[RFC PATCH v3 24/37] bpf tools: Load eBPF programs in object files into kernel

[Wang Nan <wangnan0@huawei.com>]

This patch utilizes previous introduced bpf_load_program to load
programs in the ELF file into kernel. Result is stored in 'fd' field
in 'struct bpf_program'.

During loading, it allocs a log buffer and free it before return.
Note that that buffer is not passed to bpf_load_program() if the first
loading try is successful. Doesn't use a statically allocated log
buffer to avoid potention multi-thread problem.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
---
 tools/lib/bpf/libbpf.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 5e25ea7..e8ef78e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -95,6 +95,8 @@ struct bpf_program {
 		int map_idx;
 	} *reloc_desc;
 	int nr_reloc;
+
+	int fd;
 };
 
 struct bpf_object {
@@ -128,10 +130,24 @@ struct bpf_object {
 };
 #define obj_elf_valid(o)	((o)->elf.fd >= 0)
 
+static void bpf_unload_program(struct bpf_program *prog)
+{
+	if (!prog)
+		return;
+
+	if (prog->fd >= 0) {
+		close(prog->fd);
+		prog->fd = -1;
+	}
+}
+
 static void bpf_clear_program(struct bpf_program *prog)
 {
 	if (!prog)
 		return;
+
+	bpf_unload_program(prog);
+
 	if (prog->section_name) {
 		free(prog->section_name);
 		prog->section_name = NULL;
@@ -200,6 +216,7 @@ bpf_program_alloc(struct bpf_object *obj, void *data, size_t size,
 	memcpy(prog->insns, data,
 	       prog->insns_cnt * sizeof(struct bpf_insn));
 	prog->idx = idx;
+	prog->fd = -1;
 
 	return prog;
 out:
@@ -756,6 +773,59 @@ static int bpf_obj_collect_reloc(struct bpf_object *obj)
 	return 0;
 }
 
+static int
+bpf_obj_load_prog(struct bpf_object *obj, struct bpf_program *prog)
+{
+	int fd, err;
+	char *log_buf;
+
+	log_buf = malloc(BPF_LOG_BUF_SIZE);
+	if (!log_buf)
+		pr_warning("Alloc log buffer for bpf loader error, "
+			   "continue without log\n");
+
+	fd = bpf_load_program(BPF_PROG_TYPE_KPROBE, prog->insns,
+			      prog->insns_cnt, obj->license,
+			      obj->kern_version, log_buf,
+			      BPF_LOG_BUF_SIZE);
+
+	if (fd >= 0) {
+		prog->fd = fd;
+		pr_debug("load bpf program '%s': fd = %d\n",
+			 prog->section_name, prog->fd);
+		err = 0;
+		goto out;
+	}
+
+	err = -EINVAL;
+	pr_warning("load bpf program '%s' failed: %s\n",
+		   prog->section_name, strerror(errno));
+
+	if (log_buf)
+		pr_warning("bpf: load: failed to load program '%s':\n"
+			   "-- BEGIN DUMP LOG ---\n%s\n-- END LOG --\n",
+				prog->section_name, log_buf);
+
+out:
+	if (log_buf)
+		free(log_buf);
+	return err;
+}
+
+static int
+bpf_obj_load_progs(struct bpf_object *obj)
+{
+	size_t i;
+	int err;
+
+	for (i = 0; i < obj->nr_programs; i++) {
+		err = bpf_obj_load_prog(obj, &obj->programs[i]);
+		if (err)
+			return err;
+	}
+	return 0;
+}
+
 static int bpf_obj_validate(struct bpf_object *obj)
 {
 	if (obj->kern_version == 0) {
@@ -819,6 +889,13 @@ int bpf_unload_object(struct bpf_object *obj)
 		free(obj->maps_fds);
 	}
 
+	if (obj->programs) {
+		size_t i;
+
+		for (i = 0; i < obj->nr_programs; i++)
+			bpf_unload_program(&obj->programs[i]);
+	}
+
 	return 0;
 }
 
@@ -831,6 +908,8 @@ int bpf_load_object(struct bpf_object *obj)
 		goto out;
 	if (bpf_obj_relocate(obj))
 		goto out;
+	if (bpf_obj_load_progs(obj))
+		goto out;
 
 	return 0;
 out:
-- 
1.8.3.4