path: root/sim/ppc/README.psim

		PSIM - model a PowerPC platform

    Copyright (C) 1994-1995, 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 2 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, write to the Free Software
    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.


This directory contains the source code to the program PSIM that
implements a model of a PowerPC platform.  PSIM can either be built
standalone or as part of the debugger GDB.


What is PSIM?

	PSIM is an ANSI C program that can be configured to model
	various PowerPC platforms.

	The platform that is modeled can vary from:

		o	A user program environment (UEA) complete
			with emulated system calls

	to

		o	A hardware platform with several processors
			interacting with each other and various
			modeled hardware devices.


Is the source code available?

	Yes.

	The source code to PSIM is available under the terms of
	the GNU Public Licence.  This allows you to distribute
	the source code for free but with certain conditions.


What motivated PSIM?

	As an idea, psim was first discussed seriously during mid
	1994.  At that time its main objectives were:


		o	good performance

			Many simulators loose out by only providing
			a binary interface to the internals.  This
			inteface eventually becomming a bottle neck
			in the simulators performance.

			It was intended that PSIM would avoid this
			problem by giving the user access to the
			full source code.

			Further, by exploiting the power of modern
			compilers it was hoped that PSIM would achieve
			good performance with out having to compromize
			its internal design.


		o	practical portability

			Rather than try to be portable to every
			C compiler on every platform, it was decided
			that PSIM would restrict its self to suporting
			ANSI compilers that included the extension
			of a long long type.

			GCC is one such compiler, consequenly PSIM
			should be portable to any machine running GCC.


		o	flexability in its design

			PSIM should allow the user to select the
			features required and customize the build
			accordingly.  By having the source code,
			the compler is able to eliminate any un
			used features of the simulator.

			After all, let the compiler do the work.


		o	SMP

			A model that allowed the simulation of
			SMP platforms with out the large overhead
			often encountered with such models.


	PSIM achieves each of these objectives.


Who would be interested in PSIM?

	o	the curious

		Using psim, gdb, gcc and binutils the curious
		user can contruct an environment that allows
		them to play with PowerPC user programs with out
		the need for real hardware.


	o	the analyst

		PSIM includes many (contributed) monitoring
		features which (unlike many other simulators)
		do not come with a great penalty in performance.

		Thus the performance analyst is able to use
		this simulator to model the inpact of changes
		to the system they are analysing.  Be that
		system a compiler or real hardware platform.

		If PSIM doesn't monitor a components of interest,
		the source code is freely available, and hence
		there is no hinderance to changing things
		to meet a specific analysts needs.


	o	the serious SW developer

		PSIM models all three levels of the PowerPC
		Architecture: UEA, VEA and OEA.  Further,
		the internal design is such that PSIM can
		be extended to suport additional
		development requirements.  Such requirements
		might include (for the UEA) a new Operating
		System emulation through to (for the OEA)
		a model of a different hardware platform.


What features does PSIM have?


	Monitoring and modeling

		PSIM includes (thanks to Michael Meissner)
		a detailed model of the various PowerPC
		implementations schedulers.


	SMP
		
		The PowerPC ISA defines SMP synchronizing instructions
		this simulator models a limited subset of their
		behavor.  Consequently, if you limit code to the
		use the modeled behavour, PSIM can be used to
		model SMP PowerPC platforms.

		People intending to use this system should study
		the code implementing the lwarx etc instructions.
		
	ENDIAN SUPORT

		PSIM implements the PowerPC's big and little (xor
		endian) modes and correctly simulates code that
		switches between these two modes.

		In addition, psim can model a true little-endian
		machine.

	ISA models (Instruction Set Architecture)

		PSIM includes a model of the UEA, VEA and OEA.  This
		inclues the time base registers (VEA) and HTAB
		and BATS (OEA).

		In addition, a preliminary model of the 64 bit
		PowerPC architecture is implemented.

	Hardware

		PSIM's internals are based around the concept
		of a Device Tree.  This tree intentionaly
		resembles that of the Device Tree found in
		OpenBoot firmware.  PSIM is flexable enough
		to allow the user to fully configure the
		actual hardware model from a device tree
		specification that is read in from a file.

		A user can either run a program using one of
		PSIM's built in hardware models specify a
		custom hardware model that should be simulated.

		A user is also able to quickly add a model
		of new hardware devices so that they can be
		included in a custom hardware model.

	Emulation

		PSIM is able (UEA) to emulate UNIX calls
		based on NetBSD abi through to (preliminary)
		the ROM rom calls found in common firmware
		(OpenBoot and BUGAPI).

	Floating point

		Preliminary suport for floating point is included.
		Real kernels don't need floating point.


Is PSIM CHRP Compliant?

	No.

	However, PSIM does include all the hooks that are needed to
	construct a model of a CHRP compliant platform.

	That is:

		o	OpenBoot client software

		o	OpenPIC interrupt controller

		o	Hooks to implement a RTAS interface

		o	the ability to add a model of each of the
			hardware devices required by a CHRP compliant
			desktop.


How do I build PSIM?

	To build PSIM you will need the following files:


	gdb-4.15.tar.gz		From your favorite GNU ftp site.
				I've also tested psim-951016 with
				gdb-4.15.1.  If you would prefer
				a graphical development environment
				then PSIM can also be built with
				gdbtk.


	ftp://ftp.ci.com.au/pub/clayton/README.pim

				This file.


	ftp://ftp.ci.com.au/pub/clayton/gdb-4.15+psim-951016.diff.gz

				This contains a few minor patches to
				gdb-4.15 so that will include psim
				when it is built.


	ftp://ftp.ci.com.au/pub/clayton/psim-test-951016.tar.gz

				(Optional) A scattering of pre-compiled
				programs that run under the simulator.


	ftp://ftp.ci.com.au/pub/clayton/gdb-4.15+psim-951016.tar.gz

				This contains the psim files proper.


	gcc			Again available from your favorite
				GNU ftp site.


	patch			Sun's patch behaves a little wierd
				and doesn't appear to like creating
				empty files.  You may want to consider
				installing gnu's patch.


	In addition, I'm slowly building up a set of useful patches
	to gdb-4.15 that are useful.  You will want to also apply
	these patches:


	ftp://ftp.ci.com.au/pub/clayton/gdb-4.15+attach.diff.gz

				Patch to gdb that allows the `attach'
				command to be used when connecting to a
				simulator.

				See that file for more information.

	ftp://ftp.ci.com.au/pub/clayton/gdb-4.15+note.diff.gz

				Patch to gdb's bfd that adds basic support
				for a .note section. OpenBoot makes
				use of a .note section when loading a
				boot image.


	Procedure:

	0.	A starting point

		$ ls -1
		gdb-4.15+psim-951016.diff.gz
		gdb-4.15+psim-951016.tar.gz
		gdb-4.15.tar.gz
		psim-test-951016.tar.gz


	1.	Unpack gdb

		$ gunzip < gdb-4.15.tar.gz | tar xf -


	2.	Change to the gdb directory, apply the psim patches and unpack
		the psim files.

		$ cd gdb-4.15

		$ gunzip < ../gdb-4.15+psim-951016.diff.gz | more
		$ gunzip < ../gdb-4.15+psim-951016.diff.gz | patch -p1

		$ gunzip < ../gdb-4.15+psim-951016.tar.gz | tar tvf -
		$ gunzip < ../gdb-4.15+psim-951016.tar.gz | tar xvf -

		You may also want to consider applying the `attach' and
		`note' patches that are available vis:

		$ gunzip < ../gdb-4.15+attach.diff.gz | more
		$ gunzip < ../gdb-4.15+attach.diff.gz | patch -p

		$ gunzip < ../gdb-4.15+note.diff.gz | more
		$ gunzip < ../gdb-4.15+note.diff.gz | patch -p


	3.	Configure gdb

		$ more gdb/README

		then something like (I assume SH):

		$ CC=gcc ./configure --target=powerpc-unknown-eabisim

		eabisim is needed as by default (because PSIM needs GCC) the
		simulator is not built.


	4.	Build

		$ make CC=gcc

		alternativly, if you are short on disk space or just want the
		simulator built:

		$ ( cd libiberty && make CC=gcc )
		$ ( cd bfd && make CC=gcc )
		$ ( cd sim/ppc && make CC=gcc )


	5.	Install

		$ make CC=gcc install

		or just

		$ cp gdb/gdb ~/bin/powerpc-unknown-eabisim-gdb
		$ cp sim/ppc/run ~/bin/powerpc-unknown-eabisim-run


Is there a more recent version of PSIM and if so, how would I build it?

	A PSIM is an ongoing development, occasional snapshots
	(that include new features) are made available.  Several of
	the more recent snapshots are:

	ftp://ftp.ci.com.au/pub/clayton/psim-951219.tar.gz

				Hopefully merges in Michael stuff
				with mine,  adds multiple emulations
				(OpenBoot and NetBSD),  revamps
				inline stuff, rearanges devices so
				that phandls and ihandles can be
				implemented.

	ftp://ftp.ci.com.au/pub/clayton/psim-951203.tar.gz

				A good snapshot

				This includes extensions from Michael
				Meissner that add monitoring of the
				PowerPC's register and bus architectures.


	To build/install one of these snapshots, you replace the
	current gdb/sim/ppc directory with the one in the update,
	re-configure and rebuild.

	Procedure:

	0.	A starting point

		$ cd gdb-4.15


	1.	Remove the old psim directory

		$ mv sim/ppc sim/old.ppc


	2.	Unpack the new one

		$ gunzip < ../psim-960105.tar.gz | tar tf -
		$ gunzip < ../psim-960105.tar.gz | tar tf -


	3.	Reconfig/rebuild (as seen above):

		$ CC=gcc ./configure --target=powerpc-unknown-eabisim
		$ make CC=gcc


Are there any example programs that can be run on PSIM?

	Psim has a simple test suite that is used to ensure
	that fixes do not introduce new bugs.  This test suite
	like psim is updated:

	ftp://ftp.ci.com.au/pub/clayton/psim-test-951218.tar.gz

				Prebuilt test programs for PSIM.
				Includes examples of UEA, VEA and
				OEA code.
				Requires gcc-2.7.2 and binutils-2.6
				to rebuild.

	ftp://ftp.ci.com.au/pub/clayton/psim-test-951016.tar.gz

				(Optional) A scattering of pre-compiled
				programs that run under the simulator.


How do I use the simulator?


	I assume that you've unpacked a psim-test archive.


	1.	As a standalone program

		Print out the users environment:

		$ powerpc-unknown-eabisim-run psim-test/uea/envp

		Print out the arguments:

		$ powerpc-unknown-eabisim-run psim-test/uea/argv a b c

		Check that sbrk works:

		$ powerpc-unknown-eabisim-run psim-test/uea/break


	2.	Example of running GDB:	

		The main thing to note is that before you can run the simulator
		you must enable it.  The example below illustrates this:

		$ powerpc-unknown-eabisim-gdb psim-test/uea/envp
		(gdb) target sim
		(gdb) load
		(gdb) break main
		(gdb) run
		.
		.
		.


	3.	Using a device tree as a description of a machine
		(I assume that you have applied the attach bug).

		$ cd psim-test/tree
		$ powerpc-unknown-eabisim-gdb
		(gdb) target sim
		(gdb) attach device-tree
		(gdb) run

		or

		$ cd psim-test/tree
		$ powerpc-unknown-eabisim-run device-tree
		

Where do I send bugs or report problems?

	There is a mailing list (subscribe through majordomo@ci.com.au) (that
	is almost never used) at:

	powerpc-psim@ci.com.au

	If I get the ftp archive updated I post a note to that mailing list.
	In addition your welcome to send bugs or problems either to me or to
	that e-mail list.


Does PSIM have any limitations or problems?

	See the file PROBLEMS (included in the distribution) for any
	outstanding issues.


Who helped?

	Thanks go to the following who each helped in some way.

	Allen Briggs, Bett Koch, David Edelsohn, Gordon Irlam,
	Michael Meissner, Bob Mercier, Richard Perini,
	Richard Stallman, Mitchele Walker