linux.git/tools/lib/bpf/bpf.c, branch v5.16

libbpf: Fix lookup_and_delete_elem_flags error reporting

2021-11-05T15:26:08+00:00

Fix bpf_map_lookup_and_delete_elem_flags() to pass the return code through
libbpf_err_errno() as we do similarly in bpf_map_lookup_and_delete_elem().

Fixes: f12b65432728 ("libbpf: Streamline error reporting for low-level APIs")
Signed-off-by: Mehrdad Arshad Rad 
Signed-off-by: Daniel Borkmann 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/bpf/20211104171354.11072-1-arshad.rad@gmail.com

libbpf: Ensure that BPF syscall fds are never 0, 1, or 2

2021-10-28T23:30:07+00:00

Add a simple wrapper for passing an fd and getting a new one >= 3 if it
is one of 0, 1, or 2. There are two primary reasons to make this change:
First, libbpf relies on the assumption a certain BPF fd is never 0 (e.g.
most recently noticed in [0]). Second, Alexei pointed out in [1] that
some environments reset stdin, stdout, and stderr if they notice an
invalid fd at these numbers. To protect against both these cases, switch
all internal BPF syscall wrappers in libbpf to always return an fd >= 3.
We only need to modify the syscall wrappers and not other code that
assumes a valid fd by doing >= 0, to avoid pointless churn, and because
it is still a valid assumption. The cost paid is two additional syscalls
if fd is in range [0, 2].

  [0]: e31eec77e4ab ("bpf: selftests: Fix fd cleanup in get_branch_snapshot")
  [1]: https://lore.kernel.org/bpf/CAADnVQKVKY8o_3aU8Gzke443+uHa-eGoM0h7W4srChMXU1S4Bg@mail.gmail.com

Signed-off-by: Kumar Kartikeya Dwivedi 
Signed-off-by: Alexei Starovoitov 
Acked-by: Song Liu 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20211028063501.2239335-5-memxor@gmail.com

libbpf: Add "map_extra" as a per-map-type extra flag

2021-10-28T20:22:49+00:00

This patch adds the libbpf infrastructure for supporting a
per-map-type "map_extra" field, whose definition will be
idiosyncratic depending on map type.

For example, for the bloom filter map, the lower 4 bits of
map_extra is used to denote the number of hash functions.

Please note that until libbpf 1.0 is here, the
"bpf_create_map_params" struct is used as a temporary
means for propagating the map_extra field to the kernel.

Signed-off-by: Joanne Koong 
Signed-off-by: Alexei Starovoitov 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20211027234504.30744-3-joannekoong@fb.com

libbpf: Support kernel module function calls

2021-10-06T00:07:42+00:00

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 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20211002011757.311265-7-memxor@gmail.com

libbpf: Add bpf_cookie support to bpf_link_create() API

2021-08-16T22:45:08+00:00

Add ability to specify bpf_cookie value when creating BPF perf link with
bpf_link_create() low-level API.

Given BPF_LINK_CREATE command is growing and keeps getting new fields that are
specific to the type of BPF_LINK, extend libbpf side of bpf_link_create() API
and corresponding OPTS struct to accomodate such changes. Add extra checks to
prevent using incompatible/unexpected combinations of fields.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Daniel Borkmann 
Link: https://lore.kernel.org/bpf/20210815070609.987780-11-andrii@kernel.org

libbpf: Streamline error reporting for low-level APIs

2021-05-26T00:32:35+00:00

Ensure that low-level APIs behave uniformly across the libbpf as follows:
  - in case of an error, errno is always set to the correct error code;
  - when libbpf 1.0 mode is enabled with LIBBPF_STRICT_DIRECT_ERRS option to
    libbpf_set_strict_mode(), return -Exxx error value directly, instead of -1;
  - by default, until libbpf 1.0 is released, keep returning -1 directly.

More context, justification, and discussion can be found in "Libbpf: the road
to v1.0" document ([0]).

  [0] https://docs.google.com/document/d/1UyjTZuPFWiPFyKk1tV5an11_iaRuec6U-ZESZ54nNTY

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Acked-by: John Fastabend 
Acked-by: Toke Høiland-Jørgensen 
Link: https://lore.kernel.org/bpf/20210525035935.1461796-4-andrii@kernel.org

bpf: Extend libbpf with bpf_map_lookup_and_delete_elem_flags

2021-05-24T20:30:51+00:00

Add bpf_map_lookup_and_delete_elem_flags() libbpf API in order to use
the BPF_F_LOCK flag with the map_lookup_and_delete_elem() function.

Signed-off-by: Denis Salopek 
Signed-off-by: Andrii Nakryiko 
Acked-by: Yonghong Song 
Link: https://lore.kernel.org/bpf/15b05dafe46c7e0750d110f233977372029d1f62.1620763117.git.denis.salopek@sartura.hr

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

libbpf: Factor out low-level BPF program loading helper

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

Refactor low-level API for BPF program loading to not rely on public API
types. This allows painless extension without constant efforts to cleverly not
break backwards compatibility.

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20201203204634.1325171-12-andrii@kernel.org

libbpf: Cap retries in sys_bpf_prog_load

2020-12-03T20:01:18+00:00

I've seen a situation, where a process that's under pprof constantly
generates SIGPROF which prevents program loading indefinitely.
The right thing to do probably is to disable signals in the upper
layers while loading, but it still would be nice to get some error from
libbpf instead of an endless loop.

Let's add some small retry limit to the program loading:
try loading the program 5 (arbitrary) times and give up.

v2:
* 10 -> 5 retires (Andrii Nakryiko)

Signed-off-by: Stanislav Fomichev 
Signed-off-by: Andrii Nakryiko 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20201202231332.3923644-1-sdf@google.com