gdb/mipsread.c

   1 /* Read a symbol table in MIPS' format (Third-Eye).
   2
   3    Copyright (C) 1986-2018 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 "bfd.h"
  28 #include "symtab.h"
  29 #include "objfiles.h"
  30 #include "buildsym.h"
  31 #include "stabsread.h"
  32
  33 #include "coff/sym.h"
  34 #include "coff/internal.h"
  35 #include "coff/ecoff.h"
  36 #include "libcoff.h"            /* Private BFD COFF information.  */
  37 #include "libecoff.h"           /* Private BFD ECOFF information.  */
  38 #include "elf/common.h"
  39 #include "elf/internal.h"
  40 #include "elf/mips.h"
  41
  42 #include "psymtab.h"
  43
  44 static void
  45 read_alphacoff_dynamic_symtab (minimal_symbol_reader &,
  46                                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, symfile_add_flags symfile_flags)
  71 {
  72   bfd *abfd = objfile->obfd;
  73
  74   minimal_symbol_reader reader (objfile);
  75
  76   /* Now that the executable file is positioned at symbol table,
  77      process it and define symbols accordingly.  */
  78
  79   if (!((*ecoff_backend (abfd)->debug_swap.read_debug_info)
  80         (abfd, (asection *) NULL, &ecoff_data (abfd)->debug_info)))
  81     error (_("Error reading symbol table: %s"), bfd_errmsg (bfd_get_error ()));
  82
  83   mdebug_build_psymtabs (reader, objfile, &ecoff_backend (abfd)->debug_swap,
  84                          &ecoff_data (abfd)->debug_info);
  85
  86   /* Add alpha coff dynamic symbols.  */
  87
  88   read_alphacoff_dynamic_symtab (reader, objfile->section_offsets, objfile);
  89
  90   /* Install any minimal symbols that have been collected as the current
  91      minimal symbols for this objfile.  */
  92
  93   reader.install ();
  94 }
  95
  96 /* Perform any local cleanups required when we are done with a
  97    particular objfile.  */
  98
  99 static void
 100 mipscoff_symfile_finish (struct objfile *objfile)
 101 {
 102 }
 103
 104 /* Alpha OSF/1 encapsulates the dynamic symbols in ELF format in a
 105    standard COFF section.  The ELF format for the symbols differs from
 106    the format defined in elf/external.h.  It seems that a normal ELF
 107    32-bit format is used, and the representation only changes because
 108    longs are 64-bit on the alpha.  In addition, the handling of
 109    text/data section indices for symbols is different from the ELF
 110    ABI.  As the BFD linker currently does not support dynamic linking
 111    on the alpha, there seems to be no reason to pollute BFD with
 112    another mixture of object file formats for now.  */
 113
 114 /* Format of an alpha external ELF symbol.  */
 115
 116 typedef struct
 117 {
 118   unsigned char st_name[4];     /* Symbol name, index in string table.  */
 119   unsigned char st_pad[4];      /* Pad to long word boundary.  */
 120   unsigned char st_value[8];    /* Value of the symbol.  */
 121   unsigned char st_size[4];     /* Associated symbol size.  */
 122   unsigned char st_info[1];     /* Type and binding attributes.  */
 123   unsigned char st_other[1];    /* No defined meaning, 0.  */
 124   unsigned char st_shndx[2];    /* Associated section index.  */
 125 } Elfalpha_External_Sym;
 126
 127 /* Format of an alpha external ELF dynamic info structure.  */
 128
 129 typedef struct
 130 {
 131   unsigned char d_tag[4];       /* Tag.  */
 132   unsigned char d_pad[4];       /* Pad to long word boundary.  */
 133   union
 134   {
 135     unsigned char d_ptr[8];     /* Pointer value.  */
 136     unsigned char d_val[4];     /* Integer value.  */
 137   }
 138   d_un;
 139 } Elfalpha_External_Dyn;
 140
 141 /* Struct to obtain the section pointers for alpha dynamic symbol info.  */
 142
 143 struct alphacoff_dynsecinfo
 144 {
 145   asection *sym_sect;           /* Section pointer for .dynsym section.  */
 146   asection *str_sect;           /* Section pointer for .dynstr section.  */
 147   asection *dyninfo_sect;       /* Section pointer for .dynamic section.  */
 148   asection *got_sect;           /* Section pointer for .got section.  */
 149 };
 150
 151 /* We are called once per section from read_alphacoff_dynamic_symtab.
 152    We need to examine each section we are passed, check to see if it
 153    is something we are interested in processing, and if so, stash away
 154    some access information for the section.  */
 155
 156 static void
 157 alphacoff_locate_sections (bfd *ignore_abfd, asection *sectp, void *sip)
 158 {
 159   struct alphacoff_dynsecinfo *si;
 160
 161   si = (struct alphacoff_dynsecinfo *) sip;
 162
 163   if (strcmp (sectp->name, ".dynsym") == 0)
 164     si->sym_sect = sectp;
 165   else if (strcmp (sectp->name, ".dynstr") == 0)
 166     si->str_sect = sectp;
 167   else if (strcmp (sectp->name, ".dynamic") == 0)
 168     si->dyninfo_sect = sectp;
 169   else if (strcmp (sectp->name, ".got") == 0)
 170       si->got_sect = sectp;
 171 }
 172
 173 /* Scan an alpha dynamic symbol table for symbols of interest and add
 174    them to the minimal symbol table.  */
 175
 176 static void
 177 read_alphacoff_dynamic_symtab (minimal_symbol_reader &reader,
 178                                struct section_offsets *section_offsets,
 179                                struct objfile *objfile)
 180 {
 181   bfd *abfd = objfile->obfd;
 182   struct alphacoff_dynsecinfo si;
 183   int sym_count;
 184   int i;
 185   int stripped;
 186   Elfalpha_External_Sym *x_symp;
 187   gdb_byte *dyninfo_p;
 188   gdb_byte *dyninfo_end;
 189   int got_entry_size = 8;
 190   int dt_mips_local_gotno = -1;
 191   int dt_mips_gotsym = -1;
 192
 193   /* We currently only know how to handle alpha dynamic symbols.  */
 194   if (bfd_get_arch (abfd) != bfd_arch_alpha)
 195     return;
 196
 197   /* Locate the dynamic symbols sections and read them in.  */
 198   memset ((char *) &si, 0, sizeof (si));
 199   bfd_map_over_sections (abfd, alphacoff_locate_sections, (void *) & si);
 200   if (si.sym_sect == NULL || si.str_sect == NULL
 201       || si.dyninfo_sect == NULL || si.got_sect == NULL)
 202     return;
 203
 204   gdb::byte_vector sym_sec (bfd_get_section_size (si.sym_sect));
 205   gdb::byte_vector str_sec (bfd_get_section_size (si.str_sect));
 206   gdb::byte_vector dyninfo_sec (bfd_get_section_size (si.dyninfo_sect));
 207   gdb::byte_vector got_sec (bfd_get_section_size (si.got_sect));
 208
 209   if (!bfd_get_section_contents (abfd, si.sym_sect, sym_sec.data (),
 210                                  (file_ptr) 0, sym_sec.size ()))
 211     return;
 212   if (!bfd_get_section_contents (abfd, si.str_sect, str_sec.data (),
 213                                  (file_ptr) 0, str_sec.size ()))
 214     return;
 215   if (!bfd_get_section_contents (abfd, si.dyninfo_sect, dyninfo_sec.data (),
 216                                  (file_ptr) 0, dyninfo_sec.size ()))
 217     return;
 218   if (!bfd_get_section_contents (abfd, si.got_sect, got_sec.data (),
 219                                  (file_ptr) 0, got_sec.size ()))
 220     return;
 221
 222   /* Find the number of local GOT entries and the index for the
 223      first dynamic symbol in the GOT.  */
 224   for ((dyninfo_p = dyninfo_sec.data (),
 225         dyninfo_end = dyninfo_p + dyninfo_sec.size ());
 226        dyninfo_p < dyninfo_end;
 227        dyninfo_p += sizeof (Elfalpha_External_Dyn))
 228     {
 229       Elfalpha_External_Dyn *x_dynp = (Elfalpha_External_Dyn *) dyninfo_p;
 230       long dyn_tag;
 231
 232       dyn_tag = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp->d_tag);
 233       if (dyn_tag == DT_NULL)
 234         break;
 235       else if (dyn_tag == DT_MIPS_LOCAL_GOTNO)
 236         {
 237           if (dt_mips_local_gotno < 0)
 238             dt_mips_local_gotno
 239               = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp->d_un.d_val);
 240         }
 241       else if (dyn_tag == DT_MIPS_GOTSYM)
 242         {
 243           if (dt_mips_gotsym < 0)
 244             dt_mips_gotsym
 245               = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp->d_un.d_val);
 246         }
 247     }
 248   if (dt_mips_local_gotno < 0 || dt_mips_gotsym < 0)
 249     return;
 250
 251   /* Scan all dynamic symbols and enter them into the minimal symbol
 252      table if appropriate.  */
 253   sym_count = sym_sec.size () / sizeof (Elfalpha_External_Sym);
 254   stripped = (bfd_get_symcount (abfd) == 0);
 255
 256   /* Skip first symbol, which is a null dummy.  */
 257   for (i = 1, x_symp = (Elfalpha_External_Sym *) sym_sec.data () + 1;
 258        i < sym_count;
 259        i++, x_symp++)
 260     {
 261       unsigned long strx;
 262       char *name;
 263       bfd_vma sym_value;
 264       unsigned char sym_info;
 265       unsigned int sym_shndx;
 266       int isglobal;
 267       enum minimal_symbol_type ms_type;
 268
 269       strx = bfd_h_get_32 (abfd, (bfd_byte *) x_symp->st_name);
 270       if (strx >= str_sec.size ())
 271         continue;
 272       name = (char *) (str_sec.data () + strx);
 273       if (*name == '\0' || *name == '.')
 274         continue;
 275
 276       sym_value = bfd_h_get_64 (abfd, (bfd_byte *) x_symp->st_value);
 277       sym_info = bfd_h_get_8 (abfd, (bfd_byte *) x_symp->st_info);
 278       sym_shndx = bfd_h_get_16 (abfd, (bfd_byte *) x_symp->st_shndx);
 279       if (sym_shndx >= (SHN_LORESERVE & 0xffff))
 280         sym_shndx += SHN_LORESERVE - (SHN_LORESERVE & 0xffff);
 281       isglobal = (ELF_ST_BIND (sym_info) == STB_GLOBAL);
 282
 283       if (sym_shndx == SHN_UNDEF)
 284         {
 285           /* Handle undefined functions which are defined in a shared
 286              library.  */
 287           if (ELF_ST_TYPE (sym_info) != STT_FUNC
 288               || ELF_ST_BIND (sym_info) != STB_GLOBAL)
 289             continue;
 290
 291           ms_type = mst_solib_trampoline;
 292
 293           /* If sym_value is nonzero, it points to the shared library
 294              trampoline entry, which is what we are looking for.
 295
 296              If sym_value is zero, then we have to get the GOT entry
 297              for the symbol.
 298
 299              If the GOT entry is nonzero, it represents the quickstart
 300              address of the function and we use that as the symbol
 301              value.
 302
 303              If the GOT entry is zero, the function address has to be
 304              resolved by the runtime loader before the executable is
 305              started.  We are unable to find any meaningful address
 306              for these functions in the executable file, so we skip
 307              them.  */
 308           if (sym_value == 0)
 309             {
 310               int got_entry_offset =
 311                 (i - dt_mips_gotsym + dt_mips_local_gotno) * got_entry_size;
 312
 313               if (got_entry_offset < 0
 314                   || got_entry_offset >= got_sec.size ())
 315                 continue;
 316               sym_value =
 317                 bfd_h_get_64 (abfd,
 318                               (bfd_byte *) (got_sec.data ()
 319                                             + got_entry_offset));
 320               if (sym_value == 0)
 321                 continue;
 322             }
 323         }
 324       else
 325         {
 326           /* Symbols defined in the executable itself.  We only care
 327              about them if this is a stripped executable, otherwise
 328              they have been retrieved from the normal symbol table
 329              already.  */
 330           if (!stripped)
 331             continue;
 332
 333           if (sym_shndx == SHN_MIPS_TEXT)
 334             {
 335               if (isglobal)
 336                 ms_type = mst_text;
 337               else
 338                 ms_type = mst_file_text;
 339             }
 340           else if (sym_shndx == SHN_MIPS_DATA)
 341             {
 342               if (isglobal)
 343                 ms_type = mst_data;
 344               else
 345                 ms_type = mst_file_data;
 346             }
 347           else if (sym_shndx == SHN_MIPS_ACOMMON)
 348             {
 349               if (isglobal)
 350                 ms_type = mst_bss;
 351               else
 352                 ms_type = mst_file_bss;
 353             }
 354           else if (sym_shndx == SHN_ABS)
 355             {
 356               ms_type = mst_abs;
 357             }
 358           else
 359             {
 360               continue;
 361             }
 362         }
 363
 364       reader.record (name, sym_value, ms_type);
 365     }
 366 }
 367
 368 /* Initialization.  */
 369
 370 static const struct sym_fns ecoff_sym_fns =
 371 {
 372   mipscoff_new_init,            /* init anything gbl to entire symtab */
 373   mipscoff_symfile_init,        /* read initial info, setup for sym_read() */
 374   mipscoff_symfile_read,        /* read a symbol file into symtab */
 375   NULL,                         /* sym_read_psymbols */
 376   mipscoff_symfile_finish,      /* finished with file, cleanup */
 377   default_symfile_offsets,      /* dummy FIXME til implem sym reloc */
 378   default_symfile_segments,     /* Get segment information from a file.  */
 379   NULL,
 380   default_symfile_relocate,     /* Relocate a debug section.  */
 381   NULL,                         /* sym_probe_fns */
 382   &psym_functions
 383 };
 384
 385 void
 386 _initialize_mipsread (void)
 387 {
 388   add_symtab_fns (bfd_target_ecoff_flavour, &ecoff_sym_fns);
 389 }