Merge branch 'bpf: Fixes for CONFIG_X86_KERNEL_IBT'

Jiri Olsa says:

====================
Martynas reported bpf_get_func_ip returning +4 address when
CONFIG_X86_KERNEL_IBT option is enabled and I found there are
some failing bpf tests when this option is enabled.

The CONFIG_X86_KERNEL_IBT option adds endbr instruction at the
function entry, so the idea is to 'fix' entry ip for kprobe_multi
and trampoline probes, because they are placed on the function
entry.

v5 changes:
  - updated uapi/linux/bpf.h headers with comment for
    bpf_get_func_ip returning 0 [Andrii]
  - added acks

v4 changes:
  - used get_kernel_nofault to read previous instruction [Peter]
  - used movabs instruction in trampoline comment [Peter]
  - renamed fentry_ip argument in kprobe_multi_link_handler [Peter]

v3 changes:
  - using 'unused' bpf function to get IBT config option
    into selftest skeleton
  - rebased to current bpf-next/master
  - added ack/review from Masami

v2 changes:
  - change kprobes get_func_ip to return zero for kprobes
    attached within the function body [Andrii]
  - detect IBT config and properly test kprobe with offset
    [Andrii]

v1 changes:
  - read previous instruction in kprobe_multi link handler
    and adjust entry_ip for CONFIG_X86_KERNEL_IBT option
  - split first patch into 2 separate changes
  - update changelogs
====================

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>