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;
95 struct target_section *sections, *sections_end, *tsec;
97 if (bfd_get_flavour (templ) != bfd_target_elf_flavour)
98 error (_("add-symbol-file-from-memory not supported for this target"));
100 nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, size, &loadbase,
101 target_read_memory_bfd);
103 error (_("Failed to read a valid object file image from memory."));
106 xfree (bfd_get_filename (nbfd));
108 nbfd->filename = xstrdup ("shared object read from target memory");
110 nbfd->filename = name;
112 cleanup = make_cleanup_bfd_unref (nbfd);
114 if (!bfd_check_format (nbfd, bfd_object))
115 error (_("Got object file from memory but can't read symbols: %s."),
116 bfd_errmsg (bfd_get_error ()));
118 sai = alloc_section_addr_info (bfd_count_sections (nbfd));
119 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;
129 sai->num_sections = i;
131 objf = symbol_file_add_from_bfd (nbfd, bfd_get_filename (nbfd),
132 from_tty ? SYMFILE_VERBOSE : 0,
133 sai, OBJF_SHARED, NULL);
138 if (build_section_table (nbfd, §ions, §ions_end) == 0)
140 make_cleanup (xfree, sections);
142 /* Adjust the target section addresses by the load address. */
143 for (tsec = sections; tsec != sections_end; ++tsec)
145 tsec->addr += loadbase;
146 tsec->endaddr += loadbase;
149 add_target_sections (&nbfd, sections, sections_end);
152 /* This might change our ideas about frames already looked at. */
153 reinit_frame_cache ();
155 do_cleanups (cleanup);
161 add_symbol_file_from_memory_command (char *args, int from_tty)
167 error (_("add-symbol-file-from-memory requires an expression argument"));
169 addr = parse_and_eval_address (args);
171 /* We need some representative bfd to know the target we are looking at. */
172 if (symfile_objfile != NULL)
173 templ = symfile_objfile->obfd;
177 error (_("Must use symbol-file or exec-file "
178 "before add-symbol-file-from-memory."));
180 symbol_file_add_from_memory (templ, addr, 0, NULL, from_tty);
183 /* Arguments for symbol_file_add_from_memory_wrapper. */
185 struct symbol_file_add_from_memory_args
188 CORE_ADDR sysinfo_ehdr;
194 /* Wrapper function for symbol_file_add_from_memory, for
198 symbol_file_add_from_memory_wrapper (struct ui_out *uiout, void *data)
200 struct symbol_file_add_from_memory_args *args = data;
202 symbol_file_add_from_memory (args->bfd, args->sysinfo_ehdr, args->size,
203 args->name, args->from_tty);
207 /* Rummage through mappings to find the vsyscall page size. */
210 find_vdso_size (CORE_ADDR vaddr, unsigned long size,
211 int read, int write, int exec, int modified,
214 struct symbol_file_add_from_memory_args *args = data;
216 if (vaddr == args->sysinfo_ehdr)
224 /* Try to add the symbols for the vsyscall page, if there is one.
225 This function is called via the inferior_created observer. */
228 add_vsyscall_page (struct target_ops *target, int from_tty)
230 CORE_ADDR sysinfo_ehdr;
232 if (target_auxv_search (target, AT_SYSINFO_EHDR, &sysinfo_ehdr) > 0
233 && sysinfo_ehdr != (CORE_ADDR) 0)
236 struct symbol_file_add_from_memory_args args;
238 if (core_bfd != NULL)
240 else if (exec_bfd != NULL)
243 /* FIXME: cagney/2004-05-06: Should not require an existing
244 BFD when trying to create a run-time BFD of the VSYSCALL
245 page in the inferior. Unfortunately that's the current
246 interface so for the moment bail. Introducing a
247 ``bfd_runtime'' (a BFD created using the loaded image) file
248 format should fix this. */
250 warning (_("Could not load vsyscall page "
251 "because no executable was specified\n"
252 "try using the \"file\" command first."));
256 args.sysinfo_ehdr = sysinfo_ehdr;
258 if (gdbarch_find_memory_regions_p (target_gdbarch ()))
259 (void) gdbarch_find_memory_regions (target_gdbarch (),
260 find_vdso_size, &args);
262 args.name = xstrprintf ("system-supplied DSO at %s",
263 paddress (target_gdbarch (), sysinfo_ehdr));
264 /* Pass zero for FROM_TTY, because the action of loading the
265 vsyscall DSO was not triggered by the user, even if the user
266 typed "run" at the TTY. */
268 catch_exceptions (current_uiout, symbol_file_add_from_memory_wrapper,
269 &args, RETURN_MASK_ALL);
275 /* Provide a prototype to silence -Wmissing-prototypes. */
276 extern initialize_file_ftype _initialize_symfile_mem;
279 _initialize_symfile_mem (void)
281 add_cmd ("add-symbol-file-from-memory", class_files,
282 add_symbol_file_from_memory_command,
283 _("Load the symbols out of memory from a "
284 "dynamically loaded object file.\n"
285 "Give an expression for the address "
286 "of the file's shared object file header."),
289 /* Want to know of each new inferior so that its vsyscall info can
291 observer_attach_inferior_created (add_vsyscall_page);