* layout.cc (Layout::Layout): Initialize sections_are_attached_.
[deliverable/binutils-gdb.git] / gold / layout.cc
index 1591cfb5c9a5bdf0e20699ef4a0f862c97ae5b1f..76b6b2be8d109d544c84212e6ab3c0312a1749c0 100644 (file)
 
 #include "gold.h"
 
+#include <cerrno>
 #include <cstring>
 #include <algorithm>
 #include <iostream>
 #include <utility>
+#include <fcntl.h>
+#include <unistd.h>
+#include "libiberty.h"
+#include "md5.h"
+#include "sha1.h"
 
 #include "parameters.h"
 #include "options.h"
@@ -73,10 +79,12 @@ Layout::Layout(const General_options& options, Script_options* script_options)
   : options_(options), script_options_(script_options), namepool_(),
     sympool_(), dynpool_(), signatures_(),
     section_name_map_(), segment_list_(), section_list_(),
-    unattached_section_list_(), special_output_list_(),
-    section_headers_(NULL), tls_segment_(NULL), symtab_section_(NULL),
-    dynsym_section_(NULL), dynamic_section_(NULL), dynamic_data_(NULL),
-    eh_frame_section_(NULL), group_signatures_(), output_file_size_(-1),
+    unattached_section_list_(), sections_are_attached_(false),
+    special_output_list_(), section_headers_(NULL), tls_segment_(NULL),
+    symtab_section_(NULL), dynsym_section_(NULL), dynamic_section_(NULL),
+    dynamic_data_(NULL), eh_frame_section_(NULL), eh_frame_data_(NULL),
+    added_eh_frame_data_(false), eh_frame_hdr_section_(NULL),
+    build_id_note_(NULL), group_signatures_(), output_file_size_(-1),
     input_requires_executable_stack_(false),
     input_with_gnu_stack_note_(false),
     input_without_gnu_stack_note_(false),
@@ -226,7 +234,15 @@ Output_section*
 Layout::get_output_section(const char* name, Stringpool::Key name_key,
                           elfcpp::Elf_Word type, elfcpp::Elf_Xword flags)
 {
-  const Key key(name_key, std::make_pair(type, flags));
+  elfcpp::Elf_Xword lookup_flags = flags;
+
+  // Ignoring SHF_WRITE and SHF_EXECINSTR here means that we combine
+  // read-write with read-only sections.  Some other ELF linkers do
+  // not do this.  FIXME: Perhaps there should be an option
+  // controlling this.
+  lookup_flags &= ~(elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR);
+
+  const Key key(name_key, std::make_pair(type, lookup_flags));
   const std::pair<Key, Output_section*> v(key, NULL);
   std::pair<Section_name_map::iterator, bool> ins(
     this->section_name_map_.insert(v));
@@ -236,19 +252,34 @@ Layout::get_output_section(const char* name, Stringpool::Key name_key,
   else
     {
       // This is the first time we've seen this name/type/flags
-      // combination.  If the section has contents but no flags, then
-      // see whether we have an existing section with the same name.
-      // This is a workaround for cases where assembler code forgets
-      // to set section flags, and the GNU linker would simply pick an
-      // existing section with the same name.  FIXME: Perhaps there
-      // should be an option to control this.
+      // combination.  For compatibility with the GNU linker, we
+      // combine sections with contents and zero flags with sections
+      // with non-zero flags.  This is a workaround for cases where
+      // assembler code forgets to set section flags.  FIXME: Perhaps
+      // there should be an option to control this.
       Output_section* os = NULL;
-      if (type == elfcpp::SHT_PROGBITS && flags == 0)
+
+      if (type == elfcpp::SHT_PROGBITS)
        {
-         os = this->find_output_section(name);
-         if (os != NULL && os->type() != elfcpp::SHT_PROGBITS)
-           os = NULL;
+          if (flags == 0)
+            {
+              Output_section* same_name = this->find_output_section(name);
+              if (same_name != NULL
+                  && same_name->type() == elfcpp::SHT_PROGBITS
+                  && (same_name->flags() & elfcpp::SHF_TLS) == 0)
+                os = same_name;
+            }
+          else if ((flags & elfcpp::SHF_TLS) == 0)
+            {
+              elfcpp::Elf_Xword zero_flags = 0;
+              const Key zero_key(name_key, std::make_pair(type, zero_flags));
+              Section_name_map::iterator p =
+                  this->section_name_map_.find(zero_key);
+              if (p != this->section_name_map_.end())
+               os = p->second;
+            }
        }
+
       if (os == NULL)
        os = this->make_output_section(name, type, flags);
       ins.first->second = os;
@@ -258,17 +289,22 @@ Layout::get_output_section(const char* name, Stringpool::Key name_key,
 
 // Pick the output section to use for section NAME, in input file
 // RELOBJ, with type TYPE and flags FLAGS.  RELOBJ may be NULL for a
-// linker created section.  ADJUST_NAME is true if we should apply the
-// standard name mappings in Layout::output_section_name.  This will
-// return NULL if the input section should be discarded.
+// linker created section.  IS_INPUT_SECTION is true if we are
+// choosing an output section for an input section found in a input
+// file.  This will return NULL if the input section should be
+// discarded.
 
 Output_section*
 Layout::choose_output_section(const Relobj* relobj, const char* name,
                              elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
-                             bool adjust_name)
+                             bool is_input_section)
 {
-  // We should ignore some flags.  FIXME: This will need some
-  // adjustment for ld -r.
+  // We should not see any input sections after we have attached
+  // sections to segments.
+  gold_assert(!is_input_section || !this->sections_are_attached_);
+
+  // Some flags in the input section should not be automatically
+  // copied to the output section.
   flags &= ~ (elfcpp::SHF_INFO_LINK
              | elfcpp::SHF_LINK_ORDER
              | elfcpp::SHF_GROUP
@@ -319,7 +355,7 @@ Layout::choose_output_section(const Relobj* relobj, const char* name,
   // output section.
 
   size_t len = strlen(name);
-  if (adjust_name && !parameters->options().relocatable())
+  if (is_input_section && !parameters->options().relocatable())
     name = Layout::output_section_name(name, &len);
 
   Stringpool::Key name_key;
@@ -368,6 +404,17 @@ Layout::layout(Sized_relobj<size, big_endian>* object, unsigned int shndx,
        return NULL;
     }
 
+  // By default the GNU linker sorts input sections whose names match
+  // .ctor.*, .dtor.*, .init_array.*, or .fini_array.*.  The sections
+  // are sorted by name.  This is used to implement constructor
+  // priority ordering.  We are compatible.
+  if (!this->script_options_->saw_sections_clause()
+      && (is_prefix_of(".ctors.", name)
+         || is_prefix_of(".dtors.", name)
+         || is_prefix_of(".init_array.", name)
+         || is_prefix_of(".fini_array.", name)))
+    os->set_must_sort_attached_input_sections();
+
   // FIXME: Handle SHF_LINK_ORDER somewhere.
 
   *off = os->add_input_section(object, shndx, name, shdr, reloc_shndx,
@@ -491,7 +538,7 @@ Layout::layout_eh_frame(Sized_relobj<size, big_endian>* object,
                        off_t* off)
 {
   gold_assert(shdr.get_sh_type() == elfcpp::SHT_PROGBITS);
-  gold_assert(shdr.get_sh_flags() == elfcpp::SHF_ALLOC);
+  gold_assert((shdr.get_sh_flags() & elfcpp::SHF_ALLOC) != 0);
 
   const char* const name = ".eh_frame";
   Output_section* os = this->choose_output_section(object,
@@ -506,7 +553,6 @@ Layout::layout_eh_frame(Sized_relobj<size, big_endian>* object,
     {
       this->eh_frame_section_ = os;
       this->eh_frame_data_ = new Eh_frame();
-      os->add_output_section_data(this->eh_frame_data_);
 
       if (this->options_.eh_frame_hdr())
        {
@@ -548,7 +594,21 @@ Layout::layout_eh_frame(Sized_relobj<size, big_endian>* object,
                                                      shndx,
                                                      reloc_shndx,
                                                      reloc_type))
-    *off = -1;
+    {
+      os->update_flags_for_input_section(shdr.get_sh_flags());
+
+      // We found a .eh_frame section we are going to optimize, so now
+      // we can add the set of optimized sections to the output
+      // section.  We need to postpone adding this until we've found a
+      // section we can optimize so that the .eh_frame section in
+      // crtbegin.o winds up at the start of the output section.
+      if (!this->added_eh_frame_data_)
+       {
+         os->add_output_section_data(this->eh_frame_data_);
+         this->added_eh_frame_data_ = true;
+       }
+      *off = -1;
+    }
   else
     {
       // We couldn't handle this .eh_frame section for some reason.
@@ -620,96 +680,141 @@ Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
 
   this->section_list_.push_back(os);
 
-  if ((flags & elfcpp::SHF_ALLOC) == 0)
+  // The GNU linker by default sorts some sections by priority, so we
+  // do the same.  We need to know that this might happen before we
+  // attach any input sections.
+  if (!this->script_options_->saw_sections_clause()
+      && (strcmp(name, ".ctors") == 0
+         || strcmp(name, ".dtors") == 0
+         || strcmp(name, ".init_array") == 0
+         || strcmp(name, ".fini_array") == 0))
+    os->set_may_sort_attached_input_sections();
+
+  // If we have already attached the sections to segments, then we
+  // need to attach this one now.  This happens for sections created
+  // directly by the linker.
+  if (this->sections_are_attached_)
+    this->attach_section_to_segment(os);
+
+  return os;
+}
+
+// Attach output sections to segments.  This is called after we have
+// seen all the input sections.
+
+void
+Layout::attach_sections_to_segments()
+{
+  for (Section_list::iterator p = this->section_list_.begin();
+       p != this->section_list_.end();
+       ++p)
+    this->attach_section_to_segment(*p);
+
+  this->sections_are_attached_ = true;
+}
+
+// Attach an output section to a segment.
+
+void
+Layout::attach_section_to_segment(Output_section* os)
+{
+  if ((os->flags() & elfcpp::SHF_ALLOC) == 0)
     this->unattached_section_list_.push_back(os);
   else
-    {
-      if (parameters->options().relocatable())
-       return os;
+    this->attach_allocated_section_to_segment(os);
+}
 
-      // If we have a SECTIONS clause, we can't handle the attachment
-      // to segments until after we've seen all the sections.
-      if (this->script_options_->saw_sections_clause())
-       return os;
+// Attach an allocated output section to a segment.
 
-      gold_assert(!this->script_options_->saw_phdrs_clause());
+void
+Layout::attach_allocated_section_to_segment(Output_section* os)
+{
+  elfcpp::Elf_Xword flags = os->flags();
+  gold_assert((flags & elfcpp::SHF_ALLOC) != 0);
 
-      // This output section goes into a PT_LOAD segment.
+  if (parameters->options().relocatable())
+    return;
 
-      elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags);
+  // If we have a SECTIONS clause, we can't handle the attachment to
+  // segments until after we've seen all the sections.
+  if (this->script_options_->saw_sections_clause())
+    return;
 
-      // In general the only thing we really care about for PT_LOAD
-      // segments is whether or not they are writable, so that is how
-      // we search for them.  People who need segments sorted on some
-      // other basis will have to use a linker script.
+  gold_assert(!this->script_options_->saw_phdrs_clause());
 
-      Segment_list::const_iterator p;
-      for (p = this->segment_list_.begin();
-          p != this->segment_list_.end();
-          ++p)
-       {
-         if ((*p)->type() == elfcpp::PT_LOAD
-             && ((*p)->flags() & elfcpp::PF_W) == (seg_flags & elfcpp::PF_W))
-           {
-             // If -Tbss was specified, we need to separate the data
-             // and BSS segments.
-             if (this->options_.user_set_Tbss())
-               {
-                 if ((type == elfcpp::SHT_NOBITS)
-                     == (*p)->has_any_data_sections())
-                   continue;
-               }
+  // This output section goes into a PT_LOAD segment.
 
-             (*p)->add_output_section(os, seg_flags);
-             break;
-           }
-       }
+  elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags);
 
-      if (p == this->segment_list_.end())
-       {
-         Output_segment* oseg = this->make_output_segment(elfcpp::PT_LOAD,
-                                                          seg_flags);
-         oseg->add_output_section(os, seg_flags);
-       }
+  // In general the only thing we really care about for PT_LOAD
+  // segments is whether or not they are writable, so that is how we
+  // search for them.  People who need segments sorted on some other
+  // basis will have to use a linker script.
 
-      // If we see a loadable SHT_NOTE section, we create a PT_NOTE
-      // segment.
-      if (type == elfcpp::SHT_NOTE)
-       {
-         // See if we already have an equivalent PT_NOTE segment.
-         for (p = this->segment_list_.begin();
-              p != segment_list_.end();
-              ++p)
-           {
-             if ((*p)->type() == elfcpp::PT_NOTE
-                 && (((*p)->flags() & elfcpp::PF_W)
-                     == (seg_flags & elfcpp::PF_W)))
-               {
-                 (*p)->add_output_section(os, seg_flags);
-                 break;
-               }
-           }
+  Segment_list::const_iterator p;
+  for (p = this->segment_list_.begin();
+       p != this->segment_list_.end();
+       ++p)
+    {
+      if ((*p)->type() == elfcpp::PT_LOAD
+          && ((*p)->flags() & elfcpp::PF_W) == (seg_flags & elfcpp::PF_W))
+        {
+          // If -Tbss was specified, we need to separate the data
+          // and BSS segments.
+          if (this->options_.user_set_Tbss())
+            {
+              if ((os->type() == elfcpp::SHT_NOBITS)
+                  == (*p)->has_any_data_sections())
+                continue;
+            }
 
-         if (p == this->segment_list_.end())
-           {
-             Output_segment* oseg = this->make_output_segment(elfcpp::PT_NOTE,
-                                                              seg_flags);
-             oseg->add_output_section(os, seg_flags);
-           }
-       }
+          (*p)->add_output_section(os, seg_flags);
+          break;
+        }
+    }
 
-      // If we see a loadable SHF_TLS section, we create a PT_TLS
-      // segment.  There can only be one such segment.
-      if ((flags & elfcpp::SHF_TLS) != 0)
-       {
-         if (this->tls_segment_ == NULL)
-           this->tls_segment_ = this->make_output_segment(elfcpp::PT_TLS,
-                                                          seg_flags);
-         this->tls_segment_->add_output_section(os, seg_flags);
-       }
+  if (p == this->segment_list_.end())
+    {
+      Output_segment* oseg = this->make_output_segment(elfcpp::PT_LOAD,
+                                                       seg_flags);
+      oseg->add_output_section(os, seg_flags);
     }
 
-  return os;
+  // If we see a loadable SHT_NOTE section, we create a PT_NOTE
+  // segment.
+  if (os->type() == elfcpp::SHT_NOTE)
+    {
+      // See if we already have an equivalent PT_NOTE segment.
+      for (p = this->segment_list_.begin();
+           p != segment_list_.end();
+           ++p)
+        {
+          if ((*p)->type() == elfcpp::PT_NOTE
+              && (((*p)->flags() & elfcpp::PF_W)
+                  == (seg_flags & elfcpp::PF_W)))
+            {
+              (*p)->add_output_section(os, seg_flags);
+              break;
+            }
+        }
+
+      if (p == this->segment_list_.end())
+        {
+          Output_segment* oseg = this->make_output_segment(elfcpp::PT_NOTE,
+                                                           seg_flags);
+          oseg->add_output_section(os, seg_flags);
+        }
+    }
+
+  // If we see a loadable SHF_TLS section, we create a PT_TLS
+  // segment.  There can only be one such segment.
+  if ((flags & elfcpp::SHF_TLS) != 0)
+    {
+      if (this->tls_segment_ == NULL)
+        this->tls_segment_ = this->make_output_segment(elfcpp::PT_TLS,
+                                                       seg_flags);
+      this->tls_segment_->add_output_section(os, seg_flags);
+    }
 }
 
 // Make an output section for a script.
@@ -936,6 +1041,7 @@ Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab,
 
   this->create_gold_note();
   this->create_executable_stack_info(target);
+  this->create_build_id();
 
   Output_segment* phdr_seg = NULL;
   if (!parameters->options().relocatable() && !parameters->doing_static_link())
@@ -1082,15 +1188,16 @@ Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab,
   return off;
 }
 
-// Create a .note section for an executable or shared library.  This
-// records the version of gold used to create the binary.
+// Create a note header following the format defined in the ELF ABI.
+// NAME is the name, NOTE_TYPE is the type, DESCSZ is the size of the
+// descriptor.  ALLOCATE is true if the section should be allocated in
+// memory.  This returns the new note section.  It sets
+// *TRAILING_PADDING to the number of trailing zero bytes required.
 
-void
-Layout::create_gold_note()
+Output_section*
+Layout::create_note(const char* name, int note_type, size_t descsz,
+                   bool allocate, size_t* trailing_padding)
 {
-  if (parameters->options().relocatable())
-    return;
-
   // Authorities all agree that the values in a .note field should
   // be aligned on 4-byte boundaries for 32-bit binaries.  However,
   // they differ on what the alignment is for 64-bit binaries.
@@ -1109,19 +1216,14 @@ Layout::create_gold_note()
 #endif
 
   // The contents of the .note section.
-  const char* name = "GNU";
-  std::string desc(std::string("gold ") + gold::get_version_string());
   size_t namesz = strlen(name) + 1;
   size_t aligned_namesz = align_address(namesz, size / 8);
-  size_t descsz = desc.length() + 1;
   size_t aligned_descsz = align_address(descsz, size / 8);
-  const int note_type = 4;
 
-  size_t notesz = 3 * (size / 8) + aligned_namesz + aligned_descsz;
+  size_t notehdrsz = 3 * (size / 8) + aligned_namesz;
 
-  unsigned char buffer[128];
-  gold_assert(sizeof buffer >= notesz);
-  memset(buffer, 0, notesz);
+  unsigned char* buffer = new unsigned char[notehdrsz];
+  memset(buffer, 0, notehdrsz);
 
   bool is_big_endian = parameters->target().is_big_endian();
 
@@ -1159,15 +1261,46 @@ Layout::create_gold_note()
     gold_unreachable();
 
   memcpy(buffer + 3 * (size / 8), name, namesz);
-  memcpy(buffer + 3 * (size / 8) + aligned_namesz, desc.data(), descsz);
 
   const char* note_name = this->namepool_.add(".note", false, NULL);
+  elfcpp::Elf_Xword flags = 0;
+  if (allocate)
+    flags = elfcpp::SHF_ALLOC;
   Output_section* os = this->make_output_section(note_name,
                                                 elfcpp::SHT_NOTE,
-                                                0);
-  Output_section_data* posd = new Output_data_const(buffer, notesz,
-                                                   size / 8);
+                                                flags);
+  Output_section_data* posd = new Output_data_const_buffer(buffer, notehdrsz,
+                                                          size / 8);
   os->add_output_section_data(posd);
+
+  *trailing_padding = aligned_descsz - descsz;
+
+  return os;
+}
+
+// For an executable or shared library, create a note to record the
+// version of gold used to create the binary.
+
+void
+Layout::create_gold_note()
+{
+  if (parameters->options().relocatable())
+    return;
+
+  std::string desc = std::string("gold ") + gold::get_version_string();
+
+  size_t trailing_padding;
+  Output_section *os = this->create_note("GNU", elfcpp::NT_GNU_GOLD_VERSION,
+                                        desc.size(), false, &trailing_padding);
+
+  Output_section_data* posd = new Output_data_const(desc, 4);
+  os->add_output_section_data(posd);
+
+  if (trailing_padding > 0)
+    {
+      posd = new Output_data_fixed_space(trailing_padding, 0);
+      os->add_output_section_data(posd);
+    }
 }
 
 // Record whether the stack should be executable.  This can be set
@@ -1219,6 +1352,104 @@ Layout::create_executable_stack_info(const Target* target)
     }
 }
 
+// If --build-id was used, set up the build ID note.
+
+void
+Layout::create_build_id()
+{
+  if (!parameters->options().user_set_build_id())
+    return;
+
+  const char* style = parameters->options().build_id();
+  if (strcmp(style, "none") == 0)
+    return;
+
+  // Set DESCSZ to the size of the note descriptor.  When possible,
+  // set DESC to the note descriptor contents.
+  size_t descsz;
+  std::string desc;
+  if (strcmp(style, "md5") == 0)
+    descsz = 128 / 8;
+  else if (strcmp(style, "sha1") == 0)
+    descsz = 160 / 8;
+  else if (strcmp(style, "uuid") == 0)
+    {
+      const size_t uuidsz = 128 / 8;
+
+      char buffer[uuidsz];
+      memset(buffer, 0, uuidsz);
+
+      int descriptor = ::open("/dev/urandom", O_RDONLY);
+      if (descriptor < 0)
+       gold_error(_("--build-id=uuid failed: could not open /dev/urandom: %s"),
+                  strerror(errno));
+      else
+       {
+         ssize_t got = ::read(descriptor, buffer, uuidsz);
+         ::close(descriptor);
+         if (got < 0)
+           gold_error(_("/dev/urandom: read failed: %s"), strerror(errno));
+         else if (static_cast<size_t>(got) != uuidsz)
+           gold_error(_("/dev/urandom: expected %zu bytes, got %zd bytes"),
+                      uuidsz, got);
+       }
+
+      desc.assign(buffer, uuidsz);
+      descsz = uuidsz;
+    }
+  else if (strncmp(style, "0x", 2) == 0)
+    {
+      hex_init();
+      const char* p = style + 2;
+      while (*p != '\0')
+       {
+         if (hex_p(p[0]) && hex_p(p[1]))
+           {
+             char c = (hex_value(p[0]) << 4) | hex_value(p[1]);
+             desc += c;
+             p += 2;
+           }
+         else if (*p == '-' || *p == ':')
+           ++p;
+         else
+           gold_fatal(_("--build-id argument '%s' not a valid hex number"),
+                      style);
+       }
+      descsz = desc.size();
+    }
+  else
+    gold_fatal(_("unrecognized --build-id argument '%s'"), style);
+
+  // Create the note.
+  size_t trailing_padding;
+  Output_section* os = this->create_note("GNU", elfcpp::NT_GNU_BUILD_ID,
+                                        descsz, true, &trailing_padding);
+
+  if (!desc.empty())
+    {
+      // We know the value already, so we fill it in now.
+      gold_assert(desc.size() == descsz);
+
+      Output_section_data* posd = new Output_data_const(desc, 4);
+      os->add_output_section_data(posd);
+
+      if (trailing_padding != 0)
+       {
+         posd = new Output_data_fixed_space(trailing_padding, 0);
+         os->add_output_section_data(posd);
+       }
+    }
+  else
+    {
+      // We need to compute a checksum after we have completed the
+      // link.
+      gold_assert(trailing_padding == 0);
+      this->build_id_note_ = new Output_data_fixed_space(descsz, 4);
+      os->add_output_section_data(this->build_id_note_);
+      os->set_after_input_sections();
+    }
+}
+
 // Return whether SEG1 should be before SEG2 in the output file.  This
 // is based entirely on the segment type and flags.  When this is
 // called the segment addresses has normally not yet been set.
@@ -1436,8 +1667,8 @@ Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
            }
 
          unsigned int shndx_hold = *pshndx;
-         uint64_t new_addr = (*p)->set_section_addresses(false, addr, &off,
-                                                         pshndx);
+         uint64_t new_addr = (*p)->set_section_addresses(this, false, addr,
+                                                          &off, pshndx);
 
          // Now that we know the size of this segment, we may be able
          // to save a page in memory, at the cost of wasting some
@@ -1462,8 +1693,8 @@ Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
                  addr = align_address(aligned_addr, common_pagesize);
                  addr = align_address(addr, (*p)->maximum_alignment());
                  off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
-                 new_addr = (*p)->set_section_addresses(true, addr, &off,
-                                                        pshndx);
+                 new_addr = (*p)->set_section_addresses(this, true, addr,
+                                                         &off, pshndx);
                }
            }
 
@@ -1924,27 +2155,53 @@ Layout::create_dynamic_symtab(const Input_objects* input_objects,
 
   // Create the hash tables.
 
-  // FIXME: We need an option to create a GNU hash table.
+  if (strcmp(parameters->options().hash_style(), "sysv") == 0
+      || strcmp(parameters->options().hash_style(), "both") == 0)
+    {
+      unsigned char* phash;
+      unsigned int hashlen;
+      Dynobj::create_elf_hash_table(*pdynamic_symbols, local_symcount,
+                                   &phash, &hashlen);
+
+      Output_section* hashsec = this->choose_output_section(NULL, ".hash",
+                                                           elfcpp::SHT_HASH,
+                                                           elfcpp::SHF_ALLOC,
+                                                           false);
+
+      Output_section_data* hashdata = new Output_data_const_buffer(phash,
+                                                                  hashlen,
+                                                                  align);
+      hashsec->add_output_section_data(hashdata);
+
+      hashsec->set_link_section(dynsym);
+      hashsec->set_entsize(4);
+
+      odyn->add_section_address(elfcpp::DT_HASH, hashsec);
+    }
 
-  unsigned char* phash;
-  unsigned int hashlen;
-  Dynobj::create_elf_hash_table(*pdynamic_symbols, local_symcount,
-                               &phash, &hashlen);
+  if (strcmp(parameters->options().hash_style(), "gnu") == 0
+      || strcmp(parameters->options().hash_style(), "both") == 0)
+    {
+      unsigned char* phash;
+      unsigned int hashlen;
+      Dynobj::create_gnu_hash_table(*pdynamic_symbols, local_symcount,
+                                   &phash, &hashlen);
 
-  Output_section* hashsec = this->choose_output_section(NULL, ".hash",
-                                                       elfcpp::SHT_HASH,
-                                                       elfcpp::SHF_ALLOC,
-                                                       false);
+      Output_section* hashsec = this->choose_output_section(NULL, ".gnu.hash",
+                                                           elfcpp::SHT_GNU_HASH,
+                                                           elfcpp::SHF_ALLOC,
+                                                           false);
 
-  Output_section_data* hashdata = new Output_data_const_buffer(phash,
-                                                              hashlen,
-                                                              align);
-  hashsec->add_output_section_data(hashdata);
+      Output_section_data* hashdata = new Output_data_const_buffer(phash,
+                                                                  hashlen,
+                                                                  align);
+      hashsec->add_output_section_data(hashdata);
 
-  hashsec->set_link_section(dynsym);
-  hashsec->set_entsize(4);
+      hashsec->set_link_section(dynsym);
+      hashsec->set_entsize(4);
 
-  odyn->add_section_address(elfcpp::DT_HASH, hashsec);
+      odyn->add_section_address(elfcpp::DT_GNU_HASH, hashsec);
+    }
 }
 
 // Assign offsets to each local portion of the dynamic symbol table.
@@ -2551,6 +2808,46 @@ Layout::write_sections_after_input_sections(Output_file* of)
   this->section_headers_->write(of);
 }
 
+// If the build ID requires computing a checksum, do so here, and
+// write it out.  We compute a checksum over the entire file because
+// that is simplest.
+
+void
+Layout::write_build_id(Output_file* of) const
+{
+  if (this->build_id_note_ == NULL)
+    return;
+
+  const unsigned char* iv = of->get_input_view(0, this->output_file_size_);
+
+  unsigned char* ov = of->get_output_view(this->build_id_note_->offset(),
+                                         this->build_id_note_->data_size());
+
+  const char* style = parameters->options().build_id();
+  if (strcmp(style, "sha1") == 0)
+    {
+      sha1_ctx ctx;
+      sha1_init_ctx(&ctx);
+      sha1_process_bytes(iv, this->output_file_size_, &ctx);
+      sha1_finish_ctx(&ctx, ov);
+    }
+  else if (strcmp(style, "md5") == 0)
+    {
+      md5_ctx ctx;
+      md5_init_ctx(&ctx);
+      md5_process_bytes(iv, this->output_file_size_, &ctx);
+      md5_finish_ctx(&ctx, ov);
+    }
+  else
+    gold_unreachable();
+
+  of->write_output_view(this->build_id_note_->offset(),
+                       this->build_id_note_->data_size(),
+                       ov);
+
+  of->free_input_view(0, this->output_file_size_, iv);
+}
+
 // Write out a binary file.  This is called after the link is
 // complete.  IN is the temporary output file we used to generate the
 // ELF code.  We simply walk through the segments, read them from
@@ -2731,6 +3028,9 @@ Write_after_input_sections_task::run(Workqueue*)
 void
 Close_task_runner::run(Workqueue*, const Task*)
 {
+  // If we need to compute a checksum for the BUILD if, we do so here.
+  this->layout_->write_build_id(this->of_);
+
   // If we've been asked to create a binary file, we do so here.
   if (this->options_->oformat_enum() != General_options::OBJECT_FORMAT_ELF)
     this->layout_->write_binary(this->of_);
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