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bpf: kernel side support for BTF Var and DataSec

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This work adds kernel-side verification, logging and seq_show dumping
of BTF Var and DataSec kinds which are emitted with latest LLVM. The
following constraints apply:

BTF Var must have:

- Its kind_flag is 0
- Its vlen is 0
- Must point to a valid type
- Type must not resolve to a forward type
- Size of underlying type must be > 0
- Must have a valid name
- Can only be a source type, not sink or intermediate one
- Name may include dots (e.g. in case of static variables
  inside functions)
- Cannot be a member of a struct/union
- Linkage so far can either only be static or global/allocated

BTF DataSec must have:

- Its kind_flag is 0
- Its vlen cannot be 0
- Its size cannot be 0
- Must have a valid name
- Can only be a source type, not sink or intermediate one
- Name may include dots (e.g. to represent .bss, .data, .rodata etc)
- Cannot be a member of a struct/union
- Inner btf_var_secinfo array with {type,offset,size} triple
  must be sorted by offset in ascending order
- Type must always point to BTF Var
- BTF resolved size of Var must be <= size provided by triple
- DataSec size must be >= sum of triple sizes (thus holes
  are allowed)

btf_var_resolve(), btf_ptr_resolve() and btf_modifier_resolve()
are on a high level quite similar but each come with slight,
subtle differences. They could potentially be a bit refactored
in future which hasn't been done here to ease review.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann 2019-04-09 23:20:09 +02:00 committed by Alexei Starovoitov
parent f063c889c9
commit 1dc9285184
1 changed files with 397 additions and 20 deletions
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417
kernel/bpf/btf.c
View File

@ -185,6 +185,16 @@
i < btf_type_vlen(struct_type); \
i++, member++)
#define for_each_vsi(i, struct_type, member) \
for (i = 0, member = btf_type_var_secinfo(struct_type); \
i < btf_type_vlen(struct_type); \
i++, member++)
#define for_each_vsi_from(i, from, struct_type, member) \
for (i = from, member = btf_type_var_secinfo(struct_type) + from; \
i < btf_type_vlen(struct_type); \
i++, member++)
static DEFINE_IDR(btf_idr);
static DEFINE_SPINLOCK(btf_idr_lock);
@ -262,6 +272,8 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
[BTF_KIND_RESTRICT] = "RESTRICT",
[BTF_KIND_FUNC] = "FUNC",
[BTF_KIND_FUNC_PROTO] = "FUNC_PROTO",
[BTF_KIND_VAR] = "VAR",
[BTF_KIND_DATASEC] = "DATASEC",
};
struct btf_kind_operations {
@ -375,13 +387,36 @@ static bool btf_type_is_int(const struct btf_type *t)
return BTF_INFO_KIND(t->info) == BTF_KIND_INT;
}
static bool btf_type_is_var(const struct btf_type *t)
{
return BTF_INFO_KIND(t->info) == BTF_KIND_VAR;
}
static bool btf_type_is_datasec(const struct btf_type *t)
{
return BTF_INFO_KIND(t->info) == BTF_KIND_DATASEC;
}
/* Types that act only as a source, not sink or intermediate
* type when resolving.
*/
static bool btf_type_is_resolve_source_only(const struct btf_type *t)
{
return btf_type_is_var(t) ||
btf_type_is_datasec(t);
}
/* What types need to be resolved?
*
* btf_type_is_modifier() is an obvious one.
*
* btf_type_is_struct() because its member refers to
* another type (through member->type).
*
* btf_type_is_var() because the variable refers to
* another type. btf_type_is_datasec() holds multiple
* btf_type_is_var() types that need resolving.
*
* btf_type_is_array() because its element (array->type)
* refers to another type. Array can be thought of a
* special case of struct while array just has the same
@ -390,9 +425,11 @@ static bool btf_type_is_int(const struct btf_type *t)
static bool btf_type_needs_resolve(const struct btf_type *t)
{
return btf_type_is_modifier(t) ||
btf_type_is_ptr(t) ||
btf_type_is_struct(t) ||
btf_type_is_array(t);
btf_type_is_ptr(t) ||
btf_type_is_struct(t) ||
btf_type_is_array(t) ||
btf_type_is_var(t) ||
btf_type_is_datasec(t);
}
/* t->size can be used */
@ -403,6 +440,7 @@ static bool btf_type_has_size(const struct btf_type *t)
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
case BTF_KIND_ENUM:
case BTF_KIND_DATASEC:
return true;
}
@ -467,6 +505,16 @@ static const struct btf_enum *btf_type_enum(const struct btf_type *t)
return (const struct btf_enum *)(t + 1);
}
static const struct btf_var *btf_type_var(const struct btf_type *t)
{
return (const struct btf_var *)(t + 1);
}
static const struct btf_var_secinfo *btf_type_var_secinfo(const struct btf_type *t)
{
return (const struct btf_var_secinfo *)(t + 1);
}
static const struct btf_kind_operations *btf_type_ops(const struct btf_type *t)
{
return kind_ops[BTF_INFO_KIND(t->info)];
@ -478,23 +526,31 @@ static bool btf_name_offset_valid(const struct btf *btf, u32 offset)
offset < btf->hdr.str_len;
}
/* Only C-style identifier is permitted. This can be relaxed if
* necessary.
*/
static bool btf_name_valid_identifier(const struct btf *btf, u32 offset)
static bool __btf_name_char_ok(char c, bool first, bool dot_ok)
{
if ((first ? !isalpha(c) :
!isalnum(c)) &&
c != '_' &&
((c == '.' && !dot_ok) ||
c != '.'))
return false;
return true;
}
static bool __btf_name_valid(const struct btf *btf, u32 offset, bool dot_ok)
{
/* offset must be valid */
const char *src = &btf->strings[offset];
const char *src_limit;
if (!isalpha(*src) && *src != '_')
if (!__btf_name_char_ok(*src, true, dot_ok))
return false;
/* set a limit on identifier length */
src_limit = src + KSYM_NAME_LEN;
src++;
while (*src && src < src_limit) {
if (!isalnum(*src) && *src != '_')
if (!__btf_name_char_ok(*src, false, dot_ok))
return false;
src++;
}
@ -502,6 +558,19 @@ static bool btf_name_valid_identifier(const struct btf *btf, u32 offset)
return !*src;
}
/* Only C-style identifier is permitted. This can be relaxed if
* necessary.
*/
static bool btf_name_valid_identifier(const struct btf *btf, u32 offset)
{
return __btf_name_valid(btf, offset, false);
}
static bool btf_name_valid_section(const struct btf *btf, u32 offset)
{
return __btf_name_valid(btf, offset, true);
}
static const char *__btf_name_by_offset(const struct btf *btf, u32 offset)
{
if (!offset)
@ -697,6 +766,32 @@ static void btf_verifier_log_member(struct btf_verifier_env *env,
__btf_verifier_log(log, "\n");
}
__printf(4, 5)
static void btf_verifier_log_vsi(struct btf_verifier_env *env,
const struct btf_type *datasec_type,
const struct btf_var_secinfo *vsi,
const char *fmt, ...)
{
struct bpf_verifier_log *log = &env->log;
va_list args;
if (!bpf_verifier_log_needed(log))
return;
if (env->phase != CHECK_META)
btf_verifier_log_type(env, datasec_type, NULL);
__btf_verifier_log(log, "\t type_id=%u offset=%u size=%u",
vsi->type, vsi->offset, vsi->size);
if (fmt && *fmt) {
__btf_verifier_log(log, " ");
va_start(args, fmt);
bpf_verifier_vlog(log, fmt, args);
va_end(args);
}
__btf_verifier_log(log, "\n");
}
static void btf_verifier_log_hdr(struct btf_verifier_env *env,
u32 btf_data_size)
{
@ -974,7 +1069,8 @@ const struct btf_type *btf_type_id_size(const struct btf *btf,
} else if (btf_type_is_ptr(size_type)) {
size = sizeof(void *);
} else {
if (WARN_ON_ONCE(!btf_type_is_modifier(size_type)))
if (WARN_ON_ONCE(!btf_type_is_modifier(size_type) &&
!btf_type_is_var(size_type)))
return NULL;
size = btf->resolved_sizes[size_type_id];
@ -1509,7 +1605,7 @@ static int btf_modifier_resolve(struct btf_verifier_env *env,
u32 next_type_size = 0;
next_type = btf_type_by_id(btf, next_type_id);
if (!next_type) {
if (!next_type || btf_type_is_resolve_source_only(next_type)) {
btf_verifier_log_type(env, v->t, "Invalid type_id");
return -EINVAL;
}
@ -1542,6 +1638,53 @@ static int btf_modifier_resolve(struct btf_verifier_env *env,
return 0;
}
static int btf_var_resolve(struct btf_verifier_env *env,
const struct resolve_vertex *v)
{
const struct btf_type *next_type;
const struct btf_type *t = v->t;
u32 next_type_id = t->type;
struct btf *btf = env->btf;
u32 next_type_size;
next_type = btf_type_by_id(btf, next_type_id);
if (!next_type || btf_type_is_resolve_source_only(next_type)) {
btf_verifier_log_type(env, v->t, "Invalid type_id");
return -EINVAL;
}
if (!env_type_is_resolve_sink(env, next_type) &&
!env_type_is_resolved(env, next_type_id))
return env_stack_push(env, next_type, next_type_id);
if (btf_type_is_modifier(next_type)) {
const struct btf_type *resolved_type;
u32 resolved_type_id;
resolved_type_id = next_type_id;
resolved_type = btf_type_id_resolve(btf, &resolved_type_id);
if (btf_type_is_ptr(resolved_type) &&
!env_type_is_resolve_sink(env, resolved_type) &&
!env_type_is_resolved(env, resolved_type_id))
return env_stack_push(env, resolved_type,
resolved_type_id);
}
/* We must resolve to something concrete at this point, no
* forward types or similar that would resolve to size of
* zero is allowed.
*/
if (!btf_type_id_size(btf, &next_type_id, &next_type_size)) {
btf_verifier_log_type(env, v->t, "Invalid type_id");
return -EINVAL;
}
env_stack_pop_resolved(env, next_type_id, next_type_size);
return 0;
}
static int btf_ptr_resolve(struct btf_verifier_env *env,
const struct resolve_vertex *v)
{
@ -1551,7 +1694,7 @@ static int btf_ptr_resolve(struct btf_verifier_env *env,
struct btf *btf = env->btf;
next_type = btf_type_by_id(btf, next_type_id);
if (!next_type) {
if (!next_type || btf_type_is_resolve_source_only(next_type)) {
btf_verifier_log_type(env, v->t, "Invalid type_id");
return -EINVAL;
}
@ -1609,6 +1752,15 @@ static void btf_modifier_seq_show(const struct btf *btf,
btf_type_ops(t)->seq_show(btf, t, type_id, data, bits_offset, m);
}
static void btf_var_seq_show(const struct btf *btf, const struct btf_type *t,
u32 type_id, void *data, u8 bits_offset,
struct seq_file *m)
{
t = btf_type_id_resolve(btf, &type_id);
btf_type_ops(t)->seq_show(btf, t, type_id, data, bits_offset, m);
}
static void btf_ptr_seq_show(const struct btf *btf, const struct btf_type *t,
u32 type_id, void *data, u8 bits_offset,
struct seq_file *m)
@ -1776,7 +1928,8 @@ static int btf_array_resolve(struct btf_verifier_env *env,
/* Check array->index_type */
index_type_id = array->index_type;
index_type = btf_type_by_id(btf, index_type_id);
if (btf_type_nosize_or_null(index_type)) {
if (btf_type_is_resolve_source_only(index_type) ||
btf_type_nosize_or_null(index_type)) {
btf_verifier_log_type(env, v->t, "Invalid index");
return -EINVAL;
}
@ -1795,7 +1948,8 @@ static int btf_array_resolve(struct btf_verifier_env *env,
/* Check array->type */
elem_type_id = array->type;
elem_type = btf_type_by_id(btf, elem_type_id);
if (btf_type_nosize_or_null(elem_type)) {
if (btf_type_is_resolve_source_only(elem_type) ||
btf_type_nosize_or_null(elem_type)) {
btf_verifier_log_type(env, v->t,
"Invalid elem");
return -EINVAL;
@ -2016,7 +2170,8 @@ static int btf_struct_resolve(struct btf_verifier_env *env,
const struct btf_type *member_type = btf_type_by_id(env->btf,
member_type_id);
if (btf_type_nosize_or_null(member_type)) {
if (btf_type_is_resolve_source_only(member_type) ||
btf_type_nosize_or_null(member_type)) {
btf_verifier_log_member(env, v->t, member,
"Invalid member");
return -EINVAL;
@ -2411,6 +2566,222 @@ static struct btf_kind_operations func_ops = {
.seq_show = btf_df_seq_show,
};
static s32 btf_var_check_meta(struct btf_verifier_env *env,
const struct btf_type *t,
u32 meta_left)
{
const struct btf_var *var;
u32 meta_needed = sizeof(*var);
if (meta_left < meta_needed) {
btf_verifier_log_basic(env, t,
"meta_left:%u meta_needed:%u",
meta_left, meta_needed);
return -EINVAL;
}
if (btf_type_vlen(t)) {
btf_verifier_log_type(env, t, "vlen != 0");
return -EINVAL;
}
if (btf_type_kflag(t)) {
btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
return -EINVAL;
}
if (!t->name_off ||
!__btf_name_valid(env->btf, t->name_off, true)) {
btf_verifier_log_type(env, t, "Invalid name");
return -EINVAL;
}
/* A var cannot be in type void */
if (!t->type || !BTF_TYPE_ID_VALID(t->type)) {
btf_verifier_log_type(env, t, "Invalid type_id");
return -EINVAL;
}
var = btf_type_var(t);
if (var->linkage != BTF_VAR_STATIC &&
var->linkage != BTF_VAR_GLOBAL_ALLOCATED) {
btf_verifier_log_type(env, t, "Linkage not supported");
return -EINVAL;
}
btf_verifier_log_type(env, t, NULL);
return meta_needed;
}
static void btf_var_log(struct btf_verifier_env *env, const struct btf_type *t)
{
const struct btf_var *var = btf_type_var(t);
btf_verifier_log(env, "type_id=%u linkage=%u", t->type, var->linkage);
}
static const struct btf_kind_operations var_ops = {
.check_meta = btf_var_check_meta,
.resolve = btf_var_resolve,
.check_member = btf_df_check_member,
.check_kflag_member = btf_df_check_kflag_member,
.log_details = btf_var_log,
.seq_show = btf_var_seq_show,
};
static s32 btf_datasec_check_meta(struct btf_verifier_env *env,
const struct btf_type *t,
u32 meta_left)
{
const struct btf_var_secinfo *vsi;
u64 last_vsi_end_off = 0, sum = 0;
u32 i, meta_needed;
meta_needed = btf_type_vlen(t) * sizeof(*vsi);
if (meta_left < meta_needed) {
btf_verifier_log_basic(env, t,
"meta_left:%u meta_needed:%u",
meta_left, meta_needed);
return -EINVAL;
}
if (!btf_type_vlen(t)) {
btf_verifier_log_type(env, t, "vlen == 0");
return -EINVAL;
}
if (!t->size) {
btf_verifier_log_type(env, t, "size == 0");
return -EINVAL;
}
if (btf_type_kflag(t)) {
btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
return -EINVAL;
}
if (!t->name_off ||
!btf_name_valid_section(env->btf, t->name_off)) {
btf_verifier_log_type(env, t, "Invalid name");
return -EINVAL;
}
btf_verifier_log_type(env, t, NULL);
for_each_vsi(i, t, vsi) {
/* A var cannot be in type void */
if (!vsi->type || !BTF_TYPE_ID_VALID(vsi->type)) {
btf_verifier_log_vsi(env, t, vsi,
"Invalid type_id");
return -EINVAL;
}
if (vsi->offset < last_vsi_end_off || vsi->offset >= t->size) {
btf_verifier_log_vsi(env, t, vsi,
"Invalid offset");
return -EINVAL;
}
if (!vsi->size || vsi->size > t->size) {
btf_verifier_log_vsi(env, t, vsi,
"Invalid size");
return -EINVAL;
}
last_vsi_end_off = vsi->offset + vsi->size;
if (last_vsi_end_off > t->size) {
btf_verifier_log_vsi(env, t, vsi,
"Invalid offset+size");
return -EINVAL;
}
btf_verifier_log_vsi(env, t, vsi, NULL);
sum += vsi->size;
}
if (t->size < sum) {
btf_verifier_log_type(env, t, "Invalid btf_info size");
return -EINVAL;
}
return meta_needed;
}
static int btf_datasec_resolve(struct btf_verifier_env *env,
const struct resolve_vertex *v)
{
const struct btf_var_secinfo *vsi;
struct btf *btf = env->btf;
u16 i;
for_each_vsi_from(i, v->next_member, v->t, vsi) {
u32 var_type_id = vsi->type, type_id, type_size = 0;
const struct btf_type *var_type = btf_type_by_id(env->btf,
var_type_id);
if (!var_type || !btf_type_is_var(var_type)) {
btf_verifier_log_vsi(env, v->t, vsi,
"Not a VAR kind member");
return -EINVAL;
}
if (!env_type_is_resolve_sink(env, var_type) &&
!env_type_is_resolved(env, var_type_id)) {
env_stack_set_next_member(env, i + 1);
return env_stack_push(env, var_type, var_type_id);
}
type_id = var_type->type;
if (!btf_type_id_size(btf, &type_id, &type_size)) {
btf_verifier_log_vsi(env, v->t, vsi, "Invalid type");
return -EINVAL;
}
if (vsi->size < type_size) {
btf_verifier_log_vsi(env, v->t, vsi, "Invalid size");
return -EINVAL;
}
}
env_stack_pop_resolved(env, 0, 0);
return 0;
}
static void btf_datasec_log(struct btf_verifier_env *env,
const struct btf_type *t)
{
btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}
static void btf_datasec_seq_show(const struct btf *btf,
const struct btf_type *t, u32 type_id,
void *data, u8 bits_offset,
struct seq_file *m)
{
const struct btf_var_secinfo *vsi;
const struct btf_type *var;
u32 i;
seq_printf(m, "section (\"%s\") = {", __btf_name_by_offset(btf, t->name_off));
for_each_vsi(i, t, vsi) {
var = btf_type_by_id(btf, vsi->type);
if (i)
seq_puts(m, ",");
btf_type_ops(var)->seq_show(btf, var, vsi->type,
data + vsi->offset, bits_offset, m);
}
seq_puts(m, "}");
}
static const struct btf_kind_operations datasec_ops = {
.check_meta = btf_datasec_check_meta,
.resolve = btf_datasec_resolve,
.check_member = btf_df_check_member,
.check_kflag_member = btf_df_check_kflag_member,
.log_details = btf_datasec_log,
.seq_show = btf_datasec_seq_show,
};
static int btf_func_proto_check(struct btf_verifier_env *env,
const struct btf_type *t)
{
@ -2542,6 +2913,8 @@ static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS] = {
[BTF_KIND_RESTRICT] = &modifier_ops,
[BTF_KIND_FUNC] = &func_ops,
[BTF_KIND_FUNC_PROTO] = &func_proto_ops,
[BTF_KIND_VAR] = &var_ops,
[BTF_KIND_DATASEC] = &datasec_ops,
};
static s32 btf_check_meta(struct btf_verifier_env *env,
@ -2622,13 +2995,17 @@ static bool btf_resolve_valid(struct btf_verifier_env *env,
if (!env_type_is_resolved(env, type_id))
return false;
if (btf_type_is_struct(t))
if (btf_type_is_struct(t) || btf_type_is_datasec(t))
return !btf->resolved_ids[type_id] &&
!btf->resolved_sizes[type_id];
!btf->resolved_sizes[type_id];
if (btf_type_is_modifier(t) || btf_type_is_ptr(t)) {
if (btf_type_is_modifier(t) || btf_type_is_ptr(t) ||
btf_type_is_var(t)) {
t = btf_type_id_resolve(btf, &type_id);
return t && !btf_type_is_modifier(t);
return t &&
!btf_type_is_modifier(t) &&
!btf_type_is_var(t) &&
!btf_type_is_datasec(t);
}
if (btf_type_is_array(t)) {