Merge branch 'bpf: Speed up symbol resolving in kprobe multi link'

Merge branch 'bpf: Speed up symbol resolving in kprobe multi link'

Jiri Olsa says:

====================

hi,
sending additional fix for symbol resolving in kprobe multi link
requested by Alexei and Andrii [1].

This speeds up bpftrace kprobe attachment, when using pure symbols
(3344 symbols) to attach:

Before:

  # perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* {  } i:ms:1 { exit(); }'
  ...
  6.5681 +- 0.0225 seconds time elapsed  ( +-  0.34% )

After:

  # perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* {  } i:ms:1 { exit(); }'
  ...
  0.5661 +- 0.0275 seconds time elapsed  ( +-  4.85% )

v6 changes:
  - rewrote patch 1 changelog and fixed the line length [Christoph]

v5 changes:
  - added acks [Masami]
  - workaround in selftest for RCU warning by filtering out several
    functions to attach

v4 changes:
  - fix compile issue [kernel test robot]
  - added acks [Andrii]

v3 changes:
  - renamed kallsyms_lookup_names to ftrace_lookup_symbols
    and moved it to ftrace.c [Masami]
  - added ack [Andrii]
  - couple small test fixes [Andrii]

v2 changes (first version [2]):
  - removed the 2 seconds check [Alexei]
  - moving/forcing symbols sorting out of kallsyms_lookup_names function [Alexei]
  - skipping one array allocation and copy_from_user [Andrii]
  - several small fixes [Masami,Andrii]
  - build fix [kernel test robot]

thanks,
jirka

[1] https://lore.kernel.org/bpf/CAEf4BzZtQaiUxQ-sm_hH2qKPRaqGHyOfEsW96DxtBHRaKLoL3Q@mail.gmail.com/
[2] https://lore.kernel.org/bpf/20220407125224.310255-1-jolsa@kernel.org/
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>