1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
|
# This implements the "diagnose-nsstring" command, usually installed in the debug session like
# command script import lldb.diagnose
# it is used when NSString summary formatter fails to replicate the logic that went into LLDB making the
# decisions it did and providing some useful context information that can
# be used for improving the formatter
from __future__ import print_function
import lldb
def read_memory(process, location, size):
data = ""
error = lldb.SBError()
for x in range(0, size - 1):
byte = process.ReadUnsignedFromMemory(x + location, 1, error)
if error.fail:
data = data + "err%s" % "" if x == size - 2 else ":"
else:
try:
data = data + "0x%x" % byte
if byte == 0:
data = data + "(\\0)"
elif byte == 0xa:
data = data + "(\\a)"
elif byte == 0xb:
data = data + "(\\b)"
elif byte == 0xc:
data = data + "(\\c)"
elif byte == '\n':
data = data + "(\\n)"
else:
data = data + "(%s)" % chr(byte)
if x < size - 2:
data = data + ":"
except Exception as e:
print(e)
return data
def diagnose_nsstring_Command_Impl(debugger, command, result, internal_dict):
"""
A command to diagnose the LLDB NSString data formatter
invoke as
(lldb) diagnose-nsstring <expr returning NSString>
e.g.
(lldb) diagnose-nsstring @"Hello world"
"""
target = debugger.GetSelectedTarget()
process = target.GetProcess()
thread = process.GetSelectedThread()
frame = thread.GetSelectedFrame()
if not target.IsValid() or not process.IsValid():
return "unable to get target/process - cannot proceed"
options = lldb.SBExpressionOptions()
options.SetFetchDynamicValue()
error = lldb.SBError()
if frame.IsValid():
nsstring = frame.EvaluateExpression(command, options)
else:
nsstring = target.EvaluateExpression(command, options)
print(str(nsstring), file=result)
nsstring_address = nsstring.GetValueAsUnsigned(0)
if nsstring_address == 0:
return "unable to obtain the string - cannot proceed"
expression = "\
struct $__lldb__notInlineMutable {\
char* buffer;\
signed long length;\
signed long capacity;\
unsigned int hasGap:1;\
unsigned int isFixedCapacity:1;\
unsigned int isExternalMutable:1;\
unsigned int capacityProvidedExternally:1;\n\
#if __LP64__\n\
unsigned long desiredCapacity:60;\n\
#else\n\
unsigned long desiredCapacity:28;\n\
#endif\n\
void* contentsAllocator;\
};\
\
struct $__lldb__CFString {\
void* _cfisa;\
uint8_t _cfinfo[4];\
uint32_t _rc;\
union {\
struct __inline1 {\
signed long length;\
} inline1;\
struct __notInlineImmutable1 {\
char* buffer;\
signed long length;\
void* contentsDeallocator;\
} notInlineImmutable1;\
struct __notInlineImmutable2 {\
char* buffer;\
void* contentsDeallocator;\
} notInlineImmutable2;\
struct $__lldb__notInlineMutable notInlineMutable;\
} variants;\
};\
"
expression = expression + "*(($__lldb__CFString*) %d)" % nsstring_address
# print expression
dumped = target.EvaluateExpression(expression, options)
print(str(dumped), file=result)
little_endian = (target.byte_order == lldb.eByteOrderLittle)
ptr_size = target.addr_size
info_bits = dumped.GetChildMemberWithName("_cfinfo").GetChildAtIndex(
0 if little_endian else 3).GetValueAsUnsigned(0)
is_mutable = (info_bits & 1) == 1
is_inline = (info_bits & 0x60) == 0
has_explicit_length = (info_bits & (1 | 4)) != 4
is_unicode = (info_bits & 0x10) == 0x10
is_special = (
nsstring.GetDynamicValue(
lldb.eDynamicCanRunTarget).GetTypeName() == "NSPathStore2")
has_null = (info_bits & 8) == 8
print("\nInfo=%d\nMutable=%s\nInline=%s\nExplicit=%s\nUnicode=%s\nSpecial=%s\nNull=%s\n" % \
(info_bits, "yes" if is_mutable else "no", "yes" if is_inline else "no", "yes" if has_explicit_length else "no", "yes" if is_unicode else "no", "yes" if is_special else "no", "yes" if has_null else "no"), file=result)
explicit_length_offset = 0
if not has_null and has_explicit_length and not is_special:
explicit_length_offset = 2 * ptr_size
if is_mutable and not is_inline:
explicit_length_offset = explicit_length_offset + ptr_size
elif is_inline:
pass
elif not is_inline and not is_mutable:
explicit_length_offset = explicit_length_offset + ptr_size
else:
explicit_length_offset = 0
if explicit_length_offset == 0:
print("There is no explicit length marker - skipping this step\n", file=result)
else:
explicit_length_offset = nsstring_address + explicit_length_offset
explicit_length = process.ReadUnsignedFromMemory(
explicit_length_offset, 4, error)
print("Explicit length location is at 0x%x - read value is %d\n" % (
explicit_length_offset, explicit_length), file=result)
if is_mutable:
location = 2 * ptr_size + nsstring_address
location = process.ReadPointerFromMemory(location, error)
elif is_inline and has_explicit_length and not is_unicode and not is_special and not is_mutable:
location = 3 * ptr_size + nsstring_address
elif is_unicode:
location = 2 * ptr_size + nsstring_address
if is_inline:
if not has_explicit_length:
print("Unicode & Inline & !Explicit is a new combo - no formula for it", file=result)
else:
location += ptr_size
else:
location = process.ReadPointerFromMemory(location, error)
elif is_special:
location = nsstring_address + ptr_size + 4
elif is_inline:
location = 2 * ptr_size + nsstring_address
if not has_explicit_length:
location += 1
else:
location = 2 * ptr_size + nsstring_address
location = process.ReadPointerFromMemory(location, error)
print("Expected data location: 0x%x\n" % (location), file=result)
print("1K of data around location: %s\n" % read_memory(
process, location, 1024), file=result)
print("5K of data around string pointer: %s\n" % read_memory(
process, nsstring_address, 1024 * 5), file=result)
def __lldb_init_module(debugger, internal_dict):
debugger.HandleCommand(
"command script add -f %s.diagnose_nsstring_Command_Impl diagnose-nsstring" %
__name__)
print('The "diagnose-nsstring" command has been installed, type "help diagnose-nsstring" for detailed help.')
__lldb_init_module(lldb.debugger, None)
__lldb_init_module = None
|
