Commit 3d208f4c authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

libbpf: Expose btf__align_of() API 



Expose BTF API that calculates type alignment requirements.

Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191214014341.3442258-7-andriin@fb.com
parent 544402d4

tools/lib/bpf/btf.c

+39 −0
Original line number Diff line number Diff line
@@ -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;

tools/lib/bpf/btf.h

+1 −0
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ LIBBPF_API const struct btf_type *btf__type_by_id(const struct btf *btf, 
						  __u32 id);

LIBBPF_API __s64 btf__resolve_size(const struct btf *btf, __u32 type_id);

LIBBPF_API int btf__resolve_type(const struct btf *btf, __u32 type_id);

LIBBPF_API int btf__align_of(const struct btf *btf, __u32 id);

LIBBPF_API int btf__fd(const struct btf *btf);

LIBBPF_API const void *btf__get_raw_data(const struct btf *btf, __u32 *size);

LIBBPF_API const char *btf__name_by_offset(const struct btf *btf, __u32 offset);

tools/lib/bpf/btf_dump.c

+6 −41
Original line number Diff line number Diff line
@@ -752,41 +752,6 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id) 
	}

}



static 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;



		for (i = 0; i < vlen; i++, m++)

			align = max(align, btf_align_of(btf, m->type));



		return align;

	}

	default:

		pr_warn("unsupported BTF_KIND:%u\n", btf_kind(t));

		return 1;

	}

}



static bool btf_is_struct_packed(const struct btf *btf, __u32 id,

				 const struct btf_type *t)

{
@@ -794,18 +759,18 @@ static bool btf_is_struct_packed(const struct btf *btf, __u32 id, 
	int align, i, bit_sz;

	__u16 vlen;



	align = btf_align_of(btf, id);

	align = btf__align_of(btf, id);

	/* size of a non-packed struct has to be a multiple of its alignment*/

	if (t->size % align)

	if (align && t->size % align)

		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_align_of(btf, m->type);

		align = btf__align_of(btf, m->type);

		bit_sz = btf_member_bitfield_size(t, i);

		if (bit_sz == 0 && m->offset % (8 * align) != 0)

		if (align && bit_sz == 0 && m->offset % (8 * align) != 0)

			return true;

	}
@@ -889,7 +854,7 @@ static void btf_dump_emit_struct_def(struct btf_dump *d, 
		fname = btf_name_of(d, m->name_off);

		m_sz = btf_member_bitfield_size(t, i);

		m_off = btf_member_bit_offset(t, i);

		align = packed ? 1 : btf_align_of(d->btf, m->type);

		align = packed ? 1 : btf__align_of(d->btf, m->type);



		btf_dump_emit_bit_padding(d, off, m_off, m_sz, align, lvl + 1);

		btf_dump_printf(d, "\n%s", pfx(lvl + 1));
@@ -907,7 +872,7 @@ static void btf_dump_emit_struct_def(struct btf_dump *d, 


	/* pad at the end, if necessary */

	if (is_struct) {

		align = packed ? 1 : btf_align_of(d->btf, id);

		align = packed ? 1 : btf__align_of(d->btf, id);

		btf_dump_emit_bit_padding(d, off, t->size * 8, 0, align,

					  lvl + 1);

	}

tools/lib/bpf/libbpf.map

+1 −0
Original line number Diff line number Diff line
@@ -212,4 +212,5 @@ LIBBPF_0.0.6 { 
LIBBPF_0.0.7 {

	global:

		bpf_program__attach;

		btf__align_of;

} LIBBPF_0.0.6;

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