// Copyright 2018 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.

// Package build contains helper functions for building kernels/images.
package build

import (
	"bytes"
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"time"

	"github.com/google/syzkaller/pkg/osutil"
	"github.com/google/syzkaller/pkg/report"
	"github.com/google/syzkaller/pkg/vcs"
	"github.com/google/syzkaller/sys/targets"
)

// Params is input arguments for the Image function.
type Params struct {
	TargetOS     string
	TargetArch   string
	VMType       string
	KernelDir    string
	OutputDir    string
	Compiler     string
	Ccache       string
	UserspaceDir string
	CmdlineFile  string
	SysctlFile   string
	Config       []byte
}

// Information that is returned from the Image function.
type ImageDetails struct {
	Signature  string
	CompilerID string
}

// Image creates a disk image for the specified OS/ARCH/VM.
// Kernel is taken from KernelDir, userspace system is taken from UserspaceDir.
// If CmdlineFile is not empty, contents of the file are appended to the kernel command line.
// If SysctlFile is not empty, contents of the file are appended to the image /etc/sysctl.conf.
// Output is stored in OutputDir and includes (everything except for image is optional):
//  - image: the image
//  - key: ssh key for the image
//  - kernel: kernel for injected boot
//  - initrd: initrd for injected boot
//  - kernel.config: actual kernel config used during build
//  - obj/: directory with kernel object files (this should match KernelObject
//    specified in sys/targets, e.g. vmlinux for linux)
// The returned structure contains a kernel ID that will be the same for kernels
// with the same runtime behavior, and different for kernels with different runtime
// behavior. Binary equal builds, or builds that differ only in e.g. debug info,
// have the same ID. The ID may be empty if OS implementation does not have
// a way to calculate such IDs.
// Also that structure provides a compiler ID field that contains the name and
// the version of the compiler/toolchain that was used to build the kernel.
// The CompilerID field is not guaranteed to be non-empty.
func Image(params Params) (details ImageDetails, err error) {
	builder, err := getBuilder(params.TargetOS, params.TargetArch, params.VMType)
	if err != nil {
		return
	}
	if err = osutil.MkdirAll(filepath.Join(params.OutputDir, "obj")); err != nil {
		return
	}
	if len(params.Config) != 0 {
		// Write kernel config early, so that it's captured on build failures.
		if err = osutil.WriteFile(filepath.Join(params.OutputDir, "kernel.config"), params.Config); err != nil {
			err = fmt.Errorf("failed to write config file: %v", err)
			return
		}
	}
	details, err = builder.build(params)
	if details.CompilerID == "" {
		// Fill in the compiler info even if the build failed.
		var idErr error
		details.CompilerID, idErr = compilerIdentity(params.Compiler)
		if err == nil {
			err = idErr
		} // Try to preserve the build error otherwise.
	}
	if err != nil {
		err = extractRootCause(err, params.TargetOS, params.KernelDir)
		return
	}
	if key := filepath.Join(params.OutputDir, "key"); osutil.IsExist(key) {
		if err := os.Chmod(key, 0600); err != nil {
			return details, fmt.Errorf("failed to chmod 0600 %v: %v", key, err)
		}
	}
	return
}

func Clean(targetOS, targetArch, vmType, kernelDir string) error {
	builder, err := getBuilder(targetOS, targetArch, vmType)
	if err != nil {
		return err
	}
	return builder.clean(kernelDir, targetArch)
}

type KernelError struct {
	Report     []byte
	Output     []byte
	Recipients vcs.Recipients
	guiltyFile string
}

func (err *KernelError) Error() string {
	return string(err.Report)
}

type builder interface {
	build(params Params) (ImageDetails, error)
	clean(kernelDir, targetArch string) error
}

func getBuilder(targetOS, targetArch, vmType string) (builder, error) {
	var supported = []struct {
		OS    string
		archs []string
		vms   []string
		b     builder
	}{
		{targets.Linux, []string{targets.AMD64}, []string{"gvisor"}, gvisor{}},
		{targets.Linux, []string{targets.AMD64}, []string{"gce", "qemu"}, linux{}},
		{targets.Linux, []string{targets.ARM, targets.ARM64, targets.I386, targets.MIPS64LE,
			targets.PPC64LE, targets.S390x, targets.RiscV64}, []string{"qemu"}, linux{}},
		{targets.Fuchsia, []string{targets.AMD64, targets.ARM64}, []string{"qemu"}, fuchsia{}},
		{targets.Akaros, []string{targets.AMD64}, []string{"qemu"}, akaros{}},
		{targets.OpenBSD, []string{targets.AMD64}, []string{"gce", "vmm"}, openbsd{}},
		{targets.NetBSD, []string{targets.AMD64}, []string{"gce", "qemu"}, netbsd{}},
		{targets.FreeBSD, []string{targets.AMD64}, []string{"gce", "qemu"}, freebsd{}},
		{targets.Darwin, []string{targets.AMD64}, []string{"qemu"}, darwin{}},
		{targets.TestOS, []string{targets.TestArch64}, []string{"qemu"}, test{}},
	}
	for _, s := range supported {
		if targetOS == s.OS {
			for _, arch := range s.archs {
				if targetArch == arch {
					for _, vm := range s.vms {
						if vmType == vm {
							return s.b, nil
						}
					}
				}
			}
		}
	}
	return nil, fmt.Errorf("unsupported image type %v/%v/%v", targetOS, targetArch, vmType)
}

func compilerIdentity(compiler string) (string, error) {
	if compiler == "" {
		return "", nil
	}

	bazel := strings.HasSuffix(compiler, "bazel")

	arg, timeout := "--version", time.Minute
	if bazel {
		// Bazel episodically fails with 1 min timeout.
		arg, timeout = "", 10*time.Minute
	}
	output, err := osutil.RunCmd(timeout, "", compiler, arg)
	if err != nil {
		return "", err
	}
	for _, line := range strings.Split(string(output), "\n") {
		if bazel {
			// Strip extracting and log lines...
			if strings.Contains(line, "Extracting Bazel") {
				continue
			}
			if strings.HasPrefix(line, "INFO: ") {
				continue
			}
			if strings.HasPrefix(line, "WARNING: ") {
				continue
			}
		}

		return strings.TrimSpace(line), nil
	}
	return "", fmt.Errorf("no output from compiler --version")
}

func extractRootCause(err error, OS, kernelSrc string) error {
	if err == nil {
		return nil
	}
	verr, ok := err.(*osutil.VerboseError)
	if !ok {
		return err
	}
	reason, file := extractCauseInner(verr.Output, kernelSrc)
	if len(reason) == 0 {
		return err
	}
	kernelErr := &KernelError{
		Report:     reason,
		Output:     verr.Output,
		guiltyFile: file,
	}
	if file != "" && OS == targets.Linux {
		maintainers, err := report.GetLinuxMaintainers(kernelSrc, file)
		if err != nil {
			kernelErr.Output = append(kernelErr.Output, err.Error()...)
		}
		kernelErr.Recipients = maintainers
	}
	return kernelErr
}

func extractCauseInner(s []byte, kernelSrc string) ([]byte, string) {
	lines := extractCauseRaw(s)
	const maxLines = 20
	if len(lines) > maxLines {
		lines = lines[:maxLines]
	}
	var stripPrefix []byte
	if kernelSrc != "" {
		stripPrefix = []byte(kernelSrc)
		if stripPrefix[len(stripPrefix)-1] != filepath.Separator {
			stripPrefix = append(stripPrefix, filepath.Separator)
		}
	}
	file := ""
	for i := range lines {
		if stripPrefix != nil {
			lines[i] = bytes.Replace(lines[i], stripPrefix, nil, -1)
		}
		if file == "" {
			for _, fileRe := range fileRes {
				match := fileRe.FindSubmatch(lines[i])
				if match != nil {
					file = string(match[1])
					if file[0] != '/' {
						break
					}
					// We already removed kernel source prefix,
					// if we still have an absolute path, it's probably pointing
					// to compiler/system libraries (not going to work).
					file = ""
				}
			}
		}
	}
	file = strings.TrimPrefix(file, "./")
	if strings.HasSuffix(file, ".o") {
		// Linker may point to object files instead.
		file = strings.TrimSuffix(file, ".o") + ".c"
	}
	res := bytes.Join(lines, []byte{'\n'})
	// gcc uses these weird quotes around identifiers, which may be
	// mis-rendered by systems that don't understand utf-8.
	res = bytes.Replace(res, []byte("‘"), []byte{'\''}, -1)
	res = bytes.Replace(res, []byte("’"), []byte{'\''}, -1)
	return res, file
}

func extractCauseRaw(s []byte) [][]byte {
	weak := true
	var cause [][]byte
	dedup := make(map[string]bool)
	for _, line := range bytes.Split(s, []byte{'\n'}) {
		for _, pattern := range buildFailureCauses {
			if !pattern.pattern.Match(line) {
				continue
			}
			if weak && !pattern.weak {
				cause = nil
				dedup = make(map[string]bool)
			}
			if dedup[string(line)] {
				continue
			}
			dedup[string(line)] = true
			if cause == nil {
				weak = pattern.weak
			}
			cause = append(cause, line)
			break
		}
	}
	return cause
}

type buildFailureCause struct {
	pattern *regexp.Regexp
	weak    bool
}

var buildFailureCauses = [...]buildFailureCause{
	{pattern: regexp.MustCompile(`: error: `)},
	{pattern: regexp.MustCompile(`ERROR: `)},
	{pattern: regexp.MustCompile(`: fatal error: `)},
	{pattern: regexp.MustCompile(`: undefined reference to`)},
	{pattern: regexp.MustCompile(`: multiple definition of`)},
	{pattern: regexp.MustCompile(`: Permission denied`)},
	{pattern: regexp.MustCompile(`: not found`)},
	{pattern: regexp.MustCompile(`^([a-zA-Z0-9_\-/.]+):[0-9]+:([0-9]+:)?.*(error|invalid|fatal|wrong)`)},
	{pattern: regexp.MustCompile(`FAILED unresolved symbol`)},
	{pattern: regexp.MustCompile(`No rule to make target`)},
	{weak: true, pattern: regexp.MustCompile(`: final link failed: `)},
	{weak: true, pattern: regexp.MustCompile(`collect2: error: `)},
	{weak: true, pattern: regexp.MustCompile(`FAILED: Build did NOT complete`)},
}

var fileRes = []*regexp.Regexp{
	regexp.MustCompile(`^([a-zA-Z0-9_\-/.]+):[0-9]+:([0-9]+:)? `),
	regexp.MustCompile(`^(?:ld: )?(([a-zA-Z0-9_\-/.]+?)\.o):`),
	regexp.MustCompile(`; (([a-zA-Z0-9_\-/.]+?)\.o):`),
}