A shim dynamic loader for overriding CPUID, using processor support for CPUID faulting on Ivy Bridge+, and the Linux kernel support for ARCH_GET_CPUID / ARCH_SET_CPUID subfunctions on 4.12+. This was implemented using a shim dynamic loader instead of e.g. LD_PRELOAD, because glibc 2.26+ performs CPU feature detection within the dynamic loader itself, which is too early to intercept with LD_PRELOAD.

Writeup: https://www.dcddcc.com/blog/2019-05-01-processor-cpuid-faulting-and-dynamic-loader-interposing.html

Overridable CPUID features: SSE, SSE2, SSE3, SSSE3, SSE41, SSE42, AVX, AVX2, AVX512, HLE, RTM.

cp <binary> <patch_binary>
patchelf --set-interpreter <absolute path>/libcpuidoverride.so <patch_binary>
NO_<feature>=1 <patch_binary>

For example, to disable AVX2 for the cpuid binary:

cp `which cpuid` patched_cpuid
patchelf --set-interpreter `pwd`/libcpuidoverride.so patched_cpuid
NO_AVX2=1 patched_cpuid

Alternatively, build with -Wl,--dynamic-linker=<absolute path>/libcpuidoverride.so.