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