Add support for extern variables, provided to BPF program by libbpf. Currently
the following extern variables are supported:
- LINUX_KERNEL_VERSION; version of a kernel in which BPF program is
executing, follows KERNEL_VERSION() macro convention, can be 4- and 8-byte
long;
- CONFIG_xxx values; a set of values of actual kernel config. Tristate,
boolean, strings, and integer values are supported.
Set of possible values is determined by declared type of extern variable.
Supported types of variables are:
- Tristate values. Are represented as `enum libbpf_tristate`. Accepted values
are **strictly** 'y', 'n', or 'm', which are represented as TRI_YES, TRI_NO,
or TRI_MODULE, respectively.
- Boolean values. Are represented as bool (_Bool) types. Accepted values are
'y' and 'n' only, turning into true/false values, respectively.
- Single-character values. Can be used both as a substritute for
bool/tristate, or as a small-range integer:
- 'y'/'n'/'m' are represented as is, as characters 'y', 'n', or 'm';
- integers in a range [-128, 127] or [0, 255] (depending on signedness of
char in target architecture) are recognized and represented with
respective values of char type.
- Strings. String values are declared as fixed-length char arrays. String of
up to that length will be accepted and put in first N bytes of char array,
with the rest of bytes zeroed out. If config string value is longer than
space alloted, it will be truncated and warning message emitted. Char array
is always zero terminated. String literals in config have to be enclosed in
double quotes, just like C-style string literals.
- Integers. 8-, 16-, 32-, and 64-bit integers are supported, both signed and
unsigned variants. Libbpf enforces parsed config value to be in the
supported range of corresponding integer type. Integers values in config can
be:
- decimal integers, with optional + and - signs;
- hexadecimal integers, prefixed with 0x or 0X;
- octal integers, starting with 0.
Config file itself is searched in /boot/config-$(uname -r) location with
fallback to /proc/config.gz, unless config path is specified explicitly
through bpf_object_open_opts' kernel_config_path option. Both gzipped and
plain text formats are supported. Libbpf adds explicit dependency on zlib
because of this, but this shouldn't be a problem, given libelf already depends
on zlib.
All detected extern variables, are put into a separate .extern internal map.
It, similarly to .rodata map, is marked as read-only from BPF program side, as
well as is frozen on load. This allows BPF verifier to track extern values as
constants and perform enhanced branch prediction and dead code elimination.
This can be relied upon for doing kernel version/feature detection and using
potentially unsupported field relocations or BPF helpers in a CO-RE-based BPF
program, while still having a single version of BPF program running on old and
new kernels. Selftests are validating this explicitly for unexisting BPF
helper.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191214014710.3449601-3-andriin@fb.com
For BPF_PROG_TYPE_TRACING, the bpf_prog's ctx is an array of u64.
This patch borrows the idea from BPF_CALL_x in filter.h to
convert a u64 to the arg type of the traced function.
The new BPF_TRACE_x has an arg to specify the return type of a bpf_prog.
It will be used in the future TCP-ops bpf_prog that may return "void".
The new macros are defined in the new header file "bpf_trace_helpers.h".
It is under selftests/bpf/ for now. It could be moved to libbpf later
after seeing more upcoming non-tracing use cases.
The tests are changed to use these new macros also. Hence,
the k[s]u8/16/32/64 are no longer needed and they are removed
from the bpf_helpers.h.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191123202504.1502696-1-kafai@fb.com
Add sanity test for BPF trampoline that checks kernel functions
with up to 6 arguments of different sizes.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-10-ast@kernel.org
This adds support to libbpf for setting map pinning information as part of
the BTF map declaration, to get automatic map pinning (and reuse) on load.
The pinning type currently only supports a single PIN_BY_NAME mode, where
each map will be pinned by its name in a path that can be overridden, but
defaults to /sys/fs/bpf.
Since auto-pinning only does something if any maps actually have a
'pinning' BTF attribute set, we default the new option to enabled, on the
assumption that seamless pinning is what most callers want.
When a map has a pin_path set at load time, libbpf will compare the map
pinned at that location (if any), and if the attributes match, will re-use
that map instead of creating a new one. If no existing map is found, the
newly created map will instead be pinned at the location.
Programs wanting to customise the pinning can override the pinning paths
using bpf_map__set_pin_path() before calling bpf_object__load() (including
setting it to NULL to disable pinning of a particular map).
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/157269298092.394725.3966306029218559681.stgit@toke.dk
Add few macros simplifying BCC-like multi-level probe reads, while also
emitting CO-RE relocations for each read.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191008175942.1769476-7-andriin@fb.com
Move bpf_helpers.h, bpf_tracing.h, and bpf_endian.h into libbpf. Move
bpf_helper_defs.h generation into libbpf's Makefile. Ensure all those
headers are installed along the other libbpf headers. Also, adjust
selftests and samples include path to include libbpf now.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191008175942.1769476-6-andriin@fb.com
Andrii Nakryiko