[PATCH bpf-next v8 00/11] bpf: Support multi-attach for freplace programs

@@ -621,6 +621,8 @@ static __always_inline unsigned int bpf_dispatcher_nop_func(
 struct bpf_trampoline *bpf_trampoline_lookup(u64 key);
 int bpf_trampoline_link_prog(struct bpf_prog *prog);
 int bpf_trampoline_unlink_prog(struct bpf_prog *prog);
+struct bpf_trampoline *bpf_trampoline_get(u64 key, void *addr,
+					  struct btf_func_model *fmodel);
 void bpf_trampoline_put(struct bpf_trampoline *tr);
 #define BPF_DISPATCHER_INIT(_name) {				\
 	.mutex = __MUTEX_INITIALIZER(_name.mutex),		\

@@ -677,6 +679,11 @@ static inline int bpf_trampoline_unlink_prog(struct bpf_prog *prog)
 {
 	return -ENOTSUPP;
 }
+static inline struct bpf_trampoline *bpf_trampoline_get(u64 key, void *addr,
+							struct btf_func_model *fmodel)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
 static inline void bpf_trampoline_put(struct bpf_trampoline *tr) {}
 #define DEFINE_BPF_DISPATCHER(name)
 #define DECLARE_BPF_DISPATCHER(name)

@@ -450,4 +450,13 @@ bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
 int check_ctx_reg(struct bpf_verifier_env *env,
 		  const struct bpf_reg_state *reg, int regno);
 
+int bpf_check_attach_target(struct bpf_verifier_log *log,
+			    const struct bpf_prog *prog,
+			    const struct bpf_prog *tgt_prog,
+			    u32 btf_id,
+			    struct btf_func_model *fmodel,
+			    long *tgt_addr,
+			    const char **tgt_name,
+			    const struct btf_type **tgt_type);
+
 #endif /* _LINUX_BPF_VERIFIER_H */

@@ -336,6 +336,26 @@ int bpf_trampoline_unlink_prog(struct bpf_prog *prog)
 	return err;
 }
 
+struct bpf_trampoline *bpf_trampoline_get(u64 key, void *addr,
+					  struct btf_func_model *fmodel)
+{
+	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, fmodel, sizeof(*fmodel));
+	tr->func.addr = addr;
+out:
+	mutex_unlock(&tr->mutex);
+	return tr;
+}
+
 void bpf_trampoline_put(struct bpf_trampoline *tr)
 {
 	if (!tr)

@@ -11174,11 +11174,11 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
 }
 #define SECURITY_PREFIX "security_"
 
-static int check_attach_modify_return(struct bpf_prog *prog, unsigned long addr)
+static int check_attach_modify_return(const struct bpf_prog *prog, unsigned long addr,
+				      const char *func_name)
 {
 	if (within_error_injection_list(addr) ||
-	    !strncmp(SECURITY_PREFIX, prog->aux->attach_func_name,
-		     sizeof(SECURITY_PREFIX) - 1))
+	    !strncmp(SECURITY_PREFIX, func_name, sizeof(SECURITY_PREFIX) - 1))
 		return 0;
 
 	return -EINVAL;

@@ -11215,43 +11215,29 @@ static int check_non_sleepable_error_inject(u32 btf_id)
 	return btf_id_set_contains(&btf_non_sleepable_error_inject, btf_id);
 }
 
-static int check_attach_btf_id(struct bpf_verifier_env *env)
+int bpf_check_attach_target(struct bpf_verifier_log *log,
+			    const struct bpf_prog *prog,
+			    const struct bpf_prog *tgt_prog,
+			    u32 btf_id,
+			    struct btf_func_model *fmodel,
+			    long *tgt_addr,
+			    const char **tgt_name,
+			    const struct btf_type **tgt_type)
 {
-	struct bpf_prog *prog = env->prog;
 	bool prog_extension = prog->type == BPF_PROG_TYPE_EXT;
-	struct bpf_prog *tgt_prog = prog->aux->linked_prog;
-	struct bpf_verifier_log *log = &env->log;
-	u32 btf_id = prog->aux->attach_btf_id;
 	const char prefix[] = "btf_trace_";
-	struct btf_func_model fmodel;
 	int ret = 0, subprog = -1, i;
-	struct bpf_trampoline *tr;
 	const struct btf_type *t;
 	bool conservative = true;
 	const char *tname;
 	struct btf *btf;
-	long addr;
-	u64 key;
-
-	if (prog->aux->sleepable && prog->type != BPF_PROG_TYPE_TRACING &&
-	    prog->type != BPF_PROG_TYPE_LSM) {
-		verbose(env, "Only fentry/fexit/fmod_ret and lsm programs can be sleepable\n");
-		return -EINVAL;
-	}
-
-	if (prog->type == BPF_PROG_TYPE_STRUCT_OPS)
-		return check_struct_ops_btf_id(env);
-
-	if (prog->type != BPF_PROG_TYPE_TRACING &&
-	    prog->type != BPF_PROG_TYPE_LSM &&
-	    !prog_extension)
-		return 0;
+	long addr = 0;
 
 	if (!btf_id) {
 		bpf_log(log, "Tracing programs must provide btf_id\n");
 		return -EINVAL;
 	}
-	btf = bpf_prog_get_target_btf(prog);
+	btf = tgt_prog ? tgt_prog->aux->btf : btf_vmlinux;
 	if (!btf) {
 		bpf_log(log,
 			"FENTRY/FEXIT program can only be attached to another program annotated with BTF\n");

@@ -11291,8 +11277,6 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 					"Extension programs should be JITed\n");
 				return -EINVAL;
 			}
-			env->ops = bpf_verifier_ops[tgt_prog->type];
-			prog->expected_attach_type = tgt_prog->expected_attach_type;
 		}
 		if (!tgt_prog->jited) {
 			bpf_log(log, "Can attach to only JITed progs\n");

@@ -11328,13 +11312,11 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 			bpf_log(log, "Cannot extend fentry/fexit\n");
 			return -EINVAL;
 		}
-		key = ((u64)aux->id) << 32 | btf_id;
 	} else {
 		if (prog_extension) {
 			bpf_log(log, "Cannot replace kernel functions\n");
 			return -EINVAL;
 		}
-		key = btf_id;
 	}
 
 	switch (prog->expected_attach_type) {

@@ -11364,13 +11346,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 			/* should never happen in valid vmlinux build */
 			return -EINVAL;
 
-		/* remember two read only pointers that are valid for
-		 * the life time of the kernel
-		 */
-		prog->aux->attach_func_name = tname;
-		prog->aux->attach_func_proto = t;
-		prog->aux->attach_btf_trace = true;
-		return 0;
+		break;
 	case BPF_TRACE_ITER:
 		if (!btf_type_is_func(t)) {
 			bpf_log(log, "attach_btf_id %u is not a function\n",

@@ -11380,12 +11356,10 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 		t = btf_type_by_id(btf, t->type);
 		if (!btf_type_is_func_proto(t))
 			return -EINVAL;
-		prog->aux->attach_func_name = tname;
-		prog->aux->attach_func_proto = t;
-		if (!bpf_iter_prog_supported(prog))
-			return -EINVAL;
-		ret = btf_distill_func_proto(log, btf, t, tname, &fmodel);
-		return ret;
+		ret = btf_distill_func_proto(log, btf, t, tname, fmodel);
+		if (ret)
+			return ret;
+		break;
 	default:
 		if (!prog_extension)
 			return -EINVAL;

@@ -11394,13 +11368,6 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 	case BPF_LSM_MAC:
 	case BPF_TRACE_FENTRY:
 	case BPF_TRACE_FEXIT:
-		prog->aux->attach_func_name = tname;
-		if (prog->type == BPF_PROG_TYPE_LSM) {
-			ret = bpf_lsm_verify_prog(log, prog);
-			if (ret < 0)
-				return ret;
-		}
-
 		if (!btf_type_is_func(t)) {
 			bpf_log(log, "attach_btf_id %u is not a function\n",
 				btf_id);

@@ -11412,24 +11379,14 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 		t = btf_type_by_id(btf, t->type);
 		if (!btf_type_is_func_proto(t))
 			return -EINVAL;
-		tr = bpf_trampoline_lookup(key);
-		if (!tr)
-			return -ENOMEM;
-		/* t is either vmlinux type or another program's type */
-		prog->aux->attach_func_proto = t;
-		mutex_lock(&tr->mutex);
-		if (tr->func.addr) {
-			prog->aux->trampoline = tr;
-			goto out;
-		}
-		if (tgt_prog && conservative) {
-			prog->aux->attach_func_proto = NULL;
+
+		if (tgt_prog && conservative)
 			t = NULL;
-		}
-		ret = btf_distill_func_proto(log, btf, t,
-					     tname, &tr->func.model);
+
+		ret = btf_distill_func_proto(log, btf, t, tname, fmodel);
 		if (ret < 0)
-			goto out;
+			return ret;
+
 		if (tgt_prog) {
 			if (subprog == 0)
 				addr = (long) tgt_prog->bpf_func;

@@ -11441,8 +11398,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 				bpf_log(log,
 					"The address of function %s cannot be found\n",
 					tname);
-				ret = -ENOENT;
-				goto out;
+				return -ENOENT;
 			}
 		}
 

@@ -11467,30 +11423,102 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 			default:
 				break;
 			}
-			if (ret)
-				bpf_log(log, "%s is not sleepable\n",
-					prog->aux->attach_func_name);
+			if (ret) {
+				bpf_log(log, "%s is not sleepable\n", tname);
+				return ret;
+			}
 		} else if (prog->expected_attach_type == BPF_MODIFY_RETURN) {
 			if (tgt_prog) {
 				bpf_log(log, "can't modify return codes of BPF programs\n");
-				ret = -EINVAL;
-				goto out;
+				return -EINVAL;
+			}
+			ret = check_attach_modify_return(prog, addr, tname);
+			if (ret) {
+				bpf_log(log, "%s() is not modifiable\n", tname);
+				return ret;
 			}
-			ret = check_attach_modify_return(prog, addr);
-			if (ret)
-				bpf_log(log, "%s() is not modifiable\n",
-					prog->aux->attach_func_name);
 		}
-		if (ret)
-			goto out;
-		tr->func.addr = (void *)addr;
-		prog->aux->trampoline = tr;
-out:
-		mutex_unlock(&tr->mutex);
-		if (ret)
-			bpf_trampoline_put(tr);
+
+		break;
+	}
+	*tgt_addr = addr;
+	if (tgt_name)
+		*tgt_name = tname;
+	if (tgt_type)
+		*tgt_type = t;
+	return 0;
+}
+
+static int check_attach_btf_id(struct bpf_verifier_env *env)
+{
+	struct bpf_prog *prog = env->prog;
+	struct bpf_prog *tgt_prog = prog->aux->linked_prog;
+	u32 btf_id = prog->aux->attach_btf_id;
+	struct btf_func_model fmodel;
+	struct bpf_trampoline *tr;
+	const struct btf_type *t;
+	const char *tname;
+	long addr;
+	int ret;
+	u64 key;
+
+	if (prog->aux->sleepable && prog->type != BPF_PROG_TYPE_TRACING &&
+	    prog->type != BPF_PROG_TYPE_LSM) {
+		verbose(env, "Only fentry/fexit/fmod_ret and lsm programs can be sleepable\n");
+		return -EINVAL;
+	}
+
+	if (prog->type == BPF_PROG_TYPE_STRUCT_OPS)
+		return check_struct_ops_btf_id(env);
+
+	if (prog->type != BPF_PROG_TYPE_TRACING &&
+	    prog->type != BPF_PROG_TYPE_LSM &&
+	    prog->type != BPF_PROG_TYPE_EXT)
+		return 0;
+
+	ret = bpf_check_attach_target(&env->log, prog, tgt_prog, btf_id,
+				      &fmodel, &addr, &tname, &t);
+	if (ret)
 		return ret;
+
+	if (tgt_prog) {
+		if (prog->type == BPF_PROG_TYPE_EXT) {
+			env->ops = bpf_verifier_ops[tgt_prog->type];
+			prog->expected_attach_type =
+				tgt_prog->expected_attach_type;
+		}
+		key = ((u64)tgt_prog->aux->id) << 32 | btf_id;
+	} else {
+		key = btf_id;
 	}
+
+	/* remember two read only pointers that are valid for
+	 * the life time of the kernel
+	 */
+	prog->aux->attach_func_proto = t;
+	prog->aux->attach_func_name = tname;
+
+	if (prog->expected_attach_type == BPF_TRACE_RAW_TP) {
+		prog->aux->attach_btf_trace = true;
+		return 0;
+	} else if (prog->expected_attach_type == BPF_TRACE_ITER) {
+		if (!bpf_iter_prog_supported(prog))
+			return -EINVAL;
+		return 0;
+	}
+
+	if (prog->type == BPF_PROG_TYPE_LSM) {
+		ret = bpf_lsm_verify_prog(&env->log, prog);
+		if (ret < 0)
+			return ret;
+	}
+
+	tr = bpf_trampoline_get(key, (void *)addr, &fmodel);
+	if (!tr)
+		return -ENOMEM;
+
+	prog->aux->trampoline = tr;
+	return 0;
 }
 
 int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,

@@ -3860,7 +3860,14 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
 
 	info->reg_type = PTR_TO_BTF_ID;
 	if (tgt_prog) {
-		ret = btf_translate_to_vmlinux(log, btf, t, tgt_prog->type, arg);
+		enum bpf_prog_type tgt_type;
+
+		if (tgt_prog->type == BPF_PROG_TYPE_EXT)
+			tgt_type = tgt_prog->aux->tgt_prog_type;
+		else
+			tgt_type = tgt_prog->type;
+
+		ret = btf_translate_to_vmlinux(log, btf, t, tgt_type, arg);
 		if (ret > 0) {
 			info->btf_id = ret;
 			return true;

@@ -751,6 +751,8 @@ struct bpf_prog_aux {
 	struct mutex tgt_mutex; /* protects tgt_* pointers below, *after* prog becomes visible */
 	struct bpf_prog *tgt_prog;
 	struct bpf_trampoline *tgt_trampoline;
+	enum bpf_prog_type tgt_prog_type;
+	enum bpf_attach_type tgt_attach_type;
 	bool verifier_zext; /* Zero extensions has been inserted by verifier. */
 	bool offload_requested;
 	bool attach_btf_trace; /* true if attaching to BTF-enabled raw tp */

@@ -632,8 +632,13 @@ union bpf_attr {
 		};
 		__u32		attach_type;	/* attach type */
 		__u32		flags;		/* extra flags */
-		__aligned_u64	iter_info;	/* extra bpf_iter_link_info */
-		__u32		iter_info_len;	/* iter_info length */
+		union {
+			__u32		target_btf_id;	/* btf_id of target to attach to */
+			struct {
+				__aligned_u64	iter_info;	/* extra bpf_iter_link_info */
+				__u32		iter_info_len;	/* iter_info length */
+			};
+		};
 	} link_create;
 
 	struct { /* struct used by BPF_LINK_UPDATE command */

@@ -4,6 +4,7 @@
 #include <linux/bpf.h>
 #include <linux/bpf_trace.h>
 #include <linux/bpf_lirc.h>
+#include <linux/bpf_verifier.h>
 #include <linux/btf.h>
 #include <linux/syscalls.h>
 #include <linux/slab.h>

@@ -2549,12 +2550,17 @@ static const struct bpf_link_ops bpf_tracing_link_lops = {
 	.fill_link_info = bpf_tracing_link_fill_link_info,
 };
 
-static int bpf_tracing_prog_attach(struct bpf_prog *prog)
+static int bpf_tracing_prog_attach(struct bpf_prog *prog,
+				   int tgt_prog_fd,
+				   u32 btf_id)
 {
 	struct bpf_link_primer link_primer;
 	struct bpf_prog *tgt_prog = NULL;
+	struct bpf_trampoline *tr = NULL;
 	struct bpf_tracing_link *link;
-	struct bpf_trampoline *tr;
+	struct btf_func_model fmodel;
+	u64 key = 0;
+	long addr;
 	int err;
 
 	switch (prog->type) {

@@ -2583,6 +2589,28 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog)
 		goto out_put_prog;
 	}
 
+	if (!!tgt_prog_fd != !!btf_id) {
+		err = -EINVAL;
+		goto out_put_prog;
+	}
+
+	if (tgt_prog_fd) {
+		/* For now we only allow new targets for BPF_PROG_TYPE_EXT */
+		if (prog->type != BPF_PROG_TYPE_EXT) {
+			err = -EINVAL;
+			goto out_put_prog;
+		}
+
+		tgt_prog = bpf_prog_get(tgt_prog_fd);
+		if (IS_ERR(tgt_prog)) {
+			err = PTR_ERR(tgt_prog);
+			tgt_prog = NULL;
+			goto out_put_prog;
+		}
+
+		key = ((u64)tgt_prog->aux->id) << 32 | btf_id;
+	}
+
 	link = kzalloc(sizeof(*link), GFP_USER);
 	if (!link) {
 		err = -ENOMEM;

@@ -2594,12 +2622,28 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog)
 
 	mutex_lock(&prog->aux->tgt_mutex);
 
-	if (!prog->aux->tgt_trampoline) {
+	if (!prog->aux->tgt_trampoline && !tgt_prog) {
 		err = -ENOENT;
 		goto out_unlock;
 	}
-	tr = prog->aux->tgt_trampoline;
-	tgt_prog = prog->aux->tgt_prog;
+
+	if (!prog->aux->tgt_trampoline ||
+	    (key && key != prog->aux->tgt_trampoline->key)) {
+
+		err = bpf_check_attach_target(NULL, prog, tgt_prog, btf_id,
+					      &fmodel, &addr, NULL, NULL);
+		if (err)
+			goto out_unlock;
+
+		tr = bpf_trampoline_get(key, (void *)addr, &fmodel);
+		if (!tr) {
+			err = -ENOMEM;
+			goto out_unlock;
+		}
+	} else {
+		tr = prog->aux->tgt_trampoline;
+		tgt_prog = prog->aux->tgt_prog;
+	}
 
 	err = bpf_link_prime(&link->link, &link_primer);
 	if (err)

@@ -2614,16 +2658,24 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog)
 
 	link->tgt_prog = tgt_prog;
 	link->trampoline = tr;
-
-	prog->aux->tgt_prog = NULL;
-	prog->aux->tgt_trampoline = NULL;
+	if (tr == prog->aux->tgt_trampoline) {
+		/* if we got a new ref from syscall, drop existing one from prog */
+		if (tgt_prog_fd)
+			bpf_prog_put(prog->aux->tgt_prog);
+		prog->aux->tgt_trampoline = NULL;
+		prog->aux->tgt_prog = NULL;
+	}
 	mutex_unlock(&prog->aux->tgt_mutex);
 
 	return bpf_link_settle(&link_primer);
 out_unlock:
+	if (tr && tr != prog->aux->tgt_trampoline)
+		bpf_trampoline_put(tr);
 	mutex_unlock(&prog->aux->tgt_mutex);
 	kfree(link);
 out_put_prog:
+	if (tgt_prog_fd && tgt_prog)
+		bpf_prog_put(tgt_prog);
 	bpf_prog_put(prog);
 	return err;
 }

@@ -2737,7 +2789,7 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
 			tp_name = prog->aux->attach_func_name;
 			break;
 		}
-		return bpf_tracing_prog_attach(prog);
+		return bpf_tracing_prog_attach(prog, 0, 0);
 	case BPF_PROG_TYPE_RAW_TRACEPOINT:
 	case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:
 		if (strncpy_from_user(buf,

@@ -3921,10 +3973,15 @@ static int bpf_map_do_batch(const union bpf_attr *attr,
 
 static int tracing_bpf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 {
-	if (attr->link_create.attach_type == BPF_TRACE_ITER &&
-	    prog->expected_attach_type == BPF_TRACE_ITER)
-		return bpf_iter_link_attach(attr, prog);
+	if (attr->link_create.attach_type != prog->expected_attach_type)
+		return -EINVAL;
 
+	if (prog->expected_attach_type == BPF_TRACE_ITER)
+		return bpf_iter_link_attach(attr, prog);
+	else if (prog->type == BPF_PROG_TYPE_EXT)
+		return bpf_tracing_prog_attach(prog,
+					       attr->link_create.target_fd,
+					       attr->link_create.target_btf_id);
 	return -EINVAL;
 }
 

@@ -3938,18 +3995,25 @@ static int link_create(union bpf_attr *attr)
 	if (CHECK_ATTR(BPF_LINK_CREATE))
 		return -EINVAL;
 
-	ptype = attach_type_to_prog_type(attr->link_create.attach_type);
-	if (ptype == BPF_PROG_TYPE_UNSPEC)
-		return -EINVAL;
-
-	prog = bpf_prog_get_type(attr->link_create.prog_fd, ptype);
+	prog = bpf_prog_get(attr->link_create.prog_fd);
 	if (IS_ERR(prog))
 		return PTR_ERR(prog);
 
 	ret = bpf_prog_attach_check_attach_type(prog,
 						attr->link_create.attach_type);
 	if (ret)
-		goto err_out;
+		goto out;
+
+	if (prog->type == BPF_PROG_TYPE_EXT) {
+		ret = tracing_bpf_link_attach(attr, prog);
+		goto out;
+	}
+
+	ptype = attach_type_to_prog_type(attr->link_create.attach_type);
+	if (ptype == BPF_PROG_TYPE_UNSPEC || ptype != prog->type) {
+		ret = -EINVAL;
+		goto out;
+	}
 
 	switch (ptype) {
 	case BPF_PROG_TYPE_CGROUP_SKB:

@@ -3977,7 +4041,7 @@ static int link_create(union bpf_attr *attr)
 		ret = -EINVAL;
 	}
 
-err_out:
+out:
 	if (ret < 0)
 		bpf_prog_put(prog);
 	return ret;

@@ -11379,6 +11379,12 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
 		if (!btf_type_is_func_proto(t))
 			return -EINVAL;
 
+		if ((prog->aux->tgt_prog_type &&
+		     prog->aux->tgt_prog_type != tgt_prog->type) ||
+		    (prog->aux->tgt_attach_type &&
+		     prog->aux->tgt_attach_type != tgt_prog->expected_attach_type))
+			return -EINVAL;
+
 		if (tgt_prog && conservative)
 			t = NULL;
 

@@ -11481,6 +11487,9 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 		return ret;
 
 	if (tgt_prog) {
+		prog->aux->tgt_prog_type = tgt_prog->type;
+		prog->aux->tgt_attach_type = tgt_prog->expected_attach_type;
+
 		if (prog->type == BPF_PROG_TYPE_EXT) {
 			env->ops = bpf_verifier_ops[tgt_prog->type];
 			prog->expected_attach_type =

@@ -632,8 +632,13 @@ union bpf_attr {
 		};
 		__u32		attach_type;	/* attach type */
 		__u32		flags;		/* extra flags */
-		__aligned_u64	iter_info;	/* extra bpf_iter_link_info */
-		__u32		iter_info_len;	/* iter_info length */
+		union {
+			__u32		target_btf_id;	/* btf_id of target to attach to */
+			struct {
+				__aligned_u64	iter_info;	/* extra bpf_iter_link_info */
+				__u32		iter_info_len;	/* iter_info length */
+			};
+		};
 	} link_create;
 
 	struct { /* struct used by BPF_LINK_UPDATE command */

@@ -232,6 +232,60 @@ static void test_func_replace_multi(void)
 				  prog_name, true, test_second_attach);
 }
 
+static void test_fmod_ret_freplace(void)
+{
+	struct bpf_object *freplace_obj = NULL, *pkt_obj, *fmod_obj = NULL;
+	const char *freplace_name = "./freplace_get_constant.o";
+	const char *fmod_ret_name = "./fmod_ret_freplace.o";
+	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts);
+	const char *tgt_name = "./test_pkt_access.o";
+	struct bpf_link *freplace_link = NULL;
+	struct bpf_program *prog;
+	__u32 duration = 0;
+	int err, pkt_fd;
+
+	err = bpf_prog_load(tgt_name, BPF_PROG_TYPE_UNSPEC,
+			    &pkt_obj, &pkt_fd);
+	/* the target prog should load fine */
+	if (CHECK(err, "tgt_prog_load", "file %s err %d errno %d\n",
+		  tgt_name, err, errno))
+		return;
+	opts.attach_prog_fd = pkt_fd;
+
+	freplace_obj = bpf_object__open_file(freplace_name, &opts);
+	if (CHECK(IS_ERR_OR_NULL(freplace_obj), "freplace_obj_open",
+		  "failed to open %s: %ld\n", freplace_name,
+		  PTR_ERR(freplace_obj)))
+		goto out;
+
+	err = bpf_object__load(freplace_obj);
+	if (CHECK(err, "freplace_obj_load", "err %d\n", err))
+		goto out;
+
+	prog = bpf_program__next(NULL, freplace_obj);
+	freplace_link = bpf_program__attach_trace(prog);
+	if (CHECK(IS_ERR(freplace_link), "freplace_attach_trace", "failed to link\n"))
+		goto out;
+
+	opts.attach_prog_fd = bpf_program__fd(prog);
+	fmod_obj = bpf_object__open_file(fmod_ret_name, &opts);
+	if (CHECK(IS_ERR_OR_NULL(fmod_obj), "fmod_obj_open",
+		  "failed to open %s: %ld\n", fmod_ret_name,
+		  PTR_ERR(fmod_obj)))
+		goto out;
+
+	err = bpf_object__load(fmod_obj);
+	if (CHECK(!err, "fmod_obj_load", "loading fmod_ret should fail\n"))
+		goto out;
+
+out:
+	bpf_link__destroy(freplace_link);
+	bpf_object__close(freplace_obj);
+	bpf_object__close(fmod_obj);
+	bpf_object__close(pkt_obj);
+}
+
+
 static void test_func_sockmap_update(void)
 {
 	const char *prog_name[] = {

@@ -314,4 +368,6 @@ void test_fexit_bpf2bpf(void)
 		test_func_map_prog_compatibility();
 	if (test__start_subtest("func_replace_multi"))
 		test_func_replace_multi();
+	if (test__start_subtest("fmod_ret_freplace"))
+		test_fmod_ret_freplace();
 }

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+volatile __u64 test_fmod_ret = 0;
+SEC("fmod_ret/security_new_get_constant")
+int BPF_PROG(fmod_ret_test, long val, int ret)
+{
+	test_fmod_ret = 1;
+	return 120;
+}
+
+char _license[] SEC("license") = "GPL";

@@ -5,7 +5,7 @@
 
 volatile __u64 test_get_constant = 0;
 SEC("freplace/get_constant")
-int new_get_constant(long val)
+int security_new_get_constant(long val)
 {
 	if (val != 123)
 		return 0;

@@ -311,14 +311,12 @@ extern const struct bench bench_rename_kretprobe;
 extern const struct bench bench_rename_rawtp;
 extern const struct bench bench_rename_fentry;
 extern const struct bench bench_rename_fexit;
-extern const struct bench bench_rename_fmodret;
 extern const struct bench bench_trig_base;
 extern const struct bench bench_trig_tp;
 extern const struct bench bench_trig_rawtp;
 extern const struct bench bench_trig_kprobe;
 extern const struct bench bench_trig_fentry;
 extern const struct bench bench_trig_fentry_sleep;
-extern const struct bench bench_trig_fmodret;
 extern const struct bench bench_rb_libbpf;
 extern const struct bench bench_rb_custom;
 extern const struct bench bench_pb_libbpf;

@@ -333,14 +331,12 @@ static const struct bench *benchs[] = {
 	&bench_rename_rawtp,
 	&bench_rename_fentry,
 	&bench_rename_fexit,
-	&bench_rename_fmodret,
 	&bench_trig_base,
 	&bench_trig_tp,
 	&bench_trig_rawtp,
 	&bench_trig_kprobe,
 	&bench_trig_fentry,
 	&bench_trig_fentry_sleep,
-	&bench_trig_fmodret,
 	&bench_rb_libbpf,
 	&bench_rb_custom,
 	&bench_pb_libbpf,

@@ -464,4 +460,3 @@ int main(int argc, char **argv)
 
 	return 0;
 }
-

@@ -106,12 +106,6 @@ static void setup_fexit()
 	attach_bpf(ctx.skel->progs.prog5);
 }
 
-static void setup_fmodret()
-{
-	setup_ctx();
-	attach_bpf(ctx.skel->progs.prog6);
-}
-
 static void *consumer(void *input)
 {
 	return NULL;

@@ -182,14 +176,3 @@ const struct bench bench_rename_fexit = {
 	.report_progress = hits_drops_report_progress,
 	.report_final = hits_drops_report_final,
 };
-
-const struct bench bench_rename_fmodret = {
-	.name = "rename-fmodret",
-	.validate = validate,
-	.setup = setup_fmodret,
-	.producer_thread = producer,
-	.consumer_thread = consumer,
-	.measure = measure,
-	.report_progress = hits_drops_report_progress,
-	.report_final = hits_drops_report_final,
-};

@@ -96,12 +96,6 @@ static void trigger_fentry_sleep_setup()
 	attach_bpf(ctx.skel->progs.bench_trigger_fentry_sleep);
 }
 
-static void trigger_fmodret_setup()
-{
-	setup_ctx();
-	attach_bpf(ctx.skel->progs.bench_trigger_fmodret);
-}
-
 static void *trigger_consumer(void *input)
 {
 	return NULL;

@@ -171,14 +165,3 @@ const struct bench bench_trig_fentry_sleep = {
 	.report_progress = hits_drops_report_progress,
 	.report_final = hits_drops_report_final,
 };
-
-const struct bench bench_trig_fmodret = {
-	.name = "trig-fmodret",
-	.validate = trigger_validate,
-	.setup = trigger_fmodret_setup,
-	.producer_thread = trigger_producer,
-	.consumer_thread = trigger_consumer,
-	.measure = trigger_measure,
-	.report_progress = hits_drops_report_progress,
-	.report_final = hits_drops_report_final,
-};

@@ -61,10 +61,9 @@ void test_test_overhead(void)
 	const char *raw_tp_name = "raw_tp/task_rename";
 	const char *fentry_name = "fentry/__set_task_comm";
 	const char *fexit_name = "fexit/__set_task_comm";
-	const char *fmodret_name = "fmod_ret/__set_task_comm";
 	const char *kprobe_func = "__set_task_comm";
 	struct bpf_program *kprobe_prog, *kretprobe_prog, *raw_tp_prog;
-	struct bpf_program *fentry_prog, *fexit_prog, *fmodret_prog;
+	struct bpf_program *fentry_prog, *fexit_prog;
 	struct bpf_object *obj;
 	struct bpf_link *link;
 	int err, duration = 0;

@@ -97,11 +96,6 @@ void test_test_overhead(void)
 	if (CHECK(!fexit_prog, "find_probe",
 		  "prog '%s' not found\n", fexit_name))
 		goto cleanup;
-	fmodret_prog = bpf_object__find_program_by_title(obj, fmodret_name);
-	if (CHECK(!fmodret_prog, "find_probe",
-		  "prog '%s' not found\n", fmodret_name))
-		goto cleanup;
-
 	err = bpf_object__load(obj);
 	if (CHECK(err, "obj_load", "err %d\n", err))
 		goto cleanup;

@@ -148,12 +142,6 @@ void test_test_overhead(void)
 	test_run("fexit");
 	bpf_link__destroy(link);
 
-	/* attach fmod_ret */
-	link = bpf_program__attach_trace(fmodret_prog);
-	if (CHECK(IS_ERR(link), "attach fmod_ret", "err %ld\n", PTR_ERR(link)))
-		goto cleanup;
-	test_run("fmod_ret");
-	bpf_link__destroy(link);
 cleanup:
 	prctl(PR_SET_NAME, comm, 0L, 0L, 0L);
 	bpf_object__close(obj);

@@ -39,10 +39,4 @@ int BPF_PROG(prog5, struct task_struct *tsk, const char *buf, bool exec)
 	return 0;
 }
 
-SEC("fmod_ret/__set_task_comm")
-int BPF_PROG(prog6, struct task_struct *tsk, const char *buf, bool exec)
-{
-	return !tsk;
-}
-
 char _license[] SEC("license") = "GPL";

@@ -45,10 +45,3 @@ int bench_trigger_fentry_sleep(void *ctx)
 	__sync_add_and_fetch(&hits, 1);
 	return 0;
 }
-
-SEC("fmod_ret/__x64_sys_getpgid")
-int bench_trigger_fmodret(void *ctx)
-{
-	__sync_add_and_fetch(&hits, 1);
-	return -22;
-}

@@ -1402,7 +1402,7 @@ int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
 			     struct bpf_reg_state *regs);
 int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
 			  struct bpf_reg_state *reg);
-int btf_check_type_match(struct bpf_verifier_env *env, struct bpf_prog *prog,
+int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *prog,
 			 struct btf *btf, const struct btf_type *t);
 
 struct bpf_prog *bpf_prog_by_id(u32 id);

@@ -347,8 +347,9 @@ static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
 
 static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
 {
-	return (log->level && log->ubuf && !bpf_verifier_log_full(log)) ||
-		log->level == BPF_LOG_KERNEL;
+	return log &&
+		((log->level && log->ubuf && !bpf_verifier_log_full(log)) ||
+		 log->level == BPF_LOG_KERNEL);
 }
 
 #define BPF_MAX_SUBPROGS 256

@@ -4388,7 +4388,7 @@ static int btf_check_func_type_match(struct bpf_verifier_log *log,
 }
 
 /* Compare BTFs of given program with BTF of target program */
-int btf_check_type_match(struct bpf_verifier_env *env, struct bpf_prog *prog,
+int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *prog,
 			 struct btf *btf2, const struct btf_type *t2)
 {
 	struct btf *btf1 = prog->aux->btf;

@@ -4396,7 +4396,7 @@ int btf_check_type_match(struct bpf_verifier_env *env, struct bpf_prog *prog,
 	u32 btf_id = 0;
 
 	if (!prog->aux->func_info) {
-		bpf_log(&env->log, "Program extension requires BTF\n");
+		bpf_log(log, "Program extension requires BTF\n");
 		return -EINVAL;
 	}
 

@@ -4408,7 +4408,7 @@ int btf_check_type_match(struct bpf_verifier_env *env, struct bpf_prog *prog,
 	if (!t1 || !btf_type_is_func(t1))
 		return -EFAULT;
 
-	return btf_check_func_type_match(&env->log, btf1, t1, btf2, t2);
+	return btf_check_func_type_match(log, btf1, t1, btf2, t2);
 }
 
 /* Compare BTF of a function with given bpf_reg_state.

@@ -11220,6 +11220,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 	struct bpf_prog *prog = env->prog;
 	bool prog_extension = prog->type == BPF_PROG_TYPE_EXT;
 	struct bpf_prog *tgt_prog = prog->aux->linked_prog;
+	struct bpf_verifier_log *log = &env->log;
 	u32 btf_id = prog->aux->attach_btf_id;
 	const char prefix[] = "btf_trace_";
 	struct btf_func_model fmodel;

@@ -11247,23 +11248,23 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 		return 0;
 
 	if (!btf_id) {
-		verbose(env, "Tracing programs must provide btf_id\n");
+		bpf_log(log, "Tracing programs must provide btf_id\n");
 		return -EINVAL;
 	}
 	btf = bpf_prog_get_target_btf(prog);
 	if (!btf) {
-		verbose(env,
+		bpf_log(log,
 			"FENTRY/FEXIT program can only be attached to another program annotated with BTF\n");
 		return -EINVAL;
 	}
 	t = btf_type_by_id(btf, btf_id);
 	if (!t) {
-		verbose(env, "attach_btf_id %u is invalid\n", btf_id);
+		bpf_log(log, "attach_btf_id %u is invalid\n", btf_id);
 		return -EINVAL;
 	}
 	tname = btf_name_by_offset(btf, t->name_off);
 	if (!tname) {
-		verbose(env, "attach_btf_id %u doesn't have a name\n", btf_id);
+		bpf_log(log, "attach_btf_id %u doesn't have a name\n", btf_id);
 		return -EINVAL;
 	}
 	if (tgt_prog) {