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rust-raspberrypi-OS-tutorials/08_timestamps/README.md
Andre Richter f6832bec31
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2019-12-31 00:00:09 +01:00

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# Tutorial 08 - Timestamps
## tl;dr
We add abstractions for the architectural timer, implement it for `aarch64` and
use it to annotate prints with timestamps; A `warn!()` macro is added.
## Test it
Check it out via chainboot (added in previous tutorial):
```console
make chainboot
[...]
### Listening on /dev/ttyUSB0
__ __ _ _ _ _
| \/ (_)_ _ (_) | ___ __ _ __| |
| |\/| | | ' \| | |__/ _ \/ _` / _` |
|_| |_|_|_||_|_|____\___/\__,_\__,_|
Raspberry Pi 3
[ML] Requesting binary
### sending kernel kernel8.img [13872 byte]
### finished sending
[ML] Loaded! Executing the payload now
[ 1.233286] Booting on: Raspberry Pi 3
[ 1.236282] Architectural timer resolution: 52 ns
[ 1.241023] Drivers loaded:
[ 1.243833] 1. GPIO
[ 1.246467] 2. PL011Uart
[W 1.249453] Spin duration smaller than architecturally supported, skipping
[ 1.256390] Spinning for 1 second
[ 2.259728] Spinning for 1 second
[ 3.262286] Spinning for 1 second
```
## Diff to previous
```diff
Binary files 07_uart_chainloader/demo_payload_rpi3.img and 08_timestamps/demo_payload_rpi3.img differ
Binary files 07_uart_chainloader/demo_payload_rpi4.img and 08_timestamps/demo_payload_rpi4.img differ
diff -uNr 07_uart_chainloader/Makefile 08_timestamps/Makefile
--- 07_uart_chainloader/Makefile
+++ 08_timestamps/Makefile
@@ -15,8 +15,7 @@
QEMU_MACHINE_TYPE = raspi3
QEMU_MISC_ARGS = -serial stdio -display none
LINKER_FILE = src/bsp/rpi/link.ld
- RUSTC_MISC_ARGS = -C target-cpu=cortex-a53 -C relocation-model=pic
- CHAINBOOT_DEMO_PAYLOAD = demo_payload_rpi3.img
+ RUSTC_MISC_ARGS = -C target-cpu=cortex-a53
else ifeq ($(BSP),rpi4)
TARGET = aarch64-unknown-none-softfloat
OUTPUT = kernel8.img
@@ -24,8 +23,7 @@
# QEMU_MACHINE_TYPE =
# QEMU_MISC_ARGS = -serial stdio -display none
LINKER_FILE = src/bsp/rpi/link.ld
- RUSTC_MISC_ARGS = -C target-cpu=cortex-a72 -C relocation-model=pic
- CHAINBOOT_DEMO_PAYLOAD = demo_payload_rpi4.img
+ RUSTC_MISC_ARGS = -C target-cpu=cortex-a72
endif
RUSTFLAGS = -C link-arg=-T$(LINKER_FILE) $(RUSTC_MISC_ARGS)
@@ -56,7 +54,7 @@
DOCKER_EXEC_RASPBOOT_DEV = /dev/ttyUSB0
# DOCKER_EXEC_RASPBOOT_DEV = /dev/ttyACM0
-.PHONY: all doc qemu qemuasm chainboot clippy clean readelf objdump nm
+.PHONY: all doc qemu chainboot clippy clean readelf objdump nm
all: clean $(OUTPUT)
@@ -74,23 +72,16 @@
ifeq ($(QEMU_MACHINE_TYPE),)
qemu:
@echo "This board is not yet supported for QEMU."
-
-qemuasm:
- @echo "This board is not yet supported for QEMU."
else
qemu: all
$(DOCKER_CMD) $(DOCKER_ARG_CURDIR) $(CONTAINER_UTILS) \
$(DOCKER_EXEC_QEMU) $(OUTPUT)
-
-qemuasm: all
- $(DOCKER_CMD) $(DOCKER_ARG_CURDIR) $(CONTAINER_UTILS) \
- $(DOCKER_EXEC_QEMU) $(OUTPUT) -d in_asm
endif
-chainboot:
+chainboot: all
$(DOCKER_CMD) $(DOCKER_ARG_CURDIR) $(DOCKER_ARG_TTY) \
$(CONTAINER_UTILS) $(DOCKER_EXEC_RASPBOOT) $(DOCKER_EXEC_RASPBOOT_DEV) \
- $(CHAINBOOT_DEMO_PAYLOAD)
+ $(OUTPUT)
clippy:
cargo xclippy --target=$(TARGET) --features bsp_$(BSP)
diff -uNr 07_uart_chainloader/src/arch/aarch64/time.rs 08_timestamps/src/arch/aarch64/time.rs
--- 07_uart_chainloader/src/arch/aarch64/time.rs
+++ 08_timestamps/src/arch/aarch64/time.rs
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: MIT OR Apache-2.0
+//
+// Copyright (c) 2018-2019 Andre Richter <andre.o.richter@gmail.com>
+
+//! Timer primitives.
+
+use crate::{interface, warn};
+use core::time::Duration;
+use cortex_a::regs::*;
+
+const NS_PER_S: u64 = 1_000_000_000;
+
+//--------------------------------------------------------------------------------------------------
+// Arch-public
+//--------------------------------------------------------------------------------------------------
+
+pub struct Timer;
+
+//--------------------------------------------------------------------------------------------------
+// OS interface implementations
+//--------------------------------------------------------------------------------------------------
+
+impl interface::time::Timer for Timer {
+ fn resolution(&self) -> Duration {
+ Duration::from_nanos(NS_PER_S / (CNTFRQ_EL0.get() as u64))
+ }
+
+ fn uptime(&self) -> Duration {
+ let frq: u64 = CNTFRQ_EL0.get() as u64;
+ let current_count: u64 = CNTPCT_EL0.get() * NS_PER_S;
+
+ 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() as u64;
+ 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")
+ } 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 as u32);
+
+ // 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 07_uart_chainloader/src/arch/aarch64.rs 08_timestamps/src/arch/aarch64.rs
--- 07_uart_chainloader/src/arch/aarch64.rs
+++ 08_timestamps/src/arch/aarch64.rs
@@ -5,8 +5,9 @@
//! AArch64.
pub mod sync;
+mod time;
-use crate::bsp;
+use crate::{bsp, interface};
use cortex_a::{asm, regs::*};
/// The entry of the `kernel` binary.
@@ -22,7 +23,7 @@
if bsp::BOOT_CORE_ID == MPIDR_EL1.get() & CORE_MASK {
SP.set(bsp::BOOT_CORE_STACK_START);
- crate::relocate::relocate_self::<u64>()
+ crate::runtime_init::runtime_init()
} else {
// If not core0, infinitely wait for events.
wait_forever()
@@ -30,6 +31,12 @@
}
//--------------------------------------------------------------------------------------------------
+// Global instances
+//--------------------------------------------------------------------------------------------------
+
+static TIMER: time::Timer = time::Timer;
+
+//--------------------------------------------------------------------------------------------------
// Implementation of the kernel's architecture abstraction code
//--------------------------------------------------------------------------------------------------
@@ -42,6 +49,11 @@
}
}
+/// Return a reference to a `interface::time::TimeKeeper` implementation.
+pub fn timer() -> &'static impl interface::time::Timer {
+ &TIMER
+}
+
/// Pause execution on the calling CPU core.
#[inline(always)]
pub fn wait_forever() -> ! {
diff -uNr 07_uart_chainloader/src/bsp/driver/bcm/bcm2xxx_pl011_uart.rs 08_timestamps/src/bsp/driver/bcm/bcm2xxx_pl011_uart.rs
--- 07_uart_chainloader/src/bsp/driver/bcm/bcm2xxx_pl011_uart.rs
+++ 08_timestamps/src/bsp/driver/bcm/bcm2xxx_pl011_uart.rs
@@ -298,11 +298,18 @@
arch::nop();
}
+ // Read one character.
+ let mut ret = inner.DR.get() as u8 as char;
+
+ // Convert carrige return to newline.
+ if ret == '\r' {
+ ret = '\n'
+ }
+
// Update statistics.
inner.chars_read += 1;
- // Read one character.
- inner.DR.get() as u8 as char
+ ret
})
}
diff -uNr 07_uart_chainloader/src/bsp/rpi/link.ld 08_timestamps/src/bsp/rpi/link.ld
--- 07_uart_chainloader/src/bsp/rpi/link.ld
+++ 08_timestamps/src/bsp/rpi/link.ld
@@ -5,10 +5,9 @@
SECTIONS
{
- /* Set the link address to the top-most 40 KiB of DRAM (assuming 1GiB) */
- . = 0x3F000000 - 0x10000;
+ /* Set current address to the value from which the RPi starts execution */
+ . = 0x80000;
- __binary_start = .;
.text :
{
*(.text._start) *(.text*)
@@ -32,14 +31,5 @@
__bss_end = .;
}
- .got :
- {
- *(.got*)
- }
-
- /* Fill up to 8 byte, b/c relocating the binary is done in u64 chunks */
- . = ALIGN(8);
- __binary_end = .;
-
/DISCARD/ : { *(.comment*) }
}
diff -uNr 07_uart_chainloader/src/bsp/rpi.rs 08_timestamps/src/bsp/rpi.rs
--- 07_uart_chainloader/src/bsp/rpi.rs
+++ 08_timestamps/src/bsp/rpi.rs
@@ -16,9 +16,6 @@
/// The early boot core's stack address.
pub const BOOT_CORE_STACK_START: u64 = 0x80_000;
-/// The address on which the RPi3 firmware loads every binary by default.
-pub const BOARD_DEFAULT_LOAD_ADDRESS: usize = 0x80_000;
-
//--------------------------------------------------------------------------------------------------
// Global BSP driver instances
//--------------------------------------------------------------------------------------------------
diff -uNr 07_uart_chainloader/src/interface.rs 08_timestamps/src/interface.rs
--- 07_uart_chainloader/src/interface.rs
+++ 08_timestamps/src/interface.rs
@@ -112,3 +112,22 @@
}
}
}
+
+/// Timekeeping interfaces.
+pub mod time {
+ use core::time::Duration;
+
+ /// Timer functions.
+ pub trait Timer {
+ /// 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 07_uart_chainloader/src/main.rs 08_timestamps/src/main.rs
--- 07_uart_chainloader/src/main.rs
+++ 08_timestamps/src/main.rs
@@ -29,11 +29,7 @@
// the first function to run.
mod arch;
-// `_start()` then calls `relocate::relocate_self()`.
-mod relocate;
-
-// `relocate::relocate_self()` calls `runtime_init()`, which on completion, jumps to
-// `kernel_init()`.
+// `_start()` then calls `runtime_init()`, which on completion, jumps to `kernel_init()`.
mod runtime_init;
// Conditionally includes the selected `BSP` code.
@@ -66,50 +62,25 @@
/// The main function running after the early init.
fn kernel_main() -> ! {
- use interface::console::All;
-
- println!(" __ __ _ _ _ _ ");
- println!("| \\/ (_)_ _ (_) | ___ __ _ __| |");
- println!("| |\\/| | | ' \\| | |__/ _ \\/ _` / _` |");
- println!("|_| |_|_|_||_|_|____\\___/\\__,_\\__,_|");
- println!();
- println!("{:^37}", bsp::board_name());
- println!();
- println!("[ML] Requesting binary");
- bsp::console().flush();
-
- // Clear the RX FIFOs, if any, of spurious received characters before starting with the loader
- // protocol.
- bsp::console().clear();
-
- // Notify raspbootcom to send the binary.
- for _ in 0..3 {
- bsp::console().write_char(3 as char);
- }
+ use core::time::Duration;
+ use interface::time::Timer;
- // Read the binary's size.
- let mut size: u32 = u32::from(bsp::console().read_char() as u8);
- size |= u32::from(bsp::console().read_char() as u8) << 8;
- size |= u32::from(bsp::console().read_char() as u8) << 16;
- size |= u32::from(bsp::console().read_char() as u8) << 24;
-
- // Trust it's not too big.
- print!("OK");
-
- let kernel_addr: *mut u8 = bsp::BOARD_DEFAULT_LOAD_ADDRESS as *mut u8;
- unsafe {
- // Read the kernel byte by byte.
- for i in 0..size {
- *kernel_addr.offset(i as isize) = bsp::console().read_char() as u8;
- }
+ info!("Booting on: {}", bsp::board_name());
+ info!(
+ "Architectural timer resolution: {} ns",
+ arch::timer().resolution().as_nanos()
+ );
+
+ info!("Drivers loaded:");
+ for (i, driver) in bsp::device_drivers().iter().enumerate() {
+ info!(" {}. {}", i + 1, driver.compatible());
}
- println!("[ML] Loaded! Executing the payload now\n");
- bsp::console().flush();
-
- // Use black magic to get a function pointer.
- let kernel: extern "C" fn() -> ! = unsafe { core::mem::transmute(kernel_addr as *const ()) };
+ // Test a failing timer case.
+ arch::timer().spin_for(Duration::from_nanos(1));
- // Jump to loaded kernel!
- kernel()
+ loop {
+ info!("Spinning for 1 second");
+ arch::timer().spin_for(Duration::from_secs(1));
+ }
}
diff -uNr 07_uart_chainloader/src/print.rs 08_timestamps/src/print.rs
--- 07_uart_chainloader/src/print.rs
+++ 08_timestamps/src/print.rs
@@ -32,3 +32,71 @@
$crate::print::_print(format_args_nl!($($arg)*));
})
}
+
+/// Prints an info, with newline.
+#[macro_export]
+macro_rules! info {
+ ($string:expr) => ({
+ #[allow(unused_imports)]
+ use crate::interface::time::Timer;
+
+ let timestamp = $crate::arch::timer().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::interface::time::Timer;
+
+ let timestamp = $crate::arch::timer().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 newline.
+#[macro_export]
+macro_rules! warn {
+ ($string:expr) => ({
+ #[allow(unused_imports)]
+ use crate::interface::time::Timer;
+
+ let timestamp = $crate::arch::timer().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::interface::time::Timer;
+
+ let timestamp = $crate::arch::timer().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 07_uart_chainloader/src/relocate.rs 08_timestamps/src/relocate.rs
--- 07_uart_chainloader/src/relocate.rs
+++ 08_timestamps/src/relocate.rs
@@ -1,46 +0,0 @@
-// SPDX-License-Identifier: MIT OR Apache-2.0
-//
-// Copyright (c) 2018-2019 Andre Richter <andre.o.richter@gmail.com>
-
-//! Relocation code.
-
-/// Relocates the own binary from `bsp::BOARD_DEFAULT_LOAD_ADDRESS` to the `__binary_start` address
-/// from the linker script.
-///
-/// # Safety
-///
-/// - Only a single core must be active and running this function.
-/// - Function must not use the `bss` section.
-pub unsafe fn relocate_self<T>() -> ! {
- extern "C" {
- static __binary_start: usize;
- static __binary_end: usize;
- }
-
- let binary_start_addr: usize = &__binary_start as *const _ as _;
- let binary_end_addr: usize = &__binary_end as *const _ as _;
- let binary_size_in_byte: usize = binary_end_addr - binary_start_addr;
-
- // Get the relocation destination address from the linker symbol.
- let mut reloc_dst_addr: *mut T = binary_start_addr as *mut T;
-
- // The address of where the previous firmware loaded us.
- let mut src_addr: *const T = crate::bsp::BOARD_DEFAULT_LOAD_ADDRESS as *const _;
-
- // Copy the whole binary.
- //
- // This is essentially a `memcpy()` optimized for throughput by transferring in chunks of T.
- let n = binary_size_in_byte / core::mem::size_of::<T>();
- for _ in 0..n {
- use core::ptr;
-
- ptr::write_volatile::<T>(reloc_dst_addr, ptr::read_volatile::<T>(src_addr));
- reloc_dst_addr = reloc_dst_addr.offset(1);
- src_addr = src_addr.offset(1);
- }
-
- // Call `init()` through a trait object, causing the jump to use an absolute address to reach
- // the relocated binary. An elaborate explanation can be found in the runtime_init.rs source
- // comments.
- crate::runtime_init::get().runtime_init()
-}
diff -uNr 07_uart_chainloader/src/runtime_init.rs 08_timestamps/src/runtime_init.rs
--- 07_uart_chainloader/src/runtime_init.rs
+++ 08_timestamps/src/runtime_init.rs
@@ -4,39 +4,21 @@
//! Rust runtime initialization code.
-/// We are outsmarting the compiler here by using a trait as a layer of indirection. Because we are
-/// generating PIC code, a static dispatch to `init()` would generate a relative jump from the
-/// callee to `init()`. However, when calling `init()`, code just finished copying the binary to the
-/// actual link-time address, and hence is still running at whatever location the previous loader
-/// has put it. So we do not want a relative jump, because it would not jump to the relocated code.
+/// Equivalent to `crt0` or `c0` code in C/C++ world. Clears the `bss` section, then jumps to kernel
+/// init code.
///
-/// By indirecting through a trait object, we can make use of the property that vtables store
-/// absolute addresses. So calling `init()` this way will kick execution to the relocated binary.
-pub trait RunTimeInit {
- /// Equivalent to `crt0` or `c0` code in C/C++ world. Clears the `bss` section, then jumps to
- /// kernel init code.
- ///
- /// # Safety
- ///
- /// - Only a single core must be active and running this function.
- unsafe fn runtime_init(&self) -> ! {
- extern "C" {
- // Boundaries of the .bss section, provided by the linker script.
- static mut __bss_start: u64;
- static mut __bss_end: u64;
- }
-
- // Zero out the .bss section.
- r0::zero_bss(&mut __bss_start, &mut __bss_end);
-
- crate::kernel_init()
+/// # Safety
+///
+/// - Only a single core must be active and running this function.
+pub unsafe fn runtime_init() -> ! {
+ extern "C" {
+ // Boundaries of the .bss section, provided by the linker script.
+ static mut __bss_start: u64;
+ static mut __bss_end: u64;
}
-}
-struct Traitor;
-impl RunTimeInit for Traitor {}
+ // Zero out the .bss section.
+ r0::zero_bss(&mut __bss_start, &mut __bss_end);
-/// Give the callee a `RunTimeInit` trait object.
-pub fn get() -> &'static dyn RunTimeInit {
- &Traitor {}
+ crate::kernel_init()
}
```
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