What is "return-oriented programming" (ROP) as a security concern related to computer architecture, and what architectural feature helps mitigate it?

A ROP chains together short code sequences ending in "return" instructions, already present in memory, to perform malicious operations without injecting new code; mitigations include shadow stacks or pointer authentication for control-flow integrity B ROP is a programming paradigm with no security implications, used for writing return statements in high-level languages C It is a technique that requires physically reprogramming the CPU's silicon D ROP attacks can be fully prevented simply by increasing clock speed