8086 memory space was: The Soul of Barb's New Machine 1155

Indeed. It's a very old idea. I fear that it's been neglected too long because of the "cost" of implementation. Of course; spending an extra $50 on a personal computer to make it more stable and robust against such attacks is well within the budget of the consumer. vis cost of "anti-virus" software.

I believe that at least one of my desktop machines has the hardware for similar functionality; and it's more than a decade old. IIRC, the Motorola 68k MMU had execute permission bits on the pages which the CPU core should set in supervisor mode to ensure that there's not a bus error when the program counter enters the page.

It's not sufficient for the file permissions to be set. The file probably contains non-execable data such as static data (message strings, etc). So the only way to "cleanly" implement it using the method you describe is to have several files for each program. That gets ugly, very quickly.

Only the executeable object blocks should have the execute bits set by the guts of the operating system operating in privileged mode in response to a system call to execute a file. -- "Bernd Felsche - Innovative Reckoning, Perth, Western Australia ASCII ribbon campaign I'm a .signature virus! X against HTML mail Copy me into your ~-.signature and postings to help me spread!