[v3,1/5] tools/nolibc: add support for openat(2)

Commit Message

Louis Taylor March 6, 2025, 6:41 p.m. UTC

openat is useful to avoid needing to construct relative paths, so expose
a wrapper for using it directly.

Signed-off-by: Louis Taylor <[e-mail]>
---
 tools/include/nolibc/sys.h                   | 25 ++++++++++++++++++++
 tools/testing/selftests/nolibc/nolibc-test.c | 17 +++++++++++++
 2 files changed, 42 insertions(+)

Comments

Thomas Weißschuh March 6, 2025, 9:30 p.m. UTC | #1

On Thu, 06 Mar 2025 18:41:18 +0000, Louis Taylor wrote:
> openat is useful to avoid needing to construct relative paths, so expose
> a wrapper for using it directly.
> 
> 

Applied, thanks!

[1/5] tools/nolibc: add support for openat(2)
      commit: b2edaad7f5192a79384b7d0bec62312b668da463
[2/5] tools/nolibc: always use openat(2) instead of open(2)
      commit: fbd4f52f5bf76e6ef63d7ebee16d404c6c8cfebb
[3/5] tools/nolibc: process open() vararg as mode_t
      commit: 90e1f9f7440cba79716a9d5b0c9df2ce6a661197
[4/5] tools/nolibc: drop outdated example from overview comment
      commit: 00e03fea969efd46b104acd271e7f7e08e7c23bf
[5/5] selftests/nolibc: use O_RDONLY flag instead of 0
      commit: 6e406202a44a1a37176da0333cec10d5320c4b33

Best regards,

Patch

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index 8f44c33b1213..3cd938f9abda 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -765,6 +765,31 @@  int mount(const char *src, const char *tgt,
 	return __sysret(sys_mount(src, tgt, fst, flags, data));
 }
 
+/*
+ * int openat(int dirfd, const char *path, int flags[, mode_t mode]);
+ */
+
+static __attribute__((unused))
+int sys_openat(int dirfd, const char *path, int flags, mode_t mode)
+{
+	return my_syscall4(__NR_openat, dirfd, path, flags, mode);
+}
+
+static __attribute__((unused))
+int openat(int dirfd, const char *path, int flags, ...)
+{
+	mode_t mode = 0;
+
+	if (flags & O_CREAT) {
+		va_list args;
+
+		va_start(args, flags);
+		mode = va_arg(args, mode_t);
+		va_end(args);
+	}
+
+	return __sysret(sys_openat(dirfd, path, flags, mode));
+}
 
 /*
  * int open(const char *path, int flags[, mode_t mode]);
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 79c3e6a845f3..e8faddcecf9d 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -1028,6 +1028,22 @@  int test_rlimit(void)
 	return 0;
 }
 
+int test_openat(void)
+{
+	int dev, null;
+
+	dev = openat(AT_FDCWD, "/dev", O_DIRECTORY);
+	if (dev < 0)
+		return -1;
+
+	null = openat(dev, "null", O_RDONLY);
+	close(dev);
+	if (null < 0)
+		return -1;
+
+	close(null);
+	return 0;
+}
 
 /* Run syscall tests between IDs <min> and <max>.
  * Return 0 on success, non-zero on failure.
@@ -1116,6 +1132,7 @@  int run_syscall(int min, int max)
 		CASE_TEST(mmap_munmap_good);  EXPECT_SYSZR(1, test_mmap_munmap()); break;
 		CASE_TEST(open_tty);          EXPECT_SYSNE(1, tmp = open("/dev/null", 0), -1); if (tmp != -1) close(tmp); break;
 		CASE_TEST(open_blah);         EXPECT_SYSER(1, tmp = open("/proc/self/blah", 0), -1, ENOENT); if (tmp != -1) close(tmp); break;
+		CASE_TEST(openat_dir);        EXPECT_SYSZR(1, test_openat()); break;
 		CASE_TEST(pipe);              EXPECT_SYSZR(1, test_pipe()); break;
 		CASE_TEST(poll_null);         EXPECT_SYSZR(1, poll(NULL, 0, 0)); break;
 		CASE_TEST(poll_stdout);       EXPECT_SYSNE(1, ({ struct pollfd fds = { 1, POLLOUT, 0}; poll(&fds, 1, 0); }), -1); break;