Added A20 line support.

front/sdl/docopt.c

@@ -226,13 +226,15 @@ int elems_to_args(struct Elements *elements, struct DocoptArgs *args,
     for (i = 0; i < elements->n_options; i++) {
         option = &elements->options[i];
         if (help && option->value && strcmp(option->olong, "--help") == 0) {
-            for (j = 0; j < 19; j++)
+            for (j = 0; j < 20; j++)
                 puts(args->help_message[j]);
             return EXIT_FAILURE;
         } else if (version && option->value &&
                    strcmp(option->olong, "--version") == 0) {
             puts(version);
             return EXIT_FAILURE;
+        } else if (strcmp(option->olong, "--a20") == 0) {
+            args->a20 = option->value;
         } else if (strcmp(option->olong, "--clean") == 0) {
             args->clean = option->value;
         } else if (strcmp(option->olong, "--edit") == 0) {
@@ -299,8 +301,8 @@ int elems_to_args(struct Elements *elements, struct DocoptArgs *args,
 
 struct DocoptArgs docopt(int argc, char *argv[], const bool help, const char *version) {
     struct DocoptArgs args = {
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, NULL, NULL, (char *) "10.0", NULL, NULL,
-        NULL,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, NULL, NULL, (char *) "10.0", NULL,
+        NULL, NULL,
             usage_pattern,
             { "Usage: virtualxt [options]",
               "",
@@ -310,6 +312,7 @@ struct DocoptArgs docopt(int argc, char *argv[], const bool help, const char *ve
               "  --hdboot                Prefer booting from harddrive.",
               "  --halt                  Debug break on startup.",
               "  --mute                  Disable audio.",
+              "  --a20                   Enable support for A20 line.",
               "  --no-activity           Disable disk activity indicator.",
               "  --no-idle               Disable CPU idle on INT28.",
               "  --clean                 Remove config file and write a new default one.",
@@ -327,6 +330,7 @@ struct DocoptArgs docopt(int argc, char *argv[], const bool help, const char *ve
     struct Argument arguments[] = {NULL
     };
     struct Option options[] = {
+        {NULL, "--a20", 0, 0, NULL},
         {NULL, "--clean", 0, 0, NULL},
         {NULL, "--edit", 0, 0, NULL},
         {NULL, "--halt", 0, 0, NULL},
@@ -349,7 +353,7 @@ struct DocoptArgs docopt(int argc, char *argv[], const bool help, const char *ve
 
     elements.n_commands = 0;
     elements.n_arguments = 0;
-    elements.n_options = 16;
+    elements.n_options = 17;
     elements.commands = commands;
     elements.arguments = arguments;
     elements.options = options;

front/sdl/docopt.h

@@ -82,6 +82,7 @@ typedef size_t bool;
 struct DocoptArgs {
 
     /* options without arguments */
+    size_t a20;
     size_t clean;
     size_t edit;
     size_t halt;
@@ -101,7 +102,7 @@ struct DocoptArgs {
     char *trace;
     /* special */
     const char *usage_pattern;
-    const char *help_message[19];
+    const char *help_message[20];
 };
 
 struct DocoptArgs docopt(int, char *[], bool, const char *);

front/sdl/main.c

@@ -583,6 +583,8 @@ static int load_config(void *user, const char *section, const char *name, const
 			args.hdboot |= atoi(value);
 		else if (!strcmp("halt", name))
 			args.halt |= atoi(value);
+		else if (!strcmp("a20", name))
+			args.a20 |= atoi(value);
 		else if (!strcmp("mute", name))
 			args.mute |= atoi(value);
 		else if (!strcmp("no-activity", name))
@@ -745,6 +747,7 @@ static bool write_default_config(const char *path, bool clean) {
 		"\n[args]\n"
 		";halt=1\n"
 		";hdboot=1\n"
+		";a20=1\n"
 		";harddrive=boot/freedos_hd.img\n"
 		"\n[ch36x_isa]\n"
 		"port=0x201\n"
@@ -947,6 +950,11 @@ int main(int argc, char *argv[]) {
 		else
 			vxt_system_configure(vxt, "rifs", "readonly", "1");
 	#endif
+
+	#ifdef VXTU_MODULE_CHIPSET
+		if (args.a20)
+			vxt_system_configure(vxt, "args", "a20", "1");
+	#endif
 
 	#ifdef VXTU_MODULE_GDB
 		if (args.halt)

front/sdl/virtualxt.docopt

@@ -6,6 +6,7 @@ Options:
   --hdboot                Prefer booting from harddrive.
   --halt                  Debug break on startup.
   --mute                  Disable audio.
+  --a20                   Enable support for A20 line.
   --no-activity           Disable disk activity indicator.
   --no-idle               Disable CPU idle on INT28.
   --clean                 Remove config file and write a new default one.

lib/vxt/include/vxt/vxt.h

@@ -141,9 +141,9 @@ extern "C" {
     #define VXT_API
 #endif
 
-#define VXT_POINTER(s, o) ( (((((vxt_pointer)(vxt_word)(s)) << 4) + (vxt_pointer)(vxt_word)(o))) & 0xFFFFF )
-#define VXT_INVALID_POINTER ((vxt_pointer)0xFFFFFFFF)
-#define VXT_INVALID_TIMER_ID ((vxt_timer_id)-1)
+#define VXT_POINTER(s, o)    ( ((((vxt_pointer)(vxt_word)(s)) << 4) + (vxt_pointer)(vxt_word)(o)) & 0xFFFFFF )
+#define VXT_INVALID_POINTER  ( (vxt_pointer)0xFFFFFFFF )
+#define VXT_INVALID_TIMER_ID ( (vxt_timer_id)-1 )
 
 #define _VXT_ERROR_CODES(x)                                                     \
     x(0, VXT_NO_ERROR,                  "no error")                             \
@@ -335,6 +335,7 @@ VXT_API struct vxt_registers *vxt_system_registers(vxt_system *s);
 
 VXT_API int vxt_system_frequency(vxt_system *s);
 VXT_API void vxt_system_set_frequency(vxt_system *s, int freq);
+VXT_API void vxt_system_set_a20(vxt_system *s, bool enable);
 VXT_API void vxt_system_set_tracer(vxt_system *s, void (*tracer)(vxt_system*,vxt_pointer,vxt_byte));
 VXT_API void vxt_system_set_validator(vxt_system *s, const struct vxt_validator *intrf);
 VXT_API void vxt_system_set_userdata(vxt_system *s, void *data);

lib/vxt/system.c

@@ -205,6 +205,8 @@ VXT_API struct vxt_peripheral *vxt_allocate_peripheral(vxt_allocator *alloc, siz
 
 VXT_API void vxt_system_reset(CONSTP(vxt_system) s) {
     cpu_reset(&s->cpu);
+    s->a20 = false;
+
     for (int i = 0; i < s->num_devices; i++) {
         CONSTSP(vxt_peripheral) d = s->devices[i];
         if (d->reset)
@@ -312,6 +314,10 @@ VXT_API void vxt_system_set_frequency(CONSTP(vxt_system) s, int freq) {
     s->frequency = freq;
 }
 
+VXT_API void vxt_system_set_a20(CONSTP(vxt_system) s, bool enable) {
+	s->a20 = enable;
+}
+
 VXT_API void vxt_system_install_monitor(CONSTP(vxt_system) s, struct vxt_peripheral *dev, const char *name, void *reg, enum vxt_monitor_flag flags) {
 	if (s->num_monitors < VXT_MAX_MONITORS)
 		s->monitors[s->num_monitors++] = (struct vxt_monitor){ dev ? vxt_peripheral_name(dev) : "CPU", name, reg, flags };
@@ -357,25 +363,44 @@ VXT_API void vxt_system_install_io(CONSTP(vxt_system) s, struct vxt_peripheral *
 
 VXT_API void vxt_system_install_mem(CONSTP(vxt_system) s, struct vxt_peripheral *dev, vxt_pointer from, vxt_pointer to) {
 	VERIFY_PERIPHERAL(dev,);
+	if ((from | to) & ~0xFFFFF)
+		VXT_LOG("ERROR: Trying to register memory above 1MB!");
+
 	if ((from | (to + 1)) & 0xF)
 		VXT_LOG("ERROR: Trying to register unaligned address!");
 
-	from = (from >> 4) & 0xFFFF;
-	to = (to >> 4) & 0xFFFF;
+	from = from >> 4;
+	to = to >> 4;
 	while (from <= to)
 		s->mem_map[from++] = ((struct peripheral*)dev)->idx;
 }
 
 VXT_API vxt_byte vxt_system_read_byte(CONSTP(vxt_system) s, vxt_pointer addr) {
-    addr &= 0xFFFFF;
-    CONSTSP(vxt_peripheral) dev = s->devices[s->mem_map[addr >> 4]];
-    return dev->io.read(vxt_peripheral_device(dev), addr);
+	if (!s->a20)
+		addr &= 0xEFFFFF;
+
+	if (addr >= 0x100000) {
+		addr -= 0x100000;
+		return (addr >= UMA_SIZE) ? 0xFF : s->ext_mem[addr];
+	}
+
+	CONSTSP(vxt_peripheral) dev = s->devices[s->mem_map[addr >> 4]];
+	return dev->io.read(vxt_peripheral_device(dev), addr);
 }
 
 VXT_API void vxt_system_write_byte(CONSTP(vxt_system) s, vxt_pointer addr, vxt_byte data) {
-    addr &= 0xFFFFF;
-    CONSTSP(vxt_peripheral) dev = s->devices[s->mem_map[addr >> 4]];
-    dev->io.write(vxt_peripheral_device(dev), addr, data);
+	if (!s->a20)
+		addr &= 0xEFFFFF;
+
+	if (addr >= 0x100000) {
+		addr -= 0x100000;
+		if (addr < UMA_SIZE)
+			s->ext_mem[addr] = data;
+		return;
+	}
+
+	CONSTSP(vxt_peripheral) dev = s->devices[s->mem_map[addr >> 4]];
+	dev->io.write(vxt_peripheral_device(dev), addr, data);
 }
 
 vxt_byte system_in(CONSTP(vxt_system) s, vxt_word port) {

lib/vxt/system.h

@@ -29,6 +29,7 @@
 
 #define MAX_TIMERS 256
 #define INT64 long long
+#define UMA_SIZE (0x10000 - 16)
 #define PERIPHERAL_SIGNATURE 0xFAF129C3
 
 #define VERIFY_PERIPHERAL(p, r)										\
@@ -60,10 +61,12 @@ struct system {
 
    vxt_byte io_map[VXT_IO_MAP_SIZE];
    vxt_byte mem_map[VXT_MEM_MAP_SIZE];
+   vxt_byte ext_mem[UMA_SIZE];
 
    vxt_allocator *alloc;
    struct cpu cpu;
    int frequency;
+   bool a20;
 
    int num_timers;
    struct timer timers[MAX_TIMERS];

modules/chipset/a20.c

@@ -0,0 +1,80 @@
+// Copyright (c) 2019-2024 Andreas T Jonsson <mail@andreasjonsson.se>
+//
+// This software is provided 'as-is', without any express or implied
+// warranty. In no event will the authors be held liable for any damages
+// arising from the use of this software.
+//
+// Permission is granted to anyone to use this software for any purpose,
+// including commercial applications, and to alter it and redistribute it
+// freely, subject to the following restrictions:
+//
+// 1. The origin of this software must not be misrepresented; you must not
+//    claim that you wrote the original software. If you use this software in
+//    a product, an acknowledgment (see the following) in the product
+//    documentation is required.
+//
+//    This product make use of the VirtualXT software emulator.
+//    Visit https://virtualxt.org for more information.
+//
+// 2. Altered source versions must be plainly marked as such, and must not be
+//    misrepresented as being the original software.
+//
+// 3. This notice may not be removed or altered from any source distribution.
+
+#include <vxt/vxtu.h>
+
+struct a20 {
+	bool available;
+	vxt_byte port_92;
+};
+
+static vxt_byte in(struct a20 *c, vxt_word port) {
+	(void)port;
+	return c->port_92;
+}
+
+static void out(struct a20 *c, vxt_word port, vxt_byte data) {
+	(void)port;
+	bool enable_a20 = (data & 2) != 0;
+	if ((c->port_92 & 2) != (data & 2))
+		VXT_LOG(enable_a20 ? "Enable Fast-A20 line!" : "Disable Fast-A20 line!");
+
+	vxt_system_set_a20(VXT_GET_SYSTEM(c), enable_a20);
+	c->port_92 = data;
+}
+
+static vxt_error config(struct a20 *c, const char *section, const char *key, const char *value) {
+	if (!strcmp(section, "args") && !strcmp(key, "a20"))
+		c->available = atoi(value) != 0;
+	return VXT_NO_ERROR;
+}
+
+static vxt_error install(struct a20 *c, vxt_system *s) {
+	if (c->available)
+		vxt_system_install_io_at(s, VXT_GET_PERIPHERAL(c), 0x92);
+	return VXT_NO_ERROR;
+}
+
+static vxt_error reset(struct a20 *c) {
+	c->port_92 = 0;
+	return VXT_NO_ERROR;
+}
+
+static const char *name(struct a20 *c) {
+	(void)c; return "Fast-A20";
+}
+
+struct vxt_peripheral *a20_create(vxt_allocator *alloc, void *frontend, const char *args) {
+	(void)frontend; (void)args;
+
+	struct VXT_PERIPHERAL(struct a20) *p;
+	*(void**)&p = (void*)vxt_allocate_peripheral(alloc, sizeof(struct a20));
+
+	p->install = &install;
+	p->config = &config;
+	p->reset = &reset;
+	p->name = &name;
+	p->io.in = &in;
+	p->io.out = &out;
+	return (struct vxt_peripheral*)p;
+}

modules/chipset/chipset.c

@@ -32,6 +32,9 @@ struct vxt_peripheral *kbc_create(vxt_allocator *alloc);
 bool kbc_key_event(struct vxt_peripheral *p, enum vxtu_scancode key, bool force);
 vxt_int16 kbc_generate_sample(struct vxt_peripheral *p, int freq);
 
+// Fast-A20 switch
+struct vxt_peripheral *a20_create(vxt_allocator *alloc, void *frontend, const char *args);
+
 static struct vxt_peripheral *pic_create(vxt_allocator *alloc, void *frontend, const char *args) {
     (void)frontend; (void)args;
 	return vxtu_pic_create(alloc);
@@ -109,4 +112,4 @@ static struct vxt_peripheral *ppi_kbc_create(vxt_allocator *alloc, void *fronten
     return p;
 }
 
-VXTU_MODULE_ENTRIES(&pic_create, &dma_create, &pit_create, &ppi_kbc_create)
+VXTU_MODULE_ENTRIES(&pic_create, &dma_create, &pit_create, &ppi_kbc_create, &a20_create)

modules/chipset/premake5.lua

@@ -1,4 +1,5 @@
 files {
     "chipset.c",
-    "kbc.c"
+    "kbc.c",
+    "a20.c"
 }

modules/gdb/gdb.c

@@ -357,15 +357,11 @@ int gdb_sys_putchar(struct gdb_state *state, int ch) {
 }
 
 int gdb_sys_mem_readb(struct gdb_state *state, address addr, char *val) {
-	if (addr > 0xFFFFF)
-		return GDB_EOF;
     *val = (char)vxt_system_read_byte(state->sys, addr);
     return 0;
 }
 
 int gdb_sys_mem_writeb(struct gdb_state *state, address addr, char val) {
-	if (addr > 0xFFFFF)
-		return GDB_EOF;
     vxt_system_write_byte(state->sys, addr, (vxt_byte)val);
     return 0;
 }

tools/docopt/docopt_c.py

@@ -74,7 +74,7 @@
 
 #include <sys/limits.h>
 
-#elif defined(__FreeBSD__) || defined(__NetBSD__) \
+#elif defined(__NetBSD__) \
 || defined(__OpenBSD__) || defined(__bsdi__) \
 || defined(__DragonFly__) || defined(macintosh) \
 || defined(__APPLE__) || defined(__APPLE_CC__)