upstream/0.4.3/TODO

$Id: TODO,v 1.410 2006/11/06 05:32:38 debug Exp $

This file is my list of things I want to work on in the future. It is in
random order, and some parts of it 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,
            experiment in a separate project (not in GXemul)
                o) First test would be to just implement a simple
                   instruction such as MIPS' addiu or lui, on AMD64
                   hosts...

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)  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)  DMA (0xffa00000)
        x)  Instruction tracing should include symbols for branch targets,
            and so on...
        x)  SH4 interrupt controller:
                x)  Implement correct priorities of interrupts
        x)  SH4 BSC (Bus State Controller)
        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 exception correctness.
        x)  Floating point speed!
        x)  Think carefully about how to implement SH5/SH64 (for evbsh5).

Dreamcast:
        x)  CD image bootup:
                0)  Find IP.BIN, and load it to 0x8c008000.
                1)  Run code at 0x8c008300 (SEGA license code).
                2)  When the license code runs a "boot menu" syscall,
                    load the 1ST_READ.BIN file (unscrambled?) to 0x8c010000.
                3)  Run code at 0x8c00b800 (Bootstrap 1). This will in turn
                    jump to 0x8c00e000 (Bootstrap 2), and then jump to
                    0x8c010000, to start the program.
                (Try with e.g. Comstedt's Serial IP Slave, to make sure it
                works as expected.)
        x)  LAN adapter.
        x)  PVR:  Lots of stuff. See dev_pvr.c.
        x)  Maple bus:
                x)  Correct controller input
                x)  Mouse input
        x)  PROM/BIOS calls:
                x)  GD-ROM emulation
        x)  NetBSD/dreamcast: Root on nfs?
        x)  Linux/dreamcast? (The gentoo kernel currently crashes.)
        x)  More homebrew demos/games.
        x)  Sound emulation (ARM cpu).
        x)  VME processor emulation?

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!
        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)  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)  find and fix the bug which causes NetBSD/macppc to fail after
            an install!
        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.

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

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

AVR:
        o)  Everything.

AVR32:
        o)  Everything. It would be good if there was NetBSD/avr32 to
            experiment with...

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 running (iq80321)
        o)  make the xscale counter registers (ccnt) work
        o)  make the ata controller usable for FreeBSD!
        o)  zaurus for openbsd...
        o)  debian/cats crashes because of unimplemented coproc stuff.
            fix this?

Test machines:
        + dev_fb block fill and copy
        + dev_fb draw characters (from the built-in font)?
        + dev_fb input device? mouse pointer coordinates and buttons
                (allow changes in these to cause interrupts as well?)
        + 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)  DEVICE_TICK in technical.html
        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.

Busses:
        o)  Redesign the entire "mainbus" concept!
                x)  Busses should be placed in a hierarchical tree (?)
                x)  Specific clock/bus speeds, cpu speeds etc.
        o)  Interrupt routing subsystem:
                x)  IF POSSIBLE, try to make the new system work with the
                    current system, but print annoying warning messages. :)
                    Think carefully about this.
                x)  Registry for all available interrupts.
                        +)  Each interrupt controller (including CPU cores
                            that can handle interrupts) should register its
                            interrupts, e.g.
                                cpu[0].irq[3]
                                cpu[0].irq[3].pcmcia_slot[1]
                                cpu[0].irq.pci[3]
                        +)  Note: MIPS cpus have multiple irqs in the core,
                            while some other CPUs only have one (irq[0]
                            or just irq).
                x)  Users should use interrupt _names_ instead of integers
                    when attaching to an interrupt controller, but when
                    asserting/deasserting irq lines, small integers must
                    still be used (for obvious performance reasons).
                    Figure out a way to do this nicely!
                x)  Any users need to say whether they need the interrupt line
                    exclusively or allow shared access.
                x)  Must work with everything from native IRQs to
                    TurboChannel/PCI/ISA/ADB/PCMCIA/...
                x)  Must work with SMP emulation!
                x)  Make it with device_add(). How does the end user find
                    out the name of an interrupt controller/line in e.g.
                    a configuration file?
        o)  Synchronization over network? or at least in dyntrans within
            one emulated machine
        o)  Convert to real busses: TurboChannel, PCMCIA, ADB

Config file parser:
        o)  Rewrite it from scratch!
        o)  Usage of any expression available through the debugger
        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?

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)  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

Terminal/console:
        o)  allow emulated serial ports to be connected to the outside
            world in a more generic way, or even to other emulated
            machines(?)

Save state of the whole emulated machine, to be able to load it back
        in later?  (Memory, all device's states, all registers and
        so on.  Like taking a snapshot. (SimOS seems to do this,
        according to its website.))

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!
