Internal shadow stack on_clone

[zwimer]

The internal shadow stack needs to handle threading events.

[zwimer]

Specifically, clone calls that lead to threads. Use drmgr for the thread init event (does not get called for fork, this was tested) Note: thread exit event does get called when even a single threaded process dies. Instead of one stack, maybe keep a map<tid, shadowstack> ?

[zwimer]

Also: thread SS should clear stack on thread event

[zwimer]

This map requires syscall get tid on each call. Maybe try to do this once and store the result in TLS?

Drmgr gives an interface to store things in a thread local context. Look up the memtrace sample, it had a per_thread_t struct that's manipulated.

Also need to figure out what happens to TLS for k threads on fork event?

[zwimer]

Uses drmgr_register_tls_field, drmgr_get_tls_field, and drmgr_set_tls_field.

[zwimer]

Done