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22 KiB
22 KiB
Tutorial 07 - Timestamps
tl;dr
- We add abstractions for timer hardware, and implement them for the ARM architectural timer in
_arch/aarch64. - The new timer functions are used to annotate UART prints with timestamps, and to get rid of the
cycle-based delays in the
GPIOdevice driver, which boosts accuracy. - A
warn!()macro is added.
Test it
Check it out via chainboot (added in previous tutorial):
$ make chainboot
[...]
Minipush 1.0
[MP] ⏳ Waiting for /dev/ttyUSB0
[MP] ✅ Serial connected
[MP] 🔌 Please power the target now
__ __ _ _ _ _
| \/ (_)_ _ (_) | ___ __ _ __| |
| |\/| | | ' \| | |__/ _ \/ _` / _` |
|_| |_|_|_||_|_|____\___/\__,_\__,_|
Raspberry Pi 3
[ML] Requesting binary
[MP] ⏩ Pushing 11 KiB =========================================🦀 100% 0 KiB/s Time: 00:00:00
[ML] Loaded! Executing the payload now
[ 0.543941] Booting on: Raspberry Pi 3
[ 0.545059] Architectural timer resolution: 52 ns
[ 0.547358] Drivers loaded:
[ 0.548703] 1. BCM GPIO
[ 0.550135] 2. BCM PL011 UART
[W 0.551828] Spin duration smaller than architecturally supported, skipping
[ 0.555212] Spinning for 1 second
[ 1.556818] Spinning for 1 second
[ 2.557690] Spinning for 1 second
Diff to previous
Binary files 06_uart_chainloader/demo_payload_rpi3.img and 07_timestamps/demo_payload_rpi3.img differ
Binary files 06_uart_chainloader/demo_payload_rpi4.img and 07_timestamps/demo_payload_rpi4.img differ
diff -uNr 06_uart_chainloader/Makefile 07_timestamps/Makefile
--- 06_uart_chainloader/Makefile
+++ 07_timestamps/Makefile
@@ -25,7 +25,6 @@
READELF_BINARY = aarch64-none-elf-readelf
LINKER_FILE = src/bsp/raspberrypi/link.ld
RUSTC_MISC_ARGS = -C target-cpu=cortex-a53
- CHAINBOOT_DEMO_PAYLOAD = demo_payload_rpi3.img
else ifeq ($(BSP),rpi4)
TARGET = aarch64-unknown-none-softfloat
KERNEL_BIN = kernel8.img
@@ -37,7 +36,6 @@
READELF_BINARY = aarch64-none-elf-readelf
LINKER_FILE = src/bsp/raspberrypi/link.ld
RUSTC_MISC_ARGS = -C target-cpu=cortex-a72
- CHAINBOOT_DEMO_PAYLOAD = demo_payload_rpi4.img
endif
# Export for build.rs
@@ -82,8 +80,7 @@
EXEC_QEMU = $(QEMU_BINARY) -M $(QEMU_MACHINE_TYPE)
EXEC_MINIPUSH = ruby ../utils/minipush.rb
-.PHONY: all $(KERNEL_ELF) $(KERNEL_BIN) doc qemu qemuasm chainboot clippy clean readelf objdump nm \
- check
+.PHONY: all $(KERNEL_ELF) $(KERNEL_BIN) doc qemu chainboot clippy clean readelf objdump nm check
all: $(KERNEL_BIN)
@@ -105,14 +102,10 @@
qemu: $(KERNEL_BIN)
$(call colorecho, "\nLaunching QEMU")
@$(DOCKER_QEMU) $(EXEC_QEMU) $(QEMU_RELEASE_ARGS) -kernel $(KERNEL_BIN)
-
-qemuasm: $(KERNEL_BIN)
- $(call colorecho, "\nLaunching QEMU with ASM output")
- @$(DOCKER_QEMU) $(EXEC_QEMU) $(QEMU_RELEASE_ARGS) -kernel $(KERNEL_BIN) -d in_asm
endif
-chainboot:
- @$(DOCKER_CHAINBOOT) $(EXEC_MINIPUSH) $(DEV_SERIAL) $(CHAINBOOT_DEMO_PAYLOAD)
+chainboot: $(KERNEL_BIN)
+ @$(DOCKER_CHAINBOOT) $(EXEC_MINIPUSH) $(DEV_SERIAL) $(KERNEL_BIN)
clippy:
@RUSTFLAGS="$(RUSTFLAGS_PEDANTIC)" $(CLIPPY_CMD)
diff -uNr 06_uart_chainloader/src/_arch/aarch64/cpu/boot.s 07_timestamps/src/_arch/aarch64/cpu/boot.s
--- 06_uart_chainloader/src/_arch/aarch64/cpu/boot.s
+++ 07_timestamps/src/_arch/aarch64/cpu/boot.s
@@ -22,31 +22,20 @@
and x1, x1, _core_id_mask
ldr x2, BOOT_CORE_ID // provided by bsp/__board_name__/cpu.rs
cmp x1, x2
- b.ne 2f
+ b.ne 1f
- // If execution reaches here, it is the boot core.
-
- // Next, relocate the binary.
- adr x0, __binary_nonzero_start // The address the binary got loaded to.
- ldr x1, =__binary_nonzero_start // The address the binary was linked to.
- ldr x2, =__binary_nonzero_end_exclusive
-
-1: ldr x3, [x0], #8
- str x3, [x1], #8
- cmp x1, x2
- b.lo 1b
+ // If execution reaches here, it is the boot core. Now, prepare the jump to Rust code.
// Set the stack pointer.
ldr x0, =__boot_core_stack_end_exclusive
mov sp, x0
- // Jump to the relocated Rust code.
- ldr x1, =_start_rust
- br x1
+ // Jump to Rust code.
+ b _start_rust
// Infinitely wait for events (aka "park the core").
-2: wfe
- b 2b
+1: wfe
+ b 1b
.size _start, . - _start
.type _start, function
diff -uNr 06_uart_chainloader/src/_arch/aarch64/cpu.rs 07_timestamps/src/_arch/aarch64/cpu.rs
--- 06_uart_chainloader/src/_arch/aarch64/cpu.rs
+++ 07_timestamps/src/_arch/aarch64/cpu.rs
@@ -19,15 +19,6 @@
pub use asm::nop;
-/// Spin for `n` cycles.
-#[cfg(feature = "bsp_rpi3")]
-#[inline(always)]
-pub fn spin_for_cycles(n: usize) {
- for _ in 0..n {
- asm::nop();
- }
-}
-
/// Pause execution on the core.
#[inline(always)]
pub fn wait_forever() -> ! {
diff -uNr 06_uart_chainloader/src/_arch/aarch64/time.rs 07_timestamps/src/_arch/aarch64/time.rs
--- 06_uart_chainloader/src/_arch/aarch64/time.rs
+++ 07_timestamps/src/_arch/aarch64/time.rs
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: MIT OR Apache-2.0
+//
+// Copyright (c) 2018-2021 Andre Richter <andre.o.richter@gmail.com>
+
+//! Architectural timer primitives.
+//!
+//! # Orientation
+//!
+//! Since arch modules are imported into generic modules using the path attribute, the path of this
+//! file is:
+//!
+//! crate::time::arch_time
+
+use crate::{time, warn};
+use core::time::Duration;
+use cortex_a::{barrier, regs::*};
+
+//--------------------------------------------------------------------------------------------------
+// Private Definitions
+//--------------------------------------------------------------------------------------------------
+
+const NS_PER_S: u64 = 1_000_000_000;
+
+/// ARMv8 Generic Timer.
+struct GenericTimer;
+
+//--------------------------------------------------------------------------------------------------
+// Global instances
+//--------------------------------------------------------------------------------------------------
+
+static TIME_MANAGER: GenericTimer = GenericTimer;
+
+//--------------------------------------------------------------------------------------------------
+// Private Code
+//--------------------------------------------------------------------------------------------------
+
+impl GenericTimer {
+ #[inline(always)]
+ fn read_cntpct(&self) -> u64 {
+ // Prevent that the counter is read ahead of time due to out-of-order execution.
+ unsafe { barrier::isb(barrier::SY) };
+ CNTPCT_EL0.get()
+ }
+}
+
+//--------------------------------------------------------------------------------------------------
+// Public Code
+//--------------------------------------------------------------------------------------------------
+
+/// Return a reference to the time manager.
+pub fn time_manager() -> &'static impl time::interface::TimeManager {
+ &TIME_MANAGER
+}
+
+//------------------------------------------------------------------------------
+// OS Interface Code
+//------------------------------------------------------------------------------
+
+impl time::interface::TimeManager for GenericTimer {
+ fn resolution(&self) -> Duration {
+ Duration::from_nanos(NS_PER_S / (CNTFRQ_EL0.get() as u64))
+ }
+
+ fn uptime(&self) -> Duration {
+ let current_count: u64 = self.read_cntpct() * NS_PER_S;
+ let frq: u64 = CNTFRQ_EL0.get() as u64;
+
+ Duration::from_nanos(current_count / frq)
+ }
+
+ fn spin_for(&self, duration: Duration) {
+ // Instantly return on zero.
+ if duration.as_nanos() == 0 {
+ return;
+ }
+
+ // Calculate the register compare value.
+ let frq = CNTFRQ_EL0.get();
+ let x = match frq.checked_mul(duration.as_nanos() as u64) {
+ None => {
+ warn!("Spin duration too long, skipping");
+ return;
+ }
+ Some(val) => val,
+ };
+ let tval = x / NS_PER_S;
+
+ // Check if it is within supported bounds.
+ let warn: Option<&str> = if tval == 0 {
+ Some("smaller")
+ // The upper 32 bits of CNTP_TVAL_EL0 are reserved.
+ } else if tval > u32::max_value().into() {
+ Some("bigger")
+ } else {
+ None
+ };
+
+ if let Some(w) = warn {
+ warn!(
+ "Spin duration {} than architecturally supported, skipping",
+ w
+ );
+ return;
+ }
+
+ // Set the compare value register.
+ CNTP_TVAL_EL0.set(tval);
+
+ // Kick off the counting. // Disable timer interrupt.
+ CNTP_CTL_EL0.modify(CNTP_CTL_EL0::ENABLE::SET + CNTP_CTL_EL0::IMASK::SET);
+
+ // ISTATUS will be '1' when cval ticks have passed. Busy-check it.
+ while !CNTP_CTL_EL0.matches_all(CNTP_CTL_EL0::ISTATUS::SET) {}
+
+ // Disable counting again.
+ CNTP_CTL_EL0.modify(CNTP_CTL_EL0::ENABLE::CLEAR);
+ }
+}
diff -uNr 06_uart_chainloader/src/bsp/device_driver/bcm/bcm2xxx_gpio.rs 07_timestamps/src/bsp/device_driver/bcm/bcm2xxx_gpio.rs
--- 06_uart_chainloader/src/bsp/device_driver/bcm/bcm2xxx_gpio.rs
+++ 07_timestamps/src/bsp/device_driver/bcm/bcm2xxx_gpio.rs
@@ -139,25 +139,19 @@
/// Disable pull-up/down on pins 14 and 15.
#[cfg(feature = "bsp_rpi3")]
fn disable_pud_14_15_bcm2837(&mut self) {
- use crate::cpu;
+ use crate::{time, time::interface::TimeManager};
+ use core::time::Duration;
- // Make an educated guess for a good delay value (Sequence described in the BCM2837
- // peripherals PDF).
- //
- // - According to Wikipedia, the fastest RPi4 clocks around 1.5 GHz.
- // - The Linux 2837 GPIO driver waits 1 µs between the steps.
- //
- // So lets try to be on the safe side and default to 2000 cycles, which would equal 1 µs
- // would the CPU be clocked at 2 GHz.
- const DELAY: usize = 2000;
+ // The Linux 2837 GPIO driver waits 1 µs between the steps.
+ const DELAY: Duration = Duration::from_micros(1);
self.registers.GPPUD.write(GPPUD::PUD::Off);
- cpu::spin_for_cycles(DELAY);
+ time::time_manager().spin_for(DELAY);
self.registers
.GPPUDCLK0
.write(GPPUDCLK0::PUDCLK15::AssertClock + GPPUDCLK0::PUDCLK14::AssertClock);
- cpu::spin_for_cycles(DELAY);
+ time::time_manager().spin_for(DELAY);
self.registers.GPPUD.write(GPPUD::PUD::Off);
self.registers.GPPUDCLK0.set(0);
diff -uNr 06_uart_chainloader/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs 07_timestamps/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
--- 06_uart_chainloader/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
+++ 07_timestamps/src/bsp/device_driver/bcm/bcm2xxx_pl011_uart.rs
@@ -279,7 +279,7 @@
}
/// Retrieve a character.
- fn read_char(&mut self, blocking_mode: BlockingMode) -> Option<char> {
+ fn read_char_converting(&mut self, blocking_mode: BlockingMode) -> Option<char> {
// If RX FIFO is empty,
if self.registers.FR.matches_all(FR::RXFE::SET) {
// immediately return in non-blocking mode.
@@ -294,7 +294,12 @@
}
// Read one character.
- let ret = self.registers.DR.get() as u8 as char;
+ let mut ret = self.registers.DR.get() as u8 as char;
+
+ // Convert carrige return to newline.
+ if ret == '\r' {
+ ret = '\n'
+ }
// Update statistics.
self.chars_read += 1;
@@ -374,14 +379,14 @@
impl console::interface::Read for PL011Uart {
fn read_char(&self) -> char {
self.inner
- .lock(|inner| inner.read_char(BlockingMode::Blocking).unwrap())
+ .lock(|inner| inner.read_char_converting(BlockingMode::Blocking).unwrap())
}
fn clear_rx(&self) {
// Read from the RX FIFO until it is indicating empty.
while self
.inner
- .lock(|inner| inner.read_char(BlockingMode::NonBlocking))
+ .lock(|inner| inner.read_char_converting(BlockingMode::NonBlocking))
.is_some()
{}
}
diff -uNr 06_uart_chainloader/src/bsp/raspberrypi/link.ld 07_timestamps/src/bsp/raspberrypi/link.ld
--- 06_uart_chainloader/src/bsp/raspberrypi/link.ld
+++ 07_timestamps/src/bsp/raspberrypi/link.ld
@@ -16,8 +16,7 @@
SECTIONS
{
- /* Set the link address to 32 MiB */
- . = 0x2000000;
+ . = __rpi_load_addr;
/* ^ */
/* | stack */
/* | growth */
@@ -27,7 +26,6 @@
/***********************************************************************************************
* Code + RO Data + Global Offset Table
***********************************************************************************************/
- __binary_nonzero_start = .;
.text :
{
KEEP(*(.text._start))
@@ -51,12 +49,8 @@
***********************************************************************************************/
.data : { *(.data*) } :segment_rw
- /* Fill up to 8 byte, b/c relocating the binary is done in u64 chunks */
- . = ALIGN(8);
- __binary_nonzero_end_exclusive = .;
-
/* Section is zeroed in u64 chunks, align start and end to 8 bytes */
- .bss :
+ .bss : ALIGN(8)
{
__bss_start = .;
*(.bss*);
diff -uNr 06_uart_chainloader/src/bsp/raspberrypi/memory.rs 07_timestamps/src/bsp/raspberrypi/memory.rs
--- 06_uart_chainloader/src/bsp/raspberrypi/memory.rs
+++ 07_timestamps/src/bsp/raspberrypi/memory.rs
@@ -23,10 +23,9 @@
/// The board's physical memory map.
#[rustfmt::skip]
pub(super) mod map {
- pub const BOARD_DEFAULT_LOAD_ADDRESS: usize = 0x8_0000;
- pub const GPIO_OFFSET: usize = 0x0020_0000;
- pub const UART_OFFSET: usize = 0x0020_1000;
+ pub const GPIO_OFFSET: usize = 0x0020_0000;
+ pub const UART_OFFSET: usize = 0x0020_1000;
/// Physical devices.
#[cfg(feature = "bsp_rpi3")]
@@ -53,13 +52,7 @@
// Public Code
//--------------------------------------------------------------------------------------------------
-/// The address on which the Raspberry firmware loads every binary by default.
-#[inline(always)]
-pub fn board_default_load_addr() -> *const u64 {
- map::BOARD_DEFAULT_LOAD_ADDRESS as _
-}
-
-/// Return the inclusive range spanning the relocated .bss section.
+/// Return the inclusive range spanning the .bss section.
///
/// # Safety
///
diff -uNr 06_uart_chainloader/src/cpu.rs 07_timestamps/src/cpu.rs
--- 06_uart_chainloader/src/cpu.rs
+++ 07_timestamps/src/cpu.rs
@@ -14,6 +14,3 @@
// Architectural Public Reexports
//--------------------------------------------------------------------------------------------------
pub use arch_cpu::{nop, wait_forever};
-
-#[cfg(feature = "bsp_rpi3")]
-pub use arch_cpu::spin_for_cycles;
diff -uNr 06_uart_chainloader/src/main.rs 07_timestamps/src/main.rs
--- 06_uart_chainloader/src/main.rs
+++ 07_timestamps/src/main.rs
@@ -107,7 +107,6 @@
//! [`runtime_init::runtime_init()`]: runtime_init/fn.runtime_init.html
#![allow(clippy::clippy::upper_case_acronyms)]
-#![feature(asm)]
#![feature(const_fn_fn_ptr_basics)]
#![feature(format_args_nl)]
#![feature(global_asm)]
@@ -125,6 +124,7 @@
mod print;
mod runtime_init;
mod synchronization;
+mod time;
/// Early init code.
///
@@ -149,51 +149,31 @@
/// The main function running after the early init.
fn kernel_main() -> ! {
- use bsp::console::console;
- use console::interface::All;
+ use core::time::Duration;
+ use driver::interface::DriverManager;
+ use time::interface::TimeManager;
- println!(" __ __ _ _ _ _ ");
- println!("| \\/ (_)_ _ (_) | ___ __ _ __| |");
- println!("| |\\/| | | ' \\| | |__/ _ \\/ _` / _` |");
- println!("|_| |_|_|_||_|_|____\\___/\\__,_\\__,_|");
- println!();
- println!("{:^37}", bsp::board_name());
- println!();
- println!("[ML] Requesting binary");
- console().flush();
-
- // Discard any spurious received characters before starting with the loader protocol.
- console().clear_rx();
-
- // Notify `Minipush` to send the binary.
- for _ in 0..3 {
- console().write_char(3 as char);
- }
+ info!("Booting on: {}", bsp::board_name());
- // Read the binary's size.
- let mut size: u32 = u32::from(console().read_char() as u8);
- size |= u32::from(console().read_char() as u8) << 8;
- size |= u32::from(console().read_char() as u8) << 16;
- size |= u32::from(console().read_char() as u8) << 24;
-
- // Trust it's not too big.
- console().write_char('O');
- console().write_char('K');
-
- let kernel_addr: *mut u8 = bsp::memory::board_default_load_addr() as *mut u8;
- unsafe {
- // Read the kernel byte by byte.
- for i in 0..size {
- core::ptr::write_volatile(kernel_addr.offset(i as isize), console().read_char() as u8)
- }
+ info!(
+ "Architectural timer resolution: {} ns",
+ time::time_manager().resolution().as_nanos()
+ );
+
+ info!("Drivers loaded:");
+ for (i, driver) in bsp::driver::driver_manager()
+ .all_device_drivers()
+ .iter()
+ .enumerate()
+ {
+ info!(" {}. {}", i + 1, driver.compatible());
}
- println!("[ML] Loaded! Executing the payload now\n");
- console().flush();
+ // Test a failing timer case.
+ time::time_manager().spin_for(Duration::from_nanos(1));
- // Use black magic to create a function pointer.
- let kernel: fn() -> ! = unsafe { core::mem::transmute(kernel_addr) };
-
- // Jump to loaded kernel!
- kernel()
+ loop {
+ info!("Spinning for 1 second");
+ time::time_manager().spin_for(Duration::from_secs(1));
+ }
}
diff -uNr 06_uart_chainloader/src/print.rs 07_timestamps/src/print.rs
--- 06_uart_chainloader/src/print.rs
+++ 07_timestamps/src/print.rs
@@ -36,3 +36,71 @@
$crate::print::_print(format_args_nl!($($arg)*));
})
}
+
+/// Prints an info, with a newline.
+#[macro_export]
+macro_rules! info {
+ ($string:expr) => ({
+ #[allow(unused_imports)]
+ use crate::time::interface::TimeManager;
+
+ let timestamp = $crate::time::time_manager().uptime();
+ let timestamp_subsec_us = timestamp.subsec_micros();
+
+ $crate::print::_print(format_args_nl!(
+ concat!("[ {:>3}.{:03}{:03}] ", $string),
+ timestamp.as_secs(),
+ timestamp_subsec_us / 1_000,
+ timestamp_subsec_us modulo 1_000
+ ));
+ });
+ ($format_string:expr, $($arg:tt)*) => ({
+ #[allow(unused_imports)]
+ use crate::time::interface::TimeManager;
+
+ let timestamp = $crate::time::time_manager().uptime();
+ let timestamp_subsec_us = timestamp.subsec_micros();
+
+ $crate::print::_print(format_args_nl!(
+ concat!("[ {:>3}.{:03}{:03}] ", $format_string),
+ timestamp.as_secs(),
+ timestamp_subsec_us / 1_000,
+ timestamp_subsec_us modulo 1_000,
+ $($arg)*
+ ));
+ })
+}
+
+/// Prints a warning, with a newline.
+#[macro_export]
+macro_rules! warn {
+ ($string:expr) => ({
+ #[allow(unused_imports)]
+ use crate::time::interface::TimeManager;
+
+ let timestamp = $crate::time::time_manager().uptime();
+ let timestamp_subsec_us = timestamp.subsec_micros();
+
+ $crate::print::_print(format_args_nl!(
+ concat!("[W {:>3}.{:03}{:03}] ", $string),
+ timestamp.as_secs(),
+ timestamp_subsec_us / 1_000,
+ timestamp_subsec_us modulo 1_000
+ ));
+ });
+ ($format_string:expr, $($arg:tt)*) => ({
+ #[allow(unused_imports)]
+ use crate::time::interface::TimeManager;
+
+ let timestamp = $crate::time::time_manager().uptime();
+ let timestamp_subsec_us = timestamp.subsec_micros();
+
+ $crate::print::_print(format_args_nl!(
+ concat!("[W {:>3}.{:03}{:03}] ", $format_string),
+ timestamp.as_secs(),
+ timestamp_subsec_us / 1_000,
+ timestamp_subsec_us modulo 1_000,
+ $($arg)*
+ ));
+ })
+}
diff -uNr 06_uart_chainloader/src/time.rs 07_timestamps/src/time.rs
--- 06_uart_chainloader/src/time.rs
+++ 07_timestamps/src/time.rs
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: MIT OR Apache-2.0
+//
+// Copyright (c) 2020-2021 Andre Richter <andre.o.richter@gmail.com>
+
+//! Timer primitives.
+
+#[cfg(target_arch = "aarch64")]
+#[path = "_arch/aarch64/time.rs"]
+mod arch_time;
+
+//--------------------------------------------------------------------------------------------------
+// Architectural Public Reexports
+//--------------------------------------------------------------------------------------------------
+pub use arch_time::time_manager;
+
+//--------------------------------------------------------------------------------------------------
+// Public Definitions
+//--------------------------------------------------------------------------------------------------
+
+/// Timekeeping interfaces.
+pub mod interface {
+ use core::time::Duration;
+
+ /// Time management functions.
+ pub trait TimeManager {
+ /// The timer's resolution.
+ fn resolution(&self) -> Duration;
+
+ /// The uptime since power-on of the device.
+ ///
+ /// This includes time consumed by firmware and bootloaders.
+ fn uptime(&self) -> Duration;
+
+ /// Spin for a given duration.
+ fn spin_for(&self, duration: Duration);
+ }
+}
diff -uNr 06_uart_chainloader/update.sh 07_timestamps/update.sh
--- 06_uart_chainloader/update.sh
+++ 07_timestamps/update.sh
@@ -1,8 +0,0 @@
-#!/usr/bin/env bash
-
-cd ../05_drivers_gpio_uart
-BSP=rpi4 make
-cp kernel8.img ../06_uart_chainloader/demo_payload_rpi4.img
-make
-cp kernel8.img ../06_uart_chainloader/demo_payload_rpi3.img
-rm kernel8.img