libbpf: Fix btf__align_of() by taking into account field offsets

stable inclusion
from stable-v5.10.173
commit 3938f01405d61fde44b25a960c2d6cc851c80467
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8BFR3

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3938f01405d61fde44b25a960c2d6cc851c80467



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[ Upstream commit 25a4481b ]

btf__align_of() is supposed to be return alignment requirement of
a requested BTF type. For STRUCT/UNION it doesn't always return correct
value, because it calculates alignment only based on field types. But
for packed structs this is not enough, we need to also check field
offsets and struct size. If field offset isn't aligned according to
field type's natural alignment, then struct must be packed. Similarly,
if struct size is not a multiple of struct's natural alignment, then
struct must be packed as well.

This patch fixes this issue precisely by additionally checking these
conditions.

Fixes: 3d208f4c ("libbpf: Expose btf__align_of() API")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20221212211505.558851-5-andrii@kernel.org


Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>