Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
libbpf: Add layout encoding support
Support encoding of BTF layout data via btf__new_empty_opts().
Current supported opts are base_btf and add_layout.
Layout information is maintained in btf.c in the layouts[] array;
when BTF is created with the add_layout option it represents the
current view of supported BTF kinds.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260326145444.2076244-5-alan.maguire@oracle.com
authored by
Alan Maguire
and committed by
Andrii Nakryiko
d686d92c
2ecbe53e
+83
-2
+61
-2
tools/lib/bpf/btf.c
+61
-2
tools/lib/bpf/btf.c
···
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static struct btf_type btf_void;
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/*
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* Describe how kinds are laid out; some have a singular element following the "struct btf_type",
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* some have BTF_INFO_VLEN(t->info) elements. Specify sizes for both. Flags are currently unused.
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* Kind layout can be optionally added to the BTF representation in a dedicated section to
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* facilitate parsing. New kinds must be added here.
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*/
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static struct btf_layout layouts[NR_BTF_KINDS] = {
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/* singular element size vlen element(s) size flags */
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[BTF_KIND_UNKN] = { 0, 0, 0 },
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[BTF_KIND_INT] = { sizeof(__u32), 0, 0 },
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[BTF_KIND_PTR] = { 0, 0, 0 },
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[BTF_KIND_ARRAY] = { sizeof(struct btf_array), 0, 0 },
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[BTF_KIND_STRUCT] = { 0, sizeof(struct btf_member), 0 },
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[BTF_KIND_UNION] = { 0, sizeof(struct btf_member), 0 },
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[BTF_KIND_ENUM] = { 0, sizeof(struct btf_enum), 0 },
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[BTF_KIND_FWD] = { 0, 0, 0 },
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[BTF_KIND_TYPEDEF] = { 0, 0, 0 },
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[BTF_KIND_VOLATILE] = { 0, 0, 0 },
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[BTF_KIND_CONST] = { 0, 0, 0 },
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[BTF_KIND_RESTRICT] = { 0, 0, 0 },
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[BTF_KIND_FUNC] = { 0, 0, 0 },
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[BTF_KIND_FUNC_PROTO] = { 0, sizeof(struct btf_param), 0 },
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[BTF_KIND_VAR] = { sizeof(struct btf_var), 0, 0 },
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[BTF_KIND_DATASEC] = { 0, sizeof(struct btf_var_secinfo), 0 },
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[BTF_KIND_FLOAT] = { 0, 0, 0 },
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[BTF_KIND_DECL_TAG] = { sizeof(struct btf_decl_tag), 0, 0 },
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[BTF_KIND_TYPE_TAG] = { 0, 0, 0 },
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[BTF_KIND_ENUM64] = { 0, sizeof(struct btf_enum64), 0 },
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};
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struct btf {
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/* raw BTF data in native endianness */
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void *raw_data;
···
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free(btf);
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}
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-
static struct btf *btf_new_empty(struct btf *base_btf)
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static struct btf *btf_new_empty(struct btf_new_opts *opts)
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{
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bool add_layout = OPTS_GET(opts, add_layout, false);
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struct btf *base_btf = OPTS_GET(opts, base_btf, NULL);
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struct btf_header *hdr;
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struct btf *btf;
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···
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/* +1 for empty string at offset 0 */
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btf->raw_size = sizeof(struct btf_header) + (base_btf ? 0 : 1);
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if (add_layout)
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btf->raw_size += sizeof(layouts);
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btf->raw_data = calloc(1, btf->raw_size);
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if (!btf->raw_data) {
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free(btf);
···
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btf->types_data = btf->raw_data + hdr->hdr_len;
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btf->strs_data = btf->raw_data + hdr->hdr_len;
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hdr->str_len = base_btf ? 0 : 1; /* empty string at offset 0 */
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if (add_layout) {
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hdr->layout_len = sizeof(layouts);
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btf->layout = layouts;
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/*
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* No need to swap endianness here as btf_get_raw_data()
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* will do this for us if btf->swapped_endian is true.
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*/
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memcpy(btf->raw_data + hdr->hdr_len, layouts, sizeof(layouts));
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btf->strs_data += sizeof(layouts);
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hdr->str_off += sizeof(layouts);
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}
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memcpy(&btf->hdr, hdr, sizeof(*hdr));
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return btf;
···
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struct btf *btf__new_empty_split(struct btf *base_btf)
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{
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return libbpf_ptr(btf_new_empty(base_btf));
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LIBBPF_OPTS(btf_new_opts, opts);
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opts.base_btf = base_btf;
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return libbpf_ptr(btf_new_empty(&opts));
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}
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struct btf *btf__new_empty_opts(struct btf_new_opts *opts)
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{
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if (!OPTS_VALID(opts, btf_new_opts))
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return libbpf_err_ptr(-EINVAL);
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return libbpf_ptr(btf_new_empty(opts));
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}
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static struct btf *btf_new(const void *data, __u32 size, struct btf *base_btf, bool is_mmap)
+20
tools/lib/bpf/btf.h
+20
tools/lib/bpf/btf.h
···
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*/
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LIBBPF_API struct btf *btf__new_empty_split(struct btf *base_btf);
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struct btf_new_opts {
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size_t sz;
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struct btf *base_btf; /* optional base BTF */
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bool add_layout; /* add BTF layout information */
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size_t:0;
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};
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#define btf_new_opts__last_field add_layout
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/**
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* @brief **btf__new_empty_opts()** creates an unpopulated BTF object with
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* optional *base_btf* and BTF kind layout description if *add_layout*
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* is set
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* @return new BTF object instance which has to be eventually freed with
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* **btf__free()**
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*
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* On error, NULL is returned and the thread-local `errno` variable is
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* set to the error code.
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*/
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LIBBPF_API struct btf *btf__new_empty_opts(struct btf_new_opts *opts);
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/**
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* @brief **btf__distill_base()** creates new versions of the split BTF
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* *src_btf* and its base BTF. The new base BTF will only contain the types