// 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"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"runtime"
	"strings"
	"time"

	"github.com/google/syzkaller/pkg/debugtracer"
	"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 and Clean functions.
type Params struct {
	TargetOS     string
	TargetArch   string
	VMType       string
	KernelDir    string
	OutputDir    string
	Compiler     string
	Make         string
	Linker       string
	Ccache       string
	UserspaceDir string
	CmdlineFile  string
	SysctlFile   string
	Config       []byte
	Tracer       debugtracer.DebugTracer
	BuildCPUs    int // If 0, all CPUs will be used.
	Build        json.RawMessage
}

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

func sanitize(params *Params) {
	if params.Tracer == nil {
		params.Tracer = &debugtracer.NullTracer{}
	}
	if params.BuildCPUs == 0 {
		params.BuildCPUs = runtime.NumCPU()
	}
}

// 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) {
	sanitize(&params)
	var builder builder
	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: %w", 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: %w", key, err)
		}
	}
	return
}

func Clean(params Params) error {
	sanitize(&params)
	builder, err := getBuilder(params.TargetOS, params.TargetArch, params.VMType)
	if err != nil {
		return err
	}
	return builder.clean(params)
}

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

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

type InfraError struct {
	Title  string
	Output []byte
}

func (e InfraError) Error() string {
	if len(e.Output) > 0 {
		return fmt.Sprintf("%s: %s", e.Title, e.Output)
	}
	return e.Title
}

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

func getBuilder(targetOS, targetArch, vmType string) (builder, error) {
	if targetOS == targets.Linux {
		switch vmType {
		case targets.GVisor:
			return gvisor{}, nil
		case "cuttlefish":
			return cuttlefish{}, nil
		case "proxyapp:android":
			return android{}, nil
		case targets.Starnix:
			return starnix{}, nil
		}
	}
	builders := map[string]builder{
		targets.Linux:   linux{},
		targets.Fuchsia: fuchsia{},
		targets.OpenBSD: openbsd{},
		targets.NetBSD:  netbsd{},
		targets.FreeBSD: freebsd{},
		targets.Darwin:  darwin{},
		targets.TestOS:  test{},
	}
	if builder, ok := builders[targetOS]; ok {
		return builder, 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.
		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
			}
			if strings.Contains(line, "Downloading https://releases.bazel") {
				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
	}
	var verr *osutil.VerboseError
	if !errors.As(err, &verr) {
		return err
	}
	reason, file := extractCauseInner(verr.Output, kernelSrc)
	if len(reason) == 0 {
		return err
	}
	// Don't report upon SIGKILL for Linux builds.
	if OS == targets.Linux && string(reason) == "Killed" && verr.ExitCode == 137 {
		return &InfraError{
			Title:  string(reason),
			Output: verr.Output,
		}
	}
	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.ReplaceAll(lines[i], stripPrefix, nil)
		}
		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.ReplaceAll(res, []byte("‘"), []byte{'\''})
	res = bytes.ReplaceAll(res, []byte("’"), []byte{'\''})
	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(`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(`^([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`)},
	{pattern: regexp.MustCompile(`^Killed$`)},
	{pattern: regexp.MustCompile(`error\[.*?\]: `)},
	{weak: true, pattern: regexp.MustCompile(`: not found`)},
	{weak: true, pattern: regexp.MustCompile(`: final link failed: `)},
	{weak: true, pattern: regexp.MustCompile(`collect2: error: `)},
	{weak: true, pattern: regexp.MustCompile(`(ERROR|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):`),
}