[PATCH v1 7/8] gdb/linux-tdep: parse ProtectionKey in /proc/PID/smaps

[Matthieu Longo <matthieu.longo@arm.com>]

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 e6697669f3d..5312dad176f 100644
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -127,6 +127,7 @@ struct smaps_data
 
   ULONGEST rss;
   ULONGEST swap;
+  std::optional<int> pkey;
 };
 
 /* Whether to take the /proc/PID/coredump_filter into account when
@@ -1552,6 +1553,7 @@ 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);
@@ -1652,6 +1654,16 @@ 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 ());
+		  break;
+		}
+	    }
 	}
       /* Save the smaps entry to the vector.  */
 	struct smaps_data map;
@@ -1671,6 +1683,7 @@ parse_smaps_data (const file_reader_t<char> &freader)
 	map.inode = m.inode;
 	map.rss = rss;
 	map.swap = swap;
+	map.pkey.emplace (pkey);
 
 	smaps.emplace_back (map);
     }
-- 
2.55.0