// SPDX-License-Identifier: GPL-2.0-only
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/* Copyright (c) 2019 Facebook */
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#include <linux/hash.h>
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#include <linux/bpf.h>
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#include <linux/filter.h>
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#include <linux/ftrace.h>
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#include <linux/rbtree_latch.h>
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#include <linux/perf_event.h>
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#include <linux/btf.h>
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#include <linux/rcupdate_trace.h>
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#include <linux/rcupdate_wait.h>
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#include <trace/hooks/memory.h>
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/* dummy _ops. The verifier will operate on target program's ops. */
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const struct bpf_verifier_ops bpf_extension_verifier_ops = {
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};
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const struct bpf_prog_ops bpf_extension_prog_ops = {
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};
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/* btf_vmlinux has ~22k attachable functions. 1k htab is enough. */
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#define TRAMPOLINE_HASH_BITS 10
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#define TRAMPOLINE_TABLE_SIZE (1 << TRAMPOLINE_HASH_BITS)
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static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE];
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/* serializes access to trampoline_table */
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static DEFINE_MUTEX(trampoline_mutex);
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void *bpf_jit_alloc_exec_page(void)
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{
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void *image;
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image = bpf_jit_alloc_exec(PAGE_SIZE);
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if (!image)
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return NULL;
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set_vm_flush_reset_perms(image);
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/* Keep image as writeable. The alternative is to keep flipping ro/rw
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* everytime new program is attached or detached.
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*/
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set_memory_x((long)image, 1);
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trace_android_vh_set_memory_x((unsigned long)image, 1);
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return image;
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}
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void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym)
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{
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ksym->start = (unsigned long) data;
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ksym->end = ksym->start + PAGE_SIZE;
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bpf_ksym_add(ksym);
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perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
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PAGE_SIZE, false, ksym->name);
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}
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void bpf_image_ksym_del(struct bpf_ksym *ksym)
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{
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bpf_ksym_del(ksym);
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perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
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PAGE_SIZE, true, ksym->name);
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}
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static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
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{
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struct bpf_trampoline *tr;
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struct hlist_head *head;
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int i;
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mutex_lock(&trampoline_mutex);
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head = &trampoline_table[hash_64(key, TRAMPOLINE_HASH_BITS)];
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hlist_for_each_entry(tr, head, hlist) {
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if (tr->key == key) {
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refcount_inc(&tr->refcnt);
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goto out;
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}
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}
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tr = kzalloc(sizeof(*tr), GFP_KERNEL);
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if (!tr)
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goto out;
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tr->key = key;
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INIT_HLIST_NODE(&tr->hlist);
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hlist_add_head(&tr->hlist, head);
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refcount_set(&tr->refcnt, 1);
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mutex_init(&tr->mutex);
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for (i = 0; i < BPF_TRAMP_MAX; i++)
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INIT_HLIST_HEAD(&tr->progs_hlist[i]);
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out:
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mutex_unlock(&trampoline_mutex);
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return tr;
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}
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static int is_ftrace_location(void *ip)
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{
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long addr;
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addr = ftrace_location((long)ip);
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if (!addr)
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return 0;
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if (WARN_ON_ONCE(addr != (long)ip))
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return -EFAULT;
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return 1;
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}
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static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
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{
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void *ip = tr->func.addr;
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int ret;
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if (tr->func.ftrace_managed)
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ret = unregister_ftrace_direct((long)ip, (long)old_addr);
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else
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ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
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return ret;
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}
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static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr)
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{
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void *ip = tr->func.addr;
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int ret;
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if (tr->func.ftrace_managed)
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ret = modify_ftrace_direct((long)ip, (long)old_addr, (long)new_addr);
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else
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ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr);
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return ret;
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}
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/* first time registering */
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static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
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{
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void *ip = tr->func.addr;
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int ret;
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ret = is_ftrace_location(ip);
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if (ret < 0)
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return ret;
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tr->func.ftrace_managed = ret;
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if (tr->func.ftrace_managed)
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ret = register_ftrace_direct((long)ip, (long)new_addr);
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else
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ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
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return ret;
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}
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static struct bpf_tramp_progs *
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bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total)
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{
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const struct bpf_prog_aux *aux;
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struct bpf_tramp_progs *tprogs;
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struct bpf_prog **progs;
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int kind;
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*total = 0;
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tprogs = kcalloc(BPF_TRAMP_MAX, sizeof(*tprogs), GFP_KERNEL);
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if (!tprogs)
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return ERR_PTR(-ENOMEM);
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for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
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tprogs[kind].nr_progs = tr->progs_cnt[kind];
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*total += tr->progs_cnt[kind];
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progs = tprogs[kind].progs;
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hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist)
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*progs++ = aux->prog;
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}
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return tprogs;
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}
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static void __bpf_tramp_image_put_deferred(struct work_struct *work)
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{
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struct bpf_tramp_image *im;
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im = container_of(work, struct bpf_tramp_image, work);
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bpf_image_ksym_del(&im->ksym);
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trace_android_vh_set_memory_nx((unsigned long)im->image, 1);
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bpf_jit_free_exec(im->image);
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bpf_jit_uncharge_modmem(1);
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percpu_ref_exit(&im->pcref);
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kfree_rcu(im, rcu);
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}
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/* callback, fexit step 3 or fentry step 2 */
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static void __bpf_tramp_image_put_rcu(struct rcu_head *rcu)
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{
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struct bpf_tramp_image *im;
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im = container_of(rcu, struct bpf_tramp_image, rcu);
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INIT_WORK(&im->work, __bpf_tramp_image_put_deferred);
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schedule_work(&im->work);
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}
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/* callback, fexit step 2. Called after percpu_ref_kill confirms. */
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static void __bpf_tramp_image_release(struct percpu_ref *pcref)
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{
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struct bpf_tramp_image *im;
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im = container_of(pcref, struct bpf_tramp_image, pcref);
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call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
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}
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/* callback, fexit or fentry step 1 */
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static void __bpf_tramp_image_put_rcu_tasks(struct rcu_head *rcu)
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{
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struct bpf_tramp_image *im;
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im = container_of(rcu, struct bpf_tramp_image, rcu);
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if (im->ip_after_call)
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/* the case of fmod_ret/fexit trampoline and CONFIG_PREEMPTION=y */
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percpu_ref_kill(&im->pcref);
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else
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/* the case of fentry trampoline */
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call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
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}
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static void bpf_tramp_image_put(struct bpf_tramp_image *im)
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{
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/* The trampoline image that calls original function is using:
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* rcu_read_lock_trace to protect sleepable bpf progs
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* rcu_read_lock to protect normal bpf progs
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* percpu_ref to protect trampoline itself
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* rcu tasks to protect trampoline asm not covered by percpu_ref
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* (which are few asm insns before __bpf_tramp_enter and
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* after __bpf_tramp_exit)
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*
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* The trampoline is unreachable before bpf_tramp_image_put().
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*
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* First, patch the trampoline to avoid calling into fexit progs.
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* The progs will be freed even if the original function is still
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* executing or sleeping.
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* In case of CONFIG_PREEMPT=y use call_rcu_tasks() to wait on
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* first few asm instructions to execute and call into
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* __bpf_tramp_enter->percpu_ref_get.
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* Then use percpu_ref_kill to wait for the trampoline and the original
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* function to finish.
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* Then use call_rcu_tasks() to make sure few asm insns in
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* the trampoline epilogue are done as well.
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*
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* In !PREEMPT case the task that got interrupted in the first asm
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* insns won't go through an RCU quiescent state which the
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* percpu_ref_kill will be waiting for. Hence the first
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* call_rcu_tasks() is not necessary.
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*/
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if (im->ip_after_call) {
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int err = bpf_arch_text_poke(im->ip_after_call, BPF_MOD_JUMP,
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NULL, im->ip_epilogue);
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WARN_ON(err);
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if (IS_ENABLED(CONFIG_PREEMPTION))
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call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
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else
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percpu_ref_kill(&im->pcref);
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return;
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}
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/* The trampoline without fexit and fmod_ret progs doesn't call original
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* function and doesn't use percpu_ref.
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* Use call_rcu_tasks_trace() to wait for sleepable progs to finish.
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* Then use call_rcu_tasks() to wait for the rest of trampoline asm
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* and normal progs.
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*/
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call_rcu_tasks_trace(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
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}
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static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
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{
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struct bpf_tramp_image *im;
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struct bpf_ksym *ksym;
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void *image;
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int err = -ENOMEM;
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im = kzalloc(sizeof(*im), GFP_KERNEL);
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if (!im)
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goto out;
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err = bpf_jit_charge_modmem(1);
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if (err)
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goto out_free_im;
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err = -ENOMEM;
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im->image = image = bpf_jit_alloc_exec_page();
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if (!image)
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goto out_uncharge;
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err = percpu_ref_init(&im->pcref, __bpf_tramp_image_release, 0, GFP_KERNEL);
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if (err)
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goto out_free_image;
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ksym = &im->ksym;
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INIT_LIST_HEAD_RCU(&ksym->lnode);
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snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu_%u", key, idx);
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bpf_image_ksym_add(image, ksym);
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return im;
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out_free_image:
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bpf_jit_free_exec(im->image);
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out_uncharge:
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bpf_jit_uncharge_modmem(1);
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out_free_im:
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kfree(im);
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out:
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return ERR_PTR(err);
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}
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static int bpf_trampoline_update(struct bpf_trampoline *tr)
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{
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struct bpf_tramp_image *im;
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struct bpf_tramp_progs *tprogs;
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u32 flags = BPF_TRAMP_F_RESTORE_REGS;
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int err, total;
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tprogs = bpf_trampoline_get_progs(tr, &total);
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if (IS_ERR(tprogs))
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return PTR_ERR(tprogs);
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if (total == 0) {
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err = unregister_fentry(tr, tr->cur_image->image);
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bpf_tramp_image_put(tr->cur_image);
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tr->cur_image = NULL;
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tr->selector = 0;
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goto out;
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}
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im = bpf_tramp_image_alloc(tr->key, tr->selector);
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if (IS_ERR(im)) {
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err = PTR_ERR(im);
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goto out;
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}
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if (tprogs[BPF_TRAMP_FEXIT].nr_progs ||
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tprogs[BPF_TRAMP_MODIFY_RETURN].nr_progs)
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flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
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err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,
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&tr->func.model, flags, tprogs,
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tr->func.addr);
|
if (err < 0)
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goto out;
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WARN_ON(tr->cur_image && tr->selector == 0);
|
WARN_ON(!tr->cur_image && tr->selector);
|
if (tr->cur_image)
|
/* progs already running at this address */
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err = modify_fentry(tr, tr->cur_image->image, im->image);
|
else
|
/* first time registering */
|
err = register_fentry(tr, im->image);
|
if (err)
|
goto out;
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if (tr->cur_image)
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bpf_tramp_image_put(tr->cur_image);
|
tr->cur_image = im;
|
tr->selector++;
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out:
|
kfree(tprogs);
|
return err;
|
}
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static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
|
{
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switch (prog->expected_attach_type) {
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case BPF_TRACE_FENTRY:
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return BPF_TRAMP_FENTRY;
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case BPF_MODIFY_RETURN:
|
return BPF_TRAMP_MODIFY_RETURN;
|
case BPF_TRACE_FEXIT:
|
return BPF_TRAMP_FEXIT;
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case BPF_LSM_MAC:
|
if (!prog->aux->attach_func_proto->type)
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/* The function returns void, we cannot modify its
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* return value.
|
*/
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return BPF_TRAMP_FEXIT;
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else
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return BPF_TRAMP_MODIFY_RETURN;
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default:
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return BPF_TRAMP_REPLACE;
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}
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}
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int bpf_trampoline_link_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
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{
|
enum bpf_tramp_prog_type kind;
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int err = 0;
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int cnt = 0, i;
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kind = bpf_attach_type_to_tramp(prog);
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mutex_lock(&tr->mutex);
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if (tr->extension_prog) {
|
/* cannot attach fentry/fexit if extension prog is attached.
|
* cannot overwrite extension prog either.
|
*/
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err = -EBUSY;
|
goto out;
|
}
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|
for (i = 0; i < BPF_TRAMP_MAX; i++)
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cnt += tr->progs_cnt[i];
|
|
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(tr);
|
if (err) {
|
hlist_del(&prog->aux->tramp_hlist);
|
tr->progs_cnt[kind]--;
|
}
|
out:
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mutex_unlock(&tr->mutex);
|
return err;
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}
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|
/* bpf_trampoline_unlink_prog() should never fail. */
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int bpf_trampoline_unlink_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
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{
|
enum bpf_tramp_prog_type kind;
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int err;
|
|
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(tr);
|
out:
|
mutex_unlock(&tr->mutex);
|
return err;
|
}
|
|
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);
|
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();
|
}
|
|
void notrace __bpf_prog_enter_sleepable(void)
|
{
|
rcu_read_lock_trace();
|
might_fault();
|
}
|
|
void notrace __bpf_prog_exit_sleepable(void)
|
{
|
rcu_read_unlock_trace();
|
}
|
|
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);
|
}
|
|
int __weak
|
arch_prepare_bpf_trampoline(struct bpf_tramp_image *tr, 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);
|
