linux.git/tools/lib/bpf/libbpf_internal.h, branch v5.13

libbpf: Provide GELF_ST_VISIBILITY() define for older libelf

2021-05-11T21:07:33+00:00

Where that macro isn't available.

Signed-off-by: Arnaldo Carvalho de Melo 
Signed-off-by: Daniel Borkmann 
Link: https://lore.kernel.org/bpf/YJaspEh0qZr4LYOc@kernel.org

libbpf: Make few internal helpers available outside of libbpf.c

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

Make skip_mods_and_typedefs(), btf_kind_str(), and btf_func_linkage() helpers
available outside of libbpf.c, to be used by static linker code.

Also do few cleanups (error code fixes, comment clean up, etc) that don't
deserve their own commit.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/bpf/20210423181348.1801389-9-andrii@kernel.org

libbpf: Refactor BTF map definition parsing

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

Refactor BTF-defined maps parsing logic to allow it to be nicely reused by BPF
static linker. Further, at least for BPF static linker, it's important to know
which attributes of a BPF map were defined explicitly, so provide a bit set
for each known portion of BTF map definition. This allows BPF static linker to
do a simple check when dealing with extern map declarations.

The same capabilities allow to distinguish attributes explicitly set to zero
(e.g., __uint(max_entries, 0)) vs the case of not specifying it at all (no
max_entries attribute at all). Libbpf is currently not utilizing that, but it
could be useful for backwards compatibility reasons later.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/bpf/20210423181348.1801389-7-andrii@kernel.org

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 BPF static linker APIs

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

Introduce BPF static linker APIs to libbpf. BPF static linker allows to
perform static linking of multiple BPF object files into a single combined
resulting object file, preserving all the BPF programs, maps, global
variables, etc.

Data sections (.bss, .data, .rodata, .maps, maps, etc) with the same name are
concatenated together. Similarly, code sections are also concatenated. All the
symbols and ELF relocations are also concatenated in their respective ELF
sections and are adjusted accordingly to the new object file layout.

Static variables and functions are handled correctly as well, adjusting BPF
instructions offsets to reflect new variable/function offset within the
combined ELF section. Such relocations are referencing STT_SECTION symbols and
that stays intact.

Data sections in different files can have different alignment requirements, so
that is taken care of as well, adjusting sizes and offsets as necessary to
satisfy both old and new alignment requirements.

DWARF data sections are stripped out, currently. As well as LLLVM_ADDRSIG
section, which is ignored by libbpf in bpf_object__open() anyways. So, in
a way, BPF static linker is an analogue to `llvm-strip -g`, which is a pretty
nice property, especially if resulting .o file is then used to generate BPF
skeleton.

Original string sections are ignored and instead we construct our own set of
unique strings using libbpf-internal `struct strset` API.

To reduce the size of the patch, all the .BTF and .BTF.ext processing was
moved into a separate patch.

The high-level API consists of just 4 functions:
  - bpf_linker__new() creates an instance of BPF static linker. It accepts
    output filename and (currently empty) options struct;
  - bpf_linker__add_file() takes input filename and appends it to the already
    processed ELF data; it can be called multiple times, one for each BPF
    ELF object file that needs to be linked in;
  - bpf_linker__finalize() needs to be called to dump final ELF contents into
    the output file, specified when bpf_linker was created; after
    bpf_linker__finalize() is called, no more bpf_linker__add_file() and
    bpf_linker__finalize() calls are allowed, they will return error;
  - regardless of whether bpf_linker__finalize() was called or not,
    bpf_linker__free() will free up all the used resources.

Currently, BPF static linker doesn't resolve cross-object file references
(extern variables and/or functions). This will be added in the follow up patch
set.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20210318194036.3521577-7-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: Support attachment of BPF tracing programs to kernel modules

2020-12-04T01:38:21+00:00

Teach libbpf to search for BTF types in kernel modules for tracing BPF
programs. This allows attachment of raw_tp/fentry/fexit/fmod_ret/etc BPF
program types to tracepoints and functions in kernel modules.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20201203204634.1325171-13-andrii@kernel.org