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8237: Track DMA transfer mode (from mode byte) and enforce read/write direction. You cannot READ from DMA configured for WRITING, etc

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This commit is contained in:
Jonathan Campbell 2019-05-26 20:57:04 -07:00
parent 4ac39236b7
commit cd872be4dd
2 changed files with 18 additions and 4 deletions
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7
include/dma.h
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@ -28,6 +28,12 @@ enum DMAEvent {
DMA_TRANSFEREND
};
enum DMATransfer {
DMAT_VERIFY=0,
DMAT_WRITE=1,
DMAT_READ=2
};
class DmaChannel;
typedef void (* DMA_CallBack)(DmaChannel * chan,DMAEvent event);
@ -43,6 +49,7 @@ public:
Bit8u DMA16_PAGESHIFT;
Bit32u DMA16_ADDRMASK;
Bit8u DMA16;
Bit8u transfer_mode;
bool increment;
bool autoinit;
bool masked;

15
src/hardware/dma.cpp
View File

@ -297,6 +297,7 @@ void DmaController::WriteControllerReg(Bitu reg,Bitu val,Bitu /*len*/) {
chan=GetChannel(val & 3);
chan->autoinit=(val & 0x10) > 0;
chan->increment=(!allow_decrement_mode) || ((val & 0x20) == 0); /* 0=increment 1=decrement */
chan->transfer_mode=((val >> 2) & 3);
//TODO Maybe other bits? Like bits 6-7 to select demand/single/block/cascade mode? */
break;
case 0xc: /* Clear Flip/Flip */
@ -402,8 +403,11 @@ Bitu DmaChannel::Read(Bitu want, Bit8u * buffer) {
LOG(LOG_DMACONTROL,LOG_WARN)("BUG: Attempted DMA channel read while channel masked");
return 0;
}
/* TODO: Reject Read() if DMA mode byte was programmed in any mode other than read */
/* You cannot read a DMA channel configured for writing (to memory) */
if (transfer_mode != DMAT_READ) {
LOG(LOG_DMACONTROL,LOG_WARN)("BUG: Attempted DMA channel write when DMA channel is configured by guest for reading (from memory)");
return 0;
}
/* WARNING: "want" is expressed in DMA transfer units.
* For 8-bit DMA, want is in bytes.
@ -473,8 +477,11 @@ Bitu DmaChannel::Write(Bitu want, Bit8u * buffer) {
LOG(LOG_DMACONTROL,LOG_WARN)("BUG: Attempted DMA channel write while channel masked");
return 0;
}
/* TODO: Reject Write() if DMA mode byte was programmed in any mode other than write */
/* You cannot write a DMA channel configured for reading (from memory) */
if (transfer_mode != DMAT_WRITE) {
LOG(LOG_DMACONTROL,LOG_WARN)("BUG: Attempted DMA channel read when DMA channel is configured by guest for writing (to memory)");
return 0;
}
/* WARNING: "want" is expressed in DMA transfer units.
* For 8-bit DMA, want is in bytes.