我們試圖找到一個直接通過linux內核設定時間而不需要使用用戶空間的函式。我們發現clock_settime.c檔案中有一個僅限超級用戶使用的功能：
* Copyright (C) 1991-2022 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <time.h>
#include <hurd.h>
#include <hurd/port.h>
#include <shlib-compat.h>
/* Set the current time of day.
This call is restricted to the super-user. */
int
__clock_settime (clockid_t clock_id, const struct timespec *ts)
{
error_t err;
mach_port_t hostpriv;
time_value_t tv;
if (clock_id != CLOCK_REALTIME
|| ! valid_nanoseconds (ts->tv_nsec))
return __hurd_fail (EINVAL);
err = __get_privileged_ports (&hostpriv, NULL);
if (err)
return __hurd_fail (EPERM);
TIMESPEC_TO_TIME_VALUE (&tv, ts);
err = __host_set_time (hostpriv, tv);
__mach_port_deallocate (__mach_task_self (), hostpriv);
return __hurd_fail (err);
}
libc_hidden_def (__clock_settime)
versioned_symbol (libc, __clock_settime, clock_settime, GLIBC_2_17);
/* clock_settime moved to libc in version 2.17;
old binaries may expect the symbol version it had in librt. */
#if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17)
strong_alias (__clock_settime, __clock_settime_2);
compat_symbol (libc, __clock_settime_2, clock_settime, GLIBC_2_2);
#endif
我們想遵循函式__host_set_time宣告，但任何地方都沒有庫參考，我們認為它可能是可以幫助我們解決問題的函式。有人知道它的來源和作用嗎？提前致謝。
uj5u.com熱心網友回復：
您正在查看錯誤的源代碼樹。您參考的代碼是用戶空間 GNU C 庫的一部分。此外，該代碼僅用于 Hurd 作業系統，而不是 Linux。這個 C 庫對 Linux 的 clock_settime 的實作在其中sysdeps/unix/sysv/linux/clock_settime.c，您將看到它只是呼叫了擴展為行內匯編的宏，用于系統呼叫陷阱。
您應該搜索 Linux 內核本身的源代碼，而不是 C 庫。我在https://elixir.bootlin.com/上的搜索框中輸入了“clock_settime” ，經過幾次跳躍后，我找到do_settimeofday64了我認為您正在尋找的 API。您可能還想查閱實際系統呼叫入口點的代碼，這些入口點位于kernel/time/time.c; 這些是執行安全記憶體讀取和安全檢查然后呼叫 do_settimeofday64 的包裝器。
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