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