Trap Control unit and tests

1 files changed, 192 insertions, 0 deletions

diff --git a/rv64cpu/tb/unit/tb_trap_ctrl.cc b/rv64cpu/tb/unit/tb_trap_ctrl.cc
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+++ b/rv64cpu/tb/unit/tb_trap_ctrl.cc
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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 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, "PageFault_Mcause");
+    check(dut->trap_mtval == 0xBADC0FFEE0ULL, "PageFault_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;
+}