ROM only executable in firmware mode, except for address of

syscall_addr_reg

Co-authored-by: Mikael Ågren <[email protected]>

hw/application_fpga/core/tk1/rtl/tk1.v

@@ -106,6 +106,7 @@ module tk1 (
   localparam FW_RAM_FIRST = 32'hd0000000;
   localparam FW_RAM_LAST = 32'hd00007ff;
 
+  localparam FW_ROM_FIRST = 32'h00000000;
   localparam FW_ROM_LAST = 32'h00001fff;
 
   // ILLEGAL_ADDR is outside of the physical memory, and will trap in
@@ -398,6 +399,9 @@ module tk1 (
   //
   // Trying to execute instructions in FW-RAM.
   //
+  // Executing instructions in ROM, while not being in firmware
+  // mode, or at the address set in syscall_addr_reg.
+  //
   // Trying to execute code in mem area set to be data access only.
   // This requires execution monitor to have been setup and
   // enabled.
@@ -415,6 +419,14 @@ module tk1 (
           force_trap_set = 1'h1;
         end
 
+        if (system_mode_reg) begin
+          if (cpu_addr != syscall_addr_reg) begin
+            if ((cpu_addr >= FW_ROM_FIRST) && (cpu_addr <= FW_ROM_LAST)) begin
+              force_trap_set = 1'h1;
+            end
+          end
+        end
+
         if (cpu_mon_en_reg) begin
           if ((cpu_addr >= cpu_mon_first_reg) && (cpu_addr <= cpu_mon_last_reg)) begin
             force_trap_set = 1'h1;