,%eax ==> movl $YY,%eax
view[-1] = 0xb8;
}
else
{
Target_i386::Relocate::check_range(relinfo, relnum, rel,
view_size, -2);
unsigned char op2 = view[-2];
if (op2 == 0x8b)
{
// movl XX,%reg ==> movl $YY,%reg
Target_i386::Relocate::check_tls(relinfo, relnum, rel,
(op1 & 0xc7) == 0x05);
view[-2] = 0xc7;
view[-1] = 0xc0 | ((op1 >> 3) & 7);
}
else if (op2 == 0x03)
{
// addl XX,%reg ==> addl $YY,%reg
Target_i386::Relocate::check_tls(relinfo, relnum, rel,
(op1 & 0xc7) == 0x05);
view[-2] = 0x81;
view[-1] = 0xc0 | ((op1 >> 3) & 7);
}
else
Target_i386::Relocate::check_tls(relinfo, relnum, rel, 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
Target_i386::Relocate::check_range(relinfo, relnum, rel, view_size, -2);
Target_i386::Relocate::check_range(relinfo, relnum, rel, view_size, 4);
unsigned char op1 = view[-1];
unsigned char op2 = view[-2];
Target_i386::Relocate::check_tls(relinfo, relnum, rel,
(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
Target_i386::Relocate::check_tls(relinfo, relnum, rel, 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);
}
// Do a relocation in which we convert a TLS Global-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
Target_i386::Relocate::check_range(relinfo, relnum, rel, view_size, -2);
Target_i386::Relocate::check_range(relinfo, relnum, rel, view_size, 9);
unsigned char op1 = view[-1];
unsigned char op2 = view[-2];
Target_i386::Relocate::check_tls(relinfo, relnum, rel,
op2 == 0x8d || op2 == 0x04);
Target_i386::Relocate::check_tls(relinfo, relnum, rel,
view[4] == 0xe8);
int roff = 5;
if (op2 == 0x04)
{
Target_i386::Relocate::check_range(relinfo, relnum, rel, view_size, -3);
Target_i386::Relocate::check_tls(relinfo, relnum, rel,
view[-3] == 0x8d);
Target_i386::Relocate::check_tls(relinfo, relnum, rel,
((op1 & 0xc7) == 0x05
&& op1 != (4 << 3)));
memcpy(view - 3, "\x65\xa1\0\0\0\0\x81\xe8\0\0\0", 12);
}
else
{
Target_i386::Relocate::check_tls(relinfo, relnum, rel,
(op1 & 0xf8) == 0x80 && (op1 & 7) != 4);
if (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;
}
// Check the range for a TLS relocation.
inline void
Target_i386::Relocate::check_range(const Relocate_info<32, false>* relinfo,
size_t relnum,
const elfcpp::Rel<32, false>& rel,
off_t view_size, off_t off)
{
off_t offset = rel.get_r_offset() + off;
if (offset < 0 || offset > view_size)
{
fprintf(stderr, _("%s: %s: TLS relocation out of range\n"),
program_name,
relinfo->location(relnum, rel.get_r_offset()).c_str());
gold_exit(false);
}
}
// Check the validity of a TLS relocation. This is like assert.
inline void
Target_i386::Relocate::check_tls(const Relocate_info<32, false>* relinfo,
size_t relnum,
const elfcpp::Rel<32, false>& rel,
bool valid)
{
if (!valid)
{
fprintf(stderr,
_("%s: %s: TLS relocation against invalid instruction\n"),
program_name,
relinfo->location(relnum, rel.get_r_offset()).c_str());
gold_exit(false);
}
}
// 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);
}
// 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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