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

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

[Ilya Leoshkevich]

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@linux.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

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

[Jan Kiszka]

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@linux.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@siemens.com>

Thanks,
Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

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

[Jan Kiszka]

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@linux.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@siemens.com>
> 
> Thanks,
> Jan
> 

Sorry, forgot to CC Andrew for pickup.

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux