diff options
| author | Andrii Nakryiko <andriin@fb.com> | 2020-08-19 22:45:15 +0300 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-08-20 00:19:39 +0300 |
| commit | 3fc32f40c40207bf85ce1b007f18981c4673df96 (patch) | |
| tree | 1a97d48c7887152a80f435822642bb494366b3f9 /tools/lib/bpf/libbpf_internal.h | |
| parent | defcffeb517b3965e64f4e5531db3b452dccbfc5 (diff) | |
| download | linux-3fc32f40c40207bf85ce1b007f18981c4673df96.tar.xz | |
libbpf: Implement type-based CO-RE relocations support
Implement support for TYPE_EXISTS/TYPE_SIZE/TYPE_ID_LOCAL/TYPE_ID_REMOTE
relocations. These are examples of type-based relocations, as opposed to
field-based relocations supported already. The difference is that they are
calculating relocation values based on the type itself, not a field within
a struct/union.
Type-based relos have slightly different semantics when matching local types
to kernel target types, see comments in bpf_core_types_are_compat() for
details. Their behavior on failure to find target type in kernel BTF also
differs. Instead of "poisoning" relocatable instruction and failing load
subsequently in kernel, they return 0 (which is rarely a valid return result,
so user BPF code can use that to detect success/failure of the relocation and
deal with it without extra "guarding" relocations). Also, it's always possible
to check existence of the type in target kernel with TYPE_EXISTS relocation,
similarly to a field-based FIELD_EXISTS.
TYPE_ID_LOCAL relocation is a bit special in that it always succeeds (barring
any libbpf/Clang bugs) and resolved to BTF ID using **local** BTF info of BPF
program itself. Tests in subsequent patches demonstrate the usage and
semantics of new relocations.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200819194519.3375898-2-andriin@fb.com
Diffstat (limited to 'tools/lib/bpf/libbpf_internal.h')
| -rw-r--r-- | tools/lib/bpf/libbpf_internal.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index c8ed352671d5..edd3511aa242 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -238,6 +238,10 @@ enum bpf_core_relo_kind { BPF_FIELD_SIGNED = 3, /* field signedness (0 - unsigned, 1 - signed) */ BPF_FIELD_LSHIFT_U64 = 4, /* bitfield-specific left bitshift */ BPF_FIELD_RSHIFT_U64 = 5, /* bitfield-specific right bitshift */ + BPF_TYPE_ID_LOCAL = 6, /* type ID in local BPF object */ + BPF_TYPE_ID_TARGET = 7, /* type ID in target kernel */ + BPF_TYPE_EXISTS = 8, /* type existence in target kernel */ + BPF_TYPE_SIZE = 9, /* type size in bytes */ }; /* The minimum bpf_core_relo checked by the loader |