Userland

[gmoney]

Does anyone know any good tut out there for switching to user land and back to kernel land?

[JamesM]

It's not difficult to switch from user land to kernel land. The difficulty comes the other way round.

switching from user land to kernel land

Code: Select all

int $0x80

syscalls are typically implemented using an interrupt service routine hook - set up eax,ebx,ecx etc to pass paramters then interrupt. The kernel handles the interrupt as a 'syscall'.

The other way is more difficult and involves an IRET to change the CPL. (current privilege level)

[JackScott]

The following from osdever.net might be useful:
http://www.osdever.net/tutorials/soft_ts.php