kernel: Factor our perf build from main kernel build

The build of the perf utility has been quite bothersome,
with different arches and kernel versions failing.

Since we now have the ful kernel source in the package,
factor out the actual build into Dockerfile.perf

Signed-off-by: Rolf Neugebauer <rn@rneugeba.io>

kernel/Dockerfile

@@ -172,16 +172,6 @@ RUN DVER=$(basename $(find /tmp/kernel-modules/lib/modules/ -mindepth 1 -maxdept
 
 RUN printf "KERNEL_SOURCE=${KERNEL_SOURCE}\n" > /out/kernel-source-info
 
-# perf
-# Only build perf for the latest LTS and the latest stable kernel.
-# Skip arm64 for now as perf for 4.19.x fails to build.
-RUN if [ "${KERNEL_SERIES}" != 4.9.x ] && [ $(uname -m) != aarch64 ]; then \
-       mkdir -p /build/perf && \
-       make -C tools/perf LDFLAGS=-static O=/build/perf && \
-       strip /build/perf/perf && \
-       cp /build/perf/perf /out; \
-     fi
-
 # Download Intel ucode and create a CPIO archive for it
 ENV UCODE_URL=https://downloadmirror.intel.com/28039/eng/microcode-20180807.tgz
 RUN set -e && \

kernel/Dockerfile.perf

@@ -1,10 +1,43 @@
-# This Dockerfile extracts the perf utility from a kernel package and
-# places it into a scratch image
+# This Dockerfile extracts the source code and headers from a kernel package,
+# builds the perf utility, and places it into a scratch image
 ARG IMAGE
-FROM ${IMAGE} AS kernel
+FROM ${IMAGE} AS ksrc
+
+FROM linuxkit/alpine:518c2ed0f398c5508969ac5e033607201fb419ed AS build
+RUN apk add \
+    argp-standalone \
+    bash \
+    bc \
+    binutils-dev \
+    bison \
+    build-base \
+    diffutils \
+    flex \
+    gmp-dev \
+    installkernel \
+    kmod \
+    libelf-dev \
+    mpc1-dev \
+    mpfr-dev \
+    sed \
+    tar \
+    xz \
+    xz-dev \
+    zlib-dev
+
+COPY --from=ksrc /linux.tar.xz /kernel-headers.tar /
+RUN tar xf linux.tar.xz && \
+    tar xf kernel-headers.tar
+
+WORKDIR /linux
+
+RUN mkdir -p /out && \
+    make -C tools/perf LDFLAGS=-static && \
+    strip tools/perf/perf && \
+    cp tools/perf/perf /out
 
 FROM scratch
 ENTRYPOINT []
 CMD []
 WORKDIR /
-COPY --from=kernel /perf /usr/bin/perf
+COPY --from=build /out/perf /usr/bin/perf