[PATCH RFC 3/4] lib/bpf: Add support for ftrace event attach and detach

["Joel Fernandes (Google)" <joel@joelfernandes.org>]

Add the needed library support in this commit.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 tools/lib/bpf/bpf.c      | 53 ++++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/bpf.h      |  4 +++
 tools/lib/bpf/libbpf.map |  2 ++
 3 files changed, 59 insertions(+)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index c4a48086dc9a..28c5a7d00d14 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -24,6 +24,9 @@
 #include <stdlib.h>
 #include <string.h>
 #include <memory.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
 #include <unistd.h>
 #include <asm/unistd.h>
 #include <linux/bpf.h>
@@ -57,6 +60,8 @@
 #define min(x, y) ((x) < (y) ? (x) : (y))
 #endif
 
+#define TRACEFS "/sys/kernel/debug/tracing"
+
 static inline __u64 ptr_to_u64(const void *ptr)
 {
 	return (__u64) (unsigned long) ptr;
@@ -658,6 +663,54 @@ int bpf_raw_tracepoint_open(const char *name, int prog_fd)
 	return sys_bpf(BPF_RAW_TRACEPOINT_OPEN, &attr, sizeof(attr));
 }
 
+int bpf_raw_tracepoint_ftrace_attach(const char *subsys, const char *name,
+				     int prog_fd)
+{
+	char buf[256];
+	int len, ret, tfd;
+
+	sprintf(buf, "%s/events/%s/%s/bpf", TRACEFS, subsys, name);
+	tfd = open(buf, O_WRONLY);
+	if (tfd < 0)
+		return tfd;
+
+	sprintf(buf, "attach:%d", prog_fd);
+	len = strlen(buf);
+	ret = write(tfd, buf, len);
+
+	if (ret < 0)
+		goto err;
+	if (ret != len)
+		ret = -1;
+err:
+	close(tfd);
+	return ret;
+}
+
+int bpf_raw_tracepoint_ftrace_detach(const char *subsys, const char *name,
+				     int prog_fd)
+{
+	char buf[256];
+	int len, ret, tfd;
+
+	sprintf(buf, "%s/events/%s/%s/bpf", TRACEFS, subsys, name);
+	tfd = open(buf, O_WRONLY);
+	if (tfd < 0)
+		return tfd;
+
+	sprintf(buf, "detach:%d", prog_fd);
+	len = strlen(buf);
+	ret = write(tfd, buf, len);
+
+	if (ret < 0)
+		goto err;
+	if (ret != len)
+		ret = -1;
+err:
+	close(tfd);
+	return ret;
+}
+
 int bpf_load_btf(void *btf, __u32 btf_size, char *log_buf, __u32 log_buf_size,
 		 bool do_log)
 {
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 9593fec75652..5b9c44658037 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -163,6 +163,10 @@ LIBBPF_API int bpf_prog_query(int target_fd, enum bpf_attach_type type,
 			      __u32 query_flags, __u32 *attach_flags,
 			      __u32 *prog_ids, __u32 *prog_cnt);
 LIBBPF_API int bpf_raw_tracepoint_open(const char *name, int prog_fd);
+LIBBPF_API int bpf_raw_tracepoint_ftrace_attach(const char *subsys,
+						const char *name, int prog_fd);
+LIBBPF_API int bpf_raw_tracepoint_ftrace_detach(const char *subsys,
+						const char *name, int prog_fd);
 LIBBPF_API int bpf_load_btf(void *btf, __u32 btf_size, char *log_buf,
 			    __u32 log_buf_size, bool do_log);
 LIBBPF_API int bpf_task_fd_query(int pid, int fd, __u32 flags, char *buf,
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 673001787cba..fca377b688c2 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -163,4 +163,6 @@ LIBBPF_0.0.3 {
 		bpf_map__is_internal;
 		bpf_map_freeze;
 		btf__finalize_data;
+		bpf_raw_tracepoint_ftrace_attach;
+		bpf_raw_tracepoint_ftrace_detach;
 } LIBBPF_0.0.2;
-- 
2.22.0.410.gd8fdbe21b5-goog