Update Linux to v5.10.109
Sourced from [1]
[1] https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.109.tar.xz
Change-Id: I19bca9fc6762d4e63bcf3e4cba88bbe560d9c76c
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
new file mode 100644
index 0000000..986dabc
--- /dev/null
+++ b/kernel/bpf/trampoline.c
@@ -0,0 +1,571 @@
+// 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>
+
+/* dummy _ops. The verifier will operate on target program's ops. */
+const struct bpf_verifier_ops bpf_extension_verifier_ops = {
+};
+const struct bpf_prog_ops bpf_extension_prog_ops = {
+};
+
+/* btf_vmlinux has ~22k attachable functions. 1k htab is enough. */
+#define TRAMPOLINE_HASH_BITS 10
+#define TRAMPOLINE_TABLE_SIZE (1 << TRAMPOLINE_HASH_BITS)
+
+static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE];
+
+/* serializes access to trampoline_table */
+static DEFINE_MUTEX(trampoline_mutex);
+
+void *bpf_jit_alloc_exec_page(void)
+{
+ void *image;
+
+ image = bpf_jit_alloc_exec(PAGE_SIZE);
+ if (!image)
+ return NULL;
+
+ set_vm_flush_reset_perms(image);
+ /* Keep image as writeable. The alternative is to keep flipping ro/rw
+ * everytime new program is attached or detached.
+ */
+ set_memory_x((long)image, 1);
+ return image;
+}
+
+void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym)
+{
+ ksym->start = (unsigned long) data;
+ ksym->end = ksym->start + PAGE_SIZE;
+ bpf_ksym_add(ksym);
+ perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
+ PAGE_SIZE, false, ksym->name);
+}
+
+void bpf_image_ksym_del(struct bpf_ksym *ksym)
+{
+ bpf_ksym_del(ksym);
+ perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
+ PAGE_SIZE, true, ksym->name);
+}
+
+static 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;
+
+ 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 is_ftrace_location(void *ip)
+{
+ long addr;
+
+ addr = ftrace_location((long)ip);
+ if (!addr)
+ return 0;
+ if (WARN_ON_ONCE(addr != (long)ip))
+ return -EFAULT;
+ return 1;
+}
+
+static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
+{
+ void *ip = tr->func.addr;
+ int ret;
+
+ if (tr->func.ftrace_managed)
+ ret = unregister_ftrace_direct((long)ip, (long)old_addr);
+ else
+ ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
+ return ret;
+}
+
+static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr)
+{
+ void *ip = tr->func.addr;
+ int ret;
+
+ if (tr->func.ftrace_managed)
+ ret = modify_ftrace_direct((long)ip, (long)old_addr, (long)new_addr);
+ else
+ ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr);
+ return ret;
+}
+
+/* first time registering */
+static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
+{
+ void *ip = tr->func.addr;
+ int ret;
+
+ ret = is_ftrace_location(ip);
+ if (ret < 0)
+ return ret;
+ tr->func.ftrace_managed = ret;
+
+ if (tr->func.ftrace_managed)
+ ret = register_ftrace_direct((long)ip, (long)new_addr);
+ else
+ ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
+ return ret;
+}
+
+static struct bpf_tramp_progs *
+bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total)
+{
+ const struct bpf_prog_aux *aux;
+ struct bpf_tramp_progs *tprogs;
+ struct bpf_prog **progs;
+ int kind;
+
+ *total = 0;
+ tprogs = kcalloc(BPF_TRAMP_MAX, sizeof(*tprogs), GFP_KERNEL);
+ if (!tprogs)
+ return ERR_PTR(-ENOMEM);
+
+ for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
+ tprogs[kind].nr_progs = tr->progs_cnt[kind];
+ *total += tr->progs_cnt[kind];
+ progs = tprogs[kind].progs;
+
+ hlist_for_each_entry(aux, &tr->progs_hlist[kind], tramp_hlist)
+ *progs++ = aux->prog;
+ }
+ return tprogs;
+}
+
+static 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_image_ksym_del(&im->ksym);
+ bpf_jit_free_exec(im->image);
+ bpf_jit_uncharge_modmem(1);
+ percpu_ref_exit(&im->pcref);
+ kfree_rcu(im, rcu);
+}
+
+/* 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, u32 idx)
+{
+ 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(1);
+ if (err)
+ goto out_free_im;
+
+ err = -ENOMEM;
+ im->image = image = bpf_jit_alloc_exec_page();
+ if (!image)
+ goto out_uncharge;
+
+ err = percpu_ref_init(&im->pcref, __bpf_tramp_image_release, 0, GFP_KERNEL);
+ if (err)
+ goto out_free_image;
+
+ ksym = &im->ksym;
+ INIT_LIST_HEAD_RCU(&ksym->lnode);
+ snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu_%u", key, idx);
+ bpf_image_ksym_add(image, ksym);
+ return im;
+
+out_free_image:
+ bpf_jit_free_exec(im->image);
+out_uncharge:
+ bpf_jit_uncharge_modmem(1);
+out_free_im:
+ kfree(im);
+out:
+ return ERR_PTR(err);
+}
+
+static int bpf_trampoline_update(struct bpf_trampoline *tr)
+{
+ struct bpf_tramp_image *im;
+ struct bpf_tramp_progs *tprogs;
+ u32 flags = BPF_TRAMP_F_RESTORE_REGS;
+ int err, total;
+
+ tprogs = bpf_trampoline_get_progs(tr, &total);
+ if (IS_ERR(tprogs))
+ return PTR_ERR(tprogs);
+
+ if (total == 0) {
+ err = unregister_fentry(tr, tr->cur_image->image);
+ bpf_tramp_image_put(tr->cur_image);
+ tr->cur_image = NULL;
+ tr->selector = 0;
+ goto out;
+ }
+
+ im = bpf_tramp_image_alloc(tr->key, tr->selector);
+ if (IS_ERR(im)) {
+ err = PTR_ERR(im);
+ goto out;
+ }
+
+ if (tprogs[BPF_TRAMP_FEXIT].nr_progs ||
+ tprogs[BPF_TRAMP_MODIFY_RETURN].nr_progs)
+ flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
+
+ err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,
+ &tr->func.model, flags, tprogs,
+ tr->func.addr);
+ if (err < 0)
+ goto out;
+
+ 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 */
+ err = modify_fentry(tr, tr->cur_image->image, im->image);
+ else
+ /* first time registering */
+ err = register_fentry(tr, im->image);
+ if (err)
+ goto out;
+ if (tr->cur_image)
+ bpf_tramp_image_put(tr->cur_image);
+ tr->cur_image = im;
+ tr->selector++;
+out:
+ kfree(tprogs);
+ return err;
+}
+
+static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
+{
+ switch (prog->expected_attach_type) {
+ case BPF_TRACE_FENTRY:
+ return BPF_TRAMP_FENTRY;
+ case BPF_MODIFY_RETURN:
+ return BPF_TRAMP_MODIFY_RETURN;
+ case BPF_TRACE_FEXIT:
+ return BPF_TRAMP_FEXIT;
+ case BPF_LSM_MAC:
+ if (!prog->aux->attach_func_proto->type)
+ /* The function returns void, we cannot modify its
+ * return value.
+ */
+ return BPF_TRAMP_FEXIT;
+ else
+ return BPF_TRAMP_MODIFY_RETURN;
+ default:
+ return BPF_TRAMP_REPLACE;
+ }
+}
+
+int bpf_trampoline_link_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
+{
+ enum bpf_tramp_prog_type kind;
+ int err = 0;
+ int cnt;
+
+ kind = bpf_attach_type_to_tramp(prog);
+ mutex_lock(&tr->mutex);
+ if (tr->extension_prog) {
+ /* cannot attach fentry/fexit if extension prog is attached.
+ * cannot overwrite extension prog either.
+ */
+ err = -EBUSY;
+ goto out;
+ }
+ cnt = tr->progs_cnt[BPF_TRAMP_FENTRY] + tr->progs_cnt[BPF_TRAMP_FEXIT];
+ if (kind == BPF_TRAMP_REPLACE) {
+ /* Cannot attach extension if fentry/fexit are in use. */
+ if (cnt) {
+ err = -EBUSY;
+ goto out;
+ }
+ tr->extension_prog = prog;
+ err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
+ prog->bpf_func);
+ goto out;
+ }
+ if (cnt >= BPF_MAX_TRAMP_PROGS) {
+ err = -E2BIG;
+ goto out;
+ }
+ if (!hlist_unhashed(&prog->aux->tramp_hlist)) {
+ /* prog already linked */
+ err = -EBUSY;
+ goto out;
+ }
+ hlist_add_head(&prog->aux->tramp_hlist, &tr->progs_hlist[kind]);
+ tr->progs_cnt[kind]++;
+ err = bpf_trampoline_update(tr);
+ if (err) {
+ hlist_del(&prog->aux->tramp_hlist);
+ tr->progs_cnt[kind]--;
+ }
+out:
+ mutex_unlock(&tr->mutex);
+ return err;
+}
+
+/* bpf_trampoline_unlink_prog() should never fail. */
+int bpf_trampoline_unlink_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
+{
+ enum bpf_tramp_prog_type kind;
+ 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)
+{
+ 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);
+}
+
+/* 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);