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"
59 /* Verify parameters of target_read_memory_bfd and target_read_memory are
62 gdb_static_assert (sizeof (CORE_ADDR) == sizeof (bfd_vma));
63 gdb_static_assert (sizeof (gdb_byte) == sizeof (bfd_byte));
64 gdb_static_assert (sizeof (ssize_t) <= sizeof (bfd_size_type));
66 /* Provide bfd/ compatible prototype for target_read_memory. Casting would not
67 be enough as LEN width may differ. */
70 target_read_memory_bfd (bfd_vma memaddr, bfd_byte *myaddr, bfd_size_type len)
72 /* MYADDR must be already allocated for the LEN size so it has to fit in
74 gdb_assert ((ssize_t) len == len);
76 return target_read_memory (memaddr, myaddr, len);
79 /* Read inferior memory at ADDR to find the header of a loaded object file
80 and read its in-core symbols out of inferior memory. TEMPL is a bfd
81 representing the target's format. NAME is the name to use for this
82 symbol file in messages; it can be NULL or a malloc-allocated string
83 which will be attached to the BFD. */
84 static struct objfile *
85 symbol_file_add_from_memory (struct bfd *templ, CORE_ADDR addr, char *name,
90 struct bfd_section *sec;
92 struct section_addr_info *sai;
94 struct cleanup *cleanup;
96 if (bfd_get_flavour (templ) != bfd_target_elf_flavour)
97 error (_("add-symbol-file-from-memory not supported for this target"));
99 nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, &loadbase,
100 target_read_memory_bfd);
102 error (_("Failed to read a valid object file image from memory."));
106 nbfd->filename = xstrdup ("shared object read from target memory");
108 nbfd->filename = name;
110 if (!bfd_check_format (nbfd, bfd_object))
112 make_cleanup_bfd_close (nbfd);
113 error (_("Got object file from memory but can't read symbols: %s."),
114 bfd_errmsg (bfd_get_error ()));
117 sai = alloc_section_addr_info (bfd_count_sections (nbfd));
118 cleanup = make_cleanup (xfree, sai);
120 for (sec = nbfd->sections; sec != NULL; sec = sec->next)
121 if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
123 sai->other[i].addr = bfd_get_section_vma (nbfd, sec) + loadbase;
124 sai->other[i].name = (char *) bfd_get_section_name (nbfd, sec);
125 sai->other[i].sectindex = sec->index;
129 objf = symbol_file_add_from_bfd (nbfd, from_tty ? SYMFILE_VERBOSE : 0,
130 sai, OBJF_SHARED, NULL);
132 /* This might change our ideas about frames already looked at. */
133 reinit_frame_cache ();
135 do_cleanups (cleanup);
141 add_symbol_file_from_memory_command (char *args, int from_tty)
147 error (_("add-symbol-file-from-memory requires an expression argument"));
149 addr = parse_and_eval_address (args);
151 /* We need some representative bfd to know the target we are looking at. */
152 if (symfile_objfile != NULL)
153 templ = symfile_objfile->obfd;
157 error (_("Must use symbol-file or exec-file "
158 "before add-symbol-file-from-memory."));
160 symbol_file_add_from_memory (templ, addr, NULL, from_tty);
163 /* Arguments for symbol_file_add_from_memory_wrapper. */
165 struct symbol_file_add_from_memory_args
168 CORE_ADDR sysinfo_ehdr;
173 /* Wrapper function for symbol_file_add_from_memory, for
177 symbol_file_add_from_memory_wrapper (struct ui_out *uiout, void *data)
179 struct symbol_file_add_from_memory_args *args = data;
181 symbol_file_add_from_memory (args->bfd, args->sysinfo_ehdr, args->name,
186 /* Try to add the symbols for the vsyscall page, if there is one.
187 This function is called via the inferior_created observer. */
190 add_vsyscall_page (struct target_ops *target, int from_tty)
192 CORE_ADDR sysinfo_ehdr;
194 if (target_auxv_search (target, AT_SYSINFO_EHDR, &sysinfo_ehdr) > 0
195 && sysinfo_ehdr != (CORE_ADDR) 0)
198 struct symbol_file_add_from_memory_args args;
200 if (core_bfd != NULL)
202 else if (exec_bfd != NULL)
205 /* FIXME: cagney/2004-05-06: Should not require an existing
206 BFD when trying to create a run-time BFD of the VSYSCALL
207 page in the inferior. Unfortunately that's the current
208 interface so for the moment bail. Introducing a
209 ``bfd_runtime'' (a BFD created using the loaded image) file
210 format should fix this. */
212 warning (_("Could not load vsyscall page "
213 "because no executable was specified\n"
214 "try using the \"file\" command first."));
218 args.sysinfo_ehdr = sysinfo_ehdr;
219 args.name = xstrprintf ("system-supplied DSO at %s",
220 paddress (target_gdbarch, sysinfo_ehdr));
221 /* Pass zero for FROM_TTY, because the action of loading the
222 vsyscall DSO was not triggered by the user, even if the user
223 typed "run" at the TTY. */
225 catch_exceptions (current_uiout, symbol_file_add_from_memory_wrapper,
226 &args, RETURN_MASK_ALL);
232 /* Provide a prototype to silence -Wmissing-prototypes. */
233 extern initialize_file_ftype _initialize_symfile_mem;
236 _initialize_symfile_mem (void)
238 add_cmd ("add-symbol-file-from-memory", class_files,
239 add_symbol_file_from_memory_command,
240 _("Load the symbols out of memory from a "
241 "dynamically loaded object file.\n"
242 "Give an expression for the address "
243 "of the file's shared object file header."),
246 /* Want to know of each new inferior so that its vsyscall info can
248 observer_attach_inferior_created (add_vsyscall_page);