Adds additional Armv8-R AArch64 example programs, along with a single-core critical section implementation. The examples expand upon the existing Hello, World example and demonstrate the use of the Arm Generic Interrupt Controller and logging using defmt via the PL011 UART.

Using https://review.trustedfirmware.org/c/arm-firmware-crates/arm-fvp-base-pac/+/49345/2 as a patch to arm-fvp-base-pac, temporarily.

Author: jonathanpallant

.github/workflows/build.yml

@@ -91,7 +91,6 @@ jobs:
     - run: cargo clippy --target=${{ matrix.target }}
 
   armv8r-examples:
-    runs-on: ubuntu-latest
     name: Build Armv8-R Examples
     steps:
     - uses: actions/checkout@v6

Cargo.toml

@@ -21,3 +21,7 @@ exclude = [
 
 [dependencies]
 tock-registers = { version = "0.10.0", default-features = false } # Use it as interface-only library.
+critical-section = { version = "1.2.0", features = ["restore-state-u8"], optional = true }
+
+[features]
+critical-section-single-core = ["critical-section"]

examples/armv8-r/.cargo/config.toml

@@ -6,3 +6,6 @@ runner = "FVP_BaseR_AEMv8R -f fvp_cfg.txt"
 
 [unstable]
 build-std = ["core", "compiler_builtins"]
+
+[env]
+DEFMT_LOG = "info"

examples/armv8-r/.gitignore

@@ -1 +1,2 @@
 !/Cargo.lock
+/uart0.out

examples/armv8-r/Cargo.lock

@@ -5,8 +5,17 @@ name = "armv8-r"
 publish = false
 
 [dependencies]
-aarch64-rt = { version = "=0.4.0", default-features = false }
-aarch64-cpu.path = "../.."
+aarch64-rt = { version = "=0.4.0", default-features = false, features = [
+    "exceptions",
+] }
+# NB: Point this at Github once https://review.trustedfirmware.org/c/arm-firmware-crates/arm-fvp-base-pac/+/49345 is accepted
+arm-fvp-base-pac = { git = "https://review.trustedfirmware.org/arm-firmware-crates/arm-fvp-base-pac", rev = "refs/changes/45/49345/2", default-features = false, features = [
+    "swapped-memory-layout",
+] }
+arm-gic = "0.7.2"
+aarch64-cpu = { path = "../..", features = ["critical-section-single-core"] }
+critical-section = "1.2.0"
+defmt = "1.0.1"
 semihosting = { version = "0.1.24", default-features = false, features = [
     "panic-handler",
     "stdio",

examples/armv8-r/Cargo.toml

@@ -18,6 +18,13 @@ This folder contains example programs for the Armv8-R AArch64 architecture.
 
 [1]: https://developer.arm.com/Tools%20and%20Software/Fixed%20Virtual%20Platforms/Arm%20Architecture%20FVPs
 
+* (Optional) `defmt-print` to decode the defmt logs produced by some examples.
+  The tool can be installed with the following command:
+
+``` console
+$ cargo install defmt-print --version 1.0.0 --locked
+```
+
 ## Running the examples
 
 All commands in this section are meant to be executed using this directory as the working directory.
@@ -33,6 +40,54 @@ Hello, world! running from EL2
 static variables: X=0, Y=1
 ```
 
+### `interrupts`
+
+This program showcases nested interrupt handling.
+
+``` console
+$ cargo run --bin interrupts
+start of main
+  > irq_current()
+  Handling SGI 1
+  SGI1 handler
+  before raising SGI0
+    > irq_current()
+    Handling SGI 0
+    SGI0 handler
+    Handled SGI 0
+    < irq_current()
+  after raising SGI0
+  Handled SGI 1
+  < irq_current()
+end of main
+```
+
+### `defmt`
+
+This program showcases defmt logging.
+The defmt logs are output via UART0 (serial port 0) and not printed to the console.
+
+``` console
+$ cargo run --bin defmt
+before defmt log
+before raise SGI0
+after raise SGI0
+  > irq_current()
+  Handling SGI 0
+  Handled SGI 0
+  < irq_current()
+after defmt log
+```
+
+The FVP will create a file named `uart0.out` in the current directory that contains the UART0 output of the program.
+This file is defmt-encoded and can be decoded with the following command:
+
+``` console
+$ cat uart0.out | defmt-print -e target/aarch64v8r-unknown-none/debug/defmt
+INFO  >>> 42 <<<
+INFO  SGI0 handler
+```
+
 ## License
 
 Licensed under either of