[libc-commits] [libc] [libc][POSIX] Add clock_settime() function for Linux (PR #161729)

[Anton Shepelev via libc-commits]

================
@@ -0,0 +1,53 @@
+//===--- clock_settime linux implementation ---------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/time/clock_settime.h"
+#include "hdr/types/clockid_t.h"
+#include "hdr/types/struct_timespec.h"
+#include "src/__support/OSUtil/syscall.h"
+#include "src/__support/common.h"
+#include "src/__support/error_or.h"
+#include "src/__support/macros/config.h"
+#include <sys/syscall.h>
+
+#if defined(SYS_clock_settime64)
+#include <linux/time_types.h>
+#endif
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+ErrorOr<int> clock_settime(clockid_t clockid, const timespec *ts) {
+  int ret;
+#if defined(SYS_clock_settime)
+  ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_settime,
+                                          static_cast<long>(clockid),
+                                          reinterpret_cast<long>(ts));
+#elif defined(SYS_clock_settime64)
+  static_assert(
+      sizeof(time_t) == sizeof(int64_t),
+      "SYS_clock_settime64 requires struct timespec with 64-bit members.");
+
+  __kernel_timespec ts64{};
+
+  ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_settime64,
+                                          static_cast<long>(clockid),
+                                          reinterpret_cast<long>(&ts64));
+  if (ret == 0) {
+    ts->tv_sec = static_cast<decltype(ts->tv_sec)>(ts64.tv_sec);
+    ts->tv_nsec = static_cast<decltype(ts->tv_nsec)>(ts64.tv_nsec);
+  }
----------------
amemov wrote:

Question: shouldn't we copy values from ts into ts64 before calling doing syscall? E.g. :
```
#elif defined(SYS_clock_settime64)
    static_assert(
        sizeof(time_t) == sizeof(int64_t),
        "SYS_clock_settime64 requires struct timespec with 64-bit members.");

    __kernel_timespec ts64{};
    // Populate the 64-bit kernel structure from the user-provided timespec.
    ts64.tv_sec = static_cast<decltype(ts64.tv_sec)>(ts->tv_sec);
    ts64.tv_nsec = static_cast<decltype(ts64.tv_nsec)>(ts->tv_nsec);

    ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_settime64,
                                            static_cast<long>(clockid),
                                            reinterpret_cast<long>(&ts64));
#else
...
```

https://github.com/llvm/llvm-project/pull/161729