@@ -1735,7 +1735,7 @@ static int invoke_bpf_mod_ret(const struct btf_func_model *m, u8 **pprog,
* add rsp, 8 // skip eth_type_trans's frame
* ret // return to its caller
*/
-int arch_prepare_bpf_trampoline(void *image, void *image_end,
+int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image_end,
const struct btf_func_model *m, u32 flags,
struct bpf_tramp_progs *tprogs,
void *orig_call)
@@ -1774,6 +1774,15 @@ int arch_prepare_bpf_trampoline(void *image, void *image_end,
save_regs(m, &prog, nr_args, stack_size);
+ if (flags & BPF_TRAMP_F_CALL_ORIG) {
+ /* arg1: mov rdi, im */
+ emit_mov_imm64(&prog, BPF_REG_1, (long) im >> 32, (u32) (long) im);
+ if (emit_call(&prog, __bpf_tramp_enter, prog)) {
+ ret = -EINVAL;
+ goto cleanup;
+ }
+ }
+
if (fentry->nr_progs)
if (invoke_bpf(m, &prog, fentry, stack_size))
return -EINVAL;
@@ -1792,8 +1801,7 @@ int arch_prepare_bpf_trampoline(void *image, void *image_end,
}
if (flags & BPF_TRAMP_F_CALL_ORIG) {
- if (fentry->nr_progs || fmod_ret->nr_progs)
- restore_regs(m, &prog, nr_args, stack_size);
+ restore_regs(m, &prog, nr_args, stack_size);
/* call original function */
if (emit_call(&prog, orig_call, prog)) {
@@ -1802,6 +1810,8 @@ int arch_prepare_bpf_trampoline(void *image, void *image_end,
}
/* remember return value in a stack for bpf prog to access */
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
+ im->ip_after_call = prog;
+ emit_nops(&prog, 5);
}
if (fmod_ret->nr_progs) {
@@ -1832,9 +1842,17 @@ int arch_prepare_bpf_trampoline(void *image, void *image_end,
* the return value is only updated on the stack and still needs to be
* restored to R0.
*/
- if (flags & BPF_TRAMP_F_CALL_ORIG)
+ if (flags & BPF_TRAMP_F_CALL_ORIG) {
+ im->ip_epilogue = prog;
+ /* arg1: mov rdi, im */
+ emit_mov_imm64(&prog, BPF_REG_1, (long) im >> 32, (u32) (long) im);
+ if (emit_call(&prog, __bpf_tramp_exit, prog)) {
+ ret = -EINVAL;
+ goto cleanup;
+ }
/* restore original return value back into RAX */
emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, -8);
+ }
EMIT1(0x5B); /* pop rbx */
EMIT1(0xC9); /* leave */
@@ -22,6 +22,7 @@
#include <linux/capability.h>
#include <linux/sched/mm.h>
#include <linux/slab.h>
+#include <linux/percpu-refcount.h>
struct bpf_verifier_env;
struct bpf_verifier_log;
@@ -563,7 +564,8 @@ struct bpf_tramp_progs {
* fentry = a set of program to run before calling original function
* fexit = a set of program to run after original function
*/
-int arch_prepare_bpf_trampoline(void *image, void *image_end,
+struct bpf_tramp_image;
+int 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);
@@ -572,6 +574,8 @@ u64 notrace __bpf_prog_enter(void);
void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start);
void notrace __bpf_prog_enter_sleepable(void);
void notrace __bpf_prog_exit_sleepable(void);
+void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr);
+void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr);
struct bpf_ksym {
unsigned long start;
@@ -590,6 +594,18 @@ enum bpf_tramp_prog_type {
BPF_TRAMP_REPLACE, /* more than MAX */
};
+struct bpf_tramp_image {
+ void *image;
+ struct bpf_ksym ksym;
+ struct percpu_ref pcref;
+ void *ip_after_call;
+ void *ip_epilogue;
+ union {
+ struct rcu_head rcu;
+ struct work_struct work;
+ };
+};
+
struct bpf_trampoline {
/* hlist for trampoline_table */
struct hlist_node hlist;
@@ -612,9 +628,8 @@ struct bpf_trampoline {
/* Number of attached programs. A counter per kind. */
int progs_cnt[BPF_TRAMP_MAX];
/* Executable image of trampoline */
- void *image;
+ struct bpf_tramp_image *cur_image;
u64 selector;
- struct bpf_ksym ksym;
};
struct bpf_attach_target_info {
@@ -698,6 +713,8 @@ void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym);
void bpf_image_ksym_del(struct bpf_ksym *ksym);
void bpf_ksym_add(struct bpf_ksym *ksym);
void bpf_ksym_del(struct bpf_ksym *ksym);
+int bpf_jit_charge_modmem(u32 pages);
+void bpf_jit_uncharge_modmem(u32 pages);
#else
static inline int bpf_trampoline_link_prog(struct bpf_prog *prog,
struct bpf_trampoline *tr)
@@ -788,7 +805,6 @@ struct bpf_prog_aux {
bool func_proto_unreliable;
bool sleepable;
bool tail_call_reachable;
- enum bpf_tramp_prog_type trampoline_prog_type;
struct hlist_node tramp_hlist;
/* BTF_KIND_FUNC_PROTO for valid attach_btf_id */
const struct btf_type *attach_func_proto;
@@ -430,7 +430,7 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
tprogs[BPF_TRAMP_FENTRY].progs[0] = prog;
tprogs[BPF_TRAMP_FENTRY].nr_progs = 1;
- err = arch_prepare_bpf_trampoline(image,
+ err = arch_prepare_bpf_trampoline(NULL, image,
st_map->image + PAGE_SIZE,
&st_ops->func_models[i], 0,
tprogs, NULL);
@@ -817,7 +817,7 @@ static int __init bpf_jit_charge_init(void)
}
pure_initcall(bpf_jit_charge_init);
-static int bpf_jit_charge_modmem(u32 pages)
+int bpf_jit_charge_modmem(u32 pages)
{
if (atomic_long_add_return(pages, &bpf_jit_current) >
(bpf_jit_limit >> PAGE_SHIFT)) {
@@ -830,7 +830,7 @@ static int bpf_jit_charge_modmem(u32 pages)
return 0;
}
-static void bpf_jit_uncharge_modmem(u32 pages)
+void bpf_jit_uncharge_modmem(u32 pages)
{
atomic_long_sub(pages, &bpf_jit_current);
}
@@ -57,19 +57,10 @@ void bpf_image_ksym_del(struct bpf_ksym *ksym)
PAGE_SIZE, true, ksym->name);
}
-static void bpf_trampoline_ksym_add(struct bpf_trampoline *tr)
-{
- struct bpf_ksym *ksym = &tr->ksym;
-
- snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu", tr->key);
- bpf_image_ksym_add(tr->image, ksym);
-}
-
static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
{
struct bpf_trampoline *tr;
struct hlist_head *head;
- void *image;
int i;
mutex_lock(&trampoline_mutex);
@@ -84,14 +75,6 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
if (!tr)
goto out;
- /* is_root was checked earlier. No need for bpf_jit_charge_modmem() */
- image = bpf_jit_alloc_exec_page();
- if (!image) {
- kfree(tr);
- tr = NULL;
- goto out;
- }
-
tr->key = key;
INIT_HLIST_NODE(&tr->hlist);
hlist_add_head(&tr->hlist, head);
@@ -99,9 +82,6 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
mutex_init(&tr->mutex);
for (i = 0; i < BPF_TRAMP_MAX; i++)
INIT_HLIST_HEAD(&tr->progs_hlist[i]);
- tr->image = image;
- INIT_LIST_HEAD_RCU(&tr->ksym.lnode);
- bpf_trampoline_ksym_add(tr);
out:
mutex_unlock(&trampoline_mutex);
return tr;
@@ -185,10 +165,142 @@ bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total)
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)
{
- void *old_image = tr->image + ((tr->selector + 1) & 1) * PAGE_SIZE/2;
- void *new_image = tr->image + (tr->selector & 1) * PAGE_SIZE/2;
+ struct bpf_tramp_image *im;
struct bpf_tramp_progs *tprogs;
u32 flags = BPF_TRAMP_F_RESTORE_REGS;
int err, total;
@@ -198,41 +310,42 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
return PTR_ERR(tprogs);
if (total == 0) {
- err = unregister_fentry(tr, old_image);
+ 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;
- /* Though the second half of trampoline page is unused a task could be
- * preempted in the middle of the first half of trampoline and two
- * updates to trampoline would change the code from underneath the
- * preempted task. Hence wait for tasks to voluntarily schedule or go
- * to userspace.
- * The same trampoline can hold both sleepable and non-sleepable progs.
- * synchronize_rcu_tasks_trace() is needed to make sure all sleepable
- * programs finish executing.
- * Wait for these two grace periods together.
- */
- synchronize_rcu_mult(call_rcu_tasks, call_rcu_tasks_trace);
-
- err = arch_prepare_bpf_trampoline(new_image, new_image + PAGE_SIZE / 2,
+ 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;
- if (tr->selector)
+ 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, old_image, new_image);
+ err = modify_fentry(tr, tr->cur_image->image, im->image);
else
/* first time registering */
- err = register_fentry(tr, new_image);
+ 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);
@@ -364,17 +477,12 @@ void bpf_trampoline_put(struct bpf_trampoline *tr)
goto out;
if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[BPF_TRAMP_FEXIT])))
goto out;
- bpf_image_ksym_del(&tr->ksym);
- /* This code will be executed when all bpf progs (both sleepable and
- * non-sleepable) went through
- * bpf_prog_put()->call_rcu[_tasks_trace]()->bpf_prog_free_deferred().
- * Hence no need for another synchronize_rcu_tasks_trace() here,
- * but synchronize_rcu_tasks() is still needed, since trampoline
- * may not have had any sleepable programs and we need to wait
- * for tasks to get out of trampoline code before freeing it.
+ /* 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.
*/
- synchronize_rcu_tasks();
- bpf_jit_free_exec(tr->image);
hlist_del(&tr->hlist);
kfree(tr);
out:
@@ -433,8 +541,18 @@ 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(void *image, void *image_end,
+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)