emul/8086: add PC/AT emulator

This commit is contained in:
Virgil Dupras 2020-10-25 10:27:52 -04:00
parent c912158744
commit ba21b6a9f5
10 changed files with 175 additions and 16 deletions

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@ -1,2 +1,3 @@
/forth
/forth.bin
/pcat

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@ -1,4 +1,4 @@
TARGETS = forth
TARGETS = forth pcat
OBJS = cpu.o
CDIR = ../../cvm
STAGE = $(CDIR)/stage
@ -13,6 +13,9 @@ forth: forth.c forth.bin $(OBJS) $(BLKFS)
forth.bin: xcomp.fs $(STAGE)
$(CDIR)/stage < xcomp.fs > $@
pcat: pcat.c $(OBJS) $(BLKFS)
$(CC) -DBLKFS_PATH=\"`pwd`/$(BLKFS)\" pcat.c $(OBJS) -lncurses -o $@
$(BLKFS): $(STAGE)
$(STAGE):

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@ -1,8 +1,28 @@
# 8086 emulator
This is a work in progress. The goal is to have something lighter than QEMU to
run Collapse OS on and also something that is easier to plug with my stuff.
Something I could run without BIOS (have my own studs for INT 10 and INT 13).
This folder contains emulator for 8086 binaries of Collapse OS. The bulk of
it is a fork of Fake86 by Mike Chambers.
My first try was with 8086tiny, but this code is messy. Fake86 is a bit bigger,
but also cleaner.
`forth` is an imaginary hardware used for userspace development and testing.
This machine has an imaginary interrupt API and does not conform to PC/AT.
`pcat` is a very simple PC/AT emulator. The BIOS interrupt hooks implemented in
it only cover Collapse OS' own needs.
## Requirements
You need `ncurses` to build the `forth` executable. In debian-based distros,
it's `libncurses5-dev`.
## Build
Run `make` and it builds the `forth` and `pcat` interpreters.
## Usage
The `./forth` executable here works like the one in `/cvm`, except that it runs
under an emulated 8086 machine instead of running natively. Refer to
`/cvm/README.md` for details.
`pcat` needs to be suppied a path to a floppy disk image with a proper MBR.
`disk.bin` provided by the `pcat` recipe is sufficient.

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@ -3399,8 +3399,8 @@ int exec86(int execloops) {
return 1;
}
void reset86() {
void reset86(uint16_t startip) {
segregs[regcs] = 0;
ip = 0;
ip = startip;
hltstate = 0;
}

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@ -52,4 +52,4 @@ void writew86 (uint32_t addr32, uint16_t value);
uint8_t read86 (uint32_t addr32);
uint16_t readw86 (uint32_t addr32);
int exec86(int execloops); // returns 0 if halted
void reset86();
void reset86(uint16_t startip);

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@ -93,7 +93,7 @@ int main(int argc, char *argv[])
INTHOOKS[4] = int4;
INTHOOKS[5] = int5;
INTHOOKS[6] = int6;
reset86();
reset86(0);
fprintf(stderr, "Using blkfs %s\n", BLKFS_PATH);
blkfp = fopen(BLKFS_PATH, "r+");
if (!blkfp) {

127
emul/8086/pcat.c Normal file
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@ -0,0 +1,127 @@
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
#include <curses.h>
#include "cpu.h"
#define WCOLS 80
#define WLINES 25
#define SEC_PER_TRK 0x3f
#define TRK_PER_HEAD 0xff
extern uint8_t byteregtable[8];
extern union _bytewordregs_ regs;
extern uint16_t segregs[4];
extern INTHOOK INTHOOKS[0x100];
static FILE *fp;
WINDOW *bw, *dw, *w;
static void int10() {
uint8_t cmd = regs.byteregs[regah];
uint8_t al = regs.byteregs[regal];
uint16_t dx = regs.wordregs[regdx];
switch (cmd) {
case 0x02: // at-xy
wmove(w, dx&0xff, dx>>8);
break;
case 0x0e: // emit
if (al >= 0x20 || al == '\n') {
wechochar(w, al);
} else if (al == 0x08) {
int y, x; getyx(w, y, x);
wmove(w, y, x-1);
}
break;
}
}
static void int13() {
uint8_t cmd = regs.byteregs[regah];
uint8_t al = regs.byteregs[regal];
uint8_t cl = regs.byteregs[regcl];
uint8_t ch = regs.byteregs[regch];
uint8_t dh = regs.byteregs[regdh];
uint16_t bx = regs.wordregs[regbx];
switch (cmd) {
case 0x02: // read disk sector(s)
case 0x03: // write disk sector(s)
// CL = sector number (1-based), AL = sector count
// DH = head number, CH = track number
// ES:BX = dest addr
fseek(fp, ((((dh*TRK_PER_HEAD)+ch)*SEC_PER_TRK)+cl-1)*512, SEEK_SET);
for (int i=0; i<(al*512); i++) {
if (cmd == 0x03) { // write
fputc(getmem8(segregs[reges], bx+i), fp);
} else { // read
putmem8(segregs[reges], bx+i, fgetc(fp));
}
}
break;
case 0x08: // poll sectors per track / per head
// we just report a lot of them
regs.wordregs[regcx] = SEC_PER_TRK;
regs.byteregs[regdh] = TRK_PER_HEAD-1;
break;
}
}
static void int16() {
int c;
// debug_panel();
c = wgetch(w);
regs.byteregs[regal] = c;
}
static void usage()
{
fprintf(stderr, "Usage: ./pcat /path/to/fd\n");
}
int main(int argc, char *argv[])
{
if (argc < 2) {
usage();
return 1;
}
INTHOOKS[0x10] = int10;
INTHOOKS[0x13] = int13;
INTHOOKS[0x16] = int16;
reset86(0x7c00);
// initialize memory
fp = fopen(argv[1], "r");
if (!fp) {
fprintf(stderr, "Can't open %s\n", argv[1]);
return 1;
}
// read MBR into RAM
for (int i=0; i<512; i++) {
int c = getc(fp);
if (c != EOF) {
write86(0x7c00+i, c);
}
}
uint16_t magic = readw86(0x7dfe);
if (magic != 0xaa55) {
fprintf(stderr, "Invalid MBR magic %x\n", magic);
return 1;
}
initscr(); cbreak(); noecho(); nl(); clear();
// border window
bw = newwin(WLINES+2, WCOLS+2, 0, 0);
wborder(bw, 0, 0, 0, 0, 0, 0, 0, 0);
wrefresh(bw);
// debug panel
dw = newwin(1, 30, LINES-1, COLS-30);
w = newwin(WLINES, WCOLS, 1, 1);
scrollok(w, 1);
while (exec86(100)) {
//debug_panel();
}
nocbreak(); echo(); delwin(w); delwin(bw); delwin(dw); endwin();
printf("\nDone!\n");
//emul_printdebug();
fclose(fp);
return 0;
}

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@ -3,6 +3,7 @@ BASE = ../..
CDIR = $(BASE)/cvm
BLKPACK = $(BASE)/tools/blkpack
STAGE = $(CDIR)/stage
EMUL = $(BASE)/emul/8086/pcat
.PHONY: all
all: $(TARGET)
@ -10,7 +11,7 @@ os.bin: xcomp.fs $(STAGE) blkfs
$(STAGE) blkfs < xcomp.fs > $@
$(BLKPACK):
$(MAKE) -C ../tools
$(MAKE) -C $(BASE)/tools
blkfs: $(BLKPACK)
$(BLKPACK) $(BASE)/blk blk > $@
@ -25,9 +26,12 @@ $(TARGET): mbr.bin os.bin
cat mbr.bin os.bin > $@
dd if=blkfs of=$@ bs=512 seek=16
$(EMUL):
$(MAKE) -C $(BASE)/emul/8086
.PHONY: emul
emul: $(TARGET)
qemu-system-i386 -drive file=$(TARGET),if=floppy,format=raw
emul: $(TARGET) $(EMUL)
$(EMUL) $(TARGET)
.PHONY: clean
clean:

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@ -12,7 +12,6 @@ is bootable on a modern PC-compatible machine.
* A modern PC-compatible machine that can boot from a USB drive.
* A USB drive
* qemu for emulation
## Build the binary
@ -30,7 +29,12 @@ can run `VE`.
## Emulation
You can run the built binary in qemu using `make emul`.
You can run the built binary in Collapse OS' 8086 emulator using `make emul`.
The 8086 emulator is barbone. If you prefer to use it on a more realistic
setting, use QEMU. The command is:
qemu-system-i386 -drive file=disk.bin,if=floppy,format=raw
## Running on a modern PC

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@ -2,7 +2,7 @@
( AH=read sectors, AL=1 sector, BX=dest,
CH=trackno CL=secno DH=head DL=drive )
FDSPT C@ /MOD ( AX BX sec trk )
FDHEADS C@ /MOD ( AX BX sec head trk )
FDHEADS C@ /MOD SWAP ( AX BX sec head trk )
8 LSHIFT ROT OR 1+ ( AX BX head CX )
SWAP 8 LSHIFT 0x03 C@ ( boot drive ) OR ( AX BX CX DX )
13H 2DROP 2DROP