// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2019 Facebook */
#include <linux/hash.h>
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/ftrace.h>
#include <linux/rbtree_latch.h>
#include <linux/perf_event.h>
#include <linux/btf.h>
#include <linux/rcupdate_trace.h>
#include <linux/rcupdate_wait.h>
#include <linux/static_call.h>
#include <linux/bpf_verifier.h>
#include <linux/bpf_lsm.h>
#include <linux/delay.h>
/* dummy _ops. The verifier will operate on target program's ops. */
const struct bpf_verifier_ops bpf_extension_verifier_ops = {
};
const struct bpf_prog_ops bpf_extension_prog_ops = {
};
/* btf_vmlinux has ~22k attachable functions. 1k htab is enough. */
#define TRAMPOLINE_HASH_BITS 10
#define TRAMPOLINE_TABLE_SIZE (1 << TRAMPOLINE_HASH_BITS)
static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE];
/* serializes access to trampoline_table */
static DEFINE_MUTEX(trampoline_mutex);
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex);
static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, enum ftrace_ops_cmd cmd)
{
struct bpf_trampoline *tr = ops->private;
int ret = 0;
if (cmd == FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF) {
/* This is called inside register_ftrace_direct_multi(), so
* tr->mutex is already locked.
*/
lockdep_assert_held_once(&tr->mutex);
/* Instead of updating the trampoline here, we propagate
* -EAGAIN to register_ftrace_direct(). Then we can
* retry register_ftrace_direct() after updating the
* trampoline.
*/
if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
!(tr->flags & BPF_TRAMP_F_ORIG_STACK)) {
if (WARN_ON_ONCE(tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY))
return -EBUSY;
tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
return -EAGAIN;
}
return 0;
}
/* The normal locking order is
* tr->mutex => direct_mutex (ftrace.c) => ftrace_lock (ftrace.c)
*
* The following two commands are called from
*
* prepare_direct_functions_for_ipmodify
* cleanup_direct_functions_after_ipmodify
*
* In both cases, direct_mutex is already locked. Use
* mutex_trylock(&tr->mutex) to avoid deadlock in race condition
* (something else is making changes to this same trampoline).
*/
if (!mutex_trylock(&tr->mutex)) {
/* sleep 1 ms to make sure whatever holding tr->mutex makes
* some progress.
*/
msleep(1);
return -EAGAIN;
}
switch (cmd) {
case FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER:
tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
!(tr->flags & BPF_TRAMP_F_ORIG_STACK))
ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
break;
case FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER:
tr->flags &= ~BPF_TRAMP_F_SHARE_IPMODIFY;
if (tr->flags & BPF_TRAMP_F_ORIG_STACK)
ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
break;
default:
ret = -EINVAL;
break;
}
mutex_unlock(&tr->mutex);
return ret;
}
#endif
bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
{
enum bpf_attach_type eatype = prog->expected_attach_type;
enum bpf_prog_type ptype = prog->type;
return (ptype == BPF_PROG_TYPE_TRACING &&
(eatype == BPF_TRACE_FENTRY || eatype == BPF_TRACE_FEXIT ||
eatype == BPF_MODIFY_RETURN)) ||
(ptype == BPF_PROG_TYPE_LSM && eatype == BPF_LSM_MAC);
}
void bpf_image_ksym_add(void *data, unsigned int size, struct bpf_ksym *ksym)
{
ksym->start = (unsigned long) data;
ksym->end = ksym->start + size;
bpf_ksym_add(ksym);
perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
PAGE_SIZE, false, ksym->name);
}
void bpf_image_ksym_del(struct bpf_ksym *ksym)
{
bpf_ksym_del(ksym);
perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
PAGE_SIZE, true, ksym->name);
}
static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
{
struct bpf_trampoline *tr;
struct hlist_head *head;
int i;
mutex_lock(&trampoline_mutex);
head = &trampoline_table[hash_64(key, TRAMPOLINE_HASH_BITS)];
hlist_for_each_entry(tr, head, hlist) {
if (tr->key == key) {
refcount_inc(&tr->refcnt);
goto out;
}
}
tr = kzalloc(sizeof(*tr), GFP_KERNEL);
if (!tr)
goto out;
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL);
if (!tr->fops) {
kfree(tr);
tr = NULL;
goto out;
}
tr->fops->private = tr;
tr->fops->ops_func = bpf_tramp_ftrace_ops_func;
#endif
tr->key = key;
INIT_HLIST_NODE(&tr->hlist);
hlist_add_head(&tr->hlist, head);
refcount_set(&tr->refcnt, 1);
mutex_init(&tr->mutex);
for (i = 0; i < BPF_TRAMP_MAX; i++)
INIT_HLIST_HEAD(&tr->progs_hlist[i]);
out:
mutex_unlock(&trampoline_mutex);
return tr;
}
static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
{
void *ip = tr->func.addr;
int ret;
if (tr->func.ftrace_managed)
ret = unregister_ftrace_direct(tr->fops, (long)old_addr, false);
else
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
return ret;
}
static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr,
bool lock_direct_mutex)
{
void *ip = tr->func.addr;
int ret;
if (tr->func.ftrace_managed) {
if (lock_direct_mutex)
ret = modify_ftrace_direct(tr->fops, (long)new_addr);
else
ret = modify_ftrace_direct_nolock(tr->fops, (long)new_addr);
} else {
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr);
}
return ret;
}
/* first time registering */
static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
{
void *ip = tr->func.addr;
unsigned long faddr;
int ret;
faddr = ftrace_location((unsigned long)ip);
if (faddr) {
if (!tr->fops)
return -ENOTSUPP;
tr->func.ftrace_managed = true;
}
if (tr->func.ftrace_managed) {
ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 1);
ret = register_ftrace_direct(tr->fops, (long)new_addr);
} else {
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
}
return ret;
}
static struct bpf_tramp_links *
bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg)
{
struct bpf_tramp_link *link;
struct bpf_tramp_links *tlinks;
struct bpf_tramp_link **links;
int kind;
*total = 0;
tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
if (!tlinks)
return ERR_PTR(-ENOMEM);
for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
tlinks[kind].nr_links = tr->progs_cnt[kind];
*total += tr->progs_cnt[kind];
links = tlinks[kind].links;
hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
*ip_arg |= link->link.prog->call_get_func_ip;
*links++ = link;
}
}
return tlinks;
}
static void bpf_tramp_image_free(struct bpf_tramp_image *im)
{
bpf_image_ksym_del(&im->ksym);
arch_free_bpf_trampoline(im->image, im->size);
bpf_jit_uncharge_modmem(im->size);
percpu_ref_exit(&im->pcref);
kfree_rcu(im, rcu);
}
static void __bpf_tramp_image_put_deferred(struct work_struct *work)
{
struct bpf_tramp_image *im;
im = container_of(work, struct bpf_tramp_image, work);
bpf_tramp_image_free(im);
}
/* callback, fexit step 3 or fentry step 2 */
static void __bpf_tramp_image_put_rcu(struct rcu_head *rcu)
{
struct bpf_tramp_image *im;
im = container_of(rcu, struct bpf_tramp_image, rcu);
INIT_WORK(&im->work, __bpf_tramp_image_put_deferred);
schedule_work(&im->work);
}
/* callback, fexit step 2. Called after percpu_ref_kill confirms. */
static void __bpf_tramp_image_release(struct percpu_ref *pcref)
{
struct bpf_tramp_image *im;
im = container_of(pcref, struct bpf_tramp_image, pcref);
call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
}
/* callback, fexit or fentry step 1 */
static void __bpf_tramp_image_put_rcu_tasks(struct rcu_head *rcu)
{
struct bpf_tramp_image *im;
im = container_of(rcu, struct bpf_tramp_image, rcu);
if (im->ip_after_call)
/* the case of fmod_ret/fexit trampoline and CONFIG_PREEMPTION=y */
percpu_ref_kill(&im->pcref);
else
/* the case of fentry trampoline */
call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
}
static void bpf_tramp_image_put(struct bpf_tramp_image *im)
{
/* The trampoline image that calls original function is using:
* rcu_read_lock_trace to protect sleepable bpf progs
* rcu_read_lock to protect normal bpf progs
* percpu_ref to protect trampoline itself
* rcu tasks to protect trampoline asm not covered by percpu_ref
* (which are few asm insns before __bpf_tramp_enter and
* after __bpf_tramp_exit)
*
* The trampoline is unreachable before bpf_tramp_image_put().
*
* First, patch the trampoline to avoid calling into fexit progs.
* The progs will be freed even if the original function is still
* executing or sleeping.
* In case of CONFIG_PREEMPT=y use call_rcu_tasks() to wait on
* first few asm instructions to execute and call into
* __bpf_tramp_enter->percpu_ref_get.
* Then use percpu_ref_kill to wait for the trampoline and the original
* function to finish.
* Then use call_rcu_tasks() to make sure few asm insns in
* the trampoline epilogue are done as well.
*
* In !PREEMPT case the task that got interrupted in the first asm
* insns won't go through an RCU quiescent state which the
* percpu_ref_kill will be waiting for. Hence the first
* call_rcu_tasks() is not necessary.
*/
if (im->ip_after_call) {
int err = bpf_arch_text_poke(im->ip_after_call, BPF_MOD_JUMP,
NULL, im->ip_epilogue);
WARN_ON(err);
if (IS_ENABLED(CONFIG_TASKS_RCU))
call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
else
percpu_ref_kill(&im->pcref);
return;
}
/* The trampoline without fexit and fmod_ret progs doesn't call original
* function and doesn't use percpu_ref.
* Use call_rcu_tasks_trace() to wait for sleepable progs to finish.
* Then use call_rcu_tasks() to wait for the rest of trampoline asm
* and normal progs.
*/
call_rcu_tasks_trace(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
}
static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, int size)
{
struct bpf_tramp_image *im;
struct bpf_ksym *ksym;
void *image;
int err = -ENOMEM;
im = kzalloc(sizeof(*im), GFP_KERNEL);
if (!im)
goto out;
err = bpf_jit_charge_modmem(size);
if (err)
goto out_free_im;
im->size = size;
err = -ENOMEM;
im->image = image = arch_alloc_bpf_trampoline(size);
if (!image)
goto out_uncharge;
err = percpu_ref_init(&im->pcref, __bpf_tramp_image_release, 0, GFP_KERNEL);
if (err)
goto out_free_image;
ksym = &im->ksym;
INIT_LIST_HEAD_RCU(&ksym->lnode);
snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu", key);
bpf_image_ksym_add(image, size, ksym);
return im;
out_free_image:
arch_free_bpf_trampoline(im->image, im->size);
out_uncharge:
bpf_jit_uncharge_modmem(size);
out_free_im:
kfree(im);
out:
return ERR_PTR(err);
}
static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex)
{
struct bpf_tramp_image *im;
struct bpf_tramp_links *tlinks;
u32 orig_flags = tr->flags;
bool ip_arg = false;
int err, total, size;
tlinks = bpf_trampoline_get_progs(tr, &total, &ip_arg);
if (IS_ERR(tlinks))
return PTR_ERR(tlinks);
if (total == 0) {
err = unregister_fentry(tr, tr->cur_image->image);
bpf_tramp_image_put(tr->cur_image);
tr->cur_image = NULL;
goto out;
}
/* clear all bits except SHARE_IPMODIFY and TAIL_CALL_CTX */
tr->flags &= (BPF_TRAMP_F_SHARE_IPMODIFY | BPF_TRAMP_F_TAIL_CALL_CTX);
if (tlinks[BPF_TRAMP_FEXIT].nr_links ||
tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links) {
/* NOTE: BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME
* should not be set together.
*/
tr->flags |= BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
} else {
tr->flags |= BPF_TRAMP_F_RESTORE_REGS;
}
if (ip_arg)
tr->flags |= BPF_TRAMP_F_IP_ARG;
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
again:
if ((tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY) &&
(tr->flags & BPF_TRAMP_F_CALL_ORIG))
tr->flags |= BPF_TRAMP_F_ORIG_STACK;
#endif
size = arch_bpf_trampoline_size(&tr->func.model, tr->flags,
tlinks, tr->func.addr);
if (size < 0) {
err = size;
goto out;
}
if (size > PAGE_SIZE) {
err = -E2BIG;
goto out;
}
im = bpf_tramp_image_alloc(tr->key, size);
if (IS_ERR(im)) {
err = PTR_ERR(im);
goto out;
}
err = arch_prepare_bpf_trampoline(im, im->image, im->image + size,
&tr->func.model, tr->flags, tlinks,
tr->func.addr);
if (err < 0)
goto out_free;
err = arch_protect_bpf_trampoline(im->image, im->size);
if (err)
goto out_free;
WARN_ON(tr->cur_image && total == 0);
if (tr->cur_image)
/* progs already running at this address */
err = modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_mutex);
else
/* first time registering */
err = register_fentry(tr, im->image);
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
if (err == -EAGAIN) {
/* -EAGAIN from bpf_tramp_ftrace_ops_func. Now
* BPF_TRAMP_F_SHARE_IPMODIFY is set, we can generate the
* trampoline again, and retry register.
*/
/* reset fops->func and fops->trampoline for re-register */
tr->fops->func = NULL;
tr->fops->trampoline = 0;
/* free im memory and reallocate later */
bpf_tramp_image_free(im);
goto again;
}
#endif
if (err)
goto out_free;
if (tr->cur_image)
bpf_tramp_image_put(tr->cur_image);
tr->cur_image = im;
out:
/* If any error happens, restore previous flags */
if (err)
tr->flags = orig_flags;
kfree(tlinks);
return err;
out_free:
bpf_tramp_image_free(im);
goto out;
}
static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
{
switch (prog->expected_attach_type) {
case BPF_TRACE_FENTRY:
return BPF_TRAMP_FENTRY;
case BPF_MODIFY_RETURN:
return BPF_TRAMP_MODIFY_RETURN;
case BPF_TRACE_FEXIT:
return BPF_TRAMP_FEXIT;
case BPF_LSM_MAC:
if (!prog->aux->attach_func_proto->type)
/* The function returns void, we cannot modify its
* return value.
*/
return BPF_TRAMP_FEXIT;
else
return BPF_TRAMP_MODIFY_RETURN;
default:
return BPF_TRAMP_REPLACE;
}
}
static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
{
enum bpf_tramp_prog_type kind;
struct bpf_tramp_link *link_exiting;
int err = 0;
int cnt = 0, i;
kind = bpf_attach_type_to_tramp(link->link.prog);
if (tr->extension_prog)
/* cannot attach fentry/fexit if extension prog is attached.
* cannot overwrite extension prog either.
*/
return -EBUSY;
for (i = 0; i < BPF_TRAMP_MAX; i++)
cnt += tr->progs_cnt[i];
if (kind == BPF_TRAMP_REPLACE) {
/* Cannot attach extension if fentry/fexit are in use. */
if (cnt)
return -EBUSY;
tr->extension_prog = link->link.prog;
return bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
link->link.prog->bpf_func);
}
if (cnt >= BPF_MAX_TRAMP_LINKS)
return -E2BIG;
if (!hlist_unhashed(&link->tramp_hlist))
/* prog already linked */
return -EBUSY;
hlist_for_each_entry(link_exiting, &tr->progs_hlist[kind], tramp_hlist) {
if (link_exiting->link.prog != link->link.prog)
continue;
/* prog already linked */
return -EBUSY;
}
hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]);
tr->progs_cnt[kind]++;
err = bpf_trampoline_update(tr, true /* lock_direct_mutex */);
if (err) {
hlist_del_init(&link->tramp_hlist);
tr->progs_cnt[kind]--;
}
return err;
}
int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
{
int err;
mutex_lock(&tr->mutex);
err = __bpf_trampoline_link_prog(link, tr);
mutex_unlock(&tr->mutex);
return err;
}
static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
{
enum bpf_tramp_prog_type kind;
int err;
kind = bpf_attach_type_to_tramp(link->link.prog);
if (kind == BPF_TRAMP_REPLACE) {
WARN_ON_ONCE(!tr->extension_prog);
err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
tr->extension_prog->bpf_func, NULL);
tr->extension_prog = NULL;
return err;
}
hlist_del_init(&link->tramp_hlist);
tr->progs_cnt[kind]--;
return bpf_trampoline_update(tr, true /* lock_direct_mutex */);
}
/* bpf_trampoline_unlink_prog() should never fail. */
int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
{
int err;
mutex_lock(&tr->mutex);
err = __bpf_trampoline_unlink_prog(link, tr);
mutex_unlock(&tr->mutex);
return err;
}
#if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM)
static void bpf_shim_tramp_link_release(struct bpf_link *link)
{
struct bpf_shim_tramp_link *shim_link =
container_of(link, struct bpf_shim_tramp_link, link.link);
/* paired with 'shim_link->trampoline = tr' in bpf_trampoline_link_cgroup_shim */
if (!shim_link->trampoline)
return;
WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link, shim_link->trampoline));
bpf_trampoline_put(shim_link->trampoline);
}
static void bpf_shim_tramp_link_dealloc(struct bpf_link *link)
{
struct bpf_shim_tramp_link *shim_link =
container_of(link, struct bpf_shim_tramp_link, link.link);
kfree(shim_link);
}
static const struct bpf_link_ops bpf_shim_tramp_link_lops = {
.release = bpf_shim_tramp_link_release,
.dealloc = bpf_shim_tramp_link_dealloc,
};
static struct bpf_shim_tramp_link *cgroup_shim_alloc(const struct bpf_prog *prog,
bpf_func_t bpf_func,
int cgroup_atype)
{
struct bpf_shim_tramp_link *shim_link = NULL;
struct bpf_prog *p;
shim_link = kzalloc(sizeof(*shim_link), GFP_USER);
if (!shim_link)
return NULL;
p = bpf_prog_alloc(1, 0);
if (!p) {
kfree(shim_link);
return NULL;
}
p->jited = false;
p->bpf_func = bpf_func;
p->aux->cgroup_atype = cgroup_atype;
p->aux->attach_func_proto = prog->aux->attach_func_proto;
p->aux->attach_btf_id = prog->aux->attach_btf_id;
p->aux->attach_btf = prog->aux->attach_btf;
btf_get(p->aux->attach_btf);
p->type = BPF_PROG_TYPE_LSM;
p->expected_attach_type = BPF_LSM_MAC;
bpf_prog_inc(p);
bpf_link_init(&shim_link->link.link, BPF_LINK_TYPE_UNSPEC,
&bpf_shim_tramp_link_lops, p);
bpf_cgroup_atype_get(p->aux->attach_btf_id, cgroup_atype);
return shim_link;
}
static struct bpf_shim_tramp_link *cgroup_shim_find(struct bpf_trampoline *tr,
bpf_func_t bpf_func)
{
struct bpf_tramp_link *link;
int kind;
for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
struct bpf_prog *p = link->link.prog;
if (p->bpf_func == bpf_func)
return container_of(link, struct bpf_shim_tramp_link, link);
}
}
return NULL;
}
int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
int cgroup_atype)
{
struct bpf_shim_tramp_link *shim_link = NULL;
struct bpf_attach_target_info tgt_info = {};
struct bpf_trampoline *tr;
bpf_func_t bpf_func;
u64 key;
int err;
err = bpf_check_attach_target(NULL, prog, NULL,
prog->aux->attach_btf_id,
&tgt_info);
if (err)
return err;
key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
prog->aux->attach_btf_id);
bpf_lsm_find_cgroup_shim(prog, &bpf_func);
tr = bpf_trampoline_get(key, &tgt_info);
if (!tr)
return -ENOMEM;
mutex_lock(&tr->mutex);
shim_link = cgroup_shim_find(tr, bpf_func);
if (shim_link) {
/* Reusing existing shim attached by the other program. */
bpf_link_inc(&shim_link->link.link);
mutex_unlock(&tr->mutex);
bpf_trampoline_put(tr); /* bpf_trampoline_get above */
return 0;
}
/* Allocate and install new shim. */
shim_link = cgroup_shim_alloc(prog, bpf_func, cgroup_atype);
if (!shim_link) {
err = -ENOMEM;
goto err;
}
err = __bpf_trampoline_link_prog(&shim_link->link, tr);
if (err)
goto err;
shim_link->trampoline = tr;
/* note, we're still holding tr refcnt from above */
mutex_unlock(&tr->mutex);
return 0;
err:
mutex_unlock(&tr->mutex);
if (shim_link)
bpf_link_put(&shim_link->link.link);
/* have to release tr while _not_ holding its mutex */
bpf_trampoline_put(tr); /* bpf_trampoline_get above */
return err;
}
void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)
{
struct bpf_shim_tramp_link *shim_link = NULL;
struct bpf_trampoline *tr;
bpf_func_t bpf_func;
u64 key;
key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
prog->aux->attach_btf_id);
bpf_lsm_find_cgroup_shim(prog, &bpf_func);
tr = bpf_trampoline_lookup(key);
if (WARN_ON_ONCE(!tr))
return;
mutex_lock(&tr->mutex);
shim_link = cgroup_shim_find(tr, bpf_func);
mutex_unlock(&tr->mutex);
if (shim_link)
bpf_link_put(&shim_link->link.link);
bpf_trampoline_put(tr); /* bpf_trampoline_lookup above */
}
#endif
struct bpf_trampoline *bpf_trampoline_get(u64 key,
struct bpf_attach_target_info *tgt_info)
{
struct bpf_trampoline *tr;
tr = bpf_trampoline_lookup(key);
if (!tr)
return NULL;
mutex_lock(&tr->mutex);
if (tr->func.addr)
goto out;
memcpy(&tr->func.model, &tgt_info->fmodel, sizeof(tgt_info->fmodel));
tr->func.addr = (void *)tgt_info->tgt_addr;
out:
mutex_unlock(&tr->mutex);
return tr;
}
void bpf_trampoline_put(struct bpf_trampoline *tr)
{
int i;
if (!tr)
return;
mutex_lock(&trampoline_mutex);
if (!refcount_dec_and_test(&tr->refcnt))
goto out;
WARN_ON_ONCE(mutex_is_locked(&tr->mutex));
for (i = 0; i < BPF_TRAMP_MAX; i++)
if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[i])))
goto out;
/* This code will be executed even when the last bpf_tramp_image
* is alive. All progs are detached from the trampoline and the
* trampoline image is patched with jmp into epilogue to skip
* fexit progs. The fentry-only trampoline will be freed via
* multiple rcu callbacks.
*/
hlist_del(&tr->hlist);
if (tr->fops) {
ftrace_free_filter(tr->fops);
kfree(tr->fops);
}
kfree(tr);
out:
mutex_unlock(&trampoline_mutex);
}
#define NO_START_TIME 1
static __always_inline u64 notrace bpf_prog_start_time(void)
{
u64 start = NO_START_TIME;
if (static_branch_unlikely(&bpf_stats_enabled_key)) {
start = sched_clock();
if (unlikely(!start))
start = NO_START_TIME;
}
return start;
}
/* The logic is similar to bpf_prog_run(), but with an explicit
* rcu_read_lock() and migrate_disable() which are required
* for the trampoline. The macro is split into
* call __bpf_prog_enter
* call prog->bpf_func
* call __bpf_prog_exit
*
* __bpf_prog_enter returns:
* 0 - skip execution of the bpf prog
* 1 - execute bpf prog
* [2..MAX_U64] - execute bpf prog and record execution time.
* This is start time.
*/
static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx)
__acquires(RCU)
{
rcu_read_lock();
migrate_disable();
run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
bpf_prog_inc_misses_counter(prog);
return 0;
}
return bpf_prog_start_time();
}
static void notrace update_prog_stats(struct bpf_prog *prog,
u64 start)
{
struct bpf_prog_stats *stats;
if (static_branch_unlikely(&bpf_stats_enabled_key) &&
/* static_key could be enabled in __bpf_prog_enter*
* and disabled in __bpf_prog_exit*.
* And vice versa.
* Hence check that 'start' is valid.
*/
start > NO_START_TIME) {
u64 duration = sched_clock() - start;
unsigned long flags;
stats = this_cpu_ptr(prog->stats);
flags = u64_stats_update_begin_irqsave(&stats->syncp);
u64_stats_inc(&stats->cnt);
u64_stats_add(&stats->nsecs, duration);
u64_stats_update_end_irqrestore(&stats->syncp, flags);
}
}
static void notrace __bpf_prog_exit_recur(struct bpf_prog *prog, u64 start,
struct bpf_tramp_run_ctx *run_ctx)
__releases(RCU)
{
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
update_prog_stats(prog, start);
this_cpu_dec(*(prog->active));
migrate_enable();
rcu_read_unlock();
}
static u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog,
struct bpf_tramp_run_ctx *run_ctx)
__acquires(RCU)
{
/* Runtime stats are exported via actual BPF_LSM_CGROUP
* programs, not the shims.
*/
rcu_read_lock();
migrate_disable();
run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
return NO_START_TIME;
}
static void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start,
struct bpf_tramp_run_ctx *run_ctx)
__releases(RCU)
{
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
migrate_enable();
rcu_read_unlock();
}
u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
struct bpf_tramp_run_ctx *run_ctx)
{
rcu_read_lock_trace();
migrate_disable();
might_fault();
run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
bpf_prog_inc_misses_counter(prog);
return 0;
}
return bpf_prog_start_time();
}
void notrace __bpf_prog_exit_sleepable_recur(struct bpf_prog *prog, u64 start,
struct bpf_tramp_run_ctx *run_ctx)
{
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
update_prog_stats(prog, start);
this_cpu_dec(*(prog->active));
migrate_enable();
rcu_read_unlock_trace();
}
static u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog,
struct bpf_tramp_run_ctx *run_ctx)
{
rcu_read_lock_trace();
migrate_disable();
might_fault();
run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
return bpf_prog_start_time();
}
static void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
struct bpf_tramp_run_ctx *run_ctx)
{
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
update_prog_stats(prog, start);
migrate_enable();
rcu_read_unlock_trace();
}
static u64 notrace __bpf_prog_enter(struct bpf_prog *prog,
struct bpf_tramp_run_ctx *run_ctx)
__acquires(RCU)
{
rcu_read_lock();
migrate_disable();
run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
return bpf_prog_start_time();
}
static void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start,
struct bpf_tramp_run_ctx *run_ctx)
__releases(RCU)
{
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
update_prog_stats(prog, start);
migrate_enable();
rcu_read_unlock();
}
void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr)
{
percpu_ref_get(&tr->pcref);
}
void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)
{
percpu_ref_put(&tr->pcref);
}
bpf_trampoline_enter_t bpf_trampoline_enter(const struct bpf_prog *prog)
{
bool sleepable = prog->sleepable;
if (bpf_prog_check_recur(prog))
return sleepable ? __bpf_prog_enter_sleepable_recur :
__bpf_prog_enter_recur;
if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
prog->expected_attach_type == BPF_LSM_CGROUP)
return __bpf_prog_enter_lsm_cgroup;
return sleepable ? __bpf_prog_enter_sleepable : __bpf_prog_enter;
}
bpf_trampoline_exit_t bpf_trampoline_exit(const struct bpf_prog *prog)
{
bool sleepable = prog->sleepable;
if (bpf_prog_check_recur(prog))
return sleepable ? __bpf_prog_exit_sleepable_recur :
__bpf_prog_exit_recur;
if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
prog->expected_attach_type == BPF_LSM_CGROUP)
return __bpf_prog_exit_lsm_cgroup;
return sleepable ? __bpf_prog_exit_sleepable : __bpf_prog_exit;
}
int __weak
arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image_end,
const struct btf_func_model *m, u32 flags,
struct bpf_tramp_links *tlinks,
void *func_addr)
{
return -ENOTSUPP;
}
void * __weak arch_alloc_bpf_trampoline(unsigned int size)
{
void *image;
if (WARN_ON_ONCE(size > PAGE_SIZE))
return NULL;
image = bpf_jit_alloc_exec(PAGE_SIZE);
if (image)
set_vm_flush_reset_perms(image);
return image;
}
void __weak arch_free_bpf_trampoline(void *image, unsigned int size)
{
WARN_ON_ONCE(size > PAGE_SIZE);
/* bpf_jit_free_exec doesn't need "size", but
* bpf_prog_pack_free() needs it.
*/
bpf_jit_free_exec(image);
}
int __weak arch_protect_bpf_trampoline(void *image, unsigned int size)
{
WARN_ON_ONCE(size > PAGE_SIZE);
return set_memory_rox((long)image, 1);
}
int __weak arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
struct bpf_tramp_links *tlinks, void *func_addr)
{
return -ENOTSUPP;
}
static int __init init_trampolines(void)
{
int i;
for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++)
INIT_HLIST_HEAD(&trampoline_table[i]);
return 0;
}
late_initcall(init_trampolines);
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