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c561d11063
Add leading space to spdx tag Use // for spdx c file comment Replacements resereved to reserved inbetween to in between everytime to every time intutivie to intuitive currenct to current encontered to encountered referenceing to referencing upto to up to exectuted to executed Signed-off-by: Tom Rix <trix@redhat.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20220220184055.3608317-1-trix@redhat.com
665 lines
16 KiB
C
665 lines
16 KiB
C
// 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 <linux/module.h>
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#include <linux/static_call.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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bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
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{
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enum bpf_attach_type eatype = prog->expected_attach_type;
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return eatype == BPF_TRACE_FENTRY || eatype == BPF_TRACE_FEXIT ||
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eatype == BPF_MODIFY_RETURN;
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}
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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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* every time new program is attached or detached.
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*/
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set_memory_x((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 bpf_trampoline_module_get(struct bpf_trampoline *tr)
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{
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struct module *mod;
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int err = 0;
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preempt_disable();
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mod = __module_text_address((unsigned long) tr->func.addr);
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if (mod && !try_module_get(mod))
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err = -ENOENT;
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preempt_enable();
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tr->mod = mod;
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return err;
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}
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static void bpf_trampoline_module_put(struct bpf_trampoline *tr)
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{
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module_put(tr->mod);
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tr->mod = NULL;
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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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if (!ret)
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bpf_trampoline_module_put(tr);
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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 (bpf_trampoline_module_get(tr))
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return -ENOENT;
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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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if (ret)
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bpf_trampoline_module_put(tr);
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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, bool *ip_arg)
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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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*ip_arg |= aux->prog->call_get_func_ip;
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*progs++ = aux->prog;
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}
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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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bpf_jit_free_exec(im->image);
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bpf_jit_uncharge_modmem(PAGE_SIZE);
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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(PAGE_SIZE);
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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(PAGE_SIZE);
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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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bool ip_arg = false;
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int err, total;
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tprogs = bpf_trampoline_get_progs(tr, &total, &ip_arg);
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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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if (ip_arg)
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flags |= BPF_TRAMP_F_IP_ARG;
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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);
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if (err < 0)
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goto out;
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WARN_ON(tr->cur_image && tr->selector == 0);
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WARN_ON(!tr->cur_image && tr->selector);
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if (tr->cur_image)
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/* progs already running at this address */
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err = modify_fentry(tr, tr->cur_image->image, im->image);
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else
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/* first time registering */
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err = register_fentry(tr, im->image);
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if (err)
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goto out;
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if (tr->cur_image)
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bpf_tramp_image_put(tr->cur_image);
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tr->cur_image = im;
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tr->selector++;
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out:
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kfree(tprogs);
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return err;
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}
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static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
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{
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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:
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return BPF_TRAMP_MODIFY_RETURN;
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case BPF_TRACE_FEXIT:
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return BPF_TRAMP_FEXIT;
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case BPF_LSM_MAC:
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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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*/
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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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{
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enum bpf_tramp_prog_type kind;
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int err = 0;
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int cnt;
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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) {
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/* cannot attach fentry/fexit if extension prog is attached.
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* cannot overwrite extension prog either.
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*/
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err = -EBUSY;
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goto out;
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}
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cnt = tr->progs_cnt[BPF_TRAMP_FENTRY] + tr->progs_cnt[BPF_TRAMP_FEXIT];
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if (kind == BPF_TRAMP_REPLACE) {
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/* Cannot attach extension if fentry/fexit are in use. */
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if (cnt) {
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err = -EBUSY;
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goto out;
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}
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tr->extension_prog = prog;
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err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
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prog->bpf_func);
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goto out;
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}
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if (cnt >= BPF_MAX_TRAMP_PROGS) {
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err = -E2BIG;
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goto out;
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}
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if (!hlist_unhashed(&prog->aux->tramp_hlist)) {
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/* prog already linked */
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err = -EBUSY;
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goto out;
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}
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hlist_add_head(&prog->aux->tramp_hlist, &tr->progs_hlist[kind]);
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tr->progs_cnt[kind]++;
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err = bpf_trampoline_update(tr);
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if (err) {
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hlist_del_init(&prog->aux->tramp_hlist);
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tr->progs_cnt[kind]--;
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}
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out:
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mutex_unlock(&tr->mutex);
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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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{
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enum bpf_tramp_prog_type kind;
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int err;
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kind = bpf_attach_type_to_tramp(prog);
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mutex_lock(&tr->mutex);
|
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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_init(&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)
|
|
{
|
|
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;
|
|
/* 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);
|
|
}
|
|
|
|
#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;
|
|
}
|
|
|
|
static void notrace inc_misses_counter(struct bpf_prog *prog)
|
|
{
|
|
struct bpf_prog_stats *stats;
|
|
unsigned int flags;
|
|
|
|
stats = this_cpu_ptr(prog->stats);
|
|
flags = u64_stats_update_begin_irqsave(&stats->syncp);
|
|
u64_stats_inc(&stats->misses);
|
|
u64_stats_update_end_irqrestore(&stats->syncp, flags);
|
|
}
|
|
|
|
/* 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.
|
|
*/
|
|
u64 notrace __bpf_prog_enter(struct bpf_prog *prog)
|
|
__acquires(RCU)
|
|
{
|
|
rcu_read_lock();
|
|
migrate_disable();
|
|
if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
|
|
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) {
|
|
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, sched_clock() - start);
|
|
u64_stats_update_end_irqrestore(&stats->syncp, flags);
|
|
}
|
|
}
|
|
|
|
void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start)
|
|
__releases(RCU)
|
|
{
|
|
update_prog_stats(prog, start);
|
|
__this_cpu_dec(*(prog->active));
|
|
migrate_enable();
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog)
|
|
{
|
|
rcu_read_lock_trace();
|
|
migrate_disable();
|
|
might_fault();
|
|
if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
|
|
inc_misses_counter(prog);
|
|
return 0;
|
|
}
|
|
return bpf_prog_start_time();
|
|
}
|
|
|
|
void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start)
|
|
{
|
|
update_prog_stats(prog, start);
|
|
__this_cpu_dec(*(prog->active));
|
|
migrate_enable();
|
|
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);
|