Supervisor Mode Access Prevention
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Supervisor Mode Access Prevention (SMAP) is a feature of some CPU implementations such as the Intel Broadwell (microarchitecture) that allows supervisor mode programs to optionally set user-space memory mappings so that access to those mappings from supervisor mode will cause a trap. This makes it harder for malicious programs to "trick" the kernel into using instructions or data from a user-space program.
References:
https://lwn.net/Articles/517475/
https://software.intel.com/en-us/articles/intel-xeon-processor-d-product-family-technical-overview#_Toc419802869