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

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Date:   Thu, 17 Oct 2019 16:12:18 +0200
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Ilya Leoshkevich <iii@...ux.ibm.com>,
        Kieran Bingham <kbingham@...nel.org>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>
Subject: Re: [PATCH v2] scripts/gdb: fix debugging modules on s390

On 17.10.19 16:11, Jan Kiszka wrote:
> On 17.10.19 10:59, Ilya Leoshkevich wrote:
>> 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(
>>
> 
> Reviewed-by: Jan Kiszka <jan.kiszka@...mens.com>
> 
> Thanks,
> Jan
> 

Sorry, forgot to CC Andrew for pickup.

Jan

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