gdb/symfile-mem.c

   1 /* Reading symbol files from memory.
   2
   3    Copyright (C) 1986, 1987, 1989, 1991, 1994, 1995, 1996, 1998, 2000, 2001,
   4    2002, 2003, 2004, 2005, 2007, 2008, 2009 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 3 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, see <http://www.gnu.org/licenses/>.  */
  20
  21 /* This file defines functions (and commands to exercise those
  22    functions) for reading debugging information from object files
  23    whose images are mapped directly into the inferior's memory.  For
  24    example, the Linux kernel maps a "syscall DSO" into each process's
  25    address space; this DSO provides kernel-specific code for some
  26    system calls.
  27
  28    At the moment, BFD only has functions for parsing object files from
  29    memory for the ELF format, even though the general idea isn't
  30    ELF-specific.  This means that BFD only provides the functions GDB
  31    needs when configured for ELF-based targets.  So these functions
  32    may only be compiled on ELF-based targets.
  33
  34    GDB has no idea whether it has been configured for an ELF-based
  35    target or not: it just tries to handle whatever files it is given.
  36    But this means there are no preprocessor symbols on which we could
  37    make these functions' compilation conditional.
  38
  39    So, for the time being, we put these functions alone in this file,
  40    and have .mt files reference them as appropriate.  In the future, I
  41    hope BFD will provide a format-independent bfd_from_remote_memory
  42    entry point.  */
  43
  44
  45 #include "defs.h"
  46 #include "symtab.h"
  47 #include "gdbcore.h"
  48 #include "objfiles.h"
  49 #include "exceptions.h"
  50 #include "gdbcmd.h"
  51 #include "target.h"
  52 #include "value.h"
  53 #include "symfile.h"
  54 #include "observer.h"
  55 #include "auxv.h"
  56 #include "elf/common.h"
  57
  58
  59 /* Read inferior memory at ADDR to find the header of a loaded object file
  60    and read its in-core symbols out of inferior memory.  TEMPL is a bfd
  61    representing the target's format.  NAME is the name to use for this
  62    symbol file in messages; it can be NULL or a malloc-allocated string
  63    which will be attached to the BFD.  */
  64 static struct objfile *
  65 symbol_file_add_from_memory (struct bfd *templ, CORE_ADDR addr, char *name,
  66                              int from_tty)
  67 {
  68   struct objfile *objf;
  69   struct bfd *nbfd;
  70   struct bfd_section *sec;
  71   bfd_vma loadbase;
  72   struct section_addr_info *sai;
  73   unsigned int i;
  74
  75   if (bfd_get_flavour (templ) != bfd_target_elf_flavour)
  76     error (_("add-symbol-file-from-memory not supported for this target"));
  77
  78   nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, &loadbase,
  79                                          target_read_memory);
  80   if (nbfd == NULL)
  81     error (_("Failed to read a valid object file image from memory."));
  82
  83   if (name == NULL)
  84     nbfd->filename = xstrdup ("shared object read from target memory");
  85   else
  86     nbfd->filename = name;
  87
  88   if (!bfd_check_format (nbfd, bfd_object))
  89     {
  90       /* FIXME: should be checking for errors from bfd_close (for one thing,
  91          on error it does not free all the storage associated with the
  92          bfd).  */
  93       bfd_close (nbfd);
  94       error (_("Got object file from memory but can't read symbols: %s."),
  95              bfd_errmsg (bfd_get_error ()));
  96     }
  97
  98   sai = alloc_section_addr_info (bfd_count_sections (nbfd));
  99   make_cleanup (xfree, sai);
 100   i = 0;
 101   for (sec = nbfd->sections; sec != NULL; sec = sec->next)
 102     if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
 103       {
 104         sai->other[i].addr = bfd_get_section_vma (nbfd, sec) + loadbase;
 105         sai->other[i].name = (char *) bfd_get_section_name (nbfd, sec);
 106         sai->other[i].sectindex = sec->index;
 107         ++i;
 108       }
 109
 110   objf = symbol_file_add_from_bfd (nbfd, from_tty,
 111                                    sai, 0, OBJF_SHARED);
 112
 113   /* This might change our ideas about frames already looked at.  */
 114   reinit_frame_cache ();
 115
 116   return objf;
 117 }
 118
 119
 120 static void
 121 add_symbol_file_from_memory_command (char *args, int from_tty)
 122 {
 123   CORE_ADDR addr;
 124   struct bfd *templ;
 125
 126   if (args == NULL)
 127     error (_("add-symbol-file-from-memory requires an expression argument"));
 128
 129   addr = parse_and_eval_address (args);
 130
 131   /* We need some representative bfd to know the target we are looking at.  */
 132   if (symfile_objfile != NULL)
 133     templ = symfile_objfile->obfd;
 134   else
 135     templ = exec_bfd;
 136   if (templ == NULL)
 137     error (_("\
 138 Must use symbol-file or exec-file before add-symbol-file-from-memory."));
 139
 140   symbol_file_add_from_memory (templ, addr, NULL, from_tty);
 141 }
 142
 143 /* Arguments for symbol_file_add_from_memory_wrapper.  */
 144
 145 struct symbol_file_add_from_memory_args
 146 {
 147   struct bfd *bfd;
 148   CORE_ADDR sysinfo_ehdr;
 149   char *name;
 150   int from_tty;
 151 };
 152
 153 /* Wrapper function for symbol_file_add_from_memory, for
 154    catch_exceptions.  */
 155
 156 static int
 157 symbol_file_add_from_memory_wrapper (struct ui_out *uiout, void *data)
 158 {
 159   struct symbol_file_add_from_memory_args *args = data;
 160
 161   symbol_file_add_from_memory (args->bfd, args->sysinfo_ehdr, args->name,
 162                                args->from_tty);
 163   return 0;
 164 }
 165
 166 /* Try to add the symbols for the vsyscall page, if there is one.  This function
 167    is called via the inferior_created observer.  */
 168
 169 static void
 170 add_vsyscall_page (struct target_ops *target, int from_tty)
 171 {
 172   CORE_ADDR sysinfo_ehdr;
 173
 174   if (target_auxv_search (target, AT_SYSINFO_EHDR, &sysinfo_ehdr) > 0
 175       && sysinfo_ehdr != (CORE_ADDR) 0)
 176     {
 177       struct bfd *bfd;
 178       struct symbol_file_add_from_memory_args args;
 179
 180       if (core_bfd != NULL)
 181         bfd = core_bfd;
 182       else if (exec_bfd != NULL)
 183         bfd = exec_bfd;
 184       else
 185        /* FIXME: cagney/2004-05-06: Should not require an existing
 186           BFD when trying to create a run-time BFD of the VSYSCALL
 187           page in the inferior.  Unfortunately that's the current
 188           interface so for the moment bail.  Introducing a
 189           ``bfd_runtime'' (a BFD created using the loaded image) file
 190           format should fix this.  */
 191         {
 192           warning (_("\
 193 Could not load vsyscall page because no executable was specified\n\
 194 try using the \"file\" command first."));
 195           return;
 196         }
 197       args.bfd = bfd;
 198       args.sysinfo_ehdr = sysinfo_ehdr;
 199       args.name = xstrprintf ("system-supplied DSO at 0x%s",
 200                  paddr_nz (sysinfo_ehdr));
 201       /* Pass zero for FROM_TTY, because the action of loading the
 202          vsyscall DSO was not triggered by the user, even if the user
 203          typed "run" at the TTY.  */
 204       args.from_tty = 0;
 205       catch_exceptions (uiout, symbol_file_add_from_memory_wrapper,
 206                         &args, RETURN_MASK_ALL);
 207     }
 208 }
 209
 210 \f
 211
 212 /* Provide a prototype to silence -Wmissing-prototypes.  */
 213 extern initialize_file_ftype _initialize_symfile_mem;
 214
 215 void
 216 _initialize_symfile_mem (void)
 217 {
 218   add_cmd ("add-symbol-file-from-memory", class_files,
 219            add_symbol_file_from_memory_command, _("\
 220 Load the symbols out of memory from a dynamically loaded object file.\n\
 221 Give an expression for the address of the file's shared object file header."),
 222            &cmdlist);
 223
 224   /* Want to know of each new inferior so that its vsyscall info can
 225      be extracted.  */
 226   observer_attach_inferior_created (add_vsyscall_page);
 227 }