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// Richard CPU
// Copyright (C) 2026 Richard Qin
//
// This program 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.
//
// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
// File path: tb/unit/tb_trap_ctrl.cc
// Description: Standalone unit test for trap_ctrl exception/interrupt control logic
#include <cassert>
#include <cstdint>
#include <iostream>
#include <verilated.h>
#include "Vtrap_ctrl.h"
namespace {
constexpr uint64_t EXC_INST_ILLEGAL = 2ULL;
constexpr uint64_t EXC_ECALL_FROM_S = 9ULL;
constexpr uint64_t EXC_LOAD_PAGE_FAULT= 13ULL;
constexpr uint64_t EXC_STORE_PAGE_FAULT= 15ULL;
constexpr uint64_t EXC_LOAD_FAULT = 5ULL;
constexpr uint64_t EXC_STORE_FAULT = 7ULL;
constexpr uint64_t INT_M_SOFTWARE = 3ULL;
constexpr uint64_t INT_M_TIMER = 7ULL;
constexpr uint64_t INT_M_EXTERNAL = 11ULL;
constexpr uint64_t INTERRUPT_BIT = 1ULL << 63;
constexpr uint64_t PRIV_MODE_U = 0ULL;
constexpr uint64_t PRIV_MODE_S = 1ULL;
constexpr uint64_t PRIV_MODE_M = 3ULL;
void drive_defaults(Vtrap_ctrl* dut) {
dut->wb_pc = 0;
dut->trap_illegal_instr = 0;
dut->trap_is_ecall = 0;
dut->trap_is_ebreak = 0;
dut->trap_is_mret = 0;
dut->trap_is_sret = 0;
dut->trap_load_fault = 0;
dut->trap_store_fault = 0;
dut->trap_instr_page_fault = 0;
dut->trap_load_page_fault = 0;
dut->trap_store_page_fault = 0;
dut->trap_bad_addr = 0;
dut->trap_bad_instr = 0;
dut->ext_timer_int = 0;
dut->ext_software_int = 0;
dut->ext_external_int = 0;
dut->csr_mstatus_mie = 0;
dut->csr_mtvec = 0x800ULL;
dut->csr_stvec = 0x400ULL;
dut->csr_mepc = 0x1000ULL;
dut->csr_sepc = 0x2000ULL;
dut->csr_medeleg = 0ULL;
dut->csr_mideleg = 0ULL;
dut->csr_priv_mode = PRIV_MODE_M;
dut->eval();
}
int pass_count = 0;
void check(bool cond, const char* name) {
if (cond) {
std::cout << "\033[32m[PASS] " << name << "\033[0m" << std::endl;
pass_count++;
} else {
std::cout << "\033[31m[FAIL] " << name << "\033[0m" << std::endl;
assert(false);
}
}
} // namespace
int main(int argc, char** argv) {
Verilated::commandArgs(argc, argv);
Vtrap_ctrl* dut = new Vtrap_ctrl;
std::cout << "----------------------------------\n";
std::cout << " trap_ctrl Testbench\n";
std::cout << "----------------------------------\n";
// ---------------------------------------------------------------------
// 1) Synchronous exceptions (illegal instruction, ecall, page fault)
// ---------------------------------------------------------------------
drive_defaults(dut);
dut->csr_priv_mode = PRIV_MODE_M;
dut->csr_mtvec = 0x880ULL;
dut->wb_pc = 0x1234ULL;
dut->trap_bad_instr = 0xDEADBEEFu;
dut->trap_illegal_instr = 1;
dut->eval();
check(dut->trap_trigger, "IllegalInst_TriggersTrap");
check(dut->trap_mcause == EXC_INST_ILLEGAL, "IllegalInst_Mcause");
check(dut->trap_mtval == 0xDEADBEEFULL, "IllegalInst_Mtval");
check(dut->trap_mepc == 0x1234ULL, "IllegalInst_Mepc");
check(!dut->trap_to_s_mode, "IllegalInst_NoDelegation");
check(dut->trap_next_pc == 0x880ULL, "IllegalInst_JumpsToMtvec");
drive_defaults(dut);
dut->csr_priv_mode = PRIV_MODE_S;
dut->csr_mtvec = 0x440ULL;
dut->wb_pc = 0x5678ULL;
dut->trap_is_ecall = 1;
dut->eval();
check(dut->trap_trigger, "EcallS_TriggersTrap");
check(dut->trap_mcause == EXC_ECALL_FROM_S, "EcallS_Mcause");
check(dut->trap_mtval == 0ULL, "EcallS_MtvalZero");
check(dut->trap_next_pc == 0x440ULL, "EcallS_JumpsToMtvec");
drive_defaults(dut);
dut->trap_load_page_fault = 1;
dut->trap_bad_addr = 0xBADC0FFEE0ULL;
dut->eval();
check(dut->trap_mcause == EXC_LOAD_PAGE_FAULT, "LoadPageFault_Mcause");
check(dut->trap_mtval == 0xBADC0FFEE0ULL, "LoadPageFault_Mtval");
drive_defaults(dut);
dut->trap_store_page_fault = 1;
dut->trap_bad_addr = 0xDEADBEEF00ULL;
dut->eval();
check(dut->trap_mcause == EXC_STORE_PAGE_FAULT, "StorePageFault_Mcause");
check(dut->trap_mtval == 0xDEADBEEF00ULL, "StorePageFault_Mtval");
drive_defaults(dut);
dut->trap_load_fault = 1;
dut->trap_bad_addr = 0xABCDEF0010ULL;
dut->eval();
check(dut->trap_mcause == EXC_LOAD_FAULT, "LoadFault_Mcause");
check(dut->trap_mtval == 0xABCDEF0010ULL, "LoadFault_Mtval");
drive_defaults(dut);
dut->trap_store_fault = 1;
dut->trap_bad_addr = 0xABCDEF0020ULL;
dut->eval();
check(dut->trap_mcause == EXC_STORE_FAULT, "StoreFault_Mcause");
check(dut->trap_mtval == 0xABCDEF0020ULL, "StoreFault_Mtval");
// ---------------------------------------------------------------------
// 2) Interrupt priority + delegation to supervisor
// ---------------------------------------------------------------------
drive_defaults(dut);
dut->csr_mstatus_mie = 1;
dut->csr_priv_mode = PRIV_MODE_M;
dut->csr_mtvec = 0x300ULL | 0x1ULL; // vectored mode
dut->wb_pc = 0x4000ULL;
dut->ext_timer_int = 1;
dut->ext_software_int = 1;
dut->ext_external_int = 1;
dut->eval();
const uint64_t expected_vectored_pc = 0x300ULL + (INT_M_EXTERNAL << 2);
check(dut->trap_trigger, "InterruptPriority_Triggers");
check(dut->trap_mcause == (INTERRUPT_BIT | INT_M_EXTERNAL), "InterruptPriority_Mcause");
check(dut->trap_mtval == 0ULL, "InterruptPriority_MtvalZero");
check(dut->trap_next_pc == expected_vectored_pc, "InterruptPriority_VectoredJump");
drive_defaults(dut);
dut->csr_mstatus_mie = 0;
dut->ext_external_int = 1;
dut->eval();
check(!dut->trap_trigger, "InterruptMasked_NoTrigger");
drive_defaults(dut);
dut->csr_priv_mode = PRIV_MODE_S;
dut->csr_mstatus_mie = 1;
dut->csr_stvec = 0x880ULL | 0x1ULL; // vectored supervisor mode
dut->csr_mideleg = (1ULL << INT_M_TIMER);
dut->wb_pc = 0xABCDULL;
dut->ext_timer_int = 1;
dut->eval();
const uint64_t expected_sv_pc = 0x880ULL + (INT_M_TIMER << 2);
check(dut->trap_to_s_mode, "InterruptDelegation_ToSupervisor");
check(dut->trap_next_pc == expected_sv_pc, "InterruptDelegation_UsesStvec");
check(dut->trap_mcause == (INTERRUPT_BIT | INT_M_TIMER), "InterruptDelegation_Mcause");
// ---------------------------------------------------------------------
// 3) MRET/SRET redirect without new traps
// ---------------------------------------------------------------------
drive_defaults(dut);
dut->csr_mepc = 0xCAFEBABEULL;
dut->trap_is_mret = 1;
dut->eval();
check(dut->mret_en, "Mret_PathEnabled");
check(dut->trap_next_pc == 0xCAFEBABEULL, "Mret_RestoresMepc");
check(dut->trap_flush_req && dut->trap_pc_sel, "Mret_ForcesFlush");
check(!dut->trap_trigger, "Mret_NoTrapOverlap");
drive_defaults(dut);
dut->csr_priv_mode = PRIV_MODE_S;
dut->csr_sepc = 0x13579BDFULL;
dut->trap_is_sret = 1;
dut->eval();
check(dut->sret_en, "Sret_PathEnabled");
check(dut->trap_next_pc == 0x13579BDFULL, "Sret_RestoresSepc");
check(dut->trap_flush_req && dut->trap_pc_sel, "Sret_ForcesFlush");
std::cout << "----------------------------------\n";
std::cout << "All " << pass_count << " trap_ctrl tests passed!\n";
std::cout << "----------------------------------\n";
delete dut;
return 0;
}
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