goloader

README

Goloader

Goloader can load and run Golang code at runtime.

Forked from dearplain/goloader, Take over maintenance because the original author is not in maintenance

How does it work?

Goloader works like a linker: it relocates the address of symbols in an object file, generates runnable code, and then reuses the runtime function and the type pointer of the loader.

Goloader provides some information to the runtime and gc of Go, which allows it to work correctly with them.

Please note that Goloader is not a scripting engine. It reads the output of Go compiler and makes them runnable. All features of Go are supported, and run just as fast and lightweight as native Go code.

Comparison with plugin

Goloader reuses the Go runtime, which makes it much smaller. And code loaded by Goloader is unloadable.

Goloader is debuggable, and supports pprof tool(Yes, you can see code loaded by Goloader in pprof).

Build

Make sure you're using go >= 1.8.

First, execute the following command, then do build and test. This is because Goloader relies on the internal package, which is forbidden by the Go compiler.

cp -r $GOROOT/src/cmd/internal $GOROOT/src/cmd/objfile

Examples

go build github.com/pkujhd/goloader/examples/loader

go tool compile $GOPATH/src/github.com/pkujhd/goloader/examples/schedule/schedule.go
./loader -o schedule.o -run main.main -times 10

go tool compile $GOPATH/src/github.com/pkujhd/goloader/examples/base/base.go
./loader -o base.o -run main.main

go tool compile $GOPATH/src/github.com/pkujhd/goloader/examples/http/http.go
./loader -o http.o -run main.main

go install github.com/pkujhd/goloader/examples/basecontext
./loader -o $GOPATH/pkg/`go env GOOS`_`go env GOARCH`/github.com/pkujhd/goloader/examples/basecontext.a:github.com/pkujhd/goloader/examples/basecontext -o inter.o

#build multiple go files
go tool compile -I $GOPATH/pkg/darwin_amd64 -o test.o test1.go test2.go
./loader -o test.o -run main.main

Warning

This has currently only been tested and developed on Golang 1.8-1.13 (x64/x86, darwin, linux, windows).

Documentation

Index

• Constants
• func GetFunctionName(i interface{}) string
• func Mmap(size int) ([]byte, error)
• func Munmap(b []byte) (err error)
• func RegFunc(symPtr map[string]uintptr, name string, f interface{})
• func RegItab(symPtr map[string]uintptr, name string, addr uintptr)
• func RegSymbol(symPtr map[string]uintptr)
• func RegTLS(symPtr map[string]uintptr, offset int)
• func RegType(symPtr map[string]uintptr, name string, typ interface{})
• func RegTypes(symPtr map[string]uintptr, interfaces ...interface{})
• func ToType(typ reflect.Type) *_type
• type CodeModule
  • func Load(code *CodeReloc, symPtr map[string]uintptr) (*CodeModule, error)
  • func (cm *CodeModule) Unload()
• type CodeReloc
  • func ReadObj(f *os.File) (*CodeReloc, error)
  • func ReadObjs(files []string, pkgPath []string) (*CodeReloc, error)
• type Module
• type Reloc
• type SymData

Constants

const (
	// R_TLS_LE, used on 386, amd64, and ARM, resolves to the offset of the
	// thread-local symbol from the thread local base and is used to implement the
	// "local exec" model for tls access (r.Sym is not set on intel platforms but is
	// set to a TLS symbol -- runtime.tlsg -- in the linker when externally linking).
	R_TLS_LE    = 16
	R_CALL      = 8
	R_CALLARM   = 9
	R_CALLARM64 = 10
	R_CALLIND   = 11
	R_PCREL     = 15
	R_ADDR      = 1
	// R_ADDRARM64 relocates an adrp, add pair to compute the address of the
	// referenced symbol.
	R_ADDRARM64 = 3
	// R_ADDROFF resolves to a 32-bit offset from the beginning of the section
	// holding the data being relocated to the referenced symbol.
	R_ADDROFF = 5
	// R_WEAKADDROFF resolves just like R_ADDROFF but is a weak relocation.
	// A weak relocation does not make the symbol it refers to reachable,
	// and is only honored by the linker if the symbol is in some other way
	// reachable.
	R_WEAKADDROFF = 6
	// R_METHODOFF resolves to a 32-bit offset from the beginning of the section
	// holding the data being relocated to the referenced symbol.
	// It is a variant of R_ADDROFF used when linking from the uncommonType of a
	// *rtype, and may be set to zero by the linker if it determines the method
	// text is unreachable by the linked program.
	R_METHODOFF = 24
)

copy from $GOROOT/src/cmd/internal/objabi/reloctype.go

const (
	// An otherwise invalid zero value for the type
	Sxxx = iota
	// Executable instructions
	STEXT
	// Read only static data
	SRODATA
	// Static data that does not contain any pointers
	SNOPTRDATA
	// Static data
	SDATA
	// Statically data that is initially all 0s
	SBSS
	// Statically data that is initially all 0s and does not contain pointers
	SNOPTRBSS
	// Thread-local data that is initally all 0s
	STLSBSS
	// Debugging data
	SDWARFINFO
	SDWARFRANGE
)

copy from $GOROOT/src/cmd/internal/objabi/symkind.go

const (
	TLSNAME        = "(TLS)"
	R_CALLIND_NAME = "R_CALLIND"
)

const PtrSize = 4 << (^uintptr(0) >> 63)

Functions

func GetFunctionName

func GetFunctionName(i interface{}) string

func Mmap

func Mmap(size int) ([]byte, error)

func Munmap

func Munmap(b []byte) (err error)

func RegFunc

func RegFunc(symPtr map[string]uintptr, name string, f interface{})

func RegItab

func RegItab(symPtr map[string]uintptr, name string, addr uintptr)

func RegSymbol

func RegSymbol(symPtr map[string]uintptr)

func RegTLS

func RegTLS(symPtr map[string]uintptr, offset int)

func RegType

func RegType(symPtr map[string]uintptr, name string, typ interface{})

func RegTypes

func RegTypes(symPtr map[string]uintptr, interfaces ...interface{})

func ToType

func ToType(typ reflect.Type) *_type

Types

type CodeModule

type CodeModule struct {
	Syms     map[string]uintptr
	CodeByte []byte
	Module   interface{}
	// contains filtered or unexported fields
}

func Load

func Load(code *CodeReloc, symPtr map[string]uintptr) (*CodeModule, error)

func (*CodeModule) Unload

func (cm *CodeModule) Unload()

type CodeReloc

type CodeReloc struct {
	Code    []byte
	Data    []byte
	Mod     Module
	Syms    []SymData
	SymMap  map[string]int
	GCObjs  map[string]uintptr
	FileMap map[string]int
}

CodeReloc dispatch and load CodeReloc struct via network is OK

func ReadObj

func ReadObj(f *os.File) (*CodeReloc, error)

func ReadObjs

func ReadObjs(files []string, pkgPath []string) (*CodeReloc, error)

type Module

type Module struct {
	// contains filtered or unexported fields
}

type Reloc

type Reloc struct {
	Offset int
	SymOff int
	Size   int
	Type   int
	Add    int
}

type SymData

type SymData struct {
	Name   string
	Kind   int
	Offset int
	Reloc  []Reloc
}