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// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2020 Facebook */
#include <linux/fs.h>
#include <linux/filter.h>
#include <linux/bpf.h>
struct bpf_iter_target_info {
struct list_head list;
const char *target;
const struct seq_operations *seq_ops;
bpf_iter_init_seq_priv_t init_seq_private;
bpf_iter_fini_seq_priv_t fini_seq_private;
u32 seq_priv_size;
u32 btf_id; /* cached value */
};
struct bpf_iter_link {
struct bpf_link link;
struct bpf_iter_target_info *tinfo;
};
static struct list_head targets = LIST_HEAD_INIT(targets);
static DEFINE_MUTEX(targets_mutex);
/* protect bpf_iter_link changes */
static DEFINE_MUTEX(link_mutex);
int bpf_iter_reg_target(struct bpf_iter_reg *reg_info)
{
struct bpf_iter_target_info *tinfo;
tinfo = kmalloc(sizeof(*tinfo), GFP_KERNEL);
if (!tinfo)
return -ENOMEM;
tinfo->target = reg_info->target;
tinfo->seq_ops = reg_info->seq_ops;
tinfo->init_seq_private = reg_info->init_seq_private;
tinfo->fini_seq_private = reg_info->fini_seq_private;
tinfo->seq_priv_size = reg_info->seq_priv_size;
INIT_LIST_HEAD(&tinfo->list);
mutex_lock(&targets_mutex);
list_add(&tinfo->list, &targets);
mutex_unlock(&targets_mutex);
return 0;
}
void bpf_iter_unreg_target(const char *target)
{
struct bpf_iter_target_info *tinfo;
bool found = false;
mutex_lock(&targets_mutex);
list_for_each_entry(tinfo, &targets, list) {
if (!strcmp(target, tinfo->target)) {
list_del(&tinfo->list);
kfree(tinfo);
found = true;
break;
}
}
mutex_unlock(&targets_mutex);
WARN_ON(found == false);
}
static void cache_btf_id(struct bpf_iter_target_info *tinfo,
struct bpf_prog *prog)
{
tinfo->btf_id = prog->aux->attach_btf_id;
}
bool bpf_iter_prog_supported(struct bpf_prog *prog)
{
const char *attach_fname = prog->aux->attach_func_name;
u32 prog_btf_id = prog->aux->attach_btf_id;
const char *prefix = BPF_ITER_FUNC_PREFIX;
struct bpf_iter_target_info *tinfo;
int prefix_len = strlen(prefix);
bool supported = false;
if (strncmp(attach_fname, prefix, prefix_len))
return false;
mutex_lock(&targets_mutex);
list_for_each_entry(tinfo, &targets, list) {
if (tinfo->btf_id && tinfo->btf_id == prog_btf_id) {
supported = true;
break;
}
if (!strcmp(attach_fname + prefix_len, tinfo->target)) {
cache_btf_id(tinfo, prog);
supported = true;
break;
}
}
mutex_unlock(&targets_mutex);
return supported;
}
static void bpf_iter_link_release(struct bpf_link *link)
{
}
static void bpf_iter_link_dealloc(struct bpf_link *link)
{
struct bpf_iter_link *iter_link =
container_of(link, struct bpf_iter_link, link);
kfree(iter_link);
}
static int bpf_iter_link_replace(struct bpf_link *link,
struct bpf_prog *new_prog,
struct bpf_prog *old_prog)
{
int ret = 0;
mutex_lock(&link_mutex);
if (old_prog && link->prog != old_prog) {
ret = -EPERM;
goto out_unlock;
}
if (link->prog->type != new_prog->type ||
link->prog->expected_attach_type != new_prog->expected_attach_type ||
link->prog->aux->attach_btf_id != new_prog->aux->attach_btf_id) {
ret = -EINVAL;
goto out_unlock;
}
old_prog = xchg(&link->prog, new_prog);
bpf_prog_put(old_prog);
out_unlock:
mutex_unlock(&link_mutex);
return ret;
}
static const struct bpf_link_ops bpf_iter_link_lops = {
.release = bpf_iter_link_release,
.dealloc = bpf_iter_link_dealloc,
.update_prog = bpf_iter_link_replace,
};
int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
{
struct bpf_link_primer link_primer;
struct bpf_iter_target_info *tinfo;
struct bpf_iter_link *link;
bool existed = false;
u32 prog_btf_id;
int err;
if (attr->link_create.target_fd || attr->link_create.flags)
return -EINVAL;
prog_btf_id = prog->aux->attach_btf_id;
mutex_lock(&targets_mutex);
list_for_each_entry(tinfo, &targets, list) {
if (tinfo->btf_id == prog_btf_id) {
existed = true;
break;
}
}
mutex_unlock(&targets_mutex);
if (!existed)
return -ENOENT;
link = kzalloc(sizeof(*link), GFP_USER | __GFP_NOWARN);
if (!link)
return -ENOMEM;
bpf_link_init(&link->link, BPF_LINK_TYPE_ITER, &bpf_iter_link_lops, prog);
link->tinfo = tinfo;
err = bpf_link_prime(&link->link, &link_primer);
if (err) {
kfree(link);
return err;
}
return bpf_link_settle(&link_primer);
}
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