[4/5] test: Add renameat2 test cases

diff --git a/test/test-renameat2-chroot.sh b/test/test-renameat2-chroot.sh
new file mode 100755
index 0000000..3e44033
--- /dev/null
+++ b/test/test-renameat2-chroot.sh
@@ -0,0 +1,11 @@ 
+#! /bin/sh
+
+# Run with and without ignored paths, matching test-openat coverage.
+
+chroot ./test ./test-renameat2
+rc=$?
+if [ "$rc" -ne 0 ]; then
+	exit "$rc"
+fi
+
+PSEUDO_IGNORE_PATHS=/ chroot ./test ./test-renameat2
diff --git a/test/test-renameat2.c b/test/test-renameat2.c
new file mode 100644
index 0000000..286045f
--- /dev/null
+++ b/test/test-renameat2.c
@@ -0,0 +1,263 @@ 
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#ifndef RENAME_NOREPLACE
+#define RENAME_NOREPLACE (1 << 0)
+#endif
+#ifndef RENAME_EXCHANGE
+#define RENAME_EXCHANGE (1 << 1)
+#endif
+
+static int do_renameat2(int olddirfd, const char *oldpath,
+			int newdirfd, const char *newpath,
+			unsigned int flags) {
+#ifdef SYS_renameat2
+	return syscall(SYS_renameat2, olddirfd, oldpath, newdirfd, newpath, flags);
+#else
+	errno = ENOSYS;
+	return -1;
+#endif
+}
+
+static int touch_file(const char *path) {
+	int fd = open(path, O_CREAT | O_WRONLY | O_TRUNC, 0644);
+	if (fd == -1) {
+		perror("open");
+		return -1;
+	}
+	if (write(fd, "x", 1) != 1) {
+		perror("write");
+		close(fd);
+		return -1;
+	}
+	if (close(fd) == -1) {
+		perror("close");
+		return -1;
+	}
+	return 0;
+}
+
+static int file_exists(int dirfd, const char *name) {
+	struct stat st;
+	return fstatat(dirfd, name, &st, AT_SYMLINK_NOFOLLOW) == 0;
+}
+
+int main(void) {
+	char template[] = "test-renameat2.XXXXXX";
+	char *base;
+	int dirfd = -1;
+	int rc = 1;
+	int ret;
+	int renameat2_works = 1;
+
+	base = mkdtemp(template);
+	if (!base) {
+		perror("mkdtemp");
+		return 1;
+	}
+
+	if (chdir(base) == -1) {
+		perror("chdir to base");
+		rmdir(base);
+		return 1;
+	}
+
+	dirfd = open(".", O_RDONLY | O_DIRECTORY);
+	if (dirfd == -1) {
+		perror("open base dir");
+		goto out;
+	}
+
+	/* ---------------------------------------------------------- */
+	/* Part 1: renameat (classic) semantics via dirfd             */
+	/* ---------------------------------------------------------- */
+
+	if (touch_file("fileA") == -1)
+		goto out_in_base;
+
+	/* Rename fileA -> fileB using renameat with dirfd */
+	if (renameat(AT_FDCWD, "fileA", AT_FDCWD, "fileB") == -1) {
+		perror("renameat fileA -> fileB");
+		goto out_in_base;
+	}
+	if (file_exists(AT_FDCWD, "fileA")) {
+		fprintf(stderr, "renameat: source still exists after rename\n");
+		goto out_in_base;
+	}
+	if (!file_exists(AT_FDCWD, "fileB")) {
+		fprintf(stderr, "renameat: destination missing after rename\n");
+		goto out_in_base;
+	}
+	unlink("fileB");
+
+	/* Same test but with actual dirfd instead of AT_FDCWD */
+	if (touch_file("fileC") == -1)
+		goto out_in_base;
+
+	if (renameat(dirfd, "fileC", dirfd, "fileD") == -1) {
+		perror("renameat dirfd fileC -> fileD");
+		goto out_in_base;
+	}
+	if (file_exists(dirfd, "fileC")) {
+		fprintf(stderr, "renameat dirfd: source still exists\n");
+		goto out_in_base;
+	}
+	if (!file_exists(dirfd, "fileD")) {
+		fprintf(stderr, "renameat dirfd: destination missing\n");
+		goto out_in_base;
+	}
+	unlinkat(dirfd, "fileD", 0);
+
+	/* ---------------------------------------------------------- */
+	/* Part 2: renameat2 with flags=0 (should match renameat)     */
+	/* ---------------------------------------------------------- */
+
+	if (touch_file("fileE") == -1)
+		goto out_in_base;
+
+	ret = do_renameat2(AT_FDCWD, "fileE", AT_FDCWD, "fileF", 0);
+	if (ret == -1) {
+		if (errno == ENOSYS) {
+			/* renameat2 not available (kernel too old or pseudo stub) */
+			renameat2_works = 0;
+			unlink("fileE");
+		} else {
+			perror("renameat2 flags=0 fileE -> fileF");
+			goto out_in_base;
+		}
+	} else {
+		if (file_exists(AT_FDCWD, "fileE")) {
+			fprintf(stderr, "renameat2 flags=0: source still exists\n");
+			goto out_in_base;
+		}
+		if (!file_exists(AT_FDCWD, "fileF")) {
+			fprintf(stderr, "renameat2 flags=0: destination missing\n");
+			goto out_in_base;
+		}
+		unlink("fileF");
+	}
+
+	if (!renameat2_works) {
+		/* renameat2 returned ENOSYS; skip the remaining renameat2-specific tests */
+		rc = 0;
+		goto out;
+	}
+
+	/* ---------------------------------------------------------- */
+	/* Part 3: RENAME_NOREPLACE — must fail when target exists    */
+	/* ---------------------------------------------------------- */
+
+	if (touch_file("src_noreplace") == -1)
+		goto out_in_base;
+	if (touch_file("dst_noreplace") == -1)
+		goto out_in_base;
+
+	ret = do_renameat2(AT_FDCWD, "src_noreplace",
+			   AT_FDCWD, "dst_noreplace", RENAME_NOREPLACE);
+	if (ret != -1) {
+		fprintf(stderr, "RENAME_NOREPLACE: should have failed when target exists\n");
+		goto out_in_base;
+	}
+	if (errno != EEXIST) {
+		fprintf(stderr, "RENAME_NOREPLACE: expected EEXIST, got %s\n",
+			strerror(errno));
+		goto out_in_base;
+	}
+	/* Both files must still exist */
+	if (!file_exists(AT_FDCWD, "src_noreplace") ||
+	    !file_exists(AT_FDCWD, "dst_noreplace")) {
+		fprintf(stderr, "RENAME_NOREPLACE: files disappeared\n");
+		goto out_in_base;
+	}
+
+	/* Positive case: RENAME_NOREPLACE succeeds when target does not exist */
+	unlink("dst_noreplace");
+	ret = do_renameat2(AT_FDCWD, "src_noreplace",
+			   AT_FDCWD, "dst_noreplace", RENAME_NOREPLACE);
+	if (ret == -1) {
+		perror("RENAME_NOREPLACE (no target)");
+		goto out_in_base;
+	}
+	if (file_exists(AT_FDCWD, "src_noreplace")) {
+		fprintf(stderr, "RENAME_NOREPLACE: source still exists\n");
+		goto out_in_base;
+	}
+	if (!file_exists(AT_FDCWD, "dst_noreplace")) {
+		fprintf(stderr, "RENAME_NOREPLACE: destination missing\n");
+		goto out_in_base;
+	}
+	unlink("dst_noreplace");
+
+	/* ---------------------------------------------------------- */
+	/* Part 4: RENAME_EXCHANGE — atomically swap two paths        */
+	/* ---------------------------------------------------------- */
+
+	if (touch_file("swap_a") == -1)
+		goto out_in_base;
+	if (touch_file("swap_b") == -1)
+		goto out_in_base;
+
+	/* Write distinct content so we can verify the swap */
+	{
+		struct stat sa, sb;
+		ino_t ino_a, ino_b;
+
+		if (stat("swap_a", &sa) == -1 || stat("swap_b", &sb) == -1) {
+			perror("stat before exchange");
+			goto out_in_base;
+		}
+		ino_a = sa.st_ino;
+		ino_b = sb.st_ino;
+
+		ret = do_renameat2(AT_FDCWD, "swap_a",
+				   AT_FDCWD, "swap_b", RENAME_EXCHANGE);
+		if (ret == -1) {
+			perror("RENAME_EXCHANGE");
+			goto out_in_base;
+		}
+
+		if (stat("swap_a", &sa) == -1 || stat("swap_b", &sb) == -1) {
+			perror("stat after exchange");
+			goto out_in_base;
+		}
+
+		/* After exchange, inodes should be swapped */
+		if (sa.st_ino != ino_b || sb.st_ino != ino_a) {
+			fprintf(stderr, "RENAME_EXCHANGE: inodes not swapped "
+				"(a: %lu->%lu, b: %lu->%lu)\n",
+				(unsigned long) ino_a, (unsigned long) sa.st_ino,
+				(unsigned long) ino_b, (unsigned long) sb.st_ino);
+			goto out_in_base;
+		}
+	}
+	unlink("swap_a");
+	unlink("swap_b");
+
+	rc = 0;
+	goto out;
+
+out_in_base:
+	/* Best-effort cleanup of any leftover files inside the temp dir */
+	unlink("fileA"); unlink("fileB"); unlink("fileC"); unlink("fileD");
+	unlink("fileE"); unlink("fileF");
+	unlink("src_noreplace"); unlink("dst_noreplace");
+	unlink("swap_a"); unlink("swap_b");
+
+out:
+	if (dirfd != -1)
+		close(dirfd);
+	if (chdir("..") == 0)
+		rmdir(base);
+
+	return rc;
+}
diff --git a/test/test-renameat2.sh b/test/test-renameat2.sh
new file mode 100755
index 0000000..6aa7fbc
--- /dev/null
+++ b/test/test-renameat2.sh
@@ -0,0 +1,11 @@ 
+#! /bin/sh
+
+# Run with and without ignored paths, matching test-openat coverage.
+
+./test/test-renameat2
+rc=$?
+if [ "$rc" -ne 0 ]; then
+	exit "$rc"
+fi
+
+PSEUDO_IGNORE_PATHS=/ ./test/test-renameat2