Add CI workflow to build and test with QEMU

Introduce GitHub Actions-based CI that builds the kernel using the
GNU RISC-V toolchain and runs selected apps (e.g., cpubench) in QEMU.

Results are extracted and posted to PRs. Toolchain setup, build,
and QEMU test logic are modularized into scripts in .ci/.

Features:
- Support multiple apps per run
- CI comments results on PR automatically
- Timeout prevents hangs

Limitations:
- Currently GNU-only (LLVM WIP)
- cpubench doesn't exit cleanly due to preemptive mode

Fixes: #2
Supersedes: #11

Author: G36maid

.ci/run-qemu-tests.sh

@@ -0,0 +1,49 @@
+#!/bin/bash
+set -e
+export CROSS_COMPILE=${CROSS_COMPILE:-riscv32-unknown-elf-}
+
+# Check if at least one app is provided
+if [ $# -eq 0 ]; then
+    echo "Usage: $0 <app1> [app2] [app3] ..."
+    echo "Example: $0 hello echo cpubench"
+    exit 1
+fi
+
+APPS="$@"
+TIMEOUT=10
+
+echo "[+] Will run apps: $APPS"
+echo ""
+
+# Loop through each app
+for app in $APPS; do
+    echo "=== Running $app ==="
+
+    # Build the app
+    echo "[+] Building $app..."
+    make clean >/dev/null 2>&1
+    if ! make "$app" >/dev/null 2>&1; then
+        echo "[!] Failed to build $app"
+        echo ""
+        continue
+    fi
+
+    # Run in QEMU with timeout
+    echo "[+] Running $app in QEMU (timeout: ${TIMEOUT}s)..."
+    set +e
+    timeout ${TIMEOUT}s qemu-system-riscv32 -nographic -machine virt -bios none -kernel build/image.elf
+    exit_code=$?
+    set -e
+
+    # Print result
+    if [ $exit_code -eq 124 ]; then
+        echo "[!] $app timed out"
+    elif [ $exit_code -eq 0 ]; then
+        echo "[✓] $app completed successfully"
+    else
+        echo "[!] $app failed with exit code $exit_code"
+    fi
+    echo ""
+done
+
+echo "[+] All apps tested"

.ci/setup-toolchain.sh

@@ -0,0 +1,61 @@
+#!/bin/bash
+set -e
+
+# Default to GNU if no toolchain specified
+TOOLCHAIN_TYPE=${1:-gnu}
+
+TOOLCHAIN_REPO=https://github.com/riscv-collab/riscv-gnu-toolchain
+TOOLCHAIN_VERSION=2025.07.03
+TOOLCHAIN_OS=ubuntu-24.04
+
+setup_gnu_toolchain() {
+    echo "[+] Setting up GNU RISC-V toolchain..."
+
+    local URL="${TOOLCHAIN_REPO}/releases/download/${TOOLCHAIN_VERSION}/riscv32-elf-${TOOLCHAIN_OS}-gcc-nightly-${TOOLCHAIN_VERSION}-nightly.tar.xz"
+
+    echo "[+] Downloading RISC-V GNU toolchain..."
+    wget -q "$URL"
+    tar -xf "$(basename "$URL")"
+
+    echo "[+] Exporting GNU toolchain path..."
+    echo "$PWD/riscv/bin" >> "$GITHUB_PATH"
+
+    # Set cross-compile prefix for GNU
+    echo "CROSS_COMPILE=riscv32-unknown-elf-" >> "$GITHUB_ENV"
+    echo "TOOLCHAIN_TYPE=gnu" >> "$GITHUB_ENV"
+}
+
+setup_llvm_toolchain() {
+    echo "[+] Setting up LLVM RISC-V toolchain..."
+
+    # upstream URL for LLVM toolchain
+    local URL="${TOOLCHAIN_REPO}/releases/download/${TOOLCHAIN_VERSION}/riscv32-elf-${TOOLCHAIN_OS}-llvm-nightly-${TOOLCHAIN_VERSION}-nightly.tar.xz"
+
+    echo "[+] Downloading RISC-V LLVM toolchain..."
+    wget -q "$URL"
+    tar -xf "$(basename "$URL")"
+
+    echo "[+] Exporting LLVM toolchain path..."
+    echo "$PWD/riscv/bin" >> "$GITHUB_PATH"
+
+    # Set cross-compile prefix for LLVM
+    echo "CROSS_COMPILE=riscv32-unknown-elf-" >> "$GITHUB_ENV"
+    echo "TOOLCHAIN_TYPE=llvm" >> "$GITHUB_ENV"
+    echo "AR=llvm-ar" >> "$GITHUB_ENV"
+}
+
+case "$TOOLCHAIN_TYPE" in
+    "gnu")
+        setup_gnu_toolchain
+        ;;
+    "llvm")
+        setup_llvm_toolchain
+        ;;
+    *)
+        echo "Error: Unknown toolchain type '$TOOLCHAIN_TYPE'"
+        echo "Usage: $0 [gnu|llvm]"
+        exit 1
+        ;;
+esac
+
+echo "[+] Toolchain setup complete: $TOOLCHAIN_TYPE"

.github/workflows/ci.yml

@@ -0,0 +1,57 @@
+name: Linmo CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  basic-tests:
+    runs-on: ubuntu-24.04
+    name: Basic Tests
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential qemu-system-riscv32 wget
+
+      - name: Setup GNU RISC-V Toolchain
+        run: .ci/setup-toolchain.sh gnu
+
+      - name: Verify toolchain installation
+        run: |
+          riscv32-unknown-elf-gcc --version
+          qemu-system-riscv32 --version
+        env:
+          CROSS_COMPILE: riscv32-unknown-elf-
+
+      - name: Build Kernel
+        run: |
+          make clean
+          make
+        env:
+          CROSS_COMPILE: riscv32-unknown-elf-
+
+      - name: Run Basic Apps
+        id: test
+        run: |
+          output=$(.ci/run-qemu-tests.sh cpubench test64)
+          echo "TEST_OUTPUT<<EOF" >> $GITHUB_OUTPUT
+          echo "$output" >> $GITHUB_OUTPUT
+          echo "EOF" >> $GITHUB_OUTPUT
+
+      - name: Comment PR with results
+        if: github.event_name == 'pull_request'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const output = `${{ steps.test.outputs.TEST_OUTPUT }}`;
+            github.rest.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: `## Linmo QEMU App Test Result\n\n\`\`\`\n${output}\n\`\`\`\n\n_This is an automated report from CI._`
+            });