Add clock_gettime implementation

src/lib.rs

@@ -1,5 +1,8 @@
 #![no_std]
 
+use core::mem::MaybeUninit;
+use core::ptr;
+
 extern crate libc;
 
 /// Call this somewhere to force Rust to link this module.
@@ -8,6 +11,11 @@ extern crate libc;
 /// See https://github.com/rust-lang/rust/issues/47384
 pub fn init() {}
 
+extern "C" {
+    // Not provided by libc: https://github.com/rust-lang/libc/issues/1995
+    fn __errno() -> *mut libc::c_int;
+}
+
 #[no_mangle]
 extern "C" fn posix_memalign(
     memptr: *mut *mut libc::c_void,
@@ -36,3 +44,26 @@ unsafe extern "C" fn realpath(
 
     resolved_path
 }
+
+#[no_mangle]
+unsafe extern "C" fn clock_gettime(
+    clock_id: libc::clockid_t,
+    tp: *mut libc::timespec,
+) -> libc::c_int {
+    let mut retval = -1;
+    match clock_id {
+        libc::CLOCK_REALTIME => {
+            let mut tv = MaybeUninit::uninit();
+
+            retval = libc::gettimeofday(tv.as_mut_ptr(), ptr::null_mut());
+            if retval == 0 {
+                let tv = tv.assume_init();
+                (*tp).tv_nsec = (tv.tv_usec * 1000).into();
+                (*tp).tv_sec = tv.tv_sec;
+            }
+        }
+        _ => *__errno() = libc::EINVAL,
+    }
+
+    retval
+}