linux.git/tools/lib/bpf/btf.c, branch v5.13

libbpf: Mark BPF subprogs with hidden visibility as static for BPF verifier

2021-04-23T21:05:26+00:00

Define __hidden helper macro in bpf_helpers.h, which is a short-hand for
__attribute__((visibility("hidden"))). Add libbpf support to mark BPF
subprograms marked with __hidden as static in BTF information to enforce BPF
verifier's static function validation algorithm, which takes more information
(caller's context) into account during a subprogram validation.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/bpf/20210423181348.1801389-5-andrii@kernel.org

libbpf: Add generic BTF type shallow copy API

2021-03-18T23:14:22+00:00

Add btf__add_type() API that performs shallow copy of a given BTF type from
the source BTF into the destination BTF. All the information and type IDs are
preserved, but all the strings encountered are added into the destination BTF
and corresponding offsets are rewritten. BTF type IDs are assumed to be
correct or such that will be (somehow) modified afterwards.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20210318194036.3521577-6-andrii@kernel.org

libbpf: Extract internal set-of-strings datastructure APIs

2021-03-18T23:14:22+00:00

Extract BTF logic for maintaining a set of strings data structure, used for
BTF strings section construction in writable mode, into separate re-usable
API. This data structure is going to be used by bpf_linker to maintains ELF
STRTAB section, which has the same layout as BTF strings section.

Suggested-by: Alexei Starovoitov 
Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20210318194036.3521577-5-andrii@kernel.org

libbpf: Rename internal memory-management helpers

2021-03-18T23:14:22+00:00

Rename btf_add_mem() and btf_ensure_mem() helpers that abstract away details
of dynamically resizable memory to use libbpf_ prefix, as they are not
BTF-specific. No functional changes.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20210318194036.3521577-4-andrii@kernel.org

libbpf: Generalize BTF and BTF.ext type ID and strings iteration

2021-03-18T23:14:22+00:00

Extract and generalize the logic to iterate BTF type ID and string offset
fields within BTF types and .BTF.ext data. Expose this internally in libbpf
for re-use by bpf_linker.

Additionally, complete strings deduplication handling for BTF.ext (e.g., CO-RE
access strings), which was previously missing. There previously was no
case of deduplicating .BTF.ext data, but bpf_linker is going to use it.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20210318194036.3521577-3-andrii@kernel.org

libbpf: Expose btf_type_by_id() internally

2021-03-18T23:14:22+00:00

btf_type_by_id() is internal-only convenience API returning non-const pointer
to struct btf_type. Expose it outside of btf.c for re-use.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20210318194036.3521577-2-andrii@kernel.org

libbpf: Add BTF_KIND_FLOAT support

2021-03-05T01:58:15+00:00

The logic follows that of BTF_KIND_INT most of the time. Sanitization
replaces BTF_KIND_FLOATs with equally-sized empty BTF_KIND_STRUCTs on
older kernels, for example, the following:

    [4] FLOAT 'float' size=4

becomes the following:

    [4] STRUCT '(anon)' size=4 vlen=0

With dwarves patch [1] and this patch, the older kernels, which were
failing with the floating-point-related errors, will now start working
correctly.

[1] https://github.com/iii-i/dwarves/commit/btf-kind-float-v2

Signed-off-by: Ilya Leoshkevich 
Signed-off-by: Alexei Starovoitov 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20210226202256.116518-4-iii@linux.ibm.com

libbpf: Fix whitespace in btf_add_composite() comment

2021-03-05T01:58:15+00:00

Remove trailing space.

Signed-off-by: Ilya Leoshkevich 
Signed-off-by: Alexei Starovoitov 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/bpf/20210226202256.116518-3-iii@linux.ibm.com

libbpf: Use string table index from index table if needed

2021-01-21T23:38:01+00:00

For very large ELF objects (with many sections), we could
get special value SHN_XINDEX (65535) for elf object's string
table index - e_shstrndx.

Call elf_getshdrstrndx to get the proper string table index,
instead of reading it directly from ELF header.

Signed-off-by: Jiri Olsa 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20210121202203.9346-4-jolsa@kernel.org

libbpf: Allow loading empty BTFs

2021-01-12T20:12:05+00:00

Empty BTFs do come up (e.g., simple kernel modules with no new types and
strings, compared to the vmlinux BTF) and there is nothing technically wrong
with them. So remove unnecessary check preventing loading empty BTFs.

Fixes: d8123624506c ("libbpf: Fix BTF data layout checks and allow empty BTF")
Reported-by: Christopher William Snowhill 
Signed-off-by: Andrii Nakryiko 
Signed-off-by: Daniel Borkmann 
Link: https://lore.kernel.org/bpf/20210110070341.1380086-2-andrii@kernel.org