完成rtthread适配

cpu/riscv.c

@@ -115,6 +115,7 @@ uint32_t mem_w_read(riscv_t* riscv, uint32_t addr) {
   if (addr & 0x3) {
     riscv->exc_code = 4;
     riscv->mtval = addr;
+    printf("unaligned access addr:%08x\n", addr);
     return ret;
   }
   if (addr >= MEM_ADDR_BASE && addr < MEM_ADDR_BASE + MEM_SIZE) {
@@ -125,6 +126,7 @@ uint32_t mem_w_read(riscv_t* riscv, uint32_t addr) {
     device_read(riscv, addr, ret);
     riscv->exc_code = 5;
     riscv->mtval = addr;
+    printf("error addr:%08x\n", addr);
   }
   return ret;
 }
@@ -353,7 +355,7 @@ void ins_mret(riscv_t* riscv) {
   } else {
     riscv->mstatus &= ~MSTATUS_MIE;
   }
-  printf("mret: pc=%08x\n", riscv->pc);
+  // printf("mret: pc=%08x\n", riscv->pc);
 }
 
 void ins_or(riscv_t* riscv, int rs2, int rs1, int rd) {