linux-kernel - [PATCH v2] scripts/gdb: fix debugging modules on s390

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Date:   Thu, 17 Oct 2019 10:59:17 +0200
From:   Ilya Leoshkevich <iii@...ux.ibm.com>
To:     Jan Kiszka <jan.kiszka@...mens.com>,
        Kieran Bingham <kbingham@...nel.org>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>
Subject: [PATCH v2] 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().

Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
---

v1 -> v2: print the adjusted address.

 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 f0d8f2ecfde7..df4c810de663 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'):
@@ -111,6 +111,12 @@ 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(
-- 
2.23.0