From 9fe6d3c7df8769ff54617ea8ae9d2a4ff91cbff9 Mon Sep 17 00:00:00 2001
From: Mathieu Maret <mathieu.maret@gmail.com>
Date: Thu, 20 Aug 2020 23:38:17 +0200
Subject: [PATCH] add some pretty-printer for kthread

---
 README.md               | 11 +++++++++
 custom_gdb_extension.py | 55 ++++++++++++++++++++++++++++++++++++++---
 2 files changed, 62 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 71aec0a..958c10a 100644
--- a/README.md
+++ b/README.md
@@ -16,3 +16,14 @@ To generate iso image
  you can also test it
 
  `make self_test`
+
+# Debug
+
+gdb could be launch with debug symbols using :
+
+ make debug
+
+Then you can check some matos specific commands or pretty printing with
+
+ help user-defined
+ info pretty-printer (Should contains matos_pretty_printers)
diff --git a/custom_gdb_extension.py b/custom_gdb_extension.py
index cd11ba0..0341750 100644
--- a/custom_gdb_extension.py
+++ b/custom_gdb_extension.py
@@ -1,3 +1,48 @@
+from gdb.printing import PrettyPrinter, register_pretty_printer
+import gdb
+
+class KthreadPrettyPrinter(object):
+
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        result = ""
+        name = self.val["name"]
+        state = self.val["state"]
+        # Should get PC on stack for non-current thread otherwise will only get address in cpu_context_switch
+        cpuState = self.val["cpuState"]
+        cmdline = "info line *%s"%int(cpuState["eip"].cast(gdb.lookup_type("long").pointer()))
+        line = gdb.execute(cmdline, to_string=True)
+        #line = gdb.find_pc_line(int(cpuState["eip"].cast(gdb.lookup_type("long").pointer()).referenced_value()))
+        currentThread = gdb.parse_and_eval("currentThread")
+        if self.val == currentThread:
+            result += "->"
+        else:
+            result += "  "
+        result += "Addr: 0x%x, name: %s, state: %s, PC: %s" % (self.val, name, state, line)
+        return result
+
+
+class CustomPrettyPrinterLocator(PrettyPrinter):
+    """Given a gdb.Value, search for a custom pretty printer"""
+
+    def __init__(self):
+        super(CustomPrettyPrinterLocator, self).__init__(
+            "matos_pretty_printers", []
+        )
+
+    def __call__(self, val):
+        """Return the custom formatter if the type can be handled"""
+
+        typename = gdb.types.get_basic_type(val.type).tag
+        if typename is None:
+            typename = val.type.name
+
+        if typename == "kthread":
+            return KthreadPrettyPrinter(val)
+
+
 class KthreadListDumpCmd(gdb.Command):
     """Prints the kthread list"""
 
@@ -16,8 +61,7 @@ class KthreadListDumpCmd(gdb.Command):
         kthread_ptr = val
         result = ""
         while kthread_ptr != 0 and (idx == 0 or kthread_ptr != head) :
-            name = kthread_ptr["name"]
-            result += "\n%d: Addr: 0x%x, name: %s" % (idx, kthread_ptr, name)
+            result += "\n%d: %s" % (idx, KthreadPrettyPrinter(kthread_ptr).to_string())
             kthread_ptr = kthread_ptr["next"]
             idx += 1
         result = ("Found a Linked List with %d kthread:" % idx) + result
@@ -32,13 +76,16 @@ class KthreadListDumpCmd(gdb.Command):
         # We can pass args here and use Python CLI utilities like argparse
         # to do argument parsing
         print("Args Passed: %s" % args)
-
-        kthread_ptr_val = gdb.parse_and_eval(args)
+        if args:
+            kthread_ptr_val = gdb.parse_and_eval(args)
+        else:
+            kthread_ptr_val = gdb.parse_and_eval("currentThread")
         if str(kthread_ptr_val.type) != "struct kthread *":
             print("Expected pointer argument of type (struct kthread *)")
             return
 
         print(self._kthread_list_to_str(kthread_ptr_val))
 
+register_pretty_printer(None, CustomPrettyPrinterLocator(), replace=True)
 KthreadListDumpCmd()