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Commit b0588390 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Andrii Nakryiko
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libbpf: Split CO-RE logic into relo_core.c. 

Move CO-RE logic into separate file.
The internal interface between libbpf and CO-RE is through
bpf_core_apply_relo_insn() function and few structs defined in relo_core.h.
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210721000822.40958-5-alexei.starovoitov@gmail.com
parent 301ba4d7
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Showing with 1319 additions and 1297 deletions
tools/lib/bpf/Build
View file @ b0588390
libbpf-y := libbpf.o bpf.o nlattr.o btf.o libbpf_errno.o str_error.o \
netlink.o bpf_prog_linfo.o libbpf_probes.o xsk.o hashmap.o \
btf_dump.o ringbuf.o strset.o linker.o gen_loader.o
btf_dump.o ringbuf.o strset.o linker.o gen_loader.o relo_core.o
tools/lib/bpf/libbpf.c
View file @ b0588390
......@@ -595,11 +595,6 @@ static bool insn_is_subprog_call(const struct bpf_insn *insn)
insn->off == 0;
}
static bool is_ldimm64_insn(struct bpf_insn *insn)
{
return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
}
static bool is_call_insn(const struct bpf_insn *insn)
{
return insn->code == (BPF_JMP | BPF_CALL);
......@@ -4725,279 +4720,6 @@ bpf_object__create_maps(struct bpf_object *obj)
return err;
}
#define BPF_CORE_SPEC_MAX_LEN 64
/* represents BPF CO-RE field or array element accessor */
struct bpf_core_accessor {
__u32 type_id; /* struct/union type or array element type */
__u32 idx; /* field index or array index */
const char *name; /* field name or NULL for array accessor */
};
struct bpf_core_spec {
const struct btf *btf;
/* high-level spec: named fields and array indices only */
struct bpf_core_accessor spec[BPF_CORE_SPEC_MAX_LEN];
/* original unresolved (no skip_mods_or_typedefs) root type ID */
__u32 root_type_id;
/* CO-RE relocation kind */
enum bpf_core_relo_kind relo_kind;
/* high-level spec length */
int len;
/* raw, low-level spec: 1-to-1 with accessor spec string */
int raw_spec[BPF_CORE_SPEC_MAX_LEN];
/* raw spec length */
int raw_len;
/* field bit offset represented by spec */
__u32 bit_offset;
};
static bool str_is_empty(const char *s)
{
return !s || !s[0];
}
static bool is_flex_arr(const struct btf *btf,
const struct bpf_core_accessor *acc,
const struct btf_array *arr)
{
const struct btf_type *t;
/* not a flexible array, if not inside a struct or has non-zero size */
if (!acc->name || arr->nelems > 0)
return false;
/* has to be the last member of enclosing struct */
t = btf__type_by_id(btf, acc->type_id);
return acc->idx == btf_vlen(t) - 1;
}
static const char *core_relo_kind_str(enum bpf_core_relo_kind kind)
{
switch (kind) {
case BPF_FIELD_BYTE_OFFSET: return "byte_off";
case BPF_FIELD_BYTE_SIZE: return "byte_sz";
case BPF_FIELD_EXISTS: return "field_exists";
case BPF_FIELD_SIGNED: return "signed";
case BPF_FIELD_LSHIFT_U64: return "lshift_u64";
case BPF_FIELD_RSHIFT_U64: return "rshift_u64";
case BPF_TYPE_ID_LOCAL: return "local_type_id";
case BPF_TYPE_ID_TARGET: return "target_type_id";
case BPF_TYPE_EXISTS: return "type_exists";
case BPF_TYPE_SIZE: return "type_size";
case BPF_ENUMVAL_EXISTS: return "enumval_exists";
case BPF_ENUMVAL_VALUE: return "enumval_value";
default: return "unknown";
}
}
static bool core_relo_is_field_based(enum bpf_core_relo_kind kind)
{
switch (kind) {
case BPF_FIELD_BYTE_OFFSET:
case BPF_FIELD_BYTE_SIZE:
case BPF_FIELD_EXISTS:
case BPF_FIELD_SIGNED:
case BPF_FIELD_LSHIFT_U64:
case BPF_FIELD_RSHIFT_U64:
return true;
default:
return false;
}
}
static bool core_relo_is_type_based(enum bpf_core_relo_kind kind)
{
switch (kind) {
case BPF_TYPE_ID_LOCAL:
case BPF_TYPE_ID_TARGET:
case BPF_TYPE_EXISTS:
case BPF_TYPE_SIZE:
return true;
default:
return false;
}
}
static bool core_relo_is_enumval_based(enum bpf_core_relo_kind kind)
{
switch (kind) {
case BPF_ENUMVAL_EXISTS:
case BPF_ENUMVAL_VALUE:
return true;
default:
return false;
}
}
/*
* Turn bpf_core_relo into a low- and high-level spec representation,
* validating correctness along the way, as well as calculating resulting
* field bit offset, specified by accessor string. Low-level spec captures
* every single level of nestedness, including traversing anonymous
* struct/union members. High-level one only captures semantically meaningful
* "turning points": named fields and array indicies.
* E.g., for this case:
*
* struct sample {
* int __unimportant;
* struct {
* int __1;
* int __2;
* int a[7];
* };
* };
*
* struct sample *s = ...;
*
* int x = &s->a[3]; // access string = '0:1:2:3'
*
* Low-level spec has 1:1 mapping with each element of access string (it's
* just a parsed access string representation): [0, 1, 2, 3].
*
* High-level spec will capture only 3 points:
* - intial zero-index access by pointer (&s->... is the same as &s[0]...);
* - 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_ID_LOCAL/TYPE_ID_TARGET) don't capture any field information. Their
* spec and raw_spec are kept empty.
*
* Enum value-based relocations (ENUMVAL_EXISTS/ENUMVAL_VALUE) use access
* string to specify enumerator's value index that need to be relocated.
*/
static int bpf_core_parse_spec(const struct btf *btf,
__u32 type_id,
const char *spec_str,
enum bpf_core_relo_kind relo_kind,
struct bpf_core_spec *spec)
{
int access_idx, parsed_len, i;
struct bpf_core_accessor *acc;
const struct btf_type *t;
const char *name;
__u32 id;
__s64 sz;
if (str_is_empty(spec_str) || *spec_str == ':')
return -EINVAL;
memset(spec, 0, sizeof(*spec));
spec->btf = btf;
spec->root_type_id = type_id;
spec->relo_kind = relo_kind;
/* type-based relocations don't have a field access string */
if (core_relo_is_type_based(relo_kind)) {
if (strcmp(spec_str, "0"))
return -EINVAL;
return 0;
}
/* parse spec_str="0:1:2:3:4" into array raw_spec=[0, 1, 2, 3, 4] */
while (*spec_str) {
if (*spec_str == ':')
++spec_str;
if (sscanf(spec_str, "%d%n", &access_idx, &parsed_len) != 1)
return -EINVAL;
if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
return -E2BIG;
spec_str += parsed_len;
spec->raw_spec[spec->raw_len++] = access_idx;
}
if (spec->raw_len == 0)
return -EINVAL;
t = skip_mods_and_typedefs(btf, type_id, &id);
if (!t)
return -EINVAL;
access_idx = spec->raw_spec[0];
acc = &spec->spec[0];
acc->type_id = id;
acc->idx = access_idx;
spec->len++;
if (core_relo_is_enumval_based(relo_kind)) {
if (!btf_is_enum(t) || spec->raw_len > 1 || access_idx >= btf_vlen(t))
return -EINVAL;
/* record enumerator name in a first accessor */
acc->name = btf__name_by_offset(btf, btf_enum(t)[access_idx].name_off);
return 0;
}
if (!core_relo_is_field_based(relo_kind))
return -EINVAL;
sz = btf__resolve_size(btf, id);
if (sz < 0)
return sz;
spec->bit_offset = access_idx * sz * 8;
for (i = 1; i < spec->raw_len; i++) {
t = skip_mods_and_typedefs(btf, id, &id);
if (!t)
return -EINVAL;
access_idx = spec->raw_spec[i];
acc = &spec->spec[spec->len];
if (btf_is_composite(t)) {
const struct btf_member *m;
__u32 bit_offset;
if (access_idx >= btf_vlen(t))
return -EINVAL;
bit_offset = btf_member_bit_offset(t, access_idx);
spec->bit_offset += bit_offset;
m = btf_members(t) + access_idx;
if (m->name_off) {
name = btf__name_by_offset(btf, m->name_off);
if (str_is_empty(name))
return -EINVAL;
acc->type_id = id;
acc->idx = access_idx;
acc->name = name;
spec->len++;
}
id = m->type;
} else if (btf_is_array(t)) {
const struct btf_array *a = btf_array(t);
bool flex;
t = skip_mods_and_typedefs(btf, a->type, &id);
if (!t)
return -EINVAL;
flex = is_flex_arr(btf, acc - 1, a);
if (!flex && access_idx >= a->nelems)
return -EINVAL;
spec->spec[spec->len].type_id = id;
spec->spec[spec->len].idx = access_idx;
spec->len++;
sz = btf__resolve_size(btf, id);
if (sz < 0)
return sz;
spec->bit_offset += access_idx * sz * 8;
} else {
pr_warn("relo for [%u] %s (at idx %d) captures type [%d] of unexpected kind %s\n",
type_id, spec_str, i, id, btf_kind_str(t));
return -EINVAL;
}
}
return 0;
}
static bool bpf_core_is_flavor_sep(const char *s)
{
/* check X___Y name pattern, where X and Y are not underscores */
......@@ -5010,7 +4732,7 @@ static bool bpf_core_is_flavor_sep(const char *s)
* before last triple underscore. Struct name part after last triple
* underscore is ignored by BPF CO-RE relocation during relocation matching.
*/
static size_t bpf_core_essential_name_len(const char *name)
size_t bpf_core_essential_name_len(const char *name)
{
size_t n = strlen(name);
int i;
......@@ -5229,165 +4951,6 @@ bpf_core_find_cands(struct bpf_object *obj, const struct btf *local_btf, __u32 l
return ERR_PTR(err);
}
/* Check two types for compatibility for the purpose of field access
* relocation. const/volatile/restrict and typedefs are skipped to ensure we
* are relocating semantically compatible entities:
* - any two STRUCTs/UNIONs are compatible and can be mixed;
* - any two FWDs are compatible, if their names match (modulo flavor suffix);
* - any two PTRs are always compatible;
* - for ENUMs, names should be the same (ignoring flavor suffix) or at
* least one of enums should be anonymous;
* - for ENUMs, check sizes, names are ignored;
* - for INT, size and signedness are ignored;
* - any two FLOATs are always compatible;
* - for ARRAY, dimensionality is ignored, element types are checked for
* compatibility recursively;
* - everything else shouldn't be ever a target of relocation.
* These rules are not set in stone and probably will be adjusted as we get
* more experience with using BPF CO-RE relocations.
*/
static int bpf_core_fields_are_compat(const struct btf *local_btf,
__u32 local_id,
const struct btf *targ_btf,
__u32 targ_id)
{
const struct btf_type *local_type, *targ_type;
recur:
local_type = skip_mods_and_typedefs(local_btf, local_id, &local_id);
targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
if (!local_type || !targ_type)
return -EINVAL;
if (btf_is_composite(local_type) && btf_is_composite(targ_type))
return 1;
if (btf_kind(local_type) != btf_kind(targ_type))
return 0;
switch (btf_kind(local_type)) {
case BTF_KIND_PTR:
case BTF_KIND_FLOAT:
return 1;
case BTF_KIND_FWD:
case BTF_KIND_ENUM: {
const char *local_name, *targ_name;
size_t local_len, targ_len;
local_name = btf__name_by_offset(local_btf,
local_type->name_off);
targ_name = btf__name_by_offset(targ_btf, targ_type->name_off);
local_len = bpf_core_essential_name_len(local_name);
targ_len = bpf_core_essential_name_len(targ_name);
/* one of them is anonymous or both w/ same flavor-less names */
return local_len == 0 || targ_len == 0 ||
(local_len == targ_len &&
strncmp(local_name, targ_name, local_len) == 0);
}
case BTF_KIND_INT:
/* just reject deprecated bitfield-like integers; all other
* integers are by default compatible between each other
*/
return btf_int_offset(local_type) == 0 &&
btf_int_offset(targ_type) == 0;
case BTF_KIND_ARRAY:
local_id = btf_array(local_type)->type;
targ_id = btf_array(targ_type)->type;
goto recur;
default:
pr_warn("unexpected kind %d relocated, local [%d], target [%d]\n",
btf_kind(local_type), local_id, targ_id);
return 0;
}
}
/*
* Given single high-level named field accessor in local type, find
* corresponding high-level accessor for a target type. Along the way,
* maintain low-level spec for target as well. Also keep updating target
* bit offset.
*
* Searching is performed through recursive exhaustive enumeration of all
* fields of a struct/union. If there are any anonymous (embedded)
* structs/unions, they are recursively searched as well. If field with
* desired name is found, check compatibility between local and target types,
* before returning result.
*
* 1 is returned, if field is found.
* 0 is returned if no compatible field is found.
* <0 is returned on error.
*/
static int bpf_core_match_member(const struct btf *local_btf,
const struct bpf_core_accessor *local_acc,
const struct btf *targ_btf,
__u32 targ_id,
struct bpf_core_spec *spec,
__u32 *next_targ_id)
{
const struct btf_type *local_type, *targ_type;
const struct btf_member *local_member, *m;
const char *local_name, *targ_name;
__u32 local_id;
int i, n, found;
targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
if (!targ_type)
return -EINVAL;
if (!btf_is_composite(targ_type))
return 0;
local_id = local_acc->type_id;
local_type = btf__type_by_id(local_btf, local_id);
local_member = btf_members(local_type) + local_acc->idx;
local_name = btf__name_by_offset(local_btf, local_member->name_off);
n = btf_vlen(targ_type);
m = btf_members(targ_type);
for (i = 0; i < n; i++, m++) {
__u32 bit_offset;
bit_offset = btf_member_bit_offset(targ_type, i);
/* too deep struct/union/array nesting */
if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
return -E2BIG;
/* speculate this member will be the good one */
spec->bit_offset += bit_offset;
spec->raw_spec[spec->raw_len++] = i;
targ_name = btf__name_by_offset(targ_btf, m->name_off);
if (str_is_empty(targ_name)) {
/* embedded struct/union, we need to go deeper */
found = bpf_core_match_member(local_btf, local_acc,
targ_btf, m->type,
spec, next_targ_id);
if (found) /* either found or error */
return found;
} else if (strcmp(local_name, targ_name) == 0) {
/* matching named field */
struct bpf_core_accessor *targ_acc;
targ_acc = &spec->spec[spec->len++];
targ_acc->type_id = targ_id;
targ_acc->idx = i;
targ_acc->name = targ_name;
*next_targ_id = m->type;
found = bpf_core_fields_are_compat(local_btf,
local_member->type,
targ_btf, m->type);
if (!found)
spec->len--; /* pop accessor */
return found;
}
/* member turned out not to be what we looked for */
spec->bit_offset -= bit_offset;
spec->raw_len--;
}
return 0;
}
/* Check local and target types for compatibility. This check is used for
* type-based CO-RE relocations and follow slightly different rules than
* field-based relocations. This function assumes that root types were already
......@@ -5407,8 +4970,8 @@ static int bpf_core_match_member(const struct btf *local_btf,
* These rules are not set in stone and probably will be adjusted as we get
* more experience with using BPF CO-RE relocations.
*/
static 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_are_compat(const struct btf *local_btf, __u32 local_id,
const struct btf *targ_btf, __u32 targ_id)
{
const struct btf_type *local_type, *targ_type;
int depth = 32; /* max recursion depth */
......@@ -5482,658 +5045,6 @@ static int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id
}
}
/*
* Try to match local spec to a target type and, if successful, produce full
* target spec (high-level, low-level + bit offset).
*/
static int bpf_core_spec_match(struct bpf_core_spec *local_spec,
const struct btf *targ_btf, __u32 targ_id,
struct bpf_core_spec *targ_spec)
{
const struct btf_type *targ_type;
const struct bpf_core_accessor *local_acc;
struct bpf_core_accessor *targ_acc;
int i, sz, matched;
memset(targ_spec, 0, sizeof(*targ_spec));
targ_spec->btf = targ_btf;
targ_spec->root_type_id = targ_id;
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);
}
local_acc = &local_spec->spec[0];
targ_acc = &targ_spec->spec[0];
if (core_relo_is_enumval_based(local_spec->relo_kind)) {
size_t local_essent_len, targ_essent_len;
const struct btf_enum *e;
const char *targ_name;
/* has to resolve to an enum */
targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id, &targ_id);
if (!btf_is_enum(targ_type))
return 0;
local_essent_len = bpf_core_essential_name_len(local_acc->name);
for (i = 0, e = btf_enum(targ_type); i < btf_vlen(targ_type); i++, e++) {
targ_name = btf__name_by_offset(targ_spec->btf, e->name_off);
targ_essent_len = bpf_core_essential_name_len(targ_name);
if (targ_essent_len != local_essent_len)
continue;
if (strncmp(local_acc->name, targ_name, local_essent_len) == 0) {
targ_acc->type_id = targ_id;
targ_acc->idx = i;
targ_acc->name = targ_name;
targ_spec->len++;
targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx;
targ_spec->raw_len++;
return 1;
}
}
return 0;
}
if (!core_relo_is_field_based(local_spec->relo_kind))
return -EINVAL;
for (i = 0; i < local_spec->len; i++, local_acc++, targ_acc++) {
targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id,
&targ_id);
if (!targ_type)
return -EINVAL;
if (local_acc->name) {
matched = bpf_core_match_member(local_spec->btf,
local_acc,
targ_btf, targ_id,
targ_spec, &targ_id);
if (matched <= 0)
return matched;
} else {
/* for i=0, targ_id is already treated as array element
* type (because it's the original struct), for others
* we should find array element type first
*/
if (i > 0) {
const struct btf_array *a;
bool flex;
if (!btf_is_array(targ_type))
return 0;
a = btf_array(targ_type);
flex = is_flex_arr(targ_btf, targ_acc - 1, a);
if (!flex && local_acc->idx >= a->nelems)
return 0;
if (!skip_mods_and_typedefs(targ_btf, a->type,
&targ_id))
return -EINVAL;
}
/* too deep struct/union/array nesting */
if (targ_spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
return -E2BIG;
targ_acc->type_id = targ_id;
targ_acc->idx = local_acc->idx;
targ_acc->name = NULL;
targ_spec->len++;
targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx;
targ_spec->raw_len++;
sz = btf__resolve_size(targ_btf, targ_id);
if (sz < 0)
return sz;
targ_spec->bit_offset += local_acc->idx * sz * 8;
}
}
return 1;
}
static int bpf_core_calc_field_relo(const char *prog_name,
const struct bpf_core_relo *relo,
const struct bpf_core_spec *spec,
__u32 *val, __u32 *field_sz, __u32 *type_id,
bool *validate)
{
const struct bpf_core_accessor *acc;
const struct btf_type *t;
__u32 byte_off, byte_sz, bit_off, bit_sz, field_type_id;
const struct btf_member *m;
const struct btf_type *mt;
bool bitfield;
__s64 sz;
*field_sz = 0;
if (relo->kind == BPF_FIELD_EXISTS) {
*val = spec ? 1 : 0;
return 0;
}
if (!spec)
return -EUCLEAN; /* request instruction poisoning */
acc = &spec->spec[spec->len - 1];
t = btf__type_by_id(spec->btf, acc->type_id);
/* a[n] accessor needs special handling */
if (!acc->name) {
if (relo->kind == BPF_FIELD_BYTE_OFFSET) {
*val = spec->bit_offset / 8;
/* remember field size for load/store mem size */
sz = btf__resolve_size(spec->btf, acc->type_id);
if (sz < 0)
return -EINVAL;
*field_sz = sz;
*type_id = acc->type_id;
} else if (relo->kind == BPF_FIELD_BYTE_SIZE) {
sz = btf__resolve_size(spec->btf, acc->type_id);
if (sz < 0)
return -EINVAL;
*val = sz;
} else {
pr_warn("prog '%s': relo %d at insn #%d can't be applied to array access\n",
prog_name, relo->kind, relo->insn_off / 8);
return -EINVAL;
}
if (validate)
*validate = true;
return 0;
}
m = btf_members(t) + acc->idx;
mt = skip_mods_and_typedefs(spec->btf, m->type, &field_type_id);
bit_off = spec->bit_offset;
bit_sz = btf_member_bitfield_size(t, acc->idx);
bitfield = bit_sz > 0;
if (bitfield) {
byte_sz = mt->size;
byte_off = bit_off / 8 / byte_sz * byte_sz;
/* figure out smallest int size necessary for bitfield load */
while (bit_off + bit_sz - byte_off * 8 > byte_sz * 8) {
if (byte_sz >= 8) {
/* bitfield can't be read with 64-bit read */
pr_warn("prog '%s': relo %d at insn #%d can't be satisfied for bitfield\n",
prog_name, relo->kind, relo->insn_off / 8);
return -E2BIG;
}
byte_sz *= 2;
byte_off = bit_off / 8 / byte_sz * byte_sz;
}
} else {
sz = btf__resolve_size(spec->btf, field_type_id);
if (sz < 0)
return -EINVAL;
byte_sz = sz;
byte_off = spec->bit_offset / 8;
bit_sz = byte_sz * 8;
}
/* for bitfields, all the relocatable aspects are ambiguous and we
* might disagree with compiler, so turn off validation of expected
* value, except for signedness
*/
if (validate)
*validate = !bitfield;
switch (relo->kind) {
case BPF_FIELD_BYTE_OFFSET:
*val = byte_off;
if (!bitfield) {
*field_sz = byte_sz;
*type_id = field_type_id;
}
break;
case BPF_FIELD_BYTE_SIZE:
*val = byte_sz;
break;
case BPF_FIELD_SIGNED:
/* enums will be assumed unsigned */
*val = btf_is_enum(mt) ||
(btf_int_encoding(mt) & BTF_INT_SIGNED);
if (validate)
*validate = true; /* signedness is never ambiguous */
break;
case BPF_FIELD_LSHIFT_U64:
#if __BYTE_ORDER == __LITTLE_ENDIAN
*val = 64 - (bit_off + bit_sz - byte_off * 8);
#else
*val = (8 - byte_sz) * 8 + (bit_off - byte_off * 8);
#endif
break;
case BPF_FIELD_RSHIFT_U64:
*val = 64 - bit_sz;
if (validate)
*validate = true; /* right shift is never ambiguous */
break;
case BPF_FIELD_EXISTS:
default:
return -EOPNOTSUPP;
}
return 0;
}
static int bpf_core_calc_type_relo(const struct bpf_core_relo *relo,
const struct bpf_core_spec *spec,
__u32 *val)
{
__s64 sz;
/* type-based relos return zero when target type is not found */
if (!spec) {
*val = 0;
return 0;
}
switch (relo->kind) {
case BPF_TYPE_ID_TARGET:
*val = spec->root_type_id;
break;
case BPF_TYPE_EXISTS:
*val = 1;
break;
case BPF_TYPE_SIZE:
sz = btf__resolve_size(spec->btf, spec->root_type_id);
if (sz < 0)
return -EINVAL;
*val = sz;
break;
case BPF_TYPE_ID_LOCAL:
/* BPF_TYPE_ID_LOCAL is handled specially and shouldn't get here */
default:
return -EOPNOTSUPP;
}
return 0;
}
static int bpf_core_calc_enumval_relo(const struct bpf_core_relo *relo,
const struct bpf_core_spec *spec,
__u32 *val)
{
const struct btf_type *t;
const struct btf_enum *e;
switch (relo->kind) {
case BPF_ENUMVAL_EXISTS:
*val = spec ? 1 : 0;
break;
case BPF_ENUMVAL_VALUE:
if (!spec)
return -EUCLEAN; /* request instruction poisoning */
t = btf__type_by_id(spec->btf, spec->spec[0].type_id);
e = btf_enum(t) + spec->spec[0].idx;
*val = e->val;
break;
default:
return -EOPNOTSUPP;
}
return 0;
}
struct bpf_core_relo_res
{
/* expected value in the instruction, unless validate == false */
__u32 orig_val;
/* new value that needs to be patched up to */
__u32 new_val;
/* relocation unsuccessful, poison instruction, but don't fail load */
bool poison;
/* some relocations can't be validated against orig_val */
bool validate;
/* for field byte offset relocations or the forms:
* *(T *)(rX + <off>) = rY
* rX = *(T *)(rY + <off>),
* we remember original and resolved field size to adjust direct
* memory loads of pointers and integers; this is necessary for 32-bit
* host kernel architectures, but also allows to automatically
* relocate fields that were resized from, e.g., u32 to u64, etc.
*/
bool fail_memsz_adjust;
__u32 orig_sz;
__u32 orig_type_id;
__u32 new_sz;
__u32 new_type_id;
};
/* Calculate original and target relocation values, given local and target
* specs and relocation kind. These values are calculated for each candidate.
* If there are multiple candidates, resulting values should all be consistent
* with each other. Otherwise, libbpf will refuse to proceed due to ambiguity.
* If instruction has to be poisoned, *poison will be set to true.
*/
static int bpf_core_calc_relo(const char *prog_name,
const struct bpf_core_relo *relo,
int relo_idx,
const struct bpf_core_spec *local_spec,
const struct bpf_core_spec *targ_spec,
struct bpf_core_relo_res *res)
{
int err = -EOPNOTSUPP;
res->orig_val = 0;
res->new_val = 0;
res->poison = false;
res->validate = true;
res->fail_memsz_adjust = false;
res->orig_sz = res->new_sz = 0;
res->orig_type_id = res->new_type_id = 0;
if (core_relo_is_field_based(relo->kind)) {
err = bpf_core_calc_field_relo(prog_name, relo, local_spec,
&res->orig_val, &res->orig_sz,
&res->orig_type_id, &res->validate);
err = err ?: bpf_core_calc_field_relo(prog_name, relo, targ_spec,
&res->new_val, &res->new_sz,
&res->new_type_id, NULL);
if (err)
goto done;
/* Validate if it's safe to adjust load/store memory size.
* Adjustments are performed only if original and new memory
* sizes differ.
*/
res->fail_memsz_adjust = false;
if (res->orig_sz != res->new_sz) {
const struct btf_type *orig_t, *new_t;
orig_t = btf__type_by_id(local_spec->btf, res->orig_type_id);
new_t = btf__type_by_id(targ_spec->btf, res->new_type_id);
/* There are two use cases in which it's safe to
* adjust load/store's mem size:
* - reading a 32-bit kernel pointer, while on BPF
* size pointers are always 64-bit; in this case
* it's safe to "downsize" instruction size due to
* pointer being treated as unsigned integer with
* zero-extended upper 32-bits;
* - reading unsigned integers, again due to
* zero-extension is preserving the value correctly.
*
* In all other cases it's incorrect to attempt to
* load/store field because read value will be
* incorrect, so we poison relocated instruction.
*/
if (btf_is_ptr(orig_t) && btf_is_ptr(new_t))
goto done;
if (btf_is_int(orig_t) && btf_is_int(new_t) &&
btf_int_encoding(orig_t) != BTF_INT_SIGNED &&
btf_int_encoding(new_t) != BTF_INT_SIGNED)
goto done;
/* mark as invalid mem size adjustment, but this will
* only be checked for LDX/STX/ST insns
*/
res->fail_memsz_adjust = true;
}
} else if (core_relo_is_type_based(relo->kind)) {
err = bpf_core_calc_type_relo(relo, local_spec, &res->orig_val);
err = err ?: bpf_core_calc_type_relo(relo, targ_spec, &res->new_val);
} else if (core_relo_is_enumval_based(relo->kind)) {
err = bpf_core_calc_enumval_relo(relo, local_spec, &res->orig_val);
err = err ?: bpf_core_calc_enumval_relo(relo, targ_spec, &res->new_val);
}
done:
if (err == -EUCLEAN) {
/* EUCLEAN is used to signal instruction poisoning request */
res->poison = true;
err = 0;
} else if (err == -EOPNOTSUPP) {
/* EOPNOTSUPP means unknown/unsupported relocation */
pr_warn("prog '%s': relo #%d: unrecognized CO-RE relocation %s (%d) at insn #%d\n",
prog_name, relo_idx, core_relo_kind_str(relo->kind),
relo->kind, relo->insn_off / 8);
}
return err;
}
/*
* Turn instruction for which CO_RE relocation failed into invalid one with
* distinct signature.
*/
static void bpf_core_poison_insn(const char *prog_name, int relo_idx,
int insn_idx, struct bpf_insn *insn)
{
pr_debug("prog '%s': relo #%d: substituting insn #%d w/ invalid insn\n",
prog_name, relo_idx, insn_idx);
insn->code = BPF_JMP | BPF_CALL;
insn->dst_reg = 0;
insn->src_reg = 0;
insn->off = 0;
/* if this instruction is reachable (not a dead code),
* verifier will complain with the following message:
* invalid func unknown#195896080
*/
insn->imm = 195896080; /* => 0xbad2310 => "bad relo" */
}
static int insn_bpf_size_to_bytes(struct bpf_insn *insn)
{
switch (BPF_SIZE(insn->code)) {
case BPF_DW: return 8;
case BPF_W: return 4;
case BPF_H: return 2;
case BPF_B: return 1;
default: return -1;
}
}
static int insn_bytes_to_bpf_size(__u32 sz)
{
switch (sz) {
case 8: return BPF_DW;
case 4: return BPF_W;
case 2: return BPF_H;
case 1: return BPF_B;
default: return -1;
}
}
/*
* Patch relocatable BPF instruction.
*
* Patched value is determined by relocation kind and target specification.
* For existence relocations target spec will be NULL if field/type is not found.
* Expected insn->imm value is determined using relocation kind and local
* spec, and is checked before patching instruction. If actual insn->imm value
* is wrong, bail out with error.
*
* Currently supported classes of BPF instruction are:
* 1. rX = <imm> (assignment with immediate operand);
* 2. rX += <imm> (arithmetic operations with immediate operand);
* 3. rX = <imm64> (load with 64-bit immediate value);
* 4. rX = *(T *)(rY + <off>), where T is one of {u8, u16, u32, u64};
* 5. *(T *)(rX + <off>) = rY, where T is one of {u8, u16, u32, u64};
* 6. *(T *)(rX + <off>) = <imm>, where T is one of {u8, u16, u32, u64}.
*/
static int bpf_core_patch_insn(const char *prog_name, struct bpf_insn *insn,
int insn_idx, const struct bpf_core_relo *relo,
int relo_idx, const struct bpf_core_relo_res *res)
{
__u32 orig_val, new_val;
__u8 class;
class = BPF_CLASS(insn->code);
if (res->poison) {
poison:
/* poison second part of ldimm64 to avoid confusing error from
* verifier about "unknown opcode 00"
*/
if (is_ldimm64_insn(insn))
bpf_core_poison_insn(prog_name, relo_idx, insn_idx + 1, insn + 1);
bpf_core_poison_insn(prog_name, relo_idx, insn_idx, insn);
return 0;
}
orig_val = res->orig_val;
new_val = res->new_val;
switch (class) {
case BPF_ALU:
case BPF_ALU64:
if (BPF_SRC(insn->code) != BPF_K)
return -EINVAL;
if (res->validate && insn->imm != orig_val) {
pr_warn("prog '%s': relo #%d: unexpected insn #%d (ALU/ALU64) value: got %u, exp %u -> %u\n",
prog_name, relo_idx,
insn_idx, insn->imm, orig_val, new_val);
return -EINVAL;
}
orig_val = insn->imm;
insn->imm = new_val;
pr_debug("prog '%s': relo #%d: patched insn #%d (ALU/ALU64) imm %u -> %u\n",
prog_name, relo_idx, insn_idx,
orig_val, new_val);
break;
case BPF_LDX:
case BPF_ST:
case BPF_STX:
if (res->validate && insn->off != orig_val) {
pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDX/ST/STX) value: got %u, exp %u -> %u\n",
prog_name, relo_idx, insn_idx, insn->off, orig_val, new_val);
return -EINVAL;
}
if (new_val > SHRT_MAX) {
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) value too big: %u\n",
prog_name, relo_idx, insn_idx, new_val);
return -ERANGE;
}
if (res->fail_memsz_adjust) {
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) accesses field incorrectly. "
"Make sure you are accessing pointers, unsigned integers, or fields of matching type and size.\n",
prog_name, relo_idx, insn_idx);
goto poison;
}
orig_val = insn->off;
insn->off = new_val;
pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) off %u -> %u\n",
prog_name, relo_idx, insn_idx, orig_val, new_val);
if (res->new_sz != res->orig_sz) {
int insn_bytes_sz, insn_bpf_sz;
insn_bytes_sz = insn_bpf_size_to_bytes(insn);
if (insn_bytes_sz != res->orig_sz) {
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) unexpected mem size: got %d, exp %u\n",
prog_name, relo_idx, insn_idx, insn_bytes_sz, res->orig_sz);
return -EINVAL;
}
insn_bpf_sz = insn_bytes_to_bpf_size(res->new_sz);
if (insn_bpf_sz < 0) {
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) invalid new mem size: %u\n",
prog_name, relo_idx, insn_idx, res->new_sz);
return -EINVAL;
}
insn->code = BPF_MODE(insn->code) | insn_bpf_sz | BPF_CLASS(insn->code);
pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) mem_sz %u -> %u\n",
prog_name, relo_idx, insn_idx, res->orig_sz, res->new_sz);
}
break;
case BPF_LD: {
__u64 imm;
if (!is_ldimm64_insn(insn) ||
insn[0].src_reg != 0 || insn[0].off != 0 ||
insn[1].code != 0 || insn[1].dst_reg != 0 ||
insn[1].src_reg != 0 || insn[1].off != 0) {
pr_warn("prog '%s': relo #%d: insn #%d (LDIMM64) has unexpected form\n",
prog_name, relo_idx, insn_idx);
return -EINVAL;
}
imm = insn[0].imm + ((__u64)insn[1].imm << 32);
if (res->validate && imm != orig_val) {
pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDIMM64) value: got %llu, exp %u -> %u\n",
prog_name, relo_idx,
insn_idx, (unsigned long long)imm,
orig_val, new_val);
return -EINVAL;
}
insn[0].imm = new_val;
insn[1].imm = 0; /* currently only 32-bit values are supported */
pr_debug("prog '%s': relo #%d: patched insn #%d (LDIMM64) imm64 %llu -> %u\n",
prog_name, relo_idx, insn_idx,
(unsigned long long)imm, new_val);
break;
}
default:
pr_warn("prog '%s': relo #%d: trying to relocate unrecognized insn #%d, code:0x%x, src:0x%x, dst:0x%x, off:0x%x, imm:0x%x\n",
prog_name, relo_idx, insn_idx, insn->code,
insn->src_reg, insn->dst_reg, insn->off, insn->imm);
return -EINVAL;
}
return 0;
}
/* Output spec definition in the format:
* [<type-id>] (<type-name>) + <raw-spec> => <offset>@<spec>,
* where <spec> is a C-syntax view of recorded field access, e.g.: x.a[3].b
*/
static void bpf_core_dump_spec(int level, const struct bpf_core_spec *spec)
{
const struct btf_type *t;
const struct btf_enum *e;
const char *s;
__u32 type_id;
int i;
type_id = spec->root_type_id;
t = btf__type_by_id(spec->btf, type_id);
s = btf__name_by_offset(spec->btf, t->name_off);
libbpf_print(level, "[%u] %s %s", type_id, btf_kind_str(t), str_is_empty(s) ? "<anon>" : s);
if (core_relo_is_type_based(spec->relo_kind))
return;
if (core_relo_is_enumval_based(spec->relo_kind)) {
t = skip_mods_and_typedefs(spec->btf, type_id, NULL);
e = btf_enum(t) + spec->raw_spec[0];
s = btf__name_by_offset(spec->btf, e->name_off);
libbpf_print(level, "::%s = %u", s, e->val);
return;
}
if (core_relo_is_field_based(spec->relo_kind)) {
for (i = 0; i < spec->len; i++) {
if (spec->spec[i].name)
libbpf_print(level, ".%s", spec->spec[i].name);
else if (i > 0 || spec->spec[i].idx > 0)
libbpf_print(level, "[%u]", spec->spec[i].idx);
}
libbpf_print(level, " (");
for (i = 0; i < spec->raw_len; i++)
libbpf_print(level, "%s%d", i == 0 ? "" : ":", spec->raw_spec[i]);
if (spec->bit_offset % 8)
libbpf_print(level, " @ offset %u.%u)",
spec->bit_offset / 8, spec->bit_offset % 8);
else
libbpf_print(level, " @ offset %u)", spec->bit_offset / 8);
return;
}
}
static size_t bpf_core_hash_fn(const void *key, void *ctx)
{
return (size_t)key;
......@@ -6149,208 +5060,6 @@ static void *u32_as_hash_key(__u32 x)
return (void *)(uintptr_t)x;
}
/*
* CO-RE relocate single instruction.
*
* The outline and important points of the algorithm:
* 1. For given local type, find corresponding candidate target types.
* Candidate type is a type with the same "essential" name, ignoring
* everything after last triple underscore (___). E.g., `sample`,
* `sample___flavor_one`, `sample___flavor_another_one`, are all candidates
* for each other. Names with triple underscore are referred to as
* "flavors" and are useful, among other things, to allow to
* specify/support incompatible variations of the same kernel struct, which
* might differ between different kernel versions and/or build
* configurations.
*
* N.B. Struct "flavors" could be generated by bpftool's BTF-to-C
* converter, when deduplicated BTF of a kernel still contains more than
* one different types with the same name. In that case, ___2, ___3, etc
* are appended starting from second name conflict. But start flavors are
* also useful to be defined "locally", in BPF program, to extract same
* data from incompatible changes between different kernel
* versions/configurations. For instance, to handle field renames between
* kernel versions, one can use two flavors of the struct name with the
* same common name and use conditional relocations to extract that field,
* depending on target kernel version.
* 2. For each candidate type, try to match local specification to this
* candidate target type. Matching involves finding corresponding
* high-level spec accessors, meaning that all named fields should match,
* as well as all array accesses should be within the actual bounds. Also,
* types should be compatible (see bpf_core_fields_are_compat for details).
* 3. It is supported and expected that there might be multiple flavors
* matching the spec. As long as all the specs resolve to the same set of
* offsets across all candidates, there is no error. If there is any
* ambiguity, CO-RE relocation will fail. This is necessary to accomodate
* imprefection of BTF deduplication, which can cause slight duplication of
* the same BTF type, if some directly or indirectly referenced (by
* pointer) type gets resolved to different actual types in different
* object files. If such situation occurs, deduplicated BTF will end up
* with two (or more) structurally identical types, which differ only in
* types they refer to through pointer. This should be OK in most cases and
* is not an error.
* 4. Candidate types search is performed by linearly scanning through all
* types in target BTF. It is anticipated that this is overall more
* efficient memory-wise and not significantly worse (if not better)
* CPU-wise compared to prebuilding a map from all local type names to
* a list of candidate type names. It's also sped up by caching resolved
* list of matching candidates per each local "root" type ID, that has at
* least one bpf_core_relo associated with it. This list is shared
* between multiple relocations for the same type ID and is updated as some
* of the candidates are pruned due to structural incompatibility.
*/
static int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
int insn_idx,
const struct bpf_core_relo *relo,
int relo_idx,
const struct btf *local_btf,
struct bpf_core_cand_list *cands)
{
struct bpf_core_spec local_spec, cand_spec, targ_spec = {};
struct bpf_core_relo_res cand_res, targ_res;
const struct btf_type *local_type;
const char *local_name;
__u32 local_id;
const char *spec_str;
int i, j, err;
local_id = relo->type_id;
local_type = btf__type_by_id(local_btf, local_id);
if (!local_type)
return -EINVAL;
local_name = btf__name_by_offset(local_btf, local_type->name_off);
if (!local_name)
return -EINVAL;
spec_str = btf__name_by_offset(local_btf, relo->access_str_off);
if (str_is_empty(spec_str))
return -EINVAL;
err = bpf_core_parse_spec(local_btf, local_id, spec_str, relo->kind, &local_spec);
if (err) {
pr_warn("prog '%s': relo #%d: parsing [%d] %s %s + %s failed: %d\n",
prog_name, relo_idx, local_id, btf_kind_str(local_type),
str_is_empty(local_name) ? "<anon>" : local_name,
spec_str, err);
return -EINVAL;
}
pr_debug("prog '%s': relo #%d: kind <%s> (%d), spec is ", prog_name,
relo_idx, core_relo_kind_str(relo->kind), relo->kind);
bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
libbpf_print(LIBBPF_DEBUG, "\n");
/* TYPE_ID_LOCAL relo is special and doesn't need candidate search */
if (relo->kind == BPF_TYPE_ID_LOCAL) {
targ_res.validate = true;
targ_res.poison = false;
targ_res.orig_val = local_spec.root_type_id;
targ_res.new_val = local_spec.root_type_id;
goto patch_insn;
}
/* libbpf doesn't support candidate search for anonymous types */
if (str_is_empty(spec_str)) {
pr_warn("prog '%s': relo #%d: <%s> (%d) relocation doesn't support anonymous types\n",
prog_name, relo_idx, core_relo_kind_str(relo->kind), relo->kind);
return -EOPNOTSUPP;
}
for (i = 0, j = 0; i < cands->len; i++) {
err = bpf_core_spec_match(&local_spec, cands->cands[i].btf,
cands->cands[i].id, &cand_spec);
if (err < 0) {
pr_warn("prog '%s': relo #%d: error matching candidate #%d ",
prog_name, relo_idx, i);
bpf_core_dump_spec(LIBBPF_WARN, &cand_spec);
libbpf_print(LIBBPF_WARN, ": %d\n", err);
return err;
}
pr_debug("prog '%s': relo #%d: %s candidate #%d ", prog_name,
relo_idx, err == 0 ? "non-matching" : "matching", i);
bpf_core_dump_spec(LIBBPF_DEBUG, &cand_spec);
libbpf_print(LIBBPF_DEBUG, "\n");
if (err == 0)
continue;
err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, &cand_spec, &cand_res);
if (err)
return err;
if (j == 0) {
targ_res = cand_res;
targ_spec = cand_spec;
} else if (cand_spec.bit_offset != targ_spec.bit_offset) {
/* if there are many field relo candidates, they
* should all resolve to the same bit offset
*/
pr_warn("prog '%s': relo #%d: field offset ambiguity: %u != %u\n",
prog_name, relo_idx, cand_spec.bit_offset,
targ_spec.bit_offset);
return -EINVAL;
} else if (cand_res.poison != targ_res.poison || cand_res.new_val != targ_res.new_val) {
/* all candidates should result in the same relocation
* decision and value, otherwise it's dangerous to
* proceed due to ambiguity
*/
pr_warn("prog '%s': relo #%d: relocation decision ambiguity: %s %u != %s %u\n",
prog_name, relo_idx,
cand_res.poison ? "failure" : "success", cand_res.new_val,
targ_res.poison ? "failure" : "success", targ_res.new_val);
return -EINVAL;
}
cands->cands[j++] = cands->cands[i];
}
/*
* For BPF_FIELD_EXISTS relo or when used BPF program has field
* existence checks or kernel version/config checks, it's expected
* that we might not find any candidates. In this case, if field
* wasn't found in any candidate, the list of candidates shouldn't
* change at all, we'll just handle relocating appropriately,
* depending on relo's kind.
*/
if (j > 0)
cands->len = j;
/*
* If no candidates were found, it might be both a programmer error,
* as well as expected case, depending whether instruction w/
* relocation is guarded in some way that makes it unreachable (dead
* code) if relocation can't be resolved. This is handled in
* bpf_core_patch_insn() uniformly by replacing that instruction with
* BPF helper call insn (using invalid helper ID). If that instruction
* is indeed unreachable, then it will be ignored and eliminated by
* verifier. If it was an error, then verifier will complain and point
* to a specific instruction number in its log.
*/
if (j == 0) {
pr_debug("prog '%s': relo #%d: no matching targets found\n",
prog_name, relo_idx);
/* calculate single target relo result explicitly */
err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, NULL, &targ_res);
if (err)
return err;
}
patch_insn:
/* bpf_core_patch_insn() should know how to handle missing targ_spec */
err = bpf_core_patch_insn(prog_name, insn, insn_idx, relo, relo_idx, &targ_res);
if (err) {
pr_warn("prog '%s': relo #%d: failed to patch insn #%zu: %d\n",
prog_name, relo_idx, relo->insn_off / BPF_INSN_SZ, err);
return -EINVAL;
}
return 0;
}
static int bpf_core_apply_relo(struct bpf_program *prog,
const struct bpf_core_relo *relo,
int relo_idx,
......
tools/lib/bpf/libbpf_internal.h
View file @ b0588390
......@@ -425,4 +425,14 @@ static inline void *libbpf_ptr(void *ret)
return ret;
}
static inline bool str_is_empty(const char *s)
{
return !s || !s[0];
}
static inline bool is_ldimm64_insn(struct bpf_insn *insn)
{
return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
}
#endif /* __LIBBPF_LIBBPF_INTERNAL_H */
tools/lib/bpf/relo_core.c 0 → 100644
View file @ b0588390
// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
/* Copyright (c) 2019 Facebook */
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <linux/err.h>
#include "libbpf.h"
#include "bpf.h"
#include "btf.h"
#include "str_error.h"
#include "libbpf_internal.h"
#define BPF_CORE_SPEC_MAX_LEN 64
/* represents BPF CO-RE field or array element accessor */
struct bpf_core_accessor {
__u32 type_id; /* struct/union type or array element type */
__u32 idx; /* field index or array index */
const char *name; /* field name or NULL for array accessor */
};
struct bpf_core_spec {
const struct btf *btf;
/* high-level spec: named fields and array indices only */
struct bpf_core_accessor spec[BPF_CORE_SPEC_MAX_LEN];
/* original unresolved (no skip_mods_or_typedefs) root type ID */
__u32 root_type_id;
/* CO-RE relocation kind */
enum bpf_core_relo_kind relo_kind;
/* high-level spec length */
int len;
/* raw, low-level spec: 1-to-1 with accessor spec string */
int raw_spec[BPF_CORE_SPEC_MAX_LEN];
/* raw spec length */
int raw_len;
/* field bit offset represented by spec */
__u32 bit_offset;
};
static bool is_flex_arr(const struct btf *btf,
const struct bpf_core_accessor *acc,
const struct btf_array *arr)
{
const struct btf_type *t;
/* not a flexible array, if not inside a struct or has non-zero size */
if (!acc->name || arr->nelems > 0)
return false;
/* has to be the last member of enclosing struct */
t = btf__type_by_id(btf, acc->type_id);
return acc->idx == btf_vlen(t) - 1;
}
static const char *core_relo_kind_str(enum bpf_core_relo_kind kind)
{
switch (kind) {
case BPF_FIELD_BYTE_OFFSET: return "byte_off";
case BPF_FIELD_BYTE_SIZE: return "byte_sz";
case BPF_FIELD_EXISTS: return "field_exists";
case BPF_FIELD_SIGNED: return "signed";
case BPF_FIELD_LSHIFT_U64: return "lshift_u64";
case BPF_FIELD_RSHIFT_U64: return "rshift_u64";
case BPF_TYPE_ID_LOCAL: return "local_type_id";
case BPF_TYPE_ID_TARGET: return "target_type_id";
case BPF_TYPE_EXISTS: return "type_exists";
case BPF_TYPE_SIZE: return "type_size";
case BPF_ENUMVAL_EXISTS: return "enumval_exists";
case BPF_ENUMVAL_VALUE: return "enumval_value";
default: return "unknown";
}
}
static bool core_relo_is_field_based(enum bpf_core_relo_kind kind)
{
switch (kind) {
case BPF_FIELD_BYTE_OFFSET:
case BPF_FIELD_BYTE_SIZE:
case BPF_FIELD_EXISTS:
case BPF_FIELD_SIGNED:
case BPF_FIELD_LSHIFT_U64:
case BPF_FIELD_RSHIFT_U64:
return true;
default:
return false;
}
}
static bool core_relo_is_type_based(enum bpf_core_relo_kind kind)
{
switch (kind) {
case BPF_TYPE_ID_LOCAL:
case BPF_TYPE_ID_TARGET:
case BPF_TYPE_EXISTS:
case BPF_TYPE_SIZE:
return true;
default:
return false;
}
}
static bool core_relo_is_enumval_based(enum bpf_core_relo_kind kind)
{
switch (kind) {
case BPF_ENUMVAL_EXISTS:
case BPF_ENUMVAL_VALUE:
return true;
default:
return false;
}
}
/*
* Turn bpf_core_relo into a low- and high-level spec representation,
* validating correctness along the way, as well as calculating resulting
* field bit offset, specified by accessor string. Low-level spec captures
* every single level of nestedness, including traversing anonymous
* struct/union members. High-level one only captures semantically meaningful
* "turning points": named fields and array indicies.
* E.g., for this case:
*
* struct sample {
* int __unimportant;
* struct {
* int __1;
* int __2;
* int a[7];
* };
* };
*
* struct sample *s = ...;
*
* int x = &s->a[3]; // access string = '0:1:2:3'
*
* Low-level spec has 1:1 mapping with each element of access string (it's
* just a parsed access string representation): [0, 1, 2, 3].
*
* High-level spec will capture only 3 points:
* - intial zero-index access by pointer (&s->... is the same as &s[0]...);
* - 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_ID_LOCAL/TYPE_ID_TARGET) don't capture any field information. Their
* spec and raw_spec are kept empty.
*
* Enum value-based relocations (ENUMVAL_EXISTS/ENUMVAL_VALUE) use access
* string to specify enumerator's value index that need to be relocated.
*/
static int bpf_core_parse_spec(const struct btf *btf,
__u32 type_id,
const char *spec_str,
enum bpf_core_relo_kind relo_kind,
struct bpf_core_spec *spec)
{
int access_idx, parsed_len, i;
struct bpf_core_accessor *acc;
const struct btf_type *t;
const char *name;
__u32 id;
__s64 sz;
if (str_is_empty(spec_str) || *spec_str == ':')
return -EINVAL;
memset(spec, 0, sizeof(*spec));
spec->btf = btf;
spec->root_type_id = type_id;
spec->relo_kind = relo_kind;
/* type-based relocations don't have a field access string */
if (core_relo_is_type_based(relo_kind)) {
if (strcmp(spec_str, "0"))
return -EINVAL;
return 0;
}
/* parse spec_str="0:1:2:3:4" into array raw_spec=[0, 1, 2, 3, 4] */
while (*spec_str) {
if (*spec_str == ':')
++spec_str;
if (sscanf(spec_str, "%d%n", &access_idx, &parsed_len) != 1)
return -EINVAL;
if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
return -E2BIG;
spec_str += parsed_len;
spec->raw_spec[spec->raw_len++] = access_idx;
}
if (spec->raw_len == 0)
return -EINVAL;
t = skip_mods_and_typedefs(btf, type_id, &id);
if (!t)
return -EINVAL;
access_idx = spec->raw_spec[0];
acc = &spec->spec[0];
acc->type_id = id;
acc->idx = access_idx;
spec->len++;
if (core_relo_is_enumval_based(relo_kind)) {
if (!btf_is_enum(t) || spec->raw_len > 1 || access_idx >= btf_vlen(t))
return -EINVAL;
/* record enumerator name in a first accessor */
acc->name = btf__name_by_offset(btf, btf_enum(t)[access_idx].name_off);
return 0;
}
if (!core_relo_is_field_based(relo_kind))
return -EINVAL;
sz = btf__resolve_size(btf, id);
if (sz < 0)
return sz;
spec->bit_offset = access_idx * sz * 8;
for (i = 1; i < spec->raw_len; i++) {
t = skip_mods_and_typedefs(btf, id, &id);
if (!t)
return -EINVAL;
access_idx = spec->raw_spec[i];
acc = &spec->spec[spec->len];
if (btf_is_composite(t)) {
const struct btf_member *m;
__u32 bit_offset;
if (access_idx >= btf_vlen(t))
return -EINVAL;
bit_offset = btf_member_bit_offset(t, access_idx);
spec->bit_offset += bit_offset;
m = btf_members(t) + access_idx;
if (m->name_off) {
name = btf__name_by_offset(btf, m->name_off);
if (str_is_empty(name))
return -EINVAL;
acc->type_id = id;
acc->idx = access_idx;
acc->name = name;
spec->len++;
}
id = m->type;
} else if (btf_is_array(t)) {
const struct btf_array *a = btf_array(t);
bool flex;
t = skip_mods_and_typedefs(btf, a->type, &id);
if (!t)
return -EINVAL;
flex = is_flex_arr(btf, acc - 1, a);
if (!flex && access_idx >= a->nelems)
return -EINVAL;
spec->spec[spec->len].type_id = id;
spec->spec[spec->len].idx = access_idx;
spec->len++;
sz = btf__resolve_size(btf, id);
if (sz < 0)
return sz;
spec->bit_offset += access_idx * sz * 8;
} else {
pr_warn("relo for [%u] %s (at idx %d) captures type [%d] of unexpected kind %s\n",
type_id, spec_str, i, id, btf_kind_str(t));
return -EINVAL;
}
}
return 0;
}
/* Check two types for compatibility for the purpose of field access
* relocation. const/volatile/restrict and typedefs are skipped to ensure we
* are relocating semantically compatible entities:
* - any two STRUCTs/UNIONs are compatible and can be mixed;
* - any two FWDs are compatible, if their names match (modulo flavor suffix);
* - any two PTRs are always compatible;
* - for ENUMs, names should be the same (ignoring flavor suffix) or at
* least one of enums should be anonymous;
* - for ENUMs, check sizes, names are ignored;
* - for INT, size and signedness are ignored;
* - any two FLOATs are always compatible;
* - for ARRAY, dimensionality is ignored, element types are checked for
* compatibility recursively;
* - everything else shouldn't be ever a target of relocation.
* These rules are not set in stone and probably will be adjusted as we get
* more experience with using BPF CO-RE relocations.
*/
static int bpf_core_fields_are_compat(const struct btf *local_btf,
__u32 local_id,
const struct btf *targ_btf,
__u32 targ_id)
{
const struct btf_type *local_type, *targ_type;
recur:
local_type = skip_mods_and_typedefs(local_btf, local_id, &local_id);
targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
if (!local_type || !targ_type)
return -EINVAL;
if (btf_is_composite(local_type) && btf_is_composite(targ_type))
return 1;
if (btf_kind(local_type) != btf_kind(targ_type))
return 0;
switch (btf_kind(local_type)) {
case BTF_KIND_PTR:
case BTF_KIND_FLOAT:
return 1;
case BTF_KIND_FWD:
case BTF_KIND_ENUM: {
const char *local_name, *targ_name;
size_t local_len, targ_len;
local_name = btf__name_by_offset(local_btf,
local_type->name_off);
targ_name = btf__name_by_offset(targ_btf, targ_type->name_off);
local_len = bpf_core_essential_name_len(local_name);
targ_len = bpf_core_essential_name_len(targ_name);
/* one of them is anonymous or both w/ same flavor-less names */
return local_len == 0 || targ_len == 0 ||
(local_len == targ_len &&
strncmp(local_name, targ_name, local_len) == 0);
}
case BTF_KIND_INT:
/* just reject deprecated bitfield-like integers; all other
* integers are by default compatible between each other
*/
return btf_int_offset(local_type) == 0 &&
btf_int_offset(targ_type) == 0;
case BTF_KIND_ARRAY:
local_id = btf_array(local_type)->type;
targ_id = btf_array(targ_type)->type;
goto recur;
default:
pr_warn("unexpected kind %d relocated, local [%d], target [%d]\n",
btf_kind(local_type), local_id, targ_id);
return 0;
}
}
/*
* Given single high-level named field accessor in local type, find
* corresponding high-level accessor for a target type. Along the way,
* maintain low-level spec for target as well. Also keep updating target
* bit offset.
*
* Searching is performed through recursive exhaustive enumeration of all
* fields of a struct/union. If there are any anonymous (embedded)
* structs/unions, they are recursively searched as well. If field with
* desired name is found, check compatibility between local and target types,
* before returning result.
*
* 1 is returned, if field is found.
* 0 is returned if no compatible field is found.
* <0 is returned on error.
*/
static int bpf_core_match_member(const struct btf *local_btf,
const struct bpf_core_accessor *local_acc,
const struct btf *targ_btf,
__u32 targ_id,
struct bpf_core_spec *spec,
__u32 *next_targ_id)
{
const struct btf_type *local_type, *targ_type;
const struct btf_member *local_member, *m;
const char *local_name, *targ_name;
__u32 local_id;
int i, n, found;
targ_type = skip_mods_and_typedefs(targ_btf, targ_id, &targ_id);
if (!targ_type)
return -EINVAL;
if (!btf_is_composite(targ_type))
return 0;
local_id = local_acc->type_id;
local_type = btf__type_by_id(local_btf, local_id);
local_member = btf_members(local_type) + local_acc->idx;
local_name = btf__name_by_offset(local_btf, local_member->name_off);
n = btf_vlen(targ_type);
m = btf_members(targ_type);
for (i = 0; i < n; i++, m++) {
__u32 bit_offset;
bit_offset = btf_member_bit_offset(targ_type, i);
/* too deep struct/union/array nesting */
if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
return -E2BIG;
/* speculate this member will be the good one */
spec->bit_offset += bit_offset;
spec->raw_spec[spec->raw_len++] = i;
targ_name = btf__name_by_offset(targ_btf, m->name_off);
if (str_is_empty(targ_name)) {
/* embedded struct/union, we need to go deeper */
found = bpf_core_match_member(local_btf, local_acc,
targ_btf, m->type,
spec, next_targ_id);
if (found) /* either found or error */
return found;
} else if (strcmp(local_name, targ_name) == 0) {
/* matching named field */
struct bpf_core_accessor *targ_acc;
targ_acc = &spec->spec[spec->len++];
targ_acc->type_id = targ_id;
targ_acc->idx = i;
targ_acc->name = targ_name;
*next_targ_id = m->type;
found = bpf_core_fields_are_compat(local_btf,
local_member->type,
targ_btf, m->type);
if (!found)
spec->len--; /* pop accessor */
return found;
}
/* member turned out not to be what we looked for */
spec->bit_offset -= bit_offset;
spec->raw_len--;
}
return 0;
}
/*
* Try to match local spec to a target type and, if successful, produce full
* target spec (high-level, low-level + bit offset).
*/
static int bpf_core_spec_match(struct bpf_core_spec *local_spec,
const struct btf *targ_btf, __u32 targ_id,
struct bpf_core_spec *targ_spec)
{
const struct btf_type *targ_type;
const struct bpf_core_accessor *local_acc;
struct bpf_core_accessor *targ_acc;
int i, sz, matched;
memset(targ_spec, 0, sizeof(*targ_spec));
targ_spec->btf = targ_btf;
targ_spec->root_type_id = targ_id;
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);
}
local_acc = &local_spec->spec[0];
targ_acc = &targ_spec->spec[0];
if (core_relo_is_enumval_based(local_spec->relo_kind)) {
size_t local_essent_len, targ_essent_len;
const struct btf_enum *e;
const char *targ_name;
/* has to resolve to an enum */
targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id, &targ_id);
if (!btf_is_enum(targ_type))
return 0;
local_essent_len = bpf_core_essential_name_len(local_acc->name);
for (i = 0, e = btf_enum(targ_type); i < btf_vlen(targ_type); i++, e++) {
targ_name = btf__name_by_offset(targ_spec->btf, e->name_off);
targ_essent_len = bpf_core_essential_name_len(targ_name);
if (targ_essent_len != local_essent_len)
continue;
if (strncmp(local_acc->name, targ_name, local_essent_len) == 0) {
targ_acc->type_id = targ_id;
targ_acc->idx = i;
targ_acc->name = targ_name;
targ_spec->len++;
targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx;
targ_spec->raw_len++;
return 1;
}
}
return 0;
}
if (!core_relo_is_field_based(local_spec->relo_kind))
return -EINVAL;
for (i = 0; i < local_spec->len; i++, local_acc++, targ_acc++) {
targ_type = skip_mods_and_typedefs(targ_spec->btf, targ_id,
&targ_id);
if (!targ_type)
return -EINVAL;
if (local_acc->name) {
matched = bpf_core_match_member(local_spec->btf,
local_acc,
targ_btf, targ_id,
targ_spec, &targ_id);
if (matched <= 0)
return matched;
} else {
/* for i=0, targ_id is already treated as array element
* type (because it's the original struct), for others
* we should find array element type first
*/
if (i > 0) {
const struct btf_array *a;
bool flex;
if (!btf_is_array(targ_type))
return 0;
a = btf_array(targ_type);
flex = is_flex_arr(targ_btf, targ_acc - 1, a);
if (!flex && local_acc->idx >= a->nelems)
return 0;
if (!skip_mods_and_typedefs(targ_btf, a->type,
&targ_id))
return -EINVAL;
}
/* too deep struct/union/array nesting */
if (targ_spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
return -E2BIG;
targ_acc->type_id = targ_id;
targ_acc->idx = local_acc->idx;
targ_acc->name = NULL;
targ_spec->len++;
targ_spec->raw_spec[targ_spec->raw_len] = targ_acc->idx;
targ_spec->raw_len++;
sz = btf__resolve_size(targ_btf, targ_id);
if (sz < 0)
return sz;
targ_spec->bit_offset += local_acc->idx * sz * 8;
}
}
return 1;
}
static int bpf_core_calc_field_relo(const char *prog_name,
const struct bpf_core_relo *relo,
const struct bpf_core_spec *spec,
__u32 *val, __u32 *field_sz, __u32 *type_id,
bool *validate)
{
const struct bpf_core_accessor *acc;
const struct btf_type *t;
__u32 byte_off, byte_sz, bit_off, bit_sz, field_type_id;
const struct btf_member *m;
const struct btf_type *mt;
bool bitfield;
__s64 sz;
*field_sz = 0;
if (relo->kind == BPF_FIELD_EXISTS) {
*val = spec ? 1 : 0;
return 0;
}
if (!spec)
return -EUCLEAN; /* request instruction poisoning */
acc = &spec->spec[spec->len - 1];
t = btf__type_by_id(spec->btf, acc->type_id);
/* a[n] accessor needs special handling */
if (!acc->name) {
if (relo->kind == BPF_FIELD_BYTE_OFFSET) {
*val = spec->bit_offset / 8;
/* remember field size for load/store mem size */
sz = btf__resolve_size(spec->btf, acc->type_id);
if (sz < 0)
return -EINVAL;
*field_sz = sz;
*type_id = acc->type_id;
} else if (relo->kind == BPF_FIELD_BYTE_SIZE) {
sz = btf__resolve_size(spec->btf, acc->type_id);
if (sz < 0)
return -EINVAL;
*val = sz;
} else {
pr_warn("prog '%s': relo %d at insn #%d can't be applied to array access\n",
prog_name, relo->kind, relo->insn_off / 8);
return -EINVAL;
}
if (validate)
*validate = true;
return 0;
}
m = btf_members(t) + acc->idx;
mt = skip_mods_and_typedefs(spec->btf, m->type, &field_type_id);
bit_off = spec->bit_offset;
bit_sz = btf_member_bitfield_size(t, acc->idx);
bitfield = bit_sz > 0;
if (bitfield) {
byte_sz = mt->size;
byte_off = bit_off / 8 / byte_sz * byte_sz;
/* figure out smallest int size necessary for bitfield load */
while (bit_off + bit_sz - byte_off * 8 > byte_sz * 8) {
if (byte_sz >= 8) {
/* bitfield can't be read with 64-bit read */
pr_warn("prog '%s': relo %d at insn #%d can't be satisfied for bitfield\n",
prog_name, relo->kind, relo->insn_off / 8);
return -E2BIG;
}
byte_sz *= 2;
byte_off = bit_off / 8 / byte_sz * byte_sz;
}
} else {
sz = btf__resolve_size(spec->btf, field_type_id);
if (sz < 0)
return -EINVAL;
byte_sz = sz;
byte_off = spec->bit_offset / 8;
bit_sz = byte_sz * 8;
}
/* for bitfields, all the relocatable aspects are ambiguous and we
* might disagree with compiler, so turn off validation of expected
* value, except for signedness
*/
if (validate)
*validate = !bitfield;
switch (relo->kind) {
case BPF_FIELD_BYTE_OFFSET:
*val = byte_off;
if (!bitfield) {
*field_sz = byte_sz;
*type_id = field_type_id;
}
break;
case BPF_FIELD_BYTE_SIZE:
*val = byte_sz;
break;
case BPF_FIELD_SIGNED:
/* enums will be assumed unsigned */
*val = btf_is_enum(mt) ||
(btf_int_encoding(mt) & BTF_INT_SIGNED);
if (validate)
*validate = true; /* signedness is never ambiguous */
break;
case BPF_FIELD_LSHIFT_U64:
#if __BYTE_ORDER == __LITTLE_ENDIAN
*val = 64 - (bit_off + bit_sz - byte_off * 8);
#else
*val = (8 - byte_sz) * 8 + (bit_off - byte_off * 8);
#endif
break;
case BPF_FIELD_RSHIFT_U64:
*val = 64 - bit_sz;
if (validate)
*validate = true; /* right shift is never ambiguous */
break;
case BPF_FIELD_EXISTS:
default:
return -EOPNOTSUPP;
}
return 0;
}
static int bpf_core_calc_type_relo(const struct bpf_core_relo *relo,
const struct bpf_core_spec *spec,
__u32 *val)
{
__s64 sz;
/* type-based relos return zero when target type is not found */
if (!spec) {
*val = 0;
return 0;
}
switch (relo->kind) {
case BPF_TYPE_ID_TARGET:
*val = spec->root_type_id;
break;
case BPF_TYPE_EXISTS:
*val = 1;
break;
case BPF_TYPE_SIZE:
sz = btf__resolve_size(spec->btf, spec->root_type_id);
if (sz < 0)
return -EINVAL;
*val = sz;
break;
case BPF_TYPE_ID_LOCAL:
/* BPF_TYPE_ID_LOCAL is handled specially and shouldn't get here */
default:
return -EOPNOTSUPP;
}
return 0;
}
static int bpf_core_calc_enumval_relo(const struct bpf_core_relo *relo,
const struct bpf_core_spec *spec,
__u32 *val)
{
const struct btf_type *t;
const struct btf_enum *e;
switch (relo->kind) {
case BPF_ENUMVAL_EXISTS:
*val = spec ? 1 : 0;
break;
case BPF_ENUMVAL_VALUE:
if (!spec)
return -EUCLEAN; /* request instruction poisoning */
t = btf__type_by_id(spec->btf, spec->spec[0].type_id);
e = btf_enum(t) + spec->spec[0].idx;
*val = e->val;
break;
default:
return -EOPNOTSUPP;
}
return 0;
}
struct bpf_core_relo_res
{
/* expected value in the instruction, unless validate == false */
__u32 orig_val;
/* new value that needs to be patched up to */
__u32 new_val;
/* relocation unsuccessful, poison instruction, but don't fail load */
bool poison;
/* some relocations can't be validated against orig_val */
bool validate;
/* for field byte offset relocations or the forms:
* *(T *)(rX + <off>) = rY
* rX = *(T *)(rY + <off>),
* we remember original and resolved field size to adjust direct
* memory loads of pointers and integers; this is necessary for 32-bit
* host kernel architectures, but also allows to automatically
* relocate fields that were resized from, e.g., u32 to u64, etc.
*/
bool fail_memsz_adjust;
__u32 orig_sz;
__u32 orig_type_id;
__u32 new_sz;
__u32 new_type_id;
};
/* Calculate original and target relocation values, given local and target
* specs and relocation kind. These values are calculated for each candidate.
* If there are multiple candidates, resulting values should all be consistent
* with each other. Otherwise, libbpf will refuse to proceed due to ambiguity.
* If instruction has to be poisoned, *poison will be set to true.
*/
static int bpf_core_calc_relo(const char *prog_name,
const struct bpf_core_relo *relo,
int relo_idx,
const struct bpf_core_spec *local_spec,
const struct bpf_core_spec *targ_spec,
struct bpf_core_relo_res *res)
{
int err = -EOPNOTSUPP;
res->orig_val = 0;
res->new_val = 0;
res->poison = false;
res->validate = true;
res->fail_memsz_adjust = false;
res->orig_sz = res->new_sz = 0;
res->orig_type_id = res->new_type_id = 0;
if (core_relo_is_field_based(relo->kind)) {
err = bpf_core_calc_field_relo(prog_name, relo, local_spec,
&res->orig_val, &res->orig_sz,
&res->orig_type_id, &res->validate);
err = err ?: bpf_core_calc_field_relo(prog_name, relo, targ_spec,
&res->new_val, &res->new_sz,
&res->new_type_id, NULL);
if (err)
goto done;
/* Validate if it's safe to adjust load/store memory size.
* Adjustments are performed only if original and new memory
* sizes differ.
*/
res->fail_memsz_adjust = false;
if (res->orig_sz != res->new_sz) {
const struct btf_type *orig_t, *new_t;
orig_t = btf__type_by_id(local_spec->btf, res->orig_type_id);
new_t = btf__type_by_id(targ_spec->btf, res->new_type_id);
/* There are two use cases in which it's safe to
* adjust load/store's mem size:
* - reading a 32-bit kernel pointer, while on BPF
* size pointers are always 64-bit; in this case
* it's safe to "downsize" instruction size due to
* pointer being treated as unsigned integer with
* zero-extended upper 32-bits;
* - reading unsigned integers, again due to
* zero-extension is preserving the value correctly.
*
* In all other cases it's incorrect to attempt to
* load/store field because read value will be
* incorrect, so we poison relocated instruction.
*/
if (btf_is_ptr(orig_t) && btf_is_ptr(new_t))
goto done;
if (btf_is_int(orig_t) && btf_is_int(new_t) &&
btf_int_encoding(orig_t) != BTF_INT_SIGNED &&
btf_int_encoding(new_t) != BTF_INT_SIGNED)
goto done;
/* mark as invalid mem size adjustment, but this will
* only be checked for LDX/STX/ST insns
*/
res->fail_memsz_adjust = true;
}
} else if (core_relo_is_type_based(relo->kind)) {
err = bpf_core_calc_type_relo(relo, local_spec, &res->orig_val);
err = err ?: bpf_core_calc_type_relo(relo, targ_spec, &res->new_val);
} else if (core_relo_is_enumval_based(relo->kind)) {
err = bpf_core_calc_enumval_relo(relo, local_spec, &res->orig_val);
err = err ?: bpf_core_calc_enumval_relo(relo, targ_spec, &res->new_val);
}
done:
if (err == -EUCLEAN) {
/* EUCLEAN is used to signal instruction poisoning request */
res->poison = true;
err = 0;
} else if (err == -EOPNOTSUPP) {
/* EOPNOTSUPP means unknown/unsupported relocation */
pr_warn("prog '%s': relo #%d: unrecognized CO-RE relocation %s (%d) at insn #%d\n",
prog_name, relo_idx, core_relo_kind_str(relo->kind),
relo->kind, relo->insn_off / 8);
}
return err;
}
/*
* Turn instruction for which CO_RE relocation failed into invalid one with
* distinct signature.
*/
static void bpf_core_poison_insn(const char *prog_name, int relo_idx,
int insn_idx, struct bpf_insn *insn)
{
pr_debug("prog '%s': relo #%d: substituting insn #%d w/ invalid insn\n",
prog_name, relo_idx, insn_idx);
insn->code = BPF_JMP | BPF_CALL;
insn->dst_reg = 0;
insn->src_reg = 0;
insn->off = 0;
/* if this instruction is reachable (not a dead code),
* verifier will complain with the following message:
* invalid func unknown#195896080
*/
insn->imm = 195896080; /* => 0xbad2310 => "bad relo" */
}
static int insn_bpf_size_to_bytes(struct bpf_insn *insn)
{
switch (BPF_SIZE(insn->code)) {
case BPF_DW: return 8;
case BPF_W: return 4;
case BPF_H: return 2;
case BPF_B: return 1;
default: return -1;
}
}
static int insn_bytes_to_bpf_size(__u32 sz)
{
switch (sz) {
case 8: return BPF_DW;
case 4: return BPF_W;
case 2: return BPF_H;
case 1: return BPF_B;
default: return -1;
}
}
/*
* Patch relocatable BPF instruction.
*
* Patched value is determined by relocation kind and target specification.
* For existence relocations target spec will be NULL if field/type is not found.
* Expected insn->imm value is determined using relocation kind and local
* spec, and is checked before patching instruction. If actual insn->imm value
* is wrong, bail out with error.
*
* Currently supported classes of BPF instruction are:
* 1. rX = <imm> (assignment with immediate operand);
* 2. rX += <imm> (arithmetic operations with immediate operand);
* 3. rX = <imm64> (load with 64-bit immediate value);
* 4. rX = *(T *)(rY + <off>), where T is one of {u8, u16, u32, u64};
* 5. *(T *)(rX + <off>) = rY, where T is one of {u8, u16, u32, u64};
* 6. *(T *)(rX + <off>) = <imm>, where T is one of {u8, u16, u32, u64}.
*/
static int bpf_core_patch_insn(const char *prog_name, struct bpf_insn *insn,
int insn_idx, const struct bpf_core_relo *relo,
int relo_idx, const struct bpf_core_relo_res *res)
{
__u32 orig_val, new_val;
__u8 class;
class = BPF_CLASS(insn->code);
if (res->poison) {
poison:
/* poison second part of ldimm64 to avoid confusing error from
* verifier about "unknown opcode 00"
*/
if (is_ldimm64_insn(insn))
bpf_core_poison_insn(prog_name, relo_idx, insn_idx + 1, insn + 1);
bpf_core_poison_insn(prog_name, relo_idx, insn_idx, insn);
return 0;
}
orig_val = res->orig_val;
new_val = res->new_val;
switch (class) {
case BPF_ALU:
case BPF_ALU64:
if (BPF_SRC(insn->code) != BPF_K)
return -EINVAL;
if (res->validate && insn->imm != orig_val) {
pr_warn("prog '%s': relo #%d: unexpected insn #%d (ALU/ALU64) value: got %u, exp %u -> %u\n",
prog_name, relo_idx,
insn_idx, insn->imm, orig_val, new_val);
return -EINVAL;
}
orig_val = insn->imm;
insn->imm = new_val;
pr_debug("prog '%s': relo #%d: patched insn #%d (ALU/ALU64) imm %u -> %u\n",
prog_name, relo_idx, insn_idx,
orig_val, new_val);
break;
case BPF_LDX:
case BPF_ST:
case BPF_STX:
if (res->validate && insn->off != orig_val) {
pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDX/ST/STX) value: got %u, exp %u -> %u\n",
prog_name, relo_idx, insn_idx, insn->off, orig_val, new_val);
return -EINVAL;
}
if (new_val > SHRT_MAX) {
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) value too big: %u\n",
prog_name, relo_idx, insn_idx, new_val);
return -ERANGE;
}
if (res->fail_memsz_adjust) {
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) accesses field incorrectly. "
"Make sure you are accessing pointers, unsigned integers, or fields of matching type and size.\n",
prog_name, relo_idx, insn_idx);
goto poison;
}
orig_val = insn->off;
insn->off = new_val;
pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) off %u -> %u\n",
prog_name, relo_idx, insn_idx, orig_val, new_val);
if (res->new_sz != res->orig_sz) {
int insn_bytes_sz, insn_bpf_sz;
insn_bytes_sz = insn_bpf_size_to_bytes(insn);
if (insn_bytes_sz != res->orig_sz) {
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) unexpected mem size: got %d, exp %u\n",
prog_name, relo_idx, insn_idx, insn_bytes_sz, res->orig_sz);
return -EINVAL;
}
insn_bpf_sz = insn_bytes_to_bpf_size(res->new_sz);
if (insn_bpf_sz < 0) {
pr_warn("prog '%s': relo #%d: insn #%d (LDX/ST/STX) invalid new mem size: %u\n",
prog_name, relo_idx, insn_idx, res->new_sz);
return -EINVAL;
}
insn->code = BPF_MODE(insn->code) | insn_bpf_sz | BPF_CLASS(insn->code);
pr_debug("prog '%s': relo #%d: patched insn #%d (LDX/ST/STX) mem_sz %u -> %u\n",
prog_name, relo_idx, insn_idx, res->orig_sz, res->new_sz);
}
break;
case BPF_LD: {
__u64 imm;
if (!is_ldimm64_insn(insn) ||
insn[0].src_reg != 0 || insn[0].off != 0 ||
insn[1].code != 0 || insn[1].dst_reg != 0 ||
insn[1].src_reg != 0 || insn[1].off != 0) {
pr_warn("prog '%s': relo #%d: insn #%d (LDIMM64) has unexpected form\n",
prog_name, relo_idx, insn_idx);
return -EINVAL;
}
imm = insn[0].imm + ((__u64)insn[1].imm << 32);
if (res->validate && imm != orig_val) {
pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDIMM64) value: got %llu, exp %u -> %u\n",
prog_name, relo_idx,
insn_idx, (unsigned long long)imm,
orig_val, new_val);
return -EINVAL;
}
insn[0].imm = new_val;
insn[1].imm = 0; /* currently only 32-bit values are supported */
pr_debug("prog '%s': relo #%d: patched insn #%d (LDIMM64) imm64 %llu -> %u\n",
prog_name, relo_idx, insn_idx,
(unsigned long long)imm, new_val);
break;
}
default:
pr_warn("prog '%s': relo #%d: trying to relocate unrecognized insn #%d, code:0x%x, src:0x%x, dst:0x%x, off:0x%x, imm:0x%x\n",
prog_name, relo_idx, insn_idx, insn->code,
insn->src_reg, insn->dst_reg, insn->off, insn->imm);
return -EINVAL;
}
return 0;
}
/* Output spec definition in the format:
* [<type-id>] (<type-name>) + <raw-spec> => <offset>@<spec>,
* where <spec> is a C-syntax view of recorded field access, e.g.: x.a[3].b
*/
static void bpf_core_dump_spec(int level, const struct bpf_core_spec *spec)
{
const struct btf_type *t;
const struct btf_enum *e;
const char *s;
__u32 type_id;
int i;
type_id = spec->root_type_id;
t = btf__type_by_id(spec->btf, type_id);
s = btf__name_by_offset(spec->btf, t->name_off);
libbpf_print(level, "[%u] %s %s", type_id, btf_kind_str(t), str_is_empty(s) ? "<anon>" : s);
if (core_relo_is_type_based(spec->relo_kind))
return;
if (core_relo_is_enumval_based(spec->relo_kind)) {
t = skip_mods_and_typedefs(spec->btf, type_id, NULL);
e = btf_enum(t) + spec->raw_spec[0];
s = btf__name_by_offset(spec->btf, e->name_off);
libbpf_print(level, "::%s = %u", s, e->val);
return;
}
if (core_relo_is_field_based(spec->relo_kind)) {
for (i = 0; i < spec->len; i++) {
if (spec->spec[i].name)
libbpf_print(level, ".%s", spec->spec[i].name);
else if (i > 0 || spec->spec[i].idx > 0)
libbpf_print(level, "[%u]", spec->spec[i].idx);
}
libbpf_print(level, " (");
for (i = 0; i < spec->raw_len; i++)
libbpf_print(level, "%s%d", i == 0 ? "" : ":", spec->raw_spec[i]);
if (spec->bit_offset % 8)
libbpf_print(level, " @ offset %u.%u)",
spec->bit_offset / 8, spec->bit_offset % 8);
else
libbpf_print(level, " @ offset %u)", spec->bit_offset / 8);
return;
}
}
/*
* CO-RE relocate single instruction.
*
* The outline and important points of the algorithm:
* 1. For given local type, find corresponding candidate target types.
* Candidate type is a type with the same "essential" name, ignoring
* everything after last triple underscore (___). E.g., `sample`,
* `sample___flavor_one`, `sample___flavor_another_one`, are all candidates
* for each other. Names with triple underscore are referred to as
* "flavors" and are useful, among other things, to allow to
* specify/support incompatible variations of the same kernel struct, which
* might differ between different kernel versions and/or build
* configurations.
*
* N.B. Struct "flavors" could be generated by bpftool's BTF-to-C
* converter, when deduplicated BTF of a kernel still contains more than
* one different types with the same name. In that case, ___2, ___3, etc
* are appended starting from second name conflict. But start flavors are
* also useful to be defined "locally", in BPF program, to extract same
* data from incompatible changes between different kernel
* versions/configurations. For instance, to handle field renames between
* kernel versions, one can use two flavors of the struct name with the
* same common name and use conditional relocations to extract that field,
* depending on target kernel version.
* 2. For each candidate type, try to match local specification to this
* candidate target type. Matching involves finding corresponding
* high-level spec accessors, meaning that all named fields should match,
* as well as all array accesses should be within the actual bounds. Also,
* types should be compatible (see bpf_core_fields_are_compat for details).
* 3. It is supported and expected that there might be multiple flavors
* matching the spec. As long as all the specs resolve to the same set of
* offsets across all candidates, there is no error. If there is any
* ambiguity, CO-RE relocation will fail. This is necessary to accomodate
* imprefection of BTF deduplication, which can cause slight duplication of
* the same BTF type, if some directly or indirectly referenced (by
* pointer) type gets resolved to different actual types in different
* object files. If such situation occurs, deduplicated BTF will end up
* with two (or more) structurally identical types, which differ only in
* types they refer to through pointer. This should be OK in most cases and
* is not an error.
* 4. Candidate types search is performed by linearly scanning through all
* types in target BTF. It is anticipated that this is overall more
* efficient memory-wise and not significantly worse (if not better)
* CPU-wise compared to prebuilding a map from all local type names to
* a list of candidate type names. It's also sped up by caching resolved
* list of matching candidates per each local "root" type ID, that has at
* least one bpf_core_relo associated with it. This list is shared
* between multiple relocations for the same type ID and is updated as some
* of the candidates are pruned due to structural incompatibility.
*/
int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
int insn_idx,
const struct bpf_core_relo *relo,
int relo_idx,
const struct btf *local_btf,
struct bpf_core_cand_list *cands)
{
struct bpf_core_spec local_spec, cand_spec, targ_spec = {};
struct bpf_core_relo_res cand_res, targ_res;
const struct btf_type *local_type;
const char *local_name;
__u32 local_id;
const char *spec_str;
int i, j, err;
local_id = relo->type_id;
local_type = btf__type_by_id(local_btf, local_id);
if (!local_type)
return -EINVAL;
local_name = btf__name_by_offset(local_btf, local_type->name_off);
if (!local_name)
return -EINVAL;
spec_str = btf__name_by_offset(local_btf, relo->access_str_off);
if (str_is_empty(spec_str))
return -EINVAL;
err = bpf_core_parse_spec(local_btf, local_id, spec_str, relo->kind, &local_spec);
if (err) {
pr_warn("prog '%s': relo #%d: parsing [%d] %s %s + %s failed: %d\n",
prog_name, relo_idx, local_id, btf_kind_str(local_type),
str_is_empty(local_name) ? "<anon>" : local_name,
spec_str, err);
return -EINVAL;
}
pr_debug("prog '%s': relo #%d: kind <%s> (%d), spec is ", prog_name,
relo_idx, core_relo_kind_str(relo->kind), relo->kind);
bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
libbpf_print(LIBBPF_DEBUG, "\n");
/* TYPE_ID_LOCAL relo is special and doesn't need candidate search */
if (relo->kind == BPF_TYPE_ID_LOCAL) {
targ_res.validate = true;
targ_res.poison = false;
targ_res.orig_val = local_spec.root_type_id;
targ_res.new_val = local_spec.root_type_id;
goto patch_insn;
}
/* libbpf doesn't support candidate search for anonymous types */
if (str_is_empty(spec_str)) {
pr_warn("prog '%s': relo #%d: <%s> (%d) relocation doesn't support anonymous types\n",
prog_name, relo_idx, core_relo_kind_str(relo->kind), relo->kind);
return -EOPNOTSUPP;
}
for (i = 0, j = 0; i < cands->len; i++) {
err = bpf_core_spec_match(&local_spec, cands->cands[i].btf,
cands->cands[i].id, &cand_spec);
if (err < 0) {
pr_warn("prog '%s': relo #%d: error matching candidate #%d ",
prog_name, relo_idx, i);
bpf_core_dump_spec(LIBBPF_WARN, &cand_spec);
libbpf_print(LIBBPF_WARN, ": %d\n", err);
return err;
}
pr_debug("prog '%s': relo #%d: %s candidate #%d ", prog_name,
relo_idx, err == 0 ? "non-matching" : "matching", i);
bpf_core_dump_spec(LIBBPF_DEBUG, &cand_spec);
libbpf_print(LIBBPF_DEBUG, "\n");
if (err == 0)
continue;
err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, &cand_spec, &cand_res);
if (err)
return err;
if (j == 0) {
targ_res = cand_res;
targ_spec = cand_spec;
} else if (cand_spec.bit_offset != targ_spec.bit_offset) {
/* if there are many field relo candidates, they
* should all resolve to the same bit offset
*/
pr_warn("prog '%s': relo #%d: field offset ambiguity: %u != %u\n",
prog_name, relo_idx, cand_spec.bit_offset,
targ_spec.bit_offset);
return -EINVAL;
} else if (cand_res.poison != targ_res.poison || cand_res.new_val != targ_res.new_val) {
/* all candidates should result in the same relocation
* decision and value, otherwise it's dangerous to
* proceed due to ambiguity
*/
pr_warn("prog '%s': relo #%d: relocation decision ambiguity: %s %u != %s %u\n",
prog_name, relo_idx,
cand_res.poison ? "failure" : "success", cand_res.new_val,
targ_res.poison ? "failure" : "success", targ_res.new_val);
return -EINVAL;
}
cands->cands[j++] = cands->cands[i];
}
/*
* For BPF_FIELD_EXISTS relo or when used BPF program has field
* existence checks or kernel version/config checks, it's expected
* that we might not find any candidates. In this case, if field
* wasn't found in any candidate, the list of candidates shouldn't
* change at all, we'll just handle relocating appropriately,
* depending on relo's kind.
*/
if (j > 0)
cands->len = j;
/*
* If no candidates were found, it might be both a programmer error,
* as well as expected case, depending whether instruction w/
* relocation is guarded in some way that makes it unreachable (dead
* code) if relocation can't be resolved. This is handled in
* bpf_core_patch_insn() uniformly by replacing that instruction with
* BPF helper call insn (using invalid helper ID). If that instruction
* is indeed unreachable, then it will be ignored and eliminated by
* verifier. If it was an error, then verifier will complain and point
* to a specific instruction number in its log.
*/
if (j == 0) {
pr_debug("prog '%s': relo #%d: no matching targets found\n",
prog_name, relo_idx);
/* calculate single target relo result explicitly */
err = bpf_core_calc_relo(prog_name, relo, relo_idx, &local_spec, NULL, &targ_res);
if (err)
return err;
}
patch_insn:
/* bpf_core_patch_insn() should know how to handle missing targ_spec */
err = bpf_core_patch_insn(prog_name, insn, insn_idx, relo, relo_idx, &targ_res);
if (err) {
pr_warn("prog '%s': relo #%d: failed to patch insn #%u: %d\n",
prog_name, relo_idx, relo->insn_off / 8, err);
return -EINVAL;
}
return 0;
}
tools/lib/bpf/relo_core.h
View file @ b0588390
......@@ -75,8 +75,7 @@ struct bpf_core_relo {
enum bpf_core_relo_kind kind;
};
struct bpf_core_cand
{
struct bpf_core_cand {
const struct btf *btf;
const struct btf_type *t;
const char *name;
......@@ -89,4 +88,13 @@ struct bpf_core_cand_list {
int len;
};
int bpf_core_apply_relo_insn(const char *prog_name,
struct bpf_insn *insn, int insn_idx,
const struct bpf_core_relo *relo, int relo_idx,
const struct btf *local_btf,
struct bpf_core_cand_list *cands);
int bpf_core_types_are_compat(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);
#endif
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