1// RUN: %clang_dfsan %s -o %t && %run %t | FileCheck %s
2
3// Tests that the custom implementation of write() does writes with or without
4// a callback set using dfsan_set_write_callback().
5// REQUIRES: stable-runtime
6
7#include <sanitizer/dfsan_interface.h>
8
9#include <assert.h>
10#include <fcntl.h>
11#include <stdio.h>
12#include <string.h>
13#include <unistd.h>
14
15// Check write callback arguments by having the callback store them in
16// the following variables:
17static int last_callback_arg_fd;
18static const void *last_callback_arg_buf;
19static size_t last_callback_arg_count;
20
21// Allow tests to check the number of callbacks made by incrementing
22// this count. When callbacks are verified, the count is reset.
23static int count_unverified_callbacks = 0;
24
25// This callbact will be installed using dfsan_set_write_callback()
26// in tests below.
27static void write_callback(int fd, const void *buf, size_t count) {
28 // Do not do anything in this function that might call write().
29 count_unverified_callbacks++;
30
31 last_callback_arg_fd = fd;
32 last_callback_arg_buf = buf;
33 last_callback_arg_count = count;
34}
35
36static void write_string_to_stdout(char *string) {
37 char *cur = string;
38 int bytes_left = strlen(s: string);
39 while (bytes_left > 0) {
40 int res = write(fd: fileno(stdout), buf: cur, n: bytes_left);
41 assert (res >= 0);
42 cur += res;
43 bytes_left -= res;
44 }
45}
46
47static void test_can_write_without_callback() {
48 dfsan_set_write_callback(NULL);
49 count_unverified_callbacks = 0;
50
51 char aString[] = "Test that writes work without callback.\n";
52 // CHECK: Test that writes work without callback.
53 write_string_to_stdout(string: aString);
54
55 assert(count_unverified_callbacks == 0);
56}
57
58static void test_can_write_with_callback() {
59 dfsan_set_write_callback(labeled_write_callback: write_callback);
60
61 count_unverified_callbacks = 0;
62
63 char stringWithCallback[] = "Test that writes work with callback.\n";
64 // CHECK: Test that writes work with callback.
65 write_string_to_stdout(string: stringWithCallback);
66
67 // Data was written, so at least one call to write() was made.
68 // Because a write may not process all the bytes it is passed, there
69 // may have been several calls to write().
70 assert(count_unverified_callbacks > 0);
71 count_unverified_callbacks = 0;
72
73 dfsan_set_write_callback(NULL);
74
75 char stringWithoutCallback[] = "Writes work after the callback is removed.\n";
76 // CHECK: Writes work after the callback is removed.
77 write_string_to_stdout(string: stringWithoutCallback);
78 assert(count_unverified_callbacks == 0);
79}
80
81static void test_failing_write_runs_callback() {
82 // Open /dev/null in read-only mode. Calling write() on fd will fail.
83 int fd = open(file: "/dev/null", O_RDONLY);
84 assert(fd != -1);
85
86 // Install a callback.
87 dfsan_set_write_callback(labeled_write_callback: write_callback);
88
89 // Write to the read-only file handle. The write will fail, but the callback
90 // should still be invoked.
91 char aString[] = "This text will fail to be written.\n";
92 int len = strlen(s: aString);
93 int write_result = write(fd: fd, buf: aString, n: len);
94 assert(write_result == -1);
95
96 assert(count_unverified_callbacks == 1);
97 count_unverified_callbacks = 0;
98
99 assert(fd == last_callback_arg_fd);
100 assert(aString == last_callback_arg_buf);
101 assert(len == last_callback_arg_count);
102
103 close(fd: fd);
104}
105
106int main(int argc, char* argv[]) {
107 test_can_write_without_callback();
108 test_can_write_with_callback();
109 test_failing_write_runs_callback();
110}
111

source code of compiler-rt/test/dfsan/write_callback.c