Merge pull request #1041 from mkroening/aarch64-timer-overflow

fix: overflow in time calculation on AArch64

src/arch/aarch64/kernel/processor.rs

@@ -140,7 +140,8 @@ pub fn shutdown() -> ! {
 pub fn get_timer_ticks() -> u64 {
 	// We simulate a timer with a 1 microsecond resolution by taking the CPU timestamp
 	// and dividing it by the CPU frequency in MHz.
-	(1000000 * get_timestamp()) / u64::from(CPU_FREQUENCY.get())
+	let ticks = 1000000 * u128::from(get_timestamp()) / u128::from(CPU_FREQUENCY.get());
+	u64::try_from(ticks).unwrap()
 }
 
 #[inline]
@@ -226,7 +227,8 @@ pub fn detect_frequency() {
 fn __set_oneshot_timer(wakeup_time: Option<u64>) {
 	if let Some(wt) = wakeup_time {
 		// wt is the absolute wakeup time in microseconds based on processor::get_timer_ticks.
-		let deadline: u64 = (wt * u64::from(CPU_FREQUENCY.get())) / 1000000;
+		let deadline = u128::from(wt) * u128::from(CPU_FREQUENCY.get()) / 1000000;
+		let deadline = u64::try_from(deadline).unwrap();
 
 		unsafe {
 			asm!(

src/arch/aarch64/kernel/systemtime.rs

@@ -44,10 +44,6 @@ fn rtc_read(off: usize) -> u32 {
 	value
 }
 
-pub fn get_boot_time() -> u64 {
-	*BOOT_TIME.get().unwrap()
-}
-
 pub fn init() {
 	let dtb = unsafe {
 		Dtb::from_raw(core::ptr::from_exposed_addr(
@@ -91,7 +87,8 @@ pub fn init() {
 				info!("Hermit booted on {boot_time}");
 
 				let micros = u64::try_from(boot_time.unix_timestamp_nanos() / 1000).unwrap();
-				BOOT_TIME.set(micros).unwrap();
+				let current_ticks = super::processor::get_timer_ticks();
+				BOOT_TIME.set(micros - current_ticks).unwrap();
 
 				return;
 			}
@@ -101,3 +98,8 @@ pub fn init() {
 	PL031_ADDRESS.set(VirtAddr::zero()).unwrap();
 	BOOT_TIME.set(0).unwrap();
 }
+
+/// Returns the current time in microseconds since UNIX epoch.
+pub fn now_micros() -> u64 {
+	*BOOT_TIME.get().unwrap() + super::processor::get_timer_ticks()
+}

src/arch/mod.rs

@@ -16,7 +16,6 @@ cfg_if::cfg_if! {
 		pub use self::aarch64::kernel::processor::set_oneshot_timer;
 		pub use self::aarch64::kernel::scheduler;
 		pub use self::aarch64::kernel::switch;
-		pub use self::aarch64::kernel::systemtime::get_boot_time;
 		#[cfg(feature = "smp")]
 		pub use self::aarch64::kernel::application_processor_init;
 		pub use self::aarch64::kernel::{
@@ -43,7 +42,6 @@ cfg_if::cfg_if! {
 		pub use self::x86_64::kernel::processor;
 		pub use self::x86_64::kernel::scheduler;
 		pub use self::x86_64::kernel::switch;
-		pub use self::x86_64::kernel::systemtime::get_boot_time;
 		#[cfg(target_os = "none")]
 		pub use self::x86_64::kernel::{
 			boot_application_processors,
@@ -61,7 +59,6 @@ cfg_if::cfg_if! {
 		#[cfg(feature = "smp")]
 		pub use self::riscv64::kernel::application_processor_init;
 		pub use self::riscv64::kernel::processor::{self, set_oneshot_timer, wakeup_core};
-		pub use self::riscv64::kernel::systemtime::get_boot_time;
 		pub use self::riscv64::kernel::{
 			boot_application_processors,
 			boot_processor_init,

src/arch/riscv64/kernel/systemtime.rs

@@ -1,6 +1,7 @@
 use log::warn;
 
-pub fn get_boot_time() -> u64 {
-	warn!("`get_boot_time` is currently stubbed");
-	0
+/// Returns the current time in microseconds since UNIX epoch.
+pub fn now_micros() -> u64 {
+	warn!("time is currently stubbed");
+	super::processor::get_timer_ticks()
 }

src/arch/x86_64/kernel/systemtime.rs

@@ -172,10 +172,6 @@ impl Rtc {
 
 static BOOT_TIME: OnceCell<u64> = OnceCell::new();
 
-pub fn get_boot_time() -> u64 {
-	*BOOT_TIME.get().unwrap()
-}
-
 pub fn init() {
 	let boot_time = match boot_info().platform_info {
 		PlatformInfo::Multiboot { .. } => {
@@ -199,3 +195,8 @@ pub fn init() {
 	let micros = u64::try_from(boot_time.unix_timestamp_nanos() / 1000).unwrap();
 	BOOT_TIME.set(micros).unwrap();
 }
+
+/// Returns the current time in microseconds since UNIX epoch.
+pub fn now_micros() -> u64 {
+	*BOOT_TIME.get().unwrap() + super::processor::get_timer_ticks()
+}

src/executor/device.rs

@@ -60,7 +60,7 @@ impl<'a> NetworkInterface<'a> {
 
 		// use the current time based on the wall-clock time as seed
 		let mut config = Config::new(hardware_addr);
-		config.random_seed = (arch::get_boot_time() + arch::processor::get_timer_ticks()) / 1000000;
+		config.random_seed = (arch::kernel::systemtime::now_micros()) / 1000000;
 		if device.capabilities().medium == Medium::Ethernet {
 			config.hardware_addr = hardware_addr;
 		}
@@ -129,7 +129,7 @@ impl<'a> NetworkInterface<'a> {
 
 		// use the current time based on the wall-clock time as seed
 		let mut config = Config::new(hardware_addr);
-		config.random_seed = (arch::get_boot_time() + arch::processor::get_timer_ticks()) / 1000000;
+		config.random_seed = (arch::kernel::systemtime::now_micros()) / 1000000;
 		if device.capabilities().medium == Medium::Ethernet {
 			config.hardware_addr = hardware_addr;
 		}

src/executor/network.rs

@@ -93,8 +93,7 @@ fn start_endpoint() -> u16 {
 
 #[inline]
 pub(crate) fn now() -> Instant {
-	let microseconds = arch::processor::get_timer_ticks() + arch::get_boot_time();
-	Instant::from_micros_const(microseconds.try_into().unwrap())
+	Instant::from_micros_const(arch::kernel::systemtime::now_micros().try_into().unwrap())
 }
 
 async fn network_run() {

src/fs/mem.rs

@@ -48,7 +48,7 @@ struct RomFileInterface {
 impl ObjectInterface for RomFileInterface {
 	fn read(&self, buf: &mut [u8]) -> Result<usize, IoError> {
 		{
-			let microseconds = arch::processor::get_timer_ticks() + arch::get_boot_time();
+			let microseconds = arch::kernel::systemtime::now_micros();
 			let mut guard = self.inner.write();
 			guard.attr.st_atime = microseconds / 1_000_000;
 			guard.attr.st_atime_nsec = (microseconds % 1_000_000) * 1000;
@@ -114,7 +114,7 @@ pub struct RamFileInterface {
 impl ObjectInterface for RamFileInterface {
 	fn read(&self, buf: &mut [u8]) -> Result<usize, IoError> {
 		{
-			let microseconds = arch::processor::get_timer_ticks() + arch::get_boot_time();
+			let microseconds = arch::kernel::systemtime::now_micros();
 			let mut guard = self.inner.write();
 			guard.attr.st_atime = microseconds / 1_000_000;
 			guard.attr.st_atime_nsec = (microseconds % 1_000_000) * 1000;
@@ -141,7 +141,7 @@ impl ObjectInterface for RamFileInterface {
 	}
 
 	fn write(&self, buf: &[u8]) -> Result<usize, IoError> {
-		let microseconds = arch::processor::get_timer_ticks() + arch::get_boot_time();
+		let microseconds = arch::kernel::systemtime::now_micros();
 		let mut guard = self.inner.write();
 		let mut pos_guard = self.pos.lock();
 		let pos = *pos_guard;
@@ -214,7 +214,7 @@ impl VfsNode for RomFile {
 
 impl RomFile {
 	pub unsafe fn new(ptr: *const u8, length: usize, mode: AccessPermission) -> Self {
-		let microseconds = arch::processor::get_timer_ticks() + arch::get_boot_time();
+		let microseconds = arch::kernel::systemtime::now_micros();
 		let attr = FileAttr {
 			st_size: length.try_into().unwrap(),
 			st_mode: mode | AccessPermission::S_IFREG,
@@ -270,7 +270,7 @@ impl VfsNode for RamFile {
 
 impl RamFile {
 	pub fn new(mode: AccessPermission) -> Self {
-		let microseconds = arch::processor::get_timer_ticks() + arch::get_boot_time();
+		let microseconds = arch::kernel::systemtime::now_micros();
 		let attr = FileAttr {
 			st_mode: mode | AccessPermission::S_IFREG,
 			st_atime: microseconds / 1_000_000,
@@ -298,7 +298,7 @@ pub(crate) struct MemDirectory {
 
 impl MemDirectory {
 	pub fn new(mode: AccessPermission) -> Self {
-		let microseconds = arch::processor::get_timer_ticks() + arch::get_boot_time();
+		let microseconds = arch::kernel::systemtime::now_micros();
 
 		Self {
 			inner: Arc::new(RwSpinLock::new(BTreeMap::new())),

src/syscalls/timer.rs

@@ -60,14 +60,12 @@ extern "C" fn __sys_clock_gettime(clock_id: u64, tp: *mut timespec) -> i32 {
 	let result = unsafe { &mut *tp };
 
 	match clock_id {
-		CLOCK_REALTIME | CLOCK_MONOTONIC => {
-			let mut microseconds = arch::processor::get_timer_ticks();
-
-			if clock_id == CLOCK_REALTIME {
-				microseconds += arch::get_boot_time();
-			}
-
-			*result = timespec::from_usec(microseconds);
+		CLOCK_REALTIME => {
+			*result = timespec::from_usec(arch::kernel::systemtime::now_micros());
+			0
+		}
+		CLOCK_MONOTONIC => {
+			*result = timespec::from_usec(arch::processor::get_timer_ticks());
 			0
 		}
 		_ => {
@@ -119,10 +117,10 @@ extern "C" fn __sys_clock_nanosleep(
 				+ (requested_time.tv_nsec as u64) / 1_000;
 
 			if flags & TIMER_ABSTIME > 0 {
-				microseconds -= arch::processor::get_timer_ticks();
-
 				if clock_id == CLOCK_REALTIME {
-					microseconds -= arch::get_boot_time();
+					microseconds -= arch::kernel::systemtime::now_micros();
+				} else {
+					microseconds -= arch::processor::get_timer_ticks();
 				}
 			}
 
@@ -164,7 +162,7 @@ extern "C" fn __sys_gettimeofday(tp: *mut timeval, tz: usize) -> i32 {
 	if let Some(result) = unsafe { tp.as_mut() } {
 		// Return the current time based on the wallclock time when we were booted up
 		// plus the current timer ticks.
-		let microseconds = arch::get_boot_time() + arch::processor::get_timer_ticks();
+		let microseconds = arch::kernel::systemtime::now_micros();
 		*result = timeval::from_usec(microseconds);
 	}
 

src/time.rs

@@ -67,9 +67,7 @@ pub struct SystemTime(timespec);
 impl SystemTime {
 	/// Returns the system time corresponding to "now".
 	pub fn now() -> Self {
-		let microseconds = arch::processor::get_timer_ticks() + arch::get_boot_time();
-
-		Self(timespec::from_usec(microseconds))
+		Self(timespec::from_usec(arch::kernel::systemtime::now_micros()))
 	}
 }