ESP32-C3: Add support for booting from MCUboot bootloader

esp-hal-common/src/lib.rs

@@ -157,11 +157,8 @@ mod critical_section_impl {
         unsafe impl critical_section::Impl for super::CriticalSection {
             unsafe fn acquire() -> critical_section::RawRestoreState {
                 let mut mstatus = 0u32;
-                unsafe {
-                    core::arch::asm!("csrrci {0}, mstatus, 8", inout(reg) mstatus);
-                }
+                core::arch::asm!("csrrci {0}, mstatus, 8", inout(reg) mstatus);
                 let interrupts_active = (mstatus & 0b1000) != 0;
-
                 #[cfg(multi_core)]
                 {
                     let guard = multicore::MULTICORE_LOCK.lock();

esp32c3-hal/Cargo.toml

@@ -25,6 +25,7 @@ categories = [
 ]
 
 [dependencies]
+cfg-if           = "1.0"
 embedded-hal     = { version = "0.2.7", features = ["unproven"] }
 embedded-hal-1   = { version = "=1.0.0-alpha.9", optional = true, package = "embedded-hal" }
 embedded-hal-nb  = { version = "=1.0.0-alpha.1", optional = true }
@@ -43,6 +44,7 @@ ssd1306           = "0.7.1"
 
 [features]
 default           = ["rt", "vectored"]
+mcu-boot          = []
 direct-boot       = []
 eh1               = ["esp-hal-common/eh1", "dep:embedded-hal-1", "dep:embedded-hal-nb"]
 rt                = ["riscv-rt"]
@@ -62,3 +64,6 @@ required-features = ["eh1"]
 [[example]]
 name              = "spi_eh1_device_loopback"
 required-features = ["eh1"]
+
+[profile.dev]
+opt-level = 1

esp32c3-hal/README.md

@@ -23,6 +23,130 @@ The compilation target for this device is officially supported via the `stable`
 $ rustup target add riscv32imc-unknown-none-elf
 ```
 
+### Supported boot methods
+
+#### IDF Bootloader
+
+The [IDF second stage bootloader](https://docs.espressif.com/projects/esp-idf/en/latest/esp32c3/api-guides/startup.html#second-stage-bootloader) is the default bootloader solution.
+
+By default, [espflash](https://github.com/esp-rs/espflash) fetches the required binaries (Bootloader and Partition Table) and flashes them onto the target device together with the Rust-based application firmware image.
+
+#### MCUboot Secure Bootloader
+
+[MCUboot](https://github.com/mcu-tools/mcuboot) is a secure bootloader solution feature-wise equivalent to the [IDF Bootloader](#idf-bootloader).
+You may find more information on the documentation pages for MCUboot and the Espressif port:
+- https://docs.mcuboot.com/
+- https://docs.mcuboot.com/readme-espressif.html
+
+##### Requirements
+
+Booting from MCUboot secure bootloader requires the Rust application image to be built in a [MCUboot-specific image format](https://docs.mcuboot.com/design.html#image-format). You need to install the following dependencies:
+
+```shell
+# Required for generating the object file in Intel HEX format
+cargo install cargo-binutils
+rustup component add llvm-tools-preview
+
+# MCUboot's tool for image signing and key management
+pip install imgtool
+```
+
+Currently, MCUboot is still not supported as a booting option in [espflash](https://github.com/esp-rs/espflash/issues/267), so you'll need to use the [esptool](https://github.com/espressif/esptool) utility for flashing both the MCUboot bootloader and the Rust application binaries:
+
+```shell
+# Serial flasher utility for Espressif chips
+pip install esptool
+```
+
+Download a prebuilt MCUboot bootloader image for the target device:
+
+```shell
+# Prebuilt MCUboot bootloader binary
+curl -LO https://github.com/espressif/esp-nuttx-bootloader/releases/download/latest/mcuboot-esp32c3.bin
+```
+
+##### Booting the Hello World example from MCUboot
+
+Build the Hello World example with MCUboot support:
+
+```shell
+cargo build --release --example hello_world --features mcu-boot
+```
+Then proceed to generating the application binary and flashing it onto the target device:
+
+```shell
+# Generate the object file in Intel HEX format
+rust-objcopy -O ihex target/riscv32imc-unknown-none-elf/release/examples/hello_world app.hex
+
+# Generate the application firmware image binary file in MCUboot-format
+imgtool sign --pad --align 4 -v 0 -s auto -H 32 --pad-header -S 0x100000 app.hex app.bin
+
+# Flash the application firmware image binary onto the target device
+esptool.py -c esp32c3 -p /dev/ttyUSB0 -b 921600 --after no_reset write_flash -fs 4MB -fm dio -ff 40m 0x0 ./mcuboot-esp32c3.bin 0x110000 ./app.bin
+```
+Once the device is flashed, you may monitor the serial interface (e.g. with `picocom`):
+
+```shell
+picocom -b 115200 /dev/ttyUSB0 --imap lfcrlf
+```
+
+Reset the board and MCUboot should load the Hello World example:
+```shell
+ESP-ROM:esp32c3-api1-20210207
+Build:Feb  7 2021
+rst:0x1 (POWERON),boot:0xc (SPI_FAST_FLASH_BOOT)
+SPIWP:0xee
+mode:DIO, clock div:2
+load:0x3fcd8598,len:0x10cc
+load:0x403c8000,len:0x2b90
+load:0x403d0000,len:0x1364
+entry 0x403c804a
+[esp32c3] [INF] Enabling RNG early entropy source...
+[esp32c3] [INF] *** Booting MCUboot build v1.8.0-86-g14763b1 ***
+[esp32c3] [INF] Primary image: magic=good, swap_type=0x2, copy_done=0x1, image_ok=0x3
+[esp32c3] [INF] Scratch: magic=unset, swap_type=0x1, copy_done=0x3, image_ok=0x3
+[esp32c3] [INF] Boot source: none
+[esp32c3] [INF] Swap type: test
+[esp32c3] [INF] Disabling RNG early entropy source...
+[esp32c3] [INF] br_image_off = 0x10000
+[esp32c3] [INF] ih_hdr_size = 0x20
+[esp32c3] [INF] DRAM segment: start=0x3fcd0000, size=0x0, vaddr=0x3fcd0000
+[esp32c3] [INF] IRAM segment: start=0x1d00, size=0x170c, vaddr=0x40380000
+[esp32c3] [INF] start=0x40380004
+Hello world!
+Hello world!
+Hello world!
+```
+
+#### Direct Boot
+
+[Direct Boot](https://github.com/espressif/esp32c3-direct-boot-example#direct-boot-in-esp32-c3) allows an application stored in the External Flash to be executed directly, without being copied into Internal RAM.
+
+##### Booting the Hello World example using Direct Boot
+
+Build the Hello World example with support for Direct Boot:
+
+```shell
+cargo build --release --example hello_world --features direct-boot
+```
+
+Then proceed to generating the application binary and flashing it onto the target device:
+
+```shell
+cargo espflash --release --format direct-boot --features direct-boot --example hello_world --monitor
+```
+
+The ROM Bootloader will identify the firmware image built with Direct Boot support and load it appropriately from the External Flash:
+
+```shell
+ESP-ROM:esp32c3-api1-20210207
+Build:Feb  7 2021
+rst:0x1 (POWERON),boot:0xc (SPI_FAST_FLASH_BOOT)
+Hello world!
+Hello world!
+Hello world!
+```
+
 ## License
 
 Licensed under either of:

esp32c3-hal/build.rs

@@ -1,5 +1,21 @@
 use std::{env, fs::File, io::Write, path::PathBuf, process::exit};
 
+// Thanks to kennytm and TheDan64 for the assert_used_features macro.
+// Source:
+// https://github.com/TheDan64/inkwell/blob/36c3b106e61b1b45295a35f94023d93d9328c76f/src/lib.rs#L81-L110
+macro_rules! assert_unique_features {
+    () => {};
+    ($first:tt $(,$rest:tt)*) => {
+        $(
+            #[cfg(all(feature = $first, feature = $rest))]
+            compile_error!(concat!("Features \"", $first, "\" and \"", $rest, "\" cannot be used together"));
+        )*
+        assert_unique_features!($($rest),*);
+    }
+}
+
+assert_unique_features! {"mcu-boot", "direct-boot"}
+
 #[cfg(feature = "direct-boot")]
 fn main() {
     check_opt_level();
@@ -36,7 +52,7 @@ fn main() {
     add_defaults();
 }
 
-#[cfg(not(feature = "direct-boot"))]
+#[cfg(not(any(feature = "mcu-boot",feature = "direct-boot")))]
 fn main() {
     check_opt_level();
 
@@ -66,13 +82,55 @@ fn main() {
     add_defaults();
 }
 
+#[cfg(feature = "mcu-boot")]
+fn main() {
+    check_opt_level();
+
+    // Put the linker script somewhere the linker can find it
+    let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
+
+    File::create(out.join("memory.x"))
+        .unwrap()
+        .write_all(include_bytes!("ld/mb-esp32c3-memory.x"))
+        .unwrap();
+
+    File::create(out.join("esp32c3-link.x"))
+        .unwrap()
+        .write_all(include_bytes!("ld/mb-esp32c3-link.x"))
+        .unwrap();
+
+    File::create(out.join("riscv-link.x"))
+        .unwrap()
+        .write_all(include_bytes!("ld/mb-riscv-link.x"))
+        .unwrap();
+
+    File::create(out.join("linkall.x"))
+        .unwrap()
+        .write_all(include_bytes!("ld/mb-linkall.x"))
+        .unwrap();
+
+    println!("cargo:rustc-link-search={}", out.display());
+
+    // Only re-run the build script when memory.x is changed,
+    // instead of when any part of the source code changes.
+    println!("cargo:rerun-if-changed=ld/memory.x");
+
+    add_defaults();
+}
+
 fn add_defaults() {
     let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
+
     File::create(out.join("hal-defaults.x"))
         .unwrap()
         .write_all(include_bytes!("ld/hal-defaults.x"))
         .unwrap();
 
+    File::create(out.join("rom-functions.x"))
+        .unwrap()
+        .write_all(include_bytes!("ld/rom-functions.x"))
+        .unwrap();
+
     println!("cargo:rustc-link-search={}", out.display());
 }
 

esp32c3-hal/ld/db-esp32c3-memory.x

@@ -32,7 +32,6 @@ MEMORY
     RTC_FAST : ORIGIN = 0x50000000, LENGTH = 0x2000 /*- ESP_BOOTLOADER_RESERVE_RTC*/
 }
 
-
 REGION_ALIAS("REGION_TEXT", IROM);
 REGION_ALIAS("REGION_RODATA", DROM);
 

esp32c3-hal/ld/mb-esp32c3-link.x

@@ -0,0 +1,45 @@
+INCLUDE memory.x
+
+SECTIONS
+{
+  .metadata :
+  {
+    /* Magic for load header */
+
+    LONG(0xace637d3)
+
+    /* Application entry point address */
+
+    KEEP(*(.entry_addr))
+
+    /* IRAM metadata:
+     * - Destination address (VMA) for IRAM region
+     * - Flash offset (LMA) for start of IRAM region
+     * - Size of IRAM region
+     */
+
+    LONG(ADDR(.rwtext))
+    LONG(LOADADDR(.rwtext))
+    LONG(SIZEOF(.rwtext))
+
+    /* DRAM metadata:
+     * - Destination address (VMA) for DRAM region
+     * - Flash offset (LMA) for start of DRAM region
+     * - Size of DRAM region
+     */
+
+    LONG(ADDR(.data))
+    LONG(LOADADDR(.data))
+    LONG(SIZEOF(.data))
+  } > metadata
+}
+
+INCLUDE riscv-link.x
+
+_image_drom_vma = ADDR(.rodata);
+_image_drom_lma = LOADADDR(.rodata);
+_image_drom_size = LOADADDR(.rodata) + SIZEOF(.rodata) - _image_drom_lma;
+
+_image_irom_vma = ADDR(.text);
+_image_irom_lma = LOADADDR(.text);
+_image_irom_size = LOADADDR(.text) + SIZEOF(.text) - _image_irom_lma;

esp32c3-hal/ld/mb-esp32c3-memory.x

@@ -0,0 +1,66 @@
+MEMORY
+{
+    /*
+        https://github.com/espressif/esptool/blob/ed64d20b051d05f3f522bacc6a786098b562d4b8/esptool/targets/esp32c3.py#L78-L90
+        MEMORY_MAP = [[0x00000000, 0x00010000, "PADDING"],
+                  [0x3C000000, 0x3C800000, "DROM"],
+                  [0x3FC80000, 0x3FCE0000, "DRAM"],
+                  [0x3FC88000, 0x3FD00000, "BYTE_ACCESSIBLE"],
+                  [0x3FF00000, 0x3FF20000, "DROM_MASK"],
+                  [0x40000000, 0x40060000, "IROM_MASK"],
+                  [0x42000000, 0x42800000, "IROM"],
+                  [0x4037C000, 0x403E0000, "IRAM"],
+                  [0x50000000, 0x50002000, "RTC_IRAM"],
+                  [0x50000000, 0x50002000, "RTC_DRAM"],
+                  [0x600FE000, 0x60100000, "MEM_INTERNAL2"]]
+    */
+
+    /* The origin values for "metadata" and "ROM" memory regions are the actual
+     * load addresses.
+     *
+     * NOTE: The memory region starting from 0x0 with 0x20 length is reserved
+     * for the MCUboot header, which will be prepended to the binary file by
+     * the "imgtool" during the signing of firmware image.
+     */
+    metadata : ORIGIN = 0x20, LENGTH = 0x20
+    ROM : ORIGIN = 0x40, LENGTH = 0x400000 - 0x40
+
+    /* 400K of on soc RAM, 16K reserved for cache */
+    ICACHE : ORIGIN = 0x4037C000,  LENGTH = 0x4000
+    /* Instruction RAM */
+    IRAM : ORIGIN = 0x4037C000 + 0x4000, LENGTH = 400K - 0x4000
+    /* Data RAM */
+    DRAM : ORIGIN = 0x3FC80000, LENGTH = 0x50000
+
+    /* External flash */
+    /* Instruction ROM */
+    IROM : ORIGIN =   0x42000000, LENGTH = 0x400000
+    /* Data ROM */
+    /* The DROM segment origin is offset by 0x40 for mirroring the actual ROM
+     * image layout:
+     *    0x0  - 0x1F : MCUboot header
+     *    0x20 - 0x3F : Application image metadata section
+     *    0x40 onwards: ROM code and data
+     * This is required to meet the following constraint from the external
+     * flash MMU:
+     *    VMA % 64KB == LMA % 64KB
+     * i.e. the lower 16 bits of both the virtual address (address seen by the
+     * CPU) and the load address (physical address of the external flash) must
+     * be equal.
+     */
+    DROM : ORIGIN = 0x3C000000 + 0x40, LENGTH = 0x400000 - 0x40
+
+    /* RTC fast memory (executable). Persists over deep sleep. */
+    RTC_FAST : ORIGIN = 0x50000000, LENGTH = 0x2000 /*- ESP_BOOTLOADER_RESERVE_RTC*/
+}
+
+REGION_ALIAS("REGION_TEXT", IROM);
+REGION_ALIAS("REGION_RODATA", DROM);
+
+REGION_ALIAS("REGION_DATA", DRAM);
+REGION_ALIAS("REGION_BSS", DRAM);
+REGION_ALIAS("REGION_HEAP", DRAM);
+REGION_ALIAS("REGION_STACK", DRAM);
+
+REGION_ALIAS("REGION_RWTEXT", IRAM);
+REGION_ALIAS("REGION_RTC_FAST", RTC_FAST);

esp32c3-hal/ld/mb-linkall.x

@@ -0,0 +1,3 @@
+INCLUDE "esp32c3-link.x"
+INCLUDE "hal-defaults.x"
+INCLUDE "rom-functions.x"