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package qml
// #include <stdlib.h>
// int mprotect(void *addr, size_t len, int prot);
import "C"
import (
"bytes"
"encoding/binary"
"gopkg.in/qml.v1/cdata"
"reflect"
"unsafe"
)
const pageSize = 4096
func qmain() {
Run(func() error { tmain(); return nil })
}
func tmain() { tstub() }
func tstub() { tstub() }
func SetupTesting() {
ptr := func(f func()) uintptr { return reflect.ValueOf(f).Pointer() }
rmain, mmain := cdata.Addrs()
fset(rmain, mmain, ptr(qmain))
fset(ptr(tmain), ptr(tstub), mmain)
}
const (
protREAD = 1
protWRITE = 2
protEXEC = 4
)
func fset(target, old, new uintptr) {
pageOffset := target % pageSize
pageAddr := target - pageOffset
var mem []byte
memh := (*reflect.SliceHeader)(unsafe.Pointer(&mem))
memh.Data = pageAddr
memh.Len = pageSize * 2
memh.Cap = pageSize * 2
oldAddr := make([]byte, 8)
newAddr := make([]byte, 8)
binary.LittleEndian.PutUint64(oldAddr, uint64(old))
binary.LittleEndian.PutUint64(newAddr, uint64(new))
// BSD's syscall package misses Mprotect. Use cgo instead.
C.mprotect(unsafe.Pointer(pageAddr), C.size_t(len(mem)), protEXEC|protREAD|protWRITE)
defer C.mprotect(unsafe.Pointer(pageAddr), C.size_t(len(mem)), protEXEC|protREAD)
delta := make([]byte, 4)
for i, c := range mem[pageOffset:] {
if c == 0xe8 && int(pageOffset)+i+5 < len(mem) {
instrAddr := pageAddr + pageOffset + uintptr(i)
binary.LittleEndian.PutUint32(delta, uint32(old-instrAddr-5))
if bytes.Equal(mem[int(pageOffset)+i+1:int(pageOffset)+i+5], delta) {
binary.LittleEndian.PutUint32(mem[int(pageOffset)+i+1:], uint32(new-instrAddr-5))
return
}
}
}
panic("cannot setup qml package for testing")
}