Updates to bare metal day after teaching it again (#2775)

This fixes some issues running some of the examples, and various other
minor issues I found along the way.

src/bare-metal/aps/aarch64-rt.md

@@ -13,3 +13,10 @@ writing our own.
 ```rust,editable,compile_fail
 {{#include examples/src/main_rt.rs:main}}
 ```
+
+<details>
+
+- Run the example in QEMU with `make qemu_rt` under
+  `src/bare-metal/aps/examples`.
+
+</details>

src/bare-metal/aps/examples/Cargo.lock

@@ -14,9 +14,9 @@ dependencies = [
 
 [[package]]
 name = "aarch64-rt"
-version = "0.1.3"
+version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3be4edaff3b5ead5fb7e9ef0d72fa1e93b4052ec2410e0ebc93f6f360c9599ea"
+checksum = "3ba0820a68948e3655dbde1071b421d9ae8c08afb58e274b72c22e8a981c548c"
 dependencies = [
  "cfg-if",
  "smccc",

src/bare-metal/aps/examples/Cargo.toml

@@ -8,7 +8,7 @@ publish = false
 
 [dependencies]
 aarch64-paging = { version = "0.9.1", default-features = false }
-aarch64-rt = "0.1.3"
+aarch64-rt = "0.2.0"
 arm-pl011-uart = "0.3.1"
 bitflags = "2.9.1"
 log = "0.4.27"

src/bare-metal/aps/examples/Makefile

@@ -27,6 +27,8 @@ minimal.bin: build
 	cargo objcopy --bin minimal -- -O binary $@
 psci.bin: build
 	cargo objcopy --bin psci -- -O binary $@
+rt.bin: build
+	cargo objcopy --bin rt -- -O binary $@
 
 qemu: improved.bin
 	qemu-system-aarch64 -machine virt -cpu max -serial mon:stdio -display none -kernel $< -s
@@ -36,6 +38,8 @@ qemu_minimal: minimal.bin
 	qemu-system-aarch64 -machine virt -cpu max -serial mon:stdio -display none -kernel $< -s
 qemu_psci: psci.bin
 	qemu-system-aarch64 -machine virt -cpu max -serial mon:stdio -display none -kernel $< -s
+qemu_rt: rt.bin
+	qemu-system-aarch64 -machine virt -cpu max -serial mon:stdio -display none -kernel $< -s
 
 clean:
 	cargo clean

src/bare-metal/aps/examples/src/main_improved.rs

@@ -16,6 +16,7 @@
 #![no_main]
 #![no_std]
 
+mod asm;
 mod exceptions;
 mod pl011;
 

src/bare-metal/aps/examples/src/main_logger.rs

@@ -16,6 +16,7 @@
 #![no_main]
 #![no_std]
 
+mod asm;
 mod exceptions;
 mod logger;
 mod pl011;

src/bare-metal/aps/examples/src/main_psci.rs

@@ -19,6 +19,7 @@
 use core::arch::asm;
 use core::panic::PanicInfo;
 
+mod asm;
 mod exceptions;
 
 const PSCI_SYSTEM_OFF: u32 = 0x84000008;

src/bare-metal/aps/examples/src/main_rt.rs

@@ -24,7 +24,6 @@ use arm_pl011_uart::{PL011Registers, Uart, UniqueMmioPointer};
 use core::fmt::Write;
 use core::panic::PanicInfo;
 use core::ptr::NonNull;
-use log::error;
 use smccc::Hvc;
 use smccc::psci::system_off;
 
@@ -67,11 +66,9 @@ fn main(x0: u64, x1: u64, x2: u64, x3: u64) -> ! {
     system_off::<Hvc>().unwrap();
     panic!("system_off returned");
 }
-// ANCHOR_END: main
 
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
-    error!("{info}");
     system_off::<Hvc>().unwrap();
     loop {}
 }

src/bare-metal/microcontrollers/debugging.md

@@ -27,7 +27,7 @@ On gLinux or Debian:
 <!-- mdbook-xgettext: skip -->
 
 ```sh
-gdb-multiarch target/thumbv7em-none-eabihf/debug/board_support --eval-command="target remote :1337"
+gdb-multiarch target/thumbv7em-none-eabihf/debug/board_support --eval-command="target remote :1338"
 ```
 
 On MacOS:
@@ -35,7 +35,7 @@ On MacOS:
 <!-- mdbook-xgettext: skip -->
 
 ```sh
-arm-none-eabi-gdb target/thumbv7em-none-eabihf/debug/board_support --eval-command="target remote :1337"
+arm-none-eabi-gdb target/thumbv7em-none-eabihf/debug/board_support --eval-command="target remote :1338"
 ```
 
 <details>

src/bare-metal/microcontrollers/examples/Embed.toml

@@ -3,6 +3,7 @@ chip = "nrf52833_xxAA"
 
 [debug.gdb]
 enabled = true
+gdb_connection_string = "127.0.0.1:1338"
 
 [debug.reset]
 halt_afterwards = true

src/exercises/bare-metal/rtc.md

@@ -66,13 +66,22 @@ _Cargo.toml_ (you shouldn't need to change this):
 {{#include rtc/Cargo.toml}}
 ```
 
-_image.ld_ (you shouldn't need to change this):
+_build.rs_ (you shouldn't need to change this):
 
-<!-- File image.ld -->
+<!-- File build.rs -->
 <!-- mdbook-xgettext: skip -->
 
 ```ld
-{{#include rtc/image.ld}}
+{{#include rtc/build.rs}}
+```
+
+_memory.ld_ (you shouldn't need to change this):
+
+<!-- File memory.ld -->
+<!-- mdbook-xgettext: skip -->
+
+```ld
+{{#include rtc/memory.ld}}
 ```
 
 _Makefile_ (you shouldn't need to change this):

src/exercises/bare-metal/rtc/.cargo/config.toml

@@ -1,3 +1,2 @@
 [build]
 target = "aarch64-unknown-none"
-rustflags = ["-C", "link-arg=-Timage.ld"]

src/exercises/bare-metal/rtc/Cargo.lock

@@ -14,9 +14,9 @@ dependencies = [
 
 [[package]]
 name = "aarch64-rt"
-version = "0.1.3"
+version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3be4edaff3b5ead5fb7e9ef0d72fa1e93b4052ec2410e0ebc93f6f360c9599ea"
+checksum = "3ba0820a68948e3655dbde1071b421d9ae8c08afb58e274b72c22e8a981c548c"
 dependencies = [
  "cfg-if",
  "smccc",

src/exercises/bare-metal/rtc/Cargo.toml

@@ -8,7 +8,7 @@ publish = false
 
 [dependencies]
 aarch64-paging = { version = "0.9.1", default-features = false }
-aarch64-rt = "0.1.3"
+aarch64-rt = "0.2.0"
 arm-gic = "0.4.0"
 arm-pl011-uart = "0.3.1"
 bitflags = "2.9.1"

src/exercises/bare-metal/rtc/build.rs

@@ -0,0 +1,19 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+fn main() {
+    println!("cargo:rustc-link-arg=-Timage.ld");
+    println!("cargo:rustc-link-arg=-Tmemory.ld");
+    println!("cargo:rerun-if-changed=memory.ld");
+}

src/exercises/bare-metal/rtc/image.ld

@@ -1,104 +0,0 @@
-/*
- * Copyright 2023 Google LLC
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     https://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-/*
- * Code will start running at this symbol which is placed at the start of the
- * image.
- */
-ENTRY(entry)
-
-MEMORY
-{
-	image : ORIGIN = 0x40080000, LENGTH = 2M
-}
-
-SECTIONS
-{
-	/*
-	 * Collect together the code.
-	 */
-	.init : ALIGN(4096) {
-		text_begin = .;
-		*(.init.entry)
-		*(.init.*)
-	} >image
-	.text : {
-		*(.text.*)
-	} >image
-	text_end = .;
-
-	/*
-	 * Collect together read-only data.
-	 */
-	.rodata : ALIGN(4096) {
-		rodata_begin = .;
-		*(.rodata.*)
-	} >image
-	.got : {
-		*(.got)
-	} >image
-	rodata_end = .;
-
-	/*
-	 * Collect together the read-write data including .bss at the end which
-	 * will be zero'd by the entry code.
-	 */
-	.data : ALIGN(4096) {
-		data_begin = .;
-		*(.data.*)
-		/*
-		 * The entry point code assumes that .data is a multiple of 32
-		 * bytes long.
-		 */
-		. = ALIGN(32);
-		data_end = .;
-	} >image
-
-	/* Everything beyond this point will not be included in the binary. */
-	bin_end = .;
-
-	/* The entry point code assumes that .bss is 16-byte aligned. */
-	.bss : ALIGN(16)  {
-		bss_begin = .;
-		*(.bss.*)
-		*(COMMON)
-		. = ALIGN(16);
-		bss_end = .;
-	} >image
-
-	.stack (NOLOAD) : ALIGN(4096) {
-		boot_stack_begin = .;
-		. += 40 * 4096;
-		. = ALIGN(4096);
-		boot_stack_end = .;
-	} >image
-
-	. = ALIGN(4K);
-	PROVIDE(dma_region = .);
-
-	/*
-	 * Remove unused sections from the image.
-	 */
-	/DISCARD/ : {
-		/* The image loads itself so doesn't need these sections. */
-		*(.gnu.hash)
-		*(.hash)
-		*(.interp)
-		*(.eh_frame_hdr)
-		*(.eh_frame)
-		*(.note.gnu.build-id)
-	}
-}

src/exercises/bare-metal/rtc/memory.ld

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2023 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+MEMORY
+{
+	image : ORIGIN = 0x40080000, LENGTH = 2M
+}

src/exercises/bare-metal/rtc/src/logger.rs

@@ -12,7 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// ANCHOR: main
 use arm_pl011_uart::Uart;
 use core::fmt::Write;
 use log::{LevelFilter, Log, Metadata, Record, SetLoggerError};

tests/src/slides/slide-exemptions.list.ts

@@ -5,6 +5,7 @@ export const size_exemptions = [
   "android/interoperability/java.html",
   "android/testing.html",
   "bare-metal/aps/entry-point.html",
+  "bare-metal/aps/aarch64-rt.html",
   "exercises/bare-metal/compass.html",
   "exercises/bare-metal/solutions-afternoon.html",
   "exercises/bare-metal/rtc.html",