Merge branch 'bpf: expose bpf_{g,s}et_retval to more cgroup hooks'

Stanislav Fomichev says:

====================

Apparently, only a small subset of cgroup hooks actually falls
back to cgroup_base_func_proto. This leads to unexpected result
where not all cgroup helpers have bpf_{g,s}et_retval.

It's getting harder and harder to manage which helpers are exported
to which hooks. We now have the following call chains:

- cg_skb_func_proto
  - sk_filter_func_proto
    - bpf_sk_base_func_proto
      - bpf_base_func_proto

So by looking at cg_skb_func_proto it's pretty hard to understand
what's going on.

For cgroup helpers, I'm proposing we do the following instead:

  func_proto = cgroup_common_func_proto();
  if (func_proto) return func_proto;

  /* optional, if hook has 'current' */
  func_proto = cgroup_current_func_proto();
  if (func_proto) return func_proto;

  ...

  switch (func_id) {
  /* hook specific helpers */
  case BPF_FUNC_hook_specific_helper:
    return &xyz;
  default:
    /* always fall back to plain bpf_base_func_proto */
    bpf_base_func_proto(func_id);
  }

If this turns out more workable, we can follow up with converting
the rest to the same pattern.

v5:
- remove net/cls_cgroup.h include from patch 1/5 (Martin)
- move endif changes from patch 1/5 to 3/5 (Martin)
- don't define __weak protos, the ones in core.c suffice (Martin)

v4:
- don't touch existing helper.c helpers (Martin)
- drop unneeded CONFIG_CGROUP_BPF in bpf_lsm_func_proto (Martin)

v3:
- expose strtol/strtoul everywhere (Martin)
- move helpers declarations from bpf.h to bpf-cgroup.h (Martin)
- revise bpf_{g,s}et_retval documentation (Martin)
- don't expose bpf_{g,s}et_retval to cg_skb hooks (Martin)

v2:
- move everything into kernel/bpf/cgroup.c instead (Martin)
- use cgroup_common_func_proto in lsm (Martin)
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf-cgroup.h

@@ -414,6 +414,11 @@ int cgroup_bpf_prog_detach(const union bpf_attr *attr,
 int cgroup_bpf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);
 int cgroup_bpf_prog_query(const union bpf_attr *attr,
 			  union bpf_attr __user *uattr);
+
+const struct bpf_func_proto *
+cgroup_common_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog);
+const struct bpf_func_proto *
+cgroup_current_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog);
 #else
 
 static inline int cgroup_bpf_inherit(struct cgroup *cgrp) { return 0; }
@@ -444,6 +449,18 @@ static inline int cgroup_bpf_prog_query(const union bpf_attr *attr,
 	return -EINVAL;
 }
 
+static inline const struct bpf_func_proto *
+cgroup_common_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+	return NULL;
+}
+
+static inline const struct bpf_func_proto *
+cgroup_current_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+	return NULL;
+}
+
 static inline int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux,
 					    struct bpf_map *map) { return 0; }
 static inline struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(

include/linux/bpf.h

@@ -2375,6 +2375,7 @@ extern const struct bpf_func_proto bpf_sock_map_update_proto;
 extern const struct bpf_func_proto bpf_sock_hash_update_proto;
 extern const struct bpf_func_proto bpf_get_current_cgroup_id_proto;
 extern const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto;
+extern const struct bpf_func_proto bpf_get_cgroup_classid_curr_proto;
 extern const struct bpf_func_proto bpf_msg_redirect_hash_proto;
 extern const struct bpf_func_proto bpf_msg_redirect_map_proto;
 extern const struct bpf_func_proto bpf_sk_redirect_hash_proto;

include/uapi/linux/bpf.h

@@ -5085,17 +5085,29 @@ union bpf_attr {
  *
  * int bpf_get_retval(void)
  *	Description
- *		Get the syscall's return value that will be returned to userspace.
+ *		Get the BPF program's return value that will be returned to the upper layers.
  *
- *		This helper is currently supported by cgroup programs only.
+ *		This helper is currently supported by cgroup programs and only by the hooks
+ *		where BPF program's return value is returned to the userspace via errno.
  *	Return
- *		The syscall's return value.
+ *		The BPF program's return value.
  *
  * int bpf_set_retval(int retval)
  *	Description
- *		Set the syscall's return value that will be returned to userspace.
+ *		Set the BPF program's return value that will be returned to the upper layers.
+ *
+ *		This helper is currently supported by cgroup programs and only by the hooks
+ *		where BPF program's return value is returned to the userspace via errno.
+ *
+ *		Note that there is the following corner case where the program exports an error
+ *		via bpf_set_retval but signals success via 'return 1':
+ *
+ *			bpf_set_retval(-EPERM);
+ *			return 1;
+ *
+ *		In this case, the BPF program's return value will use helper's -EPERM. This
+ *		still holds true for cgroup/bind{4,6} which supports extra 'return 3' success case.
  *
- *		This helper is currently supported by cgroup programs only.
  *	Return
  *		0 on success, or a negative error in case of failure.
  *

kernel/bpf/bpf_lsm.c

@@ -189,6 +189,14 @@ static const struct bpf_func_proto bpf_get_attach_cookie_proto = {
 static const struct bpf_func_proto *
 bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
+	const struct bpf_func_proto *func_proto;
+
+	if (prog->expected_attach_type == BPF_LSM_CGROUP) {
+		func_proto = cgroup_common_func_proto(func_id, prog);
+		if (func_proto)
+			return func_proto;
+	}
+
 	switch (func_id) {
 	case BPF_FUNC_inode_storage_get:
 		return &bpf_inode_storage_get_proto;
@@ -212,15 +220,6 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return prog->aux->sleepable ? &bpf_ima_file_hash_proto : NULL;
 	case BPF_FUNC_get_attach_cookie:
 		return bpf_prog_has_trampoline(prog) ? &bpf_get_attach_cookie_proto : NULL;
-	case BPF_FUNC_get_local_storage:
-		return prog->expected_attach_type == BPF_LSM_CGROUP ?
-			&bpf_get_local_storage_proto : NULL;
-	case BPF_FUNC_set_retval:
-		return prog->expected_attach_type == BPF_LSM_CGROUP ?
-			&bpf_set_retval_proto : NULL;
-	case BPF_FUNC_get_retval:
-		return prog->expected_attach_type == BPF_LSM_CGROUP ?
-			&bpf_get_retval_proto : NULL;
 #ifdef CONFIG_NET
 	case BPF_FUNC_setsockopt:
 		if (prog->expected_attach_type != BPF_LSM_CGROUP)

kernel/bpf/cgroup.c

@@ -1527,6 +1527,37 @@ int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,
 	return ret;
 }
 
+BPF_CALL_2(bpf_get_local_storage, struct bpf_map *, map, u64, flags)
+{
+	/* flags argument is not used now,
+	 * but provides an ability to extend the API.
+	 * verifier checks that its value is correct.
+	 */
+	enum bpf_cgroup_storage_type stype = cgroup_storage_type(map);
+	struct bpf_cgroup_storage *storage;
+	struct bpf_cg_run_ctx *ctx;
+	void *ptr;
+
+	/* get current cgroup storage from BPF run context */
+	ctx = container_of(current->bpf_ctx, struct bpf_cg_run_ctx, run_ctx);
+	storage = ctx->prog_item->cgroup_storage[stype];
+
+	if (stype == BPF_CGROUP_STORAGE_SHARED)
+		ptr = &READ_ONCE(storage->buf)->data[0];
+	else
+		ptr = this_cpu_ptr(storage->percpu_buf);
+
+	return (unsigned long)ptr;
+}
+
+const struct bpf_func_proto bpf_get_local_storage_proto = {
+	.func		= bpf_get_local_storage,
+	.gpl_only	= false,
+	.ret_type	= RET_PTR_TO_MAP_VALUE,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_ANYTHING,
+};
+
 BPF_CALL_0(bpf_get_retval)
 {
 	struct bpf_cg_run_ctx *ctx =
@@ -1558,32 +1589,26 @@ const struct bpf_func_proto bpf_set_retval_proto = {
 };
 
 static const struct bpf_func_proto *
-cgroup_base_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+cgroup_dev_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
+	const struct bpf_func_proto *func_proto;
+
+	func_proto = cgroup_common_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
+	func_proto = cgroup_current_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
 	switch (func_id) {
-	case BPF_FUNC_get_current_uid_gid:
-		return &bpf_get_current_uid_gid_proto;
-	case BPF_FUNC_get_local_storage:
-		return &bpf_get_local_storage_proto;
-	case BPF_FUNC_get_current_cgroup_id:
-		return &bpf_get_current_cgroup_id_proto;
 	case BPF_FUNC_perf_event_output:
 		return &bpf_event_output_data_proto;
-	case BPF_FUNC_get_retval:
-		return &bpf_get_retval_proto;
-	case BPF_FUNC_set_retval:
-		return &bpf_set_retval_proto;
 	default:
 		return bpf_base_func_proto(func_id);
 	}
 }
 
-static const struct bpf_func_proto *
-cgroup_dev_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
-{
-	return cgroup_base_func_proto(func_id, prog);
-}
-
 static bool cgroup_dev_is_valid_access(int off, int size,
 				       enum bpf_access_type type,
 				       const struct bpf_prog *prog,
@@ -2096,11 +2121,17 @@ static const struct bpf_func_proto bpf_sysctl_set_new_value_proto = {
 static const struct bpf_func_proto *
 sysctl_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
+	const struct bpf_func_proto *func_proto;
+
+	func_proto = cgroup_common_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
+	func_proto = cgroup_current_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
 	switch (func_id) {
-	case BPF_FUNC_strtol:
-		return &bpf_strtol_proto;
-	case BPF_FUNC_strtoul:
-		return &bpf_strtoul_proto;
 	case BPF_FUNC_sysctl_get_name:
 		return &bpf_sysctl_get_name_proto;
 	case BPF_FUNC_sysctl_get_current_value:
@@ -2111,8 +2142,10 @@ sysctl_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_sysctl_set_new_value_proto;
 	case BPF_FUNC_ktime_get_coarse_ns:
 		return &bpf_ktime_get_coarse_ns_proto;
+	case BPF_FUNC_perf_event_output:
+		return &bpf_event_output_data_proto;
 	default:
-		return cgroup_base_func_proto(func_id, prog);
+		return bpf_base_func_proto(func_id);
 	}
 }
 
@@ -2233,6 +2266,16 @@ static const struct bpf_func_proto bpf_get_netns_cookie_sockopt_proto = {
 static const struct bpf_func_proto *
 cg_sockopt_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
+	const struct bpf_func_proto *func_proto;
+
+	func_proto = cgroup_common_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
+	func_proto = cgroup_current_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
 	switch (func_id) {
 #ifdef CONFIG_NET
 	case BPF_FUNC_get_netns_cookie:
@@ -2254,8 +2297,10 @@ cg_sockopt_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_tcp_sock:
 		return &bpf_tcp_sock_proto;
 #endif
+	case BPF_FUNC_perf_event_output:
+		return &bpf_event_output_data_proto;
 	default:
-		return cgroup_base_func_proto(func_id, prog);
+		return bpf_base_func_proto(func_id);
 	}
 }
 
@@ -2420,3 +2465,69 @@ const struct bpf_verifier_ops cg_sockopt_verifier_ops = {
 
 const struct bpf_prog_ops cg_sockopt_prog_ops = {
 };
+
+/* Common helpers for cgroup hooks. */
+const struct bpf_func_proto *
+cgroup_common_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+	switch (func_id) {
+	case BPF_FUNC_get_local_storage:
+		return &bpf_get_local_storage_proto;
+	case BPF_FUNC_get_retval:
+		switch (prog->expected_attach_type) {
+		case BPF_CGROUP_INET_INGRESS:
+		case BPF_CGROUP_INET_EGRESS:
+		case BPF_CGROUP_SOCK_OPS:
+		case BPF_CGROUP_UDP4_RECVMSG:
+		case BPF_CGROUP_UDP6_RECVMSG:
+		case BPF_CGROUP_INET4_GETPEERNAME:
+		case BPF_CGROUP_INET6_GETPEERNAME:
+		case BPF_CGROUP_INET4_GETSOCKNAME:
+		case BPF_CGROUP_INET6_GETSOCKNAME:
+			return NULL;
+		default:
+			return &bpf_get_retval_proto;
+		}
+	case BPF_FUNC_set_retval:
+		switch (prog->expected_attach_type) {
+		case BPF_CGROUP_INET_INGRESS:
+		case BPF_CGROUP_INET_EGRESS:
+		case BPF_CGROUP_SOCK_OPS:
+		case BPF_CGROUP_UDP4_RECVMSG:
+		case BPF_CGROUP_UDP6_RECVMSG:
+		case BPF_CGROUP_INET4_GETPEERNAME:
+		case BPF_CGROUP_INET6_GETPEERNAME:
+		case BPF_CGROUP_INET4_GETSOCKNAME:
+		case BPF_CGROUP_INET6_GETSOCKNAME:
+			return NULL;
+		default:
+			return &bpf_set_retval_proto;
+		}
+	default:
+		return NULL;
+	}
+}
+
+/* Common helpers for cgroup hooks with valid process context. */
+const struct bpf_func_proto *
+cgroup_current_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+	switch (func_id) {
+	case BPF_FUNC_get_current_uid_gid:
+		return &bpf_get_current_uid_gid_proto;
+	case BPF_FUNC_get_current_pid_tgid:
+		return &bpf_get_current_pid_tgid_proto;
+	case BPF_FUNC_get_current_comm:
+		return &bpf_get_current_comm_proto;
+	case BPF_FUNC_get_current_cgroup_id:
+		return &bpf_get_current_cgroup_id_proto;
+	case BPF_FUNC_get_current_ancestor_cgroup_id:
+		return &bpf_get_current_ancestor_cgroup_id_proto;
+#ifdef CONFIG_CGROUP_NET_CLASSID
+	case BPF_FUNC_get_cgroup_classid:
+		return &bpf_get_cgroup_classid_curr_proto;
+#endif
+	default:
+		return NULL;
+	}
+}

kernel/bpf/helpers.c

@@ -427,40 +427,7 @@ const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto = {
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_ANYTHING,
 };
-
-#ifdef CONFIG_CGROUP_BPF
-
-BPF_CALL_2(bpf_get_local_storage, struct bpf_map *, map, u64, flags)
-{
-	/* flags argument is not used now,
-	 * but provides an ability to extend the API.
-	 * verifier checks that its value is correct.
-	 */
-	enum bpf_cgroup_storage_type stype = cgroup_storage_type(map);
-	struct bpf_cgroup_storage *storage;
-	struct bpf_cg_run_ctx *ctx;
-	void *ptr;
-
-	/* get current cgroup storage from BPF run context */
-	ctx = container_of(current->bpf_ctx, struct bpf_cg_run_ctx, run_ctx);
-	storage = ctx->prog_item->cgroup_storage[stype];
-
-	if (stype == BPF_CGROUP_STORAGE_SHARED)
-		ptr = &READ_ONCE(storage->buf)->data[0];
-	else
-		ptr = this_cpu_ptr(storage->percpu_buf);
-
-	return (unsigned long)ptr;
-}
-
-const struct bpf_func_proto bpf_get_local_storage_proto = {
-	.func		= bpf_get_local_storage,
-	.gpl_only	= false,
-	.ret_type	= RET_PTR_TO_MAP_VALUE,
-	.arg1_type	= ARG_CONST_MAP_PTR,
-	.arg2_type	= ARG_ANYTHING,
-};
-#endif
+#endif /* CONFIG_CGROUPS */
 
 #define BPF_STRTOX_BASE_MASK 0x1F
 
@@ -589,7 +556,6 @@ const struct bpf_func_proto bpf_strtoul_proto = {
 	.arg3_type	= ARG_ANYTHING,
 	.arg4_type	= ARG_PTR_TO_LONG,
 };
-#endif
 
 BPF_CALL_3(bpf_strncmp, const char *, s1, u32, s1_sz, const char *, s2)
 {
@@ -1653,6 +1619,10 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 		return &bpf_loop_proto;
 	case BPF_FUNC_strncmp:
 		return &bpf_strncmp_proto;
+	case BPF_FUNC_strtol:
+		return &bpf_strtol_proto;
+	case BPF_FUNC_strtoul:
+		return &bpf_strtoul_proto;
 	case BPF_FUNC_dynptr_from_mem:
 		return &bpf_dynptr_from_mem_proto;
 	case BPF_FUNC_dynptr_read:

net/core/filter.c

@@ -3009,7 +3009,7 @@ BPF_CALL_0(bpf_get_cgroup_classid_curr)
 	return __task_get_classid(current);
 }
 
-static const struct bpf_func_proto bpf_get_cgroup_classid_curr_proto = {
+const struct bpf_func_proto bpf_get_cgroup_classid_curr_proto = {
 	.func		= bpf_get_cgroup_classid_curr,
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
@@ -7581,34 +7581,23 @@ const struct bpf_func_proto bpf_sk_storage_get_cg_sock_proto __weak;
 static const struct bpf_func_proto *
 sock_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
+	const struct bpf_func_proto *func_proto;
+
+	func_proto = cgroup_common_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
+	func_proto = cgroup_current_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
 	switch (func_id) {
-	/* inet and inet6 sockets are created in a process
-	 * context so there is always a valid uid/gid
-	 */
-	case BPF_FUNC_get_current_uid_gid:
-		return &bpf_get_current_uid_gid_proto;
-	case BPF_FUNC_get_local_storage:
-		return &bpf_get_local_storage_proto;
 	case BPF_FUNC_get_socket_cookie:
 		return &bpf_get_socket_cookie_sock_proto;
 	case BPF_FUNC_get_netns_cookie:
 		return &bpf_get_netns_cookie_sock_proto;
 	case BPF_FUNC_perf_event_output:
 		return &bpf_event_output_data_proto;
-	case BPF_FUNC_get_current_pid_tgid:
-		return &bpf_get_current_pid_tgid_proto;
-	case BPF_FUNC_get_current_comm:
-		return &bpf_get_current_comm_proto;
-#ifdef CONFIG_CGROUPS
-	case BPF_FUNC_get_current_cgroup_id:
-		return &bpf_get_current_cgroup_id_proto;
-	case BPF_FUNC_get_current_ancestor_cgroup_id:
-		return &bpf_get_current_ancestor_cgroup_id_proto;
-#endif
-#ifdef CONFIG_CGROUP_NET_CLASSID
-	case BPF_FUNC_get_cgroup_classid:
-		return &bpf_get_cgroup_classid_curr_proto;
-#endif
 	case BPF_FUNC_sk_storage_get:
 		return &bpf_sk_storage_get_cg_sock_proto;
 	case BPF_FUNC_ktime_get_coarse_ns:
@@ -7621,12 +7610,17 @@ sock_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 static const struct bpf_func_proto *
 sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
+	const struct bpf_func_proto *func_proto;
+
+	func_proto = cgroup_common_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
+	func_proto = cgroup_current_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
 	switch (func_id) {
-	/* inet and inet6 sockets are created in a process
-	 * context so there is always a valid uid/gid
-	 */
-	case BPF_FUNC_get_current_uid_gid:
-		return &bpf_get_current_uid_gid_proto;
 	case BPF_FUNC_bind:
 		switch (prog->expected_attach_type) {
 		case BPF_CGROUP_INET4_CONNECT:
@@ -7639,24 +7633,8 @@ sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_get_socket_cookie_sock_addr_proto;
 	case BPF_FUNC_get_netns_cookie:
 		return &bpf_get_netns_cookie_sock_addr_proto;
-	case BPF_FUNC_get_local_storage:
-		return &bpf_get_local_storage_proto;
 	case BPF_FUNC_perf_event_output:
 		return &bpf_event_output_data_proto;
-	case BPF_FUNC_get_current_pid_tgid:
-		return &bpf_get_current_pid_tgid_proto;
-	case BPF_FUNC_get_current_comm:
-		return &bpf_get_current_comm_proto;
-#ifdef CONFIG_CGROUPS
-	case BPF_FUNC_get_current_cgroup_id:
-		return &bpf_get_current_cgroup_id_proto;
-	case BPF_FUNC_get_current_ancestor_cgroup_id:
-		return &bpf_get_current_ancestor_cgroup_id_proto;
-#endif
-#ifdef CONFIG_CGROUP_NET_CLASSID
-	case BPF_FUNC_get_cgroup_classid:
-		return &bpf_get_cgroup_classid_curr_proto;
-#endif
 #ifdef CONFIG_INET
 	case BPF_FUNC_sk_lookup_tcp:
 		return &bpf_sock_addr_sk_lookup_tcp_proto;
@@ -7737,9 +7715,13 @@ const struct bpf_func_proto bpf_sk_storage_delete_proto __weak;
 static const struct bpf_func_proto *
 cg_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
+	const struct bpf_func_proto *func_proto;
+
+	func_proto = cgroup_common_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
 	switch (func_id) {
-	case BPF_FUNC_get_local_storage:
-		return &bpf_get_local_storage_proto;
 	case BPF_FUNC_sk_fullsock:
 		return &bpf_sk_fullsock_proto;
 	case BPF_FUNC_sk_storage_get:
@@ -7979,6 +7961,12 @@ const struct bpf_func_proto bpf_sock_hash_update_proto __weak;
 static const struct bpf_func_proto *
 sock_ops_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
+	const struct bpf_func_proto *func_proto;
+
+	func_proto = cgroup_common_func_proto(func_id, prog);
+	if (func_proto)
+		return func_proto;
+
 	switch (func_id) {
 	case BPF_FUNC_setsockopt:
 		return &bpf_sock_ops_setsockopt_proto;
@@ -7992,8 +7980,6 @@ sock_ops_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_sock_hash_update_proto;
 	case BPF_FUNC_get_socket_cookie:
 		return &bpf_get_socket_cookie_sock_ops_proto;
-	case BPF_FUNC_get_local_storage:
-		return &bpf_get_local_storage_proto;
 	case BPF_FUNC_perf_event_output:
 		return &bpf_event_output_data_proto;
 	case BPF_FUNC_sk_storage_get:

tools/include/uapi/linux/bpf.h

@@ -5085,17 +5085,29 @@ union bpf_attr {
  *
  * int bpf_get_retval(void)
  *	Description
- *		Get the syscall's return value that will be returned to userspace.
+ *		Get the BPF program's return value that will be returned to the upper layers.
  *
- *		This helper is currently supported by cgroup programs only.
+ *		This helper is currently supported by cgroup programs and only by the hooks
+ *		where BPF program's return value is returned to the userspace via errno.
  *	Return
- *		The syscall's return value.
+ *		The BPF program's return value.
  *
  * int bpf_set_retval(int retval)
  *	Description
- *		Set the syscall's return value that will be returned to userspace.
+ *		Set the BPF program's return value that will be returned to the upper layers.
+ *
+ *		This helper is currently supported by cgroup programs and only by the hooks
+ *		where BPF program's return value is returned to the userspace via errno.
+ *
+ *		Note that there is the following corner case where the program exports an error
+ *		via bpf_set_retval but signals success via 'return 1':
+ *
+ *			bpf_set_retval(-EPERM);
+ *			return 1;
+ *
+ *		In this case, the BPF program's return value will use helper's -EPERM. This
+ *		still holds true for cgroup/bind{4,6} which supports extra 'return 3' success case.
  *
- *		This helper is currently supported by cgroup programs only.
  *	Return
  *		0 on success, or a negative error in case of failure.
  *

tools/testing/selftests/bpf/Makefile

@@ -323,6 +323,7 @@ $(OUTPUT)/test_l4lb_noinline.o: BPF_CFLAGS += -fno-inline
 $(OUTPUT)/test_xdp_noinline.o: BPF_CFLAGS += -fno-inline
 
 $(OUTPUT)/flow_dissector_load.o: flow_dissector_load.h
+$(OUTPUT)/cgroup_getset_retval_hooks.o: cgroup_getset_retval_hooks.h
 
 # Build BPF object using Clang
 # $1 - input .c file

tools/testing/selftests/bpf/cgroup_getset_retval_hooks.h

+/* SPDX-License-Identifier: GPL-2.0 */
+
+BPF_RETVAL_HOOK(ingress, "cgroup_skb/ingress", __sk_buff, -EINVAL)
+BPF_RETVAL_HOOK(egress, "cgroup_skb/egress", __sk_buff, -EINVAL)
+BPF_RETVAL_HOOK(sock_create, "cgroup/sock_create", bpf_sock, 0)
+BPF_RETVAL_HOOK(sock_ops, "sockops", bpf_sock_ops, -EINVAL)
+BPF_RETVAL_HOOK(dev, "cgroup/dev", bpf_cgroup_dev_ctx, 0)
+BPF_RETVAL_HOOK(bind4, "cgroup/bind4", bpf_sock_addr, 0)
+BPF_RETVAL_HOOK(bind6, "cgroup/bind6", bpf_sock_addr, 0)
+BPF_RETVAL_HOOK(connect4, "cgroup/connect4", bpf_sock_addr, 0)
+BPF_RETVAL_HOOK(connect6, "cgroup/connect6", bpf_sock_addr, 0)
+BPF_RETVAL_HOOK(post_bind4, "cgroup/post_bind4", bpf_sock_addr, 0)
+BPF_RETVAL_HOOK(post_bind6, "cgroup/post_bind6", bpf_sock_addr, 0)
+BPF_RETVAL_HOOK(sendmsg4, "cgroup/sendmsg4", bpf_sock_addr, 0)
+BPF_RETVAL_HOOK(sendmsg6, "cgroup/sendmsg6", bpf_sock_addr, 0)
+BPF_RETVAL_HOOK(sysctl, "cgroup/sysctl", bpf_sysctl, 0)
+BPF_RETVAL_HOOK(recvmsg4, "cgroup/recvmsg4", bpf_sock_addr, -EINVAL)
+BPF_RETVAL_HOOK(recvmsg6, "cgroup/recvmsg6", bpf_sock_addr, -EINVAL)
+BPF_RETVAL_HOOK(getsockopt, "cgroup/getsockopt", bpf_sockopt, 0)
+BPF_RETVAL_HOOK(setsockopt, "cgroup/setsockopt", bpf_sockopt, 0)
+BPF_RETVAL_HOOK(getpeername4, "cgroup/getpeername4", bpf_sock_addr, -EINVAL)
+BPF_RETVAL_HOOK(getpeername6, "cgroup/getpeername6", bpf_sock_addr, -EINVAL)
+BPF_RETVAL_HOOK(getsockname4, "cgroup/getsockname4", bpf_sock_addr, -EINVAL)
+BPF_RETVAL_HOOK(getsockname6, "cgroup/getsockname6", bpf_sock_addr, -EINVAL)
+BPF_RETVAL_HOOK(sock_release, "cgroup/sock_release", bpf_sock, 0)

tools/testing/selftests/bpf/prog_tests/cgroup_getset_retval.c

@@ -10,6 +10,7 @@
 
 #include "cgroup_getset_retval_setsockopt.skel.h"
 #include "cgroup_getset_retval_getsockopt.skel.h"
+#include "cgroup_getset_retval_hooks.skel.h"
 
 #define SOL_CUSTOM	0xdeadbeef
 
@@ -433,6 +434,50 @@ static void test_getsockopt_retval_sync(int cgroup_fd, int sock_fd)
 	cgroup_getset_retval_getsockopt__destroy(obj);
 }
 
+struct exposed_hook {
+	const char *name;
+	int expected_err;
+} exposed_hooks[] = {
+
+#define BPF_RETVAL_HOOK(NAME, SECTION, CTX, EXPECTED_ERR) \
+	{ \
+		.name = #NAME, \
+		.expected_err = EXPECTED_ERR, \
+	},
+
+#include "cgroup_getset_retval_hooks.h"
+
+#undef BPF_RETVAL_HOOK
+};
+
+static void test_exposed_hooks(int cgroup_fd, int sock_fd)
+{
+	struct cgroup_getset_retval_hooks *skel;
+	struct bpf_program *prog;
+	int err;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(exposed_hooks); i++) {
+		skel = cgroup_getset_retval_hooks__open();
+		if (!ASSERT_OK_PTR(skel, "cgroup_getset_retval_hooks__open"))
+			continue;
+
+		prog = bpf_object__find_program_by_name(skel->obj, exposed_hooks[i].name);
+		if (!ASSERT_NEQ(prog, NULL, "bpf_object__find_program_by_name"))
+			goto close_skel;
+
+		err = bpf_program__set_autoload(prog, true);
+		if (!ASSERT_OK(err, "bpf_program__set_autoload"))
+			goto close_skel;
+
+		err = cgroup_getset_retval_hooks__load(skel);
+		ASSERT_EQ(err, exposed_hooks[i].expected_err, "expected_err");
+
+close_skel:
+		cgroup_getset_retval_hooks__destroy(skel);
+	}
+}
+
 void test_cgroup_getset_retval(void)
 {
 	int cgroup_fd = -1;
@@ -476,6 +521,9 @@ void test_cgroup_getset_retval(void)
 	if (test__start_subtest("getsockopt-retval_sync"))
 		test_getsockopt_retval_sync(cgroup_fd, sock_fd);
 
+	if (test__start_subtest("exposed_hooks"))
+		test_exposed_hooks(cgroup_fd, sock_fd);
+
 close_fd:
 	close(cgroup_fd);
 }

tools/testing/selftests/bpf/progs/cgroup_getset_retval_hooks.c

+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+#define BPF_RETVAL_HOOK(name, section, ctx, expected_err) \
+	__attribute__((__section__("?" section))) \
+	int name(struct ctx *_ctx) \
+	{ \
+		bpf_set_retval(bpf_get_retval()); \
+		return 1; \
+	}
+
+#include "cgroup_getset_retval_hooks.h"
+
+#undef BPF_RETVAL_HOOK