Comment by Denvercoder9
3 years ago
Not everything is detectable at runtime, such as syscall numbers (which is what's being tested for here).
3 years ago
Not everything is detectable at runtime, such as syscall numbers (which is what's being tested for here).
Runtime syscall number detection is very common in practice, since the kernel returns ENOSYS to enable that exact ability for glibc and other shim libraries
That's syscall for _availability_ detection, not its number. There's no way to ask the kernel "what's the number of the syscall commonly known as read()".