Restoring a state with MMIO causes an exception

Start in qiling/os/memory.py around restore(), especially the RAM and MMIO restoration loops at the linked lines. Run the sample that maps MMIO, saves state, and restores it, then verify that restoring the state no longer raises the Unicorn invalid-mapping exception and that the MMIO region is restored.

Describe the bug
Mapping an MMIO region, then saving the qiling state and then restoring the qiling state causes an exception. See the script below.

Sample Code

import qiling
from qiling.const import QL_ARCH

ql = qiling.Qiling(code=bytes(0x1000), archtype=QL_ARCH.ARM, ostype='linux')
ql.mem.map_mmio(addr=0, size=0x1000, read_cb=lambda *args: 0, write_cb=lambda *args: None)
qiling_state = ql.save()

# ...

ql.restore(qiling_state)

Actual behavior

$ python main.py 
Traceback (most recent call last):
  File "main.py", line 15, in <module>
    ql.restore(qiling_state)
  File "~/.local/lib/python3.8/site-packages/qiling/core.py", line 783, in restore
    self.mem.restore(saved_states["mem"])
  File "~/.local/lib/python3.8/site-packages/qiling/os/memory.py", line 275, in restore
    self.map_mmio(lbound, ubound - lbound, read_cb, write_cb, info=label)
  File "~/.local/lib/python3.8/site-packages/qiling/os/memory.py", line 547, in map_mmio
    self.ql.uc.mmio_map(addr, size, __mmio_read, read_cb, __mmio_write, write_cb)
  File "~/.local/lib/python3.8/site-packages/unicorn/unicorn.py", line 527, in mmio_map
    raise UcError(status)
unicorn.unicorn.UcError: Invalid memory mapping (UC_ERR_MAP)

Expected behavior
No exception.

Additional context
An exception occurs in unicorn because the MMIO memory region is mapped, while it is already mapped. I think the best way to handle this is to first unmap the existing memory region, and then map the MMIO region. I don't think simply ignoring the MMIO region if it overlaps with a region that is already mapped is possible, since the read/write handler might be different.

https://github.com/qilingframework/qiling/blob/f3e66ec290b8c7a0ee60bc2f2715ddc6e9389216/qiling/os/memory.py#L280-L299

Proposed patch

    def restore(self, mem_dict):
        """Restore saved memory content.
        """
        # clear existing memory map
        self.unmap_all()

        # restore RAM
        for lbound, ubound, perms, label, data in mem_dict['ram']:
            self.ql.log.debug(f'restoring memory range: {lbound:#08x} {ubound:#08x} {label}')

            size = ubound - lbound
            if self.is_available(lbound, size):
                self.ql.log.debug(f'mapping {lbound:#08x} {ubound:#08x}, mapsize = {size:#x}')
                self.map(lbound, size, perms, label)

            self.ql.log.debug(f'writing {len(data):#x} bytes at {lbound:#08x}')
            self.write(lbound, data)

        # restore MMIO
        for lbound, ubound, perms, label, read_cb, write_cb in mem_dict['mmio']:
            self.ql.log.debug(f"restoring mmio range: {lbound:#08x} {ubound:#08x} {label}")

            #TODO: Handle overlapped MMIO?
            self.map_mmio(lbound, ubound - lbound, read_cb, write_cb, info=label)