fix infra LLVM toolchain for RISC-V asm (#663)

* fix infra LLVM toolchain for RISC-V asm

* address provisioning review feedback

Author: MauroToscano

Makefile

@@ -56,6 +56,10 @@ SYSROOT_URL := https://lambda.alignedlayer.com/lambda-vm-sysroot-rv64im.tar.gz
 # $(abspath ...) because the build rule cd's into the program dir before invoking cargo.
 SYSROOT_CFLAGS := --target=riscv64 -march=rv64im -mabi=lp64 --sysroot=$(abspath $(SYSROOT_DIR))
 
+CLANG ?= clang
+ASM_CFLAGS ?= --target=riscv64 -march=rv64im -mabi=lp64
+ASM_LDFLAGS ?= -fuse-ld=lld -nostdlib -Wl,-e,main
+
 # Custom RV64IM target spec location
 RV64_TARGET_SPEC=$(CURDIR)/executor/programs/riscv64im-lambda-vm-elf.json
 
@@ -94,8 +98,8 @@ prepare-sysroot:
 compile-programs-asm:
 	@mkdir -p $(ASM_ARTIFACTS_DIR)
 	@set -e; for src in $(ASM_PROGRAMS); do \
-		echo "clang --target=riscv64 -fuse-ld=lld -nostdlib -Wl,-e,main $$src -o $(ASM_ARTIFACTS_DIR)/$$(basename $$src .s).elf"; \
-		clang --target=riscv64 -fuse-ld=lld -nostdlib -Wl,-e,main $$src -o $(ASM_ARTIFACTS_DIR)/$$(basename $$src .s).elf; \
+		echo "$(CLANG) $(ASM_CFLAGS) $(ASM_LDFLAGS) $$src -o $(ASM_ARTIFACTS_DIR)/$$(basename $$src .s).elf"; \
+		$(CLANG) $(ASM_CFLAGS) $(ASM_LDFLAGS) $$src -o $(ASM_ARTIFACTS_DIR)/$$(basename $$src .s).elf; \
 	done
 
 compile-programs-rust: prepare-sysroot $(RUST_ARTIFACTS)

README.md

@@ -19,7 +19,7 @@ The **[public roadmap](https://yetanotherco.github.io/lambda_vm_roadmap/)** lays
 - Rust nightly with `rust-src` component
 - Clang with RISC-V target support and LLD linker (used by `make compile-programs-asm`)
   - **macOS**: `brew install llvm` (the Homebrew LLVM includes `clang` and `lld` with RISC-V support)
-  - **Linux**: `apt install clang lld` (or equivalent for your distribution)
+  - **Linux**: use LLVM 21+ from apt.llvm.org or your distribution; older distro clang packages may reject the assembly fixtures' RISC-V ISA attributes
 
 ### Dev dependencies
 

infra/README.md

@@ -88,6 +88,7 @@ Everything has a working default; override via env var only when needed.
 | `READY_TIMEOUT` | `1800` (s) | `rent_baremetal.sh` | How long to wait for `status=ready && install.status=completed`. |
 | `PROVISION_FILE` | `<script_dir>/provision.sh` | both wrappers | Path to the remote provisioning script. |
 | `SSH_USER` | `root` | `provision_server.sh` | Switch to `admin` for re-runs after sshd hardening. |
+| `LLVM_VERSION` | `21` | provisioning scripts | LLVM major installed from apt.llvm.org for RISC-V assembly builds. |
 
 ### `SCW_TYPE` options
 

infra/provision.sh

@@ -13,6 +13,8 @@ log() { printf '\n=== %s ===\n' "$*"; }
 log "apt update + upgrade"
 export DEBIAN_FRONTEND=noninteractive
 APT_OPTS=(-y -o Dpkg::Options::=--force-confdef -o Dpkg::Options::=--force-confold)
+LLVM_VERSION="${LLVM_VERSION:-21}"
+LLVM_GPG_FINGERPRINT="6084F3CF814B57C1CF12EFD515CF4D18AF4F7421"
 
 # Scaleway baremetal Debian ships grub-cloud-amd64; its postinst (fired as a
 # trigger by initramfs-tools / shim-signed / kernel upgrades) runs grub-install
@@ -24,11 +26,46 @@ apt-get update -y
 apt-get upgrade "${APT_OPTS[@]}"
 
 # --- 2. apt packages ---------------------------------------------------------
-log "apt install base packages + clang/lld/llvm + xz-utils"
+log "apt install base packages + xz-utils"
 apt-get install "${APT_OPTS[@]}" \
     ca-certificates curl wget gnupg vim git zip unzip openssl libssl-dev jq \
-    build-essential rsyslog htop rsync pkg-config locales ufw \
-    clang lld llvm xz-utils
+    build-essential rsyslog htop rsync pkg-config locales ufw xz-utils
+
+# Debian's default clang can lag behind RISC-V ISA attribute syntax emitted by
+# the checked-in assembly fixtures. Use a pinned apt.llvm.org toolchain.
+log "LLVM $LLVM_VERSION toolchain from apt.llvm.org"
+. /etc/os-release
+LLVM_CODENAME="${VERSION_CODENAME:-}"
+if [ -z "$LLVM_CODENAME" ]; then
+    echo "ERROR: could not determine Debian/Ubuntu codename from /etc/os-release" >&2
+    exit 1
+fi
+install -d -m 0755 /etc/apt/keyrings
+wget -qO /etc/apt/keyrings/apt.llvm.org.asc https://apt.llvm.org/llvm-snapshot.gpg.key
+if ! LLVM_ACTUAL_FINGERPRINT="$(gpg --show-keys --with-colons /etc/apt/keyrings/apt.llvm.org.asc 2>/dev/null \
+    | awk -F: '/^fpr:/ { print $10; exit }')"; then
+    echo "ERROR: could not read apt.llvm.org GPG key fingerprint" >&2
+    exit 1
+fi
+if [ "$LLVM_ACTUAL_FINGERPRINT" != "$LLVM_GPG_FINGERPRINT" ]; then
+    echo "ERROR: apt.llvm.org GPG key fingerprint mismatch (got $LLVM_ACTUAL_FINGERPRINT, expected $LLVM_GPG_FINGERPRINT)" >&2
+    exit 1
+fi
+chmod 0644 /etc/apt/keyrings/apt.llvm.org.asc
+cat > /etc/apt/sources.list.d/apt.llvm.org.list <<EOF
+deb [signed-by=/etc/apt/keyrings/apt.llvm.org.asc] http://apt.llvm.org/$LLVM_CODENAME/ llvm-toolchain-$LLVM_CODENAME-$LLVM_VERSION main
+EOF
+apt-get update -y
+apt-get install "${APT_OPTS[@]}" "clang-$LLVM_VERSION" "lld-$LLVM_VERSION" "llvm-$LLVM_VERSION"
+for tool in clang clang++ lld ld.lld llvm-ar llvm-ranlib; do
+    versioned="/usr/bin/$tool-$LLVM_VERSION"
+    if [ ! -x "$versioned" ]; then
+        echo "ERROR: expected $versioned after installing LLVM $LLVM_VERSION" >&2
+        exit 1
+    fi
+    ln -sf "$versioned" "/usr/local/bin/$tool"
+done
+clang --version | head -n 1
 
 # --- 3. users: admin (sudo) + app (no sudo) ----------------------------------
 log "users: admin (sudo) + app (no sudo)"

infra/provision_server.sh

@@ -10,6 +10,7 @@
 #                        First-run servers accept root SSH; once provision.sh
 #                        has hardened sshd, re-run as: SSH_USER=admin ...
 #   PROVISION_FILE       default: <script-dir>/provision.sh
+#   LLVM_VERSION         default: 21
 #
 # SSH wait is indefinite — Ctrl+C to abort.
 
@@ -25,6 +26,7 @@ NC='\033[0m'
 
 SSH_USER="${SSH_USER:-root}"
 PROVISION_FILE="${PROVISION_FILE:-$SCRIPT_DIR/provision.sh}"
+LLVM_VERSION="${LLVM_VERSION:-21}"
 
 err() { echo -e "${RED}error:${NC} $*" >&2; }
 info() { echo -e "${BOLD}$*${NC}"; }
@@ -45,6 +47,12 @@ if ! command -v ssh >/dev/null 2>&1; then
     err "ssh not found on PATH."
     exit 1
 fi
+case "$LLVM_VERSION" in
+    ''|*[!0-9]*)
+        err "LLVM_VERSION must be a numeric LLVM major version, got '$LLVM_VERSION'"
+        exit 2
+        ;;
+esac
 
 SSH_OPTS=(-o StrictHostKeyChecking=accept-new -o ConnectTimeout=10 -o BatchMode=yes)
 
@@ -60,9 +68,9 @@ done
 ok "sshd reachable on $SSH_USER@$IP (attempt $attempt)"
 
 if [ "$SSH_USER" = "root" ]; then
-    REMOTE_CMD="bash -s"
+    REMOTE_CMD="env LLVM_VERSION=$LLVM_VERSION bash -s"
 else
-    REMOTE_CMD="sudo bash -s"
+    REMOTE_CMD="sudo env LLVM_VERSION=$LLVM_VERSION bash -s"
 fi
 
 info "Running $PROVISION_FILE on $SSH_USER@$IP..."

infra/rent_baremetal.sh

@@ -8,6 +8,7 @@
 #   SCW_TYPE              default: EM-I320E-NVME
 #   PROVISION_FILE        default: <repo>/infra/provision.sh
 #   READY_TIMEOUT         default: 1800 (seconds)
+#   LLVM_VERSION          default: 21
 #
 # Requires: scw, jq, ssh.
 # To delete the server when done: scw baremetal server delete <id> zone=<zone>
@@ -28,6 +29,7 @@ SCW_OS_ID="${SCW_OS_ID:-83640d93-a0b8-45ad-9c9f-30cae48380a4}"  # Debian
 SCW_PROJECT_ID="${SCW_PROJECT_ID:-946cfb34-d351-48c4-8566-127e7727e15f}"
 PROVISION_FILE="${PROVISION_FILE:-$SCRIPT_DIR/provision.sh}"
 READY_TIMEOUT="${READY_TIMEOUT:-1800}"
+LLVM_VERSION="${LLVM_VERSION:-21}"
 
 err() { echo -e "${RED}error:${NC} $*" >&2; }
 info() { echo -e "${BOLD}$*${NC}"; }
@@ -180,7 +182,7 @@ info "Wiping any stale known_hosts entry for $PUBLIC_IP (Scaleway recycles IPs).
 ssh-keygen -R "$PUBLIC_IP" >/dev/null 2>&1 || true
 
 info "Handing off to provision_server.sh (Ctrl+C to skip and provision later)..."
-PROVISION_FILE="$PROVISION_FILE" SSH_USER=root "$SCRIPT_DIR/provision_server.sh" "$PUBLIC_IP"
+PROVISION_FILE="$PROVISION_FILE" SSH_USER=root LLVM_VERSION="$LLVM_VERSION" "$SCRIPT_DIR/provision_server.sh" "$PUBLIC_IP"
 
 echo
 echo "To delete the server:"