Fuzzer has figured out how to corrupt input/output shmem regions
abusing the text memcpy in syz_kvm_setup_cpu. It guessed a negative
text_size value that causes the memcpy to overwrite shmem regions.
Protect better against such cases:
1. Make text_size unsigned (there is already a check that it is less than 1000).
2. Map input region as readable only, we don't write to it.
3. Add address sanity check to segv_handler, if we see that we are writing
into executable data, it's better to crash instantly.
1. Basic support for arm64 kvm testing.
2. Fix compiler warnings in x86 kvm code.
3. Test all pseudo syz calls in csource.
4. Fix handling of real code in x86.
