gdb/symfile-mem.c

   1 /* Reading symbol files from memory.
   2
   3    Copyright 1986, 1987, 1989, 1991, 1994, 1995, 1996, 1998, 2000,
   4    2001, 2002, 2003, 2004 Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 59 Temple Place - Suite 330,
  21    Boston, MA 02111-1307, USA.  */
  22
  23 /* This file defines functions (and commands to exercise those
  24    functions) for reading debugging information from object files
  25    whose images are mapped directly into the inferior's memory.  For
  26    example, the Linux kernel maps a "syscall DSO" into each process's
  27    address space; this DSO provides kernel-specific code for some
  28    system calls.
  29
  30    At the moment, BFD only has functions for parsing object files from
  31    memory for the ELF format, even though the general idea isn't
  32    ELF-specific.  This means that BFD only provides the functions GDB
  33    needs when configured for ELF-based targets.  So these functions
  34    may only be compiled on ELF-based targets.
  35
  36    GDB has no idea whether it has been configured for an ELF-based
  37    target or not: it just tries to handle whatever files it is given.
  38    But this means there are no preprocessor symbols on which we could
  39    make these functions' compilation conditional.
  40
  41    So, for the time being, we put these functions alone in this file,
  42    and have .mt files reference them as appropriate.  In the future, I
  43    hope BFD will provide a format-independent bfd_from_remote_memory
  44    entry point.  */
  45
  46
  47 #include "defs.h"
  48 #include "symtab.h"
  49 #include "gdbcore.h"
  50 #include "objfiles.h"
  51 #include "gdbcmd.h"
  52 #include "target.h"
  53 #include "value.h"
  54 #include "symfile.h"
  55 #include "symfile-mem.h"
  56
  57
  58 /* Read inferior memory at ADDR to find the header of a loaded object file
  59    and read its in-core symbols out of inferior memory.  TEMPL is a bfd
  60    representing the target's format.  */
  61 struct objfile *
  62 symbol_file_add_from_memory (bfd *templ, CORE_ADDR addr, int from_tty)
  63 {
  64   struct objfile *objf;
  65   bfd *nbfd;
  66   asection *sec;
  67   bfd_vma loadbase;
  68   struct section_addr_info *sai;
  69   unsigned int i;
  70
  71   if (bfd_get_flavour (templ) != bfd_target_elf_flavour)
  72     error ("add-symbol-file-from-memory not supported for this target");
  73
  74   nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, &loadbase,
  75                                          target_read_memory);
  76   if (nbfd == NULL)
  77     {
  78       error ("Failed to read a valid object file image from memory.");
  79       return NULL;
  80     }
  81
  82   nbfd->filename = xstrdup ("shared object read from target memory");
  83
  84   if (!bfd_check_format (nbfd, bfd_object))
  85     {
  86       /* FIXME: should be checking for errors from bfd_close (for one thing,
  87          on error it does not free all the storage associated with the
  88          bfd).  */
  89       bfd_close (nbfd);
  90       error ("Got object file from memory but can't read symbols: %s.",
  91              bfd_errmsg (bfd_get_error ()));
  92       return NULL;
  93     }
  94
  95   sai = alloc_section_addr_info (bfd_count_sections (nbfd));
  96   make_cleanup (xfree, sai);
  97   i = 0;
  98   for (sec = nbfd->sections; sec != NULL; sec = sec->next)
  99     if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
 100       {
 101         sai->other[i].addr = bfd_get_section_vma (nbfd, sec) + loadbase;
 102         sai->other[i].name = (char *) bfd_get_section_name (nbfd, sec);
 103         sai->other[i].sectindex = sec->index;
 104         ++i;
 105       }
 106
 107   objf = symbol_file_add_from_bfd (nbfd, from_tty,
 108                                    sai, 0, OBJF_SHARED);
 109
 110   /* This might change our ideas about frames already looked at.  */
 111   reinit_frame_cache ();
 112
 113   return objf;
 114 }
 115
 116
 117 static void
 118 add_symbol_file_from_memory_command (char *args, int from_tty)
 119 {
 120   CORE_ADDR addr;
 121   bfd *templ;
 122
 123   if (args == NULL)
 124     error ("add-symbol-file-from-memory requires an expression argument");
 125
 126   addr = parse_and_eval_address (args);
 127
 128   /* We need some representative bfd to know the target we are looking at.  */
 129   if (symfile_objfile != NULL)
 130     templ = symfile_objfile->obfd;
 131   else
 132     templ = exec_bfd;
 133   if (templ == NULL)
 134     error ("\
 135 Must use symbol-file or exec-file before add-symbol-file-from-memory.");
 136
 137   symbol_file_add_from_memory (templ, addr, from_tty);
 138 }
 139
 140 \f
 141 void
 142 _initialize_symfile_mem ()
 143 {
 144   add_cmd ("add-symbol-file-from-memory", class_files,
 145            add_symbol_file_from_memory_command,
 146            "\
 147 Load the symbols out of memory from a dynamically loaded object file.\n\
 148 Give an expression for the address of the file's shared object file header.",
 149            &cmdlist);
 150
 151 }