Syscall bugs that force server to use IPC

November 19, 1993

A few unfortunate IPC dependecies remain in the server.

vm_write

mig_vm_write is called explicitly in uxkern/user_reply_msg.c This is the copyout code to move data out to a user task in response to a syscall or signal. This data used to go in a reply message to the emulator. Without an emulator we have to stuff it in the user task with vm_write.

vm_write usually moves data in PAGESIZE chunks but thats not the case with copyout. A bcopy in syscall_vm_write gets a dreaded "Bad Access" exception trying to move small message. As of August, syscall_vm_write was

the same function as mig_vm_write. mig_vm_write didn't choke on the small write so that is how the no-emulatore server got finished. I think mef did something to optimize bcopy since August so I do not know the current state of vm_write.

Todo: Rationalize the vm_read/write code so the syscall version can be used rather than the IPC version.

device_*

savage says some of the device_ calls only exist in IPC form. If so, syscall versions need to be added to MK. I suspect the device_*_inband calls. Ask savage.

becker@cs.washington.edu