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@ggnkua
ggnkua committed Oct 21, 2023
1 parent f4ac51f commit 8faa8a8
Showing 1 changed file with 232 additions and 0 deletions.
232 changes: 232 additions & 0 deletions usm.c
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#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>
#include <string.h>
#include <stdint.h>

char cart[1024 * 128];
char prg_temp_buf[1024 * 128];

#if defined (_WIN32)
#pragma pack(2)
#endif
#if defined(__linux__) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__APPLE__)
#pragma pack(push,2)
#endif

typedef struct
{
uint32_t CA_NEXT; // Pointer to the next application header (or NULL if there are no more).
uint32_t CA_INIT; // Pointer to the application's initialization code. The high eight bits of this pointer have a special meaning as follows:
// Bit Set Meaning
// 0 Execute prior to display memory and interrupt vector initialization.
// 1 Execute just before GEMDOS is initialized.
// 2 (unused)
// 3 Execute prior to boot disk.
// 4 (unused)
// 5 Application is a Desk Accessory.
// 6 Application is not a GEM application.
// 7 Application needs parameters.
uint32_t CA_RUN; // Pointer to application's main entry point.
uint16_t CA_TIME; // Standard GEMDOS time stamp.
uint16_t CA_DATE; // Standard GEMDOS date stamp.
uint32_t CA_SIZE; // Size of application in bytes.
int8_t CA_FILENAME[14]; // NULL terminated ASCII filename in standard GEMDOS 8+3 format.
} CA_HEADER;

typedef struct
{
uint8_t PRG_magic; // This WORD contains the magic value (0x601A).
uint32_t PRG_tsize; // This LONG contains the size of the TEXT segment in bytes.
uint32_t PRG_dsize; // This LONG contains the size of the DATA segment in bytes.
uint32_t PRG_bsize; // This LONG contains the size of the BSS segment in bytes.
uint32_t PRG_ssize; // This LONG contains the size of the symbol table in bytes.
uint32_t PRG_res1; // This LONG is unused and is currently reserved.
uint32_t PRGFLAGS; // This LONG contains flags which define certain process characteristics (as defined below).
uint8_t ABSFLAG; // This WORD flag should be non-zero to indicate that the program has no fixups or 0 to indicate it does.Since some versions of TOS handle files with this value being non-zero incorrectly, it is better to represent a program having no fixups with 0 here and placing a 0 longword as the fixup offset.
} PRG_HEADER;
#if defined(__linux__) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__APPLE__)
#pragma pack(pop)
#endif

#if defined(__linux__) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__APPLE__) || defined (_WIN32)
#define BYTESWAP_LONG(x) (((x&0xff000000)>>24)|((x&0x00ff0000)>>8)|((x&0x0000ff00)<<8)|((x&0x000000ff)<<24))
#define BYTESWAP_WORD(x) (((x&0xff00)>>8)|((x&0x00ff)<<8))
#else
#define BYTESWAP_LONG(x) x
#define BYTESWAP_WORD(x) x
#endif

int main(int argc, char **argv)
{
int diagnostic = 0;
char *cart_start = cart;
int cart_current_offset = 0;
int steem_cart = 0;
int i;

if (argc < 3)
{
printf("Usage: %s [s] image_filename <list_of_programs_to_add>\n"
"pass s to create a steem engine compatible cart image file\n"
"For now, use upper case filenames\n", argv[0]);
return -1;
}

// Eat the program filename argument
argv++;
argc--;

if (*argv[0] == 's')
{
steem_cart = 1;
argv++;
argc--;
}
else if (*argv[0] == 'd')
{
// Diagnostic cartridges are executed almost immediately after a system reset.
// The OS uses a 680x0 JMP instruction to begin execution at address 0xFA0004
// after having set the Interrupt Priority Level (IPL) to 7, entering supervisor mode,
// and executing a RESET instruction to reset external hardware devices.
unsigned long diagnostic_magic = 0xFA52255F;
printf("Diagnostic cart not yet supported - exiting\n");
return -1;
}


if (diagnostic)
{
// ...
}

unsigned char *fill = cart;
for (i = 0; i < 128 * 1024 / 4; i++)
{
*fill++ = 'G';
*fill++ = 'G';
*fill++ = 'N';
*fill++ = '!';
}

*(unsigned long *)&cart_start[cart_current_offset] = BYTESWAP_LONG(0xABCDEF42);
cart_current_offset += 4;
unsigned long bss_hardcoded_address = 0x20000; // TODO UI

for (i = 1; i < argc; i++)
{
FILE *f = fopen(argv[i], "rb");
if (!f)
{
printf("File %s not found - exiting\n",argv[i]);
return -1;
}

fseek(f, 0, SEEK_END);
long file_size = ftell(f);
fseek(f, 0, SEEK_SET);

if (file_size > 128 * 1024)
{
// Without any further checks, this will not fit. RIP
fclose(f);
printf("File %s will not fit in image - exiting\n", argv[i]);
return -1;
}

fread(prg_temp_buf, file_size, 1, f); // TODO check errors etc
fclose(f);

long header_size = sizeof(PRG_HEADER);
unsigned long program_size;
PRG_HEADER *ph = (PRG_HEADER *)prg_temp_buf;
// TODO: sanity checks for values here
if (BYTESWAP_WORD(ph->PRG_magic) != 0x601a)
{
// TODO
}

program_size = (BYTESWAP_LONG(ph->PRG_tsize) + BYTESWAP_LONG(ph->PRG_dsize) + 1) & 0xfffffffe; // align to 2 bytes

if (program_size > 128 * 1024 - cart_current_offset - sizeof(CA_HEADER))
{
fclose(f);
printf("File %s will not fit in image - exiting\n", argv[i]);
return -1;
}

// Write header
unsigned long init_flags = 0 << 24; // TODO UI
CA_HEADER *h = (CA_HEADER *)&cart_start[cart_current_offset];
h->CA_NEXT = 0;
if (i < argc - 1)
{
h->CA_NEXT = BYTESWAP_LONG(0xfa0000 + cart_current_offset + sizeof(CA_HEADER) + program_size);
}
h->CA_INIT = BYTESWAP_LONG(0xfa0000 + cart_current_offset + sizeof(CA_HEADER) + init_flags);
h->CA_RUN = BYTESWAP_LONG(0xfa0000 + cart_current_offset + sizeof(CA_HEADER));
h->CA_TIME = 0; //TODO figure out from file info (if we really care)
h->CA_DATE = 0; //TODO figure out from file info (if we really care)
h->CA_SIZE = BYTESWAP_LONG(program_size);
memset(h->CA_FILENAME, 0, 14);
strcpy(h->CA_FILENAME, argv[i]); // TODO: Truncate to 8.3 if needed, convert to uppercase

cart_current_offset += sizeof(CA_HEADER);

memcpy(&cart_start[cart_current_offset], prg_temp_buf + header_size, program_size);

// Relocate program
if (!ph->ABSFLAG)
{
unsigned long program_start_address = 0xfa0000 + cart_current_offset;
unsigned char *current_relocation = &cart_start[cart_current_offset];
unsigned char *reloc = &prg_temp_buf[header_size + BYTESWAP_LONG(ph->PRG_tsize) + BYTESWAP_LONG(ph->PRG_dsize) + BYTESWAP_LONG(ph->PRG_ssize)]; // TODO: Sanity check values
unsigned long offset = BYTESWAP_LONG(*(uint32_t *)reloc);
reloc += 4;
for (;;)
{
if (offset == 1)
{
current_relocation += 254;
}
else
{
current_relocation += offset;
unsigned long off = BYTESWAP_LONG(*(uint32_t *)current_relocation);
if (off < program_size)
{
// It's within the text/data section, relocate as usual
*(uint32_t *)current_relocation = BYTESWAP_LONG(program_start_address + off);
}
else
{
// It's BSS area, point it to the hardcoded BSS address
*(uint32_t *)current_relocation = BYTESWAP_LONG(off - program_size + bss_hardcoded_address);
}
}
if (!*reloc) break;
offset = *reloc++;
}
}

cart_current_offset += program_size;

}

FILE *f = fopen(argv[0], "wb");
if (!f)
{
printf("Could not create image file %s - exiting\n", argv[0]);
return -1;
}
if (steem_cart)
{
// Write an extra 0.l at the start of the file
steem_cart = 0;
fwrite(&steem_cart, 4, 1, f);
}
fwrite(cart_start, 128*1024, 1, f);
fclose(f);

return 0;
}

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