memory_fd = open("/dev/mem", O_RDWR | O_SYNC | O_CLOEXEC); mapping = mmap(NULL, PAGE_SIZE_U64, prot, MAP_SHARED, descriptor, (off_t)alias_gpa_for_hpa(page_hpa));

Sure looks like a C hello world kernel debugger.

The jailer exposes neither /dev/mem nor anything you could use to make the device node for it.