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// Copyright 2021 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 backend
import (
"bytes"
"debug/elf"
"fmt"
"io/fs"
"path/filepath"
"strings"
"github.com/google/syzkaller/pkg/log"
"github.com/google/syzkaller/pkg/vminfo"
"github.com/google/syzkaller/sys/targets"
)
func DiscoverModules(target *targets.Target, objDir string, moduleObj []string) (
[]*vminfo.KernelModule, error) {
module := &vminfo.KernelModule{
Path: filepath.Join(objDir, target.KernelObject),
}
textRange, err := elfReadTextSecRange(module)
if err != nil {
return nil, err
}
modules := []*vminfo.KernelModule{
// A dummy module representing the kernel itself.
{
Path: module.Path,
Size: textRange.End - textRange.Start,
},
}
if target.OS == targets.Linux {
modules1, err := discoverModulesLinux(append([]string{objDir}, moduleObj...))
if err != nil {
return nil, err
}
modules = append(modules, modules1...)
} else if len(modules) != 1 {
return nil, fmt.Errorf("%v coverage does not support modules", target.OS)
}
return modules, nil
}
func discoverModulesLinux(dirs []string) ([]*vminfo.KernelModule, error) {
paths, err := locateModules(dirs)
if err != nil {
return nil, err
}
var modules []*vminfo.KernelModule
for name, path := range paths {
if path == "" {
continue
}
log.Logf(2, "module %v -> %v", name, path)
module := &vminfo.KernelModule{
Name: name,
Path: path,
}
textRange, err := elfReadTextSecRange(module)
if err != nil {
return nil, err
}
module.Size = textRange.End - textRange.Start
modules = append(modules, module)
}
return modules, nil
}
func locateModules(dirs []string) (map[string]string, error) {
paths := make(map[string]string)
for _, dir := range dirs {
err := filepath.WalkDir(dir, func(path string, d fs.DirEntry, err error) error {
if err != nil || filepath.Ext(path) != ".ko" {
return err
}
name, err := getModuleName(path)
if err != nil {
// Extracting module name involves parsing ELF and binary data,
// let's not fail on it, we still have the file name,
// which is usually the right module name.
log.Logf(0, "failed to get %v module name: %v", path, err)
name = strings.TrimSuffix(filepath.Base(path), "."+filepath.Ext(path))
}
// Order of dirs determine priority, so don't overwrite already discovered names.
if name != "" && paths[name] == "" {
paths[name] = path
}
return nil
})
if err != nil {
return nil, err
}
}
return paths, nil
}
func getModuleName(path string) (string, error) {
file, err := elf.Open(path)
if err != nil {
return "", err
}
defer file.Close()
section := file.Section(".modinfo")
if section == nil {
return "", fmt.Errorf("no .modinfo section")
}
data, err := section.Data()
if err != nil {
return "", fmt.Errorf("failed to read .modinfo: %w", err)
}
if name := searchModuleName(data); name != "" {
return name, nil
}
section = file.Section(".gnu.linkonce.this_module")
if section == nil {
return "", fmt.Errorf("no .gnu.linkonce.this_module section")
}
data, err = section.Data()
if err != nil {
return "", fmt.Errorf("failed to read .gnu.linkonce.this_module: %w", err)
}
return string(data), nil
}
func searchModuleName(data []byte) string {
data = append([]byte{0}, data...)
key := []byte("\x00name=")
pos := bytes.Index(data, key)
if pos == -1 {
return ""
}
end := bytes.IndexByte(data[pos+len(key):], 0)
if end == -1 {
return ""
}
end = pos + len(key) + end
if end > len(data) {
return ""
}
return string(data[pos+len(key) : end])
}
func getKaslrOffset(modules []*vminfo.KernelModule, pcBase uint64) uint64 {
for _, mod := range modules {
if mod.Name == "" {
return mod.Addr - pcBase
}
}
return 0
}
// when CONFIG_RANDOMIZE_BASE=y, pc from kcov already removed kaslr_offset.
func FixModules(localModules, modules []*vminfo.KernelModule, pcBase uint64) []*vminfo.KernelModule {
kaslrOffset := getKaslrOffset(modules, pcBase)
var modules1 []*vminfo.KernelModule
for _, mod := range modules {
size := uint64(0)
path := ""
for _, modA := range localModules {
if modA.Name == mod.Name {
size = modA.Size
path = modA.Path
break
}
}
if path == "" {
continue
}
addr := mod.Addr - kaslrOffset
modules1 = append(modules1, &vminfo.KernelModule{
Name: mod.Name,
Size: size,
Addr: addr,
Path: path,
})
}
return modules1
}
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