Subversion Repositories scarts

/* Read ELF (Executable and Linking Format) object files for GDB.

   Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,

   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008

   Free Software Foundation, Inc.

   Written by Fred Fish at Cygnus Support.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"

#include "bfd.h"

#include "gdb_string.h"

#include "elf-bfd.h"

#include "elf/common.h"

#include "elf/internal.h"

#include "elf/mips.h"

#include "symtab.h"

#include "symfile.h"

#include "objfiles.h"

#include "buildsym.h"

#include "stabsread.h"

#include "gdb-stabs.h"

#include "complaints.h"

#include "demangle.h"

extern void _initialize_elfread (void);

/* The struct elfinfo is available only during ELF symbol table and

   psymtab reading.  It is destroyed at the completion of psymtab-reading.

   It's local to elf_symfile_read.  */

struct elfinfo

  {

    asection *stabsect;         /* Section pointer for .stab section */

    asection *stabindexsect;    /* Section pointer for .stab.index section */

    asection *mdebugsect;       /* Section pointer for .mdebug section */

  };

static void free_elfinfo (void *);

/* Locate the segments in ABFD.  */

static struct symfile_segment_data *

elf_symfile_segments (bfd *abfd)

{

  Elf_Internal_Phdr *phdrs, **segments;

  long phdrs_size;

  int num_phdrs, num_segments, num_sections, i;

  asection *sect;

  struct symfile_segment_data *data;

  phdrs_size = bfd_get_elf_phdr_upper_bound (abfd);

  if (phdrs_size == -1)

    return NULL;

  phdrs = alloca (phdrs_size);

  num_phdrs = bfd_get_elf_phdrs (abfd, phdrs);

  if (num_phdrs == -1)

    return NULL;

  num_segments = 0;

  segments = alloca (sizeof (Elf_Internal_Phdr *) * num_phdrs);

  for (i = 0; i < num_phdrs; i++)

    if (phdrs[i].p_type == PT_LOAD)

      segments[num_segments++] = &phdrs[i];

  if (num_segments == 0)

    return NULL;

  data = XZALLOC (struct symfile_segment_data);

  data->num_segments = num_segments;

  data->segment_bases = XCALLOC (num_segments, CORE_ADDR);

  data->segment_sizes = XCALLOC (num_segments, CORE_ADDR);

  for (i = 0; i < num_segments; i++)

    {

      data->segment_bases[i] = segments[i]->p_vaddr;

      data->segment_sizes[i] = segments[i]->p_memsz;

    }

  num_sections = bfd_count_sections (abfd);

  data->segment_info = XCALLOC (num_sections, int);

  for (i = 0, sect = abfd->sections; sect != NULL; i++, sect = sect->next)

    {

      int j;

      CORE_ADDR vma;

      if ((bfd_get_section_flags (abfd, sect) & SEC_ALLOC) == 0)

        continue;

      vma = bfd_get_section_vma (abfd, sect);

      for (j = 0; j < num_segments; j++)

        if (segments[j]->p_memsz > 0

            && vma >= segments[j]->p_vaddr

            && vma < segments[j]->p_vaddr + segments[j]->p_memsz)

          {

            data->segment_info[i] = j + 1;

            break;

          }

      if (bfd_get_section_size (sect) > 0 && j == num_segments)

        warning (_("Loadable segment \"%s\" outside of ELF segments"),

                 bfd_section_name (abfd, sect));

    }

  return data;

}

/* We are called once per section from elf_symfile_read.  We

   need to examine each section we are passed, check to see

   if it is something we are interested in processing, and

   if so, stash away some access information for the section.

   For now we recognize the dwarf debug information sections and

   line number sections from matching their section names.  The

   ELF definition is no real help here since it has no direct

   knowledge of DWARF (by design, so any debugging format can be

   used).

   We also recognize the ".stab" sections used by the Sun compilers

   released with Solaris 2.

   FIXME: The section names should not be hardwired strings (what

   should they be?  I don't think most object file formats have enough

   section flags to specify what kind of debug section it is

   -kingdon).  */

static void

elf_locate_sections (bfd *ignore_abfd, asection *sectp, void *eip)

{

  struct elfinfo *ei;

  ei = (struct elfinfo *) eip;

  if (strcmp (sectp->name, ".stab") == 0)

    {

      ei->stabsect = sectp;

    }

  else if (strcmp (sectp->name, ".stab.index") == 0)

    {

      ei->stabindexsect = sectp;

    }

  else if (strcmp (sectp->name, ".mdebug") == 0)

    {

      ei->mdebugsect = sectp;

    }

}

static struct minimal_symbol *

record_minimal_symbol (char *name, CORE_ADDR address,

                       enum minimal_symbol_type ms_type,

                       asection *bfd_section, struct objfile *objfile)

{

  if (ms_type == mst_text || ms_type == mst_file_text)

    address = gdbarch_smash_text_address (current_gdbarch, address);

  return prim_record_minimal_symbol_and_info

    (name, address, ms_type, NULL, bfd_section->index, bfd_section, objfile);

}

/*

   LOCAL FUNCTION

   elf_symtab_read -- read the symbol table of an ELF file

   SYNOPSIS

   void elf_symtab_read (struct objfile *objfile, int type,

                         long number_of_symbols, asymbol **symbol_table)

   DESCRIPTION

   Given an objfile, a symbol table, and a flag indicating whether the

   symbol table contains regular, dynamic, or synthetic symbols, add all

   the global function and data symbols to the minimal symbol table.

   In stabs-in-ELF, as implemented by Sun, there are some local symbols

   defined in the ELF symbol table, which can be used to locate

   the beginnings of sections from each ".o" file that was linked to

   form the executable objfile.  We gather any such info and record it

   in data structures hung off the objfile's private data.

 */

#define ST_REGULAR 0

#define ST_DYNAMIC 1

#define ST_SYNTHETIC 2

static void

elf_symtab_read (struct objfile *objfile, int type,

                 long number_of_symbols, asymbol **symbol_table)

{

  long storage_needed;

  asymbol *sym;

  long i;

  CORE_ADDR symaddr;

  CORE_ADDR offset;

  enum minimal_symbol_type ms_type;

  /* If sectinfo is nonNULL, it contains section info that should end up

     filed in the objfile.  */

  struct stab_section_info *sectinfo = NULL;

  /* If filesym is nonzero, it points to a file symbol, but we haven't

     seen any section info for it yet.  */

  asymbol *filesym = 0;

  /* Name of filesym, as saved on the objfile_obstack.  */

  char *filesymname = obsavestring ("", 0, &objfile->objfile_obstack);

  struct dbx_symfile_info *dbx = objfile->deprecated_sym_stab_info;

  int stripped = (bfd_get_symcount (objfile->obfd) == 0);

  for (i = 0; i < number_of_symbols; i++)

    {

      sym = symbol_table[i];

      if (sym->name == NULL || *sym->name == '\0')

        {

          /* Skip names that don't exist (shouldn't happen), or names

             that are null strings (may happen). */

          continue;

        }

      /* Skip "special" symbols, e.g. ARM mapping symbols.  These are

         symbols which do not correspond to objects in the symbol table,

         but have some other target-specific meaning.  */

      if (bfd_is_target_special_symbol (objfile->obfd, sym))

        continue;

      offset = ANOFFSET (objfile->section_offsets, sym->section->index);

      if (type == ST_DYNAMIC

          && sym->section == &bfd_und_section

          && (sym->flags & BSF_FUNCTION))

        {

          struct minimal_symbol *msym;

          bfd *abfd = objfile->obfd;

          asection *sect;

          /* Symbol is a reference to a function defined in

             a shared library.

             If its value is non zero then it is usually the address

             of the corresponding entry in the procedure linkage table,

             plus the desired section offset.

             If its value is zero then the dynamic linker has to resolve

             the symbol. We are unable to find any meaningful address

             for this symbol in the executable file, so we skip it.  */

          symaddr = sym->value;

          if (symaddr == 0)

            continue;

          /* sym->section is the undefined section.  However, we want to

             record the section where the PLT stub resides with the

             minimal symbol.  Search the section table for the one that

             covers the stub's address.  */

          for (sect = abfd->sections; sect != NULL; sect = sect->next)

            {

              if ((bfd_get_section_flags (abfd, sect) & SEC_ALLOC) == 0)

                continue;

              if (symaddr >= bfd_get_section_vma (abfd, sect)

                  && symaddr < bfd_get_section_vma (abfd, sect)

                               + bfd_get_section_size (sect))

                break;

            }

          if (!sect)

            continue;

          symaddr += ANOFFSET (objfile->section_offsets, sect->index);

          msym = record_minimal_symbol

            ((char *) sym->name, symaddr, mst_solib_trampoline, sect, objfile);

          if (msym != NULL)

            msym->filename = filesymname;

          continue;

        }

      /* If it is a nonstripped executable, do not enter dynamic

         symbols, as the dynamic symbol table is usually a subset

         of the main symbol table.  */

      if (type == ST_DYNAMIC && !stripped)

        continue;

      if (sym->flags & BSF_FILE)

        {

          /* STT_FILE debugging symbol that helps stabs-in-elf debugging.

             Chain any old one onto the objfile; remember new sym.  */

          if (sectinfo != NULL)

            {

              sectinfo->next = dbx->stab_section_info;

              dbx->stab_section_info = sectinfo;

              sectinfo = NULL;

            }

          filesym = sym;

          filesymname =

            obsavestring ((char *) filesym->name, strlen (filesym->name),

                          &objfile->objfile_obstack);

        }

      else if (sym->flags & BSF_SECTION_SYM)

        continue;

      else if (sym->flags & (BSF_GLOBAL | BSF_LOCAL | BSF_WEAK))

        {

          struct minimal_symbol *msym;

          /* Select global/local/weak symbols.  Note that bfd puts abs

             symbols in their own section, so all symbols we are

             interested in will have a section. */

          /* Bfd symbols are section relative. */

          symaddr = sym->value + sym->section->vma;

          /* Relocate all non-absolute symbols by the section offset.  */

          if (sym->section != &bfd_abs_section)

            {

              symaddr += offset;

            }

          /* For non-absolute symbols, use the type of the section

             they are relative to, to intuit text/data.  Bfd provides

             no way of figuring this out for absolute symbols. */

          if (sym->section == &bfd_abs_section)

            {

              /* This is a hack to get the minimal symbol type

                 right for Irix 5, which has absolute addresses

                 with special section indices for dynamic symbols.

                 NOTE: uweigand-20071112: Synthetic symbols do not

                 have an ELF-private part, so do not touch those.  */

              unsigned short shndx = type == ST_SYNTHETIC ? 0 :

                ((elf_symbol_type *) sym)->internal_elf_sym.st_shndx;

              switch (shndx)

                {

                case SHN_MIPS_TEXT:

                  ms_type = mst_text;

                  break;

                case SHN_MIPS_DATA:

                  ms_type = mst_data;

                  break;

                case SHN_MIPS_ACOMMON:

                  ms_type = mst_bss;

                  break;

                default:

                  ms_type = mst_abs;

                }

              /* If it is an Irix dynamic symbol, skip section name

                 symbols, relocate all others by section offset. */

              if (ms_type != mst_abs)

                {

                  if (sym->name[0] == '.')

                    continue;

                  symaddr += offset;

                }

            }

          else if (sym->section->flags & SEC_CODE)

            {

              if (sym->flags & (BSF_GLOBAL | BSF_WEAK))

                {

                  ms_type = mst_text;

                }

              else if ((sym->name[0] == '.' && sym->name[1] == 'L')

                       || ((sym->flags & BSF_LOCAL)

                           && sym->name[0] == '$'

                           && sym->name[1] == 'L'))

                /* Looks like a compiler-generated label.  Skip

                   it.  The assembler should be skipping these (to

                   keep executables small), but apparently with

                   gcc on the (deleted) delta m88k SVR4, it loses.

                   So to have us check too should be harmless (but

                   I encourage people to fix this in the assembler

                   instead of adding checks here).  */

                continue;

              else

                {

                  ms_type = mst_file_text;

                }

            }

          else if (sym->section->flags & SEC_ALLOC)

            {

              if (sym->flags & (BSF_GLOBAL | BSF_WEAK))

                {

                  if (sym->section->flags & SEC_LOAD)

                    {

                      ms_type = mst_data;

                    }

                  else

                    {

                      ms_type = mst_bss;

                    }

                }

              else if (sym->flags & BSF_LOCAL)

                {

                  /* Named Local variable in a Data section.

                     Check its name for stabs-in-elf.  */

                  int special_local_sect;

                  if (strcmp ("Bbss.bss", sym->name) == 0)

                    special_local_sect = SECT_OFF_BSS (objfile);

                  else if (strcmp ("Ddata.data", sym->name) == 0)

                    special_local_sect = SECT_OFF_DATA (objfile);

                  else if (strcmp ("Drodata.rodata", sym->name) == 0)

                    special_local_sect = SECT_OFF_RODATA (objfile);

                  else

                    special_local_sect = -1;

                  if (special_local_sect >= 0)

                    {

                      /* Found a special local symbol.  Allocate a

                         sectinfo, if needed, and fill it in.  */

                      if (sectinfo == NULL)

                        {

                          int max_index;

                          size_t size;

                          max_index

                            = max (SECT_OFF_BSS (objfile),

                                   max (SECT_OFF_DATA (objfile),

                                        SECT_OFF_RODATA (objfile)));

                          /* max_index is the largest index we'll

                             use into this array, so we must

                             allocate max_index+1 elements for it.

                             However, 'struct stab_section_info'

                             already includes one element, so we

                             need to allocate max_index aadditional

                             elements.  */

                          size = (sizeof (struct stab_section_info)

                                  + (sizeof (CORE_ADDR)

                                     * max_index));

                          sectinfo = (struct stab_section_info *)

                            xmalloc (size);

                          memset (sectinfo, 0, size);

                          sectinfo->num_sections = max_index;

                          if (filesym == NULL)

                            {

                              complaint (&symfile_complaints,

                                         _("elf/stab section information %s without a preceding file symbol"),

                                         sym->name);

                            }

                          else

                            {

                              sectinfo->filename =

                                (char *) filesym->name;

                            }

                        }

                      if (sectinfo->sections[special_local_sect] != 0)

                        complaint (&symfile_complaints,

                                   _("duplicated elf/stab section information for %s"),

                                   sectinfo->filename);

                      /* BFD symbols are section relative.  */

                      symaddr = sym->value + sym->section->vma;

                      /* Relocate non-absolute symbols by the

                         section offset.  */

                      if (sym->section != &bfd_abs_section)

                        symaddr += offset;

                      sectinfo->sections[special_local_sect] = symaddr;

                      /* The special local symbols don't go in the

                         minimal symbol table, so ignore this one.  */

                      continue;

                    }

                  /* Not a special stabs-in-elf symbol, do regular

                     symbol processing.  */

                  if (sym->section->flags & SEC_LOAD)

                    {

                      ms_type = mst_file_data;

                    }

                  else

                    {

                      ms_type = mst_file_bss;

                    }

                }

              else

                {

                  ms_type = mst_unknown;

                }

            }

          else

            {

              /* FIXME:  Solaris2 shared libraries include lots of

                 odd "absolute" and "undefined" symbols, that play

                 hob with actions like finding what function the PC

                 is in.  Ignore them if they aren't text, data, or bss.  */

              /* ms_type = mst_unknown; */

              continue; /* Skip this symbol. */

            }

          msym = record_minimal_symbol

            ((char *) sym->name, symaddr,

             ms_type, sym->section, objfile);

          if (msym)

            {

              /* Pass symbol size field in via BFD.  FIXME!!!  */

              elf_symbol_type *elf_sym;

              /* NOTE: uweigand-20071112: A synthetic symbol does not have an

                 ELF-private part.  However, in some cases (e.g. synthetic

                 'dot' symbols on ppc64) the udata.p entry is set to point back

                 to the original ELF symbol it was derived from.  Get the size

                 from that symbol.  */

              if (type != ST_SYNTHETIC)

                elf_sym = (elf_symbol_type *) sym;

              else

                elf_sym = (elf_symbol_type *) sym->udata.p;

              if (elf_sym)

                MSYMBOL_SIZE(msym) = elf_sym->internal_elf_sym.st_size;

            }

          if (msym != NULL)

            msym->filename = filesymname;

          gdbarch_elf_make_msymbol_special (current_gdbarch, sym, msym);

        }

    }

}

/* Scan and build partial symbols for a symbol file.

   We have been initialized by a call to elf_symfile_init, which

   currently does nothing.

   SECTION_OFFSETS is a set of offsets to apply to relocate the symbols

   in each section.  We simplify it down to a single offset for all

   symbols.  FIXME.

   MAINLINE is true if we are reading the main symbol

   table (as opposed to a shared lib or dynamically loaded file).

   This function only does the minimum work necessary for letting the

   user "name" things symbolically; it does not read the entire symtab.

   Instead, it reads the external and static symbols and puts them in partial

   symbol tables.  When more extensive information is requested of a

   file, the corresponding partial symbol table is mutated into a full

   fledged symbol table by going back and reading the symbols

   for real.

   We look for sections with specific names, to tell us what debug

   format to look for:  FIXME!!!

   elfstab_build_psymtabs() handles STABS symbols;

   mdebug_build_psymtabs() handles ECOFF debugging information.

   Note that ELF files have a "minimal" symbol table, which looks a lot

   like a COFF symbol table, but has only the minimal information necessary

   for linking.  We process this also, and use the information to

   build gdb's minimal symbol table.  This gives us some minimal debugging

   capability even for files compiled without -g.  */

static void

elf_symfile_read (struct objfile *objfile, int mainline)

{

  bfd *abfd = objfile->obfd;

  struct elfinfo ei;

  struct cleanup *back_to;

  CORE_ADDR offset;

  long symcount = 0, dynsymcount = 0, synthcount, storage_needed;

  asymbol **symbol_table = NULL, **dyn_symbol_table = NULL;

  asymbol *synthsyms;

  init_minimal_symbol_collection ();

  back_to = make_cleanup_discard_minimal_symbols ();

  memset ((char *) &ei, 0, sizeof (ei));

  /* Allocate struct to keep track of the symfile */

  objfile->deprecated_sym_stab_info = (struct dbx_symfile_info *)

    xmalloc (sizeof (struct dbx_symfile_info));

  memset ((char *) objfile->deprecated_sym_stab_info, 0, sizeof (struct dbx_symfile_info));

  make_cleanup (free_elfinfo, (void *) objfile);

  /* Process the normal ELF symbol table first.  This may write some

     chain of info into the dbx_symfile_info in objfile->deprecated_sym_stab_info,

     which can later be used by elfstab_offset_sections.  */

  storage_needed = bfd_get_symtab_upper_bound (objfile->obfd);

  if (storage_needed < 0)

    error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile->obfd),

           bfd_errmsg (bfd_get_error ()));

  if (storage_needed > 0)

    {

      symbol_table = (asymbol **) xmalloc (storage_needed);

      make_cleanup (xfree, symbol_table);

      symcount = bfd_canonicalize_symtab (objfile->obfd, symbol_table);

      if (symcount < 0)

        error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile->obfd),

               bfd_errmsg (bfd_get_error ()));

      elf_symtab_read (objfile, ST_REGULAR, symcount, symbol_table);

    }

  /* Add the dynamic symbols.  */

  storage_needed = bfd_get_dynamic_symtab_upper_bound (objfile->obfd);

  if (storage_needed > 0)

    {

      dyn_symbol_table = (asymbol **) xmalloc (storage_needed);

      make_cleanup (xfree, dyn_symbol_table);

      dynsymcount = bfd_canonicalize_dynamic_symtab (objfile->obfd,

                                                     dyn_symbol_table);

      if (dynsymcount < 0)

        error (_("Can't read symbols from %s: %s"), bfd_get_filename (objfile->obfd),

               bfd_errmsg (bfd_get_error ()));

      elf_symtab_read (objfile, ST_DYNAMIC, dynsymcount, dyn_symbol_table);

    }

  /* Add synthetic symbols - for instance, names for any PLT entries.  */

  synthcount = bfd_get_synthetic_symtab (abfd, symcount, symbol_table,

                                         dynsymcount, dyn_symbol_table,

                                         &synthsyms);

  if (synthcount > 0)

    {

      asymbol **synth_symbol_table;

      long i;

      make_cleanup (xfree, synthsyms);

      synth_symbol_table = xmalloc (sizeof (asymbol *) * synthcount);

      for (i = 0; i < synthcount; i++)

        synth_symbol_table[i] = synthsyms + i;

      make_cleanup (xfree, synth_symbol_table);

      elf_symtab_read (objfile, ST_SYNTHETIC, synthcount, synth_symbol_table);

    }

  /* Install any minimal symbols that have been collected as the current

     minimal symbols for this objfile.  The debug readers below this point

     should not generate new minimal symbols; if they do it's their

     responsibility to install them.  "mdebug" appears to be the only one

     which will do this.  */

  install_minimal_symbols (objfile);

  do_cleanups (back_to);

  /* Now process debugging information, which is contained in

     special ELF sections. */

  /* If we are reinitializing, or if we have never loaded syms yet,

     set table to empty.  MAINLINE is cleared so that *_read_psymtab

     functions do not all also re-initialize the psymbol table. */

  if (mainline)

    {

      init_psymbol_list (objfile, 0);

      mainline = 0;

    }

  /* We first have to find them... */

  bfd_map_over_sections (abfd, elf_locate_sections, (void *) & ei);

  /* ELF debugging information is inserted into the psymtab in the

     order of least informative first - most informative last.  Since

     the psymtab table is searched `most recent insertion first' this

     increases the probability that more detailed debug information

     for a section is found.

     For instance, an object file might contain both .mdebug (XCOFF)

     and .debug_info (DWARF2) sections then .mdebug is inserted first

     (searched last) and DWARF2 is inserted last (searched first).  If

     we don't do this then the XCOFF info is found first - for code in

     an included file XCOFF info is useless. */

  if (ei.mdebugsect)

    {

      const struct ecoff_debug_swap *swap;

      /* .mdebug section, presumably holding ECOFF debugging

         information.  */

      swap = get_elf_backend_data (abfd)->elf_backend_ecoff_debug_swap;

      if (swap)

        elfmdebug_build_psymtabs (objfile, swap, ei.mdebugsect);

    }

  if (ei.stabsect)

    {

      asection *str_sect;

      /* Stab sections have an associated string table that looks like

         a separate section.  */

      str_sect = bfd_get_section_by_name (abfd, ".stabstr");

      /* FIXME should probably warn about a stab section without a stabstr.  */

      if (str_sect)

        elfstab_build_psymtabs (objfile,

                                mainline,

                                ei.stabsect,

                                str_sect->filepos,

                                bfd_section_size (abfd, str_sect));

    }

  if (dwarf2_has_info (objfile))

    {

      /* DWARF 2 sections */

      dwarf2_build_psymtabs (objfile, mainline);

    }

  /* FIXME: kettenis/20030504: This still needs to be integrated with

     dwarf2read.c in a better way.  */

  dwarf2_build_frame_info (objfile);

}

/* This cleans up the objfile's deprecated_sym_stab_info pointer, and

   the chain of stab_section_info's, that might be dangling from

   it.  */

static void

free_elfinfo (void *objp)

{