Subject: Re: [PATCH] scripts/gdb/symbols: follow up on refactoring for const struct bin_attribute

From: Mohamed Khalfella <[email-masked]>
Date: Wed, 12 Feb 2025 20:38:06 -0800

On 2025-01-12 21:21:49 +0900, Koichiro Den wrote:
> The work for 'const struct bin_attribute' [1] was merged into linux-next
> but did not include updates to the lx-symbols code. So it now fails with
> the following error:
> Python Exception <class 'gdb.error'>: There is no member named nsections.
> Error occurred in Python: There is no member named nsections.
> 
> Restore its functionality by aligning it with those changes on
> kernel/module/sysfs.c.
> 
> [1] https://lore.kernel.org/all/[email-masked]/
> 
> Signed-off-by: Koichiro Den <[email-masked]>
> ---
>  scripts/gdb/linux/symbols.py | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/scripts/gdb/linux/symbols.py b/scripts/gdb/linux/symbols.py
> index f6c1b063775a..8efefd30df49 100644
> --- a/scripts/gdb/linux/symbols.py
> +++ b/scripts/gdb/linux/symbols.py
> @@ -89,16 +89,26 @@ lx-symbols command."""
>                  return name
>          return None
>  
> +    def _iter_bin_attrs(self, bin_attrs):
> +        while True:
> +            try:
> +                bin_attr = bin_attrs.dereference()
> +            except gdb.MemoryError:

This should not result in an exception. The array should at least have
one element on it, that is the NULL terminator.

> +                break
> +            if bin_attr == 0:
> +                break
> +            yield bin_attr
> +            bin_attrs += 1
> +
>      def _section_arguments(self, module, module_addr):
>          try:
>              sect_attrs = module['sect_attrs'].dereference()
>          except gdb.error:
>              return str(module_addr)
>  
> -        attrs = sect_attrs['attrs']
>          section_name_to_address = {
> -            attrs[n]['battr']['attr']['name'].string(): attrs[n]['address']
> -            for n in range(int(sect_attrs['nsections']))}
> +            bin_attr['attr']['name'].string(): bin_attr['private']
> +            for bin_attr in self._iter_bin_attrs(sect_attrs['grp']['bin_attrs'])}
>  
>          textaddr = section_name_to_address.get(".text", module_addr)
>          args = []
> -- 
> 2.45.2
> 

Hello Koichiro,

I hit the same problem came up with similar fix below. Of course I am
biased and I think my change is more concise. Feel free to take from it.
Looks like many commits changed this code and any of them would break
python code. Can you please add Fixes tag at least to the top commit.

34f5ec0f8252 ("module: sysfs: Drop 'struct module_sect_attr'")
4b2c11e4aaf7 ("module: sysfs: Drop member 'module_sect_attr::address'")
d8959b947a8d ("module: sysfs: Drop member 'module_sect_attrs::nsections'")

diff --git a/scripts/gdb/linux/symbols.py b/scripts/gdb/linux/symbols.py
index f6c1b063775a..e4865ec5aebe 100644
--- a/scripts/gdb/linux/symbols.py
+++ b/scripts/gdb/linux/symbols.py
@@ -95,10 +95,15 @@ lx-symbols command."""
         except gdb.error:
             return str(module_addr)

-        attrs = sect_attrs['attrs']
-        section_name_to_address = {
-            attrs[n]['battr']['attr']['name'].string(): attrs[n]['address']
-            for n in range(int(sect_attrs['nsections']))}
+        section_name_to_address = {}
+        gattr = sect_attrs['grp']['bin_attrs']
+        battr = gattr.dereference()
+        while battr:
+            sec_name = battr['attr']['name'].string()
+            sec_addr = battr['private']
+            section_name_to_address[sec_name] = sec_addr
+            gattr = gattr + 1
+            battr = gattr.dereference()

         textaddr = section_name_to_address.get(".text", module_addr)
         args = []