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
56
57/* Read inferior memory at ADDR to find the header of a loaded object file
58   and read its in-core symbols out of inferior memory.  TEMPL is a bfd
59   representing the target's format.  */
60static struct objfile *
61symbol_file_add_from_memory (struct bfd *templ, CORE_ADDR addr, int from_tty)
62{
63  struct objfile *objf;
64  struct bfd *nbfd;
65  struct bfd_section *sec;
66  bfd_vma loadbase;
67  struct section_addr_info *sai;
68  unsigned int i;
69
70  if (bfd_get_flavour (templ) != bfd_target_elf_flavour)
71    error ("add-symbol-file-from-memory not supported for this target");
72
73  nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, &loadbase,
74					 target_read_memory);
75  if (nbfd == NULL)
76    error ("Failed to read a valid object file image from memory.");
77
78  nbfd->filename = xstrdup ("shared object read from target memory");
79
80  if (!bfd_check_format (nbfd, bfd_object))
81    {
82      /* FIXME: should be checking for errors from bfd_close (for one thing,
83         on error it does not free all the storage associated with the
84         bfd).  */
85      bfd_close (nbfd);
86      error ("Got object file from memory but can't read symbols: %s.",
87	     bfd_errmsg (bfd_get_error ()));
88    }
89
90  sai = alloc_section_addr_info (bfd_count_sections (nbfd));
91  make_cleanup (xfree, sai);
92  i = 0;
93  for (sec = nbfd->sections; sec != NULL; sec = sec->next)
94    if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
95      {
96	sai->other[i].addr = bfd_get_section_vma (nbfd, sec) + loadbase;
97	sai->other[i].name = (char *) bfd_get_section_name (nbfd, sec);
98	sai->other[i].sectindex = sec->index;
99	++i;
100      }
101
102  objf = symbol_file_add_from_bfd (nbfd, from_tty,
103                                   sai, 0, OBJF_SHARED);
104
105  /* This might change our ideas about frames already looked at.  */
106  reinit_frame_cache ();
107
108  return objf;
109}
110
111
112static void
113add_symbol_file_from_memory_command (char *args, int from_tty)
114{
115  CORE_ADDR addr;
116  struct bfd *templ;
117
118  if (args == NULL)
119    error ("add-symbol-file-from-memory requires an expression argument");
120
121  addr = parse_and_eval_address (args);
122
123  /* We need some representative bfd to know the target we are looking at.  */
124  if (symfile_objfile != NULL)
125    templ = symfile_objfile->obfd;
126  else
127    templ = exec_bfd;
128  if (templ == NULL)
129    error ("\
130Must use symbol-file or exec-file before add-symbol-file-from-memory.");
131
132  symbol_file_add_from_memory (templ, addr, from_tty);
133}
134
135
136void
137_initialize_symfile_mem (void)
138{
139  add_cmd ("add-symbol-file-from-memory", class_files,
140           add_symbol_file_from_memory_command,
141           "\
142Load the symbols out of memory from a dynamically loaded object file.\n\
143Give an expression for the address of the file's shared object file header.",
144           &cmdlist);
145
146}
147