GDB (xrefs)

/tmp/gdb-8.1/gdb/symfile-mem.c
Go to the documentation of this file.
1 /* Reading symbol files from memory.
2
3 Copyright (C) 1986-2018 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 symfile_add_flags add_flags = 0;
95
96 if (bfd_get_flavour (templ) != bfd_target_elf_flavour)
97 error (_("add-symbol-file-from-memory not supported for this target"));
98
99 nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, size, &loadbase,
100 target_read_memory_bfd);
101 if (nbfd == NULL)
102 error (_("Failed to read a valid object file image from memory."));
103
104 /* Manage the new reference for the duration of this function. */
105 gdb_bfd_ref_ptr nbfd_holder = new_bfd_ref (nbfd);
106
107 xfree (bfd_get_filename (nbfd));
108 if (name == NULL)
109 nbfd->filename = xstrdup ("shared object read from target memory");
110 else
111 nbfd->filename = name;
112
113 if (!bfd_check_format (nbfd, bfd_object))
114 error (_("Got object file from memory but can't read symbols: %s."),
115 bfd_errmsg (bfd_get_error ()));
116
117 sai = alloc_section_addr_info (bfd_count_sections (nbfd));
118 cleanup = make_cleanup (xfree, sai);
119 i = 0;
120 for (sec = nbfd->sections; sec != NULL; sec = sec->next)
121 if ((bfd_get_section_flags (nbfd, sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
122 {
123 sai->other[i].addr = bfd_get_section_vma (nbfd, sec) + loadbase;
124 sai->other[i].name = (char *) bfd_get_section_name (nbfd, sec);
125 sai->other[i].sectindex = sec->index;
126 ++i;
127 }
128 sai->num_sections = i;
129
130 if (from_tty)
131 add_flags |= SYMFILE_VERBOSE;
132
133 objf = symbol_file_add_from_bfd (nbfd, bfd_get_filename (nbfd),
134 add_flags, sai, OBJF_SHARED, NULL);
135
136 add_target_sections_of_objfile (objf);
137
138 /* This might change our ideas about frames already looked at. */
139 reinit_frame_cache ();
140
141 do_cleanups (cleanup);
142 return objf;
143 }
144
145
146 static void
147 add_symbol_file_from_memory_command (const char *args, int from_tty)
148 {
149 CORE_ADDR addr;
150 struct bfd *templ;
151
152 if (args == NULL)
153 error (_("add-symbol-file-from-memory requires an expression argument"));
154
155 addr = parse_and_eval_address (args);
156
157 /* We need some representative bfd to know the target we are looking at. */
158 if (symfile_objfile != NULL)
159 templ = symfile_objfile->obfd;
160 else
161 templ = exec_bfd;
162 if (templ == NULL)
163 error (_("Must use symbol-file or exec-file "
164 "before add-symbol-file-from-memory."));
165
166 symbol_file_add_from_memory (templ, addr, 0, NULL, from_tty);
167 }
168
169 /* Try to add the symbols for the vsyscall page, if there is one.
170 This function is called via the inferior_created observer. */
171
172 static void
173 add_vsyscall_page (struct target_ops *target, int from_tty)
174 {
175 struct mem_range vsyscall_range;
176
177 if (gdbarch_vsyscall_range (target_gdbarch (), &vsyscall_range))
178 {
179 struct bfd *bfd;
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"));
195 return;
196 }
197
198 char *name = xstrprintf ("system-supplied DSO at %s",
199 paddress (target_gdbarch (), vsyscall_range.start));
200 TRY
201 {
202 /* Pass zero for FROM_TTY, because the action of loading the
203 vsyscall DSO was not triggered by the user, even if the
204 user typed "run" at the TTY. */
205 symbol_file_add_from_memory (bfd,
206 vsyscall_range.start,
207 vsyscall_range.length,
208 name,
209 0 /* from_tty */);
210 }
211 CATCH (ex, RETURN_MASK_ALL)
212 {
213 exception_print (gdb_stderr, ex);
214 }
215 END_CATCH
216 }
217 }
218
219 void
220 _initialize_symfile_mem (void)
221 {
222 add_cmd ("add-symbol-file-from-memory", class_files,
223 add_symbol_file_from_memory_command,
224 _("Load the symbols out of memory from a "
225 "dynamically loaded object file.\n"
226 "Give an expression for the address "
227 "of the file's shared object file header."),
228 &cmdlist);
229
230 /* Want to know of each new inferior so that its vsyscall info can
231 be extracted. */
232 observer_attach_inferior_created (add_vsyscall_page);
233 }
target_gdbarch
struct gdbarch * target_gdbarch(void)
Definition: gdbarch.c:5467
target_read_memory_bfd
static int target_read_memory_bfd(bfd_vma memaddr, bfd_byte *myaddr, bfd_size_type len)
Definition: symfile-mem.c:68
other_sections::name
char * name
Definition: symfile.h:51
add_vsyscall_page
static void add_vsyscall_page(struct target_ops *target, int from_tty)
Definition: symfile-mem.c:173
add_symbol_file_from_memory_command
static void add_symbol_file_from_memory_command(const char *args, int from_tty)
Definition: symfile-mem.c:147
CORE_ADDR
bfd_vma CORE_ADDR
Definition: common-types.h:41
RETURN_MASK_ALL
Definition: common-exceptions.h:44
xfree
void xfree(void *)
warning
void warning(const char *fmt,...)
Definition: errors.c:26
other_sections::sectindex
int sectindex
Definition: symfile.h:54
symbol_file_add_from_memory
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
add_cmd
struct cmd_list_element * add_cmd(const char *name, enum command_class theclass, const char *doc, struct cmd_list_element **list)
Definition: cli-decode.c:262
auxv.h
cmdlist
struct cmd_list_element * cmdlist
Definition: cli-cmds.c:79
OBJF_SHARED
Definition: objfile-flags.h:42
cleanup
Definition: cleanups.c:38
_
#define _(String)
Definition: gdb_locale.h:35
gdb_bfd.h
defs.h
gdbarch_vsyscall_range
int gdbarch_vsyscall_range(struct gdbarch *gdbarch, struct mem_range *range)
Definition: gdbarch.c:4945
END_CATCH
#define END_CATCH
Definition: common-exceptions.h:259
class_files
Definition: command.h:41
other_sections::addr
CORE_ADDR addr
Definition: symfile.h:50
paddress
const char * paddress(struct gdbarch *gdbarch, CORE_ADDR addr)
Definition: utils.c:2745
SYMFILE_VERBOSE
Definition: symfile-add-flags.h:32
objfiles.h
observer.h
new_bfd_ref
static gdb_bfd_ref_ptr new_bfd_ref(struct bfd *abfd)
Definition: gdb_bfd.h:75
observer_attach_inferior_created
struct observer * observer_attach_inferior_created(observer_inferior_created_ftype *f)
TRY
#define TRY
Definition: common-exceptions.h:246
symtab.h
name
const char *const name
Definition: aarch64-tdep.c:76
symbol_file_add_from_bfd
struct objfile * symbol_file_add_from_bfd(bfd *abfd, const char *name, symfile_add_flags add_flags, struct section_addr_info *addrs, objfile_flags flags, struct objfile *parent)
Definition: symfile.c:1257
gdb::ref_ptr
Definition: gdb_ref_ptr.h:49
CATCH
#define CATCH(EXCEPTION, MASK)
Definition: common-exceptions.h:254
_initialize_symfile_mem
void _initialize_symfile_mem(void)
Definition: symfile-mem.c:220
mem_range
Definition: memrange.h:27
target_ops
Definition: target.h:412
exec_bfd
#define exec_bfd
Definition: exec.h:33
exception_print
void exception_print(struct ui_file *file, struct gdb_exception e)
Definition: exceptions.c:109
make_cleanup
struct cleanup * make_cleanup(make_cleanup_ftype *function, void *arg)
Definition: cleanups.c:116
symfile_objfile
#define symfile_objfile
Definition: progspace.h:227
xstrprintf
char * xstrprintf(const char *format,...)
Definition: common-utils.c:107
section_addr_info
Definition: symfile.h:64
gdb_assert
#define gdb_assert(expr)
Definition: gdb_assert.h:32
section_addr_info::num_sections
size_t num_sections
Definition: symfile.h:68
objfile
Definition: objfiles.h:286
gdb_byte
bfd_byte gdb_byte
Definition: common-types.h:38
gdb_stderr
#define gdb_stderr
Definition: utils.h:344
gdbcore.h
parse_and_eval_address
CORE_ADDR parse_and_eval_address(const char *exp)
Definition: eval.c:101
target_read_memory
int target_read_memory(CORE_ADDR memaddr, gdb_byte *myaddr, ssize_t len)
Definition: target.c:1370
target.h
value.h
section_addr_info::other
struct other_sections other[1]
Definition: symfile.h:70
gdb_static_assert
gdb_static_assert(sizeof(CORE_ADDR)==sizeof(bfd_vma))
mem_range::length
int length
Definition: memrange.h:50
add_target_sections_of_objfile
void add_target_sections_of_objfile(struct objfile *objfile)
Definition: exec.c:561
core_bfd
bfd * core_bfd
Definition: corefile.c:54
reinit_frame_cache
void reinit_frame_cache(void)
Definition: frame.c:1809
gdbcmd.h
error
void error(const char *fmt,...)
Definition: errors.c:38
size
size_t size
Definition: go32-nat.c:242
do_cleanups
void do_cleanups(struct cleanup *old_chain)
Definition: cleanups.c:174
symfile.h
alloc_section_addr_info
struct section_addr_info * alloc_section_addr_info(size_t num_sections)
Definition: symfile.c:223
mem_range::start
CORE_ADDR start
Definition: memrange.h:47