1/* Reading symbol files from memory. 2 3 Copyright (C) 1986, 1987, 1989, 1991, 1994, 1995, 1996, 1998, 2000, 2001, 4 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010, 2011 5 Free Software Foundation, Inc. 6 7 This file is part of GDB. 8 9 This program is free software; you can redistribute it and/or modify 10 it under the terms of the GNU General Public License as published by 11 the Free Software Foundation; either version 3 of the License, or 12 (at your option) any later version. 13 14 This program is distributed in the hope that it will be useful, 15 but WITHOUT ANY WARRANTY; without even the implied warranty of 16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 GNU General Public License for more details. 18 19 You should have received a copy of the GNU General Public License 20 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 21 22/* This file defines functions (and commands to exercise those 23 functions) for reading debugging information from object files 24 whose images are mapped directly into the inferior's memory. For 25 example, the Linux kernel maps a "syscall DSO" into each process's 26 address space; this DSO provides kernel-specific code for some 27 system calls. 28 29 At the moment, BFD only has functions for parsing object files from 30 memory for the ELF format, even though the general idea isn't 31 ELF-specific. This means that BFD only provides the functions GDB 32 needs when configured for ELF-based targets. So these functions 33 may only be compiled on ELF-based targets. 34 35 GDB has no idea whether it has been configured for an ELF-based 36 target or not: it just tries to handle whatever files it is given. 37 But this means there are no preprocessor symbols on which we could 38 make these functions' compilation conditional. 39 40 So, for the time being, we put these functions alone in this file, 41 and have .mt files reference them as appropriate. In the future, I 42 hope BFD will provide a format-independent bfd_from_remote_memory 43 entry point. */ 44 45 46#include "defs.h" 47#include "symtab.h" 48#include "gdbcore.h" 49#include "objfiles.h" 50#include "exceptions.h" 51#include "gdbcmd.h" 52#include "target.h" 53#include "value.h" 54#include "symfile.h" 55#include "observer.h" 56#include "auxv.h" 57#include "elf/common.h" 58 59 60/* Read inferior memory at ADDR to find the header of a loaded object file 61 and read its in-core symbols out of inferior memory. TEMPL is a bfd 62 representing the target's format. NAME is the name to use for this 63 symbol file in messages; it can be NULL or a malloc-allocated string 64 which will be attached to the BFD. */ 65static struct objfile * 66symbol_file_add_from_memory (struct bfd *templ, CORE_ADDR addr, char *name, 67 int from_tty) 68{ 69 struct objfile *objf; 70 struct bfd *nbfd; 71 struct bfd_section *sec; 72 bfd_vma loadbase; 73 struct section_addr_info *sai; 74 unsigned int i; 75 76 if (bfd_get_flavour (templ) != bfd_target_elf_flavour) 77 error (_("add-symbol-file-from-memory not supported for this target")); 78 79 nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, &loadbase, 80 target_read_memory); 81 if (nbfd == NULL) 82 error (_("Failed to read a valid object file image from memory.")); 83 84 if (name == NULL) 85 nbfd->filename = xstrdup ("shared object read from target memory"); 86 else 87 nbfd->filename = name; 88 89 if (!bfd_check_format (nbfd, bfd_object)) 90 { 91 /* FIXME: should be checking for errors from bfd_close (for one thing, 92 on error it does not free all the storage associated with the 93 bfd). */ 94 bfd_close (nbfd); 95 error (_("Got object file from memory but can't read symbols: %s."), 96 bfd_errmsg (bfd_get_error ())); 97 } 98 99 sai = alloc_section_addr_info (bfd_count_sections (nbfd)); 100 make_cleanup (xfree, sai); 101 i = 0; 102 for (sec = nbfd->sections; sec != NULL; sec = sec->next) 103 if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0) 104 { 105 sai->other[i].addr = bfd_get_section_vma (nbfd, sec) + loadbase; 106 sai->other[i].name = (char *) bfd_get_section_name (nbfd, sec); 107 sai->other[i].sectindex = sec->index; 108 ++i; 109 } 110 111 objf = symbol_file_add_from_bfd (nbfd, from_tty ? SYMFILE_VERBOSE : 0, 112 sai, OBJF_SHARED); 113 114 /* This might change our ideas about frames already looked at. */ 115 reinit_frame_cache (); 116 117 return objf; 118} 119 120 121static void 122add_symbol_file_from_memory_command (char *args, int from_tty) 123{ 124 CORE_ADDR addr; 125 struct bfd *templ; 126 127 if (args == NULL) 128 error (_("add-symbol-file-from-memory requires an expression argument")); 129 130 addr = parse_and_eval_address (args); 131 132 /* We need some representative bfd to know the target we are looking at. */ 133 if (symfile_objfile != NULL) 134 templ = symfile_objfile->obfd; 135 else 136 templ = exec_bfd; 137 if (templ == NULL) 138 error (_("Must use symbol-file or exec-file " 139 "before add-symbol-file-from-memory.")); 140 141 symbol_file_add_from_memory (templ, addr, NULL, from_tty); 142} 143 144/* Arguments for symbol_file_add_from_memory_wrapper. */ 145 146struct symbol_file_add_from_memory_args 147{ 148 struct bfd *bfd; 149 CORE_ADDR sysinfo_ehdr; 150 char *name; 151 int from_tty; 152}; 153 154/* Wrapper function for symbol_file_add_from_memory, for 155 catch_exceptions. */ 156 157static int 158symbol_file_add_from_memory_wrapper (struct ui_out *uiout, void *data) 159{ 160 struct symbol_file_add_from_memory_args *args = data; 161 162 symbol_file_add_from_memory (args->bfd, args->sysinfo_ehdr, args->name, 163 args->from_tty); 164 return 0; 165} 166 167/* Try to add the symbols for the vsyscall page, if there is one. 168 This function is called via the inferior_created observer. */ 169 170static void 171add_vsyscall_page (struct target_ops *target, int from_tty) 172{ 173 CORE_ADDR sysinfo_ehdr; 174 175 if (target_auxv_search (target, AT_SYSINFO_EHDR, &sysinfo_ehdr) > 0 176 && sysinfo_ehdr != (CORE_ADDR) 0) 177 { 178 struct bfd *bfd; 179 struct symbol_file_add_from_memory_args args; 180 181 if (core_bfd != NULL) 182 bfd = core_bfd; 183 else if (exec_bfd != NULL) 184 bfd = exec_bfd; 185 else 186 /* FIXME: cagney/2004-05-06: Should not require an existing 187 BFD when trying to create a run-time BFD of the VSYSCALL 188 page in the inferior. Unfortunately that's the current 189 interface so for the moment bail. Introducing a 190 ``bfd_runtime'' (a BFD created using the loaded image) file 191 format should fix this. */ 192 { 193 warning (_("Could not load vsyscall page " 194 "because no executable was specified\n" 195 "try using the \"file\" command first.")); 196 return; 197 } 198 args.bfd = bfd; 199 args.sysinfo_ehdr = sysinfo_ehdr; 200 args.name = xstrprintf ("system-supplied DSO at %s", 201 paddress (target_gdbarch, sysinfo_ehdr)); 202 /* Pass zero for FROM_TTY, because the action of loading the 203 vsyscall DSO was not triggered by the user, even if the user 204 typed "run" at the TTY. */ 205 args.from_tty = 0; 206 catch_exceptions (uiout, symbol_file_add_from_memory_wrapper, 207 &args, RETURN_MASK_ALL); 208 } 209} 210 211 212 213/* Provide a prototype to silence -Wmissing-prototypes. */ 214extern initialize_file_ftype _initialize_symfile_mem; 215 216void 217_initialize_symfile_mem (void) 218{ 219 add_cmd ("add-symbol-file-from-memory", class_files, 220 add_symbol_file_from_memory_command, 221 _("Load the symbols out of memory from a " 222 "dynamically loaded object file.\n" 223 "Give an expression for the address " 224 "of the file's shared object file header."), 225 &cmdlist); 226 227 /* Want to know of each new inferior so that its vsyscall info can 228 be extracted. */ 229 observer_attach_inferior_created (add_vsyscall_page); 230} 231