1 /*
2 * tools/testing/selftests/kvm/lib/io.c
3 *
4 * Copyright (C) 2018, Google LLC.
5 *
6 * This work is licensed under the terms of the GNU GPL, version 2.
7 */
8
9 #include "test_util.h"
10
11 /* Test Write
12 *
13 * A wrapper for write(2), that automatically handles the following
14 * special conditions:
15 *
16 * + Interrupted system call (EINTR)
17 * + Write of less than requested amount
18 * + Non-block return (EAGAIN)
19 *
20 * For each of the above, an additional write is performed to automatically
21 * continue writing the requested data.
22 * There are also many cases where write(2) can return an unexpected
23 * error (e.g. EIO). Such errors cause a TEST_ASSERT failure.
24 *
25 * Note, for function signature compatibility with write(2), this function
26 * returns the number of bytes written, but that value will always be equal
27 * to the number of requested bytes. All other conditions in this and
28 * future enhancements to this function either automatically issue another
29 * write(2) or cause a TEST_ASSERT failure.
30 *
31 * Args:
32 * fd - Opened file descriptor to file to be written.
33 * count - Number of bytes to write.
34 *
35 * Output:
36 * buf - Starting address of data to be written.
37 *
38 * Return:
39 * On success, number of bytes written.
40 * On failure, a TEST_ASSERT failure is caused.
41 */
test_write(int fd,const void * buf,size_t count)42 ssize_t test_write(int fd, const void *buf, size_t count)
43 {
44 ssize_t rc;
45 ssize_t num_written = 0;
46 size_t num_left = count;
47 const char *ptr = buf;
48
49 /* Note: Count of zero is allowed (see "RETURN VALUE" portion of
50 * write(2) manpage for details.
51 */
52 TEST_ASSERT(count >= 0, "Unexpected count, count: %li", count);
53
54 do {
55 rc = write(fd, ptr, num_left);
56
57 switch (rc) {
58 case -1:
59 TEST_ASSERT(errno == EAGAIN || errno == EINTR,
60 "Unexpected write failure,\n"
61 " rc: %zi errno: %i", rc, errno);
62 continue;
63
64 case 0:
65 TEST_ASSERT(false, "Unexpected EOF,\n"
66 " rc: %zi num_written: %zi num_left: %zu",
67 rc, num_written, num_left);
68 break;
69
70 default:
71 TEST_ASSERT(rc >= 0, "Unexpected ret from write,\n"
72 " rc: %zi errno: %i", rc, errno);
73 num_written += rc;
74 num_left -= rc;
75 ptr += rc;
76 break;
77 }
78 } while (num_written < count);
79
80 return num_written;
81 }
82
83 /* Test Read
84 *
85 * A wrapper for read(2), that automatically handles the following
86 * special conditions:
87 *
88 * + Interrupted system call (EINTR)
89 * + Read of less than requested amount
90 * + Non-block return (EAGAIN)
91 *
92 * For each of the above, an additional read is performed to automatically
93 * continue reading the requested data.
94 * There are also many cases where read(2) can return an unexpected
95 * error (e.g. EIO). Such errors cause a TEST_ASSERT failure. Note,
96 * it is expected that the file opened by fd at the current file position
97 * contains at least the number of requested bytes to be read. A TEST_ASSERT
98 * failure is produced if an End-Of-File condition occurs, before all the
99 * data is read. It is the callers responsibility to assure that sufficient
100 * data exists.
101 *
102 * Note, for function signature compatibility with read(2), this function
103 * returns the number of bytes read, but that value will always be equal
104 * to the number of requested bytes. All other conditions in this and
105 * future enhancements to this function either automatically issue another
106 * read(2) or cause a TEST_ASSERT failure.
107 *
108 * Args:
109 * fd - Opened file descriptor to file to be read.
110 * count - Number of bytes to read.
111 *
112 * Output:
113 * buf - Starting address of where to write the bytes read.
114 *
115 * Return:
116 * On success, number of bytes read.
117 * On failure, a TEST_ASSERT failure is caused.
118 */
test_read(int fd,void * buf,size_t count)119 ssize_t test_read(int fd, void *buf, size_t count)
120 {
121 ssize_t rc;
122 ssize_t num_read = 0;
123 size_t num_left = count;
124 char *ptr = buf;
125
126 /* Note: Count of zero is allowed (see "If count is zero" portion of
127 * read(2) manpage for details.
128 */
129 TEST_ASSERT(count >= 0, "Unexpected count, count: %li", count);
130
131 do {
132 rc = read(fd, ptr, num_left);
133
134 switch (rc) {
135 case -1:
136 TEST_ASSERT(errno == EAGAIN || errno == EINTR,
137 "Unexpected read failure,\n"
138 " rc: %zi errno: %i", rc, errno);
139 break;
140
141 case 0:
142 TEST_ASSERT(false, "Unexpected EOF,\n"
143 " rc: %zi num_read: %zi num_left: %zu",
144 rc, num_read, num_left);
145 break;
146
147 default:
148 TEST_ASSERT(rc > 0, "Unexpected ret from read,\n"
149 " rc: %zi errno: %i", rc, errno);
150 num_read += rc;
151 num_left -= rc;
152 ptr += rc;
153 break;
154 }
155 } while (num_read < count);
156
157 return num_read;
158 }
159
