Add GDB pretty-printers for zend_string, zend_type (php#13463)

arnaud-lb · web-flow · commit 405808245984 · 2024-04-12T13:00:07.000+02:00
diff --git a/.gdb.py b/.gdb.py
@@ -0,0 +1,137 @@
+
+"""GDB support for PHP types
+
+Add this to your gdb by amending your ~/.gdbinit as follows:
+
+    source .gdb.py
+
+Use
+  (gdb) p /r any_variable
+to print |any_variable| without using any printers.
+
+To interactively type Python for development of the printers, use
+  (gdb) python foo = gdb.parse_and_eval('bar')
+to put the C value 'bar' in the current scope into a Python variable 'foo'.
+Then you can interact with that variable:
+  (gdb) python print foo['impl_']
+"""
+
+import gdb
+import re
+
+pp_set = gdb.printing.RegexpCollectionPrettyPrinter("php")
+
+class ZendStringPrettyPrinter(gdb.printing.PrettyPrinter):
+    "Print a zend_string"
+
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return self.format_string()
+
+    def children(self):
+        for field in self.val.type.fields():
+            yield (field.name, self.val[field.name])
+
+    def format_string(self):
+        len = int(self.val['len'])
+        truncated = False
+        if len > 50:
+            len = 50
+            truncated = True
+
+        ptr_type = gdb.lookup_type('char').pointer()
+        ary_type = gdb.lookup_type('char').array(len)
+        str = self.val['val'].cast(ptr_type).dereference().cast(ary_type)
+        str = str.format_string()
+        if truncated:
+            str += ' (%d bytes total)' % int(self.val['len'])
+
+        return str
+pp_set.add_printer('zend_string', '^_zend_string$', ZendStringPrettyPrinter)
+
+class ZendTypePrettyPrinter(gdb.printing.PrettyPrinter):
+    "Print a zend_type"
+
+    def __init__(self, val):
+        self.val = val
+        self.load_bits()
+
+    def to_string(self):
+        return self.format_type(self.val)
+
+    def children(self):
+        for field in self.val.type.fields():
+            yield (field.name, self.val[field.name])
+
+    def format_type(self, t):
+        type_mask = int(t['type_mask'])
+        type_mask_size = t['type_mask'].type.sizeof * 8
+        separator = '|'
+        parts = []
+        meta = []
+        for bit in range(0, type_mask_size):
+            if type_mask & (1 << bit):
+                type_name = self.bits.get(bit)
+                match type_name:
+                    case None:
+                        parts.append('(1<<%d)' % bit)
+                    case 'list':
+                        list = t['ptr'].cast(gdb.lookup_type('zend_type_list').pointer())
+                        num_types = int(list['num_types'])
+                        types = list['types'].dereference().cast(gdb.lookup_type('zend_type').array(num_types))
+                        for i in range(0, num_types):
+                            str = self.format_type(types[i])
+                            if any((c in set('|&()')) for c in str):
+                                str = '(%s)' % str
+                            parts.append(str)
+                    case 'union' | 'arena':
+                        meta.append(type_name)
+                    case 'intersection':
+                        meta.append(type_name)
+                        separator = '&'
+                    case 'name':
+                        str = t['ptr'].cast(gdb.lookup_type('zend_string').pointer())
+                        parts.append(ZendStringPrettyPrinter(str).to_string())
+                    case _:
+                        parts.append(type_name)
+
+        str = separator.join(parts)
+
+        if len(meta) > 0:
+            str = '[%s] %s' % (','.join(meta), str)
+
+        return str
+
+    def load_bits(self):
+        (symbol,_) = gdb.lookup_symbol("zend_gc_refcount")
+        if symbol == None:
+            raise "Could not find zend_types.h: symbol zend_gc_refcount not found"
+        filename = symbol.symtab.fullname()
+
+        bits = {}
+
+        with open(filename, 'r') as file:
+            content = file.read()
+
+            pattern = re.compile(r'#define _ZEND_TYPE_([^\s]+)_BIT\s+\(1u << (\d+)\)')
+            matches = pattern.findall(content)
+            for name, bit in matches:
+                bits[int(bit)] = name.lower()
+
+            pattern = re.compile(r'#define IS_([^\s]+)\s+(\d+)')
+            matches = pattern.findall(content)
+            for name, bit in matches:
+                if not int(bit) in bits:
+                    bits[int(bit)] = name.lower()
+
+        types = {}
+        for bit in bits:
+            types[bits[bit]] = bit
+
+        self.bits = bits
+        self.types = types
+pp_set.add_printer('zend_type', '^zend_type$', ZendTypePrettyPrinter)
+
+gdb.printing.register_pretty_printer(gdb, pp_set, replace=True)
