@b0rk You don't see a bunch of `stat` system calls to work out the paths of the shared libraries because that information is precalculated and stored in `/etc/ld.so.cache`, which it opens on line 4 of your full strace report. I am not sure if this is documented anywhere. I only know about it myself because I help out with glibc development sometimes.

And finally, I don't know _exactly_ what the system calls on lines 71 through 83 of the full strace are for, but I know some of it:

- `arch_prctl(ARCH_SET_FS, ...)` is setting the x86 register %fs, which can be used to hold a pointer (Linux uses it to point to data that varies from thread to thread, like `errno`) but for complicated historical reasons only the kernel can _set_ that pointer.

- The long string of `mprotect`s are making parts of the shared libraries read-only. These parts have to be writable while the dynamic linker is working, but after it's done setting everything up they can be read-only. This is a security feature, but I only vaguely understand why (it has to do with making it harder to exploit buffer overflow bugs).

- The `munmap` on line 81 pairs with the `mmap` on line 6. The dynamic linker is done with `/etc/ld.so.cache` at this point.

- I don't know what `set_tid_address` and `set_robust_list` are for.

@zwol @b0rk set_tid_address is used to inform the kernel of a place where the thread ID is stored. AFAIK it has exactly one use which is that you can use it for futexes (which pthread is built on). set_robust_list is also for futexes–namely it’s a list of them.