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// Copyright 2025 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 kernel
import (
"fmt"
"io/fs"
"os"
"path"
"path/filepath"
"runtime"
"time"
"github.com/google/syzkaller/pkg/aflow"
"github.com/google/syzkaller/pkg/build"
"github.com/google/syzkaller/pkg/codesearch"
"github.com/google/syzkaller/pkg/hash"
"github.com/google/syzkaller/pkg/osutil"
"github.com/google/syzkaller/sys/targets"
)
// Build action builds the Linux kernel from the given sources,
// outputs directory with build artifacts.
var Build = aflow.NewFuncAction("kernel-builder", buildKernel)
type buildArgs struct {
KernelSrc string
KernelCommit string
KernelConfig string
}
type buildResult struct {
KernelObj string // Directory with build artifacts.
}
func BuildKernel(buildDir, srcDir, cfg string, cleanup bool) error {
if err := osutil.WriteFile(filepath.Join(buildDir, ".config"), []byte(cfg)); err != nil {
return err
}
// We don't fuzz x32 arch, and it's not very interesting,
// but building with this config and ld.lld fails with the following error:
// ld.lld: error: arch/x86/entry/vdso/vgetrandom-x32.o:(.note.gnu.property+0x0): data is too short
// ld.lld: error: arch/x86/entry/vdso/vgetcpu-x32.o:(.note.gnu.property+0x0): data is too short
configScript := filepath.Join(srcDir, "scripts", "config")
if _, err := osutil.RunCmd(time.Hour, buildDir, configScript, "-d", "X86_X32_ABI"); err != nil {
return err
}
target := targets.List[targets.Linux][targets.AMD64]
image := filepath.FromSlash(build.LinuxKernelImage(targets.AMD64))
makeArgs := build.LinuxMakeArgs(target, targets.DefaultLLVMCompiler, targets.DefaultLLVMLinker,
"ccache", buildDir, runtime.NumCPU())
const compileCommands = "compile_commands.json"
makeArgs = append(makeArgs, "-s", path.Base(image), compileCommands)
if _, err := osutil.RunCmd(time.Hour, srcDir, "make", makeArgs...); err != nil {
return aflow.FlowError(err)
}
if !cleanup {
return nil
}
// Remove main intermediate build files, we don't need them anymore
// and they take lots of space. But keep generated source files.
keepFiles := map[string]bool{
image: true,
target.KernelObject: true,
compileCommands: true,
}
return filepath.WalkDir(buildDir, func(path string, d fs.DirEntry, err error) error {
if err != nil {
return err
}
relative, err := filepath.Rel(buildDir, path)
if err != nil {
return err
}
if d.IsDir() || keepFiles[relative] || codesearch.IsSourceFile(relative) {
return nil
}
return os.Remove(path)
})
}
func buildKernel(ctx *aflow.Context, args buildArgs) (buildResult, error) {
desc := fmt.Sprintf("kernel commit %v, kernel config hash %v",
args.KernelCommit, hash.String(args.KernelConfig))
dir, err := ctx.Cache("build", desc, func(dir string) error {
return BuildKernel(dir, args.KernelSrc, args.KernelConfig, true)
})
return buildResult{KernelObj: dir}, err
}
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