func enterUsermode(u models.Usercorn) error {
// move CPU from System to User mode
modeSwitch := []byte{
0x00, 0x00, 0x0f, 0xe1, // mrs r0, cpsr
0x1f, 0x00, 0xc0, 0xe3, // bic r0, r0, $0x1f
0x10, 0x00, 0x80, 0xe3, // orr r0, r0, $0x10
0x00, 0xf0, 0x21, 0xe1, // msr cpsr_c, r0
}
mmap, err := u.Mmap(0, uint64(len(modeSwitch)))
if err != nil {
return err
}
defer u.MemUnmap(mmap.Addr, mmap.Size)
end := mmap.Addr + uint64(len(modeSwitch))
err = u.RunShellcodeMapped(mmap, modeSwitch,
map[int]uint64{uc.ARM_REG_LR: end},
[]int{uc.ARM_REG_R0, uc.ARM_REG_LR, uc.ARM_REG_SP},
)
return err
}