Only implement one solution for native triggers.

When S-mode is present, use option 1 (disable triggers in M-mode unless
MIE is set) from the Debug Spec. When S-mode is not present, use option
2 (implement mte and mpte bits in tcontrol).

See discussion in #1777.

2 files changed, 29 insertions, 15 deletions

diff --git a/riscv/csr_init.cc b/riscv/csr_init.cc
index d72c925..2c2760f 100644
--- a/riscv/csr_init.cc
+++ b/riscv/csr_init.cc
@@ -205,13 +205,14 @@ void state_t::csr_init(processor_t* const proc, reg_t max_isa)
     add_csr(CSR_TDATA2, tdata2 = std::make_shared<tdata2_csr_t>(proc, CSR_TDATA2));
     add_csr(CSR_TDATA3, std::make_shared<tdata3_csr_t>(proc, CSR_TDATA3));
     add_csr(CSR_TINFO, std::make_shared<tinfo_csr_t>(proc, CSR_TINFO));
-    add_csr(CSR_TCONTROL, tcontrol = std::make_shared<masked_csr_t>(proc, CSR_TCONTROL, CSR_TCONTROL_MPTE | CSR_TCONTROL_MTE, 0));
+    if (!proc->extension_enabled_const('S')) {
+      add_csr(CSR_TCONTROL, tcontrol = std::make_shared<masked_csr_t>(proc, CSR_TCONTROL, CSR_TCONTROL_MPTE | CSR_TCONTROL_MTE, 0));
+    }
   } else {
     add_csr(CSR_TDATA1, std::make_shared<const_csr_t>(proc, CSR_TDATA1, 0));
     add_csr(CSR_TDATA2, tdata2 = std::make_shared<const_csr_t>(proc, CSR_TDATA2, 0));
     add_csr(CSR_TDATA3, std::make_shared<const_csr_t>(proc, CSR_TDATA3, 0));
     add_csr(CSR_TINFO, std::make_shared<const_csr_t>(proc, CSR_TINFO, 0));
-    add_csr(CSR_TCONTROL, tcontrol = std::make_shared<const_csr_t>(proc, CSR_TCONTROL, 0));
   }
   unsigned scontext_length = (xlen == 32 ? 16 : 32); // debug spec suggests 16-bit for RV32 and 32-bit for RV64
   add_supervisor_csr(CSR_SCONTEXT, scontext = std::make_shared<masked_csr_t>(proc, CSR_SCONTEXT, (reg_t(1) << scontext_length) - 1, 0));
diff --git a/riscv/triggers.cc b/riscv/triggers.cc
index a0a84c0..e130a87 100644
--- a/riscv/triggers.cc
+++ b/riscv/triggers.cc
@@ -74,19 +74,32 @@ bool trigger_t::common_match(processor_t * const proc, bool use_prev_prv) const
     return false;
 
   if (get_action() == ACTION_DEBUG_EXCEPTION) {
-    const bool mstatus_mie = state->mstatus->read() & MSTATUS_MIE;
-    if (prv == PRV_M && !mstatus_mie)
-      return false;
-
-    const bool sstatus_sie = state->sstatus->read() & MSTATUS_SIE;
-    const bool medeleg_breakpoint = (state->medeleg->read() >> CAUSE_BREAKPOINT) & 1;
-    if (prv == PRV_S && !v && medeleg_breakpoint && !sstatus_sie)
-      return false;
-
-    const bool vsstatus_sie = state->vsstatus->read() & MSTATUS_SIE;
-    const bool hedeleg_breakpoint = (state->hedeleg->read() >> CAUSE_BREAKPOINT) & 1;
-    if (prv == PRV_S && v && medeleg_breakpoint && hedeleg_breakpoint && !vsstatus_sie)
-      return false;
+    if (proc->extension_enabled('S')) {
+      // The hardware prevents triggers with action=0 from matching or firing
+      // while in M-mode and while MIE in mstatus is 0. If medeleg [3]=1 then it
+      // prevents triggers with action=0 from matching or firing while in S-mode
+      // and while SIE in sstatus is 0. If medeleg [3]=1 and hedeleg [3]=1 then
+      // it prevents triggers with action=0 from matching or firing while in
+      // VS-mode and while SIE in vstatus is 0.
+
+      const bool mstatus_mie = state->mstatus->read() & MSTATUS_MIE;
+      if (prv == PRV_M && !mstatus_mie)
+        return false;
+
+      const bool sstatus_sie = state->sstatus->read() & MSTATUS_SIE;
+      const bool medeleg_breakpoint = (state->medeleg->read() >> CAUSE_BREAKPOINT) & 1;
+      if (prv == PRV_S && !v && medeleg_breakpoint && !sstatus_sie)
+        return false;
+
+      const bool vsstatus_sie = state->vsstatus->read() & MSTATUS_SIE;
+      const bool hedeleg_breakpoint = (state->hedeleg->read() >> CAUSE_BREAKPOINT) & 1;
+      if (prv == PRV_S && v && medeleg_breakpoint && hedeleg_breakpoint && !vsstatus_sie)
+        return false;
+    } else {
+      // mte and mpte in tcontrol is implemented. medeleg [3] is hard-wired to 0.
+      if (prv == PRV_M && !(tcontrol_value(state) & CSR_TCONTROL_MTE))
+        return false;
+    }
   }
 
   return true;