scripts/gdb: fix debugging modules on s390

Currently lx-symbols assumes that module text is always located at
module->core_layout->base, but s390 uses the following layout:

+------+ <- module->core_layout->base
| GOT |
+------+ <- module->core_layout->base + module->arch->plt_offset
| PLT |
+------+ <- module->core_layout->base + module->arch->plt_offset +
| TEXT | module->arch->plt_size
+------+

Therefore, when trying to debug modules on s390, all the symbol
addresses are skewed by plt_offset + plt_size.

Fix by adding plt_offset + plt_size to module_addr in
load_module_symbols().

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ilya Leoshkevich <[e-mail]>
Reviewed-by: Jan Kiszka <[e-mail]>
Cc: Kieran Bingham <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Vasily Gorbik <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

scripts/gdb/linux/symbols.py

···
 import os
 import re
 
-from linux import modules
+from linux import modules, utils
 
 
 if hasattr(gdb, 'Breakpoint'):
···
             module_file = self._get_module_file(module_name)
 
         if module_file:
+            if utils.is_target_arch('s390'):
+                # Module text is preceded by PLT stubs on s390.
+                module_arch = module['arch']
+                plt_offset = int(module_arch['plt_offset'])
+                plt_size = int(module_arch['plt_size'])
+                module_addr = hex(int(module_addr, 0) + plt_offset + plt_size)
             gdb.write("loading @{addr}: {filename}\n".format(
                 addr=module_addr, filename=module_file))
             cmdline = "add-symbol-file {filename} {addr}{sections}".format(