From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>, <ast@fb.com>,
<daniel@iogearbox.net>
Cc: <andrii@kernel.org>, <kernel-team@fb.com>
Subject: [PATCH v3 bpf-next 2/7] libbpf: add internal helper to load BTF data by FD
Date: Mon, 30 Nov 2020 19:47:03 -0800 [thread overview]
Message-ID: <20201201034709.2918694-3-andrii@kernel.org> (raw)
In-Reply-To: <20201201034709.2918694-1-andrii@kernel.org>
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>
---
tools/lib/bpf/btf.c | 61 +++++++++++++++++++--------------
tools/lib/bpf/libbpf_internal.h | 1 +
2 files changed, 36 insertions(+), 26 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 8ff46cd30ca1..affea8318feb 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1318,35 +1318,27 @@ 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) {
@@ -1355,31 +1347,48 @@ 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 {
/*
--
2.24.1
next prev parent reply other threads:[~2020-12-01 3:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-01 3:47 [PATCH v3 bpf-next 0/7] libbpf: add support for kernel module BTF CO-RE relocations Andrii Nakryiko
2020-12-01 3:47 ` [PATCH v3 bpf-next 1/7] bpf: fix bpf_put_raw_tracepoint()'s use of __module_address() Andrii Nakryiko
2020-12-01 3:47 ` Andrii Nakryiko [this message]
2020-12-01 3:47 ` [PATCH v3 bpf-next 3/7] libbpf: refactor CO-RE relocs to not assume a single BTF object Andrii Nakryiko
2020-12-01 3:47 ` [PATCH v3 bpf-next 4/7] libbpf: add kernel module BTF support for CO-RE relocations Andrii Nakryiko
2020-12-01 3:47 ` [PATCH v3 bpf-next 5/7] selftests/bpf: add bpf_testmod kernel module for testing Andrii Nakryiko
2020-12-01 3:47 ` [PATCH v3 bpf-next 6/7] selftests/bpf: add support for marking sub-tests as skipped Andrii Nakryiko
2020-12-01 3:47 ` [PATCH v3 bpf-next 7/7] selftests/bpf: add CO-RE relocs selftest relying on kernel module BTF Andrii Nakryiko
2020-12-01 21:29 ` [PATCH v3 bpf-next 0/7] libbpf: add support for kernel module BTF CO-RE relocations Alexei Starovoitov
2020-12-01 21:49 ` Andrii Nakryiko
2020-12-01 22:22 ` Alexei Starovoitov
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