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Support for booting from floppy

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MKBOOT and boot chain now support booting from the floppy drive's volume boot record.
This commit is contained in:
Peter Weingartner 2022-05-16 16:07:31 -04:00
parent 30e728be14
commit e0f79f3e6c
5 changed files with 9789 additions and 9725 deletions
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build/foenixmcp_a2560k.bin
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112
src/boot.c
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@ -41,12 +41,32 @@
/* TODO: move this to constants.h */
#define BOOT_SECTOR_BUFFER ((unsigned char *)0x00004000)
#define BOOT_CODE_MBR_OFF 0x000 /* Offset to the code in the MBR */
#define BOOT_CPUID_MBR_OFF 0x004 /* Offset to the CPUID in the MBR */
#define BOOT_SIG_MBR_OFF 0x006 /* Offset to the boot signature in the MBR */
#define BOOT_SECTOR_BUFFER ((unsigned char *)0x00004000)
#define BOOT_CODE_MBR_OFF 0x000 /* Offset to the code in the MBR */
#define BOOT_CPUID_MBR_OFF 0x004 /* Offset to the CPUID in the MBR */
#define BOOT_SIG_MBR_OFF 0x006 /* Offset to the boot signature in the MBR */
#define BOOT_SIG 0xF0E1 /* Foenix/MCP boot signature expected */
#define BOOT_SIG 0xF0E1 /* Foenix/MCP boot signature expected */
#define FDC_VBR_JUMP 0x000 // Intel 80x86 machine language jump... 3 bytes
#define FDC_VBR_OEMNAME 0x003 // OEM Name... 8 bytes
#define FDC_VBR_BPB 0x00B // BIOS Parameter Block
#define FDC_VBR_BYTES_PER_SECTOR 0x00B // Number of bytes per sector... 2 bytes
#define FDC_VBR_SECTORS_PER_CLUSTER 0x00D // Number of sectors per cluster... 1 byte
#define FDC_VBR_RESERVED_SECTORS 0x00E // Number of reserved sectors... 2 bytes
#define FDC_VBR_FAT_COUNT 0x010 // Number of file allocation tables... 1 byte
#define FDC_VBR_MAX_ROOT_ENTRIES 0x011 // Maximum number of root directory entries... 2 bytes
#define FDC_VBR_SECTORS 0x013 // Number of logical sectors in FAT12/16... 2 bytes
#define FDC_VBR_MEDIA_TYPE 0x015 // Media type code... 1 byte
#define FDC_VBR_SECTORS_PER_FAT 0x016 // Number of sectors per file allocation table... 2 bytes
#define FDC_VBR_SECTORS_PER_TRACK 0x018 // Number of sectors per track... 2 bytes
#define FDC_VBR_HEADS 0x01A // Number of heads... 2 bytes
#define FDC_VBR_HIDDEN_SECTORS 0x01C // Number of hidden sectors... 2 bytes
#define FDC_VBR_TOTAL_SECTORS 0x01E // Total number of sectors... 2 bytes
#define FDC_VBR_BOOT_CODE 0x060 // Start of boot sector code
#define BOOT_CODE_VBR_OFF FDC_VBR_BOOT_CODE /* Offset to the code in the VBR for floppy drives */
#define BOOT_CPUID_VBR_OFF BOOT_CODE_VBR_OFF+4 /* Offset to the CPUID in the VBR for floppy drives */
#define BOOT_SIG_VBR_OFF BOOT_CODE_VBR_OFF+6 /* Offset to the boot signature in the VBR for floppy drives */
const char * MCP_INIT_SDC = "/sd/system/mcp.init"; /**< Path to config file on the SD card */
const char * MCP_INIT_FDC = "/fd/system/mcp.init"; /**< Path to config file on the floppy drive */
@ -114,7 +134,16 @@ void cli_command_get(char * path) {
short is_bootable(unsigned char * sector, short device) {
switch(device) {
case BDEV_FDC:
// TODO: handled floppy drives
// The SDC and HDC boot off the MBR...
// Check for the CPUID and boot signature
if ((sector[BOOT_CPUID_VBR_OFF] == CPU_M68000) ||
(sector[BOOT_CPUID_VBR_OFF] == CPU_M68040)) {
if ((sector[BOOT_SIG_VBR_OFF] == ((BOOT_SIG >> 8) & 0x00FF)) &&
(sector[BOOT_SIG_VBR_OFF+1] == (BOOT_SIG & 0x00FF))) {
// The CPU is supported, and the boot signature is correct
return 1;
}
}
break;
case BDEV_SDC:
@ -150,7 +179,9 @@ void boot_sector_run(short device) {
switch(device) {
case BDEV_FDC:
// TODO: support floppy drives
// The FDC boots off the Volume Boot Record (offset 0x060)
boot_sector = (FUNC_V_2_V)(BOOT_SECTOR_BUFFER + BOOT_CODE_VBR_OFF);
boot_sector();
break;
case BDEV_SDC:
@ -446,6 +477,19 @@ void boot_from_bdev(short device) {
}
}
const unsigned char boot_from_file_sector[] = {
0x60, 0x00, 0x00, 0x06, // bra.w boot
CPU_M68000, 0x00, 0xf0, 0xe1, // dc.b CPU_M68000, 0, 0xf0, 0xe1
0x30, 0x3c, 0x00, 0x40, // boot: move.w #$40,d0
0x43, 0xfa, 0x00, 0x0e, // lea (path,pc),a1
0x22, 0x09, // move.l a1,d1
0x42, 0x82, // clr.l d2
0x42, 0x83, // clr.l d3
0x4e, 0x4f, // trap #15
0x4e, 0x71, // bootloop nop
0x60, 0xfc // bra bootloop
};
/**
* Make the indicated drive non booting by erasing the boot information
*
@ -461,9 +505,20 @@ short boot_non_booting(short device) {
// Try to read the current sector
short n = sys_bdev_read(device, 0, buffer, FSYS_SECTOR_SZ);
if (n == FSYS_SECTOR_SZ) {
// Boot record read... clear it out
for (int i = 0; i < 0x0DA; i++) {
buffer[i] = 0;
short sector_offset = 0;
if (device == BDEV_FDC) {
// Point to the beginning of the boot code for the FDC (VBR)
sector_offset = BOOT_CODE_VBR_OFF;
} else {
// Point to the beginning of the boot code for the SDC/HDD (MBR)
sector_offset = BOOT_CODE_MBR_OFF;
}
// Boot record read... clear out the boot code
for (int i = 0; i < sizeof(boot_from_file_sector); i++) {
buffer[sector_offset + i] = 0;
}
// Try to write it back
@ -491,19 +546,6 @@ short boot_non_booting(short device) {
return result;
}
const unsigned char boot_from_file_sector[] = {
0x60, 0x00, 0x00, 0x06, // bra.w boot
CPU_M68000, 0x00, 0xf0, 0xe1, // dc.b CPU_M68000, 0, 0xf0, 0xe1
0x30, 0x3c, 0x00, 0x40, // boot: move.w #$40,d0
0x43, 0xfa, 0x00, 0x0e, // lea (path,pc),a1
0x22, 0x09, // move.l a1,d1
0x42, 0x82, // clr.l d2
0x42, 0x83, // clr.l d3
0x4e, 0x4f, // trap #15
0x4e, 0x71, // bootloop nop
0x60, 0xfc // bra bootloop
};
/**
* Make the indicated drive booting from a file
*
@ -518,26 +560,38 @@ short boot_set_file(short device, const char * path) {
buffer = (unsigned char *)malloc(FSYS_SECTOR_SZ);
if (buffer != 0) {
// Try to read the current sector
bdev_init(device);
short n = sys_bdev_read(device, 0, buffer, FSYS_SECTOR_SZ);
if (n == FSYS_SECTOR_SZ) {
int sector_len = sizeof(boot_from_file_sector);
int sector_offset = 0;
int path_len = strlen(path);
// Boot record read... clear it out
for (i = 0; i < 0x1B0; i++) {
buffer[i] = 0;
if (device == BDEV_FDC) {
// Set up the floppy disk boot record
sector_offset = BOOT_CODE_VBR_OFF;
// Write 80x86 code to infinite loop at the start of the boot sector
// This will help maintain compatibility with MS-DOS and Windows machines
buffer[0] = 0xEB;
buffer[1] = 0xFF;
buffer[2] = 0x90;
} else {
// Set up the SDC or HDC master boot record
sector_offset = BOOT_CODE_MBR_OFF;
}
// Copy the boot code over
for (i = 0; i < sector_len; i++) {
buffer[i] = boot_from_file_sector[i];
buffer[sector_offset + i] = boot_from_file_sector[i];
}
// Insert the path
for (i = 0; i < path_len; i++) {
buffer[i + sector_len] = path[i];
buffer[sector_offset + i + sector_len] = path[i];
}
buffer[path_len + sector_len] = 0;
buffer[sector_offset + sector_len + path_len] = 0;
// Try to write it back
n = sys_bdev_write(device, 0, buffer, FSYS_SECTOR_SZ);

2
src/cli/dos_cmds.c
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@ -606,6 +606,8 @@ short cmd_mkboot(short screen, int argc, const char * argv[]) {
} else if (argc == 4) {
// Can be either -b or -s
dev = cli_eval_number(argv[1]);
if (strcmp("-b", argv[2]) == 0) {
// -b
mode = 1;

19398
src/mapfile
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2
src/version.h
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@ -7,6 +7,6 @@
#define VER_MAJOR 0
#define VER_MINOR 75
#define VER_BUILD 1
#define VER_BUILD 3
#endif