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| author | Andrii Nakryiko <andrii@kernel.org> | 2023-05-08 23:55:02 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-07-19 16:21:04 +0200 |
| commit | 34fe7aa8ef1d159ca6b6f01728788e8b702ac7c5 (patch) | |
| tree | a6daf6e070b769161b91b01e1e34fbab9cb13c66 | |
| parent | 8404f8de1e23690524b92dded514dee29160f7ad (diff) | |
| download | linux-starfive-34fe7aa8ef1d159ca6b6f01728788e8b702ac7c5.tar.gz linux-starfive-34fe7aa8ef1d159ca6b6f01728788e8b702ac7c5.tar.bz2 linux-starfive-34fe7aa8ef1d159ca6b6f01728788e8b702ac7c5.zip | |
libbpf: fix offsetof() and container_of() to work with CO-RE
[ Upstream commit bdeeed3498c7871c17465bb4f11d1bc67f9098af ]
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>
Signed-off-by: Sasha Levin <sashal@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 d37c4fe2849d..2b3b300bf4df 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. |