gdb/mipsread.c

   1 /* Read a symbol table in MIPS' format (Third-Eye).
   2
   3    Copyright (C) 1986-2013 Free Software Foundation, Inc.
   4
   5    Contributed by Alessandro Forin (af@cs.cmu.edu) at CMU.  Major work
   6    by Per Bothner, John Gilmore and Ian Lance Taylor at Cygnus Support.
   7
   8    This file is part of GDB.
   9
  10    This program is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 3 of the License, or
  13    (at your option) any later version.
  14
  15    This program is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  22
  23 /* Read symbols from an ECOFF file.  Most of the work is done in
  24    mdebugread.c.  */
  25
  26 #include "defs.h"
  27 #include "gdb_string.h"
  28 #include "bfd.h"
  29 #include "symtab.h"
  30 #include "objfiles.h"
  31 #include "buildsym.h"
  32 #include "stabsread.h"
  33
  34 #include "coff/sym.h"
  35 #include "coff/internal.h"
  36 #include "coff/ecoff.h"
  37 #include "libcoff.h"            /* Private BFD COFF information.  */
  38 #include "libecoff.h"           /* Private BFD ECOFF information.  */
  39 #include "elf/common.h"
  40 #include "elf/internal.h"
  41 #include "elf/mips.h"
  42
  43 #include "psymtab.h"
  44
  45 static void
  46 read_alphacoff_dynamic_symtab (struct section_offsets *,
  47                                struct objfile *objfile);
  48
  49 /* Initialize anything that needs initializing when a completely new
  50    symbol file is specified (not just adding some symbols from another
  51    file, e.g. a shared library).  */
  52
  53 static void
  54 mipscoff_new_init (struct objfile *ignore)
  55 {
  56   stabsread_new_init ();
  57   buildsym_new_init ();
  58 }
  59
  60 /* Initialize to read a symbol file (nothing to do).  */
  61
  62 static void
  63 mipscoff_symfile_init (struct objfile *objfile)
  64 {
  65 }
  66
  67 /* Read a symbol file from a file.  */
  68
  69 static void
  70 mipscoff_symfile_read (struct objfile *objfile, int symfile_flags)
  71 {
  72   bfd *abfd = objfile->obfd;
  73   struct cleanup *back_to;
  74
  75   init_minimal_symbol_collection ();
  76   back_to = make_cleanup_discard_minimal_symbols ();
  77
  78   /* Now that the executable file is positioned at symbol table,
  79      process it and define symbols accordingly.  */
  80
  81   if (!((*ecoff_backend (abfd)->debug_swap.read_debug_info)
  82         (abfd, (asection *) NULL, &ecoff_data (abfd)->debug_info)))
  83     error (_("Error reading symbol table: %s"), bfd_errmsg (bfd_get_error ()));
  84
  85   mdebug_build_psymtabs (objfile, &ecoff_backend (abfd)->debug_swap,
  86                          &ecoff_data (abfd)->debug_info);
  87
  88   /* Add alpha coff dynamic symbols.  */
  89
  90   read_alphacoff_dynamic_symtab (objfile->section_offsets, objfile);
  91
  92   /* Install any minimal symbols that have been collected as the current
  93      minimal symbols for this objfile.  */
  94
  95   install_minimal_symbols (objfile);
  96   do_cleanups (back_to);
  97 }
  98
  99 /* Perform any local cleanups required when we are done with a
 100    particular objfile.  */
 101
 102 static void
 103 mipscoff_symfile_finish (struct objfile *objfile)
 104 {
 105 }
 106
 107 /* Alpha OSF/1 encapsulates the dynamic symbols in ELF format in a
 108    standard COFF section.  The ELF format for the symbols differs from
 109    the format defined in elf/external.h.  It seems that a normal ELF
 110    32-bit format is used, and the representation only changes because
 111    longs are 64-bit on the alpha.  In addition, the handling of
 112    text/data section indices for symbols is different from the ELF
 113    ABI.  As the BFD linker currently does not support dynamic linking
 114    on the alpha, there seems to be no reason to pollute BFD with
 115    another mixture of object file formats for now.  */
 116
 117 /* Format of an alpha external ELF symbol.  */
 118
 119 typedef struct
 120 {
 121   unsigned char st_name[4];     /* Symbol name, index in string table.  */
 122   unsigned char st_pad[4];      /* Pad to long word boundary.  */
 123   unsigned char st_value[8];    /* Value of the symbol.  */
 124   unsigned char st_size[4];     /* Associated symbol size.  */
 125   unsigned char st_info[1];     /* Type and binding attributes.  */
 126   unsigned char st_other[1];    /* No defined meaning, 0.  */
 127   unsigned char st_shndx[2];    /* Associated section index.  */
 128 } Elfalpha_External_Sym;
 129
 130 /* Format of an alpha external ELF dynamic info structure.  */
 131
 132 typedef struct
 133 {
 134   unsigned char d_tag[4];       /* Tag.  */
 135   unsigned char d_pad[4];       /* Pad to long word boundary.  */
 136   union
 137   {
 138     unsigned char d_ptr[8];     /* Pointer value.  */
 139     unsigned char d_val[4];     /* Integer value.  */
 140   }
 141   d_un;
 142 } Elfalpha_External_Dyn;
 143
 144 /* Struct to obtain the section pointers for alpha dynamic symbol info.  */
 145
 146 struct alphacoff_dynsecinfo
 147 {
 148   asection *sym_sect;           /* Section pointer for .dynsym section.  */
 149   asection *str_sect;           /* Section pointer for .dynstr section.  */
 150   asection *dyninfo_sect;       /* Section pointer for .dynamic section.  */
 151   asection *got_sect;           /* Section pointer for .got section.  */
 152 };
 153
 154 /* We are called once per section from read_alphacoff_dynamic_symtab.
 155    We need to examine each section we are passed, check to see if it
 156    is something we are interested in processing, and if so, stash away
 157    some access information for the section.  */
 158
 159 static void
 160 alphacoff_locate_sections (bfd *ignore_abfd, asection *sectp, void *sip)
 161 {
 162   struct alphacoff_dynsecinfo *si;
 163
 164   si = (struct alphacoff_dynsecinfo *) sip;
 165
 166   if (strcmp (sectp->name, ".dynsym") == 0)
 167     si->sym_sect = sectp;
 168   else if (strcmp (sectp->name, ".dynstr") == 0)
 169     si->str_sect = sectp;
 170   else if (strcmp (sectp->name, ".dynamic") == 0)
 171     si->dyninfo_sect = sectp;
 172   else if (strcmp (sectp->name, ".got") == 0)
 173       si->got_sect = sectp;
 174 }
 175
 176 /* Scan an alpha dynamic symbol table for symbols of interest and add
 177    them to the minimal symbol table.  */
 178
 179 static void
 180 read_alphacoff_dynamic_symtab (struct section_offsets *section_offsets,
 181                                struct objfile *objfile)
 182 {
 183   bfd *abfd = objfile->obfd;
 184   struct alphacoff_dynsecinfo si;
 185   char *sym_secptr;
 186   char *str_secptr;
 187   char *dyninfo_secptr;
 188   char *got_secptr;
 189   bfd_size_type sym_secsize;
 190   bfd_size_type str_secsize;
 191   bfd_size_type dyninfo_secsize;
 192   bfd_size_type got_secsize;
 193   int sym_count;
 194   int i;
 195   int stripped;
 196   Elfalpha_External_Sym *x_symp;
 197   char *dyninfo_p;
 198   char *dyninfo_end;
 199   int got_entry_size = 8;
 200   int dt_mips_local_gotno = -1;
 201   int dt_mips_gotsym = -1;
 202   struct cleanup *cleanups;
 203
 204   /* We currently only know how to handle alpha dynamic symbols.  */
 205   if (bfd_get_arch (abfd) != bfd_arch_alpha)
 206     return;
 207
 208   /* Locate the dynamic symbols sections and read them in.  */
 209   memset ((char *) &si, 0, sizeof (si));
 210   bfd_map_over_sections (abfd, alphacoff_locate_sections, (void *) & si);
 211   if (si.sym_sect == NULL || si.str_sect == NULL
 212       || si.dyninfo_sect == NULL || si.got_sect == NULL)
 213     return;
 214
 215   sym_secsize = bfd_get_section_size (si.sym_sect);
 216   str_secsize = bfd_get_section_size (si.str_sect);
 217   dyninfo_secsize = bfd_get_section_size (si.dyninfo_sect);
 218   got_secsize = bfd_get_section_size (si.got_sect);
 219   sym_secptr = xmalloc (sym_secsize);
 220   cleanups = make_cleanup (xfree, sym_secptr);
 221   str_secptr = xmalloc (str_secsize);
 222   make_cleanup (xfree, str_secptr);
 223   dyninfo_secptr = xmalloc (dyninfo_secsize);
 224   make_cleanup (xfree, dyninfo_secptr);
 225   got_secptr = xmalloc (got_secsize);
 226   make_cleanup (xfree, got_secptr);
 227
 228   if (!bfd_get_section_contents (abfd, si.sym_sect, sym_secptr,
 229                                  (file_ptr) 0, sym_secsize))
 230     return;
 231   if (!bfd_get_section_contents (abfd, si.str_sect, str_secptr,
 232                                  (file_ptr) 0, str_secsize))
 233     return;
 234   if (!bfd_get_section_contents (abfd, si.dyninfo_sect, dyninfo_secptr,
 235                                  (file_ptr) 0, dyninfo_secsize))
 236     return;
 237   if (!bfd_get_section_contents (abfd, si.got_sect, got_secptr,
 238                                  (file_ptr) 0, got_secsize))
 239     return;
 240
 241   /* Find the number of local GOT entries and the index for the
 242      first dynamic symbol in the GOT.  */
 243   for (dyninfo_p = dyninfo_secptr, dyninfo_end = dyninfo_p + dyninfo_secsize;
 244        dyninfo_p < dyninfo_end;
 245        dyninfo_p += sizeof (Elfalpha_External_Dyn))
 246     {
 247       Elfalpha_External_Dyn *x_dynp = (Elfalpha_External_Dyn *) dyninfo_p;
 248       long dyn_tag;
 249
 250       dyn_tag = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp->d_tag);
 251       if (dyn_tag == DT_NULL)
 252         break;
 253       else if (dyn_tag == DT_MIPS_LOCAL_GOTNO)
 254         {
 255           if (dt_mips_local_gotno < 0)
 256             dt_mips_local_gotno
 257               = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp->d_un.d_val);
 258         }
 259       else if (dyn_tag == DT_MIPS_GOTSYM)
 260         {
 261           if (dt_mips_gotsym < 0)
 262             dt_mips_gotsym
 263               = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp->d_un.d_val);
 264         }
 265     }
 266   if (dt_mips_local_gotno < 0 || dt_mips_gotsym < 0)
 267     return;
 268
 269   /* Scan all dynamic symbols and enter them into the minimal symbol
 270      table if appropriate.  */
 271   sym_count = sym_secsize / sizeof (Elfalpha_External_Sym);
 272   stripped = (bfd_get_symcount (abfd) == 0);
 273
 274   /* Skip first symbol, which is a null dummy.  */
 275   for (i = 1, x_symp = (Elfalpha_External_Sym *) sym_secptr + 1;
 276        i < sym_count;
 277        i++, x_symp++)
 278     {
 279       unsigned long strx;
 280       char *name;
 281       bfd_vma sym_value;
 282       unsigned char sym_info;
 283       unsigned int sym_shndx;
 284       int isglobal;
 285       enum minimal_symbol_type ms_type;
 286
 287       strx = bfd_h_get_32 (abfd, (bfd_byte *) x_symp->st_name);
 288       if (strx >= str_secsize)
 289         continue;
 290       name = str_secptr + strx;
 291       if (*name == '\0' || *name == '.')
 292         continue;
 293
 294       sym_value = bfd_h_get_64 (abfd, (bfd_byte *) x_symp->st_value);
 295       sym_info = bfd_h_get_8 (abfd, (bfd_byte *) x_symp->st_info);
 296       sym_shndx = bfd_h_get_16 (abfd, (bfd_byte *) x_symp->st_shndx);
 297       if (sym_shndx >= (SHN_LORESERVE & 0xffff))
 298         sym_shndx += SHN_LORESERVE - (SHN_LORESERVE & 0xffff);
 299       isglobal = (ELF_ST_BIND (sym_info) == STB_GLOBAL);
 300
 301       if (sym_shndx == SHN_UNDEF)
 302         {
 303           /* Handle undefined functions which are defined in a shared
 304              library.  */
 305           if (ELF_ST_TYPE (sym_info) != STT_FUNC
 306               || ELF_ST_BIND (sym_info) != STB_GLOBAL)
 307             continue;
 308
 309           ms_type = mst_solib_trampoline;
 310
 311           /* If sym_value is nonzero, it points to the shared library
 312              trampoline entry, which is what we are looking for.
 313
 314              If sym_value is zero, then we have to get the GOT entry
 315              for the symbol.
 316
 317              If the GOT entry is nonzero, it represents the quickstart
 318              address of the function and we use that as the symbol
 319              value.
 320
 321              If the GOT entry is zero, the function address has to be
 322              resolved by the runtime loader before the executable is
 323              started.  We are unable to find any meaningful address
 324              for these functions in the executable file, so we skip
 325              them.  */
 326           if (sym_value == 0)
 327             {
 328               int got_entry_offset =
 329                 (i - dt_mips_gotsym + dt_mips_local_gotno) * got_entry_size;
 330
 331               if (got_entry_offset < 0 || got_entry_offset >= got_secsize)
 332                 continue;
 333               sym_value =
 334                 bfd_h_get_64 (abfd,
 335                               (bfd_byte *) (got_secptr + got_entry_offset));
 336               if (sym_value == 0)
 337                 continue;
 338             }
 339         }
 340       else
 341         {
 342           /* Symbols defined in the executable itself.  We only care
 343              about them if this is a stripped executable, otherwise
 344              they have been retrieved from the normal symbol table
 345              already.  */
 346           if (!stripped)
 347             continue;
 348
 349           if (sym_shndx == SHN_MIPS_TEXT)
 350             {
 351               if (isglobal)
 352                 ms_type = mst_text;
 353               else
 354                 ms_type = mst_file_text;
 355               sym_value += ANOFFSET (section_offsets, SECT_OFF_TEXT (objfile));
 356             }
 357           else if (sym_shndx == SHN_MIPS_DATA)
 358             {
 359               if (isglobal)
 360                 ms_type = mst_data;
 361               else
 362                 ms_type = mst_file_data;
 363               sym_value += ANOFFSET (section_offsets, SECT_OFF_DATA (objfile));
 364             }
 365           else if (sym_shndx == SHN_MIPS_ACOMMON)
 366             {
 367               if (isglobal)
 368                 ms_type = mst_bss;
 369               else
 370                 ms_type = mst_file_bss;
 371               sym_value += ANOFFSET (section_offsets, SECT_OFF_BSS (objfile));
 372             }
 373           else if (sym_shndx == SHN_ABS)
 374             {
 375               ms_type = mst_abs;
 376             }
 377           else
 378             {
 379               continue;
 380             }
 381         }
 382
 383       prim_record_minimal_symbol (name, sym_value, ms_type, objfile);
 384     }
 385
 386   do_cleanups (cleanups);
 387 }
 388
 389 /* Initialization.  */
 390
 391 static const struct sym_fns ecoff_sym_fns =
 392 {
 393   bfd_target_ecoff_flavour,
 394   mipscoff_new_init,            /* init anything gbl to entire symtab */
 395   mipscoff_symfile_init,        /* read initial info, setup for sym_read() */
 396   mipscoff_symfile_read,        /* read a symbol file into symtab */
 397   NULL,                         /* sym_read_psymbols */
 398   mipscoff_symfile_finish,      /* finished with file, cleanup */
 399   default_symfile_offsets,      /* dummy FIXME til implem sym reloc */
 400   default_symfile_segments,     /* Get segment information from a file.  */
 401   NULL,
 402   default_symfile_relocate,     /* Relocate a debug section.  */
 403   NULL,                         /* sym_probe_fns */
 404   &psym_functions
 405 };
 406
 407 /* Provide a prototype to silence -Wmissing-prototypes.  */
 408 void _initialize_mipsread (void);
 409
 410 void
 411 _initialize_mipsread (void)
 412 {
 413   add_symtab_fns (&ecoff_sym_fns);
 414 }