[PATCH AUTOSEL 4.9 21/21] scripts/gdb: fix debugging modules on s390

[Sasha Levin <sashal@kernel.org>]

From: Ilya Leoshkevich <iii@linux.ibm.com>

[ Upstream commit 585d730d41120926e3f79a601edad3930fa28366 ]

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/20191017085917.81791-1-iii@linux.ibm.com
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 scripts/gdb/linux/symbols.py | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/scripts/gdb/linux/symbols.py b/scripts/gdb/linux/symbols.py
index 004b0ac7fa72d..d869e588f4ec4 100644
--- a/scripts/gdb/linux/symbols.py
+++ b/scripts/gdb/linux/symbols.py
@@ -15,7 +15,7 @@ import gdb
 import os
 import re
 
-from linux import modules
+from linux import modules, utils
 
 
 if hasattr(gdb, 'Breakpoint'):
@@ -116,6 +116,12 @@ lx-symbols command."""
             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(
-- 
2.20.1