crossbuild.go

// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
// or more contributor license agreements. Licensed under the Elastic License 2.0;
// you may not use this file except in compliance with the Elastic License 2.0.

package mage

import (
	"fmt"
	"go/build"
	"log"
	"os"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"time"

	"github.com/magefile/mage/mg"
	"github.com/magefile/mage/sh"

	"github.com/elastic/elastic-agent-libs/file"
	"github.com/elastic/elastic-agent/dev-tools/mage/gotool"
)

const defaultCrossBuildTarget = "golangCrossBuild"

// Platforms contains the set of target platforms for cross-builds. It can be
// modified at runtime by setting the PLATFORMS environment variable.
// See NewPlatformList for details about platform filtering expressions.
var Platforms = BuildPlatforms.Defaults()

// SelectedPackageTypes is the list of package types. If empty, all packages types
// are considered to be selected (see isPackageTypeSelected).
var SelectedPackageTypes []PackageType

// SelectedDockerVariants is the list of docker variants. If empty, all docker variants
// are considered to be selected (see isDockerVariantSelected).
var SelectedDockerVariants []DockerVariant

func init() {
	// Allow overriding via PLATFORMS.
	if expression := os.Getenv("PLATFORMS"); len(expression) > 0 {
		Platforms = NewPlatformList(expression)
	}

	// Allow overriding via PACKAGES.
	if packageTypes := os.Getenv("PACKAGES"); len(packageTypes) > 0 {
		for _, pkgtype := range strings.Split(packageTypes, ",") {
			var p PackageType
			err := p.UnmarshalText([]byte(pkgtype))
			if err != nil {
				continue
			}
			SelectedPackageTypes = append(SelectedPackageTypes, p)
		}
	}

	// Allow overriding via DOCKER_VARIANTS.
	if dockerVariants := os.Getenv("DOCKER_VARIANTS"); len(dockerVariants) > 0 {
		for _, docvariant := range strings.Split(dockerVariants, ",") {
			var v DockerVariant
			err := v.UnmarshalText([]byte(docvariant))
			if err != nil {
				continue
			}
			SelectedDockerVariants = append(SelectedDockerVariants, v)
		}
	}
}

// CrossBuildOption defines an option to the CrossBuild target.
type CrossBuildOption func(params *crossBuildParams)

// ImageSelectorFunc returns the name of the builder image.
type ImageSelectorFunc func(platform string) (string, error)

// ForPlatforms filters the platforms based on the given expression.
func ForPlatforms(expr string) func(params *crossBuildParams) {
	return func(params *crossBuildParams) {
		params.Platforms = params.Platforms.Filter(expr)
	}
}

// WithTarget specifies the mage target to execute inside the golang-crossbuild
// container.
func WithTarget(target string) func(params *crossBuildParams) {
	return func(params *crossBuildParams) {
		params.Target = target
	}
}

// InDir specifies the base directory to use when cross-building.
func InDir(path ...string) func(params *crossBuildParams) {
	return func(params *crossBuildParams) {
		params.InDir = filepath.Join(path...)
	}
}

// Serially causes each cross-build target to be executed serially instead of
// in parallel.
func Serially() func(params *crossBuildParams) {
	return func(params *crossBuildParams) {
		params.Serial = true
	}
}

// ImageSelector returns the name of the selected builder image.
func ImageSelector(f ImageSelectorFunc) func(params *crossBuildParams) {
	return func(params *crossBuildParams) {
		params.ImageSelector = f
	}
}

// AddPlatforms sets dependencies on others platforms.
func AddPlatforms(expressions ...string) func(params *crossBuildParams) {
	return func(params *crossBuildParams) {
		var list BuildPlatformList
		for _, expr := range expressions {
			list = NewPlatformList(expr)
			params.Platforms = params.Platforms.Merge(list)
		}
	}
}

type crossBuildParams struct {
	Platforms     BuildPlatformList
	Target        string
	Serial        bool
	InDir         string
	ImageSelector ImageSelectorFunc
}

// CrossBuild executes a given build target once for each target platform.
func CrossBuild(options ...CrossBuildOption) error {
	fmt.Println("--- CrossBuild Elastic-Agent")
	params := crossBuildParams{Platforms: Platforms, Target: defaultCrossBuildTarget, ImageSelector: CrossBuildImage}
	for _, opt := range options {
		opt(&params)
	}

	if len(params.Platforms) == 0 {
		log.Printf("Skipping cross-build of target=%v because platforms list is empty.", params.Target)
		return nil
	}

	// AIX can't really be crossbuilt, due to cgo and various compiler shortcomings.
	// If we have a singular AIX platform set, revert to a native build toolchain
	if runtime.GOOS == "aix" {
		for _, platform := range params.Platforms {
			if platform.GOOS() == "aix" {
				if len(params.Platforms) != 1 {
					return fmt.Errorf("platform AIX cannot be crossbuilt with other platforms. Set PLATFORMS='aix/ppc64'")
				}
				// This is basically a short-out so we can attempt to build on AIX in a relatively generic way
				log.Printf("Target is building for AIX, skipping normal crossbuild process")
				args := DefaultBuildArgs()
				args.OutputDir = filepath.Join("build", "golang-crossbuild")
				args.Name += "-" + Platform.GOOS + "-" + Platform.Arch
				return Build(args)

			}
		}
		// If we're here, something isn't set.
		return fmt.Errorf("cannot crossbuild on AIX. Either run `mage build` or set PLATFORMS='aix/ppc64'")
	}

	// Docker is required for this target.
	if err := HaveDocker(); err != nil {
		return err
	}

	if CrossBuildMountModcache {
		// Make sure the module dependencies are downloaded on the host,
		// as they will be mounted into the container read-only.
		mg.Deps(func() error { return gotool.Mod.Download() })
	}

	// Build the magefile for Linux, so we can run it inside the container.
	mg.Deps(buildMage)

	log.Println("crossBuild: Platform list =", params.Platforms)
	var deps []interface{}
	for _, buildPlatform := range params.Platforms {
		if !buildPlatform.Flags.CanCrossBuild() {
			return fmt.Errorf("unsupported cross build platform %v", buildPlatform.Name)
		}
		builder := GolangCrossBuilder{buildPlatform.Name, params.Target, params.InDir, params.ImageSelector}
		if params.Serial {
			if err := builder.Build(); err != nil {
				return fmt.Errorf("failed cross-building target=%s for platform=%s: %w",
					params.Target, buildPlatform.Name, err)
			}
		} else {
			deps = append(deps, builder.Build)
		}
	}

	// Each build runs in parallel.
	Parallel(deps...)

	return nil
}

// CrossBuildXPack executes the 'golangCrossBuild' target in the Beat's
// associated x-pack directory to produce a version of the Beat that contains
// Elastic licensed content.
func CrossBuildXPack(options ...CrossBuildOption) error {
	o := []CrossBuildOption{InDir("x-pack", BeatName)}
	o = append(o, options...)
	return CrossBuild(o...)
}

// buildMage pre-compiles the magefile to a binary using the GOARCH parameter.
// It has the benefit of speeding up the build because the
// mage -compile is done only once rather than in each Docker container.
func buildMage() error {
	arch := runtime.GOARCH
	return sh.RunWith(map[string]string{"CGO_ENABLED": "0"}, "mage", "-f", "-goos=linux", "-goarch="+arch,
		"-compile", CreateDir(filepath.Join("build", "mage-linux-"+arch)))
}

// CrossBuildImage build the docker image.
func CrossBuildImage(platform string) (string, error) {
	tagSuffix := "main"

	switch {
	case platform == "darwin/amd64":
		tagSuffix = "darwin-debian10"
	case platform == "darwin/arm64" || platform == "darwin/universal":
		tagSuffix = "darwin-arm64-debian10"
	case platform == "linux/arm64":
		tagSuffix = "arm"
	case platform == "linux/armv5" || platform == "linux/armv6":
		tagSuffix = "armel"
	case platform == "linux/armv7":
		tagSuffix = "armhf"
	case strings.HasPrefix(platform, "linux/mips"):
		tagSuffix = "mips-debian10"
	case strings.HasPrefix(platform, "linux/ppc"):
		tagSuffix = "ppc-debian10"
	case platform == "linux/s390x":
		tagSuffix = "s390x-debian10"
	case strings.HasPrefix(platform, "linux"):
		// Use an older version of libc to gain greater OS compatibility.
		// Debian 8 uses glibc 2.19.
		tagSuffix = "main-debian8"
	}

	goVersion, err := GoVersion()
	if err != nil {
		return "", err
	}

	return BeatsCrossBuildImage + ":" + goVersion + "-" + tagSuffix, nil
}

// GolangCrossBuilder executes the specified mage target inside of the
// associated golang-crossbuild container image for the platform.
type GolangCrossBuilder struct {
	Platform      string
	Target        string
	InDir         string
	ImageSelector ImageSelectorFunc
}

// Build executes the build inside of Docker.
func (b GolangCrossBuilder) Build() error {
	fmt.Printf(">> %v: Building for %v\n", b.Target, b.Platform)

	repoInfo, err := GetProjectRepoInfo()
	if err != nil {
		return fmt.Errorf("failed to determine repo root and package sub dir: %w", err)
	}

	mountPoint := filepath.ToSlash(filepath.Join("/go", "src", repoInfo.CanonicalRootImportPath))
	// use custom dir for build if given, subdir if not:
	cwd := repoInfo.SubDir
	if b.InDir != "" {
		cwd = b.InDir
	}
	workDir := filepath.ToSlash(filepath.Join(mountPoint, cwd))

	builderArch := runtime.GOARCH
	buildCmd, err := filepath.Rel(workDir,
		filepath.Join(mountPoint, repoInfo.SubDir, "build/mage-linux-"+builderArch))
	if err != nil {
		return fmt.Errorf("failed to determine mage-linux-%s relative path: %w", builderArch, err)
	}

	// If we're running this mage target on Windows, the path separator used in
	// buildCmd will be `\`. But the buildCmd is executed inside a Linux Docker
	// container. So we ensure that all path separators are `/`.
	buildCmd = filepath.ToSlash(buildCmd)

	dockerRun := sh.RunCmd("docker", "run")
	image, err := b.ImageSelector(b.Platform)
	if err != nil {
		return fmt.Errorf("failed to determine golang-crossbuild image tag: %w", err)
	}
	verbose := ""
	if mg.Verbose() {
		verbose = "true"
	}
	var args []string
	// There's a bug on certain debian versions:
	// https://discuss.linuxcontainers.org/t/debian-jessie-containers-have-extremely-low-performance/1272
	// basically, apt-get has a bug where will try to iterate through every possible FD as set by the NOFILE ulimit.
	// On certain docker installs, docker will set the ulimit to a value > 10^9, which means apt-get will take >1 hour.
	// This runs across all possible debian platforms, since there's no real harm in it.
	if strings.Contains(image, "debian") {
		args = append(args, "--ulimit", "nofile=262144:262144")
	}

	if runtime.GOOS != "windows" {
		args = append(args,
			"--env", "EXEC_UID="+strconv.Itoa(os.Getuid()),
			"--env", "EXEC_GID="+strconv.Itoa(os.Getgid()),
		)
	}
	if versionQualified {
		args = append(args, "--env", "VERSION_QUALIFIER="+versionQualifier)
	}
	if CrossBuildMountModcache {
		// Mount $GOPATH/pkg/mod into the container, read-only.
		hostDir := filepath.Join(build.Default.GOPATH, "pkg", "mod")
		args = append(args, "-v", hostDir+":/go/pkg/mod:ro")
	}

	args = append(args,
		"--rm",
		"--env", "GOFLAGS=-mod=readonly",
		"--env", "MAGEFILE_VERBOSE="+verbose,
		"--env", "MAGEFILE_TIMEOUT="+EnvOr("MAGEFILE_TIMEOUT", ""),
		"--env", fmt.Sprintf("SNAPSHOT=%v", Snapshot),
		"--env", fmt.Sprintf("DEV=%v", DevBuild),
		"--env", fmt.Sprintf("EXTERNAL=%v", ExternalBuild),
		"-v", repoInfo.RootDir+":"+mountPoint,
		"-w", workDir,
		image,

		// Arguments for docker crossbuild entrypoint. For details see
		// https://github.com/elastic/golang-crossbuild/blob/main/go1.17/base/rootfs/entrypoint.go.
		"--build-cmd", buildCmd+" "+b.Target,
		"--platforms", b.Platform,
	)

	return dockerRun(args...)
}

// DockerChown chowns files generated during build. EXEC_UID and EXEC_GID must
// be set in the containers environment otherwise this is a noop.
func DockerChown(path string) {
	// Chown files generated during build that are root owned.
	uid, _ := strconv.Atoi(EnvOr("EXEC_UID", "-1"))
	gid, _ := strconv.Atoi(EnvOr("EXEC_GID", "-1"))
	if uid > 0 && gid > 0 {
		log.Printf(">>> Fixing file ownership issues from Docker at path=%v", path)
		if err := chownPaths(uid, gid, path); err != nil {
			log.Println(err)
		}
	}
}

// chownPaths will chown the file and all of the dirs specified in the path.
func chownPaths(uid, gid int, path string) error {
	start := time.Now()
	numFixed := 0
	defer func() {
		log.Printf("chown took: %v, changed %d files", time.Since(start), numFixed)
	}()

	return filepath.Walk(path, func(name string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		// Get the file's UID and GID.
		stat, err := file.Wrap(info)
		if err != nil {
			return err
		}
		fileUID, _ := stat.UID()
		fileGID, _ := stat.GID()
		if uid == fileUID && gid == fileGID {
			// Skip if UID/GID are already a match.
			return nil
		}

		if err := os.Chown(name, uid, gid); err != nil {
			return fmt.Errorf("failed to chown path=%v : %w", name, err)
		}
		numFixed++
		return nil
	})
}