Merge branch 'bpf_iter-BTF_ID-at-build-time'

Yonghong Song says:

====================
Commit 5a2798ab32ba
("bpf: Add BTF_ID_LIST/BTF_ID/BTF_ID_UNUSED macros")
implemented a mechanism to compute btf_ids at kernel build
time which can simplify kernel implementation and reduce
runtime overhead by removing in-kernel btf_id calculation.

This patch set tried to use this mechanism to compute
btf_ids for bpf_skc_to_*() helpers and for btf_id_or_null ctx
arguments specified during bpf iterator registration.
Please see individual patch for details.

Changelogs:
v1 -> v2:
- v1 ([1]) is only for bpf_skc_to_*() helpers. This version
expanded it to cover ctx btf_id_or_null arguments
- abandoned the change of "extern u32 name[]" to
"static u32 name[]" for BPF_ID_LIST local "name" definition.
gcc 9 incurred a compilation error.

[1]: https://lore.kernel.org/bpf/[e-mail]/T
====================

Signed-off-by: Alexei Starovoitov <[e-mail]>

include/linux/bpf.h

···
 struct bpf_ctx_arg_aux {
 	u32 offset;
 	enum bpf_reg_type reg_type;
+	u32 btf_id;
 };
 
 struct bpf_prog_aux {
···
 
 struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr);
 void bpf_map_offload_map_free(struct bpf_map *map);
-void init_btf_sock_ids(struct btf *btf);
 #else
 static inline int bpf_prog_offload_init(struct bpf_prog *prog,
 					union bpf_attr *attr)
···
 }
 
 static inline void bpf_map_offload_map_free(struct bpf_map *map)
-{
-}
-static inline void init_btf_sock_ids(struct btf *btf)
 {
 }
 #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */

include/linux/btf_ids.h

···
  * .zero 4
  *
  */
-#define __BTF_ID_LIST(name)				\
+#define __BTF_ID_LIST(name, scope)			\
 asm(							\
 ".pushsection " BTF_IDS_SECTION ",\"a\";       \n"	\
-".local " #name ";                             \n"	\
+"." #scope " " #name ";                        \n"	\
 #name ":;                                      \n"	\
 ".popsection;                                  \n");	\
 
 #define BTF_ID_LIST(name)				\
-__BTF_ID_LIST(name)					\
+__BTF_ID_LIST(name, local)				\
 extern u32 name[];
+
+#define BTF_ID_LIST_GLOBAL(name)			\
+__BTF_ID_LIST(name, globl)
 
 /*
  * The BTF_ID_UNUSED macro defines 4 zero bytes.
···
 #define BTF_ID_LIST(name) static u32 name[5];
 #define BTF_ID(prefix, name)
 #define BTF_ID_UNUSED
+#define BTF_ID_LIST_GLOBAL(name) u32 name[1];
 
 #endif /* CONFIG_DEBUG_INFO_BTF */
+
+#ifdef CONFIG_NET
+/* Define a list of socket types which can be the argument for
+ * skc_to_*_sock() helpers. All these sockets should have
+ * sock_common as the first argument in its memory layout.
+ */
+#define BTF_SOCK_TYPE_xxx \
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET, inet_sock)			\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_CONN, inet_connection_sock)	\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_REQ, inet_request_sock)	\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_TW, inet_timewait_sock)	\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_REQ, request_sock)			\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_SOCK, sock)				\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_SOCK_COMMON, sock_common)		\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP, tcp_sock)			\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP_REQ, tcp_request_sock)		\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP_TW, tcp_timewait_sock)		\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP6, tcp6_sock)			\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_UDP, udp_sock)			\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_UDP6, udp6_sock)
+
+enum {
+#define BTF_SOCK_TYPE(name, str) name,
+BTF_SOCK_TYPE_xxx
+#undef BTF_SOCK_TYPE
+MAX_BTF_SOCK_TYPE,
+};
+
+extern u32 btf_sock_ids[];
+#endif
 
 #endif

kernel/bpf/btf.c

···
 		goto errout;
 
 	bpf_struct_ops_init(btf, log);
-	init_btf_sock_ids(btf);
 
 	btf_verifier_env_free(env);
 	refcount_set(&btf->refcnt, 1);
···
 		return true;
 
 	/* this is a pointer to another type */
-	info->reg_type = PTR_TO_BTF_ID;
 	for (i = 0; i < prog->aux->ctx_arg_info_size; i++) {
 		const struct bpf_ctx_arg_aux *ctx_arg_info = &prog->aux->ctx_arg_info[i];
 
 		if (ctx_arg_info->offset == off) {
 			info->reg_type = ctx_arg_info->reg_type;
-			break;
+			info->btf_id = ctx_arg_info->btf_id;
+			return true;
 		}
 	}
 
+	info->reg_type = PTR_TO_BTF_ID;
 	if (tgt_prog) {
 		ret = btf_translate_to_vmlinux(log, btf, t, tgt_prog->type, arg);
 		if (ret > 0) {

kernel/bpf/map_iter.c

···
 #include <linux/fs.h>
 #include <linux/filter.h>
 #include <linux/kernel.h>
+#include <linux/btf_ids.h>
 
 struct bpf_iter_seq_map_info {
 	u32 mid;
···
 	.show	= bpf_map_seq_show,
 };
 
-static const struct bpf_iter_reg bpf_map_reg_info = {
+BTF_ID_LIST(btf_bpf_map_id)
+BTF_ID(struct, bpf_map)
+
+static struct bpf_iter_reg bpf_map_reg_info = {
 	.target			= "bpf_map",
 	.seq_ops		= &bpf_map_seq_ops,
 	.init_seq_private	= NULL,
···
 
 static int __init bpf_map_iter_init(void)
 {
+	bpf_map_reg_info.ctx_arg_info[0].btf_id = *btf_bpf_map_id;
 	return bpf_iter_reg_target(&bpf_map_reg_info);
 }
 

kernel/bpf/task_iter.c

···
 #include <linux/fs.h>
 #include <linux/fdtable.h>
 #include <linux/filter.h>
+#include <linux/btf_ids.h>
 
 struct bpf_iter_seq_task_common {
 	struct pid_namespace *ns;
···
 	.show	= task_file_seq_show,
 };
 
-static const struct bpf_iter_reg task_reg_info = {
+BTF_ID_LIST(btf_task_file_ids)
+BTF_ID(struct, task_struct)
+BTF_ID(struct, file)
+
+static struct bpf_iter_reg task_reg_info = {
 	.target			= "task",
 	.seq_ops		= &task_seq_ops,
 	.init_seq_private	= init_seq_pidns,
···
 	},
 };
 
-static const struct bpf_iter_reg task_file_reg_info = {
+static struct bpf_iter_reg task_file_reg_info = {
 	.target			= "task_file",
 	.seq_ops		= &task_file_seq_ops,
 	.init_seq_private	= init_seq_pidns,
···
 {
 	int ret;
 
+	task_reg_info.ctx_arg_info[0].btf_id = btf_task_file_ids[0];
 	ret = bpf_iter_reg_target(&task_reg_info);
 	if (ret)
 		return ret;
 
+	task_file_reg_info.ctx_arg_info[0].btf_id = btf_task_file_ids[0];
+	task_file_reg_info.ctx_arg_info[1].btf_id = btf_task_file_ids[1];
 	return bpf_iter_reg_target(&task_file_reg_info);
 }
 late_initcall(task_iter_init);

net/core/filter.c

···
 	bpf_dispatcher_change_prog(BPF_DISPATCHER_PTR(xdp), prev_prog, prog);
 }
 
-/* Define a list of socket types which can be the argument for
- * skc_to_*_sock() helpers. All these sockets should have
- * sock_common as the first argument in its memory layout.
- */
-#define BTF_SOCK_TYPE_xxx \
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET, "inet_sock")			\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_CONN, "inet_connection_sock")	\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_REQ, "inet_request_sock")	\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_TW, "inet_timewait_sock")	\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_REQ, "request_sock")		\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_SOCK, "sock")			\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_SOCK_COMMON, "sock_common")		\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP, "tcp_sock")			\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP_REQ, "tcp_request_sock")	\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP_TW, "tcp_timewait_sock")	\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP6, "tcp6_sock")			\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_UDP, "udp_sock")			\
-	BTF_SOCK_TYPE(BTF_SOCK_TYPE_UDP6, "udp6_sock")
-
-enum {
-#define BTF_SOCK_TYPE(name, str) name,
+#ifdef CONFIG_DEBUG_INFO_BTF
+BTF_ID_LIST_GLOBAL(btf_sock_ids)
+#define BTF_SOCK_TYPE(name, type) BTF_ID(struct, type)
 BTF_SOCK_TYPE_xxx
 #undef BTF_SOCK_TYPE
-MAX_BTF_SOCK_TYPE,
-};
-
-static int btf_sock_ids[MAX_BTF_SOCK_TYPE];
-
-#ifdef CONFIG_BPF_SYSCALL
-static const char *bpf_sock_types[] = {
-#define BTF_SOCK_TYPE(name, str) str,
-BTF_SOCK_TYPE_xxx
-#undef BTF_SOCK_TYPE
-};
-
-void init_btf_sock_ids(struct btf *btf)
-{
-	int i, btf_id;
-
-	for (i = 0; i < MAX_BTF_SOCK_TYPE; i++) {
-		btf_id = btf_find_by_name_kind(btf, bpf_sock_types[i],
-					       BTF_KIND_STRUCT);
-		if (btf_id > 0)
-			btf_sock_ids[i] = btf_id;
-	}
-}
+#else
+u32 btf_sock_ids[MAX_BTF_SOCK_TYPE];
 #endif
 
 static bool check_arg_btf_id(u32 btf_id, u32 arg)

net/ipv4/tcp_ipv4.c

···
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 #include <linux/inetdevice.h>
+#include <linux/btf_ids.h>
 
 #include <crypto/hash.h>
 #include <linux/scatterlist.h>
···
 	bpf_iter_fini_seq_net(priv_data);
 }
 
-static const struct bpf_iter_reg tcp_reg_info = {
+static struct bpf_iter_reg tcp_reg_info = {
 	.target			= "tcp",
 	.seq_ops		= &bpf_iter_tcp_seq_ops,
 	.init_seq_private	= bpf_iter_init_tcp,
···
 
 static void __init bpf_iter_register(void)
 {
+	tcp_reg_info.ctx_arg_info[0].btf_id = btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON];
 	if (bpf_iter_reg_target(&tcp_reg_info))
 		pr_warn("Warning: could not register bpf iterator tcp\n");
 }

net/ipv4/udp.c

···
 #include <net/xfrm.h>
 #include <trace/events/udp.h>
 #include <linux/static_key.h>
+#include <linux/btf_ids.h>
 #include <trace/events/skb.h>
 #include <net/busy_poll.h>
 #include "udp_impl.h"
···
 	bpf_iter_fini_seq_net(priv_data);
 }
 
-static const struct bpf_iter_reg udp_reg_info = {
+static struct bpf_iter_reg udp_reg_info = {
 	.target			= "udp",
 	.seq_ops		= &bpf_iter_udp_seq_ops,
 	.init_seq_private	= bpf_iter_init_udp,
···
 
 static void __init bpf_iter_register(void)
 {
+	udp_reg_info.ctx_arg_info[0].btf_id = btf_sock_ids[BTF_SOCK_TYPE_UDP];
 	if (bpf_iter_reg_target(&udp_reg_info))
 		pr_warn("Warning: could not register bpf iterator udp\n");
 }

net/ipv6/route.c

···
 #include <net/l3mdev.h>
 #include <net/ip.h>
 #include <linux/uaccess.h>
+#include <linux/btf_ids.h>
 
 #ifdef CONFIG_SYSCTL
 #include <linux/sysctl.h>
···
 #if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS)
 DEFINE_BPF_ITER_FUNC(ipv6_route, struct bpf_iter_meta *meta, struct fib6_info *rt)
 
-static const struct bpf_iter_reg ipv6_route_reg_info = {
+BTF_ID_LIST(btf_fib6_info_id)
+BTF_ID(struct, fib6_info)
+
+static struct bpf_iter_reg ipv6_route_reg_info = {
 	.target			= "ipv6_route",
 	.seq_ops		= &ipv6_route_seq_ops,
 	.init_seq_private	= bpf_iter_init_seq_net,
···
 
 static int __init bpf_iter_register(void)
 {
+	ipv6_route_reg_info.ctx_arg_info[0].btf_id = *btf_fib6_info_id;
 	return bpf_iter_reg_target(&ipv6_route_reg_info);
 }
 

net/netlink/af_netlink.c

···
 #include <linux/genetlink.h>
 #include <linux/net_namespace.h>
 #include <linux/nospec.h>
+#include <linux/btf_ids.h>
 
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
···
 };
 
 #if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS)
-static const struct bpf_iter_reg netlink_reg_info = {
+BTF_ID_LIST(btf_netlink_sock_id)
+BTF_ID(struct, netlink_sock)
+
+static struct bpf_iter_reg netlink_reg_info = {
 	.target			= "netlink",
 	.seq_ops		= &netlink_seq_ops,
 	.init_seq_private	= bpf_iter_init_seq_net,
···
 
 static int __init bpf_iter_register(void)
 {
+	netlink_reg_info.ctx_arg_info[0].btf_id = *btf_netlink_sock_id;
 	return bpf_iter_reg_target(&netlink_reg_info);
 }
 #endif

tools/include/linux/btf_ids.h

···
 #ifndef _LINUX_BTF_IDS_H
 #define _LINUX_BTF_IDS_H
 
+#ifdef CONFIG_DEBUG_INFO_BTF
+
 #include <linux/compiler.h> /* for __PASTE */
 
 /*
···
 asm(							\
 ".pushsection " BTF_IDS_SECTION ",\"a\";       \n"	\
 ".local " #symbol " ;                          \n"	\
-".type  " #symbol ", @object;                  \n"	\
+".type  " #symbol ", STT_OBJECT;               \n"	\
 ".size  " #symbol ", 4;                        \n"	\
 #symbol ":                                     \n"	\
 ".zero 4                                       \n"	\
···
  * .zero 4
  *
  */
-#define __BTF_ID_LIST(name)				\
+#define __BTF_ID_LIST(name, scope)			\
 asm(							\
 ".pushsection " BTF_IDS_SECTION ",\"a\";       \n"	\
-".local " #name ";                             \n"	\
+"." #scope " " #name ";                        \n"	\
 #name ":;                                      \n"	\
 ".popsection;                                  \n");	\
 
 #define BTF_ID_LIST(name)				\
-__BTF_ID_LIST(name)					\
+__BTF_ID_LIST(name, local)				\
 extern u32 name[];
+
+#define BTF_ID_LIST_GLOBAL(name)			\
+__BTF_ID_LIST(name, globl)
 
 /*
  * The BTF_ID_UNUSED macro defines 4 zero bytes.
···
 ".zero 4                                       \n"	\
 ".popsection;                                  \n");
 
+#else
+
+#define BTF_ID_LIST(name) static u32 name[5];
+#define BTF_ID(prefix, name)
+#define BTF_ID_UNUSED
+#define BTF_ID_LIST_GLOBAL(name) u32 name[1];
+
+#endif /* CONFIG_DEBUG_INFO_BTF */
+
+#ifdef CONFIG_NET
+/* Define a list of socket types which can be the argument for
+ * skc_to_*_sock() helpers. All these sockets should have
+ * sock_common as the first argument in its memory layout.
+ */
+#define BTF_SOCK_TYPE_xxx \
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET, inet_sock)			\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_CONN, inet_connection_sock)	\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_REQ, inet_request_sock)	\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_INET_TW, inet_timewait_sock)	\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_REQ, request_sock)			\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_SOCK, sock)				\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_SOCK_COMMON, sock_common)		\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP, tcp_sock)			\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP_REQ, tcp_request_sock)		\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP_TW, tcp_timewait_sock)		\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_TCP6, tcp6_sock)			\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_UDP, udp_sock)			\
+	BTF_SOCK_TYPE(BTF_SOCK_TYPE_UDP6, udp6_sock)
+
+enum {
+#define BTF_SOCK_TYPE(name, str) name,
+BTF_SOCK_TYPE_xxx
+#undef BTF_SOCK_TYPE
+MAX_BTF_SOCK_TYPE,
+};
+
+extern u32 btf_sock_ids[];
+#endif
 
 #endif

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

···
 #include <bpf/libbpf.h>
 #include <linux/btf.h>
 #include <linux/kernel.h>
+#define CONFIG_DEBUG_INFO_BTF
 #include <linux/btf_ids.h>
 #include "test_progs.h"
 
···
 	{ "func",    BTF_KIND_FUNC,    -1 },
 };
 
-BTF_ID_LIST(test_list)
+BTF_ID_LIST(test_list_local)
+BTF_ID_UNUSED
+BTF_ID(typedef, S)
+BTF_ID(typedef, T)
+BTF_ID(typedef, U)
+BTF_ID(struct,  S)
+BTF_ID(union,   U)
+BTF_ID(func,    func)
+
+extern __u32 test_list_global[];
+BTF_ID_LIST_GLOBAL(test_list_global)
 BTF_ID_UNUSED
 BTF_ID(typedef, S)
 BTF_ID(typedef, T)
···
 
 int test_resolve_btfids(void)
 {
-	unsigned int i;
+	__u32 *test_list, *test_lists[] = { test_list_local, test_list_global };
+	unsigned int i, j;
 	int ret = 0;
 
 	if (resolve_symbols())
 		return -1;
 
-	/* Check BTF_ID_LIST(test_list) IDs */
-	for (i = 0; i < ARRAY_SIZE(test_symbols) && !ret; i++) {
-		ret = CHECK(test_list[i] != test_symbols[i].id,
-			    "id_check",
-			    "wrong ID for %s (%d != %d)\n", test_symbols[i].name,
-			    test_list[i], test_symbols[i].id);
+	/* Check BTF_ID_LIST(test_list_local) and
+	 * BTF_ID_LIST_GLOBAL(test_list_global) IDs
+	 */
+	for (j = 0; j < ARRAY_SIZE(test_lists); j++) {
+		test_list = test_lists[j];
+		for (i = 0; i < ARRAY_SIZE(test_symbols) && !ret; i++) {
+			ret = CHECK(test_list[i] != test_symbols[i].id,
+				    "id_check",
+				    "wrong ID for %s (%d != %d)\n",
+				    test_symbols[i].name,
+				    test_list[i], test_symbols[i].id);
+		}
 	}
 
 	return ret;