Add an optional offset option to the "symbol-file" command
Commit Message
On Friday, May 25, 2018 10:14:35 AM Simon Marchi wrote:
> On 2018-05-25 01:23, Petr Tesarik wrote:
> > Yes, technically, add-symbol-file can be used for the same purpose, but
> > it is very inconvenient. Most notably, it requires listing all ELF
> > sections explicitly, and the Linux kernel has a lot of them (typically
> > a few dozen).
> >
> > So, my current solution is:
> >
> > 1. exec-file vmlinux
> > 2. info target
> > 3. # parse the output, adding an offset to each section's start
> > 4. add-symbol-file vmlinux $textaddr -s ... # a very long list
> > 5. exec-file # to make sure that only target memory is used
> >
> > Although I have already written a Python script to initialise the
> > session, it's ugly, especially when it comes to parsing the output of
> > "info target".
>
> Thanks for confirming.
>
> > Regarding consistency, add-symbol-file does not currently have any
> > conflicting "-o" option, so I can add one for the same purpose.
> >
> > Shall I do that?
>
> I think it would be a good idea. It would improve the usability of
> add-symbol-file and keep both commands more or less in sync, so it
> sounds like a win-win to me.
>
> I assume the second positional argument of add-symbol-file (which gives
> the start address of .text) would become optional? You just need to
> think carefully about what should happen when mixing the different
> arguments. The .text positional argument and -o would probably be
> mutually exclusive? -o applies to all sections, but you could use -s to
> override the address of a particular section?
Please do this. I have an old branch with an 'add_symbol_file_rel' that
tried to do this (but the syntax was a bit clumsy). My use case was debugging
an EFI appliation via the GDB stub in qemu. I've included the patch below
in case it is useful.
commit d4ae4cb5271baacc2754e0ee89415c66a5296133
Author: John Baldwin <jhb@FreeBSD.org>
Date: Fri Mar 6 15:09:01 2015 -0500
Add a variant of 'add-symbol-file' that accepts a single base address
of the image and relocates all sections in the file by adding the
base address.
@@ -89,6 +89,8 @@ static void symbol_file_add_main_1 (const char *args, int from_tty, int flags);
static void add_symbol_file_command (char *, int);
+static void add_symbol_file_rel_command (char *, int);
+
static const struct sym_fns *find_sym_fns (bfd *);
static void decrement_reading_symtab (void *);
@@ -2406,6 +2408,74 @@ add_symbol_file_command (char *args, int from_tty)
}
+static void
+add_symbol_file_rel_command (char *args, int from_tty)
+{
+ struct gdbarch *gdbarch = get_current_arch ();
+ int flags = OBJF_USERLOADED | OBJF_SHARED;
+ CORE_ADDR base_addr;
+ char *arg;
+ int argcnt = 0;
+ int i;
+ char **argv;
+ struct objfile *objf;
+ bfd *bfd;
+
+ struct section_addr_info *section_addrs;
+ struct cleanup *my_cleanups = make_cleanup (null_cleanup, NULL);
+
+ dont_repeat ();
+
+ if (args == NULL)
+ error (_("add-symbol-file-rel takes a file name and an address"));
+
+ argv = gdb_buildargv (args);
+ make_cleanup_freeargv (argv);
+
+ if (argv[0] == NULL || argv[1] == NULL)
+ error (_("add-symbol-file-rel takes a file name and an address"));
+
+ /* The first argument is the file name. */
+ bfd = symfile_bfd_open (argv[0]);
+ make_cleanup_bfd_unref (bfd);
+
+ /* The second argument is the base address. */
+ base_addr = parse_and_eval_address (argv[1]);
+
+ /* Handle optional arguments. */
+ for (arg = argv[2], argcnt = 2; arg != NULL; arg = argv[++argcnt])
+ {
+ if (strcmp (arg, "-readnow") == 0)
+ flags |= OBJF_READNOW;
+ else
+ error (_("USAGE: add-symbol-file-rel <filename> <baseaddress>"
+ " [-readnow]"));
+ }
+
+ section_addrs = build_section_addr_info_from_bfd (bfd);
+ make_cleanup_free_section_addr_info (section_addrs);
+ for (i = 0; i < section_addrs->num_sections; i++)
+ {
+ section_addrs->other[i].addr += base_addr;
+ printf_unfiltered ("\t%s_addr = %s\n", section_addrs->other[i].name,
+ paddress (gdbarch, section_addrs->other[i].addr));
+ }
+
+ if (from_tty && (!query ("%s", "")))
+ error (_("Not confirmed."));
+
+ objf = symbol_file_add_from_bfd (bfd, argv[0], from_tty ? SYMFILE_VERBOSE : 0,
+ section_addrs, flags, NULL);
+
+ add_target_sections_of_objfile (objf);
+
+ /* Getting new symbols may change our opinion about what is
+ frameless. */
+ reinit_frame_cache ();
+ do_cleanups (my_cleanups);
+}
+
+
/* This function removes a symbol file that was added via add-symbol-file. */
static void
@@ -3998,6 +4068,15 @@ with the text. SECT is a section name to be loaded at SECT_ADDR."),
&cmdlist);
set_cmd_completer (c, filename_completer);
+ c = add_cmd ("add-symbol-file-rel", class_files, add_symbol_file_rel_command,
+ _("\
+Load symbols from FILE, assuming FILE has been dynamically loaded.\n\
+Usage: add-symbol-file-rel FILE ADDR\n\
+ADDR is the base address of the file. The base address is added to the\n\
+address of each loaded section."),
+ &cmdlist);
+ set_cmd_completer (c, filename_completer);
+
c = add_cmd ("remove-symbol-file", class_files,
remove_symbol_file_command, _("\
Remove a symbol file added via the add-symbol-file command.\n\