1 files changed, 158 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/lib/io.c b/tools/testing/selftests/kvm/lib/io.c
new file mode 100644
index 000000000..cff869ffe
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/io.c
@@ -0,0 +1,158 @@
+/*
+ * tools/testing/selftests/kvm/lib/io.c
+ *
+ * Copyright (C) 2018, Google LLC.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ */
+
+#include "test_util.h"
+
+/* Test Write
+ *
+ * A wrapper for write(2), that automatically handles the following
+ * special conditions:
+ *
+ *   + Interrupted system call (EINTR)
+ *   + Write of less than requested amount
+ *   + Non-block return (EAGAIN)
+ *
+ * For each of the above, an additional write is performed to automatically
+ * continue writing the requested data.
+ * There are also many cases where write(2) can return an unexpected
+ * error (e.g. EIO).  Such errors cause a TEST_ASSERT failure.
+ *
+ * Note, for function signature compatibility with write(2), this function
+ * returns the number of bytes written, but that value will always be equal
+ * to the number of requested bytes.  All other conditions in this and
+ * future enhancements to this function either automatically issue another
+ * write(2) or cause a TEST_ASSERT failure.
+ *
+ * Args:
+ *  fd    - Opened file descriptor to file to be written.
+ *  count - Number of bytes to write.
+ *
+ * Output:
+ *  buf   - Starting address of data to be written.
+ *
+ * Return:
+ *  On success, number of bytes written.
+ *  On failure, a TEST_ASSERT failure is caused.
+ */
+ssize_t test_write(int fd, const void *buf, size_t count)
+{
+	ssize_t rc;
+	ssize_t num_written = 0;
+	size_t num_left = count;
+	const char *ptr = buf;
+
+	/* Note: Count of zero is allowed (see "RETURN VALUE" portion of
+	 * write(2) manpage for details.
+	 */
+	TEST_ASSERT(count >= 0, "Unexpected count, count: %li", count);
+
+	do {
+		rc = write(fd, ptr, num_left);
+
+		switch (rc) {
+		case -1:
+			TEST_ASSERT(errno == EAGAIN || errno == EINTR,
+				    "Unexpected write failure,\n"
+				    "  rc: %zi errno: %i", rc, errno);
+			continue;
+
+		case 0:
+			TEST_ASSERT(false, "Unexpected EOF,\n"
+				    "  rc: %zi num_written: %zi num_left: %zu",
+				    rc, num_written, num_left);
+			break;
+
+		default:
+			TEST_ASSERT(rc >= 0, "Unexpected ret from write,\n"
+				"  rc: %zi errno: %i", rc, errno);
+			num_written += rc;
+			num_left -= rc;
+			ptr += rc;
+			break;
+		}
+	} while (num_written < count);
+
+	return num_written;
+}
+
+/* Test Read
+ *
+ * A wrapper for read(2), that automatically handles the following
+ * special conditions:
+ *
+ *   + Interrupted system call (EINTR)
+ *   + Read of less than requested amount
+ *   + Non-block return (EAGAIN)
+ *
+ * For each of the above, an additional read is performed to automatically
+ * continue reading the requested data.
+ * There are also many cases where read(2) can return an unexpected
+ * error (e.g. EIO).  Such errors cause a TEST_ASSERT failure.  Note,
+ * it is expected that the file opened by fd at the current file position
+ * contains at least the number of requested bytes to be read.  A TEST_ASSERT
+ * failure is produced if an End-Of-File condition occurs, before all the
+ * data is read.  It is the callers responsibility to assure that sufficient
+ * data exists.
+ *
+ * Note, for function signature compatibility with read(2), this function
+ * returns the number of bytes read, but that value will always be equal
+ * to the number of requested bytes.  All other conditions in this and
+ * future enhancements to this function either automatically issue another
+ * read(2) or cause a TEST_ASSERT failure.
+ *
+ * Args:
+ *  fd    - Opened file descriptor to file to be read.
+ *  count - Number of bytes to read.
+ *
+ * Output:
+ *  buf   - Starting address of where to write the bytes read.
+ *
+ * Return:
+ *  On success, number of bytes read.
+ *  On failure, a TEST_ASSERT failure is caused.
+ */
+ssize_t test_read(int fd, void *buf, size_t count)
+{
+	ssize_t rc;
+	ssize_t num_read = 0;
+	size_t num_left = count;
+	char *ptr = buf;
+
+	/* Note: Count of zero is allowed (see "If count is zero" portion of
+	 * read(2) manpage for details.
+	 */
+	TEST_ASSERT(count >= 0, "Unexpected count, count: %li", count);
+
+	do {
+		rc = read(fd, ptr, num_left);
+
+		switch (rc) {
+		case -1:
+			TEST_ASSERT(errno == EAGAIN || errno == EINTR,
+				    "Unexpected read failure,\n"
+				    "  rc: %zi errno: %i", rc, errno);
+			break;
+
+		case 0:
+			TEST_ASSERT(false, "Unexpected EOF,\n"
+				    "  rc: %zi num_read: %zi num_left: %zu",
+				    rc, num_read, num_left);
+			break;
+
+		default:
+			TEST_ASSERT(rc > 0, "Unexpected ret from read,\n"
+				    "  rc: %zi errno: %i", rc, errno);
+			num_read += rc;
+			num_left -= rc;
+			ptr += rc;
+			break;
+		}
+	} while (num_read < count);
+
+	return num_read;
+}