Add scripts to generate fresh vmlinux.h

Add script/gen-vmlinux-headers.sh (adapted from retsnoop [1]), that
can build a Linux Kernel for various architectures and generate
corresponding vmlinux.h header.

Add kconfigs directory with common and per-arch configurations that
can be used to produce vmlinux.h

In gen-vmlinux-header.sh if an explicit config is not specified,
append kconfigs/config.common and kconfigs/config.${ARCH} to build the
Linux Kernel.

[1] https://github.com/anakryiko/retsnoop/blob/master/scripts/gen-vmlinux-headers.sh

Signed-off-by: Ihor Solodrai <[email protected]>

Author: theihor

kconfigs/config.aarch64

@@ -0,0 +1 @@
+CONFIG_64BIT=y

kconfigs/config.common

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+CONFIG_BPF=y
+CONFIG_BPF_EVENTS=y
+CONFIG_BPF_JIT=y
+CONFIG_BPF_SYSCALL=y
+CONFIG_DEBUG_INFO=y
+CONFIG_DEBUG_INFO_BTF=y
+CONFIG_DEBUG_INFO_DWARF4=y
+CONFIG_FPROBE=y
+CONFIG_FTRACE=y
+CONFIG_FUNCTION_TRACER=y
+CONFIG_KPROBES=y
+CONFIG_KPROBE_EVENTS=y
+CONFIG_MMU=y
+CONFIG_MODULES=y
+CONFIG_PERF_EVENTS=y
+CONFIG_TRACEPOINTS=y
+CONFIG_TRACING=y
+CONFIG_UPROBE_EVENTS=y

kconfigs/config.loongarch64

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+CONFIG_64BIT=y

kconfigs/config.ppc64le

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+CONFIG_64BIT=y

kconfigs/config.riscv64

@@ -0,0 +1 @@
+CONFIG_64BIT=y

kconfigs/config.s390x

@@ -0,0 +1 @@
+CONFIG_64BIT=y

kconfigs/config.x86_64

@@ -0,0 +1 @@
+CONFIG_64BIT=y

scripts/gen-vmlinux-header.sh

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+#!/bin/bash
+
+usage () {
+        echo "USAGE: ./gen-vmlinux-headers.sh <arch> [<linux-repo-path> <kconfig-path>]"
+        exit 1
+}
+
+set -eu
+
+source $(dirname "$0")/helpers.sh
+
+WORKSPACE=$(pwd)
+BUILD_DIR="${BUILD_DIR:-$WORKSPACE/build}"
+GCC_VERSION=${GCC_VERSION:-"13"}
+OUTPUT_DIR="${OUTPUT_DIR:-$WORKSPACE/vmlinux.h}"
+
+TARGET_ARCH=$1
+LINUX_REPO=${2:-$WORKSPACE/linux}
+KCONFIG=${3:-}
+
+if [ -z "${TARGET_ARCH}" ]; then
+        echo "Error: Target architecture is not set"
+        usage
+fi
+
+if [ ! -d "${LINUX_REPO}" ]; then
+        echo "Error: Linux repo path is not found, LINUX_REPO=$LINUX_REPO"
+        usage
+fi
+
+if [ ! -f "${KCONFIG}" ]; then
+        KCONFIG=$(mktemp /tmp/kconfig.XXXX)
+        cp $WORKSPACE/kconfigs/config.common $KCONFIG
+        arch_conf="$WORKSPACE/kconfigs/config.${TARGET_ARCH}"
+        if [ -f "$arch_conf" ]; then
+                cat "$arch_conf" >> $KCONFIG
+        fi
+        echo "==== Using KCONFIG=$KCONFIG for kernel build"
+        cat $KCONFIG
+        echo "==== end of KCONFIG=$KCONFIG"
+fi
+
+mkdir -p "$BUILD_DIR"
+LINUX_REPO=$(realpath "$LINUX_REPO")
+KCONFIG=$(realpath "$KCONFIG")
+
+# Install the cross-compiler
+if [ "${TARGET_ARCH}" != "x86_64" ]; then
+        compiler_id=$(arch_compiler_id "$TARGET_ARCH")
+        sudo apt install -y                                    \
+                "gcc-${GCC_VERSION}-${compiler_id}"            \
+                "binutils-${compiler_id}"
+        sudo update-alternatives --install                     \
+                /usr/bin/${compiler_id}-gcc                    \
+                ${compiler_id}-gcc                             \
+                /usr/bin/${compiler_id}-gcc-${GCC_VERSION} 100
+        sudo update-alternatives --set                         \
+                ${compiler_id}-gcc                             \
+                /usr/bin/${compiler_id}-gcc-${GCC_VERSION}
+fi
+
+build_arch(){
+        local arch="$1"
+        local kbuild_output="$(realpath $BUILD_DIR/$arch)"
+        mkdir -p "$kbuild_output"
+        local arch_slug=$(arch_slug "$arch")
+        local compiler_id=$(arch_compiler_id "$arch")
+
+        echo "Building $arch ($arch_slug) into $kbuild_output..."
+        (
+                cd "$LINUX_REPO"
+                make O="$kbuild_output"                                 \
+                        ARCH=$arch_slug CROSS_COMPILE="${compiler_id}-" \
+                        tinyconfig
+                "$LINUX_REPO/scripts/kconfig/merge_config.sh" -m        \
+                        -O "$kbuild_output"                             \
+                        "$kbuild_output/.config" "${KCONFIG}"
+                make O="$kbuild_output"                                 \
+                        ARCH=$arch_slug CROSS_COMPILE="${compiler_id}-" \
+                        olddefconfig
+
+                make O="$kbuild_output"                                 \
+                        ARCH=$arch_slug CROSS_COMPILE="${compiler_id}-" \
+                        -j$(nproc) all
+
+                mkdir -p "$OUTPUT_DIR/$arch"
+                bpftool btf dump file "$kbuild_output/vmlinux" format c \
+                        > "$OUTPUT_DIR/$arch/vmlinux.h"
+        )
+}
+
+build_arch $TARGET_ARCH

scripts/helpers.sh

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+#!/bin/bash
+
+arch_slug() {
+        printf "$arch"                                  \
+        | sed 's/x86_64/x86/'                           \
+        | sed 's/i686/x86/'                             \
+        | sed 's/aarch64/arm64/'                        \
+        | sed 's/ppc64le/powerpc/'                      \
+        | sed 's/riscv64/riscv/'                        \
+        | sed 's/s390x/s390/'                           \
+        | sed 's/loongarch64/loongarch/'
+}
+
+arch_compiler_id() {
+        local arch="$1"
+        case "$arch" in
+                arm)
+                        echo "arm-linux-gnueabi"
+                        ;;
+                ppc64le)
+                        echo "powerpc64le-linux-gnu"
+                        ;;
+                *)
+                        echo "${arch}-linux-gnu"
+                        ;;
+        esac
+}
+