diff options
| author | Yonghong Song <yhs@fb.com> | 2020-08-10 20:08:52 -0700 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2020-08-11 15:11:07 +0200 |
| commit | 63fe3fd393dc4e7ea3948e79947362ffbb0fd616 (patch) | |
| tree | 396dd9a9d0621eeeb0e919caf9c6653308b24219 | |
| parent | 444da3f52407d74c9aa12187ac6b01f76ee47d62 (diff) | |
libbpf: Do not use __builtin_offsetof for offsetof
Commit 5fbc220862fc ("tools/libpf: Add offsetof/container_of macro
in bpf_helpers.h") added a macro offsetof() to get the offset of a
structure member:
#define offsetof(TYPE, MEMBER) ((size_t)&((TYPE *)0)->MEMBER)
In certain use cases, size_t type may not be available so
Commit da7a35062bcc ("libbpf bpf_helpers: Use __builtin_offsetof
for offsetof") changed to use __builtin_offsetof which removed
the dependency on type size_t, which I suggested.
But using __builtin_offsetof will prevent CO-RE relocation
generation in case that, e.g., TYPE is annotated with "preserve_access_info"
where a relocation is desirable in case the member offset is changed
in a different kernel version. So this patch reverted back to
the original macro but using "unsigned long" instead of "site_t".
Fixes: da7a35062bcc ("libbpf bpf_helpers: Use __builtin_offsetof for offsetof")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/bpf/20200811030852.3396929-1-yhs@fb.com
| -rw-r--r-- | tools/lib/bpf/bpf_helpers.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index bc14db706b88..e9a4ecddb7a5 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -40,7 +40,7 @@ * Helper macro to manipulate data structures */ #ifndef offsetof -#define offsetof(TYPE, MEMBER) __builtin_offsetof(TYPE, MEMBER) +#define offsetof(TYPE, MEMBER) ((unsigned long)&((TYPE *)0)->MEMBER) #endif #ifndef container_of #define container_of(ptr, type, member) \ |