x86_stub.s

psp上的GBA模拟器

  jnz ext_store_u8            # if above perform an extended write
  shr $15, %ecx               # ecx = page number of address
  # load the corresponding memory map offset
  mov _memory_map_write(, %ecx, 4), %ecx
  test %ecx, %ecx             # see if it's NULL
  jz ext_store_u8             # if so perform an extended write
  and $0x7FFF, %eax           # isolate the lower 15bits of the address
  mov %dl, (%eax, %ecx)       # store the value
  # check for self-modifying code
  testb $0xFF, -32768(%eax, %ecx)
  jne smc_write
  ret                         # return

_execute_store_u16:
  mov %ecx, REG_PC(%ebx)      # write out the PC
  and $~0x01, %eax            # fix alignment
  mov %eax, %ecx              # ecx = address
  test $0xF0000000, %ecx      # check address range
  jnz ext_store_u16           # if above perform an extended write
  shr $15, %ecx               # ecx = page number of address
  # load the corresponding memory map offset
  mov _memory_map_write(, %ecx, 4), %ecx
  test %ecx, %ecx             # see if it's NULL
  jz ext_store_u16            # if so perform an extended write
  and $0x7FFF, %eax           # isolate the lower 15bits of the address
  mov %dx, (%eax, %ecx)       # store the value
  # check for self-modifying code
  testw $0xFFFF, -32768(%eax, %ecx)
  jne smc_write
  ret                         # return

# 16bit ext memory routines

ext_store_io16:
  and $0x3FF, %eax            # wrap around address
  and $0xFFFF, %edx
  call _write_io_register16   # perform 16bit I/O register write
  jmp write_epilogue          # see if it requires any system update

ext_store_palette16:
  and $0x3FF, %eax            # wrap around address

ext_store_palette16b:         # entry point for 8bit write
  mov %dx, _palette_ram(%eax) # write out palette value
  mov %edx, %ecx              # cx = dx
  shl $11, %ecx               # cx <<= 11 (red component is in high bits)
  mov %dh, %cl                # bottom bits of cx = top bits of dx
  shr $2, %cl                 # move the blue component to the bottom of cl
  and $0x03E0, %dx            # isolate green component of dx
  shl $1, %dx                 # make green component 6bits
  or %edx, %ecx               # combine green component into ecx
  # write out the freshly converted palette value
  mov %cx, _palette_ram_converted(%eax)
  ret                         # done

ext_store_vram16:
  and $0x1FFFF, %eax          # wrap around address
  cmp $0x18000, %eax          # see if address is in upper region
  jb ext_store_vram16b
  sub $0x8000, %eax           # if so wrap down

ext_store_vram16b:
  mov %dx, _vram(%eax)        # perform 16bit store
  ret

ext_store_oam16:
  movl $1, _oam_update        # flag OAM update
  and $0x3FF, %eax            # wrap around address
  mov %dx, _oam_ram(%eax)     # perform 16bit store
  ret

ext_store_rtc:
  and $0xFFFF, %edx           # make value 16bit
  and $0xFF, %eax             # mask address
  jmp _write_rtc              # write out RTC register

ext_store_u16_jtable:
  .long ext_store_ignore      # 0x00 BIOS, ignore
  .long ext_store_ignore      # 0x01 invalid, ignore
  .long ext_store_ignore      # 0x02 EWRAM, should have been hit already
  .long ext_store_ignore      # 0x03 IWRAM, should have been hit already
  .long ext_store_io16        # 0x04 I/O registers
  .long ext_store_palette16   # 0x05 Palette RAM
  .long ext_store_vram16      # 0x06 VRAM
  .long ext_store_oam16       # 0x07 OAM RAM
  .long ext_store_rtc         # 0x08 gamepak or RTC
  .long ext_store_ignore      # 0x09 gamepak, ignore
  .long ext_store_ignore      # 0x0A gamepak, ignore
  .long ext_store_ignore      # 0x0B gamepak, ignore
  .long ext_store_ignore      # 0x0C gamepak, ignore
  .long ext_store_eeprom      # 0x0D EEPROM (possibly)
  .long ext_store_ignore      # 0x0E Flash ROM/SRAM must be 8bit

ext_store_u16:
  mov %eax, %ecx              # ecx = address
  shr $24, %ecx               # ecx = address >> 24
  cmp $15, %ecx
  ja ext_store_ignore
  # ecx = ext_store_u16_jtable[address >> 24]
  mov ext_store_u16_jtable(, %ecx, 4), %ecx
  jmp *%ecx                   # jump to table index

_execute_store_u32:
  mov %ecx, REG_PC(%ebx)      # write out the PC
  and $~0x03, %eax            # fix alignment
  mov %eax, %ecx              # ecx = address
  test $0xF0000000, %ecx      # check address range
  jnz ext_store_u32           # if above perform an extended write
  shr $15, %ecx               # ecx = page number of address
  # load the corresponding memory map offset
  mov _memory_map_write(, %ecx, 4), %ecx
  test %ecx, %ecx             # see if it's NULL
  jz ext_store_u32            # if so perform an extended write
  and $0x7FFF, %eax           # isolate the lower 15bits of the address
  mov %edx, (%eax, %ecx)      # store the value
  # check for self-modifying code
  testl $0xFFFFFFFF, -32768(%eax, %ecx)
  jne smc_write
  ret                         # return it

# 32bit ext memory routines

ext_store_io32:
  and $0x3FF, %eax            # wrap around address
  call _write_io_register32   # perform 32bit I/O register write
  jmp write_epilogue          # see if it requires any system update

ext_store_palette32:
  and $0x3FF, %eax            # wrap around address
  call ext_store_palette16b   # write first 16bits
  add $2, %eax                # go to next address
  shr $16, %edx               # go to next 16bits
  jmp ext_store_palette16b    # write next 16bits

ext_store_vram32:
  and $0x1FFFF, %eax          # wrap around address
  cmp $0x18000, %eax          # see if address is in upper region
  jb ext_store_vram32b
  sub $0x8000, %eax           # if so wrap down

ext_store_vram32b:
  mov %edx, _vram(%eax)       # perform 32bit store
  ret

ext_store_oam32:
  movl $1, _oam_update        # flag OAM update
  and $0x3FF, %eax            # wrap around address
  mov %edx, _oam_ram(%eax)    # perform 32bit store
  ret

ext_store_u32_jtable:
  .long ext_store_ignore      # 0x00 BIOS, ignore
  .long ext_store_ignore      # 0x01 invalid, ignore
  .long ext_store_ignore      # 0x02 EWRAM, should have been hit already
  .long ext_store_ignore      # 0x03 IWRAM, should have been hit already
  .long ext_store_io32        # 0x04 I/O registers
  .long ext_store_palette32   # 0x05 Palette RAM
  .long ext_store_vram32      # 0x06 VRAM
  .long ext_store_oam32       # 0x07 OAM RAM
  .long ext_store_ignore      # 0x08 gamepak, ignore (no RTC in 32bit)
  .long ext_store_ignore      # 0x09 gamepak, ignore
  .long ext_store_ignore      # 0x0A gamepak, ignore
  .long ext_store_ignore      # 0x0B gamepak, ignore
  .long ext_store_ignore      # 0x0C gamepak, ignore
  .long ext_store_eeprom      # 0x0D EEPROM (possibly)
  .long ext_store_ignore      # 0x0E Flash ROM/SRAM must be 8bit


ext_store_u32:
  mov %eax, %ecx              # ecx = address
  shr $24, %ecx               # ecx = address >> 24
  cmp $15, %ecx
  ja ext_store_ignore
  # ecx = ext_store_u32_jtable[address >> 24]
  mov ext_store_u32_jtable(, %ecx, 4), %ecx
  jmp *%ecx

# %eax = new_cpsr
# %edx = store_mask

_execute_store_cpsr:
  mov %edx, REG_SAVE(%ebx)        # write out store_mask
  mov %ecx, REG_SAVE2(%ebx)       # write out PC too
  mov %eax, %ecx                  # ecx = new_cpsr
  and %edx, %ecx                  # ecx = new_cpsr & store_mask
  mov REG_CPSR(%ebx), %eax        # eax = cpsr
  not %edx                        # edx = ~store_mask
  and %edx, %eax                  # eax = cpsr & ~store_mask
  or %ecx, %eax                   # eax = new cpsr combined with old
  extract_flags                   # extract flags
  call _execute_store_cpsr_body   # do the dirty work in this C function

  cmp $0, %eax                    # see if return value is 0
  jnz changed_pc_cpsr             # might have changed the PC

  ret                             # return

changed_pc_cpsr:
  add $4, %esp                    # get rid of current return address
  call _block_lookup_address_arm  # lookup new PC
  jmp *%eax

smc_write:
  call _flush_translation_cache_ram

lookup_pc:
  add $4, %esp
  movl $0, CHANGED_PC_STATUS(%ebx)
  mov REG_PC(%ebx), %eax
  testl $0x20, REG_CPSR(%ebx)
  jz lookup_pc_arm

lookup_pc_thumb:
  call _block_lookup_address_thumb
  jmp *%eax

lookup_pc_arm:
  call _block_lookup_address_arm
  jmp *%eax

# eax: cycle counter

_execute_arm_translate:
  movl $_reg, %ebx            # load base register
  extract_flags               # load flag variables
  movl %eax, %edi             # load edi cycle counter

  movl REG_PC(%ebx), %eax     # load PC
  call _block_lookup_address_arm
  jmp *%eax                   # jump to it

_step_debug_x86:
  collapse_flags
#  mov $100, %edi
  mov %edi, %edx
  jmp _step_debug

.comm _memory_map_read 0x8000
.comm _memory_map_write 0x8000
.comm _reg 0x100