Implement "-a" command line option for gcore

With the new "-a" command line option, the user may request gcore to
actually dump all present memory mappings. The actual effect of this
argument is OS dependent.

On GNU/Linux, it will disable use-coredump-filter and enable
dump-excluded-mappings.

gdb/ChangeLog:
2017-11-29  Sergio Lopez  <slp@redhat.com>

	* gcore.in: Add "-a" command line option for instructing gdb to
	dump all memory mappings (OS dependent).

gdb/gcore.in

@@ -20,27 +20,39 @@
 # It starts up gdb, attaches to the given PID and invokes the gcore command.
 #
 
-if [ "$#" -eq "0" ]
-then
-    echo "usage:  @GCORE_TRANSFORM_NAME@ [-o filename] pid"
-    exit 2
-fi
-
 # Need to check for -o option, but set default basename to "core".
 name=core
 
-if [ "$1" = "-o" ]
-then
-    if [ "$#" -lt "3" ]
-    then
-	# Not enough arguments.
-	echo "usage:  @GCORE_TRANSFORM_NAME@ [-o filename] pid"
-	exit 2
-    fi
-    name=$2
+# When the -a option is present, this may hold additional commands
+# to ensure gdb dumps all mappings (OS dependent).
+dump_all_cmds=()
 
-    # Shift over to start of pid list
-    shift; shift
+while getopts :ao: opt; do
+    case $opt in
+        a)
+            case $OSTYPE in
+                linux*)
+                    dump_all_cmds=("-ex" "set use-coredump-filter off")
+                    dump_all_cmds+=("-ex" "set dump-excluded-mappings on")
+                    ;;
+            esac
+            ;;
+        o)
+            name=$OPTARG
+            ;;
+        *)
+            echo "usage:  @GCORE_TRANSFORM_NAME@ [-a] [-o filename] pid"
+            exit 2
+            ;;
+    esac
+done
+
+shift $((OPTIND-1))
+
+if [ "$#" -eq "0" ]
+then
+    echo "usage:  @GCORE_TRANSFORM_NAME@ [-a] [-o filename] pid"
+    exit 2
 fi
 
 # Attempt to fetch the absolute path to the gcore script that was
@@ -87,6 +99,7 @@ do
 	# available but not accessible as GDB would get stopped on SIGTTIN.
 	$binary_path/@GDB_TRANSFORM_NAME@ </dev/null --nx --batch \
 	    -ex "set pagination off" -ex "set height 0" -ex "set width 0" \
+	    "${dump_all_cmds[@]}" \
 	    -ex "attach $pid" -ex "gcore $name.$pid" -ex detach -ex quit
 
 	if [ -r $name.$pid ] ; then