Merge branch 'bpf_line_info'

Martin Lau says:

====================
This patch series introduces the bpf_line_info.  Please see individual patch
for details.

It will be useful for introspection purpose, like:

[root@arch-fb-vm1 bpf]# ~/devshare/fb-kernel/linux/tools/bpf/bpftool/bpftool prog dump jited pinned /sys/fs/bpf/test_btf_haskv
[...]
int test_long_fname_2(struct dummy_tracepoint_args * arg):
bpf_prog_44a040bf25481309_test_long_fname_2:
; static int test_long_fname_2(struct dummy_tracepoint_args *arg)
   0:   push   %rbp
   1:   mov    %rsp,%rbp
   4:   sub    $0x30,%rsp
   b:   sub    $0x28,%rbp
   f:   mov    %rbx,0x0(%rbp)
  13:   mov    %r13,0x8(%rbp)
  17:   mov    %r14,0x10(%rbp)
  1b:   mov    %r15,0x18(%rbp)
  1f:   xor    %eax,%eax
  21:   mov    %rax,0x20(%rbp)
  25:   xor    %esi,%esi
; int key = 0;
  27:   mov    %esi,-0x4(%rbp)
; if (!arg->sock)
  2a:   mov    0x8(%rdi),%rdi
; if (!arg->sock)
  2e:   cmp    $0x0,%rdi
  32:   je     0x0000000000000070
  34:   mov    %rbp,%rsi
; counts = bpf_map_lookup_elem(&btf_map, &key);
  37:   add    $0xfffffffffffffffc,%rsi
  3b:   movabs $0xffff8881139d7480,%rdi
  45:   add    $0x110,%rdi
  4c:   mov    0x0(%rsi),%eax
  4f:   cmp    $0x4,%rax
  53:   jae    0x000000000000005e
  55:   shl    $0x3,%rax
  59:   add    %rdi,%rax
  5c:   jmp    0x0000000000000060
  5e:   xor    %eax,%eax
; if (!counts)
  60:   cmp    $0x0,%rax
  64:   je     0x0000000000000070
; counts->v6++;
  66:   mov    0x4(%rax),%edi
  69:   add    $0x1,%rdi
  6d:   mov    %edi,0x4(%rax)
  70:   mov    0x0(%rbp),%rbx
  74:   mov    0x8(%rbp),%r13
  78:   mov    0x10(%rbp),%r14
  7c:   mov    0x18(%rbp),%r15
  80:   add    $0x28,%rbp
  84:   leaveq
  85:   retq
[...]
====================

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