Duckstation/src/core/bios.cpp

#include "bios.h"
#include "YBaseLib/Log.h"
#include "YBaseLib/MD5Digest.h"
#include "cpu_disasm.h"
#include <cerrno>
Log_SetChannel(BIOS);

namespace BIOS {
static constexpr Hash MakeHashFromString(const char str[])
{
  Hash h{};
  for (int i = 0; str[i] != '\0'; i++)
  {
    u8 nibble = 0;
    char ch = str[i];
    if (ch >= '0' && ch <= '9')
      nibble = str[i] - '0';
    else if (ch >= 'a' && ch <= 'z')
      nibble = 0xA + (str[i] - 'a');
    else if (ch >= 'A' && ch <= 'Z')
      nibble = 0xA + (str[i] - 'A');

    h.bytes[i / 2] |= nibble << (((i & 1) ^ 1) * 4);
  }
  return h;
}

std::string Hash::ToString() const
{
  char str[33];
  std::snprintf(str, sizeof(str), "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x", bytes[0],
                bytes[1], bytes[2], bytes[3], bytes[4], bytes[5], bytes[6], bytes[7], bytes[8], bytes[9], bytes[10],
                bytes[11], bytes[12], bytes[13], bytes[14], bytes[15]);
  return str;
}

static constexpr Hash SCPH_1000_HASH = MakeHashFromString("239665b1a3dade1b5a52c06338011044");
static constexpr Hash SCPH_1001_HASH = MakeHashFromString("924e392ed05558ffdb115408c263dccf");
static constexpr Hash SCPH_1002_HASH = MakeHashFromString("54847e693405ffeb0359c6287434cbef");
static constexpr Hash SCPH_5500_HASH = MakeHashFromString("8dd7d5296a650fac7319bce665a6a53c");
static constexpr Hash SCPH_5501_HASH = MakeHashFromString("490f666e1afb15b7362b406ed1cea246");
static constexpr Hash SCPH_5502_HASH = MakeHashFromString("32736f17079d0b2b7024407c39bd3050");

Hash GetHash(const Image& image)
{
  Hash hash;
  MD5Digest digest;
  digest.Update(image.data(), static_cast<u32>(image.size()));
  digest.Final(hash.bytes);
  return hash;
}

std::optional<Image> LoadImageFromFile(std::string_view filename)
{
  Image ret(BIOS_SIZE);
  std::string filename_str(filename);
  std::FILE* fp = std::fopen(filename_str.c_str(), "rb");
  if (!fp)
  {
    Log_ErrorPrintf("Failed to open BIOS image '%s', errno=%d", filename_str.c_str(), errno);
    return std::nullopt;
  }

  std::fseek(fp, 0, SEEK_END);
  const u32 size = static_cast<u32>(std::ftell(fp));
  std::fseek(fp, 0, SEEK_SET);

  if (size != BIOS_SIZE)
  {
    Log_ErrorPrintf("BIOS image '%s' mismatch, expecting %u bytes, got %u bytes", filename_str.c_str(), BIOS_SIZE,
                    size);
    std::fclose(fp);
    return std::nullopt;
  }

  if (std::fread(ret.data(), 1, ret.size(), fp) != ret.size())
  {
    Log_ErrorPrintf("Failed to read BIOS image '%s'", filename_str.c_str());
    std::fclose(fp);
    return std::nullopt;
  }

  std::fclose(fp);
  return ret;
}

std::optional<Hash> GetHashForFile(const std::string_view filename)
{
  auto image = LoadImageFromFile(filename);
  if (!image)
    return std::nullopt;

  return GetHash(*image);
}

bool IsValidHashForRegion(ConsoleRegion region, const Hash& hash)
{
  switch (region)
  {
    case ConsoleRegion::NTSC_J:
      return (hash == SCPH_1000_HASH || hash == SCPH_5500_HASH);

    case ConsoleRegion::NTSC_U:
      return (hash == SCPH_1001_HASH || hash == SCPH_5501_HASH);

    case ConsoleRegion::PAL:
      return (hash == SCPH_1002_HASH || hash == SCPH_5502_HASH);

    case ConsoleRegion::Auto:
    default:
      return false;
  }
}

void PatchBIOS(Image& bios, u32 address, u32 value, u32 mask /*= UINT32_C(0xFFFFFFFF)*/)
{
  const u32 phys_address = address & UINT32_C(0x1FFFFFFF);
  const u32 offset = phys_address - BIOS_BASE;
  Assert(phys_address >= BIOS_BASE && offset < BIOS_SIZE);

  u32 existing_value;
  std::memcpy(&existing_value, &bios[offset], sizeof(existing_value));
  u32 new_value = (existing_value & ~mask) | value;
  std::memcpy(&bios[offset], &new_value, sizeof(new_value));

  SmallString old_disasm, new_disasm;
  CPU::DisassembleInstruction(&old_disasm, address, existing_value);
  CPU::DisassembleInstruction(&new_disasm, address, new_value);
  Log_DevPrintf("BIOS-Patch 0x%08X (+0x%X): 0x%08X %s -> %08X %s", address, offset, existing_value,
                old_disasm.GetCharArray(), new_value, new_disasm.GetCharArray());
}

bool PatchBIOSEnableTTY(Image& image, const Hash& hash)
{
  if (hash != SCPH_1000_HASH && hash != SCPH_1001_HASH && hash != SCPH_1002_HASH && hash != SCPH_5500_HASH &&
      hash != SCPH_5501_HASH && hash != SCPH_5502_HASH)
  {
    Log_WarningPrintf("Incompatible version for TTY patch: %s", hash.ToString().c_str());
    return false;
  }

  Log_InfoPrintf("Patching BIOS to enable TTY/printf");
  PatchBIOS(image, 0x1FC06F0C, 0x24010001);
  PatchBIOS(image, 0x1FC06F14, 0xAF81A9C0);
  return true;
}

bool PatchBIOSFastBoot(Image& image, const Hash& hash)
{
  if (hash != SCPH_1000_HASH && hash != SCPH_1001_HASH && hash != SCPH_1002_HASH && hash != SCPH_5500_HASH &&
      hash != SCPH_5501_HASH && hash != SCPH_5502_HASH)
  {
    Log_WarningPrintf("Incompatible version for fast-boot patch: %s", hash.ToString().c_str());
    return false;
  }

  // Replace the shell entry point with a return back to the bootstrap.
  Log_InfoPrintf("Patching BIOS to skip intro");
  PatchBIOS(image, 0x1FC18000, 0x03E00008);
  PatchBIOS(image, 0x1FC18004, 0x00000000);
  return true;
}

bool PatchBIOSForEXE(Image& image, u32 r_pc, u32 r_gp, u32 r_sp, u32 r_fp)
{
  // pc has to be done first because we can't load it in the delay slot
  PatchBIOS(image, 0xBFC06FF0, UINT32_C(0x3C080000) | r_pc >> 16);                // lui $t0, (r_pc >> 16)
  PatchBIOS(image, 0xBFC06FF4, UINT32_C(0x35080000) | (r_pc & UINT32_C(0xFFFF))); // ori $t0, $t0, (r_pc & 0xFFFF)
  PatchBIOS(image, 0xBFC06FF8, UINT32_C(0x3C1C0000) | r_gp >> 16);                // lui $gp, (r_gp >> 16)
  PatchBIOS(image, 0xBFC06FFC, UINT32_C(0x379C0000) | (r_gp & UINT32_C(0xFFFF))); // ori $gp, $gp, (r_gp & 0xFFFF)
  PatchBIOS(image, 0xBFC07000, UINT32_C(0x3C1D0000) | r_sp >> 16);                // lui $sp, (r_sp >> 16)
  PatchBIOS(image, 0xBFC07004, UINT32_C(0x37BD0000) | (r_sp & UINT32_C(0xFFFF))); // ori $sp, $sp, (r_sp & 0xFFFF)
  PatchBIOS(image, 0xBFC07008, UINT32_C(0x3C1E0000) | r_fp >> 16);                // lui $fp, (r_fp >> 16)
  PatchBIOS(image, 0xBFC0700C, UINT32_C(0x01000008));                             // jr $t0
  PatchBIOS(image, 0xBFC07010, UINT32_C(0x37DE0000) | (r_fp & UINT32_C(0xFFFF))); // ori $fp, $fp, (r_fp & 0xFFFF)
  return true;
}

bool IsValidPSExeHeader(const PSEXEHeader& header, u32 file_size)
{
  static constexpr char expected_id[] = {'P', 'S', '-', 'X', ' ', 'E', 'X', 'E'};
  if (std::memcmp(header.id, expected_id, sizeof(expected_id)) != 0)
    return false;

  if (header.file_size > file_size)
    return false;

  return true;
}

} // namespace BIOS