Reinstate function needed by bpftrace-0.10

bpftrace still relies on `bpf_detach_kfunc` which was removed in
bcc-0.15.0. It doesn't do anything, so there is no harm on adding it
back until bpftrace is updated.

Signed-off-by: Rafael dos Santos <rdossant@redhat.com>

bcc-0.15.0-Reinstate-bpf_detach_kfunc.patch

@@ -0,0 +1,46 @@
+From 0b9a7f0de847d945bc5dd83961136e04d6c890ec Mon Sep 17 00:00:00 2001
+From: Jerome Marchand <jmarchan@redhat.com>
+Date: Wed, 1 Jul 2020 17:52:51 +0200
+Subject: [PATCH] Reinstate bpf_detach_kfunc
+
+It doesn't do anything, but bpftrace still calls it.
+
+---
+ src/cc/libbpf.c | 7 +++++++
+ src/cc/libbpf.h | 2 ++
+ 2 files changed, 9 insertions(+)
+
+diff --git a/src/cc/libbpf.c b/src/cc/libbpf.c
+index 010d1222..4c43218f 100644
+--- a/src/cc/libbpf.c
++++ b/src/cc/libbpf.c
+@@ -1186,6 +1186,13 @@ bool bpf_has_kernel_btf(void)
+   return libbpf_find_vmlinux_btf_id("bpf_prog_put", 0) > 0;
+ }
+ 
++int bpf_detach_kfunc(int prog_fd, char *func)
++{
++  UNUSED(prog_fd);
++  UNUSED(func);
++  return 0;
++}
++
+ int bpf_attach_kfunc(int prog_fd)
+ {
+   int ret;
+diff --git a/src/cc/libbpf.h b/src/cc/libbpf.h
+index 61471b5b..bcae5c99 100644
+--- a/src/cc/libbpf.h
++++ b/src/cc/libbpf.h
+@@ -94,6 +94,8 @@ int bpf_detach_tracepoint(const char *tp_category, const char *tp_name);
+ 
+ int bpf_attach_raw_tracepoint(int progfd, const char *tp_name);
+ 
++  int bpf_detach_kfunc(int prog_fd, char *func);
++
+ int bpf_attach_kfunc(int prog_fd);
+ 
+ int bpf_attach_lsm(int prog_fd);
+-- 
+2.25.4
+

bcc.spec

@@ -9,7 +9,7 @@
 
 Name:           bcc
 Version:        0.15.0
-Release:        1%{?dist}
+Release:        2%{?dist}
 Summary:        BPF Compiler Collection (BCC)
 License:        ASL 2.0
 URL:            https://github.com/iovisor/bcc
@@ -17,6 +17,8 @@ URL:            https://github.com/iovisor/bcc
 Source0:        %{url}/releases/download/v%{version}/%{name}-src-with-submodule.tar.gz
 #Source0:        %{url}/archive/v%{version}/%{name}-%{version}.tar.gz
 
+Patch0:         %{name}-%{version}-Reinstate-bpf_detach_kfunc.patch
+
 # Arches will be included as upstream support is added and dependencies are
 # satisfied in the respective arches
 ExclusiveArch:  x86_64 %{power64} aarch64 s390x
@@ -179,6 +181,9 @@ rm -rf %{buildroot}%{_datadir}/%{name}/tools/old/
 
 
 %changelog
+* Thu Jul 02 2020 Rafael dos Santos <rdossant@redhat.com> - 0.15.0-2
+- Reinstate a function needed by bpftrace
+
 * Tue Jun 23 2020 Rafael dos Santos <rdossant@redhat.com> - 0.15.0-1
 - Rebase to latest upstream version (#1849239)