[PATCH v2 2/2] selftests/nolibc: Add a very basic test for fallocate()

[Daniel Palmer]

1: Create a tmp file, fallocate() to make it a bit bigger, check the
size is what was expected.

2: Try to fallocate() (1 << 28),

3: Try to fallocate() (1 << 60), this causes a EFBIG

Signed-off-by: Daniel Palmer <daniel@xxxxxxxxx>
---
 tools/testing/selftests/nolibc/nolibc-test.c | 58 ++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index d3c4facb54c0..6dcc2f631c3e 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -896,6 +896,63 @@ int test_getpagesize(void)
 	return !c;
 }
 
+int test_fallocate(void)
+{
+	struct stat st;
+	int fd, r;
+
+	/* Create a new tmp file */
+	fd = open("/tmp", O_TMPFILE | O_RDWR, 0644);
+	if (fd == -1)
+		return -1;
+
+	/* Expand it to 42 bytes */
+	r = fallocate(fd, 0, 0, 42);
+	if (r)
+		goto close_tmpfile;
+
+	/* Get the new stat */
+	r = fstat(fd, &st);
+	if (r)
+		goto close_tmpfile;
+
+	/* It should be 42 bytes long */
+	if (st.st_size != 42) {
+		r = -1;
+		goto close_tmpfile;
+	}
+
+	/* Now try to allocate 256MiB, this shouldn't fail
+	 */
+	r = fallocate(fd, 0, 0, (1ll << 28));
+	if (r)
+		goto close_tmpfile;
+
+	/* Check that a massive size that happens to be the
+	 * opposite endian version of the above. This should
+	 * returns an error and errno = EFBIG indicating the
+	 * value was passed correctly but the kernel rejected
+	 * it.
+	 */
+	r = fallocate(fd, 0, 0, (1ll << (28 + 32)));
+	if (r != -1) {
+		r = -1;
+		goto close_tmpfile;
+	}
+	if (errno != EFBIG) {
+		r = -1;
+		goto close_tmpfile;
+	}
+
+	/* Test passed */
+	r = 0;
+
+close_tmpfile:
+	close(fd);
+
+	return r;
+}
+
 int test_file_stream(void)
 {
 	FILE *f;
@@ -1442,6 +1499,7 @@ int run_syscall(int min, int max)
 		CASE_TEST(dup3_0);            tmp = dup3(0, 100, 0);  EXPECT_SYSNE(1, tmp, -1); close(tmp); break;
 		CASE_TEST(dup3_m1);           tmp = dup3(-1, 100, 0); EXPECT_SYSER(1, tmp, -1, EBADF); if (tmp != -1) close(tmp); break;
 		CASE_TEST(execve_root);       EXPECT_SYSER(1, execve("/", (char*[]){ [0] = "/", [1] = NULL }, NULL), -1, EACCES); break;
+		CASE_TEST(fallocate);         EXPECT_SYSZR(1, test_fallocate()); break;
 		CASE_TEST(fchdir_stdin);      EXPECT_SYSER(1, fchdir(STDIN_FILENO), -1, ENOTDIR); break;
 		CASE_TEST(fchdir_badfd);      EXPECT_SYSER(1, fchdir(-1), -1, EBADF); break;
 		CASE_TEST(file_stream);       EXPECT_SYSZR(1, test_file_stream()); break;
-- 
2.51.0