1 /* Reading symbol files from memory.
3 Copyright (C) 1986-2014 Free Software Foundation, Inc.
5 This file is part of GDB.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>. */
20 /* This file defines functions (and commands to exercise those
21 functions) for reading debugging information from object files
22 whose images are mapped directly into the inferior's memory. For
23 example, the Linux kernel maps a "syscall DSO" into each process's
24 address space; this DSO provides kernel-specific code for some
27 At the moment, BFD only has functions for parsing object files from
28 memory for the ELF format, even though the general idea isn't
29 ELF-specific. This means that BFD only provides the functions GDB
30 needs when configured for ELF-based targets. So these functions
31 may only be compiled on ELF-based targets.
33 GDB has no idea whether it has been configured for an ELF-based
34 target or not: it just tries to handle whatever files it is given.
35 But this means there are no preprocessor symbols on which we could
36 make these functions' compilation conditional.
38 So, for the time being, we put these functions alone in this file,
39 and have .mt files reference them as appropriate. In the future, I
40 hope BFD will provide a format-independent bfd_from_remote_memory
48 #include "exceptions.h"
55 #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 (ssize_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 ((ssize_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. SIZE, if
80 non-zero, is the known size of the object. 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,
86 size_t size, char *name, int from_tty)
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, size, &loadbase,
100 target_read_memory_bfd);
102 error (_("Failed to read a valid object file image from memory."));
105 xfree (bfd_get_filename (nbfd));
107 nbfd->filename = xstrdup ("shared object read from target memory");
109 nbfd->filename = name;
111 cleanup = make_cleanup_bfd_unref (nbfd);
113 if (!bfd_check_format (nbfd, bfd_object))
114 error (_("Got object file from memory but can't read symbols: %s."),
115 bfd_errmsg (bfd_get_error ()));
117 sai = alloc_section_addr_info (bfd_count_sections (nbfd));
118 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;
128 sai->num_sections = i;
130 objf = symbol_file_add_from_bfd (nbfd, bfd_get_filename (nbfd),
131 from_tty ? SYMFILE_VERBOSE : 0,
132 sai, OBJF_SHARED, NULL);
134 add_target_sections_of_objfile (objf);
136 /* This might change our ideas about frames already looked at. */
137 reinit_frame_cache ();
139 do_cleanups (cleanup);
145 add_symbol_file_from_memory_command (char *args, int from_tty)
151 error (_("add-symbol-file-from-memory requires an expression argument"));
153 addr = parse_and_eval_address (args);
155 /* We need some representative bfd to know the target we are looking at. */
156 if (symfile_objfile != NULL)
157 templ = symfile_objfile->obfd;
161 error (_("Must use symbol-file or exec-file "
162 "before add-symbol-file-from-memory."));
164 symbol_file_add_from_memory (templ, addr, 0, NULL, from_tty);
167 /* Arguments for symbol_file_add_from_memory_wrapper. */
169 struct symbol_file_add_from_memory_args
172 CORE_ADDR sysinfo_ehdr;
178 /* Wrapper function for symbol_file_add_from_memory, for
182 symbol_file_add_from_memory_wrapper (struct ui_out *uiout, void *data)
184 struct symbol_file_add_from_memory_args *args = data;
186 symbol_file_add_from_memory (args->bfd, args->sysinfo_ehdr, args->size,
187 args->name, args->from_tty);
191 /* Rummage through mappings to find the vsyscall page size. */
194 find_vdso_size (CORE_ADDR vaddr, unsigned long size,
195 int read, int write, int exec, int modified,
198 struct symbol_file_add_from_memory_args *args = data;
200 if (vaddr == args->sysinfo_ehdr)
208 /* Try to add the symbols for the vsyscall page, if there is one.
209 This function is called via the inferior_created observer. */
212 add_vsyscall_page (struct target_ops *target, int from_tty)
214 CORE_ADDR sysinfo_ehdr;
216 if (target_auxv_search (target, AT_SYSINFO_EHDR, &sysinfo_ehdr) > 0
217 && sysinfo_ehdr != (CORE_ADDR) 0)
220 struct symbol_file_add_from_memory_args args;
222 if (core_bfd != NULL)
224 else if (exec_bfd != NULL)
227 /* FIXME: cagney/2004-05-06: Should not require an existing
228 BFD when trying to create a run-time BFD of the VSYSCALL
229 page in the inferior. Unfortunately that's the current
230 interface so for the moment bail. Introducing a
231 ``bfd_runtime'' (a BFD created using the loaded image) file
232 format should fix this. */
234 warning (_("Could not load vsyscall page "
235 "because no executable was specified\n"
236 "try using the \"file\" command first."));
240 args.sysinfo_ehdr = sysinfo_ehdr;
242 if (gdbarch_find_memory_regions_p (target_gdbarch ()))
243 (void) gdbarch_find_memory_regions (target_gdbarch (),
244 find_vdso_size, &args);
246 args.name = xstrprintf ("system-supplied DSO at %s",
247 paddress (target_gdbarch (), sysinfo_ehdr));
248 /* Pass zero for FROM_TTY, because the action of loading the
249 vsyscall DSO was not triggered by the user, even if the user
250 typed "run" at the TTY. */
252 catch_exceptions (current_uiout, symbol_file_add_from_memory_wrapper,
253 &args, RETURN_MASK_ALL);
259 /* Provide a prototype to silence -Wmissing-prototypes. */
260 extern initialize_file_ftype _initialize_symfile_mem;
263 _initialize_symfile_mem (void)
265 add_cmd ("add-symbol-file-from-memory", class_files,
266 add_symbol_file_from_memory_command,
267 _("Load the symbols out of memory from a "
268 "dynamically loaded object file.\n"
269 "Give an expression for the address "
270 "of the file's shared object file header."),
273 /* Want to know of each new inferior so that its vsyscall info can
275 observer_attach_inferior_created (add_vsyscall_page);