gold/common.cc

   1 // common.cc -- handle common symbols for gold
   2
   3 #include "gold.h"
   4
   5 #include <algorithm>
   6
   7 #include "workqueue.h"
   8 #include "layout.h"
   9 #include "output.h"
  10 #include "symtab.h"
  11 #include "common.h"
  12
  13 namespace gold
  14 {
  15
  16 // Allocate_commons_task methods.
  17
  18 // This task allocates the common symbols.  We need a lock on the
  19 // symbol table.
  20
  21 Task::Is_runnable_type
  22 Allocate_commons_task::is_runnable(Workqueue*)
  23 {
  24   if (!this->symtab_lock_->is_writable())
  25     return IS_LOCKED;
  26   return IS_RUNNABLE;
  27 }
  28
  29 // Return the locks we hold: one on the symbol table, and one blocker.
  30
  31 class Allocate_commons_task::Allocate_commons_locker : public Task_locker
  32 {
  33  public:
  34   Allocate_commons_locker(Task_token& symtab_lock, Task* task,
  35                           Task_token& blocker, Workqueue* workqueue)
  36     : symtab_locker_(symtab_lock, task),
  37       blocker_(blocker, workqueue)
  38   { }
  39
  40  private:
  41   Task_locker_write symtab_locker_;
  42   Task_locker_block blocker_;
  43 };
  44
  45 Task_locker*
  46 Allocate_commons_task::locks(Workqueue* workqueue)
  47 {
  48   return new Allocate_commons_locker(*this->symtab_lock_, this,
  49                                      *this->blocker_, workqueue);
  50 }
  51
  52 // Allocate the common symbols.
  53
  54 void
  55 Allocate_commons_task::run(Workqueue*)
  56 {
  57   this->symtab_->allocate_commons(this->options_, this->layout_);
  58 }
  59
  60 // This class is used to sort the common symbol by size.  We put the
  61 // larger common symbols first.
  62
  63 template<int size>
  64 class Sort_commons
  65 {
  66  public:
  67   Sort_commons(const Symbol_table* symtab)
  68     : symtab_(symtab)
  69   { }
  70
  71   bool operator()(const Symbol* a, const Symbol* b) const;
  72
  73  private:
  74   const Symbol_table* symtab_;
  75 };
  76
  77 template<int size>
  78 bool
  79 Sort_commons<size>::operator()(const Symbol* pa, const Symbol* pb) const
  80 {
  81   if (pa == NULL)
  82     return false;
  83   if (pb == NULL)
  84     return true;
  85
  86   const Symbol_table* symtab = this->symtab_;
  87   const Sized_symbol<size>* psa;
  88   psa = symtab->get_sized_symbol SELECT_SIZE_NAME(size) (pa
  89                                                          SELECT_SIZE(size));
  90   const Sized_symbol<size>* psb;
  91   psb = symtab->get_sized_symbol SELECT_SIZE_NAME(size) (pb
  92                                                          SELECT_SIZE(size));
  93
  94   typename Sized_symbol<size>::Size_type sa = psa->symsize();
  95   typename Sized_symbol<size>::Size_type sb = psb->symsize();
  96   if (sa < sb)
  97     return false;
  98   else if (sb > sa)
  99     return true;
 100
 101   // When the symbols are the same size, we sort them by alignment.
 102   typename Sized_symbol<size>::Value_type va = psa->value();
 103   typename Sized_symbol<size>::Value_type vb = psb->value();
 104   if (va < vb)
 105     return false;
 106   else if (vb > va)
 107     return true;
 108
 109   // Otherwise we stabilize the sort by sorting by name.
 110   return strcmp(psa->name(), psb->name()) < 0;
 111 }
 112
 113 // Allocate the common symbols.
 114
 115 void
 116 Symbol_table::allocate_commons(const General_options& options, Layout* layout)
 117 {
 118   if (this->get_size() == 32)
 119     this->do_allocate_commons<32>(options, layout);
 120   else if (this->get_size() == 64)
 121     this->do_allocate_commons<64>(options, layout);
 122   else
 123     gold_unreachable();
 124 }
 125
 126 // Allocated the common symbols, sized version.
 127
 128 template<int size>
 129 void
 130 Symbol_table::do_allocate_commons(const General_options&,
 131                                   Layout* layout)
 132 {
 133   typedef typename Sized_symbol<size>::Value_type Value_type;
 134   typedef typename Sized_symbol<size>::Size_type Size_type;
 135
 136   // We've kept a list of all the common symbols.  But the symbol may
 137   // have been resolved to a defined symbol by now.  And it may be a
 138   // forwarder.  First remove all non-common symbols.
 139   bool any = false;
 140   uint64_t addralign = 0;
 141   for (Commons_type::iterator p = this->commons_.begin();
 142        p != this->commons_.end();
 143        ++p)
 144     {
 145       Symbol* sym = *p;
 146       if (sym->is_forwarder())
 147         {
 148           sym = this->resolve_forwards(sym);
 149           *p = sym;
 150         }
 151       if (!sym->is_common())
 152         *p = NULL;
 153       else
 154         {
 155           any = true;
 156           Sized_symbol<size>* ssym;
 157           ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (
 158               sym
 159               SELECT_SIZE(size));
 160           if (ssym->value() > addralign)
 161             addralign = ssym->value();
 162         }
 163     }
 164   if (!any)
 165     return;
 166
 167   // Sort the common symbols by size, so that they pack better into
 168   // memory.
 169   std::sort(this->commons_.begin(), this->commons_.end(),
 170             Sort_commons<size>(this));
 171
 172   // Place them in a newly allocated .bss section.
 173
 174   Output_data_space *poc = new Output_data_space(addralign);
 175
 176   layout->add_output_section_data(".bss", elfcpp::SHT_NOBITS,
 177                                   elfcpp::SHF_WRITE | elfcpp::SHF_ALLOC,
 178                                   poc);
 179
 180   // Allocate them all.
 181
 182   off_t off = 0;
 183   for (Commons_type::iterator p = this->commons_.begin();
 184        p != this->commons_.end();
 185        ++p)
 186     {
 187       Symbol* sym = *p;
 188       if (sym == NULL)
 189         break;
 190
 191       Sized_symbol<size>* ssym;
 192       ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (sym
 193                                                             SELECT_SIZE(size));
 194
 195       off = align_address(off, ssym->value());
 196
 197       Size_type symsize = ssym->symsize();
 198       ssym->init(ssym->name(), poc, off, symsize, ssym->type(),
 199                  ssym->binding(), ssym->visibility(), ssym->nonvis(),
 200                  false);
 201
 202       off += symsize;
 203     }
 204
 205   poc->set_space_size(off);
 206
 207   this->commons_.clear();
 208 }
 209
 210 } // End namespace gold.