Last fixes tonight

Makefile

@@ -14,7 +14,6 @@ binaries:		## Build all small binaries
 	docker build --build-arg TARGET=readfloppy.bin -o . --target=export .
 	docker build --build-arg TARGET=writefloppy.bin -o . --target=export .
 	docker build --build-arg TARGET=crc16.bin -o . --target=export .
-	docker build --build-arg TARGET=wozmon.bin -o . --target=export .
 	docker build --build-arg TARGET=hello.bin -o . --target=export .
 	docker build --build-arg TARGET=copy.bin -o . --target=export .
 	docker build --build-arg TARGET=call.bin -o . --target=export .
@@ -22,6 +21,15 @@ binaries:		## Build all small binaries
 	docker build --build-arg TARGET=readio.bin -o . --target=export .
 	docker build --build-arg TARGET=writeio.bin -o . --target=export .
 
+.PHONY: polos
+polos:			## Build polOS components
+	docker build --build-arg TARGET=fat12boot.bin -o . --target=export .
+	docker build --build-arg TARGET=polio.com -o . --target=export .
+	docker build --build-arg TARGET=polmon.com -o . --target=export .
+	docker build --build-arg TARGET=mushroom.com -o . --target=export .
+	docker build --build-arg TARGET=hello.com -o . --target=export .
+	docker build --build-arg TARGET=ftpget.com -o . --target=export .
+
 .PHONY: floppy
 floppy:			## Make a bootable floppy image
 	docker build --build-arg TARGET=polos.img -o . --target=export .

arduino/kbd/kbd.ino

@@ -2,6 +2,10 @@
 #include "paracomm.h"
 #include "parallel.h"
 
+#ifndef NOKBD
+#define NOKBD 1
+#endif  // NOKBD
+
 ParaComms pc;
 
 void setup() {
@@ -37,7 +41,10 @@ void loop() {
     }
     led_counter += 1;
 
-    // checkKbdReset();
+#if NOKBD
+#else  // NOKBD
+    checkKbdReset();
+#endif  // NOKBD
 
     uint8_t mosib;
     if (strobeOccurred(mosib)) {
@@ -48,9 +55,9 @@ void loop() {
 
     if (Serial.available() > 0) {
         int c = Serial.read();
-#if 1
+#if NOKBD
         pc.SendByte(c);
-#else
+#else  // NOKBD
         if (c == 2) {
             mode = 0;
         } else if (c == 3) {
@@ -62,6 +69,6 @@ void loop() {
                 pc.SendByte(c);
             }
         }
-#endif
+#endif  // NOKBD
     }
 }

mrbridge.py

@@ -23,7 +23,7 @@ def device_thread(device, ws):
 def slowwrite(device, data):
     for b in data:
         device.write([b])
-        time.sleep(0.01)
+        time.sleep(0.005)
 
 
 def ws_thread(device, ws):

src/Makefile

@@ -20,8 +20,7 @@ LDFLAGS = -mregparmcall -Wl,--gc-sections -Os -nostdlib -flto
 %.com: %.elf
 	ia16-elf-objcopy -O binary $< $@
 
-bootsectors = fat12boot.bin wozmon.bin
+fat12boot.bin:
-$(bootsectors):
 	ia16-elf-objcopy -O binary $< $@
 
 fat12boot.elf: fat12boot.o fat12.o bootsect.S
@@ -37,33 +36,22 @@ polmon.elf: polmon.o stdlib.o
 polio.elf: LDFLAGS += -T flat0600.ld
 polio.elf: polio-main.o polio.s fat12.o paracomm.o stdlib.o
 
-wozmon.o: polmon.cc
-wozmon.o: CPPFLAGS = -DWOZMON=1
-wozmon.o:
-	$(CXX) $(CXXFLAGS) $(CPPFLAGS) -c -o $@ $<
-
-wozmon.elf: wozmon.o bootsect.S
-wozmon.elf: LDFLAGS += -T bootsect.ld
-wozmon.elf: CPPFLAGS += -DNOBPB
-
-wozmon.bin: wozmon.elf
-
 paracli.elf: LDFLAGS += -T doscom.ld
 paracli.elf: paracli.s paracomm.o
 
-dos-programs = mushroom.elf hello.elf
+dos-programs = mushroom.com hello.com ftpget.com
-$(dos-programs): LDFLAGS += -T doscom.ld
+$(dos-programs:.com=.elf): LDFLAGS += -T doscom.ld
 
 mushroom.elf: mushroom.s
 hello.elf: hello.o stdlib.o crt0.s
+ftpget.elf: ftpget.o stdlib.o crt0.s
 
-polos.img: fat12boot.bin polmon.com polio.com mushroom.com hello.com
+polos.img: fat12boot.bin polmon.com polio.com $(dos-programs)
 	dd if=/dev/zero of=$@ bs=512 count=720
 	mformat -i $@ -t 40 -h 2 -s 9
 	mcopy -i $@ polio.com ::/
 	mcopy -i $@ polmon.com ::/
-	mcopy -i $@ mushroom.com ::/
+	mcopy -i $@ $(dos-programs) ::/
-	mcopy -i $@ hello.com ::/
 	dd if=fat12boot.bin of=$@ conv=notrunc
 
 .PHONY: clean

src/ftpget.c

@@ -0,0 +1,33 @@
+#include <stdint.h>
+#include <unistd.h>
+
+#include "polos.h"
+
+#define kDefaultChunkSize 0x20
+
+int main(int argc, uint16_t argv[]) {
+    if (argc < 2) {
+        return -1;
+    }
+
+    uint8_t* dest = (uint8_t*)argv[0];
+    uint16_t size = argv[1];
+    uint8_t chunksize = kDefaultChunkSize;
+    if (argc > 2) {
+        chunksize = argv[2];
+    }
+
+    uint8_t ok = 0x42;
+
+    for (int i = 0; i < size; ) {
+        runcomms(kUntilIdle);
+        // delay?
+
+        int len = read(kLpt1, dest + i, chunksize);
+        if (len <= 0) {
+            break;
+        }
+        write(kLpt1, &ok, 1);
+        i += len;
+    }
+}

src/hello.c

@@ -1,5 +1,12 @@
 #include <stdio.h>
 
-int main() {
+int main(int argc, int argv[]) {
     puts("Hello, world!\r\n");
+
+    if (argc > 1) {
+        return argv[0] + argv[1];
+    } else if (argc > 0) {
+        return argv[0];
+    }
+    return 0x42;
 }

src/paracomm.c

@@ -22,6 +22,7 @@ static uint8_t miso_recvbuf[256];
 static uint8_t miso_size;
 static uint8_t miso_received_nibbles;
 static uint8_t miso_state;
+recv_cb miso_recv_cb;
 
 static void swapbuffers() {
     mosi_sendbuf = mosi_workbuf[mosi_workbuf_idx];
@@ -92,19 +93,21 @@ void paracomm_feed(uint8_t n) {
         miso_received_nibbles += 1;
 
         if (miso_received_nibbles == 2 * miso_size) {
+            miso_recv_cb(miso_recvbuf, miso_size);
             miso_state = 0;
         }
     } break;
     }
 }
 
-void paracomm_init() {
+void paracomm_init(recv_cb miso_cb) {
     mosi_size = 0;
     mosi_workbuf_idx = 0;
     mosi_workbuf_size = 0;
     mosi_state = 0;
 
     miso_state = 0;
+    miso_recv_cb = miso_cb;
 }
 
 int paracomm_send(uint8_t b) {
@@ -119,20 +122,4 @@ int paracomm_send(uint8_t b) {
     return 0;
 }
 
-uint8_t paracomm_recv(uint8_t* buf, uint8_t size) {
+uint8_t paracomm_busy() { return mosi_state != 0 || miso_state != 0; }
-    if (miso_state != 0) {
-        return 0;
-    }
-    if (size > miso_size) {
-        size = miso_size;
-    }
-    memcpy(buf, miso_recvbuf, size);
-    memcpy(miso_recvbuf, miso_recvbuf+size, miso_size - size);
-    miso_size -= size;
-
-    return size;
-}
-
-uint8_t paracomm_busy() {
-    return mosi_state != 0 || miso_state != 0;
-}

src/paracomm.h

@@ -2,19 +2,16 @@
 
 #include <stdint.h>
 
+typedef void (*recv_cb)(const uint8_t* buf, uint8_t size);
+
 /** Must call first **/
-void paracomm_init();
+void paracomm_init(recv_cb cb);
 
 /** Sends a single byte.
  * Returns: 0 if no error, non-0 otherwise.
  */
 int paracomm_send(uint8_t b);
 
-/** Receive some bytes.
- * Returns: number of bytes copied
- */
-uint8_t paracomm_recv(uint8_t* buf, uint8_t size);
-
 /** Call after reading a nibble from the port */
 void paracomm_feed(uint8_t n);
 

src/polio-main.c

@@ -12,7 +12,7 @@
 #define kParallelDataPort 0x3bc
 #define kParallelStatusPort 0x3bd
 #define kParallelControlPort 0x3be
-#define kParaDelay 400
+#define kParaDelay 100
 #define kRecvBufferSize 256
 
 void dosdbt();
@@ -51,15 +51,16 @@ static void __delay__(int n) {
     }
 }
 
-uint8_t xferpara() {
+uint8_t xferpara(uint8_t until_idle) {
-    uint8_t mosib = paracomm_nextbyte();
+    do {
-    __outb__(kParallelDataPort, mosib);
+        uint8_t mosib = paracomm_nextbyte();
-    __outb__(kParallelControlPort, 1);
+        __outb__(kParallelDataPort, mosib);
-    __delay__(kParaDelay);
+        __outb__(kParallelControlPort, 1);
-    __outb__(kParallelControlPort, 0);
+        __delay__(kParaDelay);
-    __delay__(kParaDelay);
+        __outb__(kParallelControlPort, 0);
-    uint8_t mison = __inb__(kParallelStatusPort) >> 4;
+        uint8_t mison = __inb__(kParallelStatusPort) >> 4;
-    paracomm_feed(mison);
+        paracomm_feed(mison);
+    } while (until_idle && paracomm_busy());
 
     return paracomm_busy();
 }
@@ -74,6 +75,22 @@ uint8_t parasend(uint8_t* addr, uint8_t size) {
     return i;
 }
 
+uint8_t pararecv(uint8_t* buf, uint8_t size) {
+    if (parasize == 0) {
+        return 0;
+    }
+    if (size > parasize) {
+        size = parasize;
+    }
+    memcpy(buf, parabuf, size);
+    if (size < parasize) {
+        memcpy(parabuf, parabuf + size, parasize - size);
+    }
+    parasize -= size;
+
+    return size;
+}
+
 int main() {
     dosdbt();
     parasize = 0;

src/polio.s

@@ -6,7 +6,7 @@
     .global _start
 _start:
     cli
-    mov ax, 0x2000      # stack address
+    mov ax, 0x2000      # stack address, shared with polmon
     mov sp, ax          # ss should already be 0
     sti
     jmp main
@@ -143,7 +143,7 @@ recvpara:
     mov ax, [bp+0]
     add ax, si
     mov dx, [bp+2]
-    call paracomm_recv
+    call pararecv
     ret
 
     .section .text.int80h
@@ -157,14 +157,13 @@ int80h:
     xor cx, cx
     mov es, cx
     mov ds, cx
-    shl ah
+    xchg ah, cl
-    cmp ah, offset int80h_entries
+    shl cl
+    cmp cl, offset int80h_entries
     jge 0f
-    mov al, ah
+    mov si, cx
-    xor ah, ah
-    mov si, ax
     mov bp, sp
-    lea bp, [bp + 16]       # 10 for us, 6 for the interrupt
+    add bp, 16       # 10 for us, 6 for the interrupt
     call cs:[int80h_table+si]
     jmp 1f
 0:

src/polmon.cc

@@ -2,94 +2,24 @@
 #include <cstdio>
 #include <cstring>
 
-#ifndef WOZMON
-#define WOZMON 0
-#endif
-
-#if WOZMON
-#define BACKSPACE 0
-#define ASCIIDUMP 0
-#define CLEARSCREENCMD 0
-#define INT80H 0
-#define SHOWTITLE 0
-#define BOOTSTRAP 0
-#define LAUNCH 0
-#define CTRLBREAK 0
-#endif  // WOZMON
-
-#ifndef BACKSPACE
-#define BACKSPACE 1
-#endif
-
-#ifndef ASCIIDUMP
-#define ASCIIDUMP 1
-#endif
-
-#ifndef CLEARSCREENCMD
-#define CLEARSCREENCMD 1
-#endif
-
-#ifndef INT80H
-#define INT80H 1
-#endif
-
-#ifndef SHOWTITLE
-#define SHOWTITLE 1
-#endif
-
-#ifndef BOOTSTRAP
-#define BOOTSTRAP 1
-#endif
-
-#ifndef LAUNCH
-#define LAUNCH 1
-#endif
-
-#ifndef CTRLBREAK
-#define CTRLBREAK 1
-#endif
-
 namespace {
 
-#if WOZMON
-
-int getchar() {
-    register char c asm("al");
-    asm volatile("movb $0x00, %%ah\n\t"
-                 "int $0x16"
-                 : "=r"(c)::"ah", "cc");
-    return c;
-}
-
-void putchar(int c) {
-    asm volatile("push %%bp          \n\t"
-                 "mov %0, %%ax       \n\t"
-                 "movb $0x0e, %%ah   \n\t"
-                 "movb $0, %%bh      \n\t"
-                 "int $0x10          \n\t"
-                 "pop %%bp           \n\t" ::"r"(c)
-                 : "ax", "bh", "cc");
-}
-
-#endif  // WOZMON
-
 constexpr int kDumpSize = 16;
 
-// arguments on the stack in reverse order
+extern "C" uint16_t Int80h(uint16_t fun, uint16_t nargs, uint16_t args[]);
-extern "C" uint16_t Int80h(uint8_t fun, int nargs);
 asm(".section .text.Int80h  \n"
     "Int80h:                \n"
     "   push %si            \n"
     "   push %bp            \n"
-    "   mov %al, %ah        \n"
     "   mov %sp, %bp        \n"
-    "   lea 6(%bp), %si     \n"  // 4 for pushed stuff, 2 for return addr
+    "   mov %cx, %si        \n"
+    "   shl $1, %dx         \n"
+    "   add %dx, %si        \n"
     "0:                     \n"
-    "   test %dx, %dx       \n"
+    "   cmp %cx, %si        \n"
-    "   jz 1f               \n"
+    "   je 1f               \n"
-    "   push (%si)          \n"
+    "   push -2(%si)        \n"
-    "   dec %dx             \n"
+    "   sub $2, %si         \n"
-    "   add $2, %si         \n"
     "   jmp 0b              \n"
     "1:                     \n"
     "   int $0x80           \n"
@@ -111,21 +41,22 @@ uint8_t ReadHexNibble(uint8_t c) {
     return 10 + (c - 'a');
 }
 
-uint16_t ReadUintN(int n, const char* buf) {
+uint16_t ReadUintN(int n, const char*& buf) {
     uint16_t out = 0;
     for (int i = 0; i < n; i++) {
-        if (buf[i] == 0) {
+        if (*buf < '0') {
             break;
         }
         out <<= 4;
-        out += ReadHexNibble(buf[i]);
+        out += ReadHexNibble(*buf);
+        buf += 1;
     }
     return out;
 }
 
-uint8_t ReadUint8(const char* buf) { return ReadUintN(2, buf); }
+uint8_t ReadUint8(const char*& buf) { return ReadUintN(2, buf); }
 
-uint16_t ReadUint16(const char* buf) { return ReadUintN(4, buf); }
+uint16_t ReadUint16(const char*& buf) { return ReadUintN(4, buf); }
 
 void WriteHexNibble(uint8_t c) {
     if (c > 9) {
@@ -145,6 +76,11 @@ void WriteUint16(uint16_t a) {
     WriteUint8(a & 0xff);
 }
 
+void WriteUint16ln(uint16_t a) {
+    WriteUint16(a);
+    puts("\r\n");
+}
+
 uint8_t __get_far_u8__(uint16_t addr, uint16_t seg) {
     register uint16_t ad asm("si") = addr;
     register uint16_t sg asm("ds") = seg;
@@ -173,7 +109,6 @@ void Dump(uint16_t addr, uint16_t seg, int count) {
         uint8_t d = __get_far_u8__(addr + i, seg);
         WriteUint8(d);
     }
-#if ASCIIDUMP
     putchar(' ');
     putchar(' ');
     for (int i = 0; i < count; i++) {
@@ -184,7 +119,6 @@ void Dump(uint16_t addr, uint16_t seg, int count) {
             putchar('.');
         }
     }
-#endif
 }
 
 void DumpHex(uint16_t addr, uint16_t seg) {
@@ -197,8 +131,7 @@ void DumpHex(uint16_t addr, uint16_t seg) {
     putchar(']');
     putchar(':');
     Dump(addr, seg, kDumpSize);
-    putchar('\r');
+    puts("\r\n");
-    putchar('\n');
 }
 
 void ClearScreen() {
@@ -244,49 +177,71 @@ void tofatname(const char* name, char* fatname) {
     }
 }
 
-void LaunchFile(const char* name) {
+uint16_t __readfile__(const char* name, uint16_t addr) {
+    register uint16_t ret asm("ax");
+    asm volatile("push %2        \n\t"
+                 "push %1        \n\t"
+                 "mov $04, %%ah  \n\t"
+                 "int $0x80      \n\t"
+                 "pop %%cx       \n\t"
+                 "pop %%cx       \n\t"
+                 : "=r"(ret)
+                 : "r"(name), "r"(addr)
+                 : "bx", "cx", "dx", "memory", "cc");
+
+    return ret;
+}
+
+uint16_t LaunchFile(const char* name, uint8_t argc, uint16_t* argv) {
     constexpr uint16_t kSegment = 0x200;
     constexpr uint16_t kAddress = 0x100;
     constexpr uint16_t kHeaderAddress = (kSegment << 4);
     constexpr uint16_t kFlatAddress = (kSegment << 4) + kAddress;
-    constexpr uint8_t kTrampoline[] = { 0xe8, 0xfd, 0x00, 0xcb };
+    constexpr uint16_t kArgvAddress = 0x0004;
+    // trampoline:
+    //      call 0x100
+    //      retf
+    // XXX: if you change kAddress, the trampoline needs to be updated
+    constexpr uint8_t kTrampoline[] = {0xe8, 0xfd, 0x00, 0xcb};
 
     char fatname[11];
     tofatname(name, fatname);
 
+    uint16_t r = __readfile__(fatname, kFlatAddress);
+    if (r) {
+        return r;
+    }
+
     auto* ptr = reinterpret_cast<uint8_t*>(kHeaderAddress);
     memcpy(ptr, kTrampoline, sizeof(kTrampoline));
+    auto* argp = reinterpret_cast<uint16_t*>(kHeaderAddress + kArgvAddress);
+    memcpy(argp, argv, argc * 2);
 
-    asm volatile("mov %1, %%ax      \n\t"
+    register uint16_t ac asm("ax") = argc;
-                 "push %%ax         \n\t"
+    register uint16_t av asm("dx") = kArgvAddress;
-                 "mov %0, %%ax      \n\t"
+    asm volatile("mov %2, %%cx      \n\t"
-                 "push %%ax         \n\t"
+                 "mov %%cx, %%ds    \n\t"
-                 "mov $04, %%ah     \n\t"
+                 "mov %%cx, %%es    \n\t"
-                 "int $0x80         \n\t"
-                 "add $4, %%sp      \n\t"
-                 "mov %2, %%ax      \n\t"
-                 "mov %%ax, %%ds    \n\t"
-                 "mov %%ax, %%es    \n\t"
                  "cli               \n\t"
-                 "mov %%ax, %%ss    \n\t"
+                 "mov %%cx, %%ss    \n\t"
-                 "mov %3, %%ax      \n\t"
+                 "mov %3, %%cx      \n\t"
-                 "xchg %%ax, %%sp   \n\t"
+                 "xchg %%cx, %%sp   \n\t"
                  "sti               \n\t"
-                 "push %%ax         \n\t"
+                 "push %%cx         \n\t"
                  "lcall %2,$0       \n\t"
-                 "xor %%ax, %%ax    \n\t"
+                 "xor %%cx, %%cx    \n\t"
-                 "mov %%ax, %%ds    \n\t"
+                 "mov %%cx, %%ds    \n\t"
-                 "mov %%ax, %%es    \n\t"
+                 "mov %%cx, %%es    \n\t"
                  "cli               \n\t"
                  "pop %%sp          \n\t"
-                 "mov %%ax, %%ss    \n\t"
+                 "mov %%cx, %%ss    \n\t"
                  "sti"
-                 :: "rmi"(fatname),
+                 : "+r"(ac), "+r"(av)
-                 "rmi"(kFlatAddress), "i"(kSegment), "i"(kHeaderAddress)
+                 : "i"(kSegment), "i"(kAddress)
-                 : "ax", "bx", "cx", "dx", "memory");
+                 : "bx", "cx", "memory", "cc");
-}
 
-#if CTRLBREAK
+    return ac;
+}
 
 constexpr uint16_t kCtrlBreakVector = (0x1b * 4);
 
@@ -294,9 +249,9 @@ extern "C" void cbreak();
 asm("   .section .text.cbreak   \n"
     "cbreak:                \n"
     "   xor %ax, %ax        \n"
-    "   mov %ds, %ax        \n"
+    "   mov %ax, %ds        \n"
     "   cli                 \n"
-    "   mov %ss, %ax        \n"
+    "   mov %ax, %ds        \n"
     "   mov $0x2000, %sp    \n"
     "   sti                 \n"
     "   pushf               \n"
@@ -313,15 +268,13 @@ void InstallCtrlBreak() {
     vec[1] = 0;
 }
 
-#endif  // CTRLBREAK
-
 bool ParseCommand(const char* buf, uint16_t& cur_addr, uint16_t& cur_seg) {
     bool dump = true;
     for (const char* ptr = buf; *ptr;) {
         if (*ptr == 's') {
             cur_addr = 0;
-            cur_seg = ReadUint16(ptr + 1);
+            ptr += 1;
-            ptr += 5;
+            cur_seg = ReadUint16(ptr);
         } else if (*ptr == '$') {
             __basic__();
         } else if (*ptr == 'j') {
@@ -329,52 +282,47 @@ bool ParseCommand(const char* buf, uint16_t& cur_addr, uint16_t& cur_seg) {
             ptr++;
             auto jump = reinterpret_cast<uint16_t (*)()>(cur_addr);
             uint16_t ret = jump();
-            WriteUint16(ret);
+            WriteUint16ln(ret);
-            putchar('\r');
-            putchar('\n');
-#if INT80H
         } else if (*ptr == 'i') {
             dump = false;
-            int nargs = 0;
+            uint16_t args[8];  // ought to be enough for everybody
+            uint8_t nargs = 0;
             ptr++;
-            int fun = ReadUint8(ptr);
+            int fun = ReadUint8(ptr) << 8;
-            ptr += 2;
+            fun += ReadUint8(ptr);
-            for (; *ptr;) {
+            for (; *ptr && nargs < 8;) {
                 if (*ptr == ' ') {
                     ptr++;
                     continue;
                 }
-                uint16_t d = ReadUint16(ptr);
+                args[nargs++] = ReadUint16(ptr);
-                asm volatile("push %0" ::"r"(d));
-                nargs++;
-                ptr += 4;
             }
-            uint16_t ret = Int80h(fun, nargs);
+            uint16_t ret = Int80h(fun, nargs, args);
-            asm volatile("shl %0   \n\t"
+            WriteUint16ln(ret);
-                         "add %0, %%sp" ::"r"(nargs));
-            WriteUint16(ret);
-            putchar('\r');
-            putchar('\n');
-#endif  // INT80H
-#if CLEARSCREENCMD
         } else if (*ptr == 'l') {
             dump = false;
             ClearScreen();
             ptr++;
-#endif  // CLEARSCREENCMD
-#if LAUNCH
         } else if (*ptr == 'r') {
             dump = false;
+            uint16_t args[8];  // ought to be enough for everybody
+            uint8_t nargs = 0;
             ptr++;
             while (*ptr == ' ') {
                 ptr++;
             }
-            int l = 0;
+            const char* fname = ptr;
-            for (; ptr[l]; l++) {
+            for (; *ptr && *ptr != ' '; ptr++) {
             }
-            LaunchFile(ptr);
+            for (; *ptr && nargs < 8;) {
-            ptr += l;
+                if (*ptr == ' ') {
-#endif  // LAUNCH
+                    ptr++;
+                    continue;
+                }
+                args[nargs++] = ReadUint16(ptr);
+            }
+            uint16_t ret = LaunchFile(fname, nargs, args);
+            WriteUint16ln(ret);
         } else if (*ptr == 'w') {
             dump = false;
             uint16_t addr = cur_addr;
@@ -387,21 +335,17 @@ bool ParseCommand(const char* buf, uint16_t& cur_addr, uint16_t& cur_seg) {
                 uint8_t d = ReadUint8(ptr);
                 __set_far_u8__(addr, cur_seg, d);
                 addr++;
-                ptr += 2;
             }
         } else {
             cur_addr = ReadUint16(ptr);
-            ptr += 4;
         }
     }
     return dump;
 }
 
-void DisplayPrompt() {
+void DisplayPrompt() { puts("> "); }
-    putchar('>');
-    putchar(' ');
-}
 
+[[noreturn]]
 void polmon() {
     uint16_t cur_addr = 0;
     uint16_t cur_seg = 0;
@@ -410,9 +354,7 @@ void polmon() {
     char* inptr = inbuf;
 
     ClearScreen();
-#if SHOWTITLE
     puts("PolMon for Workgroups 3.1\r\n");
-#endif  // SHOWTITLE
     DisplayPrompt();
 
     while (1) {
@@ -434,7 +376,6 @@ void polmon() {
             first = false;
             inptr = inbuf;
             DisplayPrompt();
-#if BACKSPACE
         } else if (c == kBackspace || c == kOtherBackspace) {
             inptr--;
             if (inptr < inbuf) {
@@ -444,26 +385,19 @@ void polmon() {
             }
             putchar(' ');
             putchar(kOtherBackspace);
-#endif
         } else {
             *inptr = c;
             inptr++;
         }
     }
+    __builtin_unreachable();
 }
 
 }  // namespace
 
 int main() {
-#if CTRLBREAK
     InstallCtrlBreak();
-#endif  // CTRLBREAK
     polmon();
 }
 
-#if BOOTSTRAP
+__attribute__((section(".init"), used)) void _start() { main(); }
-__attribute__((section(".init"), noreturn, used)) void _start() {
-    main();
-    __builtin_unreachable();
-}
-#endif  // BOOTSTRAP

src/polos.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#define kLpt1 0x10
+#define kUntilIdle 1
+#define kOnce 0
+
+int runcomms(char until_idle);

src/stdlib.c

@@ -1,6 +1,8 @@
 #include <stdint.h>
 #include <stdlib.h>
 
+#include "polos.h"
+
 int getchar() {
     register char c asm("al");
     asm volatile("movb $0x00, %%ah\n\t"
@@ -43,3 +45,46 @@ void* memset(void* ptr, int val, size_t len) {
     }
     return ptr;
 }
+
+int _int80h_2(uint8_t fun, uint16_t arg1, uint16_t arg2) {
+    register uint16_t a1 asm("dx") = arg1;
+    register uint16_t a2 asm("cx") = arg2;
+    register uint8_t ah asm("ah") = fun;
+    register uint16_t ret asm("ax");
+    asm volatile("push %3            \n\t"
+                 "push %2            \n\t"
+                 "int $0x80          \n\t"
+                 "pop %%cx           \n\t"
+                 "pop %%cx           \n\t"
+                 : "=r"(ret)
+                 : "r"(ah), "r"(a1), "r"(a2)
+                 : "bx", "cc", "memory");
+
+    return ret;
+}
+
+int runcomms(char until_idle) {
+    register int ret asm("ax");
+    register char ui asm("al") = until_idle;
+    asm volatile("mov $0x07, %%ah    \n\t"
+                 "int $0x80          \n\t"
+                 : "=r"(ret)
+                 : "r"(until_idle)
+                 : "bx", "cx", "dx", "cc", "memory");
+
+    return ret;
+}
+
+int read(int fd, void* buf, size_t size) {
+    if (fd != kLpt1) {
+        return -1;
+    }
+    return _int80h_2(0x05, (uint16_t)buf, size);
+}
+
+int write(int fd, void* buf, size_t size) {
+    if (fd != kLpt1) {
+        return -1;
+    }
+    return _int80h_2(0x06, (uint16_t)buf, size);
+}