feat(bootloader-interface): add support for loader boot times

src/actions/chainload.rs

@@ -104,7 +104,7 @@ pub fn chainload(context: Rc<SproutContext>, configuration: &ChainloadConfigurat
     }
 
     // Mark execution of an entry in the bootloader interface.
-    BootloaderInterface::mark_exec()
+    BootloaderInterface::mark_exec(context.root().timer())
         .context("unable to mark execution of boot entry in bootloader interface")?;
 
     // Start the loaded image.

src/context.rs

@@ -1,5 +1,6 @@
 use crate::actions::ActionDeclaration;
 use crate::options::SproutOptions;
+use crate::platform::timer::PlatformTimer;
 use anyhow::anyhow;
 use anyhow::{Result, bail};
 use std::cmp::Reverse;
@@ -12,22 +13,29 @@ const CONTEXT_FINALIZE_ITERATION_LIMIT: usize = 100;
 
 /// Declares a root context for Sprout.
 /// This contains data that needs to be shared across Sprout.
-#[derive(Default)]
 pub struct RootContext {
     /// The actions that are available in Sprout.
     actions: BTreeMap<String, ActionDeclaration>,
     /// The device path of the loaded Sprout image.
     loaded_image_path: Option<Box<DevicePath>>,
+    /// Platform timer started at the beginning of the boot process.
+    timer: PlatformTimer,
     /// The global options of Sprout.
     options: SproutOptions,
 }
 
 impl RootContext {
     /// Creates a new root context with the `loaded_image_device_path` which will be stored
-    /// in the context for easy access.
+    /// in the context for easy access. We also provide a `timer` which is used to measure elapsed
-    pub fn new(loaded_image_device_path: Box<DevicePath>, options: SproutOptions) -> Self {
+    /// time for the bootloader.
+    pub fn new(
+        loaded_image_device_path: Box<DevicePath>,
+        timer: PlatformTimer,
+        options: SproutOptions,
+    ) -> Self {
         Self {
             actions: BTreeMap::new(),
+            timer,
             loaded_image_path: Some(loaded_image_device_path),
             options,
         }
@@ -43,6 +51,11 @@ impl RootContext {
         &mut self.actions
     }
 
+    /// Access the platform timer that is started at the beginning of the boot process.
+    pub fn timer(&self) -> &PlatformTimer {
+        &self.timer
+    }
+
     /// Access the device path of the loaded Sprout image.
     pub fn loaded_image_path(&self) -> Result<&DevicePath> {
         self.loaded_image_path

src/integrations/bootloader_interface.rs

@@ -1,3 +1,4 @@
+use crate::platform::timer::PlatformTimer;
 use anyhow::{Context, Result};
 use uefi::{CString16, Guid, guid};
 use uefi_raw::table::runtime::{VariableAttributes, VariableVendor};
@@ -11,14 +12,14 @@ impl BootloaderInterface {
 
     /// Tell the system that Sprout was initialized at the current time.
     pub fn mark_init() -> Result<()> {
-        // TODO(azenla): Implement support for LoaderTimeInitUSec here.
+        Self::set_cstr16("LoaderTimeInitUSec", "0")
-        Ok(())
     }
 
     /// Tell the system that Sprout is about to execute the boot entry.
-    pub fn mark_exec() -> Result<()> {
+    pub fn mark_exec(timer: &PlatformTimer) -> Result<()> {
-        // TODO(azenla): Implement support for LoaderTimeExecUSec here.
+        // Measure the elapsed time since the bootloader was started.
-        Ok(())
+        let elapsed = timer.elapsed();
+        Self::set_cstr16("LoaderTimeExecUSec", &elapsed.as_micros().to_string())
     }
 
     /// Tell the system what the partition GUID of the ESP Sprout was booted from is.

src/main.rs

@@ -1,5 +1,6 @@
 #![doc = include_str!("../README.md")]
 #![feature(uefi_std)]
+extern crate core;
 
 use crate::config::RootConfiguration;
 use crate::context::{RootContext, SproutContext};
@@ -8,6 +9,7 @@ use crate::integrations::bootloader_interface::BootloaderInterface;
 use crate::options::SproutOptions;
 use crate::options::parser::OptionsRepresentable;
 use crate::phases::phase;
+use crate::platform::timer::PlatformTimer;
 use crate::utils::PartitionGuidForm;
 use anyhow::{Context, Result, bail};
 use log::{error, info};
@@ -40,6 +42,9 @@ pub mod extractors;
 /// generators: Runtime code that can generate entries with specific values.
 pub mod generators;
 
+/// platform: Integration or support code for specific hardware platforms.
+pub mod platform;
+
 /// menu: Display a boot menu to select an entry to boot.
 pub mod menu;
 
@@ -60,6 +65,9 @@ pub mod utils;
 
 /// Run Sprout, returning an error if one occurs.
 fn run() -> Result<()> {
+    // Start the platform timer.
+    let timer = PlatformTimer::start();
+
     // Mark the initialization of Sprout in the bootloader interface.
     BootloaderInterface::mark_init()
         .context("unable to mark initialization in bootloader interface")?;
@@ -101,7 +109,7 @@ fn run() -> Result<()> {
     }
 
     // Create the root context.
-    let mut root = RootContext::new(loaded_image_path, options);
+    let mut root = RootContext::new(loaded_image_path, timer, options);
 
     // Insert the configuration actions into the root context.
     root.actions_mut().extend(config.actions.clone());

src/platform.rs

@@ -0,0 +1,2 @@
+/// timer: Platform timer support code.
+pub mod timer;

src/platform/timer.rs

@@ -0,0 +1,81 @@
+use std::time::Duration;
+
+/// Support for aarch64 timers.
+#[cfg(target_arch = "aarch64")]
+pub mod aarch64;
+
+/// Support for x86_64 timers.
+#[cfg(target_arch = "x86_64")]
+pub mod x86_64;
+
+/// The tick frequency of the platform.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum TickFrequency {
+    /// The platform provides the tick frequency.
+    Hardware(u64),
+    /// The tick frequency is measured internally.
+    Measured(u64, Duration),
+}
+
+impl TickFrequency {
+    /// Acquire the tick frequency reported by the platform.
+    fn ticks(&self) -> u64 {
+        match self {
+            TickFrequency::Hardware(frequency) => *frequency,
+            TickFrequency::Measured(frequency, _) => *frequency,
+        }
+    }
+
+    /// Calculate the nanoseconds represented by a tick.
+    fn nanos(&self) -> f64 {
+        1.0e9_f64 / (self.ticks() as f64)
+    }
+
+    /// Produce a duration from the provided elapsed `ticks` value.
+    fn duration(&self, ticks: u64) -> Duration {
+        let accuracy = self.nanos();
+        let nanos = ticks as f64 * accuracy;
+        Duration::from_nanos(nanos as u64)
+    }
+}
+
+/// Acquire the tick value reported by the platform.
+fn arch_ticks() -> u64 {
+    #[cfg(target_arch = "aarch64")]
+    return aarch64::ticks();
+    #[cfg(target_arch = "x86_64")]
+    return x86_64::ticks();
+}
+
+/// Acquire the tick frequency reported by the platform.
+fn arch_frequency() -> TickFrequency {
+    #[cfg(target_arch = "aarch64")]
+    return aarch64::frequency();
+    #[cfg(target_arch = "x86_64")]
+    return x86_64::frequency();
+}
+
+/// Platform timer that allows measurement of the elapsed time.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct PlatformTimer {
+    /// The start tick value.
+    start: u64,
+    /// The tick frequency of the platform.
+    frequency: TickFrequency,
+}
+
+impl PlatformTimer {
+    /// Start a platform timer at the current instant.
+    pub fn start() -> Self {
+        Self {
+            start: arch_ticks(),
+            frequency: arch_frequency(),
+        }
+    }
+
+    /// Measure the elapsed duration since the timer was started.
+    pub fn elapsed(&self) -> Duration {
+        let duration = arch_ticks() - self.start;
+        self.frequency.duration(duration)
+    }
+}

src/platform/timer/aarch64.rs

@@ -0,0 +1,33 @@
+use crate::platform::timer::TickFrequency;
+use std::arch::asm;
+
+/// Reads the cntvct_el0 counter and returns the value.
+pub fn ticks() -> u64 {
+    let counter: u64;
+    unsafe {
+        asm!("mrs x0, cntvct_el0", out("x0") counter);
+    }
+    counter
+}
+
+/// We can use the actual ticks value as our start value.
+pub fn start() -> u64 {
+    ticks()
+}
+
+/// We can use the actual ticks value as our stop value.
+pub fn stop() -> u64 {
+    ticks()
+}
+
+/// Our frequency is provided by cntfrq_el0 on the platform.
+pub fn frequency() -> TickFrequency {
+    let frequency: u64;
+    unsafe {
+        asm!(
+            "mrs x0, cntfrq_el0",
+            out("x0") frequency
+        );
+    }
+    TickFrequency::Hardware(frequency)
+}

src/platform/timer/x86_64.rs

@@ -0,0 +1,66 @@
+use crate::platform::timer::TickFrequency;
+use core::arch::asm;
+use std::time::Duration;
+
+/// We will measure the frequency of the timer based on 1000 microseconds.
+/// This will result in a call to BS->Stall(1000) in the end.
+const MEASURE_FREQUENCY_DURATION: Duration = Duration::from_micros(1000);
+
+/// Read the number of ticks from the platform timer.
+pub fn ticks() -> u64 {
+    let mut eax: u32;
+    let mut edx: u32;
+
+    unsafe {
+        asm!("rdtsc", out("eax") eax, out("edx") edx);
+    }
+
+    (edx as u64) << 32 | eax as u64
+}
+
+/// Read the starting number of ticks from the platform timer.
+pub fn start() -> u64 {
+    let rax: u64;
+    unsafe {
+        asm!(
+            "mfence",
+            "lfence",
+            "rdtsc",
+            "shl rdx, 32",
+            "or rax, rdx",
+            out("rax") rax
+        );
+    }
+    rax
+}
+
+/// Read the ending number of ticks from the platform timer.
+pub fn stop() -> u64 {
+    let rax: u64;
+    unsafe {
+        asm!(
+        "rdtsc",
+        "lfence",
+        "shl rdx, 32",
+        "or rax, rdx",
+        out("rax") rax
+        );
+    }
+    rax
+}
+
+/// Measure the frequency of the platform timer.
+fn measure_frequency(duration: &Duration) -> u64 {
+    let start = start();
+    uefi::boot::stall(*duration);
+    let stop = stop();
+    let elapsed = (stop - start) as f64;
+    (elapsed / duration.as_secs_f64()) as u64
+}
+
+/// Acquire the platform timer frequency.
+/// On x86_64, this is slightly expensive, so it should be done once.
+pub fn frequency() -> TickFrequency {
+    let frequency = measure_frequency(&MEASURE_FREQUENCY_DURATION);
+    TickFrequency::Measured(frequency, MEASURE_FREQUENCY_DURATION)
+}