psxc/src/boot.c

#include "boot.h"
#include "cpu.h"
#include "insn.h"
#include "log.h"
#include "psx.h"

#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

static const uint8_t MAGIC[0x10] = "PS-X EXE";
static const uint8_t RESERVED[0x10] = {0};

psx_header_t parse_psx_header(byte_arr_t *prgm)
{
    psx_header_t header;

    // TODO: Convert asserts into recoverable error
    debug("Checking header struct size");
    assert(sizeof header == 0x38 - 0x10);

    debug("Checking program size is greater than header");
    assert(prgm->size >= 0x800);

    debug("Checking magic number in header");
    assert(memcmp(MAGIC, prgm->data, sizeof MAGIC) == 0);

    memcpy(&header, &prgm->data[sizeof MAGIC], sizeof header);

    debug("Checking file size in header matches program size");
    assert(header.size_file == prgm->size - 0x800);

    debug("Checking A34h region is zero");
    assert(memcmp(RESERVED, &prgm->data[0x38], sizeof RESERVED) == 0);

    return header;
}

uint32_t translate_addr(uint32_t addr)
{
    if (addr >= 0xA0000000)
    {
        addr = addr - 0xA0000000;
    }
    else if (addr >= 0x80000000)
    {
        addr = addr - 0x80000000;
    }

    return addr;
}

void boot_psx_prgm(byte_arr_t *prgm)
{
    debug("Parsing program header");

    psx_header_t header = parse_psx_header(prgm);

    debug("Program header");
    debug("size=%u bytes", header.size_file);
    debug("pc=%08x, gp=%08x, sp=%08x, fp=%08x", header.pc, header.gp, header.sp, header.fp);
    debug("data=%08x (%u bytes)", header.addr_data, header.size_data);
    debug("bss=%08x (%u bytes)", header.addr_bss, header.size_bss);
    debug("dest=%08x", header.addr_dest);

    cpu_t *cpu = malloc(sizeof *cpu);

    uint32_t start = translate_addr(header.addr_dest);
    assert(start + header.size_file < MAIN_RAM_SIZE);
    memcpy(&cpu->main_ram[start], &prgm->data[0x800], header.size_file);

    cpu->pc = header.pc;
    cpu->regs[REG_GP] = header.gp;
    cpu->regs[REG_SP] = header.sp;
    cpu->regs[REG_FP] = header.fp;

    psx_t psx = {header, cpu};

    while (1)
    {
        debug("Executing instruction at %08x", psx.cpu->pc);

        const uint32_t insn = cpu_read32(cpu, psx.cpu->pc);
        insn_execute(cpu, insn);

        psx.cpu->pc += 1;
    }
}