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deeppoke.go
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deeppoke.go
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// This file is part of Gopher2600.
//
// Gopher2600 is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Gopher2600 is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Gopher2600. If not, see <https://www.gnu.org/licenses/>.
package debugger
import (
"fmt"
"github.com/jetsetilly/gopher2600/debugger/govern"
"github.com/jetsetilly/gopher2600/hardware/cpu/instructions"
"github.com/jetsetilly/gopher2600/hardware/cpu/registers"
"github.com/jetsetilly/gopher2600/hardware/memory"
"github.com/jetsetilly/gopher2600/hardware/memory/memorymap"
"github.com/jetsetilly/gopher2600/logger"
"github.com/jetsetilly/gopher2600/rewind"
)
// PushDeepPoke schedules a deep poke search for the specificed value in the
// address, replacing it with newValue if found. The valueMask will be applied
// to the value for matching and for setting the newValue - unset bits in the
// mask will preserve the corresponding bits in the found value.
func (dbg *Debugger) PushDeepPoke(addr uint16, value uint8, newValue uint8, valueMask uint8, done func()) bool {
// get current state to use as the resume state after the deeppoke and rewind recovery
searchState := dbg.Rewind.GetCurrentState()
doDeepPoke := func() error {
err := dbg.doDeepPoke(searchState, addr, value, newValue, valueMask)
if err != nil {
logger.Logf("deeppoke", "%v", err)
}
if done != nil {
done()
}
return nil
}
dbg.PushFunctionImmediate(func() {
dbg.setStateQuiet(govern.Rewinding, true)
dbg.unwindLoop(doDeepPoke)
})
return true
}
// returned by searchDeepPoke() for convenience.
type deepPoking struct {
state *rewind.State
addr uint16
area memorymap.Area
}
func (dbg *Debugger) doDeepPoke(searchState *rewind.State, addr uint16, value uint8, newValue uint8, valueMask uint8) error {
poking, err := dbg.searchDeepPoke(searchState, addr, value, valueMask)
if err != nil {
return err
}
if poking.state == nil {
return nil
}
switch poking.area {
case memorymap.RAM:
// poking RAM requires a rewind.PokeHook. this is so we can poke
// the new value at the correct point rather than from the resume
// state.
pokeHook := func(s *rewind.State) error {
return deepPoke(s.Mem, poking, newValue, valueMask)
}
// run from found poking.state to the "current state" in the real emulation
err = dbg.Rewind.RunPoke(poking.state, searchState, pokeHook)
if err != nil {
return err
}
case memorymap.Cartridge:
// if we're not poking RAM then we poke the state that we found
// immediately. this is particulatly important for cartridges with
// multiple banks because we need to poke the bank we found.
err := deepPoke(poking.state.Mem, poking, newValue, valueMask)
if err != nil {
return err
}
// run from found poking.state to the "current state" in the real emulation
err = dbg.Rewind.RunPoke(poking.state, searchState, nil)
if err != nil {
return err
}
}
return nil
}
// searchDeepPoke looks for the literal value that is being poked into the quoted
// address. Once found the newValue is poked in appropriately.
//
// The valueMask is used during the rewind history search to help decide if the
// value being written matches the value we're looking for. See SearchMemoryWrite()
// and SearchRegisterWrite() in the rewind package.
func (dbg *Debugger) searchDeepPoke(searchState *rewind.State, searchAddr uint16, value uint8, valueMask uint8) (deepPoking, error) {
var poking deepPoking
var err error
const maxSearchDepth = 10
// trace memory write as far back as we can
for depth := 0; depth < maxSearchDepth; depth++ {
searchState, err = dbg.Rewind.SearchMemoryWrite(searchState, searchAddr, value, valueMask)
if err != nil {
return deepPoking{}, err
}
if searchState == nil {
return poking, nil
}
// writes to memory always use a register as the source of the write
var reg rune
switch searchState.CPU.LastResult.Defn.Operator {
case instructions.Sta:
reg = 'A'
case instructions.Stx:
reg = 'X'
case instructions.Sty:
reg = 'Y'
default:
return deepPoking{}, fmt.Errorf("unexpected write sequence (%s)", searchState.CPU.LastResult.String())
}
searchState, err = dbg.Rewind.SearchRegisterWrite(searchState, reg, value, valueMask)
if err != nil {
return deepPoking{}, err
}
if searchState == nil {
return poking, nil
}
// writes to a register can happen from another register, and immediate
// value, or an address in memory (most probably from the cartridge or
// VCS RAM)
switch searchState.CPU.LastResult.Defn.AddressingMode {
case instructions.Immediate:
ma, area := memorymap.MapAddress(searchState.CPU.LastResult.Address, false)
switch area {
case memorymap.Cartridge:
pc := registers.NewProgramCounter(ma)
pc.Add(1)
poking.addr = pc.Address()
poking.state = searchState
poking.area = area
return poking, nil
default:
return deepPoking{}, fmt.Errorf("not deeppoking through non-RAM/Cartridge space (%s)", area)
}
case instructions.AbsoluteIndexedX:
ma, area := memorymap.MapAddress(searchState.CPU.LastResult.InstructionData, false)
switch area {
case memorymap.Cartridge:
pc := registers.NewProgramCounter(ma)
pc.Add(searchState.CPU.X.Address())
poking.addr = pc.Address()
poking.state = searchState
poking.area = area
return poking, nil
case memorymap.RAM:
pc := registers.NewProgramCounter(ma)
pc.Add(searchState.CPU.X.Address())
poking.addr = pc.Address()
poking.state = searchState
poking.area = area
default:
return deepPoking{}, fmt.Errorf("not deeppoking through non-RAM/Cartridge space (%s)", area)
}
case instructions.AbsoluteIndexedY:
ma, area := memorymap.MapAddress(searchState.CPU.LastResult.InstructionData, false)
switch area {
case memorymap.Cartridge:
pc := registers.NewProgramCounter(ma)
pc.Add(searchState.CPU.Y.Address())
poking.addr = pc.Address()
poking.state = searchState
poking.area = area
return poking, nil
case memorymap.RAM:
pc := registers.NewProgramCounter(ma)
pc.Add(searchState.CPU.Y.Address())
poking.addr = pc.Address()
poking.state = searchState
poking.area = area
default:
return deepPoking{}, fmt.Errorf("not deeppoking through non-RAM/Cartridge space (%s)", area)
}
case instructions.ZeroPage:
ma, area := memorymap.MapAddress(searchState.CPU.LastResult.InstructionData, false)
switch area {
case memorymap.RAM:
poking.addr = ma
poking.state = searchState
poking.area = area
// update the search address and continue with the search
searchAddr = poking.addr
default:
return deepPoking{}, fmt.Errorf("not deeppoking through non-RAM space (%s)", area)
}
case instructions.ZeroPageIndexedX:
ma, area := memorymap.MapAddress(searchState.CPU.LastResult.InstructionData, false)
switch area {
case memorymap.RAM:
pc := registers.NewProgramCounter(ma)
pc.Add(searchState.CPU.X.Address())
poking.addr = pc.Address()
poking.state = searchState
poking.area = area
// update the search address and continue with the search
searchAddr = poking.addr
default:
return deepPoking{}, fmt.Errorf("not deeppoking through non-RAM space (%s)", area)
}
case instructions.ZeroPageIndexedY:
ma, area := memorymap.MapAddress(searchState.CPU.LastResult.InstructionData, false)
switch area {
case memorymap.RAM:
pc := registers.NewProgramCounter(ma)
pc.Add(searchState.CPU.Y.Address())
poking.addr = pc.Address()
poking.state = searchState
poking.area = area
// update the search address and continue with the search
searchAddr = poking.addr
default:
return deepPoking{}, fmt.Errorf("not deeppoking through non-RAM space (%s)", area)
}
case instructions.IndirectIndexed:
pc := registers.NewProgramCounter(searchState.CPU.LastResult.InstructionData)
lo, err := searchState.Mem.Read(pc.Address())
if err != nil {
return deepPoking{}, err
}
pc.Add(1)
hi, err := searchState.Mem.Read(pc.Address())
if err != nil {
return deepPoking{}, err
}
pc.Load((uint16(hi) << 8) | uint16(lo))
pc.Add(searchState.CPU.Y.Address())
ma, area := memorymap.MapAddress(pc.Address(), false)
switch area {
case memorymap.Cartridge:
poking.addr = ma
poking.state = searchState
poking.area = area
return poking, nil
case memorymap.RAM:
poking.addr = ma
poking.state = searchState
poking.area = area
default:
return deepPoking{}, fmt.Errorf("not deeppoking through non-RAM/Cartridge space (%s)", area)
}
fallthrough
default:
return deepPoking{}, fmt.Errorf("unsupported addressing mode (%s)", searchState.CPU.LastResult.String())
}
}
return deepPoking{}, fmt.Errorf("deeppoking too deep")
}
// deepPoke changes the bits at the address according the value of valueMask.
func deepPoke(mem *memory.Memory, poke deepPoking, value uint8, valueMask uint8) error {
v, err := mem.Peek(poke.addr)
if err != nil {
return err
}
v = (v & (valueMask ^ 0xff)) | (value & valueMask)
logger.Log("deeppoke", fmt.Sprintf("changing %#04x (%s) to %#02x", poke.addr, poke.area, value))
return mem.Poke(poke.addr, v)
}