fix MPP reset value, PMP inactive in U-mode handling and MRET in U-mode

incl/iss/arch/riscv_hart_msu_vp.h

@@ -145,7 +145,7 @@ public:
 
         mstatus_t mstatus;
 
-        static const reg_t mstatus_reset_val = 0;
+        static const reg_t mstatus_reset_val = 0x1800;
 
         void write_mstatus(T val, unsigned priv_lvl) {
             auto mask = get_mask(priv_lvl);
@@ -398,7 +398,7 @@ private:
     iss::status read_ip(unsigned addr, reg_t &val);
     iss::status write_ip(unsigned addr, reg_t val);
     iss::status read_hartid(unsigned addr, reg_t &val);
-    iss::status write_mepc(unsigned addr, reg_t val);
+    iss::status write_epc(unsigned addr, reg_t val);
     iss::status read_satp(unsigned addr, reg_t &val);
     iss::status write_satp(unsigned addr, reg_t val);
     iss::status read_fcsr(unsigned addr, reg_t &val);
@@ -954,8 +954,8 @@ template <typename BASE> iss::status riscv_hart_msu_vp<BASE>::write_ip(unsigned
     return iss::Ok;
 }
 
-template <typename BASE> iss::status riscv_hart_m_p<BASE>::write_epc(unsigned addr, reg_t val) {
-     csr[addr] = val & get_pc_mask();
+template <typename BASE> iss::status riscv_hart_msu_vp<BASE>::write_epc(unsigned addr, reg_t val) {
+    csr[addr] = val & get_pc_mask();
     return iss::Ok;
 }
 

incl/iss/arch/riscv_hart_mu_p.h

@@ -146,7 +146,7 @@ public:
 
         mstatus_t mstatus;
 
-        static const reg_t mstatus_reset_val = 0;
+        static const reg_t mstatus_reset_val = 0x1800; // MPP set to 1
 
         void write_mstatus(T val, unsigned priv_lvl) {
             auto mask = get_mask(priv_lvl);
@@ -543,25 +543,27 @@ template <typename BASE, features_e FEAT> bool riscv_hart_mu_p<BASE, FEAT>::pmp_
     constexpr auto PMP_NA4 =0x2U;
     constexpr auto PMP_NAPOT =0x3U;
     reg_t base = 0;
+    auto any_active = false;
     for (size_t i = 0; i < 16; i++) {
         reg_t tor = csr[pmpaddr0+i] << PMP_SHIFT;
         uint8_t cfg = csr[pmpcfg0+(i/4)]>>(i%4);
         if (cfg & PMP_A) {
+            any_active=true;
             auto pmp_a = (cfg & PMP_A) >> 3;
-            bool is_tor = pmp_a == PMP_TOR;
-            bool is_na4 = pmp_a == PMP_NA4;
+            auto is_tor = pmp_a == PMP_TOR;
+            auto is_na4 = pmp_a == PMP_NA4;
 
             reg_t mask = (csr[pmpaddr0+i] << 1) | (!is_na4);
             mask = ~(mask & ~(mask + 1)) << PMP_SHIFT;
 
             // Check each 4-byte sector of the access
-            bool any_match = false;
-            bool all_match = true;
+            auto any_match = false;
+            auto all_match = true;
             for (reg_t offset = 0; offset < len; offset += 1 << PMP_SHIFT) {
                 reg_t cur_addr = addr + offset;
-                bool napot_match = ((cur_addr ^ tor) & mask) == 0;
-                bool tor_match = base <= cur_addr && cur_addr < tor;
-                bool match = is_tor ? tor_match : napot_match;
+                auto napot_match = ((cur_addr ^ tor) & mask) == 0;
+                auto tor_match = base <= cur_addr && cur_addr < tor;
+                auto match = is_tor ? tor_match : napot_match;
                 any_match |= match;
                 all_match &= match;
             }
@@ -577,7 +579,7 @@ template <typename BASE, features_e FEAT> bool riscv_hart_mu_p<BASE, FEAT>::pmp_
         }
         base = tor;
     }
-    return this->reg.PRIV == PRIV_M;
+    return !any_active || this->reg.PRIV == PRIV_M;
 }
 
 
@@ -926,8 +928,6 @@ template <typename BASE, features_e FEAT> iss::status riscv_hart_mu_p<BASE, FEAT
 
 template <typename BASE, features_e FEAT> iss::status riscv_hart_mu_p<BASE, FEAT>::write_ie(unsigned addr, reg_t val) {
     auto mask = get_irq_wrmask((addr >> 8) & 0x3);
-    if(this->reg.PRIV==0)
-        mask&= ~(0xff<<4); // STIE and UTIE are read only in user and supervisor mode
     csr[mie] = (csr[mie] & ~mask) | (val & mask);
     check_interrupt();
     return iss::Ok;
@@ -1256,27 +1256,33 @@ template <typename BASE, features_e FEAT> uint64_t riscv_hart_mu_p<BASE, FEAT>::
 template <typename BASE, features_e FEAT> uint64_t riscv_hart_mu_p<BASE, FEAT>::leave_trap(uint64_t flags) {
     auto cur_priv = this->reg.PRIV;
     auto inst_priv = (flags & 0x3)? 3:0;
-    auto status = state.mstatus;
-    // pop the relevant lower-privilege interrupt enable and privilege mode stack
-    // clear respective yIE
-    switch (inst_priv) {
-    case PRIV_M:
-        this->reg.PRIV = state.mstatus.MPP;
-        state.mstatus.MPP = 0; // clear mpp to U mode
-        state.mstatus.MIE = state.mstatus.MPIE;
-        state.mstatus.MPIE = 1;
-        break;
-    case PRIV_U:
-        this->reg.PRIV = 0;
-        state.mstatus.UIE = state.mstatus.UPIE;
-        state.mstatus.UPIE = 1;
-        break;
+    if(inst_priv>cur_priv){
+        auto trap_val =  0x80ULL << 24 | (2 << 16); // illegal instruction
+        this->reg.trap_state = trap_val;
+        this->reg.NEXT_PC = std::numeric_limits<uint32_t>::max();
+    } else {
+        auto status = state.mstatus;
+        // pop the relevant lower-privilege interrupt enable and privilege mode stack
+        // clear respective yIE
+        switch (inst_priv) {
+        case PRIV_M:
+            this->reg.PRIV = state.mstatus.MPP;
+            state.mstatus.MPP = 0; // clear mpp to U mode
+            state.mstatus.MIE = state.mstatus.MPIE;
+            state.mstatus.MPIE = 1;
+            break;
+        case PRIV_U:
+            this->reg.PRIV = 0;
+            state.mstatus.UIE = state.mstatus.UPIE;
+            state.mstatus.UPIE = 1;
+            break;
+        }
+        // sets the pc to the value stored in the x epc register.
+        this->reg.NEXT_PC = csr[uepc | inst_priv << 8];
+        CLOG(INFO, disass) << "Executing xRET , changing privilege level from " << lvl[cur_priv] << " to "
+                           << lvl[this->reg.PRIV];
+        check_interrupt();
     }
-    // sets the pc to the value stored in the x epc register.
-    this->reg.NEXT_PC = csr[uepc | inst_priv << 8];
-    CLOG(INFO, disass) << "Executing xRET , changing privilege level from " << lvl[cur_priv] << " to "
-                       << lvl[this->reg.PRIV];
-    check_interrupt();
     return this->reg.NEXT_PC;
 }