Meta: Add GDB pretty printers

Author: https://github.com/gunnarbeutner
Commit: https://github.com/SerenityOS/serenity/commit/232e64c10a2
Pull-request: https://github.com/SerenityOS/serenity/pull/6530
Reviewed-by: https://github.com/bgianfo ✅
Reviewed-by: https://github.com/linusg

Meta/debug-kernel.sh

@@ -8,7 +8,9 @@
 # remote on localhost:1234. So point our debugger there, and inform
 # the debugger which binary to load symbols, etc from.
 #
-$SERENITY_KERNEL_DEBUGGER \
+exec $SERENITY_KERNEL_DEBUGGER \
     -ex "file $(dirname "$0")/../Build/${SERENITY_ARCH:-i686}/Kernel/Kernel" \
     -ex 'set arch i386:intel' \
-    -ex 'target remote localhost:1234'
+    -ex 'target remote localhost:1234' \
+    -ex "source $(dirname "$0")/serenity_gdb.py" \
+    "$@"

Meta/serenity.sh

@@ -201,7 +201,8 @@ run_gdb() {
         if [ -n "$KERNEL_CMD_LINE" ]; then
             export SERENITY_KERNEL_CMDLINE="$KERNEL_CMD_LINE"
         fi
-        gdb "$BUILD_DIR/Kernel/Kernel" -ex 'target remote :1234' "${GDB_ARGS[@]}" -ex cont
+        sleep 1
+        "$(get_top_dir)/Meta/debug-kernel.sh" "${GDB_ARGS[@]}" -ex cont
     fi
 }
 

Meta/serenity_gdb.py

@@ -0,0 +1,274 @@
+# Copyright (c) 2021, Gunnar Beutner <gunnar@beutner.name>
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# 1. Redistributions of source code must retain the above copyright notice, this
+#    list of conditions and the following disclaimer.
+#
+# 2. Redistributions in binary form must reproduce the above copyright notice,
+#    this list of conditions and the following disclaimer in the documentation
+#    and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+import gdb
+import gdb.types
+import re
+
+
+class AKAtomic:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return self.val["m_value"]
+
+
+class AKDistinctNumeric:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return self.val["m_value"]
+
+
+class AKRefCounted:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return self.val["m_ref_count"]
+
+
+class AKString:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        if int(self.val["m_impl"]["m_bits"]["m_value"]) == 0:
+            return '""'
+        else:
+            impl = AKRefPtr(self.val["m_impl"]).get_pointee().dereference()
+            return AKStringImpl(impl).to_string()
+
+
+class AKStringView:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        if int(self.val["m_length"]) == 0:
+            return '""'
+        else:
+            characters = self.val["m_characters"]
+            str_type = characters.type.target().array(self.val["m_length"]).pointer()
+            return str(characters.cast(str_type).dereference())
+
+
+def get_field_unalloced(val, member, type):
+    # Trying to access a variable-length field seems to fail with
+    # Python Exception <class 'gdb.error'> value requires 4294967296 bytes, which is more than max-value-size
+    # This works around that issue.
+    return gdb.parse_and_eval(f"*({type}*)(({val.type.name}*){int(val.address)})->{member}")
+
+
+class AKStringImpl:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        if int(self.val["m_length"]) == 0:
+            return '""'
+        else:
+            str_type = gdb.lookup_type("char").array(self.val["m_length"])
+            return get_field_unalloced(self.val, "m_inline_buffer", str_type)
+
+
+class AKOwnPtr:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return self.val.type.name
+
+    def children(self):
+        return [('*', self.val["m_ptr"])]
+
+
+class AKRefPtr:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return self.val.type.name
+
+    def get_pointee(self):
+        inner_type = self.val.type.template_argument(0)
+        inner_type_ptr = inner_type.pointer()
+        return self.val["m_bits"]["m_value"].cast(inner_type_ptr)
+
+    def children(self):
+        return [('*', self.get_pointee())]
+
+
+class AKVector:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return f'{self.val.type.name} of len {int(self.val["m_size"])}'
+
+    def children(self):
+        vec_len = int(self.val["m_size"])
+
+        if vec_len == 0:
+            return []
+
+        outline_buf = self.val["m_outline_buffer"]
+
+        inner_type_ptr = self.val.type.template_argument(0).pointer()
+
+        if int(outline_buf) != 0:
+            elements = outline_buf.cast(inner_type_ptr)
+        else:
+            elements = get_field_unalloced(self.val, "m_inline_buffer_storage", inner_type_ptr)
+
+        return [(f"[{i}]", elements[i]) for i in range(vec_len)]
+
+
+class AKHashMapPrettyPrinter:
+    def __init__(self, val):
+        self.val = val
+
+    @staticmethod
+    def _iter_hashtable(val, cb):
+        entry_type_ptr = val.type.template_argument(0).pointer()
+        buckets = val["m_buckets"]
+        for i in range(0, val["m_capacity"]):
+            bucket = buckets[i]
+            if bucket["used"]:
+                cb(bucket["storage"].cast(entry_type_ptr))
+
+    @staticmethod
+    def _iter_hashmap(val, cb):
+        table = val["m_table"]
+        AKHashMapPrettyPrinter._iter_hashtable(table, lambda entry: cb(entry["key"], entry["value"]))
+
+    def to_string(self):
+        return self.val.type.name
+
+    def children(self):
+        elements = []
+
+        def cb(key, value):
+            nonlocal elements
+            elements.append((f"[{key}]", value))
+
+        AKHashMapPrettyPrinter._iter_hashmap(self.val, cb)
+        return elements
+
+
+class VirtualAddress:
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return self.val["m_address"]
+
+
+class SerenityPrettyPrinterLocator(gdb.printing.PrettyPrinter):
+    def __init__(self):
+        super(SerenityPrettyPrinterLocator, self).__init__("serenity_pretty_printers", [])
+
+        self.re = re.compile('^([^<]+)(<.*>)?$')
+
+    def __call__(self, val):
+        type = gdb.types.get_basic_type(val.type)
+        typename = str(type.tag)
+
+        match = self.re.match(typename)
+        if not match:
+            return None
+
+        klass = match.group(1)
+
+        if klass == 'AK::Atomic':
+            return AKAtomic(val)
+        elif klass == 'AK::DistinctNumeric':
+            return AKDistinctNumeric(val)
+        elif klass == 'AK::HashMap':
+            return AKHashMapPrettyPrinter(val)
+        elif klass == 'AK::RefCounted':
+            return AKRefCounted(val)
+        elif klass == 'AK::RefPtr':
+            return AKRefPtr(val)
+        elif klass == 'AK::OwnPtr':
+            return AKOwnPtr(val)
+        elif klass == 'AK::NonnullRefPtr':
+            return AKRefPtr(val)
+        elif klass == 'AK::String':
+            return AKString(val)
+        elif klass == 'AK::StringView':
+            return AKStringView(val)
+        elif klass == 'AK::StringImpl':
+            return AKStringImpl(val)
+        elif klass == 'AK::Vector':
+            return AKVector(val)
+        elif klass == 'VirtualAddress':
+            return VirtualAddress(val)
+
+
+gdb.printing.register_pretty_printer(None, SerenityPrettyPrinterLocator(), replace=True)
+
+
+class FindThreadCmd(gdb.Command):
+    """
+    Find SerenityOS thread for the specified TID.
+    find_thread TID
+    """
+
+    def __init__(self):
+        super(FindThreadCmd, self).__init__(
+            "find_thread", gdb.COMMAND_USER
+        )
+
+    def _find_thread(self, tid):
+        threads = gdb.parse_and_eval("Kernel::Thread::g_tid_map")
+        thread = None
+
+        def cb(key, value):
+            nonlocal thread
+            if int(key["m_value"]) == tid:
+                thread = value
+
+        AKHashMapPrettyPrinter._iter_hashmap(threads, cb)
+        return thread
+
+    def complete(self, text, word):
+        return gdb.COMPLETE_SYMBOL
+
+    def invoke(self, args, from_tty):
+        argv = gdb.string_to_argv(args)
+        if len(argv) == 0:
+            gdb.write("Argument required (TID).\n")
+            return
+        tid = int(argv[0])
+        thread = self._find_thread(tid)
+        if not thread:
+            gdb.write(f"No thread with TID {tid} found.\n")
+        else:
+            gdb.write(f"{thread}\n")
+
+
+FindThreadCmd()