Add bpf_close_perf_event_fd

Add bpf_close_perf_event_fd helper that first disables, then closes a
perf event fd. Use it in Python and C++ API for detach perf event

src/cc/BPF.cc

@@ -561,8 +561,8 @@ StatusTuple BPF::detach_perf_event_all_cpu(open_probe_t& attr) {
   bool has_error = false;
   std::string err_msg;
   for (const auto& it : *attr.per_cpu_fd) {
-    int res = close(it.second);
-    if (res < 0) {
+    int res = bpf_close_perf_event_fd(it.second);
+    if (res != 0) {
       has_error = true;
       err_msg += "Failed to close perf event FD " + std::to_string(it.second) +
                  " For CPU " + std::to_string(it.first) + ": ";

src/cc/libbpf.c

@@ -808,10 +808,21 @@ int bpf_attach_perf_event(int progfd, uint32_t ev_type, uint32_t ev_config,
   return fd;
 }
 
-int bpf_detach_perf_event(uint32_t ev_type, uint32_t ev_config) {
-  // Right now, there is nothing to do, but it's a good idea to encourage
-  // callers to detach anything they attach.
-  return 0;
+int bpf_close_perf_event_fd(int fd) {
+  int res, error = 0;
+  if (fd >= 0) {
+    res = ioctl(fd, PERF_EVENT_IOC_DISABLE, 0);
+    if (res != 0) {
+      perror("ioctl(PERF_EVENT_IOC_DISABLE) failed");
+      error = res;
+    }
+    res = close(fd);
+    if (res != 0) {
+      perror("close perf event FD failed");
+      error = (res && !error) ? res : error;
+    }
+  }
+  return error;
 }
 
 int bpf_obj_pin(int fd, const char *pathname)

src/cc/libbpf.h

@@ -82,7 +82,8 @@ int bpf_attach_xdp(const char *dev_name, int progfd, uint32_t flags);
 int bpf_attach_perf_event(int progfd, uint32_t ev_type, uint32_t ev_config,
                           uint64_t sample_period, uint64_t sample_freq,
                           pid_t pid, int cpu, int group_fd);
-int bpf_detach_perf_event(uint32_t ev_type, uint32_t ev_config);
+
+int bpf_close_perf_event_fd(int fd);
 
 int bpf_obj_pin(int fd, const char *pathname);
 int bpf_obj_get(const char *pathname);

src/python/bcc/__init__.py

@@ -730,13 +730,13 @@ class BPF(object):
         except KeyError:
             raise Exception("Perf event type {} config {} not attached".format(
                 ev_type, ev_config))
+
+        res = 0
         for fd in fds.values():
-            os.close(fd)
-        res = lib.bpf_detach_perf_event(ev_type, ev_config)
-        if res < 0:
+            res = lib.bpf_close_perf_event_fd(fd) or res
+        if res != 0:
             raise Exception("Failed to detach BPF from perf event")
         del self.open_perf_events[(ev_type, ev_config)]
-        return res
 
     def _add_uprobe(self, name, probe):
         global _num_open_probes

src/python/bcc/libbcc.py

@@ -115,14 +115,15 @@ lib.perf_reader_free.argtypes = [ct.c_void_p]
 lib.perf_reader_fd.restype = int
 lib.perf_reader_fd.argtypes = [ct.c_void_p]
 
-lib.bpf_attach_xdp.restype = ct.c_int;
+lib.bpf_attach_xdp.restype = ct.c_int
 lib.bpf_attach_xdp.argtypes = [ct.c_char_p, ct.c_int, ct.c_uint]
 
-lib.bpf_attach_perf_event.restype = ct.c_int;
+lib.bpf_attach_perf_event.restype = ct.c_int
 lib.bpf_attach_perf_event.argtype = [ct.c_int, ct.c_uint, ct.c_uint, ct.c_ulonglong, ct.c_ulonglong,
         ct.c_int, ct.c_int, ct.c_int]
-lib.bpf_detach_perf_event.restype = ct.c_int;
-lib.bpf_detach_perf_event.argtype = [ct.c_uint, ct.c_uint]
+
+lib.bpf_close_perf_event_fd.restype = ct.c_int
+lib.bpf_close_perf_event_fd.argtype = [ct.c_int]
 
 # bcc symbol helpers
 class bcc_symbol(ct.Structure):