func StackArgs(u models.Usercorn) func(n int) ([]uint64, error) {
return func(n int) ([]uint64, error) {
sp, _ := u.RegRead(u.Arch().SP)
// starts with an empty slot
s := u.StrucAt(sp + uint64(u.Bits()/8))
ret := make([]uint64, n)
for i := 0; i < n; i++ {
var arg uint64
var err error
// TODO: simplify this when struc issue #47 is fixed
if u.Bits() == 64 {
err = s.Unpack(&arg)
} else {
var arg32 uint32
err = s.Unpack(&arg32)
arg = uint64(arg32)
}
if err != nil {
return nil, err
}
ret[i] = arg
}
return ret, nil
}
}
func setupElfAuxv(u models.Usercorn) ([]Elf64Auxv, error) {
// set up AT_RANDOM
var tmp [16]byte
if _, err := rand.Read(tmp[:]); err != nil {
return nil, err
}
randAddr, err := u.PushBytes(tmp[:])
if err != nil {
return nil, err
}
// insert platform string
platformAddr, err := u.PushBytes([]byte(u.Loader().Arch() + "\x00"))
if err != nil {
return nil, err
}
// main auxv table
auxv := []Elf64Auxv{
// TODO: set/track a page size somewhere - on Arch.OS?
{ELF_AT_PAGESZ, 4096},
{ELF_AT_BASE, u.InterpBase()},
{ELF_AT_FLAGS, 0},
{ELF_AT_ENTRY, uint64(u.BinEntry())},
{ELF_AT_UID, uint64(os.Getuid())},
{ELF_AT_EUID, uint64(os.Geteuid())},
{ELF_AT_GID, uint64(os.Getgid())},
{ELF_AT_EGID, uint64(os.Getegid())},
{ELF_AT_PLATFORM, platformAddr},
{ELF_AT_CLKTCK, 100}, // 100hz, totally fake
{ELF_AT_RANDOM, randAddr},
{ELF_AT_NULL, 0},
}
// add phdr information if present in binary
phdrOff, _, phdrCount := u.Loader().Header()
segments, _ := u.Loader().Segments()
for _, s := range segments {
if s.ContainsPhys(phdrOff) {
phdrOff += s.Addr
break
}
}
phdrEnt := 56
if u.Bits() == 32 {
phdrEnt = 56 // FIXME
}
if phdrOff > 0 {
auxv = append(auxv, []Elf64Auxv{
{ELF_AT_PHDR, phdrOff},
{ELF_AT_PHENT, uint64(phdrEnt)},
{ELF_AT_PHNUM, uint64(phdrCount)},
}...)
}
return auxv, nil
}
func packAddrs(u models.Usercorn, addrs []uint64) ([]byte, error) {
buf := make([]byte, int(u.Bits())/8*(len(addrs)+1))
pos := buf
for _, v := range addrs {
x, err := u.PackAddr(pos, v)
if err != nil {
return nil, err
}
pos = pos[len(x):]
}
return buf, nil
}
func SetupElfAuxv(u models.Usercorn) ([]byte, error) {
var buf bytes.Buffer
auxv, err := setupElfAuxv(u)
if err != nil {
return nil, err
}
options := &struc.Options{
PtrSize: int(u.Bits()),
Order: u.ByteOrder(),
}
for _, a := range auxv {
if err := struc.PackWithOptions(&buf, &a, options); err != nil {
return nil, err
}
}
return buf.Bytes(), err
}
func SetupElfAuxv(u models.Usercorn) ([]byte, error) {
var buf bytes.Buffer
auxv, err := setupElfAuxv(u)
if err != nil {
return nil, err
}
if u.Bits() == 32 {
var auxv32 Elf32Auxv
for _, a := range auxv {
auxv32.Type = uint32(a.Type)
auxv32.Val = uint32(a.Val)
if err := struc.PackWithOrder(&buf, &auxv32, u.ByteOrder()); err != nil {
return nil, err
}
}
} else {
for _, a := range auxv {
if err := struc.PackWithOrder(&buf, &a, u.ByteOrder()); err != nil {
return nil, err
}
}
}
return buf.Bytes(), err
}