/
relo_core.c
1687 lines (1482 loc) · 50.5 KB
/
relo_core.c
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// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
/* Copyright (c) 2019 Facebook */
#ifdef __KERNEL__
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/string.h>
#include <linux/bpf_verifier.h>
#include "relo_core.h"
static const char *btf_kind_str(const struct btf_type *t)
{
return btf_type_str(t);
}
static bool is_ldimm64_insn(struct bpf_insn *insn)
{
return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
}
static const struct btf_type *
skip_mods_and_typedefs(const struct btf *btf, u32 id, u32 *res_id)
{
return btf_type_skip_modifiers(btf, id, res_id);
}
static const char *btf__name_by_offset(const struct btf *btf, u32 offset)
{
return btf_name_by_offset(btf, offset);
}
static s64 btf__resolve_size(const struct btf *btf, u32 type_id)
{
const struct btf_type *t;
int size;
t = btf_type_by_id(btf, type_id);
t = btf_resolve_size(btf, t, &size);
if (IS_ERR(t))
return PTR_ERR(t);
return size;
}
enum libbpf_print_level {
LIBBPF_WARN,
LIBBPF_INFO,
LIBBPF_DEBUG,
};
#undef pr_warn
#undef pr_info
#undef pr_debug
#define pr_warn(fmt, log, ...) bpf_log((void *)log, fmt, "", ##__VA_ARGS__)
#define pr_info(fmt, log, ...) bpf_log((void *)log, fmt, "", ##__VA_ARGS__)
#define pr_debug(fmt, log, ...) bpf_log((void *)log, fmt, "", ##__VA_ARGS__)
#define libbpf_print(level, fmt, ...) bpf_log((void *)prog_name, fmt, ##__VA_ARGS__)
#else
#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"
#endif
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_CORE_FIELD_BYTE_OFFSET: return "byte_off";
case BPF_CORE_FIELD_BYTE_SIZE: return "byte_sz";
case BPF_CORE_FIELD_EXISTS: return "field_exists";
case BPF_CORE_FIELD_SIGNED: return "signed";
case BPF_CORE_FIELD_LSHIFT_U64: return "lshift_u64";
case BPF_CORE_FIELD_RSHIFT_U64: return "rshift_u64";
case BPF_CORE_TYPE_ID_LOCAL: return "local_type_id";
case BPF_CORE_TYPE_ID_TARGET: return "target_type_id";
case BPF_CORE_TYPE_EXISTS: return "type_exists";
case BPF_CORE_TYPE_MATCHES: return "type_matches";
case BPF_CORE_TYPE_SIZE: return "type_size";
case BPF_CORE_ENUMVAL_EXISTS: return "enumval_exists";
case BPF_CORE_ENUMVAL_VALUE: return "enumval_value";
default: return "unknown";
}
}
static bool core_relo_is_field_based(enum bpf_core_relo_kind kind)
{
switch (kind) {
case BPF_CORE_FIELD_BYTE_OFFSET:
case BPF_CORE_FIELD_BYTE_SIZE:
case BPF_CORE_FIELD_EXISTS:
case BPF_CORE_FIELD_SIGNED:
case BPF_CORE_FIELD_LSHIFT_U64:
case BPF_CORE_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_CORE_TYPE_ID_LOCAL:
case BPF_CORE_TYPE_ID_TARGET:
case BPF_CORE_TYPE_EXISTS:
case BPF_CORE_TYPE_MATCHES:
case BPF_CORE_TYPE_SIZE:
return true;
default:
return false;
}
}
static bool core_relo_is_enumval_based(enum bpf_core_relo_kind kind)
{
switch (kind) {
case BPF_CORE_ENUMVAL_EXISTS:
case BPF_CORE_ENUMVAL_VALUE:
return true;
default:
return false;
}
}
int __bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
const struct btf *targ_btf, __u32 targ_id, int level)
{
const struct btf_type *local_type, *targ_type;
int depth = 32; /* max recursion depth */
/* caller made sure that names match (ignoring flavor suffix) */
local_type = btf_type_by_id(local_btf, local_id);
targ_type = btf_type_by_id(targ_btf, targ_id);
if (!btf_kind_core_compat(local_type, targ_type))
return 0;
recur:
depth--;
if (depth < 0)
return -EINVAL;
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_kind_core_compat(local_type, targ_type))
return 0;
switch (btf_kind(local_type)) {
case BTF_KIND_UNKN:
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
case BTF_KIND_ENUM:
case BTF_KIND_FWD:
case BTF_KIND_ENUM64:
return 1;
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_PTR:
local_id = local_type->type;
targ_id = targ_type->type;
goto recur;
case BTF_KIND_ARRAY:
local_id = btf_array(local_type)->type;
targ_id = btf_array(targ_type)->type;
goto recur;
case BTF_KIND_FUNC_PROTO: {
struct btf_param *local_p = btf_params(local_type);
struct btf_param *targ_p = btf_params(targ_type);
__u16 local_vlen = btf_vlen(local_type);
__u16 targ_vlen = btf_vlen(targ_type);
int i, err;
if (local_vlen != targ_vlen)
return 0;
for (i = 0; i < local_vlen; i++, local_p++, targ_p++) {
if (level <= 0)
return -EINVAL;
skip_mods_and_typedefs(local_btf, local_p->type, &local_id);
skip_mods_and_typedefs(targ_btf, targ_p->type, &targ_id);
err = __bpf_core_types_are_compat(local_btf, local_id, targ_btf, targ_id,
level - 1);
if (err <= 0)
return err;
}
/* tail recurse for return type check */
skip_mods_and_typedefs(local_btf, local_type->type, &local_id);
skip_mods_and_typedefs(targ_btf, targ_type->type, &targ_id);
goto recur;
}
default:
pr_warn("unexpected kind %s relocated, local [%d], target [%d]\n",
btf_kind_str(local_type), local_id, targ_id);
return 0;
}
}
/*
* 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:
* - initial 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_MATCHES/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.
*/
int bpf_core_parse_spec(const char *prog_name, const struct btf *btf,
const struct bpf_core_relo *relo,
struct bpf_core_spec *spec)
{
int access_idx, parsed_len, i;
struct bpf_core_accessor *acc;
const struct btf_type *t;
const char *name, *spec_str;
__u32 id, name_off;
__s64 sz;
spec_str = btf__name_by_offset(btf, relo->access_str_off);
if (str_is_empty(spec_str) || *spec_str == ':')
return -EINVAL;
memset(spec, 0, sizeof(*spec));
spec->btf = btf;
spec->root_type_id = relo->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, relo->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_any_enum(t) || spec->raw_len > 1 || access_idx >= btf_vlen(t))
return -EINVAL;
/* record enumerator name in a first accessor */
name_off = btf_is_enum(t) ? btf_enum(t)[access_idx].name_off
: btf_enum64(t)[access_idx].name_off;
acc->name = btf__name_by_offset(btf, 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("prog '%s': relo for [%u] %s (at idx %d) captures type [%d] of unexpected kind %s\n",
prog_name, relo->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_core_compat(local_type, 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_ENUM64:
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:
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;
__u32 name_off;
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)) {
if (local_spec->relo_kind == BPF_CORE_TYPE_MATCHES)
return bpf_core_types_match(local_spec->btf,
local_spec->root_type_id,
targ_btf, targ_id);
else
return bpf_core_types_are_compat(local_spec->btf,
local_spec->root_type_id,
targ_btf, targ_id);
}
local_acc = &local_spec->spec[0];
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 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_any_enum(targ_type))
return 0;
local_essent_len = bpf_core_essential_name_len(local_acc->name);
for (i = 0; i < btf_vlen(targ_type); i++) {
if (btf_is_enum(targ_type))
name_off = btf_enum(targ_type)[i].name_off;
else
name_off = btf_enum64(targ_type)[i].name_off;
targ_name = btf__name_by_offset(targ_spec->btf, 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,
__u64 *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_CORE_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_CORE_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_CORE_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_CORE_FIELD_BYTE_OFFSET:
*val = byte_off;
if (!bitfield) {
*field_sz = byte_sz;
*type_id = field_type_id;
}
break;
case BPF_CORE_FIELD_BYTE_SIZE:
*val = byte_sz;
break;
case BPF_CORE_FIELD_SIGNED:
*val = (btf_is_any_enum(mt) && BTF_INFO_KFLAG(mt->info)) ||
(btf_is_int(mt) && (btf_int_encoding(mt) & BTF_INT_SIGNED));
if (validate)
*validate = true; /* signedness is never ambiguous */
break;
case BPF_CORE_FIELD_LSHIFT_U64:
#if __BYTE_ORDER__ == __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_CORE_FIELD_RSHIFT_U64:
*val = 64 - bit_sz;
if (validate)
*validate = true; /* right shift is never ambiguous */
break;
case BPF_CORE_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,
__u64 *val, bool *validate)
{
__s64 sz;
/* by default, always check expected value in bpf_insn */
if (validate)
*validate = true;
/* type-based relos return zero when target type is not found */
if (!spec) {
*val = 0;
return 0;
}
switch (relo->kind) {
case BPF_CORE_TYPE_ID_TARGET:
*val = spec->root_type_id;
/* type ID, embedded in bpf_insn, might change during linking,
* so enforcing it is pointless
*/
if (validate)
*validate = false;
break;
case BPF_CORE_TYPE_EXISTS:
case BPF_CORE_TYPE_MATCHES:
*val = 1;
break;
case BPF_CORE_TYPE_SIZE:
sz = btf__resolve_size(spec->btf, spec->root_type_id);
if (sz < 0)
return -EINVAL;
*val = sz;
break;
case BPF_CORE_TYPE_ID_LOCAL:
/* BPF_CORE_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,
__u64 *val)
{
const struct btf_type *t;
switch (relo->kind) {
case BPF_CORE_ENUMVAL_EXISTS:
*val = spec ? 1 : 0;
break;
case BPF_CORE_ENUMVAL_VALUE:
if (!spec)
return -EUCLEAN; /* request instruction poisoning */
t = btf_type_by_id(spec->btf, spec->spec[0].type_id);
if (btf_is_enum(t))
*val = btf_enum(t)[spec->spec[0].idx].val;
else
*val = btf_enum64_value(btf_enum64(t) + spec->spec[0].idx);
break;
default:
return -EOPNOTSUPP;
}
return 0;
}
/* 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, &res->validate);
err = err ?: bpf_core_calc_type_relo(relo, targ_spec, &res->new_val, NULL);
} 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;