From 220597a88153338589ae80a008c11834e37433e7 Mon Sep 17 00:00:00 2001
From: Mathieu Maret <mathieu.maret@gmail.com>
Date: Thu, 19 Aug 2021 16:42:44 +0200
Subject: [PATCH] gdb: add custom cmd for printing linked list

---
 custom_gdb_extension.py | 86 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/custom_gdb_extension.py b/custom_gdb_extension.py
index 3af1f4c..5ce128e 100644
--- a/custom_gdb_extension.py
+++ b/custom_gdb_extension.py
@@ -136,6 +136,92 @@ class PhyMemDescListDumpCmd(gdb.Command):
         print(self._phy_memDesc_lit_to_str(desc))
 
 
+class PrintStructC99Cmd(gdb.Command):
+    def __init__(self):
+        super(PrintStructC99Cmd, self).__init__(
+            "print_struct_c99",
+            gdb.COMMAND_USER,
+        )
+
+    def complete(self, text, word):
+        return gdb.COMPLETE_SYMBOL
+
+    def get_count_heading(self, string):
+        for i, s in enumerate(string):
+            if s != ' ':
+                break
+        return i
+
+    def extract_typename(self, string):
+        first_line = string.split('\n')[0]
+        return first_line.split('=')[1][:-1].strip()
+
+    def invoke(self, arg, from_tty):
+        gdb.execute("set print pretty")
+        gdb.execute('set pagination off')
+        gdb.execute('set print repeats 0')
+        gdb.execute('set print elements unlimited')
+        ret_ptype = gdb.execute('ptype {}'.format(arg), to_string=True)
+        tname = self.extract_typename(ret_ptype)
+        print('{} {} = {{'.format(tname, arg))
+        r = gdb.execute('p {}'.format(arg), to_string=True)
+        r = r.split('\n')
+        for rr in r[1:]:
+            if '=' not in rr:
+                print(rr)
+                continue
+            hs = self.get_count_heading(rr)
+            rr_s = rr.strip().split('=', 1)
+            rr_rval = rr_s[1].strip()
+            print(' ' * hs + '.' + rr_s[0] + '= ' + rr_rval)
+
+class ListDumpCmd(gdb.Command):
+    """Prints a linked list"""
+
+    def __init__(self):
+        super(ListDumpCmd, self).__init__(
+            "list_dump", gdb.COMMAND_USER
+        )
+
+    def _print_list(self, val):
+        """Walk through the linked list.
+
+        We will simply follow the 'next' pointers until we encounter the HEAD again
+        """
+        idx = 0
+        head = val
+        kthread_ptr = val
+        result = ""
+        while kthread_ptr != 0 and (idx == 0 or kthread_ptr != head):
+            result += gdb.execute('p *({}){}'.format(str(kthread_ptr.type),kthread_ptr), to_string=True)
+            kthread_ptr = kthread_ptr["next"]
+            idx += 1
+        result = ("Found a Linked List with %d items:" % idx) + "\n"+ result
+        return result
+
+    def complete(self, text, word):
+        # We expect the argument passed to be a symbol so fallback to the
+        # internal tab-completion handler for symbols
+        return gdb.COMPLETE_SYMBOL
+
+    def invoke(self, args, from_tty):
+        # We can pass args here and use Python CLI utilities like argparse
+        # to do argument parsing
+        print("Args Passed: %s" % args)
+        if args:
+            ptr_val = gdb.parse_and_eval(args)
+        else:
+            ptr_val = gdb.parse_and_eval("currentThread")
+        try:
+            ptr_val["next"]
+        except:
+            print("Expected pointer argument with a next field")
+            return
+
+        print(self._print_list(ptr_val))
+
 register_pretty_printer(None, CustomPrettyPrinterLocator(), replace=True)
 KthreadListDumpCmd()
 PhyMemDescListDumpCmd()
+PrintStructC99Cmd()
+ListDumpCmd()