Add an optional offset option to the "add-symbol-file" command

If all sections of a symbol file are loaded with a fixed offset, it
is easier to specify that offset than listing all sections
explicitly.  There is also a similar option for "symbol-file".

gdb/ChangeLog:
2018-06-28  Petr Tesarik  <ptesarik@suse.cz>

	* symfile.c (add_symbol_file_command, _initialize_symfile): Add
	option "-o" to add-symbol-file-load to add an offset to each
	section's load address.
	* symfile.c (set_objfile_default_section_offset): New function.

gdb/doc/ChangeLog:
2018-06-28  Petr Tesarik  <ptesarik@suse.cz>

	* gdb.texinfo (Files): Document "add-symbol-file -o offset".

gdb/testsuite/ChangeLog:
2018-06-28  Petr Tesarik  <ptesarik@suse.cz>

	* gdb.base/relocate.exp: Add test for "add-symbol-file -o ".

1 files changed, 80 insertions, 3 deletions

diff --git a/gdb/symfile.c b/gdb/symfile.c
index b592be7..48eca5c 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -2078,6 +2078,61 @@ print_transfer_performance (struct ui_file *stream,
   uiout->text (".\n");
 }
 
+/* Add an OFFSET to the start address of each section in OBJF, except
+   sections that were specified in ADDRS.  */
+
+static void
+set_objfile_default_section_offset (struct objfile *objf,
+				    const section_addr_info &addrs,
+				    CORE_ADDR offset)
+{
+  /* Add OFFSET to all sections by default.  */
+  std::vector<struct section_offsets> offsets (objf->num_sections,
+					       { offset });
+
+  /* Create sorted lists of all sections in ADDRS as well as all
+     sections in OBJF.  */
+
+  std::vector<const struct other_sections *> addrs_sorted
+    = addrs_section_sort (addrs);
+
+  section_addr_info objf_addrs
+    = build_section_addr_info_from_objfile (objf);
+  std::vector<const struct other_sections *> objf_addrs_sorted
+    = addrs_section_sort (objf_addrs);
+
+  /* Walk the BFD section list, and if a matching section is found in
+     ADDRS_SORTED_LIST, set its offset to zero to keep its address
+     unchanged.
+
+     Note that both lists may contain multiple sections with the same
+     name, and then the sections from ADDRS are matched in BFD order
+     (thanks to sectindex).  */
+
+  std::vector<const struct other_sections *>::iterator addrs_sorted_iter
+    = addrs_sorted.begin ();
+  for (const struct other_sections *objf_sect : objf_addrs_sorted)
+    {
+      const char *objf_name = addr_section_name (objf_sect->name.c_str ());
+      int cmp = -1;
+
+      while (cmp < 0 && addrs_sorted_iter != addrs_sorted.end ())
+	{
+	  const struct other_sections *sect = *addrs_sorted_iter;
+	  const char *sect_name = addr_section_name (sect->name.c_str ());
+	  cmp = strcmp (sect_name, objf_name);
+	  if (cmp <= 0)
+	    ++addrs_sorted_iter;
+	}
+
+      if (cmp == 0)
+	offsets[objf_sect->sectindex].offsets[0] = 0;
+    }
+
+  /* Apply the new section offsets.  */
+  objfile_relocate (objf, offsets.data ());
+}
+
 /* This function allows the addition of incrementally linked object files.
    It does not modify any state in the target, only in the debugger.  */
 /* Note: ezannoni 2000-04-13 This function/command used to have a
@@ -2109,6 +2164,7 @@ add_symbol_file_command (const char *args, int from_tty)
 
   std::vector<sect_opt> sect_opts = { { ".text", NULL } };
   bool stop_processing_options = false;
+  CORE_ADDR offset = 0;
 
   dont_repeat ();
 
@@ -2116,6 +2172,7 @@ add_symbol_file_command (const char *args, int from_tty)
     error (_("add-symbol-file takes a file name and an address"));
 
   bool seen_addr = false;
+  bool seen_offset = false;
   gdb_argv argv (args);
 
   for (arg = argv[0], argcnt = 0; arg != NULL; arg = argv[++argcnt])
@@ -2153,6 +2210,15 @@ add_symbol_file_command (const char *args, int from_tty)
 	  sect_opts.push_back (sect);
 	  argcnt += 2;
 	}
+      else if (strcmp (arg, "-o") == 0)
+	{
+	  arg = argv[++argcnt];
+	  if (arg == NULL)
+	    error (_("Missing argument to -o"));
+
+	  offset = parse_and_eval_address (arg);
+	  seen_offset = true;
+	}
       else if (strcmp (arg, "--") == 0)
 	stop_processing_options = true;
       else
@@ -2202,7 +2268,13 @@ add_symbol_file_command (const char *args, int from_tty)
 	 At this point, we don't know what file type this is,
 	 so we can't determine what section names are valid.  */
     }
-  if (section_addrs.empty ())
+  if (seen_offset)
+      printf_unfiltered (_("%s offset by %s\n"),
+			 (section_addrs.empty ()
+			  ? _(" with all sections")
+			  : _("with other sections")),
+			 paddress (gdbarch, offset));
+  else if (section_addrs.empty ())
     printf_unfiltered ("\n");
 
   if (from_tty && (!query ("%s", "")))
@@ -2211,6 +2283,9 @@ add_symbol_file_command (const char *args, int from_tty)
   objf = symbol_file_add (filename.get (), add_flags, &section_addrs,
 			  flags);
 
+  if (seen_offset)
+    set_objfile_default_section_offset (objf, section_addrs, offset);
+
   add_target_sections_of_objfile (objf);
 
   /* Getting new symbols may change our opinion about what is
@@ -3799,12 +3874,14 @@ to execute.\n" READNOW_READNEVER_HELP), &cmdlist);
 
   c = add_cmd ("add-symbol-file", class_files, add_symbol_file_command, _("\
 Load symbols from FILE, assuming FILE has been dynamically loaded.\n\
-Usage: add-symbol-file FILE [-readnow | -readnever] [ADDR] \
+Usage: add-symbol-file FILE [-readnow | -readnever] [-o OFF] [ADDR] \
 [-s SECT-NAME SECT-ADDR]...\n\
 ADDR is the starting address of the file's text.\n\
 Each '-s' argument provides a section name and address, and\n\
 should be specified if the data and bss segments are not contiguous\n\
-with the text.  SECT-NAME is a section name to be loaded at SECT-ADDR.\n"
+with the text.  SECT-NAME is a section name to be loaded at SECT-ADDR.\n\
+OFF is an optional offset which is added to the default load addresses\n\
+of all sections for which no other address was specified.\n"
 READNOW_READNEVER_HELP),
 	       &cmdlist);
   set_cmd_completer (c, filename_completer);