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 = "shared object read from target memory";
109 nbfd->filename = name;
110 gdb_bfd_stash_filename (nbfd);
114 cleanup = make_cleanup_bfd_unref (nbfd);
116 if (!bfd_check_format (nbfd, bfd_object))
117 error (_("Got object file from memory but can't read symbols: %s."),
118 bfd_errmsg (bfd_get_error ()));
120 sai = alloc_section_addr_info (bfd_count_sections (nbfd));
121 make_cleanup (xfree, sai);
123 for (sec = nbfd->sections; sec != NULL; sec = sec->next)
124 if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
126 sai->other[i].addr = bfd_get_section_vma (nbfd, sec) + loadbase;
127 sai->other[i].name = (char *) bfd_get_section_name (nbfd, sec);
128 sai->other[i].sectindex = sec->index;
132 objf = symbol_file_add_from_bfd (nbfd, from_tty ? SYMFILE_VERBOSE : 0,
133 sai, OBJF_SHARED, NULL);
135 /* This might change our ideas about frames already looked at. */
136 reinit_frame_cache ();
138 do_cleanups (cleanup);
144 add_symbol_file_from_memory_command (char *args, int from_tty)
150 error (_("add-symbol-file-from-memory requires an expression argument"));
152 addr = parse_and_eval_address (args);
154 /* We need some representative bfd to know the target we are looking at. */
155 if (symfile_objfile != NULL)
156 templ = symfile_objfile->obfd;
160 error (_("Must use symbol-file or exec-file "
161 "before add-symbol-file-from-memory."));
163 symbol_file_add_from_memory (templ, addr, NULL, from_tty);
166 /* Arguments for symbol_file_add_from_memory_wrapper. */
168 struct symbol_file_add_from_memory_args
171 CORE_ADDR sysinfo_ehdr;
176 /* Wrapper function for symbol_file_add_from_memory, for
180 symbol_file_add_from_memory_wrapper (struct ui_out *uiout, void *data)
182 struct symbol_file_add_from_memory_args *args = data;
184 symbol_file_add_from_memory (args->bfd, args->sysinfo_ehdr, args->name,
189 /* Try to add the symbols for the vsyscall page, if there is one.
190 This function is called via the inferior_created observer. */
193 add_vsyscall_page (struct target_ops *target, int from_tty)
195 CORE_ADDR sysinfo_ehdr;
197 if (target_auxv_search (target, AT_SYSINFO_EHDR, &sysinfo_ehdr) > 0
198 && sysinfo_ehdr != (CORE_ADDR) 0)
201 struct symbol_file_add_from_memory_args args;
203 if (core_bfd != NULL)
205 else if (exec_bfd != NULL)
208 /* FIXME: cagney/2004-05-06: Should not require an existing
209 BFD when trying to create a run-time BFD of the VSYSCALL
210 page in the inferior. Unfortunately that's the current
211 interface so for the moment bail. Introducing a
212 ``bfd_runtime'' (a BFD created using the loaded image) file
213 format should fix this. */
215 warning (_("Could not load vsyscall page "
216 "because no executable was specified\n"
217 "try using the \"file\" command first."));
221 args.sysinfo_ehdr = sysinfo_ehdr;
222 args.name = xstrprintf ("system-supplied DSO at %s",
223 paddress (target_gdbarch, sysinfo_ehdr));
224 /* Pass zero for FROM_TTY, because the action of loading the
225 vsyscall DSO was not triggered by the user, even if the user
226 typed "run" at the TTY. */
228 catch_exceptions (current_uiout, symbol_file_add_from_memory_wrapper,
229 &args, RETURN_MASK_ALL);
235 /* Provide a prototype to silence -Wmissing-prototypes. */
236 extern initialize_file_ftype _initialize_symfile_mem;
239 _initialize_symfile_mem (void)
241 add_cmd ("add-symbol-file-from-memory", class_files,
242 add_symbol_file_from_memory_command,
243 _("Load the symbols out of memory from a "
244 "dynamically loaded object file.\n"
245 "Give an expression for the address "
246 "of the file's shared object file header."),
249 /* Want to know of each new inferior so that its vsyscall info can
251 observer_attach_inferior_created (add_vsyscall_page);