Auto merge of rust-lang#2286 - LegNeato:patch-2, r=RalfJung

Support `gettimeofday` on more than macos

This appears to be in linux and in openbsd as well:

* https://github.com/torvalds/linux/blob/master/lib/vdso/gettimeofday.c
* https://github.com/openbsd/src/blob/master/sys/sys/time.h#L439

Note that std currently says [different syscalls are used on mac vs linux](https://doc.rust-lang.org/std/time/struct.SystemTime.html#platform-specific-behavior) but this is not part of[ std's contract](https://doc.rust-lang.org/std/io/index.html#platform-specific-behavior) and third party code could call the syscall directly on different platforms.

Author: bors

src/shims/time.rs

@@ -64,7 +64,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
     ) -> InterpResult<'tcx, i32> {
         let this = self.eval_context_mut();
 
-        this.assert_target_os("macos", "gettimeofday");
+        this.assert_target_os_is_unix("gettimeofday");
         this.check_no_isolation("`gettimeofday`")?;
 
         // Using tz is obsolete and should always be null

src/shims/unix/foreign_items.rs

@@ -139,6 +139,13 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 this.write_scalar(Scalar::from_machine_isize(result, this), dest)?;
             }
 
+            // Time related shims
+            "gettimeofday" => {
+                let [tv, tz] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
+                let result = this.gettimeofday(tv, tz)?;
+                this.write_scalar(Scalar::from_i32(result), dest)?;
+            }
+
             // Allocation
             "posix_memalign" => {
                 let [ret, align, size] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;

src/shims/unix/macos/foreign_items.rs

@@ -78,11 +78,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             }
 
             // Time related shims
-            "gettimeofday" => {
-                let [tv, tz] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
-                let result = this.gettimeofday(tv, tz)?;
-                this.write_scalar(Scalar::from_i32(result), dest)?;
-            }
             "mach_absolute_time" => {
                 let [] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let result = this.mach_absolute_time()?;

tests/pass/libc.rs

@@ -290,10 +290,32 @@ fn test_clocks() {
     assert_eq!(is_error, 0);
 }
 
+fn test_posix_gettimeofday() {
+    let mut tp = std::mem::MaybeUninit::<libc::timeval>::uninit();
+    let tz = std::ptr::null_mut::<libc::timezone>();
+    #[cfg(target_os = "macos")] // `tz` has a different type on macOS
+    let tz = tz as *mut libc::c_void;
+    let is_error = unsafe { libc::gettimeofday(tp.as_mut_ptr(), tz) };
+    assert_eq!(is_error, 0);
+    let tv = unsafe { tp.assume_init() };
+    assert!(tv.tv_sec > 0);
+    assert!(tv.tv_usec >= 0); // Theoretically this could be 0.
+
+    // Test that non-null tz returns an error.
+    let mut tz = std::mem::MaybeUninit::<libc::timezone>::uninit();
+    let tz_ptr = tz.as_mut_ptr();
+    #[cfg(target_os = "macos")] // `tz` has a different type on macOS
+    let tz_ptr = tz_ptr as *mut libc::c_void;
+    let is_error = unsafe { libc::gettimeofday(tp.as_mut_ptr(), tz_ptr) };
+    assert_eq!(is_error, -1);
+}
+
 fn main() {
     #[cfg(any(target_os = "linux", target_os = "freebsd"))]
     test_posix_fadvise();
 
+    test_posix_gettimeofday();
+
     #[cfg(any(target_os = "linux", target_os = "freebsd"))]
     test_sync_file_range();