Fix pointer masking for misaligned accesses

Pointer masking needs to be reapplied after computing the address of the
tail of a misaligned access in case there's a carry-out into the MSBs.

Resolves #1895

Author: aswaterman

riscv/mmu.cc

@@ -241,8 +241,10 @@ void mmu_t::load_slow_path(reg_t original_addr, reg_t len, uint8_t* bytes, xlate
 
     reg_t len_page0 = std::min(len, PGSIZE - transformed_addr % PGSIZE);
     load_slow_path_intrapage(len_page0, bytes, access_info);
-    if (len_page0 != len)
-      load_slow_path_intrapage(len - len_page0, bytes + len_page0, access_info.split_misaligned_access(len_page0));
+    if (len_page0 != len) {
+      auto tail_access_info = generate_access_info(original_addr + len_page0, LOAD, xlate_flags);
+      load_slow_path_intrapage(len - len_page0, bytes + len_page0, tail_access_info);
+    }
   }
 
   while (len > sizeof(reg_t)) {
@@ -306,8 +308,10 @@ void mmu_t::store_slow_path(reg_t original_addr, reg_t len, const uint8_t* bytes
 
     reg_t len_page0 = std::min(len, PGSIZE - transformed_addr % PGSIZE);
     store_slow_path_intrapage(len_page0, bytes, access_info, actually_store);
-    if (len_page0 != len)
-      store_slow_path_intrapage(len - len_page0, bytes + len_page0, access_info.split_misaligned_access(len_page0), actually_store);
+    if (len_page0 != len) {
+      auto tail_access_info = generate_access_info(original_addr + len_page0, STORE, xlate_flags);
+      store_slow_path_intrapage(len - len_page0, bytes + len_page0, tail_access_info, actually_store);
+    }
   } else {
     store_slow_path_intrapage(len, bytes, access_info, actually_store);
   }

riscv/mmu.h

@@ -57,10 +57,6 @@ struct mem_access_info_t {
   const bool effective_virt;
   const xlate_flags_t flags;
   const access_type type;
-
-  mem_access_info_t split_misaligned_access(reg_t offset) const {
-    return {vaddr + offset, transformed_vaddr + offset, effective_priv, effective_virt, flags, type};
-  }
 };
 
 void throw_access_exception(bool virt, reg_t addr, access_type type);