diff options
author | Andrii Nakryiko <andrii@kernel.org> | 2022-12-15 21:36:05 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-04-05 12:23:52 +0300 |
commit | b4781477f397a9e10f36d035ffc76bfb67aa1639 (patch) | |
tree | e69583502ef9bd5b0e852f2050ae8faf2253ae23 /tools/lib | |
parent | 7ad30ad8c684362364e629574ab02eec3b9bb1bc (diff) | |
download | linux-b4781477f397a9e10f36d035ffc76bfb67aa1639.tar.xz |
libbpf: Fix btf_dump's packed struct determination
[ Upstream commit 4fb877aaa179dcdb1676d55216482febaada457e ]
Fix bug in btf_dump's logic of determining if a given struct type is
packed or not. The notion of "natural alignment" is not needed and is
even harmful in this case, so drop it altogether. The biggest difference
in btf_is_struct_packed() compared to its original implementation is
that we don't really use btf__align_of() to determine overall alignment
of a struct type (because it could be 1 for both packed and non-packed
struct, depending on specifci field definitions), and just use field's
actual alignment to calculate whether any field is requiring packing or
struct's size overall necessitates packing.
Add two simple test cases that demonstrate the difference this change
would make.
Fixes: ea2ce1ba99aa ("libbpf: Fix BTF-to-C converter's padding logic")
Reported-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20221215183605.4149488-1-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'tools/lib')
-rw-r--r-- | tools/lib/bpf/btf_dump.c | 33 |
1 files changed, 6 insertions, 27 deletions
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c index 4d27b08074a5..558d34fbd331 100644 --- a/tools/lib/bpf/btf_dump.c +++ b/tools/lib/bpf/btf_dump.c @@ -788,47 +788,26 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id) } } -static int btf_natural_align_of(const struct btf *btf, __u32 id) -{ - const struct btf_type *t = btf__type_by_id(btf, id); - int i, align, vlen; - const struct btf_member *m; - - if (!btf_is_composite(t)) - return btf__align_of(btf, id); - - align = 1; - m = btf_members(t); - vlen = btf_vlen(t); - for (i = 0; i < vlen; i++, m++) { - align = max(align, btf__align_of(btf, m->type)); - } - - return align; -} - static bool btf_is_struct_packed(const struct btf *btf, __u32 id, const struct btf_type *t) { const struct btf_member *m; - int align, i, bit_sz; + int max_align = 1, align, i, bit_sz; __u16 vlen; - align = btf_natural_align_of(btf, id); - /* size of a non-packed struct has to be a multiple of its alignment */ - if (align && (t->size % align) != 0) - return true; - m = btf_members(t); vlen = btf_vlen(t); /* all non-bitfield fields have to be naturally aligned */ for (i = 0; i < vlen; i++, m++) { - align = btf_natural_align_of(btf, m->type); + align = btf__align_of(btf, m->type); bit_sz = btf_member_bitfield_size(t, i); if (align && bit_sz == 0 && m->offset % (8 * align) != 0) return true; + max_align = max(align, max_align); } - + /* size of a non-packed struct has to be a multiple of its alignment */ + if (t->size % max_align != 0) + return true; /* * if original struct was marked as packed, but its layout is * naturally aligned, we'll detect that it's not packed |