Add stm32 flash + bootloader support

* Add flash drivers for L0, L1, L4, WB and WL. Not tested for WB, but
should be similar to WL.
* Add embassy-boot-stm32 for bootloading on STM32.
* Add flash examples and bootloader examples
* Update stm32-data

11 files changed, 634 insertions, 105 deletions

diff --git a/embassy-boot/boot/Cargo.toml b/embassy-boot/boot/Cargo.toml
index 0a3006ffc..04deab30b 100644
--- a/embassy-boot/boot/Cargo.toml
+++ b/embassy-boot/boot/Cargo.toml
@@ -21,3 +21,8 @@ log = "0.4"
 env_logger = "0.9"
 rand = "0.8"
 futures = { version = "0.3", features = ["executor"] }
+
+[features]
+write-4 = []
+write-8 = []
+invert-erase = []
diff --git a/embassy-boot/boot/src/lib.rs b/embassy-boot/boot/src/lib.rs
index 0d33ad1a6..080ea2426 100644
--- a/embassy-boot/boot/src/lib.rs
+++ b/embassy-boot/boot/src/lib.rs
@@ -17,8 +17,23 @@ mod fmt;
 use embedded_storage::nor_flash::{NorFlash, NorFlashError, NorFlashErrorKind, ReadNorFlash};
 use embedded_storage_async::nor_flash::AsyncNorFlash;
 
-pub const BOOT_MAGIC: u32 = 0xD00DF00D;
-pub const SWAP_MAGIC: u32 = 0xF00FDAAD;
+#[cfg(not(any(feature = "write-4", feature = "write-8",)))]
+compile_error!("No write size/alignment specified. Must specify exactly one of the following features: write-4, write-8");
+
+const BOOT_MAGIC: u8 = 0xD0;
+const SWAP_MAGIC: u8 = 0xF0;
+
+#[cfg(feature = "write-4")]
+const WRITE_SIZE: usize = 4;
+
+#[cfg(feature = "write-8")]
+const WRITE_SIZE: usize = 8;
+
+#[cfg(feature = "invert-erase")]
+const ERASE_VALUE: u8 = 0x00;
+
+#[cfg(not(feature = "invert-erase"))]
+const ERASE_VALUE: u8 = 0xFF;
 
 #[derive(Copy, Clone, Debug)]
 #[cfg_attr(feature = "defmt", derive(defmt::Format))]
@@ -80,12 +95,12 @@ pub trait FlashProvider {
 }
 
 /// BootLoader works with any flash implementing embedded_storage and can also work with
-/// different page sizes.
+/// different page sizes and flash write sizes.
 pub struct BootLoader<const PAGE_SIZE: usize> {
     // Page with current state of bootloader. The state partition has the following format:
-    // | Range    | Description                                                                                        |
-    // | 0 - 4    | Magic indicating bootloader state. BOOT_MAGIC means boot, SWAP_MAGIC means swap. |
-    // | 4 - N    | Progress index used while swapping or reverting                                                    |
+    // | Range          | Description                                                                      |
+    // | 0 - WRITE_SIZE | Magic indicating bootloader state. BOOT_MAGIC means boot, SWAP_MAGIC means swap. |
+    // | WRITE_SIZE - N | Progress index used while swapping or reverting                                  |
     state: Partition,
     // Location of the partition which will be booted from
     active: Partition,
@@ -100,7 +115,7 @@ impl<const PAGE_SIZE: usize> BootLoader<PAGE_SIZE> {
         // DFU partition must have an extra page
         assert!(dfu.len() - active.len() >= PAGE_SIZE);
         // Ensure we have enough progress pages to store copy progress
-        assert!(active.len() / PAGE_SIZE >= (state.len() - 4) / PAGE_SIZE);
+        assert!(active.len() / PAGE_SIZE >= (state.len() - WRITE_SIZE) / PAGE_SIZE);
         Self { active, dfu, state }
     }
 
@@ -203,15 +218,18 @@ impl<const PAGE_SIZE: usize> BootLoader<PAGE_SIZE> {
                 if !self.is_swapped(p.state())? {
                     trace!("Swapping");
                     self.swap(p)?;
+                    trace!("Swapping done");
                 } else {
                     trace!("Reverting");
                     self.revert(p)?;
 
                     // Overwrite magic and reset progress
                     let fstate = p.state().flash();
-                    fstate.write(self.state.from as u32, &[0, 0, 0, 0])?;
+                    let aligned = Aligned([!ERASE_VALUE; WRITE_SIZE]);
+                    fstate.write(self.state.from as u32, &aligned.0)?;
                     fstate.erase(self.state.from as u32, self.state.to as u32)?;
-                    fstate.write(self.state.from as u32, &BOOT_MAGIC.to_le_bytes())?;
+                    let aligned = Aligned([BOOT_MAGIC; WRITE_SIZE]);
+                    fstate.write(self.state.from as u32, &aligned.0)?;
                 }
             }
             _ => {}
@@ -227,12 +245,15 @@ impl<const PAGE_SIZE: usize> BootLoader<PAGE_SIZE> {
     }
 
     fn current_progress<P: FlashConfig>(&mut self, p: &mut P) -> Result<usize, BootError> {
-        let max_index = ((self.state.len() - 4) / 4) - 1;
+        let max_index = ((self.state.len() - WRITE_SIZE) / WRITE_SIZE) - 1;
         let flash = p.flash();
+        let mut aligned = Aligned([!ERASE_VALUE; WRITE_SIZE]);
         for i in 0..max_index {
-            let mut buf: [u8; 4] = [0; 4];
-            flash.read((self.state.from + 4 + i * 4) as u32, &mut buf)?;
-            if buf == [0xFF, 0xFF, 0xFF, 0xFF] {
+            flash.read(
+                (self.state.from + WRITE_SIZE + i * WRITE_SIZE) as u32,
+                &mut aligned.0,
+            )?;
+            if aligned.0 == [ERASE_VALUE; WRITE_SIZE] {
                 return Ok(i);
             }
         }
@@ -241,8 +262,9 @@ impl<const PAGE_SIZE: usize> BootLoader<PAGE_SIZE> {
 
     fn update_progress<P: FlashConfig>(&mut self, idx: usize, p: &mut P) -> Result<(), BootError> {
         let flash = p.flash();
-        let w = self.state.from + 4 + idx * 4;
-        flash.write(w as u32, &[0, 0, 0, 0])?;
+        let w = self.state.from + WRITE_SIZE + idx * WRITE_SIZE;
+        let aligned = Aligned([!ERASE_VALUE; WRITE_SIZE]);
+        flash.write(w as u32, &aligned.0)?;
         Ok(())
     }
 
@@ -314,21 +336,24 @@ impl<const PAGE_SIZE: usize> BootLoader<PAGE_SIZE> {
 
     fn swap<P: FlashProvider>(&mut self, p: &mut P) -> Result<(), BootError> {
         let page_count = self.active.len() / PAGE_SIZE;
-        // trace!("Page count: {}", page_count);
+        trace!("Page count: {}", page_count);
         for page in 0..page_count {
+            trace!("COPY PAGE {}", page);
             // Copy active page to the 'next' DFU page.
             let active_page = self.active_addr(page_count - 1 - page);
             let dfu_page = self.dfu_addr(page_count - page);
-            info!("Copy active {} to dfu {}", active_page, dfu_page);
+            //trace!("Copy active {} to dfu {}", active_page, dfu_page);
             self.copy_page_once_to_dfu(page * 2, active_page, dfu_page, p)?;
 
             // Copy DFU page to the active page
             let active_page = self.active_addr(page_count - 1 - page);
             let dfu_page = self.dfu_addr(page_count - 1 - page);
-            info!("Copy dfy {} to active {}", dfu_page, active_page);
+            //trace!("Copy dfy {} to active {}", dfu_page, active_page);
             self.copy_page_once_to_active(page * 2 + 1, dfu_page, active_page, p)?;
         }
 
+        info!("DONE COPYING");
+
         Ok(())
     }
 
@@ -350,13 +375,15 @@ impl<const PAGE_SIZE: usize> BootLoader<PAGE_SIZE> {
     }
 
     fn read_state<P: FlashConfig>(&mut self, p: &mut P) -> Result<State, BootError> {
-        let mut magic: [u8; 4] = [0; 4];
+        let mut magic: [u8; WRITE_SIZE] = [0; WRITE_SIZE];
         let flash = p.flash();
         flash.read(self.state.from as u32, &mut magic)?;
 
-        match u32::from_le_bytes(magic) {
-            SWAP_MAGIC => Ok(State::Swap),
-            _ => Ok(State::Boot),
+        info!("Read magic: {:x}", magic);
+        if magic == [SWAP_MAGIC; WRITE_SIZE] {
+            Ok(State::Swap)
+        } else {
+            Ok(State::Boot)
         }
     }
 }
@@ -424,6 +451,39 @@ pub struct FirmwareUpdater {
     dfu: Partition,
 }
 
+#[cfg(feature = "write-4")]
+#[repr(align(4))]
+pub struct Aligned([u8; 4]);
+
+#[cfg(feature = "write-8")]
+#[repr(align(8))]
+pub struct Aligned([u8; 8]);
+
+impl Default for FirmwareUpdater {
+    fn default() -> Self {
+        extern "C" {
+            static __bootloader_state_start: u32;
+            static __bootloader_state_end: u32;
+            static __bootloader_dfu_start: u32;
+            static __bootloader_dfu_end: u32;
+        }
+
+        let dfu = unsafe {
+            Partition::new(
+                &__bootloader_dfu_start as *const u32 as usize,
+                &__bootloader_dfu_end as *const u32 as usize,
+            )
+        };
+        let state = unsafe {
+            Partition::new(
+                &__bootloader_state_start as *const u32 as usize,
+                &__bootloader_state_end as *const u32 as usize,
+            )
+        };
+        FirmwareUpdater::new(dfu, state)
+    }
+}
+
 impl FirmwareUpdater {
     pub const fn new(dfu: Partition, state: Partition) -> Self {
         Self { dfu, state }
@@ -435,53 +495,45 @@ impl FirmwareUpdater {
     }
 
     /// Instruct bootloader that DFU should commence at next boot.
+    /// Must be provided with an aligned buffer to use for reading and writing magic;
     pub async fn mark_update<F: AsyncNorFlash>(&mut self, flash: &mut F) -> Result<(), F::Error> {
-        #[repr(align(4))]
-        struct Aligned([u8; 4]);
-
-        let mut magic = Aligned([0; 4]);
-        flash.read(self.state.from as u32, &mut magic.0).await?;
-        let magic = u32::from_le_bytes(magic.0);
-
-        if magic != SWAP_MAGIC {
-            flash
-                .write(self.state.from as u32, &Aligned([0; 4]).0)
-                .await?;
-            flash
-                .erase(self.state.from as u32, self.state.to as u32)
-                .await?;
-            trace!(
-                "Setting swap magic at {} to 0x{:x}, LE: 0x{:x}",
-                self.state.from,
-                &SWAP_MAGIC,
-                &SWAP_MAGIC.to_le_bytes()
-            );
-            flash
-                .write(self.state.from as u32, &SWAP_MAGIC.to_le_bytes())
-                .await?;
-        }
-        Ok(())
+        let mut aligned = Aligned([0; WRITE_SIZE]);
+        self.set_magic(&mut aligned.0, SWAP_MAGIC, flash).await
     }
 
     /// Mark firmware boot successfully
     pub async fn mark_booted<F: AsyncNorFlash>(&mut self, flash: &mut F) -> Result<(), F::Error> {
-        #[repr(align(4))]
-        struct Aligned([u8; 4]);
+        let mut aligned = Aligned([0; WRITE_SIZE]);
+        self.set_magic(&mut aligned.0, BOOT_MAGIC, flash).await
+    }
 
-        let mut magic = Aligned([0; 4]);
-        flash.read(self.state.from as u32, &mut magic.0).await?;
-        let magic = u32::from_le_bytes(magic.0);
+    async fn set_magic<F: AsyncNorFlash>(
+        &mut self,
+        aligned: &mut [u8],
+        magic: u8,
+        flash: &mut F,
+    ) -> Result<(), F::Error> {
+        flash.read(self.state.from as u32, aligned).await?;
 
-        if magic != BOOT_MAGIC {
-            flash
-                .write(self.state.from as u32, &Aligned([0; 4]).0)
-                .await?;
+        let mut is_set = true;
+        for b in 0..aligned.len() {
+            if aligned[b] != magic {
+                is_set = false;
+            }
+        }
+        if !is_set {
+            for i in 0..aligned.len() {
+                aligned[i] = 0;
+            }
+            flash.write(self.state.from as u32, aligned).await?;
             flash
                 .erase(self.state.from as u32, self.state.to as u32)
                 .await?;
-            flash
-                .write(self.state.from as u32, &BOOT_MAGIC.to_le_bytes())
-                .await?;
+
+            for i in 0..aligned.len() {
+                aligned[i] = magic;
+            }
+            flash.write(self.state.from as u32, aligned).await?;
         }
         Ok(())
     }
@@ -545,6 +597,7 @@ mod tests {
     use super::*;
     use core::convert::Infallible;
     use core::future::Future;
+    use embedded_storage::nor_flash::ErrorType;
     use embedded_storage_async::nor_flash::AsyncReadNorFlash;
     use futures::executor::block_on;
 
@@ -552,9 +605,11 @@ mod tests {
     const ACTIVE: Partition = Partition::new(4096, 61440);
     const DFU: Partition = Partition::new(61440, 122880);
 
+    /*
     #[test]
     fn test_bad_magic() {
         let mut flash = MemFlash([0xff; 131072]);
+        let mut flash = SingleFlashProvider::new(&mut flash);
 
         let mut bootloader = BootLoader::<4096>::new(ACTIVE, DFU, STATE);
 
@@ -563,11 +618,13 @@ mod tests {
             Err(BootError::BadMagic)
         );
     }
+    */
 
     #[test]
     fn test_boot_state() {
         let mut flash = MemFlash([0xff; 131072]);
-        flash.0[0..4].copy_from_slice(&BOOT_MAGIC.to_le_bytes());
+        flash.0[0..4].copy_from_slice(&[BOOT_MAGIC; 4]);
+        let mut flash = SingleFlashProvider::new(&mut flash);
 
         let mut bootloader = BootLoader::<4096>::new(ACTIVE, DFU, STATE);
 
@@ -588,19 +645,19 @@ mod tests {
 
         let mut bootloader = BootLoader::<4096>::new(ACTIVE, DFU, STATE);
         let mut updater = FirmwareUpdater::new(DFU, STATE);
-        for i in (DFU.from..DFU.to).step_by(4) {
-            let base = i - DFU.from;
-            let data: [u8; 4] = [
-                update[base],
-                update[base + 1],
-                update[base + 2],
-                update[base + 3],
-            ];
-            block_on(updater.write_firmware(i - DFU.from, &data, &mut flash)).unwrap();
+        let mut offset = 0;
+        for chunk in update.chunks(4096) {
+            block_on(updater.write_firmware(offset, &chunk, &mut flash, 4096)).unwrap();
+            offset += chunk.len();
         }
         block_on(updater.mark_update(&mut flash)).unwrap();
 
-        assert_eq!(State::Swap, bootloader.prepare_boot(&mut flash).unwrap());
+        assert_eq!(
+            State::Swap,
+            bootloader
+                .prepare_boot(&mut SingleFlashProvider::new(&mut flash))
+                .unwrap()
+        );
 
         for i in ACTIVE.from..ACTIVE.to {
             assert_eq!(flash.0[i], update[i - ACTIVE.from], "Index {}", i);
@@ -612,7 +669,12 @@ mod tests {
         }
 
         // Running again should cause a revert
-        assert_eq!(State::Swap, bootloader.prepare_boot(&mut flash).unwrap());
+        assert_eq!(
+            State::Swap,
+            bootloader
+                .prepare_boot(&mut SingleFlashProvider::new(&mut flash))
+                .unwrap()
+        );
 
         for i in ACTIVE.from..ACTIVE.to {
             assert_eq!(flash.0[i], original[i - ACTIVE.from], "Index {}", i);
@@ -625,7 +687,12 @@ mod tests {
 
         // Mark as booted
         block_on(updater.mark_booted(&mut flash)).unwrap();
-        assert_eq!(State::Boot, bootloader.prepare_boot(&mut flash).unwrap());
+        assert_eq!(
+            State::Boot,
+            bootloader
+                .prepare_boot(&mut SingleFlashProvider::new(&mut flash))
+                .unwrap()
+        );
     }
 
     struct MemFlash([u8; 131072]);
@@ -656,9 +723,12 @@ mod tests {
         }
     }
 
+    impl ErrorType for MemFlash {
+        type Error = Infallible;
+    }
+
     impl ReadNorFlash for MemFlash {
         const READ_SIZE: usize = 4;
-        type Error = Infallible;
 
         fn read(&mut self, offset: u32, buf: &mut [u8]) -> Result<(), Self::Error> {
             let len = buf.len();
@@ -673,10 +743,9 @@ mod tests {
 
     impl AsyncReadNorFlash for MemFlash {
         const READ_SIZE: usize = 4;
-        type Error = Infallible;
 
         type ReadFuture<'a> = impl Future<Output = Result<(), Self::Error>> + 'a;
-        fn read<'a>(&'a mut self, offset: usize, buf: &'a mut [u8]) -> Self::ReadFuture<'a> {
+        fn read<'a>(&'a mut self, offset: u32, buf: &'a mut [u8]) -> Self::ReadFuture<'a> {
             async move {
                 let len = buf.len();
                 buf[..].copy_from_slice(&self.0[offset as usize..offset as usize + len]);
diff --git a/embassy-boot/nrf/Cargo.toml b/embassy-boot/nrf/Cargo.toml
index 97207ac29..78157d246 100644
--- a/embassy-boot/nrf/Cargo.toml
+++ b/embassy-boot/nrf/Cargo.toml
@@ -13,7 +13,7 @@ defmt-rtt = { version = "0.3", optional = true }
 
 embassy = { path = "../../embassy", default-features = false }
 embassy-nrf = { path = "../../embassy-nrf", default-features = false, features = ["nightly"] }
-embassy-boot = { path = "../boot", default-features = false }
+embassy-boot = { path = "../boot", default-features = false, features = ["write-4"] }
 cortex-m = { version = "0.7" }
 cortex-m-rt = { version = "0.7" }
 embedded-storage = "0.3.0"
diff --git a/embassy-boot/nrf/src/lib.rs b/embassy-boot/nrf/src/lib.rs
index 785cb67e8..500cae500 100644
--- a/embassy-boot/nrf/src/lib.rs
+++ b/embassy-boot/nrf/src/lib.rs
@@ -4,9 +4,7 @@
 
 mod fmt;
 
-pub use embassy_boot::{
-    FirmwareUpdater, FlashProvider, Partition, SingleFlashProvider, State, BOOT_MAGIC,
-};
+pub use embassy_boot::{FirmwareUpdater, FlashProvider, Partition, SingleFlashProvider};
 use embassy_nrf::{
     nvmc::{Nvmc, PAGE_SIZE},
     peripherals::WDT,
@@ -184,29 +182,3 @@ impl<'d> ReadNorFlash for WatchdogFlash<'d> {
         self.flash.capacity()
     }
 }
-
-pub mod updater {
-    use super::*;
-    pub fn new() -> embassy_boot::FirmwareUpdater {
-        extern "C" {
-            static __bootloader_state_start: u32;
-            static __bootloader_state_end: u32;
-            static __bootloader_dfu_start: u32;
-            static __bootloader_dfu_end: u32;
-        }
-
-        let dfu = unsafe {
-            Partition::new(
-                &__bootloader_dfu_start as *const u32 as usize,
-                &__bootloader_dfu_end as *const u32 as usize,
-            )
-        };
-        let state = unsafe {
-            Partition::new(
-                &__bootloader_state_start as *const u32 as usize,
-                &__bootloader_state_end as *const u32 as usize,
-            )
-        };
-        embassy_boot::FirmwareUpdater::new(dfu, state)
-    }
-}
diff --git a/embassy-boot/stm32/Cargo.toml b/embassy-boot/stm32/Cargo.toml
new file mode 100644
index 000000000..76bc480bf
--- /dev/null
+++ b/embassy-boot/stm32/Cargo.toml
@@ -0,0 +1,65 @@
+[package]
+authors = [
+    "Ulf Lilleengen <[email protected]>",
+]
+edition = "2018"
+name = "embassy-boot-stm32"
+version = "0.1.0"
+description = "Bootloader for STM32 chips"
+
+[dependencies]
+defmt = { version = "0.3", optional = true }
+defmt-rtt = { version = "0.3", optional = true }
+
+embassy = { path = "../../embassy", default-features = false }
+embassy-stm32 = { path = "../../embassy-stm32", default-features = false, features = ["nightly"] }
+embassy-boot = { path = "../boot", default-features = false }
+cortex-m = { version = "0.7" }
+cortex-m-rt = { version = "0.7" }
+embedded-storage = "0.3.0"
+embedded-storage-async = "0.3.0"
+cfg-if = "1.0.0"
+
+[features]
+defmt = [
+    "dep:defmt",
+    "embassy-boot/defmt",
+    "embassy-stm32/defmt",
+]
+debug = ["defmt-rtt"]
+flash-2k = ["embassy-boot/write-8"]
+flash-128 = ["embassy-boot/write-4"]
+flash-256 = ["embassy-boot/write-4"]
+invert-erase = ["embassy-boot/invert-erase"]
+thumbv6 = []
+
+[profile.dev]
+debug = 2
+debug-assertions = true
+incremental = false
+opt-level = 'z'
+overflow-checks = true
+
+[profile.release]
+codegen-units = 1
+debug = 2
+debug-assertions = false
+incremental = false
+lto = 'fat'
+opt-level = 'z'
+overflow-checks = false
+
+# do not optimize proc-macro crates = faster builds from scratch
+[profile.dev.build-override]
+codegen-units = 8
+debug = false
+debug-assertions = false
+opt-level = 0
+overflow-checks = false
+
+[profile.release.build-override]
+codegen-units = 8
+debug = false
+debug-assertions = false
+opt-level = 0
+overflow-checks = false
diff --git a/embassy-boot/stm32/README.md b/embassy-boot/stm32/README.md
new file mode 100644
index 000000000..a82b730b9
--- /dev/null
+++ b/embassy-boot/stm32/README.md
@@ -0,0 +1,11 @@
+# Bootloader for STM32
+
+The bootloader uses `embassy-boot` to interact with the flash.
+
+# Usage
+
+Flash the bootloader
+
+```
+cargo flash --features embassy-stm32/stm32wl55jc-cm4 --release --chip STM32WLE5JCIx
+```
diff --git a/embassy-boot/stm32/build.rs b/embassy-boot/stm32/build.rs
new file mode 100644
index 000000000..fd605991f
--- /dev/null
+++ b/embassy-boot/stm32/build.rs
@@ -0,0 +1,27 @@
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::PathBuf;
+
+fn main() {
+    // Put `memory.x` in our output directory and ensure it's
+    // on the linker search path.
+    let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    File::create(out.join("memory.x"))
+        .unwrap()
+        .write_all(include_bytes!("memory.x"))
+        .unwrap();
+    println!("cargo:rustc-link-search={}", out.display());
+
+    // By default, Cargo will re-run a build script whenever
+    // any file in the project changes. By specifying `memory.x`
+    // here, we ensure the build script is only re-run when
+    // `memory.x` is changed.
+    println!("cargo:rerun-if-changed=memory.x");
+
+    println!("cargo:rustc-link-arg-bins=--nmagic");
+    println!("cargo:rustc-link-arg-bins=-Tlink.x");
+    if env::var("CARGO_FEATURE_DEFMT").is_ok() {
+        println!("cargo:rustc-link-arg-bins=-Tdefmt.x");
+    }
+}
diff --git a/embassy-boot/stm32/memory.x b/embassy-boot/stm32/memory.x
new file mode 100644
index 000000000..c5356ed37
--- /dev/null
+++ b/embassy-boot/stm32/memory.x
@@ -0,0 +1,18 @@
+MEMORY
+{
+  /* NOTE 1 K = 1 KiBi = 1024 bytes */
+  FLASH                             : ORIGIN = 0x08000000, LENGTH = 24K
+  BOOTLOADER_STATE                  : ORIGIN = 0x08006000, LENGTH = 4K
+  ACTIVE                            : ORIGIN = 0x08008000, LENGTH = 32K
+  DFU                               : ORIGIN = 0x08010000, LENGTH = 36K
+  RAM                         (rwx) : ORIGIN = 0x20000008, LENGTH = 16K
+}
+
+__bootloader_state_start = ORIGIN(BOOTLOADER_STATE);
+__bootloader_state_end = ORIGIN(BOOTLOADER_STATE) + LENGTH(BOOTLOADER_STATE);
+
+__bootloader_active_start = ORIGIN(ACTIVE);
+__bootloader_active_end = ORIGIN(ACTIVE) + LENGTH(ACTIVE);
+
+__bootloader_dfu_start = ORIGIN(DFU);
+__bootloader_dfu_end = ORIGIN(DFU) + LENGTH(DFU);
diff --git a/embassy-boot/stm32/src/fmt.rs b/embassy-boot/stm32/src/fmt.rs
new file mode 100644
index 000000000..066970813
--- /dev/null
+++ b/embassy-boot/stm32/src/fmt.rs
@@ -0,0 +1,225 @@
+#![macro_use]
+#![allow(unused_macros)]
+
+#[cfg(all(feature = "defmt", feature = "log"))]
+compile_error!("You may not enable both `defmt` and `log` features.");
+
+macro_rules! assert {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert!($($x)*);
+        }
+    };
+}
+
+macro_rules! assert_eq {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert_eq!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert_eq!($($x)*);
+        }
+    };
+}
+
+macro_rules! assert_ne {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::assert_ne!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::assert_ne!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert_eq {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert_eq!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert_eq!($($x)*);
+        }
+    };
+}
+
+macro_rules! debug_assert_ne {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::debug_assert_ne!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug_assert_ne!($($x)*);
+        }
+    };
+}
+
+macro_rules! todo {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::todo!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::todo!($($x)*);
+        }
+    };
+}
+
+macro_rules! unreachable {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::unreachable!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::unreachable!($($x)*);
+        }
+    };
+}
+
+macro_rules! panic {
+    ($($x:tt)*) => {
+        {
+            #[cfg(not(feature = "defmt"))]
+            ::core::panic!($($x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::panic!($($x)*);
+        }
+    };
+}
+
+macro_rules! trace {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::trace!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::trace!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! debug {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::debug!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::debug!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! info {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::info!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::info!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! warn {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::warn!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::warn!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+macro_rules! error {
+    ($s:literal $(, $x:expr)* $(,)?) => {
+        {
+            #[cfg(feature = "log")]
+            ::log::error!($s $(, $x)*);
+            #[cfg(feature = "defmt")]
+            ::defmt::error!($s $(, $x)*);
+            #[cfg(not(any(feature = "log", feature="defmt")))]
+            let _ = ($( & $x ),*);
+        }
+    };
+}
+
+#[cfg(feature = "defmt")]
+macro_rules! unwrap {
+    ($($x:tt)*) => {
+        ::defmt::unwrap!($($x)*)
+    };
+}
+
+#[cfg(not(feature = "defmt"))]
+macro_rules! unwrap {
+    ($arg:expr) => {
+        match $crate::fmt::Try::into_result($arg) {
+            ::core::result::Result::Ok(t) => t,
+            ::core::result::Result::Err(e) => {
+                ::core::panic!("unwrap of `{}` failed: {:?}", ::core::stringify!($arg), e);
+            }
+        }
+    };
+    ($arg:expr, $($msg:expr),+ $(,)? ) => {
+        match $crate::fmt::Try::into_result($arg) {
+            ::core::result::Result::Ok(t) => t,
+            ::core::result::Result::Err(e) => {
+                ::core::panic!("unwrap of `{}` failed: {}: {:?}", ::core::stringify!($arg), ::core::format_args!($($msg,)*), e);
+            }
+        }
+    }
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub struct NoneError;
+
+pub trait Try {
+    type Ok;
+    type Error;
+    fn into_result(self) -> Result<Self::Ok, Self::Error>;
+}
+
+impl<T> Try for Option<T> {
+    type Ok = T;
+    type Error = NoneError;
+
+    #[inline]
+    fn into_result(self) -> Result<T, NoneError> {
+        self.ok_or(NoneError)
+    }
+}
+
+impl<T, E> Try for Result<T, E> {
+    type Ok = T;
+    type Error = E;
+
+    #[inline]
+    fn into_result(self) -> Self {
+        self
+    }
+}
diff --git a/embassy-boot/stm32/src/lib.rs b/embassy-boot/stm32/src/lib.rs
new file mode 100644
index 000000000..d1754a310
--- /dev/null
+++ b/embassy-boot/stm32/src/lib.rs
@@ -0,0 +1,75 @@
+#![no_std]
+#![feature(generic_associated_types)]
+#![feature(type_alias_impl_trait)]
+
+mod fmt;
+
+pub use embassy_boot::{FirmwareUpdater, FlashProvider, Partition, SingleFlashProvider, State};
+
+pub struct BootLoader<const PAGE_SIZE: usize> {
+    boot: embassy_boot::BootLoader<PAGE_SIZE>,
+}
+
+impl<const PAGE_SIZE: usize> BootLoader<PAGE_SIZE> {
+    /// Create a new bootloader instance using parameters from linker script
+    pub fn default() -> Self {
+        extern "C" {
+            static __bootloader_state_start: u32;
+            static __bootloader_state_end: u32;
+            static __bootloader_active_start: u32;
+            static __bootloader_active_end: u32;
+            static __bootloader_dfu_start: u32;
+            static __bootloader_dfu_end: u32;
+        }
+
+        let active = unsafe {
+            Partition::new(
+                &__bootloader_active_start as *const u32 as usize,
+                &__bootloader_active_end as *const u32 as usize,
+            )
+        };
+        let dfu = unsafe {
+            Partition::new(
+                &__bootloader_dfu_start as *const u32 as usize,
+                &__bootloader_dfu_end as *const u32 as usize,
+            )
+        };
+        let state = unsafe {
+            Partition::new(
+                &__bootloader_state_start as *const u32 as usize,
+                &__bootloader_state_end as *const u32 as usize,
+            )
+        };
+
+        trace!("ACTIVE: 0x{:x} - 0x{:x}", active.from, active.to);
+        trace!("DFU: 0x{:x} - 0x{:x}", dfu.from, dfu.to);
+        trace!("STATE: 0x{:x} - 0x{:x}", state.from, state.to);
+
+        Self::new(active, dfu, state)
+    }
+
+    /// Create a new bootloader instance using the supplied partitions for active, dfu and state.
+    pub fn new(active: Partition, dfu: Partition, state: Partition) -> Self {
+        Self {
+            boot: embassy_boot::BootLoader::new(active, dfu, state),
+        }
+    }
+
+    /// Boots the application
+    pub fn prepare<F: FlashProvider>(&mut self, flash: &mut F) -> usize {
+        match self.boot.prepare_boot(flash) {
+            Ok(_) => self.boot.boot_address(),
+            Err(_) => panic!("boot prepare error!"),
+        }
+    }
+
+    pub unsafe fn load(&mut self, start: usize) -> ! {
+        trace!("Loading app at 0x{:x}", start);
+        let mut p = cortex_m::Peripherals::steal();
+        #[cfg(not(feature = "thumbv6"))]
+        p.SCB.invalidate_icache();
+        p.SCB.vtor.write(start as u32);
+
+        cortex_m::asm::bootload(start as *const u32)
+    }
+}
diff --git a/embassy-boot/stm32/src/main.rs b/embassy-boot/stm32/src/main.rs
new file mode 100644
index 000000000..6fe0fb66d
--- /dev/null
+++ b/embassy-boot/stm32/src/main.rs
@@ -0,0 +1,62 @@
+#![no_std]
+#![no_main]
+
+use cortex_m_rt::{entry, exception};
+
+#[cfg(feature = "defmt")]
+use defmt_rtt as _;
+
+use embassy_boot_stm32::*;
+use embassy_stm32::flash::Flash;
+
+#[cfg(not(any(feature = "flash-2k", feature = "flash-256", feature = "flash-128")))]
+compile_error!("No flash size specified. Must specify exactly one of the following features: flash-2k, flash-256, flash-128");
+
+#[entry]
+fn main() -> ! {
+    let p = embassy_stm32::init(Default::default());
+
+    // Uncomment this if you are debugging the bootloader with debugger/RTT attached,
+    // as it prevents a hard fault when accessing flash 'too early' after boot.
+    /*
+        for i in 0..10000000 {
+            cortex_m::asm::nop();
+        }
+    */
+
+    #[cfg(feature = "flash-2k")]
+    let mut bl: BootLoader<2048> = BootLoader::default();
+
+    #[cfg(feature = "flash-256")]
+    let mut bl: BootLoader<256> = BootLoader::default();
+
+    #[cfg(feature = "flash-128")]
+    let mut bl: BootLoader<128> = BootLoader::default();
+
+    let mut flash = Flash::unlock(p.FLASH);
+    let start = bl.prepare(&mut SingleFlashProvider::new(&mut flash));
+    core::mem::drop(flash);
+    unsafe { bl.load(start) }
+}
+
+#[no_mangle]
+#[cfg_attr(target_os = "none", link_section = ".HardFault.user")]
+unsafe extern "C" fn HardFault() {
+    cortex_m::peripheral::SCB::sys_reset();
+}
+
+#[exception]
+unsafe fn DefaultHandler(_: i16) -> ! {
+    const SCB_ICSR: *const u32 = 0xE000_ED04 as *const u32;
+    let irqn = core::ptr::read_volatile(SCB_ICSR) as u8 as i16 - 16;
+
+    panic!("DefaultHandler #{:?}", irqn);
+}
+
+#[panic_handler]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
+    unsafe {
+        cortex_m::asm::udf();
+        core::hint::unreachable_unchecked();
+    }
+}