3b1emu: src/main.c@a44afcf2354c (annotated)

file
revisions
annotate
diff
raw

src/main.c@a44afcf2354c (annotated)

src/main.c

Thu, 02 Dec 2010 17:01:34 +0000

author: Philip Pemberton <philpem@philpem.me.uk>
date: Thu, 02 Dec 2010 17:01:34 +0000
changeset 32: a44afcf2354c
parent 30: 3190629004b2
child 34: e8ebd433270a
permissions: -rw-r--r--

Implement memory mapping and access checking

 #include <stdio.h>
 #include <stdlib.h>
 #include <stdint.h>
 #include <stdbool.h>
 #include <malloc.h>
 #include <string.h>
 #include "SDL.h"
 #include "musashi/m68k.h"
 #include "version.h"
 #include "state.h"
 void FAIL(char *err)
 {
 	state_done();
 	fprintf(stderr, "ERROR: %s\nExiting...\n", err);
 	exit(EXIT_FAILURE);
 }
 /***********************************
  * Array read/write utility macros
  * "Don't Repeat Yourself" :)
  ***********************************/
 /// Array read, 32-bit
 #define RD32(array, address, andmask)							\
 	(((uint32_t)array[(address + 0) & (andmask)] << 24) |		\
 	 ((uint32_t)array[(address + 1) & (andmask)] << 16) |		\
 	 ((uint32_t)array[(address + 2) & (andmask)] << 8)  |		\
 	 ((uint32_t)array[(address + 3) & (andmask)]))
 /// Array read, 16-bit
 #define RD16(array, address, andmask)							\
 	(((uint32_t)array[(address + 0) & (andmask)] << 8)  |		\
 	 ((uint32_t)array[(address + 1) & (andmask)]))
 /// Array read, 8-bit
 #define RD8(array, address, andmask)							\
 	((uint32_t)array[(address + 0) & (andmask)])
 /// Array write, 32-bit
 #define WR32(array, address, andmask, value) {					\
 	array[(address + 0) & (andmask)] = (value >> 24) & 0xff;	\
 	array[(address + 1) & (andmask)] = (value >> 16) & 0xff;	\
 	array[(address + 2) & (andmask)] = (value >> 8)  & 0xff;	\
 	array[(address + 3) & (andmask)] =  value        & 0xff;	\
 }
 /// Array write, 16-bit
 #define WR16(array, address, andmask, value) {					\
 	array[(address + 0) & (andmask)] = (value >> 8)  & 0xff;	\
 	array[(address + 1) & (andmask)] =  value        & 0xff;	\
 }
 /// Array write, 8-bit
 #define WR8(array, address, andmask, value)						\
 	array[(address + 0) & (andmask)] =  value        & 0xff;
 /******************
  * Memory mapping
  ******************/
 #define MAPRAM(addr) (((uint16_t)state.map[addr*2] << 8) + ((uint16_t)state.map[(addr*2)+1]))
 uint32_t mapAddr(uint32_t addr, bool writing)
 {
 	if (addr < 0x400000) {
 		// RAM access. Check against the Map RAM
 		// Start by getting the original page address
 		uint16_t page = (addr >> 12) & 0x3FF;
 		// Look it up in the map RAM and get the physical page address
 		uint32_t new_page_addr = MAPRAM(page) & 0x3FF;
 		// Update the Page Status bits
 		uint8_t pagebits = (MAPRAM(page) >> 13) & 0x03;
 		if (pagebits != 0) {
 			if (writing)
 				state.map[page*2] |= 0x60;		// Page written to (dirty)
 			else
 				state.map[page*2] |= 0x40;		// Page accessed but not written
 		}
 		// Return the address with the new physical page spliced in
 		return (new_page_addr << 12) + (addr & 0xFFF);
 	} else {
 		// I/O, VRAM or MapRAM space; no mapping is performed or required
 		// TODO: assert here?
 		return addr;
 	}
 }
 typedef enum {
 	MEM_ALLOWED = 0,
 	MEM_PAGEFAULT,		// Page fault -- page not present
 	MEM_PAGE_NO_WE,		// Page not write enabled
 	MEM_KERNEL,			// User attempted to access kernel memory
 	MEM_UIE				// User Nonmemory Location Access
 } MEM_STATUS;
 // check memory access permissions
 MEM_STATUS checkMemoryAccess(uint32_t addr, bool writing)
 {
 	// Are we in Supervisor mode?
 	if (m68k_get_reg(NULL, M68K_REG_SR) & 0x2000)
 		// Yes. We can do anything we like.
 		return MEM_ALLOWED;
 	// If we're here, then we must be in User mode.
 	// Check that the user didn't access memory outside of the RAM area
 	if (addr >= 0x400000)
 		return MEM_UIE;
 	// This leaves us with Page Fault checking. Get the page bits for this page.
 	uint16_t page = (addr >> 12) & 0x3FF;
 	uint8_t pagebits = (MAPRAM(page) >> 13) & 0x07;
 	// Check page is present
 	if ((pagebits & 0x03) == 0)
 		return MEM_PAGEFAULT;
 	// User attempt to access the kernel
 	// A19, A20, A21, A22 low (kernel access): RAM addr before paging; not in Supervisor mode
 	if (((addr >> 19) & 0x0F) == 0)
 		return MEM_KERNEL;
 	// Check page is write enabled
 	if ((pagebits & 0x04) == 0)
 		return MEM_PAGE_NO_WE;
 	// Page access allowed.
 	return MEM_ALLOWED;
 }
 #undef MAPRAM
 /********************************************************
  * m68k memory read/write support functions for Musashi
  ********************************************************/
 /**
  * @brief	Check memory access permissions for a write operation.
  * @note	This used to be a single macro (merged with ACCESS_CHECK_RD), but
  * 			gcc throws warnings when you have a return-with-value in a void
  * 			function, even if the return-with-value is completely unreachable.
  * 			Similarly it doesn't like it if you have a return without a value
  * 			in a non-void function, even if it's impossible to ever reach the
  * 			return-with-no-value. UGH!
  */
 #define ACCESS_CHECK_WR() do {									\
 		/* MEM_STATUS st; */									\
 		switch (checkMemoryAccess(address, true)) {				\
 			case MEM_ALLOWED:									\
 				/* Access allowed */							\
 				break;											\
 			case MEM_PAGEFAULT:									\
 				/* Page fault */								\
 				state.genstat = 0x8FFF;							\
 				m68k_pulse_bus_error();							\
 				return;											\
 			case MEM_UIE:										\
 				/* User access to memory above 4MB */			\
 				state.genstat = 0x9EFF;							\
 				m68k_pulse_bus_error();							\
 				return;											\
 			case MEM_KERNEL:									\
 			case MEM_PAGE_NO_WE:								\
 				/* kernel access or page not write enabled */	\
 				/* TODO: which regs need setting? */			\
 				m68k_pulse_bus_error();							\
 				return;											\
 		}														\
 	} while (false)
 /**
  * @brief Check memory access permissions for a read operation.
  * @note	This used to be a single macro (merged with ACCESS_CHECK_WR), but
  * 			gcc throws warnings when you have a return-with-value in a void
  * 			function, even if the return-with-value is completely unreachable.
  * 			Similarly it doesn't like it if you have a return without a value
  * 			in a non-void function, even if it's impossible to ever reach the
  * 			return-with-no-value. UGH!
  */
 #define ACCESS_CHECK_RD() do {									\
 		/* MEM_STATUS st; */									\
 		switch (checkMemoryAccess(address, false)) {			\
 			case MEM_ALLOWED:									\
 				/* Access allowed */							\
 				break;											\
 			case MEM_PAGEFAULT:									\
 				/* Page fault */								\
 				state.genstat = 0xCFFF;							\
 				m68k_pulse_bus_error();							\
 				return 0xFFFFFFFF;								\
 			case MEM_UIE:										\
 				/* User access to memory above 4MB */			\
 				state.genstat = 0xDEFF;							\
 				m68k_pulse_bus_error();							\
 				return 0xFFFFFFFF;								\
 			case MEM_KERNEL:									\
 			case MEM_PAGE_NO_WE:								\
 				/* kernel access or page not write enabled */	\
 				/* TODO: which regs need setting? */			\
 				m68k_pulse_bus_error();							\
 				return 0xFFFFFFFF;								\
 		}														\
 	} while (false)
 /**
  * @brief Read M68K memory, 32-bit
  */
 uint32_t m68k_read_memory_32(uint32_t address)
 {
 	uint32_t data = 0xFFFFFFFF;
 	// If ROMLMAP is set, force system to access ROM
 	if (!state.romlmap)
 		address |= 0x800000;
 	// Check access permissions
 	ACCESS_CHECK_RD();
 	if ((address >= 0x800000) && (address <= 0xBFFFFF)) {
 		// ROM access
 		data = RD32(state.rom, address, ROM_SIZE - 1);
 	} else if (address <= (state.ram_size - 1)) {
 		// RAM access
 		data = RD32(state.ram, mapAddr(address, false), state.ram_size - 1);
 	} else if ((address >= 0x420000) && (address <= 0x427FFF)) {
 		// VRAM access
 		data = RD32(state.vram, address, 0x7FFF);
 	} else if ((address >= 0x400000) && (address <= 0x4007FF)) {
 		// Map RAM access
 		data = RD32(state.map, address, 0x7FF);
 	} else {
 		// I/O register -- TODO
 		printf("RD32 0x%08X ==> ??? %s\n", address, m68k_get_reg(NULL, M68K_REG_SR) & 0x2000 ? "[SV]" : "");
 	}
 	return data;
 }
 /**
  * @brief Read M68K memory, 16-bit
  */
 uint32_t m68k_read_memory_16(uint32_t address)
 {
 	uint16_t data = 0xFFFF;
 	// If ROMLMAP is set, force system to access ROM
 	if (!state.romlmap)
 		address |= 0x800000;
 	// Check access permissions
 	ACCESS_CHECK_RD();
 	if ((address >= 0x800000) && (address <= 0xBFFFFF)) {
 		// ROM access
 		data = RD16(state.rom, address, ROM_SIZE - 1);
 	} else if (address <= (state.ram_size - 1)) {
 		// RAM access
 		data = RD16(state.ram, mapAddr(address, false), state.ram_size - 1);
 	} else if ((address >= 0x420000) && (address <= 0x427FFF)) {
 		// VRAM access
 		data = RD16(state.vram, address, 0x7FFF);
 	} else if ((address >= 0x400000) && (address <= 0x4007FF)) {
 		// Map RAM access
 		data = RD16(state.map, address, 0x7FF);
 	} else {
 		// I/O register -- TODO
 		printf("RD16 0x%08X ==> ??? %s\n", address, m68k_get_reg(NULL, M68K_REG_SR) & 0x2000 ? "[SV]" : "");
 	}
 	return data;
 }
 /**
  * @brief Read M68K memory, 8-bit
  */
 uint32_t m68k_read_memory_8(uint32_t address)
 {
 	uint8_t data = 0xFF;
 	// If ROMLMAP is set, force system to access ROM
 	if (!state.romlmap)
 		address |= 0x800000;
 	// Check access permissions
 	ACCESS_CHECK_RD();
 	if ((address >= 0x800000) && (address <= 0xBFFFFF)) {
 		// ROM access
 		data = RD8(state.rom, address, ROM_SIZE - 1);
 	} else if (address <= (state.ram_size - 1)) {
 		// RAM access
 		data = RD8(state.ram, mapAddr(address, false), state.ram_size - 1);
 	} else if ((address >= 0x420000) && (address <= 0x427FFF)) {
 		// VRAM access
 		data = RD8(state.vram, address, 0x7FFF);
 	} else if ((address >= 0x400000) && (address <= 0x4007FF)) {
 		// Map RAM access
 		data = RD8(state.map, address, 0x7FF);
 	} else {
 		// I/O register -- TODO
 		printf("RD08 0x%08X ==> ??? %s\n", address, m68k_get_reg(NULL, M68K_REG_SR) & 0x2000 ? "[SV]" : "");
 	}
 	return data;
 }
 /**
  * @brief Write M68K memory, 32-bit
  */
 void m68k_write_memory_32(uint32_t address, uint32_t value)
 {
 	// If ROMLMAP is set, force system to access ROM
 	if (!state.romlmap)
 		address |= 0x800000;
 	// Check access permissions
 	ACCESS_CHECK_WR();
 	if ((address >= 0x800000) && (address <= 0xBFFFFF)) {
 		// ROM access
 		// According to HwNote15 (John B. Milton), there is no write protection
 		// here. You can write to ROM, but nothing happens.
 	} else if (address <= (state.ram_size - 1)) {
 		// RAM access
 		WR32(state.ram, mapAddr(address, true), state.ram_size - 1, value);
 	} else if ((address >= 0x420000) && (address <= 0x427FFF)) {
 		// VRAM access
 		WR32(state.vram, address, 0x7fff, value);
 	} else if ((address >= 0x400000) && (address <= 0x4007FF)) {
 		// Map RAM access
 		WR32(state.map, address, 0x7FF, value);
 	} else {
 		switch (address) {
 			case 0xE43000:	state.romlmap = ((value & 0x8000) == 0x8000); break;	// GCR3: ROMLMAP
 			default:		printf("WR32 0x%08X ==> 0x%08X %s\n", address, value, m68k_get_reg(NULL, M68K_REG_SR) & 0x2000 ? "[SV]" : ""); break;
 		}
 	}
 }
 /**
  * @brief Write M68K memory, 16-bit
  */
 void m68k_write_memory_16(uint32_t address, uint32_t value)
 {
 	// If ROMLMAP is set, force system to access ROM
 	if (!state.romlmap)
 		address |= 0x800000;
 	// Check access permissions
 	ACCESS_CHECK_WR();
 	if ((address >= 0x800000) && (address <= 0xBFFFFF)) {
 		// ROM access
 		// According to HwNote15 (John B. Milton), there is no write protection
 		// here. You can write to ROM, but nothing happens.
 	} else if (address <= (state.ram_size - 1)) {
 		// RAM access
 		WR16(state.ram, mapAddr(address, true), state.ram_size - 1, value);
 	} else if ((address >= 0x420000) && (address <= 0x427FFF)) {
 		// VRAM access
 		WR16(state.vram, address, 0x7fff, value);
 	} else if ((address >= 0x400000) && (address <= 0x4007FF)) {
 		// Map RAM access
 		WR16(state.map, address, 0x7FF, value);
 	} else {
 		switch (address) {
 			case 0xE43000:	state.romlmap = ((value & 0x8000) == 0x8000); break;	// GCR3: ROMLMAP
 			default:		printf("WR16 0x%08X ==> 0x%04X %s\n", address, value, m68k_get_reg(NULL, M68K_REG_SR) & 0x2000 ? "[SV]" : ""); break;
 		}
 		if (address == 0x4A0000) {
 			printf("\tLED WRITE: %s %s %s %s\n",
 					value & 0x800 ? "-" : "R",
 					value & 0x400 ? "-" : "G",
 					value & 0x200 ? "-" : "Y",
 					value & 0x100 ? "-" : "R"
 					);
 		}
 	}
 }
 /**
  * @brief Write M68K memory, 8-bit
  */
 void m68k_write_memory_8(uint32_t address, uint32_t value)
 {
 	// If ROMLMAP is set, force system to access ROM
 	if (!state.romlmap)
 		address |= 0x800000;
 	// Check access permissions
 	ACCESS_CHECK_WR();
 	if ((address >= 0x800000) && (address <= 0xBFFFFF)) {
 		// ROM access
 		// According to HwNote15 (John B. Milton), there is no write protection
 		// here. You can write to ROM, but nothing happens.
 	} else if (address <= (state.ram_size - 1)) {
 		// RAM access
 		WR8(state.ram, mapAddr(address, true), state.ram_size - 1, value);
 	} else if ((address >= 0x420000) && (address <= 0x427FFF)) {
 		// VRAM access
 		WR8(state.vram, address, 0x7fff, value);
 	} else if ((address >= 0x400000) && (address <= 0x4007FF)) {
 		// Map RAM access
 		WR8(state.map, address, 0x7FF, value);
 	} else {
 		switch (address) {
 			case 0xE43000:	state.romlmap = ((value & 0x80) == 0x80); break;	// GCR3: ROMLMAP
 			default:		printf("WR08 0x%08X ==> 0x%02X %s\n", address, value, m68k_get_reg(NULL, M68K_REG_SR) & 0x2000 ? "[SV]" : ""); break;
 		}
 	}
 }
 // for the disassembler
 uint32_t m68k_read_disassembler_32(uint32_t addr) { return m68k_read_memory_32(addr); }
 uint32_t m68k_read_disassembler_16(uint32_t addr) { return m68k_read_memory_16(addr); }
 uint32_t m68k_read_disassembler_8 (uint32_t addr) { return m68k_read_memory_8 (addr); }
 /****************************
  * blessed be thy main()...
  ****************************/
 int main(void)
 {
 	// copyright banner
 	printf("FreeBee: A Quick-and-Dirty AT&T 3B1 Emulator. Version %s, %s mode.\n", VER_FULLSTR, VER_BUILD_TYPE);
 	printf("Copyright (C) 2010 P. A. Pemberton. All rights reserved.\nLicensed under the Apache License Version 2.0.\n");
 	printf("Musashi M680x0 emulator engine developed by Karl Stenerud <kstenerud@gmail.com>\n");
 	printf("Built %s by %s@%s.\n", VER_COMPILE_DATETIME, VER_COMPILE_BY, VER_COMPILE_HOST);
 	printf("Compiler: %s\n", VER_COMPILER);
 	printf("CFLAGS: %s\n", VER_CFLAGS);
 	printf("\n");
 	// set up system state
 	// 512K of RAM
 	state_init(512*1024);
 	// set up musashi and reset the CPU
 	m68k_set_cpu_type(M68K_CPU_TYPE_68010);
 	m68k_pulse_reset();
 	// Set up SDL
 	if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER) == -1) {
 		printf("Could not initialise SDL: %s.\n", SDL_GetError());
 		exit(EXIT_FAILURE);
 	}
 	// Make sure SDL cleans up after itself
 	atexit(SDL_Quit);
 	// Set up the video display
 	SDL_Surface *screen = NULL;
 	if ((screen = SDL_SetVideoMode(720, 384, 8, SDL_SWSURFACE | SDL_ANYFORMAT)) == NULL) {
 		printf("Could not find a suitable video mode: %s.\n", SDL_GetError());
 		exit(EXIT_FAILURE);
 	}
 	printf("Set %dx%d at %d bits-per-pixel mode\n\n", screen->w, screen->h, screen->format->BitsPerPixel);
 	SDL_WM_SetCaption("FreeBee 3B1 emulator", "FreeBee");
 	/***
 	 * The 3B1 CPU runs at 10MHz, with DMA running at 1MHz and video refreshing at
 	 * around 60Hz (???), with a 60Hz periodic interrupt.
 	 */
 	const uint32_t TIMESLOT_FREQUENCY = 240;	// Hz
 	const uint32_t MILLISECS_PER_TIMESLOT = 1e3 / TIMESLOT_FREQUENCY;
 	const uint32_t CLOCKS_PER_60HZ = (10e6 / 60);
 	uint32_t next_timeslot = SDL_GetTicks() + MILLISECS_PER_TIMESLOT;
 	uint32_t clock_cycles = 0;
 	bool exitEmu = false;
 	for (;;) {
 		// Run the CPU for however many cycles we need to. CPU core clock is
 		// 10MHz, and we're running at 240Hz/timeslot. Thus: 10e6/240 or
 		// 41667 cycles per timeslot.
 		clock_cycles += m68k_execute(10e6/TIMESLOT_FREQUENCY);
 		// TODO: run DMA here
 		// Is it time to run the 60Hz periodic interrupt yet?
 		if (clock_cycles > CLOCKS_PER_60HZ) {
 			// TODO: refresh screen
 			// TODO: trigger periodic interrupt (if enabled)
 			// decrement clock cycle counter, we've handled the intr.
 			clock_cycles -= CLOCKS_PER_60HZ;
 		}
 		// make sure frame rate is equal to real time
 		uint32_t now = SDL_GetTicks();
 		if (now < next_timeslot) {
 			// timeslot finished early -- eat up some time
 			SDL_Delay(next_timeslot - now);
 		} else {
 			// timeslot finished late -- skip ahead to gain time
 			// TODO: if this happens a lot, we should let the user know
 			// that their PC might not be fast enough...
 			next_timeslot = now;
 		}
 		// advance to the next timeslot
 		next_timeslot += MILLISECS_PER_TIMESLOT;
 		// if we've been asked to exit the emulator, then do so.
 		if (exitEmu) break;
 	}
 	// shut down and exit
 	SDL_Quit();
 	return 0;
 }

3b1emu / annotate

src/main.c@a44afcf2354c (annotated)

src/main.c