Commit ec6209c8 authored by Daniel Müller's avatar Daniel Müller Committed by Andrii Nakryiko

bpf, libbpf: Add type match support

This patch adds support for the proposed type match relation to
relo_core where it is shared between userspace and kernel. It plumbs
through both kernel-side and libbpf-side support.

The matching relation is defined as follows (copy from source):
- modifiers and typedefs are stripped (and, hence, effectively ignored)
- generally speaking types need to be of same kind (struct vs. struct, union
  vs. union, etc.)
  - exceptions are struct/union behind a pointer which could also match a
    forward declaration of a struct or union, respectively, and enum vs.
    enum64 (see below)
Then, depending on type:
- integers:
  - match if size and signedness match
- arrays & pointers:
  - target types are recursively matched
- structs & unions:
  - local members need to exist in target with the same name
  - for each member we recursively check match unless it is already behind a
    pointer, in which case we only check matching names and compatible kind
- enums:
  - local variants have to have a match in target by symbolic name (but not
    numeric value)
  - size has to match (but enum may match enum64 and vice versa)
- function pointers:
  - number and position of arguments in local type has to match target
  - for each argument and the return value we recursively check match
Signed-off-by: default avatarDaniel Müller <deso@posteo.net>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220628160127.607834-5-deso@posteo.net
parent 633e7ceb
......@@ -7443,6 +7443,15 @@ int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
MAX_TYPES_ARE_COMPAT_DEPTH);
}
#define MAX_TYPES_MATCH_DEPTH 2
int bpf_core_types_match(const struct btf *local_btf, u32 local_id,
const struct btf *targ_btf, u32 targ_id)
{
return __bpf_core_types_match(local_btf, local_id, targ_btf, targ_id, false,
MAX_TYPES_MATCH_DEPTH);
}
static bool bpf_core_is_flavor_sep(const char *s)
{
/* check X___Y name pattern, where X and Y are not underscores */
......
......@@ -5470,6 +5470,12 @@ int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
return __bpf_core_types_are_compat(local_btf, local_id, targ_btf, targ_id, 32);
}
int bpf_core_types_match(const struct btf *local_btf, __u32 local_id,
const struct btf *targ_btf, __u32 targ_id)
{
return __bpf_core_types_match(local_btf, local_id, targ_btf, targ_id, false, 32);
}
static size_t bpf_core_hash_fn(const void *key, void *ctx)
{
return (size_t)key;
......
......@@ -95,6 +95,7 @@ static const char *core_relo_kind_str(enum bpf_core_relo_kind kind)
case BPF_CORE_TYPE_ID_LOCAL: return "local_type_id";
case BPF_CORE_TYPE_ID_TARGET: return "target_type_id";
case BPF_CORE_TYPE_EXISTS: return "type_exists";
case BPF_CORE_TYPE_MATCHES: return "type_matches";
case BPF_CORE_TYPE_SIZE: return "type_size";
case BPF_CORE_ENUMVAL_EXISTS: return "enumval_exists";
case BPF_CORE_ENUMVAL_VALUE: return "enumval_value";
......@@ -123,6 +124,7 @@ static bool core_relo_is_type_based(enum bpf_core_relo_kind kind)
case BPF_CORE_TYPE_ID_LOCAL:
case BPF_CORE_TYPE_ID_TARGET:
case BPF_CORE_TYPE_EXISTS:
case BPF_CORE_TYPE_MATCHES:
case BPF_CORE_TYPE_SIZE:
return true;
default:
......@@ -251,7 +253,7 @@ int __bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
* - field 'a' access (corresponds to '2' in low-level spec);
* - array element #3 access (corresponds to '3' in low-level spec).
*
* Type-based relocations (TYPE_EXISTS/TYPE_SIZE,
* Type-based relocations (TYPE_EXISTS/TYPE_MATCHES/TYPE_SIZE,
* TYPE_ID_LOCAL/TYPE_ID_TARGET) don't capture any field information. Their
* spec and raw_spec are kept empty.
*
......@@ -568,9 +570,14 @@ static int bpf_core_spec_match(struct bpf_core_spec *local_spec,
targ_spec->relo_kind = local_spec->relo_kind;
if (core_relo_is_type_based(local_spec->relo_kind)) {
return bpf_core_types_are_compat(local_spec->btf,
local_spec->root_type_id,
targ_btf, targ_id);
if (local_spec->relo_kind == BPF_CORE_TYPE_MATCHES)
return bpf_core_types_match(local_spec->btf,
local_spec->root_type_id,
targ_btf, targ_id);
else
return bpf_core_types_are_compat(local_spec->btf,
local_spec->root_type_id,
targ_btf, targ_id);
}
local_acc = &local_spec->spec[0];
......@@ -819,6 +826,7 @@ static int bpf_core_calc_type_relo(const struct bpf_core_relo *relo,
*validate = false;
break;
case BPF_CORE_TYPE_EXISTS:
case BPF_CORE_TYPE_MATCHES:
*val = 1;
break;
case BPF_CORE_TYPE_SIZE:
......@@ -1410,3 +1418,266 @@ int bpf_core_calc_relo_insn(const char *prog_name,
return 0;
}
static bool bpf_core_names_match(const struct btf *local_btf, size_t local_name_off,
const struct btf *targ_btf, size_t targ_name_off)
{
const char *local_n, *targ_n;
size_t local_len, targ_len;
local_n = btf__name_by_offset(local_btf, local_name_off);
targ_n = btf__name_by_offset(targ_btf, targ_name_off);
if (str_is_empty(targ_n))
return str_is_empty(local_n);
targ_len = bpf_core_essential_name_len(targ_n);
local_len = bpf_core_essential_name_len(local_n);
return targ_len == local_len && strncmp(local_n, targ_n, local_len) == 0;
}
static int bpf_core_enums_match(const struct btf *local_btf, const struct btf_type *local_t,
const struct btf *targ_btf, const struct btf_type *targ_t)
{
__u16 local_vlen = btf_vlen(local_t);
__u16 targ_vlen = btf_vlen(targ_t);
int i, j;
if (local_t->size != targ_t->size)
return 0;
if (local_vlen > targ_vlen)
return 0;
/* iterate over the local enum's variants and make sure each has
* a symbolic name correspondent in the target
*/
for (i = 0; i < local_vlen; i++) {
bool matched = false;
__u32 local_n_off, targ_n_off;
local_n_off = btf_is_enum(local_t) ? btf_enum(local_t)[i].name_off :
btf_enum64(local_t)[i].name_off;
for (j = 0; j < targ_vlen; j++) {
targ_n_off = btf_is_enum(targ_t) ? btf_enum(targ_t)[j].name_off :
btf_enum64(targ_t)[j].name_off;
if (bpf_core_names_match(local_btf, local_n_off, targ_btf, targ_n_off)) {
matched = true;
break;
}
}
if (!matched)
return 0;
}
return 1;
}
static int bpf_core_composites_match(const struct btf *local_btf, const struct btf_type *local_t,
const struct btf *targ_btf, const struct btf_type *targ_t,
bool behind_ptr, int level)
{
const struct btf_member *local_m = btf_members(local_t);
__u16 local_vlen = btf_vlen(local_t);
__u16 targ_vlen = btf_vlen(targ_t);
int i, j, err;
if (local_vlen > targ_vlen)
return 0;
/* check that all local members have a match in the target */
for (i = 0; i < local_vlen; i++, local_m++) {
const struct btf_member *targ_m = btf_members(targ_t);
bool matched = false;
for (j = 0; j < targ_vlen; j++, targ_m++) {
if (!bpf_core_names_match(local_btf, local_m->name_off,
targ_btf, targ_m->name_off))
continue;
err = __bpf_core_types_match(local_btf, local_m->type, targ_btf,
targ_m->type, behind_ptr, level - 1);
if (err > 0) {
matched = true;
break;
}
}
if (!matched)
return 0;
}
return 1;
}
/* Check that two types "match".
*
* The matching relation is defined as follows:
* - modifiers and typedefs are stripped (and, hence, effectively ignored)
* - generally speaking types need to be of same kind (struct vs. struct, union
* vs. union, etc.)
* - exceptions are struct/union behind a pointer which could also match a
* forward declaration of a struct or union, respectively, and enum vs.
* enum64 (see below)
* Then, depending on type:
* - integers:
* - match if size and signedness match
* - arrays & pointers:
* - target types are recursively matched
* - structs & unions:
* - local members need to exist in target with the same name
* - for each member we recursively check match unless it is already behind a
* pointer, in which case we only check matching names and compatible kind
* - enums:
* - local variants have to have a match in target by symbolic name (but not
* numeric value)
* - size has to match (but enum may match enum64 and vice versa)
* - function pointers:
* - number and position of arguments in local type has to match target
* - for each argument and the return value we recursively check match
*/
int __bpf_core_types_match(const struct btf *local_btf, __u32 local_id, const struct btf *targ_btf,
__u32 targ_id, bool behind_ptr, int level)
{
const struct btf_type *local_t, *targ_t;
int depth = 32; /* max recursion depth */
__u16 local_k, targ_k;
if (level <= 0)
return -EINVAL;
local_t = btf_type_by_id(local_btf, local_id);
targ_t = btf_type_by_id(targ_btf, targ_id);
recur:
depth--;
if (depth < 0)
return -EINVAL;
local_t = skip_mods_and_typedefs(local_btf, local_id, &local_id);
targ_t = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
if (!local_t || !targ_t)
return -EINVAL;
if (!bpf_core_names_match(local_btf, local_t->name_off, targ_btf, targ_t->name_off))
return 0;
local_k = btf_kind(local_t);
targ_k = btf_kind(targ_t);
switch (local_k) {
case BTF_KIND_UNKN:
return local_k == targ_k;
case BTF_KIND_FWD: {
bool local_f = BTF_INFO_KFLAG(local_t->info);
if (behind_ptr) {
if (local_k == targ_k)
return local_f == BTF_INFO_KFLAG(targ_t->info);
/* for forward declarations kflag dictates whether the
* target is a struct (0) or union (1)
*/
return (targ_k == BTF_KIND_STRUCT && !local_f) ||
(targ_k == BTF_KIND_UNION && local_f);
} else {
if (local_k != targ_k)
return 0;
/* match if the forward declaration is for the same kind */
return local_f == BTF_INFO_KFLAG(targ_t->info);
}
}
case BTF_KIND_ENUM:
case BTF_KIND_ENUM64:
if (!btf_is_any_enum(targ_t))
return 0;
return bpf_core_enums_match(local_btf, local_t, targ_btf, targ_t);
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
if (behind_ptr) {
bool targ_f = BTF_INFO_KFLAG(targ_t->info);
if (local_k == targ_k)
return 1;
if (targ_k != BTF_KIND_FWD)
return 0;
return (local_k == BTF_KIND_UNION) == targ_f;
} else {
if (local_k != targ_k)
return 0;
return bpf_core_composites_match(local_btf, local_t, targ_btf, targ_t,
behind_ptr, level);
}
case BTF_KIND_INT: {
__u8 local_sgn;
__u8 targ_sgn;
if (local_k != targ_k)
return 0;
local_sgn = btf_int_encoding(local_t) & BTF_INT_SIGNED;
targ_sgn = btf_int_encoding(targ_t) & BTF_INT_SIGNED;
return local_t->size == targ_t->size && local_sgn == targ_sgn;
}
case BTF_KIND_PTR:
if (local_k != targ_k)
return 0;
behind_ptr = true;
local_id = local_t->type;
targ_id = targ_t->type;
goto recur;
case BTF_KIND_ARRAY: {
const struct btf_array *local_array = btf_array(local_t);
const struct btf_array *targ_array = btf_array(targ_t);
if (local_k != targ_k)
return 0;
if (local_array->nelems != targ_array->nelems)
return 0;
local_id = local_array->type;
targ_id = targ_array->type;
goto recur;
}
case BTF_KIND_FUNC_PROTO: {
struct btf_param *local_p = btf_params(local_t);
struct btf_param *targ_p = btf_params(targ_t);
__u16 local_vlen = btf_vlen(local_t);
__u16 targ_vlen = btf_vlen(targ_t);
int i, err;
if (local_k != targ_k)
return 0;
if (local_vlen != targ_vlen)
return 0;
for (i = 0; i < local_vlen; i++, local_p++, targ_p++) {
err = __bpf_core_types_match(local_btf, local_p->type, targ_btf,
targ_p->type, behind_ptr, level - 1);
if (err <= 0)
return err;
}
/* tail recurse for return type check */
local_id = local_t->type;
targ_id = targ_t->type;
goto recur;
}
default:
pr_warn("unexpected kind %s relocated, local [%d], target [%d]\n",
btf_kind_str(local_t), local_id, targ_id);
return 0;
}
}
......@@ -72,6 +72,10 @@ int __bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
const struct btf *targ_btf, __u32 targ_id, int level);
int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
const struct btf *targ_btf, __u32 targ_id);
int __bpf_core_types_match(const struct btf *local_btf, __u32 local_id, const struct btf *targ_btf,
__u32 targ_id, bool behind_ptr, int level);
int bpf_core_types_match(const struct btf *local_btf, __u32 local_id, const struct btf *targ_btf,
__u32 targ_id);
size_t bpf_core_essential_name_len(const char *name);
......
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