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From: Andrii Nakryiko <andriin@fb.com>
To: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>, <ast@fb.com>,
	<daniel@iogearbox.net>
Cc: <andrii.nakryiko@gmail.com>, <kernel-team@fb.com>,
	Andrii Nakryiko <andriin@fb.com>,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	John Fastabend <john.fastabend@gmail.com>
Subject: [PATCH v2 bpf-next 6/9] libbpf: add btf__new_empty() to create an empty BTF object
Date: Fri, 25 Sep 2020 18:13:54 -0700	[thread overview]
Message-ID: <20200926011357.2366158-7-andriin@fb.com> (raw)
In-Reply-To: <20200926011357.2366158-1-andriin@fb.com>

Add an ability to create an empty BTF object from scratch. This is going to be
used by pahole for BTF encoding. And also by selftest for convenient creation
of BTF objects.

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/lib/bpf/btf.c      | 30 ++++++++++++++++++++++++++++++
 tools/lib/bpf/btf.h      |  1 +
 tools/lib/bpf/libbpf.map |  1 +
 3 files changed, 32 insertions(+)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 040f3b8ee39f..54861a5ba9d9 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -565,6 +565,36 @@ void btf__free(struct btf *btf)
 	free(btf);
 }
 
+struct btf *btf__new_empty(void)
+{
+	struct btf *btf;
+
+	btf = calloc(1, sizeof(*btf));
+	if (!btf)
+		return ERR_PTR(-ENOMEM);
+	btf->fd = -1;
+	btf->ptr_sz = sizeof(void *);
+
+	/* +1 for empty string at offset 0 */
+	btf->raw_size = sizeof(struct btf_header) + 1;
+	btf->raw_data = calloc(1, btf->raw_size);
+	if (!btf->raw_data) {
+		free(btf);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	btf->hdr = btf->raw_data;
+	btf->hdr->hdr_len = sizeof(struct btf_header);
+	btf->hdr->magic = BTF_MAGIC;
+	btf->hdr->version = BTF_VERSION;
+
+	btf->types_data = btf->raw_data + btf->hdr->hdr_len;
+	btf->strs_data = btf->raw_data + btf->hdr->hdr_len;
+	btf->hdr->str_len = 1; /* empty string at offset 0 */
+
+	return btf;
+}
+
 struct btf *btf__new(const void *data, __u32 size)
 {
 	struct btf *btf;
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index d88b6447c222..b387d0b61f1c 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -27,6 +27,7 @@ struct bpf_object;
 
 LIBBPF_API void btf__free(struct btf *btf);
 LIBBPF_API struct btf *btf__new(const void *data, __u32 size);
+LIBBPF_API struct btf *btf__new_empty(void);
 LIBBPF_API struct btf *btf__parse(const char *path, struct btf_ext **btf_ext);
 LIBBPF_API struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext);
 LIBBPF_API struct btf *btf__parse_raw(const char *path);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index c38aca688a39..6e75cb0e1b17 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -306,6 +306,7 @@ LIBBPF_0.2.0 {
 		bpf_program__section_name;
 		btf__add_str;
 		btf__find_str;
+		btf__new_empty;
 		perf_buffer__buffer_cnt;
 		perf_buffer__buffer_fd;
 		perf_buffer__epoll_fd;
-- 
2.24.1


  parent reply	other threads:[~2020-09-26  1:14 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-26  1:13 [PATCH v2 bpf-next 0/9] libbpf: BTF writer APIs Andrii Nakryiko
2020-09-26  1:13 ` [PATCH v2 bpf-next 1/9] libbpf: refactor internals of BTF type index Andrii Nakryiko
2020-09-26  1:13 ` [PATCH v2 bpf-next 2/9] libbpf: remove assumption of single contiguous memory for BTF data Andrii Nakryiko
2020-09-26  1:13 ` [PATCH v2 bpf-next 3/9] libbpf: generalize common logic for managing dynamically-sized arrays Andrii Nakryiko
2020-09-26  1:13 ` [PATCH v2 bpf-next 4/9] libbpf: extract generic string hashing function for reuse Andrii Nakryiko
2020-09-26  1:13 ` [PATCH v2 bpf-next 5/9] libbpf: allow modification of BTF and add btf__add_str API Andrii Nakryiko
2020-09-26  1:13 ` Andrii Nakryiko [this message]
2020-09-26  1:13 ` [PATCH v2 bpf-next 7/9] libbpf: add BTF writing APIs Andrii Nakryiko
2020-09-29  0:33   ` Alexei Starovoitov
2020-09-26  1:13 ` [PATCH v2 bpf-next 8/9] libbpf: add btf__str_by_offset() as a more generic variant of name_by_offset Andrii Nakryiko
2020-09-26  1:13 ` [PATCH v2 bpf-next 9/9] selftests/bpf: test BTF writing APIs Andrii Nakryiko

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