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libbpf: Expose btf__align_of() API

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Expose BTF API that calculates type alignment requirements.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191214014341.3442258-7-andriin@fb.com
This commit is contained in:
Andrii Nakryiko
2019-12-13 17:43:30 -08:00
committed by Alexei Starovoitov
parent 544402d4b4
commit 3d208f4ca1
4 changed files with 47 additions and 41 deletions
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39
tools/lib/bpf/btf.c
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@@ -278,6 +278,45 @@ done:
return nelems * size;
}
int btf__align_of(const struct btf *btf, __u32 id)
{
const struct btf_type *t = btf__type_by_id(btf, id);
__u16 kind = btf_kind(t);
switch (kind) {
case BTF_KIND_INT:
case BTF_KIND_ENUM:
return min(sizeof(void *), t->size);
case BTF_KIND_PTR:
return sizeof(void *);
case BTF_KIND_TYPEDEF:
case BTF_KIND_VOLATILE:
case BTF_KIND_CONST:
case BTF_KIND_RESTRICT:
return btf__align_of(btf, t->type);
case BTF_KIND_ARRAY:
return btf__align_of(btf, btf_array(t)->type);
case BTF_KIND_STRUCT:
case BTF_KIND_UNION: {
const struct btf_member *m = btf_members(t);
__u16 vlen = btf_vlen(t);
int i, align = 1, t;
for (i = 0; i < vlen; i++, m++) {
t = btf__align_of(btf, m->type);
if (t <= 0)
return t;
align = max(align, t);
}
return align;
}
default:
pr_warn("unsupported BTF_KIND:%u\n", btf_kind(t));
return 0;
}
}
int btf__resolve_type(const struct btf *btf, __u32 type_id)
{
const struct btf_type *t;