std: sys: pal: uefi: tests: Add systemtime tests

Add tests to ensure that extream system times are still representable.

Signed-off-by: Ayush Singh <[email protected]>

Author: Ayush1325

library/std/src/sys/pal/uefi/tests.rs

@@ -1,4 +1,8 @@
 use super::alloc::*;
+use super::time::system_time_internal::{from_uefi, to_uefi};
+use crate::time::Duration;
+
+const SECS_IN_MINUTE: u64 = 60;
 
 #[test]
 fn align() {
@@ -19,3 +23,62 @@ fn align() {
         }
     }
 }
+
+#[test]
+fn systemtime_start() {
+    let t = r_efi::efi::Time {
+        year: 1900,
+        month: 1,
+        day: 1,
+        hour: 0,
+        minute: 0,
+        second: 0,
+        pad1: 0,
+        nanosecond: 0,
+        timezone: -1440,
+        daylight: 0,
+        pad2: 0,
+    };
+    assert_eq!(from_uefi(&t), Duration::new(0, 0));
+    assert_eq!(t, to_uefi(&from_uefi(&t), -1440, 0).unwrap());
+    assert!(to_uefi(&from_uefi(&t), 0, 0).is_none());
+}
+
+#[test]
+fn systemtime_utc_start() {
+    let t = r_efi::efi::Time {
+        year: 1900,
+        month: 1,
+        day: 1,
+        hour: 0,
+        minute: 0,
+        second: 0,
+        pad1: 0,
+        nanosecond: 0,
+        timezone: 0,
+        daylight: 0,
+        pad2: 0,
+    };
+    assert_eq!(from_uefi(&t), Duration::new(1440 * SECS_IN_MINUTE, 0));
+    assert_eq!(t, to_uefi(&from_uefi(&t), 0, 0).unwrap());
+    assert!(to_uefi(&from_uefi(&t), -1440, 0).is_some());
+}
+
+#[test]
+fn systemtime_end() {
+    let t = r_efi::efi::Time {
+        year: 9999,
+        month: 12,
+        day: 31,
+        hour: 23,
+        minute: 59,
+        second: 59,
+        pad1: 0,
+        nanosecond: 0,
+        timezone: 1440,
+        daylight: 0,
+        pad2: 0,
+    };
+    assert!(to_uefi(&from_uefi(&t), 1440, 0).is_some());
+    assert!(to_uefi(&from_uefi(&t), 1439, 0).is_none());
+}

library/std/src/sys/pal/uefi/time.rs

@@ -6,7 +6,7 @@ pub struct Instant(Duration);
 /// When a Timezone is specified, the stored Duration is in UTC. If timezone is unspecified, then
 /// the timezone is assumed to be in UTC.
 ///
-/// UEFI SystemTime is stored as Duration from 1900-01-01-00:00:00
+/// UEFI SystemTime is stored as Duration from 1900-01-01-00:00:00 with timezone -1440 as anchor
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
 pub struct SystemTime(Duration);
 
@@ -24,6 +24,20 @@ pub const UNIX_EPOCH: SystemTime = SystemTime::from_uefi(r_efi::efi::Time {
     pad2: 0,
 });
 
+const MAX_UEFI_TIME: SystemTime = SystemTime::from_uefi(r_efi::efi::Time {
+    year: 9999,
+    month: 12,
+    day: 31,
+    hour: 23,
+    minute: 59,
+    second: 59,
+    nanosecond: 999_999_999,
+    timezone: 1440,
+    daylight: 0,
+    pad1: 0,
+    pad2: 0,
+});
+
 impl Instant {
     pub fn now() -> Instant {
         // If we have a timestamp protocol, use it.
@@ -56,6 +70,7 @@ impl SystemTime {
         Self(system_time_internal::from_uefi(&t))
     }
 
+    #[expect(dead_code)]
     pub(crate) const fn to_uefi(self, timezone: i16, daylight: u8) -> Option<r_efi::efi::Time> {
         system_time_internal::to_uefi(&self.0, timezone, daylight)
     }
@@ -73,14 +88,11 @@ impl SystemTime {
         let temp = Self(self.0.checked_add(*other)?);
 
         // Check if can be represented in UEFI
-        if temp.to_uefi(0, 0).is_some() { Some(temp) } else { None }
+        if temp <= MAX_UEFI_TIME { Some(temp) } else { None }
     }
 
     pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
-        let temp = Self(self.0.checked_sub(*other)?);
-
-        // Check if can be represented in UEFI
-        if temp.to_uefi(0, 0).is_some() { Some(temp) } else { None }
+        self.0.checked_sub(*other).map(Self)
     }
 }
 
@@ -113,8 +125,19 @@ pub(crate) mod system_time_internal {
     }
 
     pub(crate) const fn from_uefi(t: &Time) -> Duration {
-        assert!(t.month <= 12);
-        assert!(t.month != 0);
+        assert!(t.month <= 12 && t.month != 0);
+        assert!(t.year >= 1900 && t.year <= 9999);
+        assert!(t.day <= 31 && t.day != 0);
+
+        assert!(t.second < 60);
+        assert!(t.minute < 60);
+        assert!(t.hour < 24);
+        assert!(t.nanosecond < 1_000_000_000);
+
+        assert!(
+            (t.timezone <= 1440 && t.timezone >= -1440)
+                || t.timezone == r_efi::efi::UNSPECIFIED_TIMEZONE
+        );
 
         const YEAR_BASE: u32 = 4800; /* Before min year, multiple of 400. */
 
@@ -148,17 +171,13 @@ pub(crate) mod system_time_internal {
 
     pub(crate) const fn to_uefi(dur: &Duration, timezone: i16, daylight: u8) -> Option<Time> {
         // Check timzone validity
-        assert!(timezone <= 1440);
-        assert!(timezone >= -1440);
+        assert!(timezone <= 1440 && timezone >= -1440);
 
-        let secs: u64 = if timezone == r_efi::efi::UNSPECIFIED_TIMEZONE {
-            dur.as_secs()
-        } else {
-            // FIXME: use checked_sub_signed once stablized
-            dur.as_secs().checked_add_signed((-timezone as i64) * SECS_IN_MINUTE as i64).unwrap()
-        };
+        // FIXME(#126043): use checked_sub_signed once stablized
+        let secs =
+            dur.as_secs().checked_add_signed((-timezone as i64) * SECS_IN_MINUTE as i64).unwrap();
 
-        // Convert to UTC
+        // Convert to seconds since 1900-01-01-00:00:00 in timezone.
         let Some(secs) = secs.checked_sub(TIMEZONE_DELTA) else { return None };
 
         let days = secs / SECS_IN_DAY;