Re: [PATCH v1 09/10] gdb/linux-tdep: parse ProtectionKey in /proc/PID/smaps

Drive-by review.

On 07/07/2026 16:48, Matthieu Longo wrote:
> Memory Protection Keys provide a mechanism for enforcing page-based
> protections without requiring modification of the page tables
> when an application changes protection domains. [1]
> 
> The "ProtectionKey" field may be present in /proc/PID/smaps x86_64
> and AArch64 systems since Linux 4.9, when the kernel is built with
> Memory Protection Keys support.
> 
> Add a new 'pkey' field to `struct smaps_data', and populate it when
> the "ProtectionKey" field is present.
> 
> This prepares for displaying the protection key in 'info proc mappings'.
> 
> [1]: https://docs.kernel.org/core-api/protection-keys.html,
>       https://lkml.iu.edu/1512.0/03058.html
> ---
>   gdb/linux-tdep.c | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
> 
> diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
> index dbc69a5a7fc..d89c5ae8504 100644
> --- a/gdb/linux-tdep.c
> +++ b/gdb/linux-tdep.c
> @@ -124,6 +124,7 @@ struct smaps_data
>   
>     ULONGEST rss;
>     ULONGEST swap;
> +  std::optional<int> pkey;
>   };
>   
>   /* Whether to take the /proc/PID/coredump_filter into account when
> @@ -1553,6 +1554,7 @@ parse_smaps_data (const file_reader_t<char> &freader)
>         int mapping_file_p;
>         ULONGEST rss = -1;
>         ULONGEST swap = -1;
> +      int pkey = -1;
>   
>         memset (&v, 0, sizeof (v));
>         struct mapping m = read_mapping (line);
> @@ -1653,6 +1655,16 @@ parse_smaps_data (const file_reader_t<char> &freader)
>   		  mapping_anon_p = 1;
>   		}
>   	    }
> +
> +	  if (streq (keyword, "ProtectionKey:"))
> +	    {
> +	      if (sscanf (line, "%*s%d", &pkey) != 1)
> +		{
> +		  warning (_("Error parsing %s's value in {s,}maps file '%s'"),
> +			   keyword, freader.c_filepath ());

If keyword has the trailing colon this will read...

Error parsing ProtectionKey:'s value

... right?

> +		  break;
> +		}
> +	    }
>   	}
>         /* Save the smaps entry to the vector.  */
>   	struct smaps_data map;
> @@ -1672,6 +1684,7 @@ parse_smaps_data (const file_reader_t<char> &freader)
>   	map.inode = m.inode;
>   	map.rss = rss;
>   	map.swap = swap;
> +	map.pkey.emplace (pkey);

Are we always unconditionally adding a key by design, even when no keys 
were found? Then we add the sentinel -1. Or am I missing something?

>   
>   	smaps.emplace_back (map);
>       }

And I agree with Thiago. This patch should live alongside Srinath's series.