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Security features are slowly transforming some CPUs away from Von Neumann and into Modified Harvard architecture Take the x64 feature W^X . When enabled, you
by hyperman1 5y ago
Security features are slowly transforming some CPUs away from Von Neumann and into Modified Harvard architecture
Take the x64 feature W^X . When enabled, you have 2 kinds of memory pages. Some contain code and some have program-created data. OS mechanisms allow for a controlled way to change this data into code by modifying page table flags. That’s a modified harvard architecture.
https://en.m.wikipedia.org/wiki/Modified_Harvard_architecture https://en.m.wikipedia.org/wiki/Modified_Harvard_architectur...
- iamdvlpr 5y agoInteresting. Do you happen to know if OS makers are currently adapting and applying more changes such as the one you described on the x64 feature? Thanks for sharing the link.
- hyperman1 5y agoIt has already been done, e.g. windows DEP. Main blocker is that software which generates code needs to be adapted to tell the OS where it put that code. Attackers adapted by e.g.inventing Return Oriented Programming(ROP): As they could not inject code into processes directly, they started overwriting the stack with adresses to interesting functions. When an attacked function returns, it does not resume the caller, but executes code in the executable chosen by attackers, with args dictated by the attacker.