upstream/0.4.4/TODO

$Id: TODO,v 1.453 2007/02/19 01:34:42 debug Exp $

-------------------------------------------------------------------------------

Fix after the 0.4.4 release:
        Fix the PowerPC DECR interrupt speed!

-------------------------------------------------------------------------------

Possible (relatively large) work packages to concentrate on in the future:

  x)  SMP:
        Get SMP working again. It is pretty much broken since I started
        the conversion from the old bintrans system to the new dyntrans system.
        Add better Test machine demos for SMP in the demos directory.

  x)  Network:
        Redesign of the networking subsystem, at least the NAT translation
        part. The current way of allowing raw ethernet frames to be
        transfered to/from the emulator via UDP should probably be extended
        to allow the frames to be transmitted other ways as well.
        Also adding support for connecting ttys (either to xterms, or to
        pipes/sockets etc, or even to PPP->NAT or SLIP->NAT :-).

  x)  PCI:
        Pretty much everything related to runtime configuration, device
        slots, interrupts, whatever. The current code is very hardcoded
        and ugly.

  x)  Debugging:
        Think more about SMP debugging, etc. Right now, the
        debugger is a mess. Also, a better connection to GDB would be
        very nice to have.

  x)  Userland emulation:
        Primary goals would be NetBSD and Linux syscall emulation.

And of course, there are _LOTS_ of minor TODOs spread out throughout
the source code, which must be fixed sooner or later.

-------------------------------------------------------------------------------

Some other things, in random order, that I'd like to fix: (Some items in 
this list are probably out-to-date by now.)

Dyntrans:
        x)  Instruction combination collisions? How to avoid easily...
        x)  Think about how to do both SHmedia and SHcompact in a reasonable
            way! (Or AMD64 long/protected/real, for that matter.)
        x)  68K emulation; think about how to do variable instruction
            lengths across page boundaries.
        x)  Dyntrans with valgrind-inspired memory checker. (In memory_rw,
            it would be reasonably simple to add; in each individual fast
            load/store routine = a lot more work, and it would become
            kludgy very fast.)
        x)  Dyntrans with SMP... lots of work to be done here.
        x)  Dyntrans with cache emulation... lots of work here as well.
        o)  dev_mp doesn't work well with dyntrans yet
        o)  In general, IPIs, CAS, LL/SC etc must be made to work with dyntrans
        x)  Redesign/rethink the delay slot mechanism used for e.g. MIPS,
                so that it caches a translation (that is, an instruction
                word and the instr_call it was translated to the last
                time), so that it doesn't need to do slow
                to_be_translated for each end of page?
        x)  Program Counter statistics:
                Per machine? What about SMP? All data to the same file?
                A debugger command should be possible to use to enable/
                disable statistics gathering.
                Configuration file option!
        x)  Breakpoints:
                o) Physical vs virtual addresses!
                o) 32-bit vs 64-bit sign extension for MIPS, and others?
        x)  INVALIDATION should cause translations in _all_ cpus to be
            invalidated, e.g. on a write to a write-protected page
            (containing code)
        x)  16-bit encodings? (MIPS16, ARM Thumb, 32-bit SH on SH64)
        x)  Lots of other stuff: see src/cpus/README_DYNTRANS
        x)  true recompilation backend? think carefully about this.
                o)  abstract syntax for emitting opcopdes
                o)  convert into native code only after an entire
                        block has been translated? probably best.
                o)  x86/amd64 code generator can be very similar... perhaps
                o)  branches to already translated code blocks can
                        link the blocks together
                o)  load/store are the most important.

Simple Valgrind-like checks?
        o)  Mark every address with bits which tell whether or not the address
            has been written to.
        o)  What should happen when programs are loaded?  Text/data, bss (zero
            filled). But stack space and heap is uninitialized.
        o)  Uninitialized local variables:
                A load from a place on the stack which has not previously
                been stored to => warning. Increasing the stack pointer using
                any available means should reset the memory to uninitialized.
        o)  If calls to malloc() and free() can be intercepted:
                o)  Access to a memory area after free() => warning.
                o)  Memory returned by malloc() is marked as not-initialized.
                o)  Non-passive, but good to have: Change the argument
                    given to malloc, to return a slightly larger memory
                    area, i.e.  margin_before + size + margin_after,
                    and return the pointer  + margin_before.
                    Any access to the margin_before or _after space results
                    in warnings. (free() must be modified to free the
                    actually allocated address.)

MIPS:
        o)  Nicer MIPS status bits in register dumps.
        o)  Alignment exceptions.
        o)  Floating point exception correctness.
        o)  Fix this? Triggered by NetBSD/sgimips? Hm:
                to_be_translated(): TODO: unimplemented instruction:
                000000000065102c: 00200800 (d)  rot_00  at,zr,0
        o)  Some more work on opcodes.
                x) MIPS64 revision 2.
                        o)  Find out which actual CPUs implement the rev2 ISA!
                        o)  DROTR32 and similar MIPS64 rev 2 instructions,
                            which have a rotation bit which differs from
                            previous ISAs.
                        o)  EI and DI instructions for MIPS64/32 rev 2.
                            NOTE: These are _NOT_ the same as for R5900!
                x) _MAYBE_ TX79 and R5900 actually differ in their
                   opcodes? Check this carefully!
        o)  Dyntrans: Count register updates are probably not 100% correct yet.
        o)  Refactor code for performance and readability/maintainability.
        o)  (Re)implement 128-bit loads/stores for R5900.
        o)  R4000 and others:
                x)  watchhi/watchlo exceptions, and other exception
                    handling details
        o)  R10000 and others:  (R12000, R14000 ?)
                x)  The code before the line
                        /*  reg[COP0_PAGEMASK] = cpu->cd.mips.coproc[0]->tlbs[0].mask & PAGEMASK_MASK;  */
                    in cpu_mips.c is not correct for R10000 according to
                    Lemote's Godson patches for GXemul. TODO: Go through all
                    register definitions according to http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi/hdwr/bks/SGI_Developer/books/R10K_UM/sgi_html/t5.Ver.2.0.book_263.html#HEADING334
                    and make sure everything works with R10000.
                    Then test with OpenBSD/sgi?
                x)  memory space, exceptions, ...
                x)  use cop0 framemask for tlb lookups
                    (http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi/hdwr/bks/SGI_Developer/books/R10K_UM/sgi_html/t5.Ver.2.0.book_284.html)

SuperH:
        x)  SH4 interrupt controller:
                x)  Implement correct priorities of interrupts
        x)  SH4 DMA (0xffa00000)
        x)  SH4 UBC (0xff200000)
        x)  Store queues can copy 32 bytes at a time, there's no need to
            copy individual 32-bit words. (Performance improvement.)
        x)  SH4 BSC (Bus State Controller)
        x)  SH4 RTC: Read the host's clock.
        x)  SH4 SCIF: Serial _interrupts_
        x)  Instruction tracing should include symbols for branch targets,
            and so on, to make the output more human readable.
        x)  NetBSD/evbsh3, dreamcast, mmeye, hpcsh! Linux?
        x)  Replace pc-relative loads with immediate load, if within the
            same page. (Similar to the same optimization for ARM.)
        x)  Floating point speed!
        x)  Floating point exception correctness.
        x)  Think carefully about how to implement SH5/SH64 (for evbsh5).

Dreamcast:
        x)  G2 DMA
        x)  LAN adapter (dev_mb8696x.c).  NetBSD root-on-nfs.
        x)  PVR:  Lots of stuff. See dev_pvr.c.
        x)  GDROM
        x)  Modem
        x)  PCI bridge/bus?
        x)  Maple bus:
                x)  Correct controller input
                x)  Mouse input
        x)  Software emulation of BIOS calls:
                x)  GD-ROM emulation: Use the GDROM device.
                x)  Use the VGA font as a fake ROM font. (Better than
                    nothing.)
        x)  Linux/dreamcast? (The gentoo kernel currently crashes.)
        x)  Make as many as possible of the KOS examples run!
        x)  More homebrew demos/games.
        x)  SPU: Sound emulation (ARM cpu).
        x)  VME processor emulation? "(Sanyo LC8670 "Potato")" according to
            Wikipedia, LC86K87 according to Comstedt's page. See
            http://www.maushammer.com/vmu.html for a good description of
            the differences between LC86104C and the one used in the VME.

Transputer:
        x)  Implement support for Helios binaries.
        x)  Stack and register contents at startup?
        x)  Figure out how to boot an entire Helios distribution.
        x)  Implement all instructions. :)

RCA1802/RCA1805, CHIP8:
        x)  CHIP8 -> RCA180x conversion
                x)  Think about how to do dual-mode, variable-instr-length
                    ISAs, and switch between modes.
                x)  1805 "extended" opcode -> trigger CHIP8 emulation?
                        That is, all calls 0NNN could point to 0x68 opcodes,
                        which, if running on a 1802 in CHIP8-emulation-mode,
                        would be manually interpreted.
                x)  Better solution:
                        CHIP8 calls to 00xx => handle at high level,
                              calls to 0xxx in general = call 180X machine code
                                (0000 = reboot?)
        x)  1802 info: http://www.nyx.net/~lturner/public_html/Cosmac.html
            and:  http://www.elf-emulation.com/1802.html
        x)  1805 extended opcodes: Implement at least disassembly support!
        x)  Keyboard input.
        x)  Sound (beep only).
        x)  Slow-down to correct speed? Wikipedia: "it was usually operated
            at 3.58 MHz/2 to suit the requirements of the 1861 chip which
            gave a speed of a little over 100,000 instructions per second"
            (Note that _CHIP8_ emulation would then be even slower.)
        x)  SCHIP48 (Super) emulation:
                Some more opcodes, 128x64 framebuffer, larger
                sprites and fonts.

Alpha:
        x)  OSF1 PALcode, Virtual memory support.
        x)  PALcode replacement! PAL1E etc opcodes...?
        x)  Interrupt/exception/trap handling.
        x)  Floating point exception correctness.
        x)  More work on bootup memory and register contents.
        x)  More Alpha machine types, so it could work with
            OpenBSD, FreeBSD, and Linux too?

SPARC:
        o)  Implement Adress space identifiers; load/stores etc.
        o)  Save/restore register windows etc! Both v9 and pre-v9!
        o)  Finish the subcc and addcc flag computation code.
        o)  Add more registers (floating point, control regs etc)
        o)  Exception/trap handling.
        o)  Disassemly of some more instructions?
        o)  Are sll etc 32-bit sign-extending or zero-extending?
        o)  Finish the GDB register stuff.
        x)  Floating point exception correctness.
        o)  SPARC v8, v7 etc?

Debugger:
        o)  How does SMP debugging work? Does it simply use "threads"?
                What if the guest OS (running on an emulated SMP machine)
                has a usertask running, with userland threads?
        o)  Try to make the debugger more modular and, if possible, reentrant!
        o)  Remove the emul command? (But show network info if showing
                machines?)
        o)  Evaluate expressions within []? That would allow stuff like
                cpu[x] where x is an expression.
        o)  Settings:
                x)  Special handlers for Write!
                        +)  MIPS coproc regs
                        +)  Alpha/MIPS/SPARC zero registers
                        +)  x86 64/32/16-bit registers
                x)  Value formatter for resulting output.
        o)  see src/debugger.c for more

POWER/PowerPC:
        x)  Fix DECR timer speed, so it matches the host.
        x)  NetBSD/prep 3.x triggers a possible bug in the emulator:
            <wdc_exec_command(0xd005e514,0xd60cdd30,0,8,..)>
              <ata_get_xfer(0,0xd60cdd30,0,8,..)>
                <0x26c550(&ata_xfer_pool,2,0,8,..)>
                <0x35c71c(0x3f27000,0,52,8,..)>
              <ata_exec_xfer(0xd005e4c8,0x3f27000,0,13,..)>
                <atastart(0xd005e4c8,0x3f27000,0,13,..)>
                  <__wdccommand_start(0xd005e4c8,0x3f27000,0,13,..)>
                    <bsw1(&prep_isa_io_space_tag,0x800001f6,0,176,..)>
                [ wdc: write to SDH: 0xb0 (sectorsize 2, lba=1, drive 1, head 0) ]
                    <wdcwait(0xd005e4c8,72,64,0xbb8,..)>
                      <0x198120(0xd005e4c8,72,64,0xbb8,..)>
                        <bsr1(&prep_isa_io_space_tag,0,0,0xbb8,..)>
                        <delay(100,0,0,0xbb8,..)>
            Note: <bsr1(&prep_isa_io_space_tag,0,0,0xbb8,..)>
        x)  PPC optimizations; instr combs
        x)  64-bit stuff: either Linux on G5, or perhaps some hobbyist
                version of AIX? (if there exists such a thing)
        x)  macppc: adb controller; keyboard (for framebuffer mode)
        x)  make OpenBSD/macppc work (PCI controller stuff)
        x)  Floating point exception correctness.
        x)  Alignment exceptions.

PReP:
        Clock time! ("Bad battery blah blah")

Algor:
        o)  Other models than the P5064?
        o)  PCI interrupts... needed for stuff like the tlp NIC?

BeBox:
        o)  Interrupts. There seems to be a problem with WDC interrupts
            "after a short while", although a few interrupts get through?
        o)  Perhaps find a copy of BeOS and try it?

HPCmips:
        x)  Mouse/pad support! :)
        x)  A NIC? (As a PCMCIA device?)

AVR:
        o)  Everything.

ARM:
        o)  See netwinder_reset() in NetBSD; the current "an internal error
            occured" message after reboot/halt is too ugly.
        o)  ARM "wait"-like instruction?
        o)  try to get netbsd/evbarm 3.x or 4.x running (iq80321)
        o)  make the xscale counter registers (ccnt) work
        o)  make the ata controller usable for FreeBSD!
        o)  Zaurus emulation, for e.g. OpenBSD/zaurus
        o)  Debian/cats crashes because of unimplemented coproc stuff.
            fix this?

Test machines:
        o)  dev_fb block fill and copy
        o)  dev_fb draw characters (from the built-in font)?
        o)  dev_fb input device? mouse pointer coordinates and buttons
                (allow changes in these to cause interrupts as well?)
        o)  Redefine the halt() function so that it stops "sometimes
            soon", i.e. usage in demo code should be:
                for (;;) {
                        halt();
                }

Better CD Image file support:
        x)  Support CD formats that contain more than 1 track, e.g.
            CDI files (?). These can then contain a mixture of e.g. sound
            and data tracks, and booting from an ISO filesystem path
            would boot from [by default] the first data track.
            (This would make sense for e.g. Dreamcast CD images, or
            possibly other live-CD formats.)

Networking:
        x)  Fix performance problems caused by only allowing a
            single TCP packet to be unacked.
        x)  Don't hardcode offsets into packets!
        x)  Test with lower than 100 max tcp/udp connections,
            to make sure that reuse works!
        x)  Make OpenBSD work better as a guest OS!
        x)  DHCP? Debian doesn't actually send DHCP packets, even
                though it claims to? So it is hard to test.
        x)  Multiple networks per emulation, and let different
            NICs in machines connect to different networks.
        x)  Support VDE (vde.sf.net)? Easiest/cleanest (before a
            redesign of the network framework has been done) is
            probably to connect it using the current (udp) solution.
        x)  Allow SLIP connections, possibly PPP, in addition to
            ethernet?

Cache simulation:
        o)  Command line flags for:
                o)  CPU endianness?
                o)  Cache sizes? (multiple levels)
        o)  Separate from the CPU concept, so that multi-core CPUs sharing
            e.g. a L2 cache can be simulated (?)
        o)  Instruction cache emulation is easiest (if separate from the
            data cache); similar hack as the S;I; hack in cpu_dyntrans.c.
            NOTE: if the architecture has a delay slot, then an instruction
            slot can actually be executed as 2 instructions.
        o)  Data cache emulation = harder; each arch's load/store routines
            must include support? running one instruction at a time and
            having a cpu-dependant lookup function for each instruction
            is another option (easier to implement, but very very slow).

Documentation:
        x)  Note about sandboxing/security:
                Not all emulated instructions fail in the way they would
                do on real hardware (e.g. a userspace program writing to
                a system register might work in GXemul, but it would
                fail on real hardware).  Sandbox = contain from the
                host OS. But the emulated programs will run "less
                securely".
        x)  Try NetBSD/arc 4.x! (It seems to work with disk images!)
        x)  NetBSD/pmax 4 install instructions: xterm instead of vt100!
        x)  BETTER DEVICE EXAMPLES!
                o)  Move away from technical.html to somewhere new.
                o)  DEVICE_TICK
                o)  Implement example devices using interrupts, dyntrans
                    memory access, etc.?
        x)  Document the dyntrans core?
        x)  Rewrite the section about experimental devices, after the
            framebuffer acceleration has been implemented, and demos
            written. (Symbolic names instead of numbers; example
            use cases, etc. Mention demo files that use the various
            features?)
        x)  "a very simple linear framebuffer device (for graphics output)"
            under "which machines does gxemul emulate" ==> better
            description?
        x)  Better description on how to set up a cross compiler?
            Example for MIPS64.
        o)  Automagic documentation generation?
                x)  machines, cpus, devices.
                x)  REMEMBER that several machines/devices can be in
                        the same source file!
        o)  Try to rewrite the install instructions for those machines
            that use 3MAX into using CATS or hpcmips? (To remove the need
            to use a raw ffs partition, using up all of the disk image.)

More generic out_of_memory error reporting, and check everywhere!
        Causes: OpenBSD has low default limits for normal users.
                Host is 32-bit? (32-bit hosts are limited to 4 GB or less
                of userspace memory.)
                You are actually low on RAM. (As trivial as this might sound,
                Unix systems usually allow processes to allocate virtual
                memory beyond the amount of RAM in the machine.)

The Device subsystem:
        x)  allow devices to be moved and/or changed in size (down to a
            minimum size, etc, or up to a max size); if there is a collision,
            return false. It is up to the caller to handle this situation!
        x)  NOTE: Translations must be invalidated, both for
            registering new devices, and for moving existing ones.
            cpu->invalidate translation caches, for all CPUs that
            are connected to a specific memory.
        x)  keep track of interrupts and busses? actually, allowing any device
            to be a bus might be a nice idea.
        x)  turn interrupt controllers into devices? :-)
        x)  refactor various clocks/nvram/cmos into one device?

PCI:
        x)  last write was ffffffff ==> fix this, it should be used
            together with a mask to get the correct bits. also, not ALL
            bits are size bits! (lowest 4 vs lowest 2?)
        x)  add support for address fixups
        x)  generalize the interrupt routing stuff (lines etc)

Clocks and timers:
        x)  DON'T HARDCODE 100 HZ IN cpu_mips_coproc.c!
        x)  Test the 8253? Right now it doesn't seem to be used?
        x)  NetWinder timeofday is incorrect!
        x)  Cobalt TOD is incorrect!
        x)  Go through all other machines, one by one, and fix them.

Config file parser:
        o)  Rewrite it from scratch!
        o)  Usage of any expression available through the debugger
        o)  Allow interrupt controllers to be added! and interrupts
            to be used in more ways than before
        o)  Support for running debugger commands (like the -c
            command line option)

Floating point layer:
        o)  make it common enough to be used by _all_ emulation modes
        o)  implement correct error/exception handling and rounding modes
        o)  implement more helper functions (i.e. add, sub, mul...)
        o)  non-IEEE modes (i.e. x86)?

Userland emulation:
        x)  Lots of stuff; freebsd and netbsd (and linux?) syscalls.
        x)  Dynamic linking? Hm.

Sound:
        x)  generic sound framework
        x)  add one or more sound cards as devices; add a testmachine
            sound card first?
        x)  Dreamcast sound? Generic PCI sound cards?

ASC SCSI controller:
        x)  NetBSD/arc 2.0 uses the ASC controller in a way which GXemul
            cannot yet handle. (NetBSD 1.6.2 works ok.) (Possibly a problem
            in NetBSD itself, http://mail-index.netbsd.org/source-changes/
            2005/11/06/0024.html suggests that.)
            NetBSD 4.x seems to work? :)

Caches / memory hierarchies: (this is mostly MIPS-specific)
        o)  src/memory*.c: Implement correct cache emulation for
            all CPU types. (currently only R2000/R3000 is implemented)
            (per CPU, multiple levels should be possible, associativity etc!)
        o)  R2000/R3000 isn't _100%_ correct, just almost correct :)
        o)  Move the -S (fill mem with random) functionality into the
            memory.c subsystem, not machine.c or wherever it is now
        o)  ECC stuff, simulation of memory errors?  (Machine dependent)
        o)  More than 4GB of emulated RAM, when run on a 32-bit host?
            (using manual swap-out of blocks to disk, ugly)
        o)  A global command line option should be used to turn
            cache emulation on or off. When off, caches should be
            faked like they are right now. When on, caches and
            memory latencies should be emulated as correctly as
            possible.

File/disk/symbol handling:
        o)  Make sure that disks can be added/removed during runtime!
            (Perhaps this needs a reasonably large re-write.)
        o)  Remove some of the complexity in file format guessing, for
                Ultrix kernels that are actually disk images?
        o)  Better handling of tape files       
        o)  Read function argument count and types from binaries? (ELF?)
        o)  Better demangling of C++ names. Note: GNU's C++ differs from e.g.
            Microsoft's C++, so multiple schemes must be possible. See
            URL at top of src/symbol_demangle.c for more info.

Userland ABI emulation:
        o)  see src/useremul.c

Better framebuffer and X-windows functionality:
        o)  Generalize the update_x1y1x2y2 stuff to an extend-region()
            function...
        o)  -Yx sometimes causes crashes.
        o)  Simple device access to framebuffer_blockcopyfill() etc,
            and text output (using the built-in fonts), for dev_fb.
        o)  CLEAN UP the ugly event code
        o)  Mouse clicks can be "missed" in the current system; this is
            not good. They should be put on a stack of some kind.
        o)  More 2D and 3D framebuffer acceleration.
        o)  Non-resizable windows?  Or choose scaledown depending
                on size (and center the image, with a black border).
        o)  Different scaledown on different windows?
        o)  Non-integral scale-up? (E.g. 640x480 -> 1024x768)
        o)  Switch scaledown during runtime? (Ala CTRL-ALT-plus/minus)
        o)  Bug reported by Elijah Rutschman on MacOS with weird
            keys (F5 = cursor down?).
        o)  Keyboard and mouse events:
                x)  Do this for more machines than just DECstation
                x)  more X11 cursor keycodes
                x)  Keys like CTRL, ALT, SHIFT do not get through
                    by themselves (these are necessary for example
                    to change the font of an xterm in X in the
                    emulator)
        o)  Generalize the framebuffer stuff by moving _ALL_ X11
                specific code to src/x11.c!
