path: root/gdb/elfread.c

/* Read ELF (Executable and Linking Format) object files for GDB.
   Copyright 1991, 1992 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 2 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, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "defs.h"
#include "bfd.h"
#include <time.h> /* For time_t in libbfd.h.  */
#include <sys/types.h> /* For time_t, if not in time.h.  */
#include "libbfd.h"		/* For bfd_elf_find_section */
#include "libelf.h"
#include "symtab.h"
#include "symfile.h"
#include "objfiles.h"
#include "buildsym.h"
#include "stabsread.h"
#include "gdb-stabs.h"
#include "complaints.h"
#include <string.h>
#include "demangle.h"

/* The struct elfinfo is available only during ELF symbol table and
   psymtab reading.  It is destroyed at the complation of psymtab-reading.
   It's local to elf_symfile_read.  */

struct elfinfo {
  file_ptr dboffset;		/* Offset to dwarf debug section */
  unsigned int dbsize;		/* Size of dwarf debug section */
  file_ptr lnoffset;		/* Offset to dwarf line number section */
  unsigned int lnsize;		/* Size of dwarf line number section */
  asection *stabsect;		/* Section pointer for .stab section */
  asection *stabindexsect;	/* Section pointer for .stab.index section */
};

/* Various things we might complain about... */

struct complaint section_info_complaint = 
  {"elf/stab section information %s without a preceding file symbol", 0, 0};

struct complaint section_info_dup_complaint = 
  {"duplicated elf/stab section information for %s", 0, 0};

struct complaint stab_info_mismatch_complaint = 
  {"elf/stab section information missing for %s", 0, 0};

struct complaint stab_info_questionable_complaint = 
  {"elf/stab section information questionable for %s", 0, 0};

static void
elf_symfile_init PARAMS ((struct objfile *));

static void
elf_new_init PARAMS ((struct objfile *));

static void
elf_symfile_read PARAMS ((struct objfile *, struct section_offsets *, int));

static void
elf_symfile_finish PARAMS ((struct objfile *));

static void
elf_symtab_read PARAMS ((bfd *,  CORE_ADDR, struct objfile *));

static void
free_elfinfo PARAMS ((void *));

static struct section_offsets *
elf_symfile_offsets PARAMS ((struct objfile *, CORE_ADDR));

static void
record_minimal_symbol_and_info PARAMS ((char *, CORE_ADDR,
					enum minimal_symbol_type, char *,
					struct objfile *));

static void
elf_locate_sections PARAMS ((bfd *, asection *, void *));

/* 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 (ignore_abfd, sectp, eip)
     bfd *ignore_abfd;
     asection *sectp;
     PTR eip;
{
  register struct elfinfo *ei;

  ei = (struct elfinfo *) eip;
  if (STREQ (sectp -> name, ".debug"))
    {
      ei -> dboffset = sectp -> filepos;
      ei -> dbsize = bfd_get_section_size_before_reloc (sectp);
    }
  else if (STREQ (sectp -> name, ".line"))
    {
      ei -> lnoffset = sectp -> filepos;
      ei -> lnsize = bfd_get_section_size_before_reloc (sectp);
    }
  else if (STREQ (sectp -> name, ".stab"))
    {
      ei -> stabsect = sectp;
    }
  else if (STREQ (sectp -> name, ".stab.index"))
    {
      ei -> stabindexsect = sectp;
    }
}

#if 0	/* Currently unused */

char *
elf_interpreter (abfd)
     bfd *abfd;
{
  sec_ptr interp_sec;
  unsigned size;
  char *interp = NULL;

  interp_sec = bfd_get_section_by_name (abfd, ".interp");
  if (interp_sec)
    {
      size = bfd_section_size (abfd, interp_sec);
      interp = alloca (size);
      if (bfd_get_section_contents (abfd, interp_sec, interp, (file_ptr)0,
				    size))
	{
	  interp = savestring (interp, size - 1);
	}
      else
	{
	  interp = NULL;
	}
    }
  return (interp);
}

#endif

static void
record_minimal_symbol_and_info (name, address, ms_type, info, objfile)
     char *name;
     CORE_ADDR address;
     enum minimal_symbol_type ms_type;
     char *info;		/* FIXME, is this really char *? */
     struct objfile *objfile;
{
  int section;

  /* Guess the section from the type.  This is likely to be wrong in
     some cases.  */
  switch (ms_type)
    {
    case mst_text:
    case mst_file_text:
      section = SECT_OFF_TEXT;
      break;
    case mst_data:
    case mst_file_data:
      section = SECT_OFF_DATA;
      break;
    case mst_bss:
    case mst_file_bss:
      section = SECT_OFF_BSS;
      break;
    default:
      section = -1;
      break;
    }

  name = obsavestring (name, strlen (name), &objfile -> symbol_obstack);
  prim_record_minimal_symbol_and_info (name, address, ms_type, info, section);
}

/*

LOCAL FUNCTION

	elf_symtab_read -- read the symbol table of an ELF file

SYNOPSIS

	void elf_symtab_read (bfd *abfd, CORE_ADDR addr,
			      struct objfile *objfile)

DESCRIPTION

	Given an open bfd, a base address to relocate symbols to, and a
	flag that specifies whether or not this bfd is for an executable
	or not (may be shared library for example), 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.

*/

static void
elf_symtab_read (abfd, addr, objfile)
     bfd *abfd;
     CORE_ADDR addr;
     struct objfile *objfile;
{
  unsigned int storage_needed;
  asymbol *sym;
  asymbol **symbol_table;
  unsigned int number_of_symbols;
  unsigned int i;
  int index;
  struct cleanup *back_to;
  CORE_ADDR symaddr;
  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;
  struct dbx_symfile_info *dbx = (struct dbx_symfile_info *)
				 objfile->sym_stab_info;
  unsigned long size;
  
  storage_needed = get_symtab_upper_bound (abfd);
  if (storage_needed > 0)
    {
      symbol_table = (asymbol **) xmalloc (storage_needed);
      back_to = make_cleanup (free, symbol_table);
      number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table); 
      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;
	    }
	  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;
	    }
	  else if (sym -> flags & (BSF_GLOBAL | BSF_LOCAL | BSF_WEAK))
	    {
	      /* 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 base address.  */
	      if (sym -> section != &bfd_abs_section)
		{
		  symaddr += addr;
		}
	      /* 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)
		{
		  ms_type = mst_abs;
		}
	      else if (sym -> section -> flags & SEC_CODE)
		{
		  if (sym -> flags & BSF_GLOBAL)
		    {
		      ms_type = mst_text;
		    }
		  else if (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
		       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_DATA)
		{
		  if (sym -> flags & BSF_GLOBAL)
		    {
		      if (sym -> section -> flags & SEC_HAS_CONTENTS)
			{
			  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.  The STREQ macro checks the
			 first character inline, so we only actually do a
			 strcmp function call on names that start with 'B'
			 or 'D' */
		      index = SECT_OFF_MAX;
		      if (STREQ ("Bbss.bss", sym -> name))
			{
			  index = SECT_OFF_BSS;
			}
		      else if (STREQ ("Ddata.data", sym -> name))
			{
			  index = SECT_OFF_DATA;
			}
		      else if (STREQ ("Drodata.rodata", sym -> name))
			{
			  index = SECT_OFF_RODATA;
			}
		      if (index != SECT_OFF_MAX)
			{
			  /* Found a special local symbol.  Allocate a
			     sectinfo, if needed, and fill it in.  */
			  if (sectinfo == NULL)
			    {
			      sectinfo = (struct stab_section_info *)
				xmmalloc (objfile -> md, sizeof (*sectinfo));
			      memset ((PTR) sectinfo, 0, sizeof (*sectinfo));
			      if (filesym == NULL)
				{
				  complain (&section_info_complaint,
					    sym -> name);
				}
			      else
				{
				  sectinfo -> filename =
				    (char *) filesym -> name;
				}
			    }
			  if (sectinfo -> sections[index] != 0)
			    {
			      complain (&section_info_dup_complaint,
					sectinfo -> filename);
			    }
			  /* Bfd symbols are section relative. */
			  symaddr = sym -> value + sym -> section -> vma;
			  /* Relocate non-absolute symbols by base address.  */
			  if (sym -> section != &bfd_abs_section)
			    {
			      symaddr += addr;
			    }
			  sectinfo -> sections[index] = 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_HAS_CONTENTS)
			{
			  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. */
		}
	      /* Pass symbol size field in via BFD.  FIXME!!!  */
	      size = ((elf_symbol_type *) sym) -> internal_elf_sym.st_size;
	      record_minimal_symbol_and_info ((char *) sym -> name, symaddr,
					      ms_type, (PTR) size, objfile);
	    }
	}
      do_cleanups (back_to);
    }
}

/* 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!!!

   dwarf_build_psymtabs() builds psymtabs for DWARF symbols;
   elfstab_build_psymtabs() handles STABS symbols.

   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 (objfile, section_offsets, mainline)
     struct objfile *objfile;
     struct section_offsets *section_offsets;
     int mainline;
{
  bfd *abfd = objfile->obfd;
  struct elfinfo ei;
  struct cleanup *back_to;
  CORE_ADDR offset;

  init_minimal_symbol_collection ();
  back_to = make_cleanup (discard_minimal_symbols, 0);

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

  /* Allocate struct to keep track of the symfile */
  objfile->sym_stab_info = (PTR)
    xmmalloc (objfile -> md, sizeof (struct dbx_symfile_info));
  memset ((char *) objfile->sym_stab_info, 0, sizeof (struct dbx_symfile_info));
  make_cleanup (free_elfinfo, (PTR) objfile);

  /* Process the normal ELF symbol table first.  This may write some 
     chain of info into the dbx_symfile_info in objfile->sym_stab_info,
     which can later be used by elfstab_offset_sections.  */

  /* FIXME, should take a section_offsets param, not just an offset.  */
  offset = ANOFFSET (section_offsets, 0);
  elf_symtab_read (abfd, offset, objfile);

  /* Now process debugging information, which is contained in
     special ELF sections.  We first have to find them... */

  bfd_map_over_sections (abfd, elf_locate_sections, (PTR) &ei);
  if (ei.dboffset && ei.lnoffset)
    {
      /* DWARF sections */
      dwarf_build_psymtabs (objfile,
			    section_offsets, mainline,
			    ei.dboffset, ei.dbsize,
			    ei.lnoffset, ei.lnsize);
    }
  if (ei.stabsect)
    {
      /* STABS sections */

      /* FIXME:  Sun didn't really know how to implement this well.
	 They made .stab sections that don't point to the .stabstr
	 section with the sh_link field.  BFD doesn't make string table
	 sections visible to the caller.  So we have to search the
	 ELF section table, not the BFD section table, for the string
	 table.  */
      struct elf32_internal_shdr *elf_sect;

      elf_sect = bfd_elf_find_section (abfd, ".stabstr");
      if (elf_sect)
	elfstab_build_psymtabs (objfile,
  	  section_offsets,
	  mainline,
	  ei.stabsect->filepos,				/* .stab offset */
	  bfd_get_section_size_before_reloc (ei.stabsect),/* .stab size */
	  (file_ptr) elf_sect->sh_offset,		/* .stabstr offset */
	  elf_sect->sh_size);				/* .stabstr size */
    }

  if (!have_partial_symbols ())
    {
      wrap_here ("");
      printf_filtered ("(no debugging symbols found)...");
      wrap_here ("");
    }

  /* Install any minimal symbols that have been collected as the current
     minimal symbols for this objfile. */

  install_minimal_symbols (objfile);

  do_cleanups (back_to);
}

/* This cleans up the objfile's sym_stab_info pointer, and the chain of
   stab_section_info's, that might be dangling from it.  */

static void
free_elfinfo (objp)
     PTR objp;
{
  struct objfile *objfile = (struct objfile *)objp;
  struct dbx_symfile_info *dbxinfo = (struct dbx_symfile_info *)
				     objfile->sym_stab_info;
  struct stab_section_info *ssi, *nssi;

  ssi = dbxinfo->stab_section_info;
  while (ssi)
    {
      nssi = ssi->next;
      mfree (objfile->md, ssi);
      ssi = nssi;
    }

  dbxinfo->stab_section_info = 0;	/* Just say No mo info about this.  */
}


/* Initialize anything that needs initializing when a completely new symbol
   file is specified (not just adding some symbols from another file, e.g. a
   shared library).

   We reinitialize buildsym, since we may be reading stabs from an ELF file.  */

static void
elf_new_init (ignore)
     struct objfile *ignore;
{
  stabsread_new_init ();
  buildsym_new_init ();
}

/* Perform any local cleanups required when we are done with a particular
   objfile.  I.E, we are in the process of discarding all symbol information
   for an objfile, freeing up all memory held for it, and unlinking the
   objfile struct from the global list of known objfiles. */

static void
elf_symfile_finish (objfile)
     struct objfile *objfile;
{
  if (objfile -> sym_stab_info != NULL)
    {
      mfree (objfile -> md, objfile -> sym_stab_info);
    }
}

/* ELF specific initialization routine for reading symbols.

   It is passed a pointer to a struct sym_fns which contains, among other
   things, the BFD for the file whose symbols are being read, and a slot for
   a pointer to "private data" which we can fill with goodies.

   For now at least, we have nothing in particular to do, so this function is
   just a stub. */

static void
elf_symfile_init (ignore)
     struct objfile *ignore;
{
}

/* ELF specific parsing routine for section offsets.

   Plain and simple for now.  */

static
struct section_offsets *
elf_symfile_offsets (objfile, addr)
     struct objfile *objfile;
     CORE_ADDR addr;
{
  struct section_offsets *section_offsets;
  int i;
 
  section_offsets = (struct section_offsets *)
    obstack_alloc (&objfile -> psymbol_obstack,
		   sizeof (struct section_offsets) +
		          sizeof (section_offsets->offsets) * (SECT_OFF_MAX-1));

  for (i = 0; i < SECT_OFF_MAX; i++)
    ANOFFSET (section_offsets, i) = addr;
  
  return section_offsets;
}

/* When handling an ELF file that contains Sun STABS debug info,
   some of the debug info is relative to the particular chunk of the
   section that was generated in its individual .o file.  E.g.
   offsets to static variables are relative to the start of the data
   segment *for that module before linking*.  This information is
   painfully squirreled away in the ELF symbol table as local symbols
   with wierd names.  Go get 'em when needed.  */

void
elfstab_offset_sections (objfile, pst)
     struct objfile *objfile;
     struct partial_symtab *pst;
{
  char *filename = pst->filename;
  struct dbx_symfile_info *dbx = (struct dbx_symfile_info *)
				 objfile->sym_stab_info;
  struct stab_section_info *maybe = dbx->stab_section_info;
  struct stab_section_info *questionable = 0;
  int i;
  char *p;

  /* The ELF symbol info doesn't include path names, so strip the path
     (if any) from the psymtab filename.  */
  while (0 != (p = strchr (filename, '/')))
    filename = p+1;

  /* FIXME:  This linear search could speed up significantly
     if it was chained in the right order to match how we search it,
     and if we unchained when we found a match. */
  for (; maybe; maybe = maybe->next)
    {
      if (filename[0] == maybe->filename[0]
	  && STREQ (filename, maybe->filename))
	{
	  /* We found a match.  But there might be several source files
	     (from different directories) with the same name.  */
	  if (0 == maybe->found)
	    break;
	  questionable = maybe;		/* Might use it later.  */
	}
    }

  if (maybe == 0 && questionable != 0)
    {
      complain (&stab_info_questionable_complaint, filename);
      maybe = questionable;
    }

  if (maybe)
    {
      /* Found it!  Allocate a new psymtab struct, and fill it in.  */
      maybe->found++;
      pst->section_offsets = (struct section_offsets *)
	obstack_alloc (&objfile -> psymbol_obstack,
		       sizeof (struct section_offsets) +
	       sizeof (pst->section_offsets->offsets) * (SECT_OFF_MAX-1));

      for (i = 0; i < SECT_OFF_MAX; i++)
	ANOFFSET (pst->section_offsets, i) = maybe->sections[i];
      return;
    }

  /* We were unable to find any offsets for this file.  Complain.  */
  if (dbx->stab_section_info)		/* If there *is* any info, */
    complain (&stab_info_mismatch_complaint, filename);
}

/*  Register that we are able to handle ELF object file formats and DWARF
    debugging formats.

    Unlike other object file formats, where the debugging information format
    is implied by the object file format, the ELF object file format and the
    DWARF debugging information format are two distinct, and potentially
    separate entities.  I.E. it is perfectly possible to have ELF objects
    with debugging formats other than DWARF.  And it is conceivable that the
    DWARF debugging format might be used with another object file format,
    like COFF, by simply using COFF's custom section feature.

    GDB, and to a lesser extent BFD, should support the notion of separate
    object file formats and debugging information formats.  For now, we just
    use "elf" in the same sense as "a.out" or "coff", to imply both the ELF
    object file format and the DWARF debugging format. */

static struct sym_fns elf_sym_fns =
{
  "elf",		/* sym_name: name or name prefix of BFD target type */
  3,			/* sym_namelen: number of significant sym_name chars */
  elf_new_init,		/* sym_new_init: init anything gbl to entire symtab */
  elf_symfile_init,	/* sym_init: read initial info, setup for sym_read() */
  elf_symfile_read,	/* sym_read: read a symbol file into symtab */
  elf_symfile_finish,	/* sym_finish: finished with file, cleanup */
  elf_symfile_offsets,	/* sym_offsets:  Translate ext. to int. relocation */
  NULL			/* next: pointer to next struct sym_fns */
};

void
_initialize_elfread ()
{
  add_symtab_fns (&elf_sym_fns);
}