// 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> /* 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); void *bpf_jit_alloc_exec_page(void){	void *image; 	image = bpf_jit_alloc_exec(PAGE_SIZE);	if (!image)		return NULL; 	set_vm_flush_reset_perms(image);	/* Keep image as writeable. The alternative is to keep flipping ro/rw	 * everytime new program is attached or detached.	 */	set_memory_x((long)image, 1);	return image;} void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym){	ksym->start = (unsigned long) data;	ksym->end = ksym->start + PAGE_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 void bpf_trampoline_ksym_add(struct bpf_trampoline *tr){	struct bpf_ksym *ksym = &tr->ksym; 	snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu", tr->key);	bpf_image_ksym_add(tr->image, ksym);} struct bpf_trampoline *bpf_trampoline_lookup(u64 key){	struct bpf_trampoline *tr;	struct hlist_head *head;	void *image;	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; 	/* is_root was checked earlier. No need for bpf_jit_charge_modmem() */	image = bpf_jit_alloc_exec_page();	if (!image) {		kfree(tr);		tr = NULL;		goto out;	} 	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]);	tr->image = image;	INIT_LIST_HEAD_RCU(&tr->ksym.lnode);	bpf_trampoline_ksym_add(tr);out:	mutex_unlock(&trampoline_mutex);	return tr;} static int is_ftrace_location(void *ip){	long addr; 	addr = ftrace_location((long)ip);	if (!addr)		return 0;	if (WARN_ON_ONCE(addr != (long)ip))		return -EFAULT;	return 1;} 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((long)ip, (long)old_addr);	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){	void *ip = tr->func.addr;	int ret; 	if (tr->func.ftrace_managed)		ret = modify_ftrace_direct((long)ip, (long)old_addr, (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;	int ret; 	ret = is_ftrace_location(ip);	if (ret < 0)		return ret;	tr->func.ftrace_managed = ret; 	if (tr->func.ftrace_managed)		ret = register_ftrace_direct((long)ip, (long)new_addr);	else		ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);	return ret;} static struct bpf_tramp_progs *bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total){	const struct bpf_prog_aux *aux;	struct bpf_tramp_progs *tprogs;	struct bpf_prog **progs;	int kind; 	*total = 0;	tprogs = kcalloc(BPF_TRAMP_MAX, sizeof(*tprogs), GFP_KERNEL);	if (!tprogs)		return ERR_PTR(-ENOMEM); 	for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {		tprogs[kind].nr_progs = tr->progs_cnt[kind];		*total += tr->progs_cnt[kind];		progs = tprogs[kind].progs; 		hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist)			*progs++ = aux->prog;	}	return tprogs;} static int bpf_trampoline_update(struct bpf_trampoline *tr){	void *old_image = tr->image + ((tr->selector + 1) & 1) * PAGE_SIZE/2;	void *new_image = tr->image + (tr->selector & 1) * PAGE_SIZE/2;	struct bpf_tramp_progs *tprogs;	u32 flags = BPF_TRAMP_F_RESTORE_REGS;	int err, total; 	tprogs = bpf_trampoline_get_progs(tr, &total);	if (IS_ERR(tprogs))		return PTR_ERR(tprogs); 	if (total == 0) {		err = unregister_fentry(tr, old_image);		tr->selector = 0;		goto out;	} 	if (tprogs[BPF_TRAMP_FEXIT].nr_progs ||	    tprogs[BPF_TRAMP_MODIFY_RETURN].nr_progs)		flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME; 	/* Though the second half of trampoline page is unused a task could be	 * preempted in the middle of the first half of trampoline and two	 * updates to trampoline would change the code from underneath the	 * preempted task. Hence wait for tasks to voluntarily schedule or go	 * to userspace.	 */ 	synchronize_rcu_tasks(); 	err = arch_prepare_bpf_trampoline(new_image, new_image + PAGE_SIZE / 2,					  &tr->func.model, flags, tprogs,					  tr->func.addr);	if (err < 0)		goto out; 	if (tr->selector)		/* progs already running at this address */		err = modify_fentry(tr, old_image, new_image);	else		/* first time registering */		err = register_fentry(tr, new_image);	if (err)		goto out;	tr->selector++;out:	kfree(tprogs);	return err;} 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;	}} int bpf_trampoline_link_prog(struct bpf_prog *prog){	enum bpf_tramp_prog_type kind;	struct bpf_trampoline *tr;	int err = 0;	int cnt; 	tr = prog->aux->trampoline;	kind = bpf_attach_type_to_tramp(prog);	mutex_lock(&tr->mutex);	if (tr->extension_prog) {		/* cannot attach fentry/fexit if extension prog is attached.		 * cannot overwrite extension prog either.		 */		err = -EBUSY;		goto out;	}	cnt = tr->progs_cnt[BPF_TRAMP_FENTRY] + tr->progs_cnt[BPF_TRAMP_FEXIT];	if (kind == BPF_TRAMP_REPLACE) {		/* Cannot attach extension if fentry/fexit are in use. */		if (cnt) {			err = -EBUSY;			goto out;		}		tr->extension_prog = prog;		err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,					 prog->bpf_func);		goto out;	}	if (cnt >= BPF_MAX_TRAMP_PROGS) {		err = -E2BIG;		goto out;	}	if (!hlist_unhashed(&prog->aux->tramp_hlist)) {		/* prog already linked */		err = -EBUSY;		goto out;	}	hlist_add_head(&prog->aux->tramp_hlist, &tr->progs_hlist[kind]);	tr->progs_cnt[kind]++;	err = bpf_trampoline_update(prog->aux->trampoline);	if (err) {		hlist_del(&prog->aux->tramp_hlist);		tr->progs_cnt[kind]--;	}out:	mutex_unlock(&tr->mutex);	return err;} /* bpf_trampoline_unlink_prog() should never fail. */int bpf_trampoline_unlink_prog(struct bpf_prog *prog){	enum bpf_tramp_prog_type kind;	struct bpf_trampoline *tr;	int err; 	tr = prog->aux->trampoline;	kind = bpf_attach_type_to_tramp(prog);	mutex_lock(&tr->mutex);	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;		goto out;	}	hlist_del(&prog->aux->tramp_hlist);	tr->progs_cnt[kind]--;	err = bpf_trampoline_update(prog->aux->trampoline);out:	mutex_unlock(&tr->mutex);	return err;} void bpf_trampoline_put(struct bpf_trampoline *tr){	if (!tr)		return;	mutex_lock(&trampoline_mutex);	if (!refcount_dec_and_test(&tr->refcnt))		goto out;	WARN_ON_ONCE(mutex_is_locked(&tr->mutex));	if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[BPF_TRAMP_FENTRY])))		goto out;	if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[BPF_TRAMP_FEXIT])))		goto out;	bpf_image_ksym_del(&tr->ksym);	/* wait for tasks to get out of trampoline before freeing it */	synchronize_rcu_tasks();	bpf_jit_free_exec(tr->image);	hlist_del(&tr->hlist);	kfree(tr);out:	mutex_unlock(&trampoline_mutex);} /* 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 */u64 notrace __bpf_prog_enter(void)	__acquires(RCU){	u64 start = 0; 	rcu_read_lock();	migrate_disable();	if (static_branch_unlikely(&bpf_stats_enabled_key))		start = sched_clock();	return start;} void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start)	__releases(RCU){	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 not zero.	     */	    start) {		stats = this_cpu_ptr(prog->aux->stats);		u64_stats_update_begin(&stats->syncp);		stats->cnt++;		stats->nsecs += sched_clock() - start;		u64_stats_update_end(&stats->syncp);	}	migrate_enable();	rcu_read_unlock();} int __weakarch_prepare_bpf_trampoline(void *image, void *image_end,			    const struct btf_func_model *m, u32 flags,			    struct bpf_tramp_progs *tprogs,			    void *orig_call){	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);