selftests: add tests for efivarfs

This change adds a few initial efivarfs tests to the
tools/testing/selftests directory.

The open-unlink test is based on code from Lingzhu Xiang.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: Lingzhu Xiang <lxiang@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/testing/selftests/efivarfs/open-unlink.c

@@ -0,0 +1,63 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+int main(int argc, char **argv)
+{
+	const char *path;
+	char buf[5];
+	int fd, rc;
+
+	if (argc < 2) {
+		fprintf(stderr, "usage: %s <path>\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	path = argv[1];
+
+	/* attributes: EFI_VARIABLE_NON_VOLATILE |
+	 *		EFI_VARIABLE_BOOTSERVICE_ACCESS |
+	 *		EFI_VARIABLE_RUNTIME_ACCESS
+	 */
+	*(uint32_t *)buf = 0x7;
+	buf[4] = 0;
+
+	/* create a test variable */
+	fd = open(path, O_WRONLY | O_CREAT);
+	if (fd < 0) {
+		perror("open(O_WRONLY)");
+		return EXIT_FAILURE;
+	}
+
+	rc = write(fd, buf, sizeof(buf));
+	if (rc != sizeof(buf)) {
+		perror("write");
+		return EXIT_FAILURE;
+	}
+
+	close(fd);
+
+	fd = open(path, O_RDONLY);
+	if (fd < 0) {
+		perror("open");
+		return EXIT_FAILURE;
+	}
+
+	if (unlink(path) < 0) {
+		perror("unlink");
+		return EXIT_FAILURE;
+	}
+
+	rc = read(fd, buf, sizeof(buf));
+	if (rc > 0) {
+		fprintf(stderr, "reading from an unlinked variable "
+				"shouldn't be possible\n");
+		return EXIT_FAILURE;
+	}
+
+	return EXIT_SUCCESS;
+}