faults.cc

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/*
 * Copyright (c) 2016 RISC-V Foundation
 * Copyright (c) 2016 The University of Virginia
 * Copyright (c) 2018 TU Dresden
 * Copyright (c) 2020 Barkhausen Institut
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
#include "arch/riscv/faults.hh"
 
#include "arch/riscv/insts/static_inst.hh"
#include "arch/riscv/isa.hh"
#include "arch/riscv/mmu.hh"
#include "arch/riscv/pmp.hh"
#include "arch/riscv/regs/misc.hh"
#include "arch/riscv/utility.hh"
#include "cpu/base.hh"
#include "cpu/thread_context.hh"
#include "debug/Faults.hh"
#include "sim/debug.hh"
#include "sim/full_system.hh"
#include "sim/system.hh"
#include "sim/workload.hh"
 
namespace gem5
{
 
namespace RiscvISA
{
 
void
RiscvFault::invokeSE(ThreadContext *tc, const StaticInstPtr &inst)
{
    panic("Fault %s encountered at pc %s.", name(), tc->pcState());
}
 
void
RiscvFault::invoke(ThreadContext *tc, const StaticInstPtr &inst)
{
    auto pc_state = tc->pcState().as<PCState>();
 
    DPRINTFS(Faults, tc->getCpuPtr(), "Fault (%s, %u) at PC: %s\n",
             name(), exception(), pc_state);
 
    if (FullSystem) {
        PrivilegeMode pp = (PrivilegeMode)tc->readMiscReg(MISCREG_PRV);
        PrivilegeMode prv = PRV_M;
        MISA misa = tc->readMiscRegNoEffect(MISCREG_ISA);
        STATUS status = tc->readMiscReg(MISCREG_STATUS);
        NSTATUS nstatus = tc->readMiscReg(MISCREG_MNSTATUS);
        auto* isa = static_cast<RiscvISA::ISA*>(tc->getIsaPtr());
        bool is_rnmi = isResumableNonMaskableInterrupt(isa);
 
        // previous virtualization (H-extension)
        bool pv = misa.rvh ? virtualizationEnabled(tc) : false;
 
        // MISCREG_PRV (mirroring mpp) cannot have PRV_HS == 2
        // it can only be 0 (U), 1 (S), 3 (M).
        // Consult Table 8.8, 8.9 RISCV Privileged Spec V20211203
        if (misa.rvh && pp == PRV_HS) {
            panic("Privilege in MISCREG_PRV is PRV_HS == 2!");
        }
 
        // According to riscv-privileged-v1.11, if a NMI occurs at the middle
        // of a M-mode trap handler, the state (epc/cause) will be overwritten
        // and is not necessary recoverable unless smrnmi enabled.
        warn_if(!isa->enableSmrnmi() && isNonMaskableInterrupt() &&
                pp == PRV_M && status.mie == 0,
                "NMI overwriting M-mode trap handler state");
 
        // Set fault handler privilege mode
        if (isNonMaskableInterrupt()) {
            prv = PRV_M;
        } else if (isInterrupt()) {
            if (pp != PRV_M && misa.rvs &&
                bits(tc->readMiscReg(MISCREG_MIDELEG), _code) != 0) {
                prv = PRV_S;
                // when rvh is true we know rvs is true so prv is S
                if (misa.rvh) {
                    if (virtualizationEnabled(tc) &&
                        bits(tc->readMiscReg(MISCREG_HIDELEG), _code) == 0) {
                        resetV(tc); // No delegation, go to HS (S with V = 0)
                    }
                    // otherwise handled in VS (S with V = 1)
                }
            }
        } else {
            if (pp != PRV_M && misa.rvs &&
                bits(tc->readMiscReg(MISCREG_MEDELEG), _code) != 0) {
                prv = PRV_S;
 
                // when rvh is true we know rvs is true so prv is S
                if (misa.rvh) {
                    if (virtualizationEnabled(tc) &&
                        bits(tc->readMiscReg(MISCREG_HEDELEG), _code) == 0) {
                        resetV(tc); // No delegation, go to HS (S with V = 0)
                    }
                    // otherwise handled in VS (S with V = 1)
                }
            }
        }
 
        // Set fault registers and status
        MiscRegIndex cause, epc, tvec, tval;
        switch (prv) {
          case PRV_U:
            panic("Delegating interrupt to user mode is removed.");
            break;
          case PRV_S:
            cause = MISCREG_SCAUSE;
            epc = MISCREG_SEPC;
            tvec = MISCREG_STVEC;
            tval = MISCREG_STVAL;
 
            status.spp = pp;
            status.spie = status.sie;
            status.sie = 0;
            break;
          case PRV_M:
            cause = is_rnmi ? MISCREG_MNCAUSE : MISCREG_MCAUSE;
            epc = is_rnmi ? MISCREG_MNEPC : MISCREG_MEPC;
            tvec = isNonMaskableInterrupt() ? MISCREG_NMIVEC : MISCREG_MTVEC;
            tval = MISCREG_MTVAL;
 
            if (is_rnmi) {
                nstatus.mnpp = pp;
            } else {
                status.mpp = pp;
                status.mpie = status.mie;
                status.mie = 0;
            }
            break;
          default:
            panic("Unknown privilege mode %d.", prv);
            break;
        }
 
        // H-extension extra handling for invoke
        if (misa.rvh) {
            if (prv == PRV_M) {
                status.mpv = pv;
                status.gva = mustSetGva();
                // Paragraph 8.5.2 RISCV Privileged Spec 20211203
                if (isGuestPageFault()) {
                    tc->setMiscReg(MISCREG_MTVAL2, trap_value() >> 2);
                }
                // Going to M-mode for handling, disable V if it's on
                if (virtualizationEnabled(tc)) { resetV(tc); }
            } else if (prv == PRV_S &&
                    !virtualizationEnabled(tc)) { // essentially HS-mode
                HSTATUS hstatus = tc->readMiscReg(MISCREG_HSTATUS);
                hstatus.spv = pv;
                if (pv) { // if V-bit was on
                    hstatus.spvp = status.spp;
                    hstatus.gva = mustSetGva();
                    // Paragraph 8.5.2 RISCV Privileged Spec 20211203
                    if (isGuestPageFault()) {
                        tc->setMiscReg(MISCREG_HTVAL, trap_value2());
                    }
                }
                // Write changes to hstatus
                tc->setMiscReg(MISCREG_HSTATUS, hstatus);
            } else if (prv == PRV_S &&
                    virtualizationEnabled(tc)) { // essentially VS-mode
                STATUS vsstatus = tc->readMiscReg(MISCREG_VSSTATUS);
                cause = MISCREG_VSCAUSE;
                epc = MISCREG_VSEPC;
                tvec = MISCREG_VSTVEC;
                tval = MISCREG_VSTVAL;
                vsstatus.spp = pp;
                vsstatus.spie = vsstatus.sie;
                vsstatus.sie = 0;
                tc->setMiscReg(MISCREG_VSSTATUS, vsstatus);
 
                // Paragraph 8.2.2 RISCV Privileged Spec 20211203
                switch (_code) {
                    case INT_SOFTWARE_VIRTUAL_SUPER:
                        _code = INT_SOFTWARE_SUPER;
                        break;
                    case INT_TIMER_VIRTUAL_SUPER:
                        _code = INT_TIMER_SUPER;
                        break;
                    case INT_EXT_VIRTUAL_SUPER:
                        _code = INT_EXT_SUPER;
                        break;
                    default:
                        break;
                }
            } else {
                panic("Unknown case in hypervisor fault handler."
                      "prv = %d, V = %d", prv, virtualizationEnabled(tc));
            }
        }
 
        // Set fault cause, privilege, and return PC
        uint64_t _cause = _code;
        if (isInterrupt()) {
           _cause |= CAUSE_INTERRUPT_MASKS[pc_state.rvType()];
        }
        tc->setMiscReg(cause, _cause);
        if (pc_state.zcmtSecondFetch()) {
            tc->setMiscReg(epc, pc_state.zcmtPc());
        } else {
            tc->setMiscReg(epc, pc_state.instAddr());
        }
        tc->setMiscReg(tval, trap_value());
        tc->setMiscReg(MISCREG_PRV, prv);
        if (is_rnmi) {
            tc->setMiscReg(MISCREG_MNSTATUS, nstatus);
        } else {
            tc->setMiscReg(MISCREG_STATUS, status);
        }
        // Temporarily mask NMI while we're in NMI handler. Otherweise, the
        // checkNonMaskableInterrupt will always return true and we'll be
        // stucked in an infinite loop.
        if (isNonMaskableInterrupt()) {
            tc->setMiscReg(MISCREG_NMIE, 0);
        }
 
        // Clear load reservation address
        isa->clearLoadReservation(tc->contextId());
 
        // Set PC to fault handler address
        Addr addr = isa->getFaultHandlerAddr(tvec, _code, isInterrupt());
        if (pc_state.zcmtSecondFetch()) {
            pc_state.zcmtSecondFetch(false);
            pc_state.zcmtPc(0);
        }
        pc_state.set(isa->rvSext(addr));
        tc->pcState(pc_state);
    } else {
        invokeSE(tc, inst);
    }
}
 
void
Reset::invoke(ThreadContext *tc, const StaticInstPtr &inst)
{
    tc->setMiscReg(MISCREG_PRV, PRV_M);
    STATUS status = tc->readMiscReg(MISCREG_STATUS);
    status.mie = 0;
    status.mprv = 0;
    tc->setMiscReg(MISCREG_STATUS, status);
    tc->setMiscReg(MISCREG_MCAUSE, 0);
 
    // Advance the PC to the implementation-defined reset vector
    auto workload = dynamic_cast<Workload *>(tc->getSystemPtr()->workload);
    std::unique_ptr<PCState> new_pc(dynamic_cast<PCState *>(
        tc->getIsaPtr()->newPCState(workload->getEntry())));
    panic_if(!new_pc, "Failed create new PCState from ISA pointer");
    VTYPE vtype = 0;
    vtype.vill = 1;
    new_pc->vtype(vtype);
    new_pc->vl(0);
    tc->pcState(*new_pc);
 
    auto* mmu = tc->getMMUPtr();
    if (mmu != nullptr) {
        mmu->reset();
    }
}
 
void
UnknownInstFault::invokeSE(ThreadContext *tc, const StaticInstPtr &inst)
{
    auto *rsi = static_cast<RiscvStaticInst *>(inst.get());
    panic("Unknown instruction 0x%08x at pc %s", rsi->machInst,
        tc->pcState());
}
 
void
IllegalInstFault::invokeSE(ThreadContext *tc, const StaticInstPtr &inst)
{
    if (! tc->getSystemPtr()->trapToGdb(GDBSignal::ILL, tc->contextId()) ) {
        auto *rsi = static_cast<RiscvStaticInst *>(inst.get());
        panic("Illegal instruction 0x%08x at pc %s: %s", rsi->machInst,
            tc->pcState(), reason.c_str());
    }
}
 
void
UnimplementedFault::invokeSE(ThreadContext *tc, const StaticInstPtr &inst)
{
    panic("Unimplemented instruction %s at pc %s", instName, tc->pcState());
}
 
void
IllegalFrmFault::invokeSE(ThreadContext *tc, const StaticInstPtr &inst)
{
    panic("Illegal floating-point rounding mode 0x%x at pc %s.",
            frm, tc->pcState());
}
 
void
BreakpointFault::invokeSE(ThreadContext *tc, const StaticInstPtr &inst)
{
    if (! tc->getSystemPtr()->trapToGdb(GDBSignal::TRAP, tc->contextId()) ) {
        schedRelBreak(0);
    }
}
 
void
SyscallFault::invokeSE(ThreadContext *tc, const StaticInstPtr &inst)
{
    /* Advance the PC to next instruction so - once (simulated) syscall
       is executed - execution continues. */
    auto pc_state = tc->pcState().as<PCState>();
    inst->advancePC(pc_state);
    tc->pcState(pc_state);
 
    tc->getSystemPtr()->workload->syscall(tc);
}
 
bool
getFaultVAddr(Fault fault, Addr &va)
{
    auto addr_fault = dynamic_cast<AddressFault *>(fault.get());
    if (addr_fault) {
        va = addr_fault->trap_value();
        return true;
    }
 
    auto pgt_fault = dynamic_cast<GenericPageTableFault *>(fault.get());
    if (pgt_fault) {
        va = pgt_fault->getFaultVAddr();
        return true;
    }
 
    return false;
}
 
} // namespace RiscvISA
} // namespace gem5