os-boot: Add Makefile and CI.

Author: Arielfoever

.github/workflows/os-boot.yml

@@ -0,0 +1,75 @@
+name: Build os-boot
+permissions:
+  id-token: write
+  attestations: write
+  contents: read
+
+on: 
+  push:
+    paths:
+      - '.github/workflows/ob-boot.yml'
+  pull_request:
+    paths:
+      - '.github/workflows/ob-boot.yml'
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Install packages
+        run: sudo apt install -y build-essential curl
+
+      - name: Check out repository code
+        uses: actions/checkout@v4
+
+      - name: Make ELF
+        working-directory: os-boot
+        run: make
+      
+      - name: Generate SBOM
+        working-directory: os-boot
+        run: shasum -a 256 build/*.tar.xz > SBOM.sha256
+      
+      - name: Generate SBOM attestation
+        uses: actions/attest-sbom@v1
+        with:
+          subject-path: 'build/fw_payload.elf'
+          sbom-path: 'SBOM.sha256'
+      
+      - name: Upload ELF
+        uses: actions/upload-artifact@v4
+        id: upload
+        with:
+          name: os-boot-${{ github.run_id }}
+          path: build/fw_payload.elf
+      
+      - name: Generate artifact attestation
+        uses: actions/attest-build-provenance@v2
+        id: attest
+        with:
+          subject-path: build/fw_payload.elf
+          subject-digest: sha256:${{ steps.upload.outputs.artifact-digest }}
+      
+      - name: Upload Paper Work
+        working-directory: os-boot
+        env:
+          ELFURL: ${{ steps.upload.outputs.artifact-url }}
+          ATTESTURL: ${{ steps.attest.outputs.attestation-url }}
+        run: |
+          echo "# os-boot ELF" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "The generated [ELF file]("$ELFURL") can be verified from [here]("$ATTESTURL")." >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "## Header" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "\`\`\`" >> $GITHUB_STEP_SUMMARY
+          readelf -h build/fw_payload.elf >> $GITHUB_STEP_SUMMARY
+          echo "\`\`\`" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "## SBOM" >> $GITHUB_STEP_SUMMARY
+          echo "\`\`\`" >> $GITHUB_STEP_SUMMARY
+          cat SBOM.sha256 >> $GITHUB_STEP_SUMMARY
+          echo "\`\`\`" >> $GITHUB_STEP_SUMMARY
+
+      

os-boot/Makefile

@@ -0,0 +1,60 @@
+.PHONY: download_gcc download_linux download_opensbi linux opensbi clean all
+
+all: clean download_gcc download_linux download_opensbi linux opensbi
+
+RISCV_COMPILER_URL ?= https://github.com/riscv-collab/riscv-gnu-toolchain/releases/download/2025.01.20/riscv64-glibc-ubuntu-24.04-gcc-nightly-2025.01.20-nightly.tar.xz
+LINUX_VERSION ?= 6.14.4
+OPENSBI_VERSION ?= 1.6
+
+download_gcc:
+	mkdir -p build
+	curl -L $(RISCV_COMPILER_URL) -o build/gcc.tar.xz
+	tar -C build -xf build/gcc.tar.xz
+
+download_linux:
+	mkdir -p build
+	curl -L https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-$(LINUX_VERSION).tar.xz -o build/linux.tar.xz
+	tar -C build -xf build/linux.tar.xz
+
+download_opensbi:
+	mkdir -p build
+	curl -L https://github.com/riscv-software-src/opensbi/archive/refs/tags/v$(OPENSBI_VERSION).tar.gz -o build/opensbi.tar.xz
+	tar -C build -xf build/opensbi.tar.xz
+
+CROSS_COMPILE := $(shell pwd)/build/riscv/bin/riscv64-unknown-linux-gnu-
+
+elf := build/opensbi-$(OPENSBI_VERSION)/build/platform/generic/firmware/fw_payload.elf
+
+# Number of instructions to run.
+LIMIT_INSTRUCTIONS ?= 250000
+
+linux:
+	$(MAKE) -C build/linux-$(LINUX_VERSION) CROSS_COMPILE=$(CROSS_COMPILE) ARCH=riscv -j$(shell nproc) defconfig
+	$(MAKE) -C build/linux-$(LINUX_VERSION) CROSS_COMPILE=$(CROSS_COMPILE) CONFIG_HVC_RISCV_SBI=y ARCH=riscv -j$(shell nproc) Image vmlinux
+
+# FW_TEXT_START is 0 by default which doesn't leave space for the emulator bootloader.
+# 0x80000000 is the default start of Spike's memory.
+opensbi: 
+	$(MAKE) -C build/opensbi-$(OPENSBI_VERSION) FW_TEXT_START=0x80000000 FW_PAYLOAD=y FW_PAYLOAD_PATH=../linux-$(LINUX_VERSION)/arch/riscv/boot/Image PLATFORM=generic CROSS_COMPILE=$(CROSS_COMPILE) -j$(shell nproc) 
+	cp build/opensbi-$(OPENSBI_VERSION)/build/platform/generic/firmware/fw_payload.elf build/fw_payload.elf
+
+sail.dtb: sail.dts
+	dtc < sail.dts -o sail.dtb
+
+# Run on Spike.
+spike: 
+	spike --instructions=$(LIMIT_INSTRUCTIONS) $(elf)
+
+# Path to Sail emulator.
+SAIL := riscv_sim_rv64d
+
+# Run on Sail.
+sail: sail.dtb
+	../build/c_emulator/riscv_sim_rv64d --no-trace -p -l $(LIMIT_INSTRUCTIONS) --device-tree-blob sail.dtb -t /tmp/console.log build/opensbi-$(OPENSBI_VERSION)/build/platform/generic/firmware/fw_payload.elf 
+
+# QEMU attempt. Not sure I ever got this working.
+qemu:
+	qemu-system-riscv64 -M virt -m 256M -nographic -bios $(elf)
+
+clean:
+	rm -rf build