[PATCH v6 08/11] kunit: uapi: Forward test executable output to KUnit log

["Thomas Weißschuh" <thomas.weissschuh@linutronix.de>]

The output of the test executable should be grouped together with the
regular KUnit output and also be available in debugfs.
Install a custom miscdevice as stdout and stderr which forwards the
written data to the KUnit log.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
 lib/kunit/kunit-uapi.c | 155 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 154 insertions(+), 1 deletion(-)

diff --git a/lib/kunit/kunit-uapi.c b/lib/kunit/kunit-uapi.c
index 485b79fd193d..7f0309a827a5 100644
--- a/lib/kunit/kunit-uapi.c
+++ b/lib/kunit/kunit-uapi.c
@@ -11,6 +11,7 @@
 #include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/fs_struct.h>
+#include <linux/miscdevice.h>
 #include <linux/pid.h>
 #include <linux/pipe_fs_i.h>
 #include <linux/sched/task.h>
@@ -22,6 +23,8 @@
 #include <kunit/test.h>
 #include <kunit/uapi.h>
 
+#define KUNIT_LOG_DEVICE "kunit-log"
+
 enum {
 	KSFT_PASS	= 0,
 	KSFT_FAIL	= 1,
@@ -94,10 +97,48 @@ static int kunit_uapi_get_cwd(struct vfsmount *mnt)
 	return take_fd(fd);
 }
 
+static int kunit_uapi_open_standard_streams(void)
+{
+	struct vfsmount *devtmpfs __free(kern_unmount) = kunit_uapi_mount_fs("devtmpfs");
+	if (IS_ERR(devtmpfs))
+		return PTR_ERR(devtmpfs);
+
+	CLASS(get_unused_fd, stdin_fd)(O_RDONLY);
+	if (stdin_fd < 0)
+		return stdin_fd;
+
+	CLASS(get_unused_fd, stdout_fd)(O_WRONLY);
+	if (stdout_fd < 0)
+		return stdout_fd;
+
+	CLASS(get_unused_fd, stderr_fd)(O_WRONLY);
+	if (stderr_fd < 0)
+		return stderr_fd;
+
+	struct file *logfile __free(fput) = file_open_root_mnt(devtmpfs, KUNIT_LOG_DEVICE,
+							       O_RDWR, 0);
+	if (IS_ERR(logfile))
+		return PTR_ERR(logfile);
+
+	fd_install(stdin_fd, no_free_ptr(logfile));
+	fd_install(stdout_fd, fget(stdin_fd));
+	fd_install(stderr_fd, fget(stdin_fd));
+
+	take_fd(stdin_fd);
+	take_fd(stdout_fd);
+	take_fd(stderr_fd);
+
+	return 0;
+}
+
 static int kunit_uapi_usermodehelper_init(struct subprocess_info *info, struct cred *new)
 {
 	struct kunit_uapi_usermodehelper_ctx *ctx = info->data;
-	int dirfd;
+	int ret, dirfd;
+
+	ret = kunit_uapi_open_standard_streams();
+	if (ret)
+		return ret;
 
 	dirfd = kunit_uapi_get_cwd(ctx->mnt);
 	if (dirfd < 0)
@@ -188,6 +229,118 @@ void kunit_uapi_run_kselftest(struct kunit *test, const struct kunit_uapi_blob *
 }
 EXPORT_SYMBOL_GPL(kunit_uapi_run_kselftest);
 
+struct kunit_uapi_log_private {
+	struct mutex mutex;
+	struct seq_buf buf;
+	char data[4096];
+};
+
+static int kunit_uapi_log_open(struct inode *ino, struct file *file)
+{
+	struct kunit_uapi_log_private *priv;
+
+	priv = kmalloc_obj(*priv);
+	if (!priv)
+		return -ENOMEM;
+
+	mutex_init(&priv->mutex);
+	seq_buf_init(&priv->buf, priv->data, sizeof(priv->data));
+
+	file->private_data = priv;
+
+	return 0;
+}
+
+static void kunit_uapi_log_str(struct kunit *test, const char *str, size_t len)
+{
+	kunit_log(KERN_INFO, test, KUNIT_SUBSUBTEST_INDENT "%.*s", (int)len, str);
+}
+
+static void kunit_uapi_print_buf_to_log(struct kunit *test, struct seq_buf *s)
+{
+	const char *start, *lf;
+
+	if (s->size == 0 || s->len == 0)
+		return;
+
+	start = seq_buf_str(s);
+	while ((lf = strchr(start, '\n'))) {
+		kunit_uapi_log_str(test, start, lf - start + 1);
+		start = ++lf;
+	}
+
+	/* Remove printed data from buffer */
+	memmove(s->buffer, start, start - s->buffer);
+	s->len -= start - s->buffer;
+}
+
+static ssize_t kunit_uapi_log_write(struct file *file, const char __user *ubuf, size_t count,
+				    loff_t *off)
+{
+	struct kunit_uapi_log_private *priv = file->private_data;
+	struct seq_buf *buf = &priv->buf;
+	struct kunit *test;
+
+	test = kunit_get_current_test();
+	if (!test)
+		return -ENODEV;
+
+	guard(mutex)(&priv->mutex);
+
+	if (seq_buf_has_overflowed(buf))
+		return -E2BIG;
+
+	if (buf->size < buf->len + count) {
+		seq_buf_set_overflow(buf);
+		kunit_warn(test, "KUnit UAPI line buffer has overflowed\n");
+		return -E2BIG;
+	}
+
+	if (copy_from_user(buf->buffer + buf->len, ubuf, count))
+		return -EFAULT;
+
+	buf->len += count;
+
+	kunit_uapi_print_buf_to_log(test, &priv->buf);
+
+	return count;
+}
+
+static int kunit_uapi_log_release(struct inode *ino, struct file *file)
+{
+	struct kunit_uapi_log_private *priv = file->private_data;
+	struct kunit *test;
+
+	mutex_destroy(&priv->mutex);
+
+	test = kunit_get_current_test();
+	if (!test) {
+		kfree(priv);
+		return -ENODEV;
+	}
+
+	/* Flush last partial line */
+	kunit_uapi_log_str(test, priv->buf.buffer, priv->buf.len);
+	kunit_uapi_log_str(test, "\n", 1);
+
+	kfree(priv);
+	return 0;
+}
+
+static const struct file_operations kunit_uapi_log_fops = {
+	.owner		= THIS_MODULE,
+	.open		= kunit_uapi_log_open,
+	.release	= kunit_uapi_log_release,
+	.write		= kunit_uapi_log_write,
+};
+
+static struct miscdevice kunit_uapi_log = {
+	.minor	= MISC_DYNAMIC_MINOR,
+	.name	= KUNIT_LOG_DEVICE,
+	.fops	= &kunit_uapi_log_fops,
+};
+module_misc_device(kunit_uapi_log);
+
 MODULE_DESCRIPTION("KUnit UAPI testing framework");
 MODULE_AUTHOR("Thomas Weißschuh <thomas.weissschuh@linutronix.de");
 MODULE_LICENSE("GPL");

-- 
2.53.0