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build: compress linux binary with UPX in builder-linux stage #2934

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4 changes: 3 additions & 1 deletion Dockerfile
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Expand Up @@ -12,7 +12,7 @@ FROM crazymax/osxcross:15.5-debian AS osxcross

FROM --platform=$BUILDPLATFORM golang:${GO_VERSION}-alpine${ALPINE_VERSION} AS builder-base
COPY --from=xx / /
RUN apk add --no-cache clang zig
RUN apk add --no-cache clang zig upx
WORKDIR /src
RUN --mount=type=cache,target=/go/pkg/mod \
--mount=type=bind,source=go.mod,target=go.mod \
Expand All @@ -37,6 +37,8 @@ RUN --mount=type=cache,target=/root/.cache/go-build,id=go-build-$TARGETPLATFORM
xx-go build -trimpath -tags no_audio -ldflags "-s -w -linkmode=external -X 'github.com/docker/docker-agent/pkg/version.Version=$GIT_TAG' -X 'github.com/docker/docker-agent/pkg/version.Commit=$GIT_COMMIT'" -o /binaries/docker-agent-$TARGETOS-$TARGETARCH .
xx-verify --static /binaries/docker-agent-$TARGETOS-$TARGETARCH
EOT
RUN upx /binaries/docker-agent-$TARGETOS-$TARGETARCH && \
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@docker-agent docker-agent May 29, 2026

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[MEDIUM] UPX arm64 compatibility depends on version — build may fail for linux/arm64

UPX support for linux/arm64 ELF binaries was only added in UPX 4.0 (2023). Alpine's apk add upx installs whatever version the Alpine release ships:

  • Alpine 3.17 and earlier → UPX 3.x → no arm64 support → upx will fail at build time with CantPackException: bad ELF e_machine when TARGETARCH=arm64
  • Alpine 3.18+ → UPX 4.x → arm64 supported

The Dockerfile pins ALPINE_VERSION="3.22", so today this is fine. However:

  1. There is no floor on the UPX version, so a future Alpine base image re-tag that ships an older UPX could silently break linux/arm64 builds.
  2. The PR description notes the binary was tested at ~114 MB → ~30 MB but does not explicitly confirm arm64 (TARGETARCH=arm64) was part of the test run.

Suggested mitigation: Add an explicit upx --version check or pin the upx version (e.g., apk add upx~=4) to ensure arm64 support is guaranteed, and confirm the test plan covers both linux/amd64 and linux/arm64.

upx -t /binaries/docker-agent-$TARGETOS-$TARGETARCH

FROM builder-base AS builder-cross
ARG TARGETPLATFORM
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