The short answer is that we only have to calculate the offset per go version, no expensive runtime scanning is required.

The long answer is that the offsets are the byte alignment offsets for the go structs containing the pointers to the file descriptor and buffers. Fortunately we only have to calculate these for each version where the TLS structs within go actually change, so not even for every version. For instance, if a field is added, removed, or changes type then the location in memory where those pointers will be found changes. We can then calculate the actual offset at runtime where we know which architecture (amd64, arm64, etc) with a simple calculation. Within the eBPF probe, when the function is called, it uses pointer arithmetic to extract the location of the file descriptor and buffer directly.