perf bpf: Add simple pid_filter class accessible to BPF proggies

Will be used in the augmented_raw_syscalls.c to implement 'perf trace
--filter-pids'.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-9sybmz4vchlbpqwx2am13h9e@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/include/bpf/pid_filter.h

+// SPDX-License-Identifier: LGPL-2.1
+
+#ifndef _PERF_BPF_PID_FILTER_
+#define _PERF_BPF_PID_FILTER_
+
+#include <bpf.h>
+
+#define pid_filter(name) pid_map(name, bool)
+
+static int pid_filter__add(struct bpf_map *pids, pid_t pid)
+{
+	bool value = true;
+	return bpf_map_update_elem(pids, &pid, &value, BPF_NOEXIST);
+}
+
+static bool pid_filter__has(struct bpf_map *pids, pid_t pid)
+{
+	return bpf_map_lookup_elem(pids, &pid) != NULL;
+}
+
+#endif // _PERF_BPF_PID_FILTER_