diff options
Diffstat (limited to 'gold/i386.cc')
-rw-r--r-- | gold/i386.cc | 478 |
1 files changed, 409 insertions, 69 deletions
diff --git a/gold/i386.cc b/gold/i386.cc index e6522e3..488da79 100644 --- a/gold/i386.cc +++ b/gold/i386.cc @@ -20,6 +20,8 @@ namespace using namespace gold; +class Output_data_plt_i386; + // The i386 target class. class Target_i386 : public Sized_target<32, false> @@ -27,7 +29,7 @@ class Target_i386 : public Sized_target<32, false> public: Target_i386() : Sized_target<32, false>(&i386_info), - got_(NULL) + got_(NULL), plt_(NULL), got_plt_(NULL) { } // Scan the relocations to look for symbol adjustments. @@ -36,6 +38,7 @@ class Target_i386 : public Sized_target<32, false> 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, @@ -61,6 +64,7 @@ class Target_i386 : public Sized_target<32, false> 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); @@ -68,6 +72,7 @@ class Target_i386 : public Sized_target<32, false> 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); }; @@ -146,11 +151,29 @@ class Target_i386 : public Sized_target<32, false> // 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_local, int r_type); + 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(Symbol_table*, Layout*); + 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_; + } + + // Copy a relocation against a global symbol. + void + copy_reloc(const General_options*, 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. @@ -158,6 +181,10 @@ class Target_i386 : public Sized_target<32, false> // 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_; }; const Target::Target_info Target_i386::i386_info = @@ -176,37 +203,317 @@ const Target::Target_info Target_i386::i386_info = // Get the GOT section, creating it if necessary. Output_data_got<32, false>* -Target_i386::got_section(Symbol_table* symtab, Layout* layout) +Target_i386::got_section(const General_options* options, Symbol_table* symtab, + Layout* layout) { if (this->got_ == NULL) { - this->got_ = new Output_data_got<32, false>(); + gold_assert(options != NULL && symtab != NULL && layout != NULL); + + this->got_ = new Output_data_got<32, false>(options); - assert(symtab != NULL && layout != NULL); layout->add_output_section_data(".got", elfcpp::SHT_PROGBITS, elfcpp::SHF_ALLOC, 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, this->got_plt_); + // The first three entries are reserved. - this->got_->add_constant(0); - this->got_->add_constant(0); - this->got_->add_constant(0); + this->got_plt_->set_space_size(3 * 4); - // Define _GLOBAL_OFFSET_TABLE_ at the start of the section. - symtab->define_in_output_data(this, "_GLOBAL_OFFSET_TABLE_", this->got_, + // 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_GLOBAL, elfcpp::STV_HIDDEN, 0, false, false); } + return this->got_; } +// 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); + + 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_); +} + +// 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. + 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()); + } + + 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, + Sized_relobj<32, false>* object, + unsigned int data_shndx, Symbol* gsym, + const elfcpp::Rel<32, false>&) +{ + if (!Relocate_functions<32, false>::need_copy_reloc(options, object, + data_shndx, gsym)) + { + // So far we do not need a COPY reloc. Save this relocation. + // If it turns out that we never a COPY reloc for this symbol, + // then we emit the relocation. + } + +} + // Optimize the TLS relocation type based on what we know about the -// symbol. IS_LOCAL is true if this symbol can be resolved entirely -// locally--i.e., does not have to be in the dynamic symbol table. +// 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_local, +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 @@ -223,7 +530,7 @@ Target_i386::optimize_tls_reloc(const General_options* options, bool is_local, // 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_local) + if (is_final) return elfcpp::R_386_TLS_LE_32; return elfcpp::R_386_TLS_IE_32; @@ -244,7 +551,7 @@ Target_i386::optimize_tls_reloc(const General_options* options, bool is_local, // 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_local) + if (is_final) return elfcpp::R_386_TLS_LE_32; return r_type; @@ -255,7 +562,7 @@ Target_i386::optimize_tls_reloc(const General_options* options, bool is_local, return r_type; default: - abort(); + gold_unreachable(); } } @@ -267,7 +574,9 @@ Target_i386::Scan::local(const General_options& options, Layout* layout, Target_i386* target, Sized_relobj<32, false>* object, - const elfcpp::Rel<32, false>&, unsigned int r_type, + unsigned int, + const elfcpp::Rel<32, false>&, + unsigned int r_type, const elfcpp::Sym<32, false>&) { switch (r_type) @@ -282,6 +591,7 @@ Target_i386::Scan::local(const General_options& options, 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: @@ -292,7 +602,7 @@ Target_i386::Scan::local(const General_options& options, case elfcpp::R_386_GOTOFF: case elfcpp::R_386_GOTPC: // We need a GOT section. - target->got_section(symtab, layout); + target->got_section(&options, symtab, layout); break; case elfcpp::R_386_COPY: @@ -319,13 +629,16 @@ Target_i386::Scan::local(const General_options& options, 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, true, r_type); + 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: @@ -370,7 +683,9 @@ Target_i386::Scan::global(const General_options& options, Layout* layout, Target_i386* target, Sized_relobj<32, false>* object, - const elfcpp::Rel<32, false>&, unsigned int r_type, + unsigned int data_shndx, + const elfcpp::Rel<32, false>& reloc, + unsigned int r_type, Symbol* gsym) { switch (r_type) @@ -390,32 +705,44 @@ Target_i386::Scan::global(const General_options& options, // 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, object, data_shndx, gsym, reloc); + } + break; case elfcpp::R_386_GOT32: // The symbol requires a GOT entry. - if (target->got_section(symtab, layout)->add_global(gsym)) + if (target->got_section(&options, symtab, layout)->add_global(gsym)) { - // If this symbol is not resolved locally, we need to add a + // If this symbol is not fully resolved, we need to add a // dynamic relocation for it. - if (!gsym->is_resolved_locally()) - abort(); + if (!gsym->final_value_is_known(&options)) + gold_unreachable(); } break; case elfcpp::R_386_PLT32: - // If the symbol is resolved locally, this is just a PC32 reloc. - if (gsym->is_resolved_locally()) + // 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; - fprintf(stderr, - _("%s: %s: unsupported reloc %u against global symbol %s\n"), - program_name, object->name().c_str(), r_type, gsym->name()); + 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(symtab, layout); + target->got_section(&options, symtab, layout); break; case elfcpp::R_386_COPY: @@ -442,30 +769,34 @@ Target_i386::Scan::global(const General_options& options, 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, - gsym->is_resolved_locally(), - 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. - 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; - } + { + 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: @@ -493,6 +824,7 @@ 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, @@ -514,6 +846,7 @@ Target_i386::scan_relocs(const General_options& options, layout, this, object, + data_shndx, prelocs, reloc_count, local_symbol_count, @@ -552,6 +885,15 @@ Target_i386::Relocate::relocate(const Relocate_info<32, false>* relinfo, 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()) + address = target->plt_section()->address() + gsym->plt_offset(); + else + gold_unreachable(); + } + switch (r_type) { case elfcpp::R_386_NONE: @@ -584,30 +926,26 @@ Target_i386::Relocate::relocate(const Relocate_info<32, false>* relinfo, break; case elfcpp::R_386_PLT32: - if (gsym->is_resolved_locally()) - Relocate_functions<32, false>::pcrel32(view, value, address); - else - fprintf(stderr, _("%s: %s: unsupported reloc %u\n"), - program_name, - relinfo->location(relnum, rel.get_r_offset()).c_str(), - r_type); + 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. - assert(gsym); - assert(gsym->has_got_offset()); + 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)->address(); + 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)->address(); + value = target->got_section(NULL, NULL, NULL)->address(); Relocate_functions<32, false>::pcrel32(view, value, address); break; @@ -685,9 +1023,11 @@ Target_i386::Relocate::relocate_tls(const Relocate_info<32, false>* relinfo, gold_exit(false); } - const bool is_local = gsym == NULL || gsym->is_resolved_locally(); + 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_local, r_type); + Target_i386::optimize_tls_reloc(relinfo->options, is_final, r_type); switch (r_type) { case elfcpp::R_386_TLS_LE_32: @@ -955,7 +1295,7 @@ Target_i386::relocate_section(const Relocate_info<32, false>* relinfo, elfcpp::Elf_types<32>::Elf_Addr address, off_t view_size) { - assert(sh_type == elfcpp::SHT_REL); + gold_assert(sh_type == elfcpp::SHT_REL); gold::relocate_section<32, false, Target_i386, elfcpp::SHT_REL, Target_i386::Relocate>( |