__BYTE_ORDER is supposed to be defined by a libc, and __BYTE_ORDER__ -
by a compiler. bpf_core_read.h checks __BYTE_ORDER == __LITTLE_ENDIAN,
which is true if neither are defined, leading to incorrect behavior on
big-endian hosts if libc headers are not included, which is often the
case.
Fixes: ee26dade0e3b ("libbpf: Add support for relocatable bitfields")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211026010831.748682-2-iii@linux.ibm.com
The name of the API doesn't convey clearly that this size is in number
of bytes (there needed to be a separate comment to make this clear in
libbpf.h). Further, measuring the size of BPF program in bytes is not
exactly the best fit, because BPF programs always consist of 8-byte
instructions. As such, bpf_program__insn_cnt() is a better alternative
in pretty much any imaginable case.
So schedule bpf_program__size() deprecation starting from v0.7 and it
will be removed in libbpf 1.0.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211025224531.1088894-5-andrii@kernel.org
Schedule deprecation of a set of APIs that are related to multi-instance
bpf_programs:
- bpf_program__set_prep() ([0]);
- bpf_program__{set,unset}_instance() ([1]);
- bpf_program__nth_fd().
These APIs are obscure, very niche, and don't seem to be used much in
practice. bpf_program__set_prep() is pretty useless for anything but the
simplest BPF programs, as it doesn't allow to adjust BPF program load
attributes, among other things. In short, it already bitrotted and will
bitrot some more if not removed.
With bpf_program__insns() API, which gives access to post-processed BPF
program instructions of any given entry-point BPF program, it's now
possible to do whatever necessary adjustments were possible with
set_prep() API before, but also more. Given any such use case is
automatically an advanced use case, requiring users to stick to
low-level bpf_prog_load() APIs and managing their own prog FDs is
reasonable.
[0] Closes: https://github.com/libbpf/libbpf/issues/299
[1] Closes: https://github.com/libbpf/libbpf/issues/300
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211025224531.1088894-4-andrii@kernel.org
Add APIs providing read-only access to bpf_program BPF instructions ([0]).
This is useful for diagnostics purposes, but it also allows a cleaner
support for cloning BPF programs after libbpf did all the FD resolution
and CO-RE relocations, subprog instructions appending, etc. Currently,
cloning BPF program is possible only through hijacking a half-broken
bpf_program__set_prep() API, which doesn't really work well for anything
but most primitive programs. For instance, set_prep() API doesn't allow
adjusting BPF program load parameters which are necessary for loading
fentry/fexit BPF programs (the case where BPF program cloning is
a necessity if doing some sort of mass-attachment functionality).
Given bpf_program__set_prep() API is set to be deprecated, having
a cleaner alternative is a must. libbpf internally already keeps track
of linear array of struct bpf_insn, so it's not hard to expose it. The
only gotcha is that libbpf previously freed instructions array during
bpf_object load time, which would make this API much less useful overall,
because in between bpf_object__open() and bpf_object__load() a lot of
changes to instructions are done by libbpf.
So this patch makes libbpf hold onto prog->insns array even after BPF
program loading. I think this is a small price for added functionality
and improved introspection of BPF program code.
See retsnoop PR ([1]) for how it can be used in practice and code
savings compared to relying on bpf_program__set_prep().
[0] Closes: https://github.com/libbpf/libbpf/issues/298
[1] https://github.com/anakryiko/retsnoop/pull/1
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211025224531.1088894-3-andrii@kernel.org
The sync-kernel.sh script has two consecutive tests for $BPF_BRANCH
being provided by the user (and so the second one can currently never
fail). Looking at the error message displayed in each case, we want to
keep the second one. Let's remove the first check.
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
The commit_signature() function does not use the hash of the commit,
which typically differs between the kernel repo and the mirrored
version, but the subject for this commit. Fix the comment accordingly.
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Original code assumed fixed and correct BTF header length. That's not
always the case, though, so fix this bug with a proper additional check.
And use actual header length instead of sizeof(struct btf_header) in
sanity checks.
Fixes: 8a138aed4a80 ("bpf: btf: Add BTF support to libbpf")
Reported-by: Evgeny Vereshchagin <evvers@ya.ru>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211023003157.726961-2-andrii@kernel.org
btf_header's str_off+str_len or type_off+type_len can overflow as they
are u32s. This will lead to bypassing the sanity checks during BTF
parsing, resulting in crashes afterwards. Fix by using 64-bit signed
integers for comparison.
Fixes: d8123624506c ("libbpf: Fix BTF data layout checks and allow empty BTF")
Reported-by: Evgeny Vereshchagin <evvers@ya.ru>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211023003157.726961-1-andrii@kernel.org
Building libbpf sources out of kernel tree (in Github repo) we run into
compilation error due to unknown __aligned attribute. It must be coming
from some kernel header, which is not available to Github sources. Use
explicit __attribute__((aligned(16))) instead.
Fixes: 961632d54163 ("libbpf: Fix dumping non-aligned __int128")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211022192502.2975553-1-andrii@kernel.org
Map name that's assigned to internal maps (.rodata, .data, .bss, etc)
consist of a small prefix of bpf_object's name and ELF section name as
a suffix. This makes it hard for users to "guess" the name to use for
looking up by name with bpf_object__find_map_by_name() API.
One proposal was to drop object name prefix from the map name and just
use ".rodata", ".data", etc, names. One downside called out was that
when multiple BPF applications are active on the host, it will be hard
to distinguish between multiple instances of .rodata and know which BPF
object (app) they belong to. Having few first characters, while quite
limiting, still can give a bit of a clue, in general.
Note, though, that btf_value_type_id for such global data maps (ARRAY)
points to DATASEC type, which encodes full ELF name, so tools like
bpftool can take advantage of this fact to "recover" full original name
of the map. This is also the reason why for custom .data.* and .rodata.*
maps libbpf uses only their ELF names and doesn't prepend object name at
all.
Another downside of such approach is that it is not backwards compatible
and, among direct use of bpf_object__find_map_by_name() API, will break
any BPF skeleton generated using bpftool that was compiled with older
libbpf version.
Instead of causing all this pain, libbpf will still generate map name
using a combination of object name and ELF section name, but it will
allow looking such maps up by their natural names, which correspond to
their respective ELF section names. This means non-truncated ELF section
names longer than 15 characters are going to be expected and supported.
With such set up, we get the best of both worlds: leave small bits of
a clue about BPF application that instantiated such maps, as well as
making it easy for user apps to lookup such maps at runtime. In this
sense it closes corresponding libbpf 1.0 issue ([0]).
BPF skeletons will continue using full names for lookups.
[0] Closes: https://github.com/libbpf/libbpf/issues/275
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211021014404.2635234-10-andrii@kernel.org
Add support for having multiple .rodata and .data data sections ([0]).
.rodata/.data are supported like the usual, but now also
.rodata.<whatever> and .data.<whatever> are also supported. Each such
section will get its own backing BPF_MAP_TYPE_ARRAY, just like
.rodata and .data.
Multiple .bss maps are not supported, as the whole '.bss' name is
confusing and might be deprecated soon, as well as user would need to
specify custom ELF section with SEC() attribute anyway, so might as well
stick to just .data.* and .rodata.* convention.
User-visible map name for such new maps is going to be just their ELF
section names.
[0] https://github.com/libbpf/libbpf/issues/274
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211021014404.2635234-8-andrii@kernel.org
Remove internal libbpf assumption that there can be only one .rodata,
.data, and .bss map per BPF object. To achieve that, extend and
generalize the scheme that was used for keeping track of relocation ELF
sections. Now each ELF section has a temporary extra index that keeps
track of logical type of ELF section (relocations, data, read-only data,
BSS). Switch relocation to this scheme, as well as .rodata/.data/.bss
handling.
We don't yet allow multiple .rodata, .data, and .bss sections, but no
libbpf internal code makes an assumption that there can be only one of
each and thus they can be explicitly referenced by a single index. Next
patches will actually allow multiple .rodata and .data sections.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211021014404.2635234-5-andrii@kernel.org
Minimize the usage of class-agnostic gelf_xxx() APIs from libelf. These
APIs require copying ELF data structures into local GElf_xxx structs and
have a more cumbersome API. BPF ELF file is defined to be always 64-bit
ELF object, even when intended to be run on 32-bit host architectures,
so there is no need to do class-agnostic conversions everywhere. BPF
static linker implementation within libbpf has been using Elf64-specific
types since initial implementation.
Add two simple helpers, elf_sym_by_idx() and elf_rel_by_idx(), for more
succinct direct access to ELF symbol and relocation records within ELF
data itself and switch all the GElf_xxx usage into Elf64_xxx
equivalents. The only remaining place within libbpf.c that's still using
gelf API is gelf_getclass(), as there doesn't seem to be a direct way to
get underlying ELF bitness.
No functional changes intended.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211021014404.2635234-4-andrii@kernel.org
There isn't a good use case where anyone but libbpf itself needs to call
btf__finalize_data(). It was implemented for internal use and it's not
clear why it was made into public API in the first place. To function, it
requires active ELF data, which is stored inside bpf_object for the
duration of opening phase only. But the only BTF that needs bpf_object's
ELF is that bpf_object's BTF itself, which libbpf fixes up automatically
during bpf_object__open() operation anyways. There is no need for any
additional fix up and no reasonable scenario where it's useful and
appropriate.
Thus, btf__finalize_data() is just an API atavism and is better removed.
So this patch marks it as deprecated immediately (v0.6+) and moves the
code from btf.c into libbpf.c where it's used in the context of
bpf_object opening phase. Such code co-location allows to make code
structure more straightforward and remove bpf_object__section_size() and
bpf_object__variable_offset() internal helpers from libbpf_internal.h,
making them static. Their naming is also adjusted to not create
a wrong illusion that they are some sort of method of bpf_object. They
are internal helpers and are called appropriately.
This is part of libbpf 1.0 effort ([0]).
[0] Closes: https://github.com/libbpf/libbpf/issues/276
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211021014404.2635234-2-andrii@kernel.org
Patch set [1] introduced BTF_KIND_TAG to allow tagging
declarations for struct/union, struct/union field, var, func
and func arguments and these tags will be encoded into
dwarf. They are also encoded to btf by llvm for the bpf target.
After BTF_KIND_TAG is introduced, we intended to use it
for kernel __user attributes. But kernel __user is actually
a type attribute. Upstream and internal discussion showed
it is not a good idea to mix declaration attribute and
type attribute. So we proposed to introduce btf_type_tag
as a type attribute and existing btf_tag renamed to
btf_decl_tag ([2]).
This patch renamed BTF_KIND_TAG to BTF_KIND_DECL_TAG and some
other declarations with *_tag to *_decl_tag to make it clear
the tag is for declaration. In the future, BTF_KIND_TYPE_TAG
might be introduced per [3].
[1] https://lore.kernel.org/bpf/20210914223004.244411-1-yhs@fb.com/
[2] https://reviews.llvm.org/D111588
[3] https://reviews.llvm.org/D111199
Fixes: b5ea834dde6b ("bpf: Support for new btf kind BTF_KIND_TAG")
Fixes: 5b84bd10363e ("libbpf: Add support for BTF_KIND_TAG")
Fixes: 5c07f2fec003 ("bpftool: Add support for BTF_KIND_TAG")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211012164838.3345699-1-yhs@fb.com
When fed an empty BPF object, bpftool gen skeleton -L crashes at
btf__set_fd() since it assumes presence of obj->btf, however for
the sequence below clang adds no .BTF section (hence no BTF).
Reproducer:
$ touch a.bpf.c
$ clang -O2 -g -target bpf -c a.bpf.c
$ bpftool gen skeleton -L a.bpf.o
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
/* THIS FILE IS AUTOGENERATED! */
struct a_bpf {
struct bpf_loader_ctx ctx;
Segmentation fault (core dumped)
The same occurs for files compiled without BTF info, i.e. without
clang's -g flag.
Fixes: 67234743736a (libbpf: Generate loader program out of BPF ELF file.)
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210930061634.1840768-1-memxor@gmail.com
Add a bulk copying api, btf__add_btf(), that speeds up and simplifies
appending entire contents of one BTF object to another one, taking care
of copying BTF type data, adjusting resulting BTF type IDs according to
their new locations in the destination BTF object, as well as copying
and deduplicating all the referenced strings and updating all the string
offsets in new BTF types as appropriate.
This API is intended to be used from tools that are generating and
otherwise manipulating BTFs generically, such as pahole. In pahole's
case, this API is useful for speeding up parallelized BTF encoding, as
it allows pahole to offload all the intricacies of BTF type copying to
libbpf and handle the parallelization aspects of the process.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Link: https://lore.kernel.org/bpf/20211006051107.17921-2-andrii@kernel.org
This change updates the BPF syscall loader to relocate BTF_KIND_FUNC
relocations, with support for weak kfunc relocations. The general idea
is to move map_fds to loader map, and also use the data for storing
kfunc BTF fds. Since both reuse the fd_array parameter, they need to be
kept together.
For map_fds, we reserve MAX_USED_MAPS slots in a region, and for kfunc,
we reserve MAX_KFUNC_DESCS. This is done so that insn->off has more
chances of being <= INT16_MAX than treating data map as a sparse array
and adding fd as needed.
When the MAX_KFUNC_DESCS limit is reached, we fall back to the sparse
array model, so that as long as it does remain <= INT16_MAX, we pass an
index relative to the start of fd_array.
We store all ksyms in an array where we try to avoid calling the
bpf_btf_find_by_name_kind helper, and also reuse the BTF fd that was
already stored. This also speeds up the loading process compared to
emitting calls in all cases, in later tests.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211002011757.311265-9-memxor@gmail.com
Preserve these calls as it allows verifier to succeed in loading the
program if they are determined to be unreachable after dead code
elimination during program load. If not, the verifier will fail at
runtime. This is done for ext->is_weak symbols similar to the case for
variable ksyms.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211002011757.311265-8-memxor@gmail.com
This patch adds libbpf support for kernel module function call support.
The fd_array parameter is used during BPF program load to pass module
BTFs referenced by the program. insn->off is set to index into this
array, but starts from 1, because insn->off as 0 is reserved for
btf_vmlinux.
We try to use existing insn->off for a module, since the kernel limits
the maximum distinct module BTFs for kfuncs to 256, and also because
index must never exceed the maximum allowed value that can fit in
insn->off (INT16_MAX). In the future, if kernel interprets signed offset
as unsigned for kfunc calls, this limit can be increased to UINT16_MAX.
Also introduce a btf__find_by_name_kind_own helper to start searching
from module BTF's start id when we know that the BTF ID is not present
in vmlinux BTF (in find_ksym_btf_id).
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211002011757.311265-7-memxor@gmail.com
When the loader indicates an internal error (result of a checked bpf
system call), it returns the result in attr.test.retval. However, tests
that rely on ASSERT_OK_PTR on NULL (returned from light skeleton) may
miss that NULL denotes an error if errno is set to 0. This would result
in skel pointer being NULL, while ASSERT_OK_PTR returning 1, leading to
a SEGV on dereference of skel, because libbpf_get_error relies on the
assumption that errno is always set in case of error for ptr == NULL.
In particular, this was observed for the ksyms_module test. When
executed using `./test_progs -t ksyms`, prior tests manipulated errno
and the test didn't crash when it failed at ksyms_module load, while
using `./test_progs -t ksyms_module` crashed due to errno being
untouched.
Fixes: 67234743736a (libbpf: Generate loader program out of BPF ELF file.)
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210927145941.1383001-11-memxor@gmail.com
The previous patch to ignore STT_SECTION symbols only added the ignore
condition in one of them. This fails if there's more than one map
definition in the 'maps' section, because the subsequent modulus check will
fail, resulting in error messages like:
libbpf: elf: unable to determine legacy map definition size in ./xdpdump_xdp.o
Fix this by also ignoring STT_SECTION in the first loop.
Fixes: c3e8c44a9063 ("libbpf: Ignore STT_SECTION symbols in 'maps' section")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210929213837.832449-1-toke@redhat.com
Initial idea was to run it hourly, but when it runs hourly it produce a
lot of useless noise and we had to switch it do daily. When we run it
daily caching make much less sense and only make debugging more complex.
