linux-kernel - [PATCH] tools/nolibc: add support for fchdir()

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Message-Id: <20251107-nolibc-fchdir-v1-1-4a1ab8141f68@linutronix.de>
Date: Fri, 07 Nov 2025 15:13:38 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Willy Tarreau <w@....eu>, 
 Thomas Weißschuh <linux@...ssschuh.net>, 
 Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH] tools/nolibc: add support for fchdir()

Add support for the file descriptor based variant of chdir().

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
---
 tools/include/nolibc/sys.h                   | 13 +++++++++++++
 tools/testing/selftests/nolibc/nolibc-test.c |  2 ++
 2 files changed, 15 insertions(+)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index c5564f57deec88b8aa70291fcf6f9ca4dbc1d03f..a4b0fdb9b641230174f5e62d62762f59af81a00e 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -118,6 +118,7 @@ void *sbrk(intptr_t inc)
 
 /*
  * int chdir(const char *path);
+ * int fchdir(int fildes);
  */
 
 static __attribute__((unused))
@@ -132,6 +133,18 @@ int chdir(const char *path)
 	return __sysret(sys_chdir(path));
 }
 
+static __attribute__((unused))
+int sys_fchdir(int fildes)
+{
+	return my_syscall1(__NR_fchdir, fildes);
+}
+
+static __attribute__((unused))
+int fchdir(int fildes)
+{
+	return __sysret(sys_fchdir(fildes));
+}
+
 
 /*
  * int chmod(const char *path, mode_t mode);
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 29de21595fc95341c2aa975375a8d471cb3933fc..5927a84466cc0ede3b99611e134a8c6b8ab91e72 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -1343,6 +1343,8 @@ 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(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;
 		CASE_TEST(fork);              EXPECT_SYSZR(1, test_fork(FORK_STANDARD)); break;
 		CASE_TEST(getdents64_root);   EXPECT_SYSNE(1, test_getdents64("/"), -1); break;

---
base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
change-id: 20251107-nolibc-fchdir-2645c298a538

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@...utronix.de>