1// target.cc -- target support for gold.
2
3// Copyright (C) 2009-2017 Free Software Foundation, Inc.
4// Written by Doug Kwan <dougkwan@google.com>.
5
6// This file is part of gold.
7
8// This program is free software; you can redistribute it and/or modify
9// it under the terms of the GNU General Public License as published by
10// the Free Software Foundation; either version 3 of the License, or
11// (at your option) any later version.
12
13// This program is distributed in the hope that it will be useful,
14// but WITHOUT ANY WARRANTY; without even the implied warranty of
15// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16// GNU General Public License for more details.
17
18// You should have received a copy of the GNU General Public License
19// along with this program; if not, write to the Free Software
20// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21// MA 02110-1301, USA.
22
23#include "gold.h"
24#include "elfcpp.h"
25#include "dynobj.h"
26#include "symtab.h"
27#include "output.h"
28#include "target.h"
29
30namespace gold
31{
32
33// Return whether NAME is a local label name.  This is used to implement the
34// --discard-locals options and can be overridden by child classes to
35// implement system-specific behaviour.  The logic here is the same as that
36// in _bfd_elf_is_local_label_name().
37
38bool
39Target::do_is_local_label_name(const char* name) const
40{
41  // Normal local symbols start with ``.L''.
42  if (name[0] == '.' && name[1] == 'L')
43    return true;
44
45  // At least some SVR4 compilers (e.g., UnixWare 2.1 cc) generate
46  // DWARF debugging symbols starting with ``..''.
47  if (name[0] == '.' && name[1] == '.')
48    return true;
49
50  // gcc will sometimes generate symbols beginning with ``_.L_'' when
51  // emitting DWARF debugging output.  I suspect this is actually a
52  // small bug in gcc (it calls ASM_OUTPUT_LABEL when it should call
53  // ASM_GENERATE_INTERNAL_LABEL, and this causes the leading
54  // underscore to be emitted on some ELF targets).  For ease of use,
55  // we treat such symbols as local.
56  if (name[0] == '_' && name[1] == '.' && name[2] == 'L' && name[3] == '_')
57    return true;
58
59  return false;
60}
61
62// Implementations of methods Target::do_make_elf_object are almost identical
63// except for the address sizes and endianities.  So we extract this
64// into a template.
65
66template<int size, bool big_endian>
67inline Object*
68Target::do_make_elf_object_implementation(
69    const std::string& name,
70    Input_file* input_file,
71    off_t offset,
72    const elfcpp::Ehdr<size, big_endian>& ehdr)
73{
74  int et = ehdr.get_e_type();
75  // ET_EXEC files are valid input for --just-symbols/-R,
76  // and we treat them as relocatable objects.
77  if (et == elfcpp::ET_REL
78      || (et == elfcpp::ET_EXEC && input_file->just_symbols()))
79    {
80      Sized_relobj_file<size, big_endian>* obj =
81	new Sized_relobj_file<size, big_endian>(name, input_file, offset, ehdr);
82      obj->setup();
83      return obj;
84    }
85  else if (et == elfcpp::ET_DYN)
86    {
87      Sized_dynobj<size, big_endian>* obj =
88	new Sized_dynobj<size, big_endian>(name, input_file, offset, ehdr);
89      obj->setup();
90      return obj;
91    }
92  else
93    {
94      gold_error(_("%s: unsupported ELF file type %d"),
95		 name.c_str(), et);
96      return NULL;
97    }
98}
99
100// Make an ELF object called NAME by reading INPUT_FILE at OFFSET.  EHDR
101// is the ELF header of the object.  There are four versions of this
102// for different address sizes and endianities.
103
104#ifdef HAVE_TARGET_32_LITTLE
105Object*
106Target::do_make_elf_object(const std::string& name, Input_file* input_file,
107			   off_t offset, const elfcpp::Ehdr<32, false>& ehdr)
108{
109  return this->do_make_elf_object_implementation<32, false>(name, input_file,
110							    offset, ehdr);
111}
112#endif
113
114#ifdef HAVE_TARGET_32_BIG
115Object*
116Target::do_make_elf_object(const std::string& name, Input_file* input_file,
117			   off_t offset, const elfcpp::Ehdr<32, true>& ehdr)
118{
119  return this->do_make_elf_object_implementation<32, true>(name, input_file,
120							   offset, ehdr);
121}
122#endif
123
124#ifdef HAVE_TARGET_64_LITTLE
125Object*
126Target::do_make_elf_object(const std::string& name, Input_file* input_file,
127			   off_t offset, const elfcpp::Ehdr<64, false>& ehdr)
128{
129  return this->do_make_elf_object_implementation<64, false>(name, input_file,
130							    offset, ehdr);
131}
132#endif
133
134#ifdef HAVE_TARGET_64_BIG
135Object*
136Target::do_make_elf_object(const std::string& name, Input_file* input_file,
137			   off_t offset, const elfcpp::Ehdr<64, true>& ehdr)
138{
139  return this->do_make_elf_object_implementation<64, true>(name, input_file,
140							   offset, ehdr);
141}
142#endif
143
144Output_section*
145Target::do_make_output_section(const char* name, elfcpp::Elf_Word type,
146			       elfcpp::Elf_Xword flags)
147{
148  return new Output_section(name, type, flags);
149}
150
151// Default for whether a reloc is a call to a non-split function is
152// whether the symbol is a function.
153
154bool
155Target::do_is_call_to_non_split(const Symbol* sym, const unsigned char*,
156				const unsigned char*, section_size_type) const
157{
158  return sym->type() == elfcpp::STT_FUNC;
159}
160
161// Default conversion for -fsplit-stack is to give an error.
162
163void
164Target::do_calls_non_split(Relobj* object, unsigned int, section_offset_type,
165			   section_size_type, const unsigned char*, size_t,
166			   unsigned char*, section_size_type,
167			   std::string*, std::string*) const
168{
169  static bool warned;
170  if (!warned)
171    {
172      gold_error(_("linker does not include stack split support "
173		   "required by %s"),
174		 object->name().c_str());
175      warned = true;
176    }
177}
178
179//  Return whether BYTES/LEN matches VIEW/VIEW_SIZE at OFFSET.
180
181bool
182Target::match_view(const unsigned char* view, section_size_type view_size,
183		   section_offset_type offset, const char* bytes,
184		   size_t len) const
185{
186  if (offset + len > view_size)
187    return false;
188  return memcmp(view + offset, bytes, len) == 0;
189}
190
191// Set the contents of a VIEW/VIEW_SIZE to nops starting at OFFSET
192// for LEN bytes.
193
194void
195Target::set_view_to_nop(unsigned char* view, section_size_type view_size,
196			section_offset_type offset, size_t len) const
197{
198  gold_assert(offset >= 0 && offset + len <= view_size);
199  if (!this->has_code_fill())
200    memset(view + offset, 0, len);
201  else
202    {
203      std::string fill = this->code_fill(len);
204      memcpy(view + offset, fill.data(), len);
205    }
206}
207
208// Return address and size to plug into eh_frame FDEs associated with a PLT.
209void
210Target::do_plt_fde_location(const Output_data* plt, unsigned char*,
211			    uint64_t* address, off_t* len) const
212{
213  *address = plt->address();
214  *len = plt->data_size();
215}
216
217// Class Sized_target.
218
219// Set the EI_OSABI field of the ELF header if requested.
220
221template<int size, bool big_endian>
222void
223Sized_target<size, big_endian>::do_adjust_elf_header(unsigned char* view,
224						     int len)
225{
226  elfcpp::ELFOSABI osabi = this->osabi();
227  if (osabi != elfcpp::ELFOSABI_NONE)
228    {
229      gold_assert(len == elfcpp::Elf_sizes<size>::ehdr_size);
230
231      elfcpp::Ehdr<size, big_endian> ehdr(view);
232      unsigned char e_ident[elfcpp::EI_NIDENT];
233      memcpy(e_ident, ehdr.get_e_ident(), elfcpp::EI_NIDENT);
234
235      e_ident[elfcpp::EI_OSABI] = osabi;
236
237      elfcpp::Ehdr_write<size, big_endian> oehdr(view);
238      oehdr.put_e_ident(e_ident);
239    }
240}
241
242#ifdef HAVE_TARGET_32_LITTLE
243template
244class Sized_target<32, false>;
245#endif
246
247#ifdef HAVE_TARGET_32_BIG
248template
249class Sized_target<32, true>;
250#endif
251
252#ifdef HAVE_TARGET_64_LITTLE
253template
254class Sized_target<64, false>;
255#endif
256
257#ifdef HAVE_TARGET_64_BIG
258template
259class Sized_target<64, true>;
260#endif
261
262} // End namespace gold.
263