accel/amdxdna: use modern PM helpers

[drm/drm-misc.git] / kernel / bpf / trampoline.c

// 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_init(void *data, unsigned int size, struct bpf_ksym *ksym)
{
        ksym->start = (unsigned long) data;
        ksym->end = ksym->start + size;
}

void bpf_image_ksym_add(struct bpf_ksym *ksym)
{
        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_init(image, size, ksym);
        bpf_image_ksym_add(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_freplace_check_tgt_prog(struct bpf_prog *tgt_prog)
{
        struct bpf_prog_aux *aux = tgt_prog->aux;

        guard(mutex)(&aux->ext_mutex);
        if (aux->prog_array_member_cnt)
                /* Program extensions can not extend target prog when the target
                 * prog has been updated to any prog_array map as tail callee.
                 * It's to prevent a potential infinite loop like:
                 * tgt prog entry -> tgt prog subprog -> freplace prog entry
                 * --tailcall-> tgt prog entry.
                 */
                return -EBUSY;

        aux->is_extended = true;
        return 0;
}

static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link,
                                      struct bpf_trampoline *tr,
                                      struct bpf_prog *tgt_prog)
{
        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;
                err = bpf_freplace_check_tgt_prog(tgt_prog);
                if (err)
                        return err;
                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,
                             struct bpf_prog *tgt_prog)
{
        int err;

        mutex_lock(&tr->mutex);
        err = __bpf_trampoline_link_prog(link, tr, tgt_prog);
        mutex_unlock(&tr->mutex);
        return err;
}

static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link,
                                        struct bpf_trampoline *tr,
                                        struct bpf_prog *tgt_prog)
{
        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;
                guard(mutex)(&tgt_prog->aux->ext_mutex);
                tgt_prog->aux->is_extended = false;
                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,
                               struct bpf_prog *tgt_prog)
{
        int err;

        mutex_lock(&tr->mutex);
        err = __bpf_trampoline_unlink_prog(link, tr, tgt_prog);
        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, NULL));
        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, NULL);
        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);
                if (prog->aux->recursion_detected)
                        prog->aux->recursion_detected(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);
                if (prog->aux->recursion_detected)
                        prog->aux->recursion_detected(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);