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".
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Fixes: da7a35062bcc ("libbpf bpf_helpers: Use __builtin_offsetof for offsetof")
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
tools/lib/bpf/bpf_helpers.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
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) \
--
2.24.1
