[RFC PATCH bpf-next 12/16] tools/libbpf: libbpf support for bpfdump

Yonghong Song
2020-04-08T23:26:05Z

Add a few libbpf APIs for bpfdump pin and query.

Also, parse the dump program section name,
retrieve the dump target path and open the path
to get a fd and assignment to prog->attach_prog_fd.
This is not really desirable, and need to think
more how to have equally better user interface
and cope with libbpf well.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
tools/lib/bpf/bpf.c | 33 +++++++++++++++++++++++++++
tools/lib/bpf/bpf.h | 5 +++++
tools/lib/bpf/libbpf.c | 48 ++++++++++++++++++++++++++++++++++++----
tools/lib/bpf/libbpf.h | 1 +
tools/lib/bpf/libbpf.map | 3 +++
5 files changed, 86 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 5cc1b0785d18..e8d4304fcc98 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -533,6 +533,39 @@ int bpf_obj_get(const char *pathname)
return sys_bpf(BPF_OBJ_GET, &attr, sizeof(attr));
}

+int bpf_obj_pin_dumper(int fd, const char *dname)
+{
+ union bpf_attr attr;
+
+ memset(&attr, 0, sizeof(attr));
+ attr.dumper_name = ptr_to_u64((void *)dname);
+ attr.bpf_fd = fd;
+ attr.file_flags = BPF_F_DUMP;
+
+ return sys_bpf(BPF_OBJ_PIN, &attr, sizeof(attr));
+}
+
+int bpf_dump_query(int query_fd, __u32 flags, void *target_proto_buf,
+ __u32 buf_len, __u32 *prog_id)
+{
+ union bpf_attr attr;
+ int ret;
+
+ memset(&attr, 0, sizeof(attr));
+ attr.dump_query.query_fd = query_fd;
+ attr.dump_query.flags = flags;
+ if (target_proto_buf) {
+ attr.dump_query.target_proto = ptr_to_u64((void *)target_proto_buf);
+ attr.dump_query.proto_buf_len = buf_len;
+ }
+
+ ret = sys_bpf(BPF_DUMP_QUERY, &attr, sizeof(attr));
+ if (!ret && prog_id)
+ *prog_id = attr.dump_query.prog_id;
+
+ return ret;
+}
+
int bpf_prog_attach(int prog_fd, int target_fd, enum bpf_attach_type type,
unsigned int flags)
{
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 46d47afdd887..2f89f8445962 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -149,8 +149,13 @@ LIBBPF_API int bpf_map_update_batch(int fd, void *keys, void *values,
__u32 *count,
const struct bpf_map_batch_opts *opts);

+LIBBPF_API int bpf_dump_query(int query_fd, __u32 flags,
+ void *target_proto_buf, __u32 buf_len,
+ __u32 *prog_id);
+
LIBBPF_API int bpf_obj_pin(int fd, const char *pathname);
LIBBPF_API int bpf_obj_get(const char *pathname);
+LIBBPF_API int bpf_obj_pin_dumper(int fd, const char *dname);

struct bpf_prog_attach_opts {
size_t sz; /* size of this struct for forward/backward compatibility */
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ff9174282a8c..c7a81ede56ce 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -79,6 +79,7 @@ static struct bpf_program *bpf_object__find_prog_by_idx(struct bpf_object *obj,
int idx);
static const struct btf_type *
skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id);
+static int fill_dumper_info(struct bpf_program *prog);

static int __base_pr(enum libbpf_print_level level, const char *format,
va_list args)
@@ -2365,8 +2366,12 @@ static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog)
/* BPF_PROG_TYPE_TRACING programs which do not attach to other programs
* also need vmlinux BTF
*/
- if (prog->type == BPF_PROG_TYPE_TRACING && !prog->attach_prog_fd)
- return true;
+ if (prog->type == BPF_PROG_TYPE_TRACING) {
+ if (prog->expected_attach_type == BPF_TRACE_DUMP)
+ return false;
+ if (!prog->attach_prog_fd)
+ return true;
+ }

return false;
}
@@ -4958,7 +4963,7 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
{
int err = 0, fd, i, btf_id;

- if ((prog->type == BPF_PROG_TYPE_TRACING ||
+ if (((prog->type == BPF_PROG_TYPE_TRACING && prog->expected_attach_type != BPF_TRACE_DUMP) ||
prog->type == BPF_PROG_TYPE_LSM ||
prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) {
btf_id = libbpf_find_attach_btf_id(prog);
@@ -5319,6 +5324,7 @@ static int bpf_object__resolve_externs(struct bpf_object *obj,

int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
{
+ struct bpf_program *prog;
struct bpf_object *obj;
int err, i;

@@ -5335,7 +5341,17 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)

obj->loaded = true;

- err = bpf_object__probe_caps(obj);
+ err = 0;
+ bpf_object__for_each_program(prog, obj) {
+ if (prog->type == BPF_PROG_TYPE_TRACING &&
+ prog->expected_attach_type == BPF_TRACE_DUMP) {
+ err = fill_dumper_info(prog);
+ if (err)
+ break;
+ }
+ }
+
+ err = err ? : bpf_object__probe_caps(obj);
err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
err = err ? : bpf_object__sanitize_and_load_btf(obj);
err = err ? : bpf_object__sanitize_maps(obj);
@@ -5459,6 +5475,11 @@ int bpf_program__pin_instance(struct bpf_program *prog, const char *path,
return 0;
}

+int bpf_program__pin_dumper(struct bpf_program *prog, const char *dname)
+{
+ return bpf_obj_pin_dumper(bpf_program__fd(prog), dname);
+}
+
int bpf_program__unpin_instance(struct bpf_program *prog, const char *path,
int instance)
{
@@ -6322,6 +6343,8 @@ static const struct bpf_sec_def section_defs[] = {
.is_attach_btf = true,
.expected_attach_type = BPF_LSM_MAC,
.attach_fn = attach_lsm),
+ SEC_DEF("dump/", TRACING,
+ .expected_attach_type = BPF_TRACE_DUMP),
BPF_PROG_SEC("xdp", BPF_PROG_TYPE_XDP),
BPF_PROG_SEC("perf_event", BPF_PROG_TYPE_PERF_EVENT),
BPF_PROG_SEC("lwt_in", BPF_PROG_TYPE_LWT_IN),
@@ -6401,6 +6424,23 @@ static const struct bpf_sec_def *find_sec_def(const char *sec_name)
return NULL;
}

+static int fill_dumper_info(struct bpf_program *prog)
+{
+ const struct bpf_sec_def *sec;
+ const char *dump_target;
+ int fd;
+
+ sec = find_sec_def(bpf_program__title(prog, false));
+ if (sec) {
+ dump_target = bpf_program__title(prog, false) + sec->len;
+ fd = open(dump_target, O_RDONLY);
+ if (fd < 0)
+ return fd;
+ prog->attach_prog_fd = fd;
+ }
+ return 0;
+}
+
static char *libbpf_get_type_names(bool attach_type)
{
int i, len = ARRAY_SIZE(section_defs) * MAX_TYPE_NAME_SIZE;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 44df1d3e7287..ccb5d30fff4a 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -216,6 +216,7 @@ LIBBPF_API int bpf_program__unpin_instance(struct bpf_program *prog,
LIBBPF_API int bpf_program__pin(struct bpf_program *prog, const char *path);
LIBBPF_API int bpf_program__unpin(struct bpf_program *prog, const char *path);
LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
+LIBBPF_API int bpf_program__pin_dumper(struct bpf_program *prog, const char *dname);

struct bpf_link;

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index bb8831605b25..ed6234bb199f 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -238,6 +238,7 @@ LIBBPF_0.0.7 {

LIBBPF_0.0.8 {
global:
+ bpf_dump_query;
bpf_link__fd;
bpf_link__open;
bpf_link__pin;
@@ -248,8 +249,10 @@ LIBBPF_0.0.8 {
bpf_link_update;
bpf_map__set_initial_value;
bpf_program__attach_cgroup;
+ bpf_obj_pin_dumper;
bpf_program__attach_lsm;
bpf_program__is_lsm;
+ bpf_program__pin_dumper;
bpf_program__set_attach_target;
bpf_program__set_lsm;
bpf_set_link_xdp_fd_opts;
--
2.24.1