selftests/efivarfs: add create-read test

Test that reads from a newly-created efivarfs file (with no data written)
will return EOF.

Signed-off-by: Jeremy Kerr <[e-mail]>
Cc: Matt Fleming <[e-mail]>
Cc: Lingzhu Xiang <[e-mail]>
Cc: Dave Young <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

tools/testing/selftests/efivarfs/Makefile

···
 CC = $(CROSS_COMPILE)gcc
 CFLAGS = -Wall
 
-test_objs = open-unlink
+test_objs = open-unlink create-read
 
 all: $(test_objs)
 

tools/testing/selftests/efivarfs/create-read.c

···
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+
+int main(int argc, char **argv)
+{
+	const char *path;
+	char buf[4];
+	int fd, rc;
+
+	if (argc < 2) {
+		fprintf(stderr, "usage: %s <path>\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	path = argv[1];
+
+	/* create a test variable */
+	fd = open(path, O_RDWR | O_CREAT, 0600);
+	if (fd < 0) {
+		perror("open(O_WRONLY)");
+		return EXIT_FAILURE;
+	}
+
+	rc = read(fd, buf, sizeof(buf));
+	if (rc != 0) {
+		fprintf(stderr, "Reading a new var should return EOF\n");
+		return EXIT_FAILURE;
+	}
+
+	return EXIT_SUCCESS;
+}

tools/testing/selftests/efivarfs/efivarfs.sh

···
 	fi
 }
 
+test_create_read()
+{
+	local file=$efivarfs_mount/$FUNCNAME-$test_guid
+	./create-read $file
+}
+
 test_delete()
 {
 	local attrs='\x07\x00\x00\x00'
···
 
 run_test test_create
 run_test test_create_empty
+run_test test_create_read
 run_test test_delete
 run_test test_zero_size_delete
 run_test test_open_unlink