commit afa840dcc021eaeb975dcde3bedbf46ea0511717
Author: Sergio Lopez <slp@redhat.com>
Date:   Mon Dec 4 09:17:12 2017 +0100

    Implement 'set dump-excluded-mappings' command
    
    Commit df8411da087dc05481926f4c4a82deabc5bc3859 implemented support for
    checking /proc/PID/coredump_filter, and also changed gcore behavior to
    unconditionally honor the VM_DONTDUMP flag, preventing sections marked
    as such for being dumped into the core file.
    
    This patch implements the 'set dump-excluded-mappings' command for
    instructing gdb to ignore the VM_DONTDUMP flag. Combined with 'set
    use-coredump-filter', this allows the user to restore the old behavior,
    dumping all sections (except the ones marked as IO) unconditionally.
    
    gdb/Changelog:
    2017-11-29  Sergio Lopez  <slp@redhat.com>
    
            * linux-tdep.c (dump_excluded_mappings): New variable.
            (dump_mapping_p): Use dump_excluded_mappings variable.
            (_initialize_linux_tdep): New command 'set dump_excluded_mappings'.

Index: gdb-7.6.1/gdb/linux-tdep.c
===================================================================
--- gdb-7.6.1.orig/gdb/linux-tdep.c	2017-12-06 20:38:51.182203906 +0100
+++ gdb-7.6.1/gdb/linux-tdep.c	2017-12-06 20:39:12.708343183 +0100
@@ -88,6 +88,11 @@
 
 static int use_coredump_filter = 1;
 
+/* Whether the value of smaps_vmflags->exclude_coredump should be
+   ignored, including mappings marked with the VM_DONTDUMP flag in
+   the dump.  */
+static int dump_excluded_mappings = 0;
+
 static struct gdbarch_data *linux_gdbarch_data_handle;
 
 struct linux_gdbarch_data
@@ -512,7 +517,7 @@
 	return 0;
 
       /* Check if we should exclude this mapping.  */
-      if (v->exclude_coredump)
+      if (!dump_excluded_mappings && v->exclude_coredump)
 	return 0;
 
       /* Update our notion of whether this mapping is shared or
@@ -1886,6 +1891,17 @@
 			    " corefiles is %s.\n"), value);
 }
 
+/* Display whether the gcore command is dumping mappings marked with
+   the VM_DONTDUMP flag.  */
+
+static void
+show_dump_excluded_mappings (struct ui_file *file, int from_tty,
+			     struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file, _("Dumping of mappings marked with the VM_DONTDUMP"
+			    " flag is %s.\n"), value);
+}
+
 /* To be called from the various GDB_OSABI_LINUX handlers for the
    various GNU/Linux architectures and machine types.  */
 
@@ -1921,4 +1937,16 @@
 about this file, refer to the manpage of core(5)."),
 			   NULL, show_use_coredump_filter,
 			   &setlist, &showlist);
+
+  add_setshow_boolean_cmd ("dump-excluded-mappings", class_files,
+			   &dump_excluded_mappings, _("\
+Set whether gcore should dump mappings marked with the VM_DONTDUMP flag."),
+			   _("\
+Show whether gcore should dump mappings marked with the VM_DONTDUMP flag."),
+			   _("\
+Use this command to set whether gcore should dump mappings marked with the\n\
+VM_DONTDUMP flag (\"dd\" in /proc/PID/smaps) when generating the corefile.  For\n\
+more information about this file, refer to the manpage of proc(5) and core(5)."),
+			   NULL, show_dump_excluded_mappings,
+			   &setlist, &showlist);
 }