1 // RUN: %clang_asan -O2 %s -o %t
2 // RUN: %run %t 2>&1 | FileCheck --check-prefix=CHECK-NOSCRIBBLE %s
3 // RUN: %env MallocScribble=1 MallocPreScribble=1 %run %t 2>&1 | FileCheck --check-prefix=CHECK-SCRIBBLE %s
4 // RUN: %env_asan_opts=max_free_fill_size=4096 %run %t 2>&1 | FileCheck --check-prefix=CHECK-SCRIBBLE %s
5 
6 #include <stdint.h>
7 #include <stdio.h>
8 #include <stdlib.h>
9 #include <string.h>
10 
11 struct Isa {
12   const char *class_name;
13 };
14 
15 struct MyClass {
16   // User memory and `ChunkHeader` overlap. In particular the `free_context_id`
17   // is stored at the beginning of user memory when it is freed. That part of
18   // user memory is not scribbled and is changed when the memory is freed. This
19   // test relies on `isa` being scribbled or unmodified after memory is freed.
20   // In order for this to work the start of `isa` must come after whatever is in
21   // `ChunkHeader` (currently the 64-bit `free_context_id`). The padding here is
22   // to ensure this is the case.
23   uint64_t padding;
24   Isa *isa;
25   long data;
26 
27   void print_my_class_name();
28 };
29 
30 __attribute__((no_sanitize("address")))
31 void MyClass::print_my_class_name() {
32   fprintf(stderr, "this = %p\n", this);
33   fprintf(stderr, "padding = 0x%lx\n", this->padding);
34   fprintf(stderr, "isa = %p\n", this->isa);
35 
36   if ((uint32_t)(uintptr_t)this->isa != 0x55555555) {
37     fprintf(stderr, "class name: %s\n", this->isa->class_name);
38   }
39 }
40 
41 int main() {
42   Isa *my_class_isa = (Isa *)malloc(sizeof(Isa));
43   memset(my_class_isa, 0x77, sizeof(Isa));
44   my_class_isa->class_name = "MyClass";
45 
46   MyClass *my_object = (MyClass *)malloc(sizeof(MyClass));
47   memset(my_object, 0x88, sizeof(MyClass));
48   my_object->isa = my_class_isa;
49   my_object->data = 42;
50 
51   my_object->print_my_class_name();
52   // CHECK-SCRIBBLE: class name: MyClass
53   // CHECK-NOSCRIBBLE: class name: MyClass
54 
55   free(my_object);
56 
57   my_object->print_my_class_name();
58   // CHECK-NOSCRIBBLE: class name: MyClass
59   // CHECK-SCRIBBLE: isa = {{(0x)?}}{{5555555555555555|55555555}}
60 
61   fprintf(stderr, "okthxbai!\n");
62   // CHECK-SCRIBBLE: okthxbai!
63   // CHECK-NOSCRIBBLE: okthxbai!
64   free(my_class_isa);
65 }
66