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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
View File

@ -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;

1
tools/lib/bpf/btf.h
View File

@ -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);

47
tools/lib/bpf/btf_dump.c
View File

@ -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);
}

1
tools/lib/bpf/libbpf.map
View File

@ -212,4 +212,5 @@ LIBBPF_0.0.6 {
LIBBPF_0.0.7 {
global:
bpf_program__attach;
btf__align_of;
} LIBBPF_0.0.6;