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/tmp/gdb-7.10/gdb/symfile-mem.c
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1 /* Reading symbol files from memory.
2 
3  Copyright (C) 1986-2015 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,
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 
134 
135  /* This might change our ideas about frames already looked at. */
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 
169 {
170  struct bfd *bfd;
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 = data;
184 
185  symbol_file_add_from_memory (args->bfd, args->sysinfo_ehdr, args->size,
186  args->name, args->from_tty);
187  return 0;
188 }
189 
190 /* Try to add the symbols for the vsyscall page, if there is one.
191  This function is called via the inferior_created observer. */
192 
193 static void
194 add_vsyscall_page (struct target_ops *target, int from_tty)
195 {
196  struct mem_range vsyscall_range;
197 
198  if (gdbarch_vsyscall_range (target_gdbarch (), &vsyscall_range))
199  {
200  struct bfd *bfd;
202 
203  if (core_bfd != NULL)
204  bfd = core_bfd;
205  else if (exec_bfd != NULL)
206  bfd = exec_bfd;
207  else
208  /* FIXME: cagney/2004-05-06: Should not require an existing
209  BFD when trying to create a run-time BFD of the VSYSCALL
210  page in the inferior. Unfortunately that's the current
211  interface so for the moment bail. Introducing a
212  ``bfd_runtime'' (a BFD created using the loaded image) file
213  format should fix this. */
214  {
215  warning (_("Could not load vsyscall page "
216  "because no executable was specified\n"
217  "try using the \"file\" command first."));
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;
231  &args, RETURN_MASK_ALL);
232  }
233 }
234 
235 
236 
237 /* Provide a prototype to silence -Wmissing-prototypes. */
239 
240 void
242 {
243  add_cmd ("add-symbol-file-from-memory", class_files,
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. */
254 }
struct gdbarch * target_gdbarch(void)
Definition: gdbarch.c:5143
static int target_read_memory_bfd(bfd_vma memaddr, bfd_byte *myaddr, bfd_size_type len)
Definition: symfile-mem.c:68
char * name
Definition: symfile.h:78
static void add_vsyscall_page(struct target_ops *target, int from_tty)
Definition: symfile-mem.c:194
#define OBJF_SHARED
Definition: objfiles.h:432
bfd_vma CORE_ADDR
Definition: common-types.h:41
void xfree(void *)
Definition: common-utils.c:97
struct objfile * symbol_file_add_from_bfd(bfd *abfd, const char *name, int add_flags, struct section_addr_info *addrs, int flags, struct objfile *parent)
Definition: symfile.c:1276
void warning(const char *fmt,...)
Definition: errors.c:26
int catch_exceptions(struct ui_out *uiout, catch_exceptions_ftype *func, void *func_args, return_mask mask)
Definition: exceptions.c:162
int sectindex
Definition: symfile.h:81
static struct objfile * symbol_file_add_from_memory(struct bfd *templ, CORE_ADDR addr, size_t size, char *name, int from_tty)
Definition: symfile-mem.c:84
struct cmd_list_element * cmdlist
Definition: cli-cmds.c:103
#define _(String)
Definition: gdb_locale.h:40
int gdbarch_vsyscall_range(struct gdbarch *gdbarch, struct mem_range *range)
Definition: gdbarch.c:4655
Definition: ui-out.c:99
CORE_ADDR addr
Definition: symfile.h:77
const char * paddress(struct gdbarch *gdbarch, CORE_ADDR addr)
Definition: utils.c:2743
static void add_symbol_file_from_memory_command(char *args, int from_tty)
Definition: symfile-mem.c:144
void gdb_bfd_ref(struct bfd *abfd)
Definition: gdb_bfd.c:439
struct observer * observer_attach_inferior_created(observer_inferior_created_ftype *f)
const char *const name
Definition: aarch64-tdep.c:68
void initialize_file_ftype(void)
Definition: defs.h:281
#define exec_bfd
Definition: exec.h:32
struct cmd_list_element * add_cmd(const char *name, enum command_class theclass, cmd_cfunc_ftype *fun, const char *doc, struct cmd_list_element **list)
Definition: cli-decode.c:192
struct cleanup * make_cleanup(make_cleanup_ftype *function, void *arg)
Definition: cleanups.c:117
#define gdb_assert(expr)
Definition: gdb_assert.h:33
#define symfile_objfile
Definition: progspace.h:216
static int symbol_file_add_from_memory_wrapper(struct ui_out *uiout, void *data)
Definition: symfile-mem.c:181
char * xstrprintf(const char *format,...)
Definition: common-utils.c:107
struct cleanup * make_cleanup_bfd_unref(bfd *abfd)
Definition: utils.c:189
size_t num_sections
Definition: symfile.h:95
bfd_byte gdb_byte
Definition: common-types.h:38
initialize_file_ftype _initialize_symfile_mem
CORE_ADDR parse_and_eval_address(const char *exp)
Definition: eval.c:96
int target_read_memory(CORE_ADDR memaddr, gdb_byte *myaddr, ssize_t len)
Definition: target.c:1393
struct other_sections other[1]
Definition: symfile.h:97
gdb_static_assert(sizeof(CORE_ADDR)==sizeof(bfd_vma))
int length
Definition: memrange.h:33
void add_target_sections_of_objfile(struct objfile *objfile)
Definition: exec.c:522
bfd * core_bfd
Definition: corefile.c:58
void reinit_frame_cache(void)
Definition: frame.c:1687
struct ui_out * current_uiout
Definition: ui-out.c:233
void error(const char *fmt,...)
Definition: errors.c:38
size_t size
Definition: go32-nat.c:242
void do_cleanups(struct cleanup *old_chain)
Definition: cleanups.c:175
struct section_addr_info * alloc_section_addr_info(size_t num_sections)
Definition: symfile.c:249
const ULONGEST const LONGEST len
Definition: target.h:309
CORE_ADDR start
Definition: memrange.h:30