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69 lines
2.6 KiB
C
69 lines
2.6 KiB
C
#include <PalmOS.h>
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#include <stdint.h>
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#include "palmGlobalDefines.h"
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#include "specs/hardwareRegisterNames.h"
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#include "specs/emuFeatureRegistersSpec.h"
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enum{
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EMU_STATE_UNTESTED = 0,
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EMU_STATE_FALSE,
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EMU_STATE_TRUE
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};
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/*this handler may not work if the opcode size that triggered the bus error isnt 4 bytes, I am currently depending on the compiler generating a 4 byte opcode for that access*/
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static const uint16_t skipBusError[5] = {
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0x5C8F,/*addq.l #6,sp ; remove error info from stack*/
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0x548F,/*addq.l #2,sp ; remove error info from stack*/
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0x54AF,/*addq.l #2,2(sp) ; skip over the invalid access, what ever was in the variable before the read should still be there*/
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0x0002,/* ; displacement for above*/
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0x4E73/*rte ; return*/
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};
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Boolean isEmulator(){
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static uint8_t emuStatus = EMU_STATE_UNTESTED;
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uint32_t osVer;
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FtrGet(sysFtrCreator, sysFtrNumROMVersion, &osVer);
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if(osVer >= PalmOS50){
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/*writing to interrupt handlers wont work on OS5+*/
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emuStatus = EMU_STATE_FALSE;
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}
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else{
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/*test if first call, else return cached value since testing is intensive*/
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if(emuStatus == EMU_STATE_UNTESTED){
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uint32_t oldBusErrorHandler = readArbitraryMemory32(2 * sizeof(uint32_t));/*EXCEPTION_BUS_ERROR vector*/
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uint8_t oldScr = readArbitraryMemory8(HW_REG_ADDR(SCR));
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volatile uint32_t palmSpecialFeatures;/*must be declared volatile since its modifyed by bus error behavior*/
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writeArbitraryMemory8(HW_REG_ADDR(SCR), 0xF0);/*enable bus error timeout, clear current invalid accesses*/
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writeArbitraryMemory32(2 * sizeof(uint32_t), (uint32_t)skipBusError);/*set EXCEPTION_BUS_ERROR vector*/
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/*set fallback value, will be the returned value if bus error timeout occurs*/
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palmSpecialFeatures = FEATURE_INVALID;
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/*everything is setup, now try to read invalid memory, success == its an emu*/
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palmSpecialFeatures = readArbitraryMemory32(EMU_REG_ADDR(EMU_INFO));
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if(palmSpecialFeatures == FEATURE_INVALID)
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emuStatus = EMU_STATE_FALSE;
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else
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emuStatus = EMU_STATE_TRUE;
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/*restore original state*/
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writeArbitraryMemory8(HW_REG_ADDR(SCR), 0xE0 | oldScr);
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writeArbitraryMemory32(2 * sizeof(uint32_t), oldBusErrorHandler);
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}
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}
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return emuStatus == EMU_STATE_TRUE;
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}
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Boolean isEmulatorFeatureEnabled(uint32_t feature){
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if(isEmulator())
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return (readArbitraryMemory32(EMU_REG_ADDR(EMU_INFO)) & feature) != 0;
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return false;
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}
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