scripts/gdb: add get_target_endianness helper

Parse the target endianness from the output of "show endian" and cache the
result to return it via the new helper get_target_endiannes.  We will need
it for reading integers from buffers that contain target memory.

Signed-off-by: Jan Kiszka <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Jason Wessel <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Ben Widawsky <[email protected]>
Cc: Borislav Petkov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

scripts/gdb/linux/utils.py

@@ -67,3 +67,21 @@ def invoke(self, ptr, typename, elementname):
                             elementname.string())
 
 ContainerOf()
+
+
+BIG_ENDIAN = 0
+LITTLE_ENDIAN = 1
+target_endianness = None
+
+
+def get_target_endianness():
+    global target_endianness
+    if target_endianness is None:
+        endian = gdb.execute("show endian", to_string=True)
+        if "little endian" in endian:
+            target_endianness = LITTLE_ENDIAN
+        elif "big endian" in endian:
+            target_endianness = BIG_ENDIAN
+        else:
+            raise gdb.GdgError("unknown endianness '{0}'".format(endian))
+    return target_endianness