build: use mold linker on arm64 Linux

.cargo/config.toml

@@ -37,6 +37,11 @@ rustflags = [
 #[target.x86_64-unknown-linux-gnu]
 #rustflags = ["-C", "linker=clang", "-C", "link-arg=-fuse-ld=lld"]
 
+# mold is significantly faster and more memory-efficient than ld on aarch64
+[target.aarch64-unknown-linux-gnu]
+linker = "clang"
+rustflags = ["-C", "link-arg=-fuse-ld=mold"]
+
 [env]
 RUST_TEST_THREADS = "40"
 

dev/docker/Dockerfile.build-artifacts-container-aarch64

@@ -16,6 +16,11 @@
 #
 FROM arm64v8/rust:1.97.1-slim-bullseye
 
+# Bullseye does not package mold. Keep this image on Bullseye for artifact
+# compatibility and install the pinned upstream ARM64 binary instead.
+ARG MOLD_VERSION=2.30.0
+ARG MOLD_SHA256=258aaf2b7808ea22fca625480efdf7a13830e9ee311716db0ba9c62af1770c07
+
 # Set in gitlab-templates/scripts/build-push-container-image.sh
 ARG CI_COMMIT_SHORT_SHA
 ENV CI_COMMIT_SHORT_SHA $CI_COMMIT_SHORT_SHA
@@ -60,6 +65,21 @@ RUN CACHEKEY=${CI_COMMIT_SHORT_SHA} apt update && \
 		git \
 	&& rm -rf /var/lib/apt/lists/*
 
+RUN curl -fsSL --retry 5 \
+		-o /tmp/mold.tar.gz \
+		"https://github.com/rui314/mold/releases/download/v${MOLD_VERSION}/mold-${MOLD_VERSION}-aarch64-linux.tar.gz" && \
+	echo "${MOLD_SHA256}  /tmp/mold.tar.gz" | sha256sum --check - && \
+	tar -C /usr/local --strip-components=1 -xzf /tmp/mold.tar.gz && \
+	rm /tmp/mold.tar.gz && \
+	mold --version
+
+# Keep the system linker for non-Rust builds such as iPXE, whose linker script
+# is not accepted by mold. Cargo uses this wrapper even outside the repository.
+RUN printf '#!/bin/sh\nexec clang -fuse-ld=mold "$@"\n' \
+		>/usr/local/bin/clang-mold && \
+	chmod 0755 /usr/local/bin/clang-mold
+ENV CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU_LINKER=/usr/local/bin/clang-mold
+
 RUN rustup component add rustfmt
 RUN cargo install cargo-cache cargo-make sccache && \
 	cargo install mdbook@0.4.52 mdbook-plantuml@0.8.0 mdbook-mermaid@0.16.2 && \

dev/docker/Dockerfile.build-artifacts-container-cross-aarch64

@@ -21,7 +21,7 @@ FROM rust:1.97.1-bookworm
 RUN dpkg --add-architecture arm64 && \
     apt-get update && \
     apt-get upgrade -y && \
-    apt-get -o Dpkg::Options::="--force-overwrite" install --assume-yes unzip libudev-dev:arm64 libssl-dev:arm64 libtss2-dev:arm64 g++-aarch64-linux-gnu libc6-dev-arm64-cross libclang-dev cmake
+    apt-get -o Dpkg::Options::="--force-overwrite" install --assume-yes unzip libudev-dev:arm64 libssl-dev:arm64 libtss2-dev:arm64 g++-aarch64-linux-gnu libc6-dev-arm64-cross libclang-dev cmake mold
 
 # protoc must match the image userspace (FROM rust:… resolves to host arch by default),
 # not the Rust target (aarch64); see prost-build protoc invocation.
@@ -40,5 +40,16 @@ ENV PATH="/protobuf/bin:${PATH}"
 
 RUN rustup target add aarch64-unknown-linux-gnu
 
-ENV CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU_LINKER=aarch64-linux-gnu-gcc CC_aarch64_unknown_linux_gnu=aarch64-linux-gnu-gcc CXX_aarch64_unknown_linux_gnu=aarch64-linux-gnu-g++ PKG_CONFIG_PATH=/lib/aarch64-linux-gnu/pkgconfig PKG_CONFIG_SYSROOT_DIR=/lib/aarch64-linux-gnu
+# Keep the cross-GCC driver so it supplies the ARM64 sysroot, but make mold an
+# invariant of that driver rather than relying on a mounted checkout's Cargo
+# configuration.
+RUN printf '#!/bin/sh\nexec aarch64-linux-gnu-gcc -fuse-ld=mold "$@"\n' \
+      >/usr/local/bin/aarch64-linux-gnu-gcc-mold && \
+    chmod 0755 /usr/local/bin/aarch64-linux-gnu-gcc-mold && \
+    printf 'int main(void) { return 0; }\n' | \
+      aarch64-linux-gnu-gcc-mold -x c - -o /tmp/mold-smoke && \
+    readelf -p .comment /tmp/mold-smoke | grep -q mold && \
+    rm /tmp/mold-smoke
+
+ENV CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU_LINKER=aarch64-linux-gnu-gcc-mold CC_aarch64_unknown_linux_gnu=aarch64-linux-gnu-gcc CXX_aarch64_unknown_linux_gnu=aarch64-linux-gnu-g++ PKG_CONFIG_PATH=/lib/aarch64-linux-gnu/pkgconfig PKG_CONFIG_SYSROOT_DIR=/lib/aarch64-linux-gnu
 WORKDIR ./carbide

dev/docker/Dockerfile.build-container-aarch64

@@ -54,6 +54,7 @@ RUN CACHEKEY=${CI_COMMIT_SHORT_SHA} apt update &&  \
 		libssl-dev \
 		libtss2-dev \
 		libudev-dev \
+		mold \
 		pandoc \
 		pkg-config \
 		tpm2-tools \
@@ -66,8 +67,12 @@ RUN CACHEKEY=${CI_COMMIT_SHORT_SHA} apt update &&  \
 		git \
 	&& rm -rf /var/lib/apt/lists/*
 
-# make LLVM's linker lld the default, because ld crashes using too much memory
-RUN update-alternatives --install /usr/bin/ld ld /usr/bin/lld 50
+# Keep the system linker for non-Rust builds such as iPXE, whose linker script
+# is not accepted by mold. Cargo uses this wrapper even outside the repository.
+RUN printf '#!/bin/sh\nexec clang -fuse-ld=mold "$@"\n' \
+		>/usr/local/bin/clang-mold && \
+	chmod 0755 /usr/local/bin/clang-mold
+ENV CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU_LINKER=/usr/local/bin/clang-mold
 
 RUN rustup component add rustfmt
 RUN cargo install cargo-cache cargo-make sccache --locked && \

dev/docker/Dockerfile.cargo-docker-minimal

@@ -17,14 +17,24 @@ RUN apt-get update && \
 	protobuf-compiler \
 	libpq-dev \
 	libssl-dev \
+	clang \
 	pkg-config \
 	lld \
+	mold \
 	&& rm -rf /var/lib/apt/lists/*
 
+RUN printf '#!/bin/sh\nexec clang -fuse-ld=lld "$@"\n' \
+		>/usr/local/bin/clang-lld && \
+	printf '#!/bin/sh\nexec clang -fuse-ld=mold "$@"\n' \
+		>/usr/local/bin/clang-mold && \
+	chmod 0755 /usr/local/bin/clang-lld /usr/local/bin/clang-mold
+
 # sccache: reuse compiled artifacts across runs (mount SCCACHE_DIR from host in run)
 RUN cargo install sccache --locked && rm -rf /usr/local/cargo/registry/src
 ENV RUSTC_WRAPPER=sccache
 ENV SCCACHE_DIR=/sccache
-# Use lld for linking (uses less RAM than default ld; avoids OOM when linking carbide-api tests).
+# Use lld on x86_64 and mold on aarch64 to avoid memory-heavy GNU ld links.
 # Enable tokio_unstable so tokio::task::Builder is available (used by api-db, api, etc.).
-ENV RUSTFLAGS="-C link-arg=-fuse-ld=lld --cfg tokio_unstable"
+ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=/usr/local/bin/clang-lld
+ENV CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU_LINKER=/usr/local/bin/clang-mold
+ENV RUSTFLAGS="--cfg tokio_unstable"