1 /* Reading symbol files from memory. 2 3 Copyright (C) 1986-2014 Free Software Foundation, Inc. 4 5 This file is part of GDB. 6 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. 11 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. 16 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/>. */ 19 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 25 system calls. 26 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. 32 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. 37 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 41 entry point. */ 42 43 44 #include "defs.h" 45 #include "symtab.h" 46 #include "gdbcore.h" 47 #include "objfiles.h" 48 #include "exceptions.h" 49 #include "gdbcmd.h" 50 #include "target.h" 51 #include "value.h" 52 #include "symfile.h" 53 #include "observer.h" 54 #include "auxv.h" 55 #include "elf/common.h" 56 #include "gdb_bfd.h" 57 58 /* Verify parameters of target_read_memory_bfd and target_read_memory are 59 compatible. */ 60 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)); 64 65 /* Provide bfd/ compatible prototype for target_read_memory. Casting would not 66 be enough as LEN width may differ. */ 67 68 static int 69 target_read_memory_bfd (bfd_vma memaddr, bfd_byte *myaddr, bfd_size_type len) 70 { 71 /* MYADDR must be already allocated for the LEN size so it has to fit in 72 ssize_t. */ 73 gdb_assert ((ssize_t) len == len); 74 75 return target_read_memory (memaddr, myaddr, len); 76 } 77 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, 85 int from_tty) 86 { 87 struct objfile *objf; 88 struct bfd *nbfd; 89 struct bfd_section *sec; 90 bfd_vma loadbase; 91 struct section_addr_info *sai; 92 unsigned int i; 93 struct cleanup *cleanup; 94 95 if (bfd_get_flavour (templ) != bfd_target_elf_flavour) 96 error (_("add-symbol-file-from-memory not supported for this target")); 97 98 nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, &loadbase, 99 target_read_memory_bfd); 100 if (nbfd == NULL) 101 error (_("Failed to read a valid object file image from memory.")); 102 103 gdb_bfd_ref (nbfd); 104 xfree (bfd_get_filename (nbfd)); 105 if (name == NULL) 106 nbfd->filename = xstrdup ("shared object read from target memory"); 107 else 108 nbfd->filename = name; 109 110 cleanup = make_cleanup_bfd_unref (nbfd); 111 112 if (!bfd_check_format (nbfd, bfd_object)) 113 error (_("Got object file from memory but can't read symbols: %s."), 114 bfd_errmsg (bfd_get_error ())); 115 116 sai = alloc_section_addr_info (bfd_count_sections (nbfd)); 117 make_cleanup (xfree, sai); 118 i = 0; 119 for (sec = nbfd->sections; sec != NULL; sec = sec->next) 120 if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0) 121 { 122 sai->other[i].addr = bfd_get_section_vma (nbfd, sec) + loadbase; 123 sai->other[i].name = (char *) bfd_get_section_name (nbfd, sec); 124 sai->other[i].sectindex = sec->index; 125 ++i; 126 } 127 sai->num_sections = i; 128 129 objf = symbol_file_add_from_bfd (nbfd, bfd_get_filename (nbfd), 130 from_tty ? SYMFILE_VERBOSE : 0, 131 sai, OBJF_SHARED, NULL); 132 133 /* This might change our ideas about frames already looked at. */ 134 reinit_frame_cache (); 135 136 do_cleanups (cleanup); 137 return objf; 138 } 139 140 141 static void 142 add_symbol_file_from_memory_command (char *args, int from_tty) 143 { 144 CORE_ADDR addr; 145 struct bfd *templ; 146 147 if (args == NULL) 148 error (_("add-symbol-file-from-memory requires an expression argument")); 149 150 addr = parse_and_eval_address (args); 151 152 /* We need some representative bfd to know the target we are looking at. */ 153 if (symfile_objfile != NULL) 154 templ = symfile_objfile->obfd; 155 else 156 templ = exec_bfd; 157 if (templ == NULL) 158 error (_("Must use symbol-file or exec-file " 159 "before add-symbol-file-from-memory.")); 160 161 symbol_file_add_from_memory (templ, addr, NULL, from_tty); 162 } 163 164 /* Arguments for symbol_file_add_from_memory_wrapper. */ 165 166 struct symbol_file_add_from_memory_args 167 { 168 struct bfd *bfd; 169 CORE_ADDR sysinfo_ehdr; 170 char *name; 171 int from_tty; 172 }; 173 174 /* Wrapper function for symbol_file_add_from_memory, for 175 catch_exceptions. */ 176 177 static int 178 symbol_file_add_from_memory_wrapper (struct ui_out *uiout, void *data) 179 { 180 struct symbol_file_add_from_memory_args *args = data; 181 182 symbol_file_add_from_memory (args->bfd, args->sysinfo_ehdr, args->name, 183 args->from_tty); 184 return 0; 185 } 186 187 /* Try to add the symbols for the vsyscall page, if there is one. 188 This function is called via the inferior_created observer. */ 189 190 static void 191 add_vsyscall_page (struct target_ops *target, int from_tty) 192 { 193 CORE_ADDR sysinfo_ehdr; 194 195 if (target_auxv_search (target, AT_SYSINFO_EHDR, &sysinfo_ehdr) > 0 196 && sysinfo_ehdr != (CORE_ADDR) 0) 197 { 198 struct bfd *bfd; 199 struct symbol_file_add_from_memory_args args; 200 201 if (core_bfd != NULL) 202 bfd = core_bfd; 203 else if (exec_bfd != NULL) 204 bfd = exec_bfd; 205 else 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. */ 212 { 213 warning (_("Could not load vsyscall page " 214 "because no executable was specified\n" 215 "try using the \"file\" command first.")); 216 return; 217 } 218 args.bfd = bfd; 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. */ 225 args.from_tty = 0; 226 catch_exceptions (current_uiout, symbol_file_add_from_memory_wrapper, 227 &args, RETURN_MASK_ALL); 228 } 229 } 230 231 232 233 /* Provide a prototype to silence -Wmissing-prototypes. */ 234 extern initialize_file_ftype _initialize_symfile_mem; 235 236 void 237 _initialize_symfile_mem (void) 238 { 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."), 245 &cmdlist); 246 247 /* Want to know of each new inferior so that its vsyscall info can 248 be extracted. */ 249 observer_attach_inferior_created (add_vsyscall_page); 250 } 251