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authorAndrii Nakryiko <andrii@kernel.org>2020-12-03 12:46:23 -0800
committerAlexei Starovoitov <ast@kernel.org>2020-12-03 17:38:20 -0800
commita19f93cfafdf85851c69bc9f677aa4f40c53610f (patch)
tree08c46ad0d0f0a2f5ec14b0257d475edc6f719d6c /tools/lib/bpf
parent2fe8890848c799515a881502339a0a7b2b555988 (diff)
libbpf: Add internal helper to load BTF data by FD
Add a btf_get_from_fd() helper, which constructs struct btf from in-kernel BTF data by FD. This is used for loading module BTFs. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20201203204634.1325171-4-andrii@kernel.org
Diffstat (limited to 'tools/lib/bpf')
-rw-r--r--tools/lib/bpf/btf.c61
-rw-r--r--tools/lib/bpf/libbpf_internal.h1
2 files changed, 36 insertions, 26 deletions
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 1935e83d309c..3c3f2bc6c652 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1323,35 +1323,27 @@ const char *btf__name_by_offset(const struct btf *btf, __u32 offset)
return btf__str_by_offset(btf, offset);
}
-int btf__get_from_id(__u32 id, struct btf **btf)
+struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf)
{
- struct bpf_btf_info btf_info = { 0 };
+ struct bpf_btf_info btf_info;
__u32 len = sizeof(btf_info);
__u32 last_size;
- int btf_fd;
+ struct btf *btf;
void *ptr;
int err;
- err = 0;
- *btf = NULL;
- btf_fd = bpf_btf_get_fd_by_id(id);
- if (btf_fd < 0)
- return 0;
-
/* we won't know btf_size until we call bpf_obj_get_info_by_fd(). so
* let's start with a sane default - 4KiB here - and resize it only if
* bpf_obj_get_info_by_fd() needs a bigger buffer.
*/
- btf_info.btf_size = 4096;
- last_size = btf_info.btf_size;
+ last_size = 4096;
ptr = malloc(last_size);
- if (!ptr) {
- err = -ENOMEM;
- goto exit_free;
- }
+ if (!ptr)
+ return ERR_PTR(-ENOMEM);
- memset(ptr, 0, last_size);
+ memset(&btf_info, 0, sizeof(btf_info));
btf_info.btf = ptr_to_u64(ptr);
+ btf_info.btf_size = last_size;
err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len);
if (!err && btf_info.btf_size > last_size) {
@@ -1360,31 +1352,48 @@ int btf__get_from_id(__u32 id, struct btf **btf)
last_size = btf_info.btf_size;
temp_ptr = realloc(ptr, last_size);
if (!temp_ptr) {
- err = -ENOMEM;
+ btf = ERR_PTR(-ENOMEM);
goto exit_free;
}
ptr = temp_ptr;
- memset(ptr, 0, last_size);
+
+ len = sizeof(btf_info);
+ memset(&btf_info, 0, sizeof(btf_info));
btf_info.btf = ptr_to_u64(ptr);
+ btf_info.btf_size = last_size;
+
err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len);
}
if (err || btf_info.btf_size > last_size) {
- err = errno;
+ btf = err ? ERR_PTR(-errno) : ERR_PTR(-E2BIG);
goto exit_free;
}
- *btf = btf__new((__u8 *)(long)btf_info.btf, btf_info.btf_size);
- if (IS_ERR(*btf)) {
- err = PTR_ERR(*btf);
- *btf = NULL;
- }
+ btf = btf_new(ptr, btf_info.btf_size, base_btf);
exit_free:
- close(btf_fd);
free(ptr);
+ return btf;
+}
- return err;
+int btf__get_from_id(__u32 id, struct btf **btf)
+{
+ struct btf *res;
+ int btf_fd;
+
+ *btf = NULL;
+ btf_fd = bpf_btf_get_fd_by_id(id);
+ if (btf_fd < 0)
+ return -errno;
+
+ res = btf_get_from_fd(btf_fd, NULL);
+ close(btf_fd);
+ if (IS_ERR(res))
+ return PTR_ERR(res);
+
+ *btf = res;
+ return 0;
}
int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index d99bc847bf84..e569ae63808e 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -155,6 +155,7 @@ int bpf_object__section_size(const struct bpf_object *obj, const char *name,
__u32 *size);
int bpf_object__variable_offset(const struct bpf_object *obj, const char *name,
__u32 *off);
+struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf);
struct btf_ext_info {
/*