Use addr_of_mut! to access static muts.

Newer versions of Rust disallow taking a
&mut reference on static mut variables.

defmt-ringbuf/defmt-ringbuf-test/src/main.rs

@@ -1,7 +1,7 @@
 #![no_std]
 #![no_main]
 
-use core::mem;
+use core::{mem, ptr::addr_of_mut};
 use cortex_m::{asm::nop, peripheral::SCB};
 use cortex_m_rt::entry;
 
@@ -20,7 +20,9 @@ fn main() -> ! {
     let _dp = Peripherals::take().unwrap();
 
     defmt::info!("Init");
-    let buffer = unsafe { RingBuffer::init(&mut BUFFER) };
+
+    // Safety: BUFFER is only accessed here and nowhere else.
+    let buffer = unsafe { RingBuffer::init(&mut *addr_of_mut!(BUFFER)) };
 
     let mut data = [0; 128];
     let (n, lost) = buffer.read(&mut data);

defmt-ringbuf/src/lib.rs

@@ -114,8 +114,7 @@ fn do_write(data: &[u8]) {
 /// This must be called exactly once.
 /// Log messages received before initiailization are discarded.
 pub unsafe fn init<const SIZE: usize>(
-    ring_buffer: &'static mut MaybeUninit<RingBuffer<SIZE>>,
-    log_available: fn(),
+    ring_buffer: &'static mut MaybeUninit<RingBuffer<SIZE>>, log_available: fn(),
 ) {
     defmt::assert!(RING_BUFFER.is_none());
 

openemc-bootloader/src/main.rs

@@ -140,7 +140,9 @@ fn main() -> ! {
     // Initialize logging.
     #[cfg(feature = "defmt-ringbuf")]
     unsafe {
-        defmt_ringbuf::init(&mut BOOTLOADER_LOG, || ());
+        use core::ptr::addr_of_mut;
+        // Safety: BOOTLOADER_LOG is only accessed here and nowhere else while the bootloader is running.
+        defmt_ringbuf::init(&mut *addr_of_mut!(BOOTLOADER_LOG), || ());
     }
 
     // Enable backup domain and check for valid signature.

openemc-firmware/src/boot.rs

@@ -5,6 +5,7 @@ use core::{
     ptr,
     ptr::{addr_of, addr_of_mut},
     slice,
+    sync::atomic::{AtomicBool, Ordering},
 };
 use cortex_m::peripheral::{scb::Exception, SCB};
 use stm32f1::stm32f103::Peripherals;
@@ -82,8 +83,13 @@ pub trait BootInfoExt {
     fn bootloader_version(&self) -> Option<&[u8]>;
 }
 
+/// Whether boot information has been initialized.
+static BOOT_INFO_INITIALIZED: AtomicBool = AtomicBool::new(false);
+
 impl BootInfoExt for BootInfo {
     unsafe fn init(bkp: &BackupDomain) {
+        defmt::assert!(!BOOT_INFO_INITIALIZED.load(Ordering::SeqCst));
+
         // Make sure BOOT_INFO is read from memory.
         let ptr = BOOT_INFO.as_mut_ptr();
         let powered_on_ptr = addr_of_mut!((*ptr).powered_on) as *mut u8;
@@ -107,13 +113,19 @@ impl BootInfoExt for BootInfo {
             // Get boot reason.
             STANDALONE_BOOT_INFO.boot_reason = BootReason::get(bkp);
         }
+
+        BOOT_INFO_INITIALIZED.store(true, Ordering::SeqCst);
     }
 
     fn get() -> &'static Self {
+        defmt::assert!(BOOT_INFO_INITIALIZED.load(Ordering::SeqCst));
+
         if Self::is_from_bootloader() {
+            // Safety: BOOT_INFO has been verified during init()
             unsafe { BOOT_INFO.assume_init_ref() }
         } else {
-            unsafe { &STANDALONE_BOOT_INFO }
+            // Safety: STANDALONE_BOOT_INFO is only modified during init()
+            unsafe { &*ptr::addr_of!(STANDALONE_BOOT_INFO) }
         }
     }
 

openemc-firmware/src/main.rs

@@ -348,8 +348,11 @@ mod app {
         // Initialize logging.
         #[cfg(feature = "defmt-ringbuf")]
         unsafe {
-            defmt_ringbuf::init(&mut LOG, || NVIC::pend(Interrupt::USART3));
-            BOOTLOADER_LOG_REF = Some(defmt_ringbuf::RingBuffer::init(&mut BOOTLOADER_LOG));
+            use core::ptr::addr_of_mut;
+            // Safety: LOG is only accessed here and nowhere else.
+            defmt_ringbuf::init(&mut *addr_of_mut!(LOG), || NVIC::pend(Interrupt::USART3));
+            // Safety: BOOTLOADER_LOG is only accessed here and nowhere else.
+            BOOTLOADER_LOG_REF = Some(defmt_ringbuf::RingBuffer::init(&mut *addr_of_mut!(BOOTLOADER_LOG)));
         }
 
         defmt::warn!("OpenEMC version {:a}", VERSION);

scripts/crates-fmt.sh

@@ -14,6 +14,8 @@ cargo +nightly fmt --manifest-path openemc-firmware/Cargo.toml
 cargo +nightly fmt --manifest-path openemc-shared/Cargo.toml
 cargo +nightly fmt --manifest-path openemc-log/Cargo.toml
 cargo +nightly fmt --manifest-path xtask/Cargo.toml
+cargo +nightly fmt --manifest-path defmt-ringbuf/Cargo.toml
+cargo +nightly fmt --manifest-path defmt-ringbuf/defmt-ringbuf-test/Cargo.toml
 
 rustup run nightly rustfmt openemc-bootloader/src/boards/*.rs
 rustup run nightly rustfmt openemc-firmware/src/boards/*.rs