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

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Message-Id: <20191015105313.12663-1-iii@linux.ibm.com>
Date:   Tue, 15 Oct 2019 12:53:13 +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] 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>
---
 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..41c6d1a55b03 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'):
@@ -113,6 +113,12 @@ lx-symbols command."""
         if module_file:
             gdb.write("loading @{addr}: {filename}\n".format(
                 addr=module_addr, filename=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)
             cmdline = "add-symbol-file {filename} {addr}{sections}".format(
                 filename=module_file,
                 addr=module_addr,
-- 
2.23.0