1 /* Reading symbol files from memory.
3 Copyright (C) 1986-1987, 1989, 1991, 1994-1996, 1998, 2000-2005,
4 2007-2012 Free Software Foundation, Inc.
6 This file is part of GDB.
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.
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.
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/>. */
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
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.
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.
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
49 #include "exceptions.h"
56 #include "elf/common.h"
58 /* Verify parameters of target_read_memory_bfd and target_read_memory are
61 gdb_static_assert (sizeof (CORE_ADDR) == sizeof (bfd_vma));
62 gdb_static_assert (sizeof (gdb_byte) == sizeof (bfd_byte));
63 gdb_static_assert (sizeof (size_t) <= sizeof (bfd_size_type));
65 /* Provide bfd/ compatible prototype for target_read_memory. Casting would not
66 be enough as LEN width may differ. */
69 target_read_memory_bfd (bfd_vma memaddr, bfd_byte *myaddr, bfd_size_type len)
71 /* MYADDR must be already allocated for the LEN size so it has to fit in
73 gdb_assert ((size_t) len == len);
75 return target_read_memory (memaddr, myaddr, len);
78 /* Read inferior memory at ADDR to find the header of a loaded object file
79 and read its in-core symbols out of inferior memory. TEMPL is a bfd
80 representing the target's format. NAME is the name to use for this
81 symbol file in messages; it can be NULL or a malloc-allocated string
82 which will be attached to the BFD. */
83 static struct objfile *
84 symbol_file_add_from_memory (struct bfd *templ, CORE_ADDR addr, char *name,
89 struct bfd_section *sec;
91 struct section_addr_info *sai;
93 struct cleanup *cleanup;
95 if (bfd_get_flavour (templ) != bfd_target_elf_flavour)
96 error (_("add-symbol-file-from-memory not supported for this target"));
98 nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, &loadbase,
99 target_read_memory_bfd);
101 error (_("Failed to read a valid object file image from memory."));
104 nbfd->filename = xstrdup ("shared object read from target memory");
106 nbfd->filename = name;
108 if (!bfd_check_format (nbfd, bfd_object))
110 /* FIXME: should be checking for errors from bfd_close (for one thing,
111 on error it does not free all the storage associated with the
114 error (_("Got object file from memory but can't read symbols: %s."),
115 bfd_errmsg (bfd_get_error ()));
118 sai = alloc_section_addr_info (bfd_count_sections (nbfd));
119 cleanup = make_cleanup (xfree, sai);
121 for (sec = nbfd->sections; sec != NULL; sec = sec->next)
122 if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
124 sai->other[i].addr = bfd_get_section_vma (nbfd, sec) + loadbase;
125 sai->other[i].name = (char *) bfd_get_section_name (nbfd, sec);
126 sai->other[i].sectindex = sec->index;
130 objf = symbol_file_add_from_bfd (nbfd, from_tty ? SYMFILE_VERBOSE : 0,
131 sai, OBJF_SHARED, NULL);
133 /* This might change our ideas about frames already looked at. */
134 reinit_frame_cache ();
136 do_cleanups (cleanup);
142 add_symbol_file_from_memory_command (char *args, int from_tty)
148 error (_("add-symbol-file-from-memory requires an expression argument"));
150 addr = parse_and_eval_address (args);
152 /* We need some representative bfd to know the target we are looking at. */
153 if (symfile_objfile != NULL)
154 templ = symfile_objfile->obfd;
158 error (_("Must use symbol-file or exec-file "
159 "before add-symbol-file-from-memory."));
161 symbol_file_add_from_memory (templ, addr, NULL, from_tty);
164 /* Arguments for symbol_file_add_from_memory_wrapper. */
166 struct symbol_file_add_from_memory_args
169 CORE_ADDR sysinfo_ehdr;
174 /* Wrapper function for symbol_file_add_from_memory, for
178 symbol_file_add_from_memory_wrapper (struct ui_out *uiout, void *data)
180 struct symbol_file_add_from_memory_args *args = data;
182 symbol_file_add_from_memory (args->bfd, args->sysinfo_ehdr, args->name,
187 /* Try to add the symbols for the vsyscall page, if there is one.
188 This function is called via the inferior_created observer. */
191 add_vsyscall_page (struct target_ops *target, int from_tty)
193 CORE_ADDR sysinfo_ehdr;
195 if (target_auxv_search (target, AT_SYSINFO_EHDR, &sysinfo_ehdr) > 0
196 && sysinfo_ehdr != (CORE_ADDR) 0)
199 struct symbol_file_add_from_memory_args args;
201 if (core_bfd != NULL)
203 else if (exec_bfd != NULL)
206 /* FIXME: cagney/2004-05-06: Should not require an existing
207 BFD when trying to create a run-time BFD of the VSYSCALL
208 page in the inferior. Unfortunately that's the current
209 interface so for the moment bail. Introducing a
210 ``bfd_runtime'' (a BFD created using the loaded image) file
211 format should fix this. */
213 warning (_("Could not load vsyscall page "
214 "because no executable was specified\n"
215 "try using the \"file\" command first."));
219 args.sysinfo_ehdr = sysinfo_ehdr;
220 args.name = xstrprintf ("system-supplied DSO at %s",
221 paddress (target_gdbarch, sysinfo_ehdr));
222 /* Pass zero for FROM_TTY, because the action of loading the
223 vsyscall DSO was not triggered by the user, even if the user
224 typed "run" at the TTY. */
226 catch_exceptions (current_uiout, symbol_file_add_from_memory_wrapper,
227 &args, RETURN_MASK_ALL);
233 /* Provide a prototype to silence -Wmissing-prototypes. */
234 extern initialize_file_ftype _initialize_symfile_mem;
237 _initialize_symfile_mem (void)
239 add_cmd ("add-symbol-file-from-memory", class_files,
240 add_symbol_file_from_memory_command,
241 _("Load the symbols out of memory from a "
242 "dynamically loaded object file.\n"
243 "Give an expression for the address "
244 "of the file's shared object file header."),
247 /* Want to know of each new inferior so that its vsyscall info can
249 observer_attach_inferior_created (add_vsyscall_page);