Fix priority of mcontrol trigger load address before

The spec defines the mcontrol load address has a higher priority over
page fault and address misaligned (Debug spec, Table 5.2). Thus, the
trigger checking should be before the translation and alignment
checking.

The previous implementation checks the trigger after the translation
and alignment, resulting in incorrect priority. For instance, when page
fault and trigger occur on the same instruction, the previous
implementation will choose to raise the page fault, which contradicts
the priority requirement.

This commit adds an address-only trigger checking before the misaligned
checking and translation. The trigger will fire on the instruction
instead of the page fault in the above case.

2 files changed, 12 insertions, 0 deletions

diff --git a/riscv/mmu.cc b/riscv/mmu.cc
index 0dbb94e..3048bde 100644
--- a/riscv/mmu.cc
+++ b/riscv/mmu.cc
@@ -141,6 +141,13 @@ bool mmu_t::mmio_store(reg_t addr, size_t len, const uint8_t* bytes)
 
 void mmu_t::load_slow_path(reg_t addr, reg_t len, uint8_t* bytes, uint32_t xlate_flags)
 {
+  if (!matched_trigger) {
+    reg_t data = reg_from_bytes(len, bytes);
+    matched_trigger = trigger_exception(triggers::OPERATION_LOAD, addr, false);
+    if (matched_trigger)
+      throw *matched_trigger;
+  }
+
   reg_t paddr = translate(addr, len, LOAD, xlate_flags);
 
   if (auto host_addr = sim->addr_to_mem(paddr)) {
diff --git a/riscv/mmu.h b/riscv/mmu.h
index d076aeb..3a06c1e 100644
--- a/riscv/mmu.h
+++ b/riscv/mmu.h
@@ -101,6 +101,11 @@ public:
   #define load_func(type, prefix, xlate_flags) \
     type##_t ALWAYS_INLINE prefix##_##type(reg_t addr, bool require_alignment = false) { \
       if (unlikely(addr & (sizeof(type##_t)-1))) { \
+        if (!matched_trigger) { \
+          matched_trigger = trigger_exception(triggers::OPERATION_LOAD, addr, false); \
+          if (matched_trigger) \
+            throw *matched_trigger; \
+        } \
         if (require_alignment) load_reserved_address_misaligned(addr); \
         else return misaligned_load(addr, sizeof(type##_t), xlate_flags); \
       } \