diff --git a/.cargo/config.toml b/.cargo/config.toml
index e06644f..7615d85 100644
--- a/.cargo/config.toml
+++ b/.cargo/config.toml
@@ -27,6 +27,3 @@ runner = "qemu-system-arm -machine versatileab -cpu arm926 -semihosting -nograph
 
 [target.thumbv4t-none-eabi]
 runner = "qemu-system-arm -machine versatileab -cpu pxa250 -semihosting -nographic -audio none -kernel"
-
-[unstable]
-build-std = ["core", "alloc"]
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index d7c152c..67e875f 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -16,15 +16,13 @@ jobs:
           echo 'rust_versions={"rust": ["stable", "1.83"]}' >> "$GITHUB_OUTPUT"
 
   # Build the workspace for a target architecture
-  build:
+  build-tier2:
     runs-on: ubuntu-24.04
     needs: setup
     strategy:
       matrix:
         rust: ${{ fromJSON(needs.setup.outputs.matrix).rust }}
         target:
-          - armebv7r-none-eabi
-          - armebv7r-none-eabihf
           - armv7r-none-eabi
           - armv7r-none-eabihf
           - armv7a-none-eabi
@@ -38,101 +36,112 @@ jobs:
           rustup target add ${{ matrix.target }}
       - name: Build
         run: |
-          cargo build --target ${{ matrix.target }} --features "serde, defmt, check-asm"
-          cargo build --target ${{ matrix.target }} --no-default-features
+          cargo build --target ${{ matrix.target }}
+          cargo build --target ${{ matrix.target }} --features "serde, defmt, critical-section-multi-core, check-asm"
+          cargo build --target ${{ matrix.target }} --features "serde, defmt, critical-section-single-core, check-asm"
 
-  build-versatileab:
+  # These targets are in nightly and coming to stable soon
+  build-tier2-nightly:
     runs-on: ubuntu-24.04
     needs: setup
     strategy:
       matrix:
-        rust: ${{ fromJSON(needs.setup.outputs.matrix).rust }}
+        target:
+          - armv7a-none-eabi
+          - armv7a-none-eabihf
+          - armv7r-none-eabi
+          - armv7r-none-eabihf
+          - armv8r-none-eabihf
     steps:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Install rust
         run: |
-          rustup install ${{ matrix.rust }}
-          rustup default ${{ matrix.rust }}
-          rustup target add armv7a-none-eabi
-          rustup target add armv7r-none-eabi
-          rustup target add armv7r-none-eabihf
+          rustup install nightly-2025-10-29
+          rustup target add ${{ matrix.target }} --toolchain nightly-2025-10-29
       - name: Build
         run: |
-          cargo build --manifest-path ./examples/versatileab/Cargo.toml --target armv7a-none-eabi
-          cargo build --manifest-path ./examples/versatileab/Cargo.toml --target armv7r-none-eabi
-          cargo build --manifest-path ./examples/versatileab/Cargo.toml --target armv7r-none-eabihf
+          cargo +nightly-2025-10-29 build --target ${{ matrix.target }}
+          cargo +nightly-2025-10-29 build --target ${{ matrix.target }} --features "serde, defmt, critical-section-multi-core, check-asm"
+          cargo +nightly-2025-10-29 build --target ${{ matrix.target }} --features "serde, defmt, critical-section-single-core, check-asm"
 
-  build-mps3-an536:
+  # These targets need build-std, and have no atomics so cannot build the critical-section module
+  build-tier3-no-atomics:
     runs-on: ubuntu-24.04
     needs: setup
     strategy:
       matrix:
-        rust: ${{ fromJSON(needs.setup.outputs.matrix).rust }}
+        target:
+          - armv4t-none-eabi
+          - thumbv4t-none-eabi
+          - armv5te-none-eabi
+          - thumbv5te-none-eabi
     steps:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Install rust
         run: |
-          rustup install nightly
-          rustup default nightly
-          rustup component add rust-src --toolchain nightly
+          rustup install nightly-2025-10-29
+          rustup component add rust-src --toolchain nightly-2025-10-29
       - name: Build
         run: |
-          cargo build --manifest-path ./examples/mps3-an536/Cargo.toml --target armv8r-none-eabihf -Zbuild-std=core
+          cargo +nightly-2025-10-29 build --target ${{ matrix.target }} -Zbuild-std=core
+          cargo +nightly-2025-10-29 build --target ${{ matrix.target }} -Zbuild-std=core --features "serde, defmt, check-asm"
 
-  # Build the host tools
-  build-host:
+  build-versatileab:
     runs-on: ubuntu-24.04
     needs: setup
     strategy:
       matrix:
-        rust: [stable, 1.59]
+        rust: ${{ fromJSON(needs.setup.outputs.matrix).rust }}
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-      - name: Install rust
+      - name: Build
         run: |
-          rustup install ${{ matrix.rust }}
-          rustup default ${{ matrix.rust }}
+          cd examples/versatileab
+          cargo build --target armv7a-none-eabi
+          cargo build --target armv7r-none-eabi
+          cargo build --target armv7r-none-eabihf
+
+  build-mps3-an536:
+    runs-on: ubuntu-24.04
+    needs: setup
+    strategy:
+      matrix:
+        rust: ${{ fromJSON(needs.setup.outputs.matrix).rust }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
       - name: Build
         run: |
-          cd arm-targets
-          cargo build
-          cargo test
+          cd examples/mps3-an536
+          cargo build --target armv8r-none-eabihf
 
-  # Build the workspace for the target architecture but using nightly to compile libcore
-  # Technically it doesn't need 'setup' but it makes the graph look nicer
-  build-tier3:
+  # Build the host tools
+  build-host:
     runs-on: ubuntu-24.04
     needs: setup
     strategy:
       matrix:
-        target:
-          - armv7a-none-eabi
-          - armv7a-none-eabihf
-          - armv7r-none-eabi
-          - armv7r-none-eabihf
-          - armv8r-none-eabihf
-          - armebv7r-none-eabi
-          - armebv7r-none-eabihf
+        rust: [stable, 1.59]
     steps:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Install rust
         run: |
-          rustup install nightly
-          rustup default nightly
-          rustup component add rust-src --toolchain nightly
+          rustup install ${{ matrix.rust }}
+          rustup default ${{ matrix.rust }}
       - name: Build
         run: |
-          cargo build --target ${{ matrix.target }} -Zbuild-std=core --features "serde, defmt, check-asm"
-          cargo build --target ${{ matrix.target }} -Zbuild-std=core --no-default-features
+          cd arm-targets
+          cargo build
+          cargo test
 
   # Gather all the above build jobs together for the purposes of getting an overall pass-fail
   build-all:
     runs-on: ubuntu-24.04
-    needs: [build, build-tier3, build-host, build-versatileab, build-mps3-an536]
+    needs: [build-tier2, build-tier2-nightly, build-tier3-no-atomics, build-host, build-versatileab, build-mps3-an536]
     steps:
       - run: /bin/true
 
@@ -145,8 +154,6 @@ jobs:
         rust: ${{ fromJSON(needs.setup.outputs.matrix).rust }}
         target:
           - armv7a-none-eabi
-          - armebv7r-none-eabi
-          - armebv7r-none-eabihf
           - armv7r-none-eabi
           - armv7r-none-eabihf
     steps:
@@ -160,7 +167,6 @@ jobs:
       - name: Build docs
         run: |
           cargo doc --target ${{ matrix.target }}
-          cargo doc --target ${{ matrix.target }} --no-default-features
           cargo doc --target ${{ matrix.target }} --all-features
 
   # Build the docs for the host tools
@@ -235,8 +241,6 @@ jobs:
       matrix:
         rust: ${{ fromJSON(needs.setup.outputs.matrix).rust }}
         target:
-          - armebv7r-none-eabi
-          - armebv7r-none-eabihf
           - armv7r-none-eabi
           - armv7r-none-eabihf
           - armv7a-none-eabi
@@ -303,10 +307,6 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-      - name: Install rust
-        run: |
-          rustup install 1.89
-          rustup default 1.89
       - name: Install Dependencies
         run: |
           sudo apt-get -y update
diff --git a/examples/mps3-an536/Cargo.toml b/examples/mps3-an536/Cargo.toml
index 537a96e..290c617 100644
--- a/examples/mps3-an536/Cargo.toml
+++ b/examples/mps3-an536/Cargo.toml
@@ -29,3 +29,4 @@ arm-targets = {version = "0.3.0", path = "../../arm-targets"}
 
 [features]
 eabi-fpu = ["aarch32-rt/eabi-fpu"]
+fpu-d32 = ["aarch32-rt/fpu-d32"]
diff --git a/examples/mps3-an536/rust-toolchain.toml b/examples/mps3-an536/rust-toolchain.toml
index 5d56faf..cc61252 100644
--- a/examples/mps3-an536/rust-toolchain.toml
+++ b/examples/mps3-an536/rust-toolchain.toml
@@ -1,2 +1,6 @@
 [toolchain]
-channel = "nightly"
+channel = "nightly-2025-10-29"
+targets = [
+	"armv8r-none-eabihf",
+]
+components = ["rust-src"]
diff --git a/examples/versatileab/rust-toolchain.toml b/examples/versatileab/rust-toolchain.toml
new file mode 100644
index 0000000..e016496
--- /dev/null
+++ b/examples/versatileab/rust-toolchain.toml
@@ -0,0 +1,9 @@
+[toolchain]
+channel = "nightly-2025-10-29"
+targets = [
+	"armv7r-none-eabi",
+	"armv7r-none-eabihf",
+	"armv7a-none-eabi",
+	"armv7a-none-eabihf",
+]
+components = ["rust-src"]
diff --git a/tests.sh b/tests.sh
index 97f2762..7e2f1a7 100755
--- a/tests.sh
+++ b/tests.sh
@@ -3,11 +3,6 @@
 # Runs a series of sample programs in QEMU and checks that the standard output
 # is as expected.
 
-rustup target add armv7r-none-eabi
-rustup target add armv7r-none-eabihf
-rustup target add armv7a-none-eabi
-rustup component add rust-src
-
 # Set this to 1 to exit on the first error
 EXIT_FAST=0
 
@@ -25,9 +20,6 @@ fail() {
 
 mkdir -p ./target
 
-versatile_ab_cargo="--manifest-path examples/versatileab/Cargo.toml"
-mps3_an536_cargo="--manifest-path examples/mps3-an536/Cargo.toml"
-
 my_diff() {
     file_a=$1
     file_b=$2
@@ -46,101 +38,39 @@ my_diff() {
     fi
 }
 
-# armv7r-none-eabi tests
-cargo build ${versatile_ab_cargo} --target=armv7r-none-eabi || exit 1
-for bin_path in $(ls examples/versatileab/src/bin/*.rs); do
-    filename=${bin_path##*/}
-    binary=${filename%.rs}
-    cargo run ${versatile_ab_cargo} --target=armv7r-none-eabi --bin $binary > ./target/$binary-armv7r-none-eabi.out
-    my_diff ./examples/versatileab/reference/$binary-armv7r-none-eabi.out ./target/$binary-armv7r-none-eabi.out || fail $binary "armv7r-none-eabi"
-done
-
-# armv7r-none-eabihf tests
-cargo build ${versatile_ab_cargo} --target=armv7r-none-eabihf || exit 1
-for bin_path in $(ls examples/versatileab/src/bin/*.rs); do
-    filename=${bin_path##*/}
-    binary=${filename%.rs}
-    cargo run ${versatile_ab_cargo} --target=armv7r-none-eabihf --bin $binary > ./target/$binary-armv7r-none-eabihf.out
-    my_diff ./examples/versatileab/reference/$binary-armv7r-none-eabihf.out ./target/$binary-armv7r-none-eabihf.out || fail $binary "armv7r-none-eabihf"
-done
-
-# armv7a-none-eabi tests
-cargo build ${versatile_ab_cargo} --target=armv7a-none-eabi || exit 1
-for bin_path in $(ls examples/versatileab/src/bin/*.rs); do
-    filename=${bin_path##*/}
-    binary=${filename%.rs}
-    cargo run ${versatile_ab_cargo} --target=armv7a-none-eabi --bin $binary > ./target/$binary-armv7a-none-eabi.out
-    my_diff ./examples/versatileab/reference/$binary-armv7a-none-eabi.out ./target/$binary-armv7a-none-eabi.out || fail $binary "armv7a-none-eabi"
-done
-
-# armv7a-none-eabihf tests
-RUSTC_BOOTSTRAP=1 cargo build ${versatile_ab_cargo} --target=armv7a-none-eabihf || exit 1
-for bin_path in $(ls examples/versatileab/src/bin/*.rs); do
-    filename=${bin_path##*/}
-    binary=${filename%.rs}
-    RUSTC_BOOTSTRAP=1 cargo run ${versatile_ab_cargo} --target=armv7a-none-eabihf --bin $binary > ./target/$binary-armv7a-none-eabihf.out
-    my_diff ./examples/versatileab/reference/$binary-armv7a-none-eabihf.out ./target/$binary-armv7a-none-eabihf.out || fail $binary "armv7a-none-eabihf"
-done
-
-# armv7a-none-eabihf double-precision tests
-RUSTC_BOOTSTRAP=1 RUSTFLAGS="-Ctarget-feature=+d32" cargo build ${versatile_ab_cargo} --target=armv7a-none-eabihf  --features=fpu-d32 || exit 1
-for bin_path in $(ls examples/versatileab/src/bin/*.rs); do
-    filename=${bin_path##*/}
-    binary=${filename%.rs}
-    RUSTC_BOOTSTRAP=1 RUSTFLAGS="-Ctarget-feature=+d32" cargo run ${versatile_ab_cargo} --target=armv7a-none-eabihf --bin $binary --features=fpu-d32 > ./target/$binary-armv7a-none-eabihf-dp.out
-    my_diff ./examples/versatileab/reference/$binary-armv7a-none-eabihf.out ./target/$binary-armv7a-none-eabihf-dp.out || fail $binary "armv7a-none-eabihf"
-done
-
-# armv5te-none-eabi tests
-RUSTC_BOOTSTRAP=1 cargo build ${versatile_ab_cargo} --target=armv5te-none-eabi
-for bin_path in $(ls examples/versatileab/src/bin/*.rs); do
-    filename=${bin_path##*/}
-    binary=${filename%.rs}
-    RUSTC_BOOTSTRAP=1 cargo run ${versatile_ab_cargo} --target=armv5te-none-eabi --bin $binary > ./target/$binary-armv5te-none-eabi.out
-    my_diff ./examples/versatileab/reference/$binary-armv5te-none-eabi.out ./target/$binary-armv5te-none-eabi.out || fail $binary "armv5te-none-eabi"
-done
-
-# thumbv5te-none-eabi tests
-RUSTC_BOOTSTRAP=1 cargo build ${versatile_ab_cargo} --target=thumbv5te-none-eabi
-for bin_path in $(ls examples/versatileab/src/bin/*.rs); do
-    filename=${bin_path##*/}
-    binary=${filename%.rs}
-    RUSTC_BOOTSTRAP=1 cargo run ${versatile_ab_cargo} --target=thumbv5te-none-eabi --bin $binary > ./target/$binary-thumbv5te-none-eabi.out
-    my_diff ./examples/versatileab/reference/$binary-thumbv5te-none-eabi.out ./target/$binary-thumbv5te-none-eabi.out || fail $binary "thumbv5te-none-eabi"
-done
-
-# armv4t-none-eabi tests
-RUSTC_BOOTSTRAP=1 cargo build ${versatile_ab_cargo} --target=armv4t-none-eabi
-for bin_path in $(ls examples/versatileab/src/bin/*.rs); do
-    filename=${bin_path##*/}
-    binary=${filename%.rs}
-    RUSTC_BOOTSTRAP=1 cargo run ${versatile_ab_cargo} --target=armv4t-none-eabi --bin $binary > ./target/$binary-armv4t-none-eabi.out
-    my_diff ./examples/versatileab/reference/$binary-armv4t-none-eabi.out ./target/$binary-armv4t-none-eabi.out || fail $binary "armv4t-none-eabi"
-done
-
-# thumbv4t-none-eabi tests
-RUSTC_BOOTSTRAP=1 cargo build ${versatile_ab_cargo} --target=thumbv4t-none-eabi
-for bin_path in $(ls examples/versatileab/src/bin/*.rs); do
-    filename=${bin_path##*/}
-    binary=${filename%.rs}
-    RUSTC_BOOTSTRAP=1 cargo run ${versatile_ab_cargo} --target=thumbv4t-none-eabi --bin $binary > ./target/$binary-thumbv4t-none-eabi.out
-    my_diff ./examples/versatileab/reference/$binary-thumbv4t-none-eabi.out ./target/$binary-thumbv4t-none-eabi.out || fail $binary "thumbv4t-none-eabi"
-done
-
-# These tests only run on QEMU 9 or higher.
-# Ubuntu 24.04 supplies QEMU 8, which doesn't support the machine we have configured for this target
-RUSTC_BOOTSTRAP=1 cargo build ${mps3_an536_cargo} --target=armv8r-none-eabihf || exit 1
-if qemu-system-arm --version | grep "version \(9\|10\)"; then
-    # armv8r-none-eabihf tests
-    for bin_path in $(ls examples/mps3-an536/src/bin/*.rs); do
-        filename=${bin_path##*/}
+run_tests() {
+    directory=$1
+    target="$2"
+    flags=$3
+    echo "Running directory=$directory target=$target flags=$flags"
+    pushd $directory
+    cargo build --target=$target $flags || exit 1
+    for bin_path in src/bin/*.rs; do
+        filename=$(basename $bin_path)
         binary=${filename%.rs}
-        RUSTC_BOOTSTRAP=1 cargo run ${mps3_an536_cargo} --target=armv8r-none-eabihf --bin $binary > ./target/$binary-armv8r-none-eabihf.out
-        my_diff ./examples/mps3-an536/reference/$binary-armv8r-none-eabihf.out ./target/$binary-armv8r-none-eabihf.out || fail $binary "armv8r-none-eabihf"
+        cargo run --target=$target --bin $binary $flags > ./target/$binary-$target.out
+        my_diff ./reference/$binary-$target.out ./target/$binary-$target.out || fail $binary $target
     done
-    RUSTC_BOOTSTRAP=1 cargo run ${mps3_an536_cargo} --target=armv8r-none-eabihf --bin smp_test -- -smp 2 > ./target/smp_test-armv8r-none-eabihf_smp2.out
-    my_diff ./examples/mps3-an536/reference/smp_test-armv8r-none-eabihf_smp2.out ./target/smp_test-armv8r-none-eabihf_smp2.out || fail smp_test "armv8r-none-eabihf"
-fi
+    popd
+}
+
+run_tests examples/versatileab armv7r-none-eabi ""
+run_tests examples/versatileab armv7r-none-eabihf ""
+run_tests examples/versatileab armv7a-none-eabi ""
+run_tests examples/versatileab armv7a-none-eabihf ""
+RUSTFLAGS="-Ctarget-feature=+d32" run_tests examples/versatileab armv7a-none-eabihf "--features=fpu-d32"
+run_tests examples/versatileab armv5te-none-eabi "-Zbuild-std=core"
+run_tests examples/versatileab armv4t-none-eabi "-Zbuild-std=core"
+run_tests examples/versatileab thumbv5te-none-eabi "-Zbuild-std=core"
+run_tests examples/versatileab thumbv4t-none-eabi "-Zbuild-std=core"
+run_tests examples/mps3-an536 armv8r-none-eabihf ""
+RUSTFLAGS="-Ctarget-cpu=cortex-r52" run_tests examples/mps3-an536 armv8r-none-eabihf "--features=fpu-d32"
+
+# Special case the SMP test. You can't run the normal examples with two CPUs because nothing stops the second CPU from running :/
+pushd examples/mps3-an536
+cargo run --target=armv8r-none-eabihf --bin smp_test -- --smp 2 > ./target/smp_test-armv8r-none-eabihf_smp2.out
+my_diff ./reference/smp_test-armv8r-none-eabihf_smp2.out ./target/smp_test-armv8r-none-eabihf_smp2.out || fail smp_test armv8r-none-eabihf
+popd
 
 if [ "$FAILURE" == "1" ]; then
     echo "***************************************************"