Thread safe for in line hook

[ZMer2019]

code:

disable_interrupts();
disable_wp();
memcpy((void*)patch_addr, trampoline, sizeof(trampoline));
enable_wp();
enbale_interrupts();

Actually,"trampoline" generally destroys multiple instructions, in SMP system, how to make theses code thread safe?

[keenjoy95]

It seems that you are really curious about this issue... ;)
(didi/kemon#2)

Let me answer this question for @SilverMoonSecurity / Yuefeng, here is the solution:
https://developer.apple.com/library/archive/releasenotes/Performance/RN-AffinityAPI/#//apple_ref/doc/uid/TP40006635-CH1-DontLinkElementID_2

An application that wants to place a thread on every available processor would do the following:

1. Obtain the number of processors on the system using sysctl(3) (see below).
2. Create that number of threads.
3. Set each thread with a distinct affinity tag.
4. Start all threads.

By using the above method, you can have one thread complete the inline hook operation and the rest start to spin.