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- /* This file is part of the program psim.
- Copyright (C) 1994-1997, Andrew Cagney <cagney@highland.com.au>
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 3 of the License, or
- (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with this program; if not, see <http://www.gnu.org/licenses/>.
-
- */
- #ifndef _EMUL_CHIRP_H_
- #define _EMUL_CHIRP_H_
- /* EMUL_CHIRP:
- The emulation of the OpenBoot client interface (as defined in 1275)
- illustrates how it is possible for PSIM to implement an interface
- that is both running in virtual memory and is called using a
- standard function call interface.
- The OpenBoot client interface is implemented by using two
- instructions:
- client_interface:
- <emul_call>
- blr
- A client program makes a function call to `client_interface' using
- the `bl' instruction. The simulator will then execute the
- <emul_call> instruction (which calls emul_chirp) and then the `blr'
- which will return to the caller.
- In addition to providing the `client_interface' entry point, while
- a client request is being handled, emul_chirp patches (well it will
- one day) the data access exception vector with a <emul_call>
- instruction. By doing this, emul_chirp is able to catch and handle
- any invalid data accesses it makes while emulating a client call.
- When such an exception occures, emul_chirp is able to recover by
- restoring the processor and then calling the clients callback
- interface so that the client can recover from the data exception.
- Handling this are the emul_chirp states:
- serving---.
- / |
- Emulation compleated ^ v Client makes call to
- - restore int vectors | | emulated interface
- ^ v - patch exception vectors
- | /
- `-emulating-. emulating the request
- / |
- | v Emulation encounters
- Client callback recovers ^ | data access exception
- from data exception and | v - re-enable vm
- returns. ^ | - call client callback
- - restart request | /
- `--faulting
- */
- extern const os_emul emul_chirp;
- #endif
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