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need to use kernel stack in trap

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This commit is contained in:
folkert van heusden 2022-03-19 18:25:50 +01:00
parent b470d2ad41
commit cf64216ecd
2 changed files with 13 additions and 16 deletions
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25
cpu.cpp
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@ -969,7 +969,7 @@ bool cpu::condition_code_operations(const uint16_t instr)
void cpu::pushStack(const uint16_t v) void cpu::pushStack(const uint16_t v)
{ {
if (getRegister(6) == stackLimitRegister) { if (getRegister(6) == stackLimitRegister) {
printf("stackLimitRegister reached\n"); printf("stackLimitRegister reached\n"); // TODO
exit(1); exit(1);
} }
@ -984,13 +984,6 @@ uint16_t cpu::popStack()
return temp; return temp;
} }
void cpu::switchModeToKernel()
{
int previous_mode = (psw >> 14) & 3;
psw &= 0007777;
psw |= previous_mode << 12;
}
bool cpu::misc_operations(const uint16_t instr) bool cpu::misc_operations(const uint16_t instr)
{ {
switch(instr) { switch(instr) {
@ -1039,7 +1032,6 @@ bool cpu::misc_operations(const uint16_t instr)
if ((instr >> 8) == 0b10001001) { // TRAP if ((instr >> 8) == 0b10001001) { // TRAP
trap(034); trap(034);
switchModeToKernel();
return true; return true;
} }
@ -1089,13 +1081,20 @@ void cpu::busError()
void cpu::trap(const uint16_t vector) void cpu::trap(const uint16_t vector)
{ {
pushStack(getPSW()); uint16_t before_psw = getPSW();
pushStack(getPC()); uint16_t before_pc = getPC();
// switch to kernel mode & update 'previous mode'
uint16_t new_psw = b->readWord(vector + 2) & 0147777; // mask off old 'previous mode'
new_psw |= (before_psw >> 2) & 030000; // apply new 'previous mode'
setPSW(new_psw);
pushStack(before_psw);
pushStack(before_pc);
setPSW(b->readWord(vector + 2));
setPC(b->readWord(vector + 0)); setPC(b->readWord(vector + 0));
D(fprintf(stderr, "TRAP %o: PC is now %06o\n", vector, getPC());) D(fprintf(stderr, "TRAP %o: PC is now %06o, PSW is now %06o\n", vector, getPC(), new_psw);)
} }
std::pair<std::string, int> cpu::addressing_to_string(const uint8_t mode_register, const uint16_t pc) std::pair<std::string, int> cpu::addressing_to_string(const uint8_t mode_register, const uint16_t pc)

2
cpu.h
View file

@ -30,8 +30,6 @@ private:
uint16_t getGAM(const uint8_t mode, const uint8_t reg, const bool word_mode, const bool MF_MT); uint16_t getGAM(const uint8_t mode, const uint8_t reg, const bool word_mode, const bool MF_MT);
void putGAM(const uint8_t mode, const int reg, const bool word_mode, const uint16_t value, const bool MF_FT); void putGAM(const uint8_t mode, const int reg, const bool word_mode, const uint16_t value, const bool MF_FT);
void switchModeToKernel();
bool double_operand_instructions(const uint16_t instr); bool double_operand_instructions(const uint16_t instr);
bool additional_double_operand_instructions(const uint16_t instr); bool additional_double_operand_instructions(const uint16_t instr);
bool single_operand_instructions(const uint16_t instr); bool single_operand_instructions(const uint16_t instr);