// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2019 Facebook */
#include <linux/bpf.h>
#include <linux/bpf_verifier.h>
#include <linux/btf.h>
#include <linux/filter.h>
#include <linux/slab.h>
#include <linux/numa.h>
#include <linux/seq_file.h>
#include <linux/refcount.h>
#include <linux/mutex.h>
#include <linux/btf_ids.h>
#include <linux/rcupdate_wait.h>
#include <linux/poll.h>
struct bpf_struct_ops_value {
struct bpf_struct_ops_common_value common;
char data[] ____cacheline_aligned_in_smp;
};
#define MAX_TRAMP_IMAGE_PAGES 8
struct bpf_struct_ops_map {
struct bpf_map map;
struct rcu_head rcu;
const struct bpf_struct_ops_desc *st_ops_desc;
/* protect map_update */
struct mutex lock;
/* link has all the bpf_links that is populated
* to the func ptr of the kernel's struct
* (in kvalue.data).
*/
struct bpf_link **links;
u32 links_cnt;
u32 image_pages_cnt;
/* image_pages is an array of pages that has all the trampolines
* that stores the func args before calling the bpf_prog.
*/
void *image_pages[MAX_TRAMP_IMAGE_PAGES];
/* The owner moduler's btf. */
struct btf *btf;
/* uvalue->data stores the kernel struct
* (e.g. tcp_congestion_ops) that is more useful
* to userspace than the kvalue. For example,
* the bpf_prog's id is stored instead of the kernel
* address of a func ptr.
*/
struct bpf_struct_ops_value *uvalue;
/* kvalue.data stores the actual kernel's struct
* (e.g. tcp_congestion_ops) that will be
* registered to the kernel subsystem.
*/
struct bpf_struct_ops_value kvalue;
};
struct bpf_struct_ops_link {
struct bpf_link link;
struct bpf_map __rcu *map;
wait_queue_head_t wait_hup;
};
static DEFINE_MUTEX(update_mutex);
#define VALUE_PREFIX "bpf_struct_ops_"
#define VALUE_PREFIX_LEN (sizeof(VALUE_PREFIX) - 1)
const struct bpf_verifier_ops bpf_struct_ops_verifier_ops = {
};
const struct bpf_prog_ops bpf_struct_ops_prog_ops = {
#ifdef CONFIG_NET
.test_run = bpf_struct_ops_test_run,
#endif
};
BTF_ID_LIST(st_ops_ids)
BTF_ID(struct, module)
BTF_ID(struct, bpf_struct_ops_common_value)
enum {
IDX_MODULE_ID,
IDX_ST_OPS_COMMON_VALUE_ID,
};
extern struct btf *btf_vmlinux;
static bool is_valid_value_type(struct btf *btf, s32 value_id,
const struct btf_type *type,
const char *value_name)
{
const struct btf_type *common_value_type;
const struct btf_member *member;
const struct btf_type *vt, *mt;
vt = btf_type_by_id(btf, value_id);
if (btf_vlen(vt) != 2) {
pr_warn("The number of %s's members should be 2, but we get %d\n",
value_name, btf_vlen(vt));
return false;
}
member = btf_type_member(vt);
mt = btf_type_by_id(btf, member->type);
common_value_type = btf_type_by_id(btf_vmlinux,
st_ops_ids[IDX_ST_OPS_COMMON_VALUE_ID]);
if (mt != common_value_type) {
pr_warn("The first member of %s should be bpf_struct_ops_common_value\n",
value_name);
return false;
}
member++;
mt = btf_type_by_id(btf, member->type);
if (mt != type) {
pr_warn("The second member of %s should be %s\n",
value_name, btf_name_by_offset(btf, type->name_off));
return false;
}
return true;
}
static void *bpf_struct_ops_image_alloc(void)
{
void *image;
int err;
err = bpf_jit_charge_modmem(PAGE_SIZE);
if (err)
return ERR_PTR(err);
image = arch_alloc_bpf_trampoline(PAGE_SIZE);
if (!image) {
bpf_jit_uncharge_modmem(PAGE_SIZE);
return ERR_PTR(-ENOMEM);
}
return image;
}
void bpf_struct_ops_image_free(void *image)
{
if (image) {
arch_free_bpf_trampoline(image, PAGE_SIZE);
bpf_jit_uncharge_modmem(PAGE_SIZE);
}
}
#define MAYBE_NULL_SUFFIX "__nullable"
#define MAX_STUB_NAME 128
/* Return the type info of a stub function, if it exists.
*
* The name of a stub function is made up of the name of the struct_ops and
* the name of the function pointer member, separated by "__". For example,
* if the struct_ops type is named "foo_ops" and the function pointer
* member is named "bar", the stub function name would be "foo_ops__bar".
*/
static const struct btf_type *
find_stub_func_proto(const struct btf *btf, const char *st_op_name,
const char *member_name)
{
char stub_func_name[MAX_STUB_NAME];
const struct btf_type *func_type;
s32 btf_id;
int cp;
cp = snprintf(stub_func_name, MAX_STUB_NAME, "%s__%s",
st_op_name, member_name);
if (cp >= MAX_STUB_NAME) {
pr_warn("Stub function name too long\n");
return NULL;
}
btf_id = btf_find_by_name_kind(btf, stub_func_name, BTF_KIND_FUNC);
if (btf_id < 0)
return NULL;
func_type = btf_type_by_id(btf, btf_id);
if (!func_type)
return NULL;
return btf_type_by_id(btf, func_type->type); /* FUNC_PROTO */
}
/* Prepare argument info for every nullable argument of a member of a
* struct_ops type.
*
* Initialize a struct bpf_struct_ops_arg_info according to type info of
* the arguments of a stub function. (Check kCFI for more information about
* stub functions.)
*
* Each member in the struct_ops type has a struct bpf_struct_ops_arg_info
* to provide an array of struct bpf_ctx_arg_aux, which in turn provides
* the information that used by the verifier to check the arguments of the
* BPF struct_ops program assigned to the member. Here, we only care about
* the arguments that are marked as __nullable.
*
* The array of struct bpf_ctx_arg_aux is eventually assigned to
* prog->aux->ctx_arg_info of BPF struct_ops programs and passed to the
* verifier. (See check_struct_ops_btf_id())
*
* arg_info->info will be the list of struct bpf_ctx_arg_aux if success. If
* fails, it will be kept untouched.
*/
static int prepare_arg_info(struct btf *btf,
const char *st_ops_name,
const char *member_name,
const struct btf_type *func_proto,
struct bpf_struct_ops_arg_info *arg_info)
{
const struct btf_type *stub_func_proto, *pointed_type;
const struct btf_param *stub_args, *args;
struct bpf_ctx_arg_aux *info, *info_buf;
u32 nargs, arg_no, info_cnt = 0;
u32 arg_btf_id;
int offset;
stub_func_proto = find_stub_func_proto(btf, st_ops_name, member_name);
if (!stub_func_proto)
return 0;
/* Check if the number of arguments of the stub function is the same
* as the number of arguments of the function pointer.
*/
nargs = btf_type_vlen(func_proto);
if (nargs != btf_type_vlen(stub_func_proto)) {
pr_warn("the number of arguments of the stub function %s__%s does not match the number of arguments of the member %s of struct %s\n",
st_ops_name, member_name, member_name, st_ops_name);
return -EINVAL;
}
if (!nargs)
return 0;
args = btf_params(func_proto);
stub_args = btf_params(stub_func_proto);
info_buf = kcalloc(nargs, sizeof(*info_buf), GFP_KERNEL);
if (!info_buf)
return -ENOMEM;
/* Prepare info for every nullable argument */
info = info_buf;
for (arg_no = 0; arg_no < nargs; arg_no++) {
/* Skip arguments that is not suffixed with
* "__nullable".
*/
if (!btf_param_match_suffix(btf, &stub_args[arg_no],
MAYBE_NULL_SUFFIX))
continue;
/* Should be a pointer to struct */
pointed_type = btf_type_resolve_ptr(btf,
args[arg_no].type,
&arg_btf_id);
if (!pointed_type ||
!btf_type_is_struct(pointed_type)) {
pr_warn("stub function %s__%s has %s tagging to an unsupported type\n",
st_ops_name, member_name, MAYBE_NULL_SUFFIX);
goto err_out;
}
offset = btf_ctx_arg_offset(btf, func_proto, arg_no);
if (offset < 0) {
pr_warn("stub function %s__%s has an invalid trampoline ctx offset for arg#%u\n",
st_ops_name, member_name, arg_no);
goto err_out;
}
if (args[arg_no].type != stub_args[arg_no].type) {
pr_warn("arg#%u type in stub function %s__%s does not match with its original func_proto\n",
arg_no, st_ops_name, member_name);
goto err_out;
}
/* Fill the information of the new argument */
info->reg_type =
PTR_TRUSTED | PTR_TO_BTF_ID | PTR_MAYBE_NULL;
info->btf_id = arg_btf_id;
info->btf = btf;
info->offset = offset;
info++;
info_cnt++;
}
if (info_cnt) {
arg_info->info = info_buf;
arg_info->cnt = info_cnt;
} else {
kfree(info_buf);
}
return 0;
err_out:
kfree(info_buf);
return -EINVAL;
}
/* Clean up the arg_info in a struct bpf_struct_ops_desc. */
void bpf_struct_ops_desc_release(struct bpf_struct_ops_desc *st_ops_desc)
{
struct bpf_struct_ops_arg_info *arg_info;
int i;
arg_info = st_ops_desc->arg_info;
for (i = 0; i < btf_type_vlen(st_ops_desc->type); i++)
kfree(arg_info[i].info);
kfree(arg_info);
}
int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
struct btf *btf,
struct bpf_verifier_log *log)
{
struct bpf_struct_ops *st_ops = st_ops_desc->st_ops;
struct bpf_struct_ops_arg_info *arg_info;
const struct btf_member *member;
const struct btf_type *t;
s32 type_id, value_id;
char value_name[128];
const char *mname;
int i, err;
if (strlen(st_ops->name) + VALUE_PREFIX_LEN >=
sizeof(value_name)) {
pr_warn("struct_ops name %s is too long\n",
st_ops->name);
return -EINVAL;
}
sprintf(value_name, "%s%s", VALUE_PREFIX, st_ops->name);
if (!st_ops->cfi_stubs) {
pr_warn("struct_ops for %s has no cfi_stubs\n", st_ops->name);
return -EINVAL;
}
type_id = btf_find_by_name_kind(btf, st_ops->name,
BTF_KIND_STRUCT);
if (type_id < 0) {
pr_warn("Cannot find struct %s in %s\n",
st_ops->name, btf_get_name(btf));
return -EINVAL;
}
t = btf_type_by_id(btf, type_id);
if (btf_type_vlen(t) > BPF_STRUCT_OPS_MAX_NR_MEMBERS) {
pr_warn("Cannot support #%u members in struct %s\n",
btf_type_vlen(t), st_ops->name);
return -EINVAL;
}
value_id = btf_find_by_name_kind(btf, value_name,
BTF_KIND_STRUCT);
if (value_id < 0) {
pr_warn("Cannot find struct %s in %s\n",
value_name, btf_get_name(btf));
return -EINVAL;
}
if (!is_valid_value_type(btf, value_id, t, value_name))
return -EINVAL;
arg_info = kcalloc(btf_type_vlen(t), sizeof(*arg_info),
GFP_KERNEL);
if (!arg_info)
return -ENOMEM;
st_ops_desc->arg_info = arg_info;
st_ops_desc->type = t;
st_ops_desc->type_id = type_id;
st_ops_desc->value_id = value_id;
st_ops_desc->value_type = btf_type_by_id(btf, value_id);
for_each_member(i, t, member) {
const struct btf_type *func_proto;
mname = btf_name_by_offset(btf, member->name_off);
if (!*mname) {
pr_warn("anon member in struct %s is not supported\n",
st_ops->name);
err = -EOPNOTSUPP;
goto errout;
}
if (__btf_member_bitfield_size(t, member)) {
pr_warn("bit field member %s in struct %s is not supported\n",
mname, st_ops->name);
err = -EOPNOTSUPP;
goto errout;
}
func_proto = btf_type_resolve_func_ptr(btf,
member->type,
NULL);
if (!func_proto)
continue;
if (btf_distill_func_proto(log, btf,
func_proto, mname,
&st_ops->func_models[i])) {
pr_warn("Error in parsing func ptr %s in struct %s\n",
mname, st_ops->name);
err = -EINVAL;
goto errout;
}
err = prepare_arg_info(btf, st_ops->name, mname,
func_proto,
arg_info + i);
if (err)
goto errout;
}
if (st_ops->init(btf)) {
pr_warn("Error in init bpf_struct_ops %s\n",
st_ops->name);
err = -EINVAL;
goto errout;
}
return 0;
errout:
bpf_struct_ops_desc_release(st_ops_desc);
return err;
}
static int bpf_struct_ops_map_get_next_key(struct bpf_map *map, void *key,
void *next_key)
{
if (key && *(u32 *)key == 0)
return -ENOENT;
*(u32 *)next_key = 0;
return 0;
}
int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
void *value)
{
struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
struct bpf_struct_ops_value *uvalue, *kvalue;
enum bpf_struct_ops_state state;
s64 refcnt;
if (unlikely(*(u32 *)key != 0))
return -ENOENT;
kvalue = &st_map->kvalue;
/* Pair with smp_store_release() during map_update */
state = smp_load_acquire(&kvalue->common.state);
if (state == BPF_STRUCT_OPS_STATE_INIT) {
memset(value, 0, map->value_size);
return 0;
}
/* No lock is needed. state and refcnt do not need
* to be updated together under atomic context.
*/
uvalue = value;
memcpy(uvalue, st_map->uvalue, map->value_size);
uvalue->common.state = state;
/* This value offers the user space a general estimate of how
* many sockets are still utilizing this struct_ops for TCP
* congestion control. The number might not be exact, but it
* should sufficiently meet our present goals.
*/
refcnt = atomic64_read(&map->refcnt) - atomic64_read(&map->usercnt);
refcount_set(&uvalue->common.refcnt, max_t(s64, refcnt, 0));
return 0;
}
static void *bpf_struct_ops_map_lookup_elem(struct bpf_map *map, void *key)
{
return ERR_PTR(-EINVAL);
}
static void bpf_struct_ops_map_put_progs(struct bpf_struct_ops_map *st_map)
{
u32 i;
for (i = 0; i < st_map->links_cnt; i++) {
if (st_map->links[i]) {
bpf_link_put(st_map->links[i]);
st_map->links[i] = NULL;
}
}
}
static void bpf_struct_ops_map_free_image(struct bpf_struct_ops_map *st_map)
{
int i;
for (i = 0; i < st_map->image_pages_cnt; i++)
bpf_struct_ops_image_free(st_map->image_pages[i]);
st_map->image_pages_cnt = 0;
}
static int check_zero_holes(const struct btf *btf, const struct btf_type *t, void *data)
{
const struct btf_member *member;
u32 i, moff, msize, prev_mend = 0;
const struct btf_type *mtype;
for_each_member(i, t, member) {
moff = __btf_member_bit_offset(t, member) / 8;
if (moff > prev_mend &&
memchr_inv(data + prev_mend, 0, moff - prev_mend))
return -EINVAL;
mtype = btf_type_by_id(btf, member->type);
mtype = btf_resolve_size(btf, mtype, &msize);
if (IS_ERR(mtype))
return PTR_ERR(mtype);
prev_mend = moff + msize;
}
if (t->size > prev_mend &&
memchr_inv(data + prev_mend, 0, t->size - prev_mend))
return -EINVAL;
return 0;
}
static void bpf_struct_ops_link_release(struct bpf_link *link)
{
}
static void bpf_struct_ops_link_dealloc(struct bpf_link *link)
{
struct bpf_tramp_link *tlink = container_of(link, struct bpf_tramp_link, link);
kfree(tlink);
}
const struct bpf_link_ops bpf_struct_ops_link_lops = {
.release = bpf_struct_ops_link_release,
.dealloc = bpf_struct_ops_link_dealloc,
};
int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
struct bpf_tramp_link *link,
const struct btf_func_model *model,
void *stub_func,
void **_image, u32 *_image_off,
bool allow_alloc)
{
u32 image_off = *_image_off, flags = BPF_TRAMP_F_INDIRECT;
void *image = *_image;
int size;
tlinks[BPF_TRAMP_FENTRY].links[0] = link;
tlinks[BPF_TRAMP_FENTRY].nr_links = 1;
if (model->ret_size > 0)
flags |= BPF_TRAMP_F_RET_FENTRY_RET;
size = arch_bpf_trampoline_size(model, flags, tlinks, NULL);
if (size <= 0)
return size ? : -EFAULT;
/* Allocate image buffer if necessary */
if (!image || size > PAGE_SIZE - image_off) {
if (!allow_alloc)
return -E2BIG;
image = bpf_struct_ops_image_alloc();
if (IS_ERR(image))
return PTR_ERR(image);
image_off = 0;
}
size = arch_prepare_bpf_trampoline(NULL, image + image_off,
image + image_off + size,
model, flags, tlinks, stub_func);
if (size <= 0) {
if (image != *_image)
bpf_struct_ops_image_free(image);
return size ? : -EFAULT;
}
*_image = image;
*_image_off = image_off + size;
return 0;
}
static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
void *value, u64 flags)
{
struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
const struct bpf_struct_ops_desc *st_ops_desc = st_map->st_ops_desc;
const struct bpf_struct_ops *st_ops = st_ops_desc->st_ops;
struct bpf_struct_ops_value *uvalue, *kvalue;
const struct btf_type *module_type;
const struct btf_member *member;
const struct btf_type *t = st_ops_desc->type;
struct bpf_tramp_links *tlinks;
void *udata, *kdata;
int prog_fd, err;
u32 i, trampoline_start, image_off = 0;
void *cur_image = NULL, *image = NULL;
if (flags)
return -EINVAL;
if (*(u32 *)key != 0)
return -E2BIG;
err = check_zero_holes(st_map->btf, st_ops_desc->value_type, value);
if (err)
return err;
uvalue = value;
err = check_zero_holes(st_map->btf, t, uvalue->data);
if (err)
return err;
if (uvalue->common.state || refcount_read(&uvalue->common.refcnt))
return -EINVAL;
tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
if (!tlinks)
return -ENOMEM;
uvalue = (struct bpf_struct_ops_value *)st_map->uvalue;
kvalue = (struct bpf_struct_ops_value *)&st_map->kvalue;
mutex_lock(&st_map->lock);
if (kvalue->common.state != BPF_STRUCT_OPS_STATE_INIT) {
err = -EBUSY;
goto unlock;
}
memcpy(uvalue, value, map->value_size);
udata = &uvalue->data;
kdata = &kvalue->data;
module_type = btf_type_by_id(btf_vmlinux, st_ops_ids[IDX_MODULE_ID]);
for_each_member(i, t, member) {
const struct btf_type *mtype, *ptype;
struct bpf_prog *prog;
struct bpf_tramp_link *link;
u32 moff;
moff = __btf_member_bit_offset(t, member) / 8;
ptype = btf_type_resolve_ptr(st_map->btf, member->type, NULL);
if (ptype == module_type) {
if (*(void **)(udata + moff))
goto reset_unlock;
*(void **)(kdata + moff) = BPF_MODULE_OWNER;
continue;
}
err = st_ops->init_member(t, member, kdata, udata);
if (err < 0)
goto reset_unlock;
/* The ->init_member() has handled this member */
if (err > 0)
continue;
/* If st_ops->init_member does not handle it,
* we will only handle func ptrs and zero-ed members
* here. Reject everything else.
*/
/* All non func ptr member must be 0 */
if (!ptype || !btf_type_is_func_proto(ptype)) {
u32 msize;
mtype = btf_type_by_id(st_map->btf, member->type);
mtype = btf_resolve_size(st_map->btf, mtype, &msize);
if (IS_ERR(mtype)) {
err = PTR_ERR(mtype);
goto reset_unlock;
}
if (memchr_inv(udata + moff, 0, msize)) {
err = -EINVAL;
goto reset_unlock;
}
continue;
}
prog_fd = (int)(*(unsigned long *)(udata + moff));
/* Similar check as the attr->attach_prog_fd */
if (!prog_fd)
continue;
prog = bpf_prog_get(prog_fd);
if (IS_ERR(prog)) {
err = PTR_ERR(prog);
goto reset_unlock;
}
if (prog->type != BPF_PROG_TYPE_STRUCT_OPS ||
prog->aux->attach_btf_id != st_ops_desc->type_id ||
prog->expected_attach_type != i) {
bpf_prog_put(prog);
err = -EINVAL;
goto reset_unlock;
}
link = kzalloc(sizeof(*link), GFP_USER);
if (!link) {
bpf_prog_put(prog);
err = -ENOMEM;
goto reset_unlock;
}
bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS,
&bpf_struct_ops_link_lops, prog);
st_map->links[i] = &link->link;
trampoline_start = image_off;
err = bpf_struct_ops_prepare_trampoline(tlinks, link,
&st_ops->func_models[i],
*(void **)(st_ops->cfi_stubs + moff),
&image, &image_off,
st_map->image_pages_cnt < MAX_TRAMP_IMAGE_PAGES);
if (err)
goto reset_unlock;
if (cur_image != image) {
st_map->image_pages[st_map->image_pages_cnt++] = image;
cur_image = image;
trampoline_start = 0;
}
*(void **)(kdata + moff) = image + trampoline_start + cfi_get_offset();
/* put prog_id to udata */
*(unsigned long *)(udata + moff) = prog->aux->id;
}
if (st_ops->validate) {
err = st_ops->validate(kdata);
if (err)
goto reset_unlock;
}
for (i = 0; i < st_map->image_pages_cnt; i++) {
err = arch_protect_bpf_trampoline(st_map->image_pages[i],
PAGE_SIZE);
if (err)
goto reset_unlock;
}
if (st_map->map.map_flags & BPF_F_LINK) {
err = 0;
/* Let bpf_link handle registration & unregistration.
*
* Pair with smp_load_acquire() during lookup_elem().
*/
smp_store_release(&kvalue->common.state, BPF_STRUCT_OPS_STATE_READY);
goto unlock;
}
err = st_ops->reg(kdata, NULL);
if (likely(!err)) {
/* This refcnt increment on the map here after
* 'st_ops->reg()' is secure since the state of the
* map must be set to INIT at this moment, and thus
* bpf_struct_ops_map_delete_elem() can't unregister
* or transition it to TOBEFREE concurrently.
*/
bpf_map_inc(map);
/* Pair with smp_load_acquire() during lookup_elem().
* It ensures the above udata updates (e.g. prog->aux->id)
* can be seen once BPF_STRUCT_OPS_STATE_INUSE is set.
*/
smp_store_release(&kvalue->common.state, BPF_STRUCT_OPS_STATE_INUSE);
goto unlock;
}
/* Error during st_ops->reg(). Can happen if this struct_ops needs to be
* verified as a whole, after all init_member() calls. Can also happen if
* there was a race in registering the struct_ops (under the same name) to
* a sub-system through different struct_ops's maps.
*/
reset_unlock:
bpf_struct_ops_map_free_image(st_map);
bpf_struct_ops_map_put_progs(st_map);
memset(uvalue, 0, map->value_size);
memset(kvalue, 0, map->value_size);
unlock:
kfree(tlinks);
mutex_unlock(&st_map->lock);
return err;
}
static long bpf_struct_ops_map_delete_elem(struct bpf_map *map, void *key)
{
enum bpf_struct_ops_state prev_state;
struct bpf_struct_ops_map *st_map;
st_map = (struct bpf_struct_ops_map *)map;
if (st_map->map.map_flags & BPF_F_LINK)
return -EOPNOTSUPP;
prev_state = cmpxchg(&st_map->kvalue.common.state,
BPF_STRUCT_OPS_STATE_INUSE,
BPF_STRUCT_OPS_STATE_TOBEFREE);
switch (prev_state) {
case BPF_STRUCT_OPS_STATE_INUSE:
st_map->st_ops_desc->st_ops->unreg(&st_map->kvalue.data, NULL);
bpf_map_put(map);
return 0;
case BPF_STRUCT_OPS_STATE_TOBEFREE:
return -EINPROGRESS;
case BPF_STRUCT_OPS_STATE_INIT:
return -ENOENT;
default:
WARN_ON_ONCE(1);
/* Should never happen. Treat it as not found. */
return -ENOENT;
}
}
static void bpf_struct_ops_map_seq_show_elem(struct bpf_map *map, void *key,
struct seq_file *m)
{
struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
void *value;
int err;
value = kmalloc(map->value_size, GFP_USER | __GFP_NOWARN);
if (!value)
return;
err = bpf_struct_ops_map_sys_lookup_elem(map, key, value);
if (!err) {
btf_type_seq_show(st_map->btf,
map->btf_vmlinux_value_type_id,
value, m);
seq_putc(m, '\n');
}
kfree(value);
}
static void __bpf_struct_ops_map_free(struct bpf_map *map)
{
struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
if (st_map->links)
bpf_struct_ops_map_put_progs(st_map);
bpf_map_area_free(st_map->links);
bpf_struct_ops_map_free_image(st_map);
bpf_map_area_free(st_map->uvalue);
bpf_map_area_free(st_map);
}
static void bpf_struct_ops_map_free(struct bpf_map *map)
{
struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
/* st_ops->owner was acquired during map_alloc to implicitly holds
* the btf's refcnt. The acquire was only done when btf_is_module()
* st_map->btf cannot be NULL here.
*/
if (btf_is_module(st_map->btf))
module_put(st_map->st_ops_desc->st_ops->owner);
/* The struct_ops's function may switch to another struct_ops.
*
* For example, bpf_tcp_cc_x->init() may switch to
* another tcp_cc_y by calling
* setsockopt(TCP_CONGESTION, "tcp_cc_y").
* During the switch, bpf_struct_ops_put(tcp_cc_x) is called
* and its refcount may reach 0 which then free its
* trampoline image while tcp_cc_x is still running.
*
* A vanilla rcu gp is to wait for all bpf-tcp-cc prog
* to finish. bpf-tcp-cc prog is non sleepable.
* A rcu_tasks gp is to wait for the last few insn
* in the tramopline image to finish before releasing
* the trampoline image.
*/
synchronize_rcu_mult(call_rcu, call_rcu_tasks);
__bpf_struct_ops_map_free(map);
}
static int bpf_struct_ops_map_alloc_check(union bpf_attr *attr)
{
if (attr->key_size != sizeof(unsigned int) || attr->max_entries != 1 ||
(attr->map_flags & ~(BPF_F_LINK | BPF_F_VTYPE_BTF_OBJ_FD)) ||
!attr->btf_vmlinux_value_type_id)
return -EINVAL;
return 0;
}
static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
{
const struct bpf_struct_ops_desc *st_ops_desc;
size_t st_map_size;
struct bpf_struct_ops_map *st_map;
const struct btf_type *t, *vt;
struct module *mod = NULL;
struct bpf_map *map;
struct btf *btf;
int ret;
if (attr->map_flags & BPF_F_VTYPE_BTF_OBJ_FD) {
/* The map holds btf for its whole life time. */
btf = btf_get_by_fd(attr->value_type_btf_obj_fd);
if (IS_ERR(btf))
return ERR_CAST(btf);
if (!btf_is_module(btf)) {
btf_put(btf);
return ERR_PTR(-EINVAL);
}
mod = btf_try_get_module(btf);
/* mod holds a refcnt to btf. We don't need an extra refcnt
* here.
*/
btf_put(btf);
if (!mod)
return ERR_PTR(-EINVAL);
} else {
btf = bpf_get_btf_vmlinux();
if (IS_ERR(btf))
return ERR_CAST(btf);
if (!btf)
return ERR_PTR(-ENOTSUPP);
}
st_ops_desc = bpf_struct_ops_find_value(btf, attr->btf_vmlinux_value_type_id);
if (!st_ops_desc) {
ret = -ENOTSUPP;
goto errout;
}
vt = st_ops_desc->value_type;
if (attr->value_size != vt->size) {
ret = -EINVAL;
goto errout;
}
t = st_ops_desc->type;
st_map_size = sizeof(*st_map) +
/* kvalue stores the
* struct bpf_struct_ops_tcp_congestions_ops
*/
(vt->size - sizeof(struct bpf_struct_ops_value));
st_map = bpf_map_area_alloc(st_map_size, NUMA_NO_NODE);
if (!st_map) {
ret = -ENOMEM;
goto errout;
}
st_map->st_ops_desc = st_ops_desc;
map = &st_map->map;
st_map->uvalue = bpf_map_area_alloc(vt->size, NUMA_NO_NODE);
st_map->links_cnt = btf_type_vlen(t);
st_map->links =
bpf_map_area_alloc(st_map->links_cnt * sizeof(struct bpf_links *),
NUMA_NO_NODE);
if (!st_map->uvalue || !st_map->links) {
ret = -ENOMEM;
goto errout_free;
}
st_map->btf = btf;
mutex_init(&st_map->lock);
bpf_map_init_from_attr(map, attr);
return map;
errout_free:
__bpf_struct_ops_map_free(map);
errout:
module_put(mod);
return ERR_PTR(ret);
}
static u64 bpf_struct_ops_map_mem_usage(const struct bpf_map *map)
{
struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
const struct bpf_struct_ops_desc *st_ops_desc = st_map->st_ops_desc;
const struct btf_type *vt = st_ops_desc->value_type;
u64 usage;
usage = sizeof(*st_map) +
vt->size - sizeof(struct bpf_struct_ops_value);
usage += vt->size;
usage += btf_type_vlen(vt) * sizeof(struct bpf_links *);
usage += PAGE_SIZE;
return usage;
}
BTF_ID_LIST_SINGLE(bpf_struct_ops_map_btf_ids, struct, bpf_struct_ops_map)
const struct bpf_map_ops bpf_struct_ops_map_ops = {
.map_alloc_check = bpf_struct_ops_map_alloc_check,
.map_alloc = bpf_struct_ops_map_alloc,
.map_free = bpf_struct_ops_map_free,
.map_get_next_key = bpf_struct_ops_map_get_next_key,
.map_lookup_elem = bpf_struct_ops_map_lookup_elem,
.map_delete_elem = bpf_struct_ops_map_delete_elem,
.map_update_elem = bpf_struct_ops_map_update_elem,
.map_seq_show_elem = bpf_struct_ops_map_seq_show_elem,
.map_mem_usage = bpf_struct_ops_map_mem_usage,
.map_btf_id = &bpf_struct_ops_map_btf_ids[0],
};
/* "const void *" because some subsystem is
* passing a const (e.g. const struct tcp_congestion_ops *)
*/
bool bpf_struct_ops_get(const void *kdata)
{
struct bpf_struct_ops_value *kvalue;
struct bpf_struct_ops_map *st_map;
struct bpf_map *map;
kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
st_map = container_of(kvalue, struct bpf_struct_ops_map, kvalue);
map = __bpf_map_inc_not_zero(&st_map->map, false);
return !IS_ERR(map);
}
void bpf_struct_ops_put(const void *kdata)
{
struct bpf_struct_ops_value *kvalue;
struct bpf_struct_ops_map *st_map;
kvalue = container_of(kdata, struct bpf_struct_ops_value, data);
st_map = container_of(kvalue, struct bpf_struct_ops_map, kvalue);
bpf_map_put(&st_map->map);
}
int bpf_struct_ops_supported(const struct bpf_struct_ops *st_ops, u32 moff)
{
void *func_ptr = *(void **)(st_ops->cfi_stubs + moff);
return func_ptr ? 0 : -ENOTSUPP;
}
static bool bpf_struct_ops_valid_to_reg(struct bpf_map *map)
{
struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
return map->map_type == BPF_MAP_TYPE_STRUCT_OPS &&
map->map_flags & BPF_F_LINK &&
/* Pair with smp_store_release() during map_update */
smp_load_acquire(&st_map->kvalue.common.state) == BPF_STRUCT_OPS_STATE_READY;
}
static void bpf_struct_ops_map_link_dealloc(struct bpf_link *link)
{
struct bpf_struct_ops_link *st_link;
struct bpf_struct_ops_map *st_map;
st_link = container_of(link, struct bpf_struct_ops_link, link);
st_map = (struct bpf_struct_ops_map *)
rcu_dereference_protected(st_link->map, true);
if (st_map) {
st_map->st_ops_desc->st_ops->unreg(&st_map->kvalue.data, link);
bpf_map_put(&st_map->map);
}
kfree(st_link);
}
static void bpf_struct_ops_map_link_show_fdinfo(const struct bpf_link *link,
struct seq_file *seq)
{
struct bpf_struct_ops_link *st_link;
struct bpf_map *map;
st_link = container_of(link, struct bpf_struct_ops_link, link);
rcu_read_lock();
map = rcu_dereference(st_link->map);
if (map)
seq_printf(seq, "map_id:\t%d\n", map->id);
rcu_read_unlock();
}
static int bpf_struct_ops_map_link_fill_link_info(const struct bpf_link *link,
struct bpf_link_info *info)
{
struct bpf_struct_ops_link *st_link;
struct bpf_map *map;
st_link = container_of(link, struct bpf_struct_ops_link, link);
rcu_read_lock();
map = rcu_dereference(st_link->map);
if (map)
info->struct_ops.map_id = map->id;
rcu_read_unlock();
return 0;
}
static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map *new_map,
struct bpf_map *expected_old_map)
{
struct bpf_struct_ops_map *st_map, *old_st_map;
struct bpf_map *old_map;
struct bpf_struct_ops_link *st_link;
int err;
st_link = container_of(link, struct bpf_struct_ops_link, link);
st_map = container_of(new_map, struct bpf_struct_ops_map, map);
if (!bpf_struct_ops_valid_to_reg(new_map))
return -EINVAL;
if (!st_map->st_ops_desc->st_ops->update)
return -EOPNOTSUPP;
mutex_lock(&update_mutex);
old_map = rcu_dereference_protected(st_link->map, lockdep_is_held(&update_mutex));
if (!old_map) {
err = -ENOLINK;
goto err_out;
}
if (expected_old_map && old_map != expected_old_map) {
err = -EPERM;
goto err_out;
}
old_st_map = container_of(old_map, struct bpf_struct_ops_map, map);
/* The new and old struct_ops must be the same type. */
if (st_map->st_ops_desc != old_st_map->st_ops_desc) {
err = -EINVAL;
goto err_out;
}
err = st_map->st_ops_desc->st_ops->update(st_map->kvalue.data, old_st_map->kvalue.data, link);
if (err)
goto err_out;
bpf_map_inc(new_map);
rcu_assign_pointer(st_link->map, new_map);
bpf_map_put(old_map);
err_out:
mutex_unlock(&update_mutex);
return err;
}
static int bpf_struct_ops_map_link_detach(struct bpf_link *link)
{
struct bpf_struct_ops_link *st_link = container_of(link, struct bpf_struct_ops_link, link);
struct bpf_struct_ops_map *st_map;
struct bpf_map *map;
mutex_lock(&update_mutex);
map = rcu_dereference_protected(st_link->map, lockdep_is_held(&update_mutex));
if (!map) {
mutex_unlock(&update_mutex);
return 0;
}
st_map = container_of(map, struct bpf_struct_ops_map, map);
st_map->st_ops_desc->st_ops->unreg(&st_map->kvalue.data, link);
RCU_INIT_POINTER(st_link->map, NULL);
/* Pair with bpf_map_get() in bpf_struct_ops_link_create() or
* bpf_map_inc() in bpf_struct_ops_map_link_update().
*/
bpf_map_put(&st_map->map);
mutex_unlock(&update_mutex);
wake_up_interruptible_poll(&st_link->wait_hup, EPOLLHUP);
return 0;
}
static __poll_t bpf_struct_ops_map_link_poll(struct file *file,
struct poll_table_struct *pts)
{
struct bpf_struct_ops_link *st_link = file->private_data;
poll_wait(file, &st_link->wait_hup, pts);
return rcu_access_pointer(st_link->map) ? 0 : EPOLLHUP;
}
static const struct bpf_link_ops bpf_struct_ops_map_lops = {
.dealloc = bpf_struct_ops_map_link_dealloc,
.detach = bpf_struct_ops_map_link_detach,
.show_fdinfo = bpf_struct_ops_map_link_show_fdinfo,
.fill_link_info = bpf_struct_ops_map_link_fill_link_info,
.update_map = bpf_struct_ops_map_link_update,
.poll = bpf_struct_ops_map_link_poll,
};
int bpf_struct_ops_link_create(union bpf_attr *attr)
{
struct bpf_struct_ops_link *link = NULL;
struct bpf_link_primer link_primer;
struct bpf_struct_ops_map *st_map;
struct bpf_map *map;
int err;
map = bpf_map_get(attr->link_create.map_fd);
if (IS_ERR(map))
return PTR_ERR(map);
st_map = (struct bpf_struct_ops_map *)map;
if (!bpf_struct_ops_valid_to_reg(map)) {
err = -EINVAL;
goto err_out;
}
link = kzalloc(sizeof(*link), GFP_USER);
if (!link) {
err = -ENOMEM;
goto err_out;
}
bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_map_lops, NULL);
err = bpf_link_prime(&link->link, &link_primer);
if (err)
goto err_out;
init_waitqueue_head(&link->wait_hup);
/* Hold the update_mutex such that the subsystem cannot
* do link->ops->detach() before the link is fully initialized.
*/
mutex_lock(&update_mutex);
err = st_map->st_ops_desc->st_ops->reg(st_map->kvalue.data, &link->link);
if (err) {
mutex_unlock(&update_mutex);
bpf_link_cleanup(&link_primer);
link = NULL;
goto err_out;
}
RCU_INIT_POINTER(link->map, map);
mutex_unlock(&update_mutex);
return bpf_link_settle(&link_primer);
err_out:
bpf_map_put(map);
kfree(link);
return err;
}
void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map)
{
struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
info->btf_vmlinux_id = btf_obj_id(st_map->btf);
}
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