summaryrefslogtreecommitdiffstats
path: root/kernel/bpf/trampoline.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/bpf/trampoline.c')
-rw-r--r--kernel/bpf/trampoline.c1080
1 files changed, 1080 insertions, 0 deletions
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
new file mode 100644
index 000000000..748ac8616
--- /dev/null
+++ b/kernel/bpf/trampoline.c
@@ -0,0 +1,1080 @@
+// 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/module.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_multi(). Then we can
+ * retry register_ftrace_direct_multi() after updating the
+ * trampoline.
+ */
+ if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
+ !(tr->flags & BPF_TRAMP_F_ORIG_STACK)) {
+ if (WARN_ON_ONCE(tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY))
+ return -EBUSY;
+
+ tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
+ return -EAGAIN;
+ }
+
+ return 0;
+ }
+
+ /* The normal locking order is
+ * tr->mutex => direct_mutex (ftrace.c) => ftrace_lock (ftrace.c)
+ *
+ * The following two commands are called from
+ *
+ * prepare_direct_functions_for_ipmodify
+ * cleanup_direct_functions_after_ipmodify
+ *
+ * In both cases, direct_mutex is already locked. Use
+ * mutex_trylock(&tr->mutex) to avoid deadlock in race condition
+ * (something else is making changes to this same trampoline).
+ */
+ if (!mutex_trylock(&tr->mutex)) {
+ /* sleep 1 ms to make sure whatever holding tr->mutex makes
+ * some progress.
+ */
+ msleep(1);
+ return -EAGAIN;
+ }
+
+ switch (cmd) {
+ case FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER:
+ tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
+
+ if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
+ !(tr->flags & BPF_TRAMP_F_ORIG_STACK))
+ ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
+ break;
+ case FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER:
+ tr->flags &= ~BPF_TRAMP_F_SHARE_IPMODIFY;
+
+ if (tr->flags & BPF_TRAMP_F_ORIG_STACK)
+ ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ mutex_unlock(&tr->mutex);
+ return ret;
+}
+#endif
+
+bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
+{
+ enum bpf_attach_type eatype = prog->expected_attach_type;
+ enum bpf_prog_type ptype = prog->type;
+
+ return (ptype == BPF_PROG_TYPE_TRACING &&
+ (eatype == BPF_TRACE_FENTRY || eatype == BPF_TRACE_FEXIT ||
+ eatype == BPF_MODIFY_RETURN)) ||
+ (ptype == BPF_PROG_TYPE_LSM && eatype == BPF_LSM_MAC);
+}
+
+void bpf_image_ksym_add(void *data, 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 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 bpf_trampoline_module_get(struct bpf_trampoline *tr)
+{
+ struct module *mod;
+ int err = 0;
+
+ preempt_disable();
+ mod = __module_text_address((unsigned long) tr->func.addr);
+ if (mod && !try_module_get(mod))
+ err = -ENOENT;
+ preempt_enable();
+ tr->mod = mod;
+ return err;
+}
+
+static void bpf_trampoline_module_put(struct bpf_trampoline *tr)
+{
+ module_put(tr->mod);
+ tr->mod = NULL;
+}
+
+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_multi(tr->fops, (long)old_addr);
+ else
+ ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
+
+ if (!ret)
+ bpf_trampoline_module_put(tr);
+ 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_multi(tr->fops, (long)new_addr);
+ else
+ ret = modify_ftrace_direct_multi_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 (bpf_trampoline_module_get(tr))
+ return -ENOENT;
+
+ if (tr->func.ftrace_managed) {
+ ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 1);
+ ret = register_ftrace_direct_multi(tr->fops, (long)new_addr);
+ } else {
+ ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
+ }
+
+ if (ret)
+ bpf_trampoline_module_put(tr);
+ 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);
+ bpf_jit_free_exec(im->image);
+ bpf_jit_uncharge_modmem(PAGE_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_PREEMPTION))
+ 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)
+{
+ 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(PAGE_SIZE);
+ if (err)
+ goto out_free_im;
+
+ err = -ENOMEM;
+ im->image = image = bpf_jit_alloc_exec(PAGE_SIZE);
+ if (!image)
+ goto out_uncharge;
+ set_vm_flush_reset_perms(image);
+
+ err = percpu_ref_init(&im->pcref, __bpf_tramp_image_release, 0, GFP_KERNEL);
+ if (err)
+ goto out_free_image;
+
+ ksym = &im->ksym;
+ INIT_LIST_HEAD_RCU(&ksym->lnode);
+ snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu", key);
+ bpf_image_ksym_add(image, ksym);
+ return im;
+
+out_free_image:
+ bpf_jit_free_exec(im->image);
+out_uncharge:
+ bpf_jit_uncharge_modmem(PAGE_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;
+
+ 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;
+ }
+
+ im = bpf_tramp_image_alloc(tr->key);
+ if (IS_ERR(im)) {
+ err = PTR_ERR(im);
+ 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
+
+ err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,
+ &tr->func.model, tr->flags, tlinks,
+ tr->func.addr);
+ if (err < 0)
+ goto out_free;
+
+ set_memory_ro((long)im->image, 1);
+ set_memory_x((long)im->image, 1);
+
+ 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;
+
+ /* reset im->image memory attr for arch_prepare_bpf_trampoline */
+ set_memory_nx((long)im->image, 1);
+ set_memory_rw((long)im->image, 1);
+ goto again;
+ }
+#endif
+ if (err)
+ goto out_free;
+
+ if (tr->cur_image)
+ bpf_tramp_image_put(tr->cur_image);
+ tr->cur_image = im;
+out:
+ /* If any error happens, restore previous flags */
+ if (err)
+ tr->flags = orig_flags;
+ kfree(tlinks);
+ return err;
+
+out_free:
+ bpf_tramp_image_free(im);
+ goto out;
+}
+
+static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
+{
+ switch (prog->expected_attach_type) {
+ case BPF_TRACE_FENTRY:
+ return BPF_TRAMP_FENTRY;
+ case BPF_MODIFY_RETURN:
+ return BPF_TRAMP_MODIFY_RETURN;
+ case BPF_TRACE_FEXIT:
+ return BPF_TRAMP_FEXIT;
+ case BPF_LSM_MAC:
+ if (!prog->aux->attach_func_proto->type)
+ /* The function returns void, we cannot modify its
+ * return value.
+ */
+ return BPF_TRAMP_FEXIT;
+ else
+ return BPF_TRAMP_MODIFY_RETURN;
+ default:
+ return BPF_TRAMP_REPLACE;
+ }
+}
+
+static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
+{
+ enum bpf_tramp_prog_type kind;
+ struct bpf_tramp_link *link_exiting;
+ int err = 0;
+ int cnt = 0, i;
+
+ kind = bpf_attach_type_to_tramp(link->link.prog);
+ if (tr->extension_prog)
+ /* cannot attach fentry/fexit if extension prog is attached.
+ * cannot overwrite extension prog either.
+ */
+ return -EBUSY;
+
+ for (i = 0; i < BPF_TRAMP_MAX; i++)
+ cnt += tr->progs_cnt[i];
+
+ if (kind == BPF_TRAMP_REPLACE) {
+ /* Cannot attach extension if fentry/fexit are in use. */
+ if (cnt)
+ return -EBUSY;
+ tr->extension_prog = link->link.prog;
+ return bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
+ link->link.prog->bpf_func);
+ }
+ if (cnt >= BPF_MAX_TRAMP_LINKS)
+ return -E2BIG;
+ if (!hlist_unhashed(&link->tramp_hlist))
+ /* prog already linked */
+ return -EBUSY;
+ hlist_for_each_entry(link_exiting, &tr->progs_hlist[kind], tramp_hlist) {
+ if (link_exiting->link.prog != link->link.prog)
+ continue;
+ /* prog already linked */
+ return -EBUSY;
+ }
+
+ hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]);
+ tr->progs_cnt[kind]++;
+ err = bpf_trampoline_update(tr, true /* lock_direct_mutex */);
+ if (err) {
+ hlist_del_init(&link->tramp_hlist);
+ tr->progs_cnt[kind]--;
+ }
+ return err;
+}
+
+int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
+{
+ int err;
+
+ mutex_lock(&tr->mutex);
+ err = __bpf_trampoline_link_prog(link, tr);
+ mutex_unlock(&tr->mutex);
+ return err;
+}
+
+static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
+{
+ enum bpf_tramp_prog_type kind;
+ int err;
+
+ kind = bpf_attach_type_to_tramp(link->link.prog);
+ if (kind == BPF_TRAMP_REPLACE) {
+ WARN_ON_ONCE(!tr->extension_prog);
+ err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
+ tr->extension_prog->bpf_func, NULL);
+ tr->extension_prog = NULL;
+ return err;
+ }
+ hlist_del_init(&link->tramp_hlist);
+ tr->progs_cnt[kind]--;
+ return bpf_trampoline_update(tr, true /* lock_direct_mutex */);
+}
+
+/* bpf_trampoline_unlink_prog() should never fail. */
+int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
+{
+ int err;
+
+ mutex_lock(&tr->mutex);
+ err = __bpf_trampoline_unlink_prog(link, tr);
+ mutex_unlock(&tr->mutex);
+ return err;
+}
+
+#if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM)
+static void bpf_shim_tramp_link_release(struct bpf_link *link)
+{
+ struct bpf_shim_tramp_link *shim_link =
+ container_of(link, struct bpf_shim_tramp_link, link.link);
+
+ /* paired with 'shim_link->trampoline = tr' in bpf_trampoline_link_cgroup_shim */
+ if (!shim_link->trampoline)
+ return;
+
+ WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link, shim_link->trampoline));
+ bpf_trampoline_put(shim_link->trampoline);
+}
+
+static void bpf_shim_tramp_link_dealloc(struct bpf_link *link)
+{
+ struct bpf_shim_tramp_link *shim_link =
+ container_of(link, struct bpf_shim_tramp_link, link.link);
+
+ kfree(shim_link);
+}
+
+static const struct bpf_link_ops bpf_shim_tramp_link_lops = {
+ .release = bpf_shim_tramp_link_release,
+ .dealloc = bpf_shim_tramp_link_dealloc,
+};
+
+static struct bpf_shim_tramp_link *cgroup_shim_alloc(const struct bpf_prog *prog,
+ bpf_func_t bpf_func,
+ int cgroup_atype)
+{
+ struct bpf_shim_tramp_link *shim_link = NULL;
+ struct bpf_prog *p;
+
+ shim_link = kzalloc(sizeof(*shim_link), GFP_USER);
+ if (!shim_link)
+ return NULL;
+
+ p = bpf_prog_alloc(1, 0);
+ if (!p) {
+ kfree(shim_link);
+ return NULL;
+ }
+
+ p->jited = false;
+ p->bpf_func = bpf_func;
+
+ p->aux->cgroup_atype = cgroup_atype;
+ p->aux->attach_func_proto = prog->aux->attach_func_proto;
+ p->aux->attach_btf_id = prog->aux->attach_btf_id;
+ p->aux->attach_btf = prog->aux->attach_btf;
+ btf_get(p->aux->attach_btf);
+ p->type = BPF_PROG_TYPE_LSM;
+ p->expected_attach_type = BPF_LSM_MAC;
+ bpf_prog_inc(p);
+ bpf_link_init(&shim_link->link.link, BPF_LINK_TYPE_UNSPEC,
+ &bpf_shim_tramp_link_lops, p);
+ bpf_cgroup_atype_get(p->aux->attach_btf_id, cgroup_atype);
+
+ return shim_link;
+}
+
+static struct bpf_shim_tramp_link *cgroup_shim_find(struct bpf_trampoline *tr,
+ bpf_func_t bpf_func)
+{
+ struct bpf_tramp_link *link;
+ int kind;
+
+ for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
+ hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
+ struct bpf_prog *p = link->link.prog;
+
+ if (p->bpf_func == bpf_func)
+ return container_of(link, struct bpf_shim_tramp_link, link);
+ }
+ }
+
+ return NULL;
+}
+
+int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
+ int cgroup_atype)
+{
+ struct bpf_shim_tramp_link *shim_link = NULL;
+ struct bpf_attach_target_info tgt_info = {};
+ struct bpf_trampoline *tr;
+ bpf_func_t bpf_func;
+ u64 key;
+ int err;
+
+ err = bpf_check_attach_target(NULL, prog, NULL,
+ prog->aux->attach_btf_id,
+ &tgt_info);
+ if (err)
+ return err;
+
+ key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
+ prog->aux->attach_btf_id);
+
+ bpf_lsm_find_cgroup_shim(prog, &bpf_func);
+ tr = bpf_trampoline_get(key, &tgt_info);
+ if (!tr)
+ return -ENOMEM;
+
+ mutex_lock(&tr->mutex);
+
+ shim_link = cgroup_shim_find(tr, bpf_func);
+ if (shim_link) {
+ /* Reusing existing shim attached by the other program. */
+ bpf_link_inc(&shim_link->link.link);
+
+ mutex_unlock(&tr->mutex);
+ bpf_trampoline_put(tr); /* bpf_trampoline_get above */
+ return 0;
+ }
+
+ /* Allocate and install new shim. */
+
+ shim_link = cgroup_shim_alloc(prog, bpf_func, cgroup_atype);
+ if (!shim_link) {
+ err = -ENOMEM;
+ goto err;
+ }
+
+ err = __bpf_trampoline_link_prog(&shim_link->link, tr);
+ if (err)
+ goto err;
+
+ shim_link->trampoline = tr;
+ /* note, we're still holding tr refcnt from above */
+
+ mutex_unlock(&tr->mutex);
+
+ return 0;
+err:
+ mutex_unlock(&tr->mutex);
+
+ if (shim_link)
+ bpf_link_put(&shim_link->link.link);
+
+ /* have to release tr while _not_ holding its mutex */
+ bpf_trampoline_put(tr); /* bpf_trampoline_get above */
+
+ return err;
+}
+
+void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)
+{
+ struct bpf_shim_tramp_link *shim_link = NULL;
+ struct bpf_trampoline *tr;
+ bpf_func_t bpf_func;
+ u64 key;
+
+ key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
+ prog->aux->attach_btf_id);
+
+ bpf_lsm_find_cgroup_shim(prog, &bpf_func);
+ tr = bpf_trampoline_lookup(key);
+ if (WARN_ON_ONCE(!tr))
+ return;
+
+ mutex_lock(&tr->mutex);
+ shim_link = cgroup_shim_find(tr, bpf_func);
+ mutex_unlock(&tr->mutex);
+
+ if (shim_link)
+ bpf_link_put(&shim_link->link.link);
+
+ bpf_trampoline_put(tr); /* bpf_trampoline_lookup above */
+}
+#endif
+
+struct bpf_trampoline *bpf_trampoline_get(u64 key,
+ struct bpf_attach_target_info *tgt_info)
+{
+ struct bpf_trampoline *tr;
+
+ tr = bpf_trampoline_lookup(key);
+ if (!tr)
+ return NULL;
+
+ mutex_lock(&tr->mutex);
+ if (tr->func.addr)
+ goto out;
+
+ memcpy(&tr->func.model, &tgt_info->fmodel, sizeof(tgt_info->fmodel));
+ tr->func.addr = (void *)tgt_info->tgt_addr;
+out:
+ mutex_unlock(&tr->mutex);
+ return tr;
+}
+
+void bpf_trampoline_put(struct bpf_trampoline *tr)
+{
+ int i;
+
+ if (!tr)
+ return;
+ mutex_lock(&trampoline_mutex);
+ if (!refcount_dec_and_test(&tr->refcnt))
+ goto out;
+ WARN_ON_ONCE(mutex_is_locked(&tr->mutex));
+
+ for (i = 0; i < BPF_TRAMP_MAX; i++)
+ if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[i])))
+ goto out;
+
+ /* This code will be executed even when the last bpf_tramp_image
+ * is alive. All progs are detached from the trampoline and the
+ * trampoline image is patched with jmp into epilogue to skip
+ * fexit progs. The fentry-only trampoline will be freed via
+ * multiple rcu callbacks.
+ */
+ hlist_del(&tr->hlist);
+ if (tr->fops) {
+ ftrace_free_filter(tr->fops);
+ kfree(tr->fops);
+ }
+ kfree(tr);
+out:
+ mutex_unlock(&trampoline_mutex);
+}
+
+#define NO_START_TIME 1
+static __always_inline u64 notrace bpf_prog_start_time(void)
+{
+ u64 start = NO_START_TIME;
+
+ if (static_branch_unlikely(&bpf_stats_enabled_key)) {
+ start = sched_clock();
+ if (unlikely(!start))
+ start = NO_START_TIME;
+ }
+ return start;
+}
+
+/* The logic is similar to bpf_prog_run(), but with an explicit
+ * rcu_read_lock() and migrate_disable() which are required
+ * for the trampoline. The macro is split into
+ * call __bpf_prog_enter
+ * call prog->bpf_func
+ * call __bpf_prog_exit
+ *
+ * __bpf_prog_enter returns:
+ * 0 - skip execution of the bpf prog
+ * 1 - execute bpf prog
+ * [2..MAX_U64] - execute bpf prog and record execution time.
+ * This is start time.
+ */
+static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx)
+ __acquires(RCU)
+{
+ rcu_read_lock();
+ migrate_disable();
+
+ run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
+
+ if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
+ bpf_prog_inc_misses_counter(prog);
+ return 0;
+ }
+ return bpf_prog_start_time();
+}
+
+static void notrace update_prog_stats(struct bpf_prog *prog,
+ u64 start)
+{
+ struct bpf_prog_stats *stats;
+
+ if (static_branch_unlikely(&bpf_stats_enabled_key) &&
+ /* static_key could be enabled in __bpf_prog_enter*
+ * and disabled in __bpf_prog_exit*.
+ * And vice versa.
+ * Hence check that 'start' is valid.
+ */
+ start > NO_START_TIME) {
+ 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);
+ }
+}
+
+static void notrace __bpf_prog_exit_recur(struct bpf_prog *prog, u64 start,
+ struct bpf_tramp_run_ctx *run_ctx)
+ __releases(RCU)
+{
+ bpf_reset_run_ctx(run_ctx->saved_run_ctx);
+
+ update_prog_stats(prog, start);
+ this_cpu_dec(*(prog->active));
+ migrate_enable();
+ rcu_read_unlock();
+}
+
+static u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog,
+ struct bpf_tramp_run_ctx *run_ctx)
+ __acquires(RCU)
+{
+ /* Runtime stats are exported via actual BPF_LSM_CGROUP
+ * programs, not the shims.
+ */
+ rcu_read_lock();
+ migrate_disable();
+
+ run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
+
+ return NO_START_TIME;
+}
+
+static void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start,
+ struct bpf_tramp_run_ctx *run_ctx)
+ __releases(RCU)
+{
+ bpf_reset_run_ctx(run_ctx->saved_run_ctx);
+
+ migrate_enable();
+ rcu_read_unlock();
+}
+
+u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
+ struct bpf_tramp_run_ctx *run_ctx)
+{
+ rcu_read_lock_trace();
+ migrate_disable();
+ might_fault();
+
+ run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
+
+ if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
+ bpf_prog_inc_misses_counter(prog);
+ return 0;
+ }
+ return bpf_prog_start_time();
+}
+
+void notrace __bpf_prog_exit_sleepable_recur(struct bpf_prog *prog, u64 start,
+ struct bpf_tramp_run_ctx *run_ctx)
+{
+ bpf_reset_run_ctx(run_ctx->saved_run_ctx);
+
+ update_prog_stats(prog, start);
+ this_cpu_dec(*(prog->active));
+ migrate_enable();
+ rcu_read_unlock_trace();
+}
+
+static u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog,
+ struct bpf_tramp_run_ctx *run_ctx)
+{
+ rcu_read_lock_trace();
+ migrate_disable();
+ might_fault();
+
+ run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
+
+ return bpf_prog_start_time();
+}
+
+static void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
+ struct bpf_tramp_run_ctx *run_ctx)
+{
+ bpf_reset_run_ctx(run_ctx->saved_run_ctx);
+
+ update_prog_stats(prog, start);
+ migrate_enable();
+ rcu_read_unlock_trace();
+}
+
+static u64 notrace __bpf_prog_enter(struct bpf_prog *prog,
+ struct bpf_tramp_run_ctx *run_ctx)
+ __acquires(RCU)
+{
+ rcu_read_lock();
+ migrate_disable();
+
+ run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
+
+ return bpf_prog_start_time();
+}
+
+static void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start,
+ struct bpf_tramp_run_ctx *run_ctx)
+ __releases(RCU)
+{
+ bpf_reset_run_ctx(run_ctx->saved_run_ctx);
+
+ update_prog_stats(prog, start);
+ migrate_enable();
+ rcu_read_unlock();
+}
+
+void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr)
+{
+ percpu_ref_get(&tr->pcref);
+}
+
+void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)
+{
+ percpu_ref_put(&tr->pcref);
+}
+
+bpf_trampoline_enter_t bpf_trampoline_enter(const struct bpf_prog *prog)
+{
+ bool sleepable = prog->aux->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->aux->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 *tr, void *image, void *image_end,
+ const struct btf_func_model *m, u32 flags,
+ struct bpf_tramp_links *tlinks,
+ 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);
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-26 18:03:56 +0000