Hi Louis,
On 2025-03-02 20:25:23+0000, Louis Taylor wrote:
> openat is useful to avoid needing to construct relative paths, so expose
> a wrapper for using it directly.
Can you say what you are using nolibc for? I'm curious :-)
> Signed-off-by: Louis Taylor <louis@xxxxxxxxxx>
> ---
> tools/include/nolibc/sys.h | 29 ++++++++++++++++++++
> tools/testing/selftests/nolibc/nolibc-test.c | 22 +++++++++++++++
> 2 files changed, 51 insertions(+)
>
> diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
> index 8f44c33b1213..e5ff34df4aee 100644
> --- a/tools/include/nolibc/sys.h
> +++ b/tools/include/nolibc/sys.h
> @@ -765,6 +765,35 @@ 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)
> +{
> +#ifdef __NR_openat
> + return my_syscall4(__NR_openat, dirfd, path, flags, mode);
> +#else
> + return __nolibc_enosys(__func__, dirfd, path, flags, mode);
> +#endif
All architectures support openat(), so the #else could be dropped.
> +}
> +
> +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, int);
mode_t instead of int?
> + 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..97ded6c76f99 100644
> --- a/tools/testing/selftests/nolibc/nolibc-test.c
> +++ b/tools/testing/selftests/nolibc/nolibc-test.c
> @@ -1028,6 +1028,26 @@ int test_rlimit(void)
> return 0;
> }
>
> +int test_openat(void)
static.
> +{
> + int dev;
> + int null;
> +
> + dev = openat(AT_FDCWD, "/dev", O_DIRECTORY);
> + if (dev < 0)
> + return -1;
> +
> + null = openat(dev, "null", 0);
> + if (null < 0) {
> + close(dev);
> + return -1;
> + }
> +
> + close(dev);
> + close(null);
> +
> + return 0;
> +}
>
> /* Run syscall tests between IDs <min> and <max>.
> * Return 0 on success, non-zero on failure.
> @@ -1116,6 +1136,8 @@ 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_fdcwd); EXPECT_SYSNE(1, tmp = openat(AT_FDCWD, "/dev/null", 0), -1); if (tmp != -1) close(tmp); break;
AT_FDCWD is already used in test_openat(). What additional value does
the test above add?
> + CASE_TEST(openat_dir); EXPECT_SYSNE(1, test_openat(), -1); 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;
> --
> 2.45.2
>
