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

Wang Nan
2015-05-17T10:58:41Z

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