diff options
| author | Andrii Nakryiko <andrii@kernel.org> | 2023-05-08 23:55:02 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-05-12 12:05:21 -0700 |
| commit | bdeeed3498c7871c17465bb4f11d1bc67f9098af (patch) | |
| tree | b221e4b559bc7a642dd03266074cdb91ecdabbd7 | |
| parent | ee9fd0ac3017c4313be91a220a9ac4c99dde7ad4 (diff) | |
libbpf: fix offsetof() and container_of() to work with CO-RE
It seems like __builtin_offset() doesn't preserve CO-RE field
relocations properly. So if offsetof() macro is defined through
__builtin_offset(), CO-RE-enabled BPF code using container_of() will be
subtly and silently broken.
To avoid this problem, redefine offsetof() and container_of() in the
form that works with CO-RE relocations more reliably.
Fixes: 5fbc220862fc ("tools/libpf: Add offsetof/container_of macro in bpf_helpers.h")
Reported-by: Lennart Poettering <lennart@poettering.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20230509065502.2306180-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | tools/lib/bpf/bpf_helpers.h | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index 929a3baca8ef..bbab9ad9dc5a 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -77,16 +77,21 @@ /* * Helper macros to manipulate data structures */ -#ifndef offsetof -#define offsetof(TYPE, MEMBER) ((unsigned long)&((TYPE *)0)->MEMBER) -#endif -#ifndef container_of + +/* offsetof() definition that uses __builtin_offset() might not preserve field + * offset CO-RE relocation properly, so force-redefine offsetof() using + * old-school approach which works with CO-RE correctly + */ +#undef offsetof +#define offsetof(type, member) ((unsigned long)&((type *)0)->member) + +/* redefined container_of() to ensure we use the above offsetof() macro */ +#undef container_of #define container_of(ptr, type, member) \ ({ \ void *__mptr = (void *)(ptr); \ ((type *)(__mptr - offsetof(type, member))); \ }) -#endif /* * Compiler (optimization) barrier. |