1 /* Reading symbol files from memory. 2 3 Copyright (C) 1986-2016 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 "gdbcmd.h" 49 #include "target.h" 50 #include "value.h" 51 #include "symfile.h" 52 #include "observer.h" 53 #include "auxv.h" 54 #include "elf/common.h" 55 #include "gdb_bfd.h" 56 57 /* Verify parameters of target_read_memory_bfd and target_read_memory are 58 compatible. */ 59 60 gdb_static_assert (sizeof (CORE_ADDR) == sizeof (bfd_vma)); 61 gdb_static_assert (sizeof (gdb_byte) == sizeof (bfd_byte)); 62 gdb_static_assert (sizeof (ssize_t) <= sizeof (bfd_size_type)); 63 64 /* Provide bfd/ compatible prototype for target_read_memory. Casting would not 65 be enough as LEN width may differ. */ 66 67 static int 68 target_read_memory_bfd (bfd_vma memaddr, bfd_byte *myaddr, bfd_size_type len) 69 { 70 /* MYADDR must be already allocated for the LEN size so it has to fit in 71 ssize_t. */ 72 gdb_assert ((ssize_t) len == len); 73 74 return target_read_memory (memaddr, myaddr, len); 75 } 76 77 /* Read inferior memory at ADDR to find the header of a loaded object file 78 and read its in-core symbols out of inferior memory. SIZE, if 79 non-zero, is the known size of the object. 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, 85 size_t size, char *name, 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, size, &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 add_target_sections_of_objfile (objf); 134 135 /* This might change our ideas about frames already looked at. */ 136 reinit_frame_cache (); 137 138 do_cleanups (cleanup); 139 return objf; 140 } 141 142 143 static void 144 add_symbol_file_from_memory_command (char *args, int from_tty) 145 { 146 CORE_ADDR addr; 147 struct bfd *templ; 148 149 if (args == NULL) 150 error (_("add-symbol-file-from-memory requires an expression argument")); 151 152 addr = parse_and_eval_address (args); 153 154 /* We need some representative bfd to know the target we are looking at. */ 155 if (symfile_objfile != NULL) 156 templ = symfile_objfile->obfd; 157 else 158 templ = exec_bfd; 159 if (templ == NULL) 160 error (_("Must use symbol-file or exec-file " 161 "before add-symbol-file-from-memory.")); 162 163 symbol_file_add_from_memory (templ, addr, 0, NULL, from_tty); 164 } 165 166 /* Arguments for symbol_file_add_from_memory_wrapper. */ 167 168 struct symbol_file_add_from_memory_args 169 { 170 struct bfd *bfd; 171 CORE_ADDR sysinfo_ehdr; 172 size_t size; 173 char *name; 174 int from_tty; 175 }; 176 177 /* Wrapper function for symbol_file_add_from_memory, for 178 catch_exceptions. */ 179 180 static int 181 symbol_file_add_from_memory_wrapper (struct ui_out *uiout, void *data) 182 { 183 struct symbol_file_add_from_memory_args *args 184 = (struct symbol_file_add_from_memory_args *) data; 185 186 symbol_file_add_from_memory (args->bfd, args->sysinfo_ehdr, args->size, 187 args->name, args->from_tty); 188 return 0; 189 } 190 191 /* Try to add the symbols for the vsyscall page, if there is one. 192 This function is called via the inferior_created observer. */ 193 194 static void 195 add_vsyscall_page (struct target_ops *target, int from_tty) 196 { 197 struct mem_range vsyscall_range; 198 199 if (gdbarch_vsyscall_range (target_gdbarch (), &vsyscall_range)) 200 { 201 struct bfd *bfd; 202 struct symbol_file_add_from_memory_args args; 203 204 if (core_bfd != NULL) 205 bfd = core_bfd; 206 else if (exec_bfd != NULL) 207 bfd = exec_bfd; 208 else 209 /* FIXME: cagney/2004-05-06: Should not require an existing 210 BFD when trying to create a run-time BFD of the VSYSCALL 211 page in the inferior. Unfortunately that's the current 212 interface so for the moment bail. Introducing a 213 ``bfd_runtime'' (a BFD created using the loaded image) file 214 format should fix this. */ 215 { 216 warning (_("Could not load vsyscall page " 217 "because no executable was specified")); 218 return; 219 } 220 args.bfd = bfd; 221 args.sysinfo_ehdr = vsyscall_range.start; 222 args.size = vsyscall_range.length; 223 224 args.name = xstrprintf ("system-supplied DSO at %s", 225 paddress (target_gdbarch (), vsyscall_range.start)); 226 /* Pass zero for FROM_TTY, because the action of loading the 227 vsyscall DSO was not triggered by the user, even if the user 228 typed "run" at the TTY. */ 229 args.from_tty = 0; 230 catch_exceptions (current_uiout, symbol_file_add_from_memory_wrapper, 231 &args, RETURN_MASK_ALL); 232 } 233 } 234 235 236 237 /* Provide a prototype to silence -Wmissing-prototypes. */ 238 extern initialize_file_ftype _initialize_symfile_mem; 239 240 void 241 _initialize_symfile_mem (void) 242 { 243 add_cmd ("add-symbol-file-from-memory", class_files, 244 add_symbol_file_from_memory_command, 245 _("Load the symbols out of memory from a " 246 "dynamically loaded object file.\n" 247 "Give an expression for the address " 248 "of the file's shared object file header."), 249 &cmdlist); 250 251 /* Want to know of each new inferior so that its vsyscall info can 252 be extracted. */ 253 observer_attach_inferior_created (add_vsyscall_page); 254 } 255