kernel/linux.git/tools/lib/bpf/libbpf.c, branch v5.7.3

libbpf: Always specify expected_attach_type on program load if supported

2020-04-15T11:22:43+00:00

For some types of BPF programs that utilize expected_attach_type, libbpf won't set load_attr.expected_attach_type, even if expected_attach_type is known from section definition. This was done to preserve backwards compatibility with old kernels that didn't recognize expected_attach_type attribute yet (which was added in 5e43f899b03a ("bpf: Check attach type at prog load time"). But this is problematic for some BPF programs that utilize newer features that require kernel to know specific expected_attach_type (e.g., extended set of return codes for cgroup_skb/egress programs). This patch makes libbpf specify expected_attach_type by default, but also detect support for this field in kernel and not set it during program load. This allows to have a good metadata for bpf_program (e.g., bpf_program__get_extected_attach_type()), but still work with old kernels (for cases where it can work at all). Additionally, due to expected_attach_type being always set for recognized program types, bpf_program__attach_cgroup doesn't have to do extra checks to determine correct attach type, so remove that additional logic. Also adjust section_names selftest to account for this change. More detailed discussion can be found in [0]. [0] https://lore.kernel.org/bpf/20200412003604.GA15986@rdna-mbp.dhcp.thefacebook.com/ Fixes: 5cf1e9145630 ("bpf: cgroup inet skb programs can return 0 to 3") Fixes: 5e43f899b03a ("bpf: Check attach type at prog load time") Reported-by: Andrey Ignatov Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Acked-by: Song Liu Acked-by: Andrey Ignatov Link: https://lore.kernel.org/bpf/20200414182645.1368174-1-andriin@fb.com

libbpf: Add support for bpf_link-based cgroup attachment

2020-03-31T00:36:41+00:00

Add bpf_program__attach_cgroup(), which uses BPF_LINK_CREATE subcommand to create an FD-based kernel bpf_link. Also add low-level bpf_link_create() API. If expected_attach_type is not specified explicitly with bpf_program__set_expected_attach_type(), libbpf will try to determine proper attach type from BPF program's section definition. Also add support for bpf_link's underlying BPF program replacement: - unconditional through high-level bpf_link__update_program() API; - cmpxchg-like with specifying expected current BPF program through low-level bpf_link_update() API. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20200330030001.2312810-4-andriin@fb.com

tools/libbpf: Add support for BPF_PROG_TYPE_LSM

2020-03-29T23:35:11+00:00

Since BPF_PROG_TYPE_LSM uses the same attaching mechanism as BPF_PROG_TYPE_TRACING, the common logic is refactored into a static function bpf_program__attach_btf_id. A new API call bpf_program__attach_lsm is still added to avoid userspace conflicts if this ever changes in the future. Signed-off-by: KP Singh Signed-off-by: Daniel Borkmann Reviewed-by: Brendan Jackman Reviewed-by: Florent Revest Reviewed-by: James Morris Acked-by: Yonghong Song Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20200329004356.27286-7-kpsingh@chromium.org

libbpf: Add setter for initial value for internal maps

2020-03-29T23:17:05+00:00

For internal maps (most notably the maps backing global variables), libbpf uses an internal mmaped area to store the data after opening the object. This data is subsequently copied into the kernel map when the object is loaded. This adds a function to set a new value for that data, which can be used to before it is loaded into the kernel. This is especially relevant for RODATA maps, since those are frozen on load. Signed-off-by: Toke Høiland-Jørgensen Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20200329132253.232541-1-toke@redhat.com

libbpf: Don't allocate 16M for log buffer by default

2020-03-25T23:13:37+00:00

For each prog/btf load we allocate and free 16 megs of verifier buffer. On production systems it doesn't really make sense because the programs/btf have gone through extensive testing and (mostly) guaranteed to successfully load. Let's assume successful case by default and skip buffer allocation on the first try. If there is an error, start with BPF_LOG_BUF_SIZE and double it on each ENOSPC iteration. v3: * Return -ENOMEM when can't allocate log buffer (Andrii Nakryiko) v2: * Don't allocate the buffer at all on the first try (Andrii Nakryiko) Signed-off-by: Stanislav Fomichev Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20200325195521.112210-1-sdf@google.com

libbpf: Remove unused parameter `def` to get_map_field_int

2020-03-25T23:11:06+00:00

Has been unused since commit ef99b02b23ef ("libbpf: capture value in BTF type info for BTF-defined map defs"). Signed-off-by: Tobias Klauser Signed-off-by: Daniel Borkmann Reviewed-by: Quentin Monnet Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20200325113655.19341-1-tklauser@distanz.ch

libbpf: Ignore incompatible types with matching name during CO-RE relocation

2020-03-13T22:30:53+00:00

When finding target type candidates, ignore forward declarations, functions, and other named types of incompatible kind. Not doing this can cause false errors. See [0] for one such case (due to struct pt_regs forward declaration). [0] https://github.com/iovisor/bcc/pull/2806#issuecomment-598543645 Fixes: ddc7c3042614 ("libbpf: implement BPF CO-RE offset relocation algorithm") Reported-by: Wenbo Zhang Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20200313172336.1879637-3-andriin@fb.com

libbpf: Split BTF presence checks into libbpf- and kernel-specific parts

2020-03-12T23:15:16+00:00

Needs for application BTF being present differs between user-space libbpf needs and kernel needs. Currently, BTF is mandatory only in kernel only when BPF application is using STRUCT_OPS. While libbpf itself relies more heavily on presense of BTF: - for BTF-defined maps; - for Kconfig externs; - for STRUCT_OPS as well. Thus, checks for presence and validness of bpf_object's BPF needs to be performed separately, which is patch does. Fixes: 5327644614a1 ("libbpf: Relax check whether BTF is mandatory") Reported-by: Michal Rostecki Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Acked-by: Martin KaFai Lau Cc: Quentin Monnet Link: https://lore.kernel.org/bpf/20200312185033.736911-1-andriin@fb.com

tools/libbpf: Add support for BPF_MODIFY_RETURN

2020-03-04T21:41:05+00:00

Signed-off-by: KP Singh Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Acked-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20200304191853.1529-6-kpsingh@chromium.org

libbpf: Add bpf_link pinning/unpinning

2020-03-03T06:06:27+00:00

With bpf_link abstraction supported by kernel explicitly, add pinning/unpinning API for links. Also allow to create (open) bpf_link from BPF FS file. This API allows to have an "ephemeral" FD-based BPF links (like raw tracepoint or fexit/freplace attachments) surviving user process exit, by pinning them in a BPF FS, which is an important use case for long-running BPF programs. As part of this, expose underlying FD for bpf_link. While legacy bpf_link's might not have a FD associated with them (which will be expressed as a bpf_link with fd=-1), kernel's abstraction is based around FD-based usage, so match it closely. This, subsequently, allows to have a generic pinning/unpinning API for generalized bpf_link. For some types of bpf_links kernel might not support pinning, in which case bpf_link__pin() will return error. With FD being part of generic bpf_link, also get rid of bpf_link_fd in favor of using vanialla bpf_link. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20200303043159.323675-3-andriin@fb.com