bpf: Compute map_btf_id during build time

For now, the field 'map_btf_id' in 'struct bpf_map_ops' for all map
types are computed during vmlinux-btf init:

  btf_parse_vmlinux() -> btf_vmlinux_map_ids_init()

It will lookup the btf_type according to the 'map_btf_name' field in
'struct bpf_map_ops'. This process can be done during build time,
thanks to Jiri's resolve_btfids.

selftest of map_ptr has passed:

  $96 map_ptr:OK
  Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Reported-by: kernel test robot <[email protected]>
Signed-off-by: Menglong Dong <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: menglongdong

include/linux/bpf.h

@@ -148,8 +148,7 @@ struct bpf_map_ops {
 				     bpf_callback_t callback_fn,
 				     void *callback_ctx, u64 flags);
 
-	/* BTF name and id of struct allocated by map_alloc */
-	const char * const map_btf_name;
+	/* BTF id of struct allocated by map_alloc */
 	int *map_btf_id;
 
 	/* bpf_iter info used to open a seq_file */

kernel/bpf/arraymap.c

@@ -11,6 +11,7 @@
 #include <linux/perf_event.h>
 #include <uapi/linux/btf.h>
 #include <linux/rcupdate_trace.h>
+#include <linux/btf_ids.h>
 
 #include "map_in_map.h"
 
@@ -690,7 +691,7 @@ static int bpf_for_each_array_elem(struct bpf_map *map, bpf_callback_t callback_
 	return num_elems;
 }
 
-static int array_map_btf_id;
+BTF_ID_LIST_SINGLE(array_map_btf_ids, struct, bpf_array)
 const struct bpf_map_ops array_map_ops = {
 	.map_meta_equal = array_map_meta_equal,
 	.map_alloc_check = array_map_alloc_check,
@@ -711,12 +712,10 @@ const struct bpf_map_ops array_map_ops = {
 	.map_update_batch = generic_map_update_batch,
 	.map_set_for_each_callback_args = map_set_for_each_callback_args,
 	.map_for_each_callback = bpf_for_each_array_elem,
-	.map_btf_name = "bpf_array",
-	.map_btf_id = &array_map_btf_id,
+	.map_btf_id = &array_map_btf_ids[0],
 	.iter_seq_info = &iter_seq_info,
 };
 
-static int percpu_array_map_btf_id;
 const struct bpf_map_ops percpu_array_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc_check = array_map_alloc_check,
@@ -732,8 +731,7 @@ const struct bpf_map_ops percpu_array_map_ops = {
 	.map_update_batch = generic_map_update_batch,
 	.map_set_for_each_callback_args = map_set_for_each_callback_args,
 	.map_for_each_callback = bpf_for_each_array_elem,
-	.map_btf_name = "bpf_array",
-	.map_btf_id = &percpu_array_map_btf_id,
+	.map_btf_id = &array_map_btf_ids[0],
 	.iter_seq_info = &iter_seq_info,
 };
 
@@ -1112,7 +1110,6 @@ static void prog_array_map_free(struct bpf_map *map)
  * Thus, prog_array_map cannot be used as an inner_map
  * and map_meta_equal is not implemented.
  */
-static int prog_array_map_btf_id;
 const struct bpf_map_ops prog_array_map_ops = {
 	.map_alloc_check = fd_array_map_alloc_check,
 	.map_alloc = prog_array_map_alloc,
@@ -1128,8 +1125,7 @@ const struct bpf_map_ops prog_array_map_ops = {
 	.map_fd_sys_lookup_elem = prog_fd_array_sys_lookup_elem,
 	.map_release_uref = prog_array_map_clear,
 	.map_seq_show_elem = prog_array_map_seq_show_elem,
-	.map_btf_name = "bpf_array",
-	.map_btf_id = &prog_array_map_btf_id,
+	.map_btf_id = &array_map_btf_ids[0],
 };
 
 static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
@@ -1218,7 +1214,6 @@ static void perf_event_fd_array_map_free(struct bpf_map *map)
 	fd_array_map_free(map);
 }
 
-static int perf_event_array_map_btf_id;
 const struct bpf_map_ops perf_event_array_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc_check = fd_array_map_alloc_check,
@@ -1231,8 +1226,7 @@ const struct bpf_map_ops perf_event_array_map_ops = {
 	.map_fd_put_ptr = perf_event_fd_array_put_ptr,
 	.map_release = perf_event_fd_array_release,
 	.map_check_btf = map_check_no_btf,
-	.map_btf_name = "bpf_array",
-	.map_btf_id = &perf_event_array_map_btf_id,
+	.map_btf_id = &array_map_btf_ids[0],
 };
 
 #ifdef CONFIG_CGROUPS
@@ -1255,7 +1249,6 @@ static void cgroup_fd_array_free(struct bpf_map *map)
 	fd_array_map_free(map);
 }
 
-static int cgroup_array_map_btf_id;
 const struct bpf_map_ops cgroup_array_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc_check = fd_array_map_alloc_check,
@@ -1267,8 +1260,7 @@ const struct bpf_map_ops cgroup_array_map_ops = {
 	.map_fd_get_ptr = cgroup_fd_array_get_ptr,
 	.map_fd_put_ptr = cgroup_fd_array_put_ptr,
 	.map_check_btf = map_check_no_btf,
-	.map_btf_name = "bpf_array",
-	.map_btf_id = &cgroup_array_map_btf_id,
+	.map_btf_id = &array_map_btf_ids[0],
 };
 #endif
 
@@ -1342,7 +1334,6 @@ static int array_of_map_gen_lookup(struct bpf_map *map,
 	return insn - insn_buf;
 }
 
-static int array_of_maps_map_btf_id;
 const struct bpf_map_ops array_of_maps_map_ops = {
 	.map_alloc_check = fd_array_map_alloc_check,
 	.map_alloc = array_of_map_alloc,
@@ -1355,6 +1346,5 @@ const struct bpf_map_ops array_of_maps_map_ops = {
 	.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
 	.map_gen_lookup = array_of_map_gen_lookup,
 	.map_check_btf = map_check_no_btf,
-	.map_btf_name = "bpf_array",
-	.map_btf_id = &array_of_maps_map_btf_id,
+	.map_btf_id = &array_map_btf_ids[0],
 };

kernel/bpf/bloom_filter.c

@@ -7,6 +7,7 @@
 #include <linux/err.h>
 #include <linux/jhash.h>
 #include <linux/random.h>
+#include <linux/btf_ids.h>
 
 #define BLOOM_CREATE_FLAG_MASK \
 	(BPF_F_NUMA_NODE | BPF_F_ZERO_SEED | BPF_F_ACCESS_MASK)
@@ -192,7 +193,7 @@ static int bloom_map_check_btf(const struct bpf_map *map,
 	return btf_type_is_void(key_type) ? 0 : -EINVAL;
 }
 
-static int bpf_bloom_map_btf_id;
+BTF_ID_LIST_SINGLE(bpf_bloom_map_btf_ids, struct, bpf_bloom_filter)
 const struct bpf_map_ops bloom_filter_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc = bloom_map_alloc,
@@ -205,6 +206,5 @@ const struct bpf_map_ops bloom_filter_map_ops = {
 	.map_update_elem = bloom_map_update_elem,
 	.map_delete_elem = bloom_map_delete_elem,
 	.map_check_btf = bloom_map_check_btf,
-	.map_btf_name = "bpf_bloom_filter",
-	.map_btf_id = &bpf_bloom_map_btf_id,
+	.map_btf_id = &bpf_bloom_map_btf_ids[0],
 };

kernel/bpf/bpf_inode_storage.c

@@ -245,7 +245,8 @@ static void inode_storage_map_free(struct bpf_map *map)
 	bpf_local_storage_map_free(smap, NULL);
 }
 
-static int inode_storage_map_btf_id;
+BTF_ID_LIST_SINGLE(inode_storage_map_btf_ids, struct,
+		   bpf_local_storage_map)
 const struct bpf_map_ops inode_storage_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc_check = bpf_local_storage_map_alloc_check,
@@ -256,8 +257,7 @@ const struct bpf_map_ops inode_storage_map_ops = {
 	.map_update_elem = bpf_fd_inode_storage_update_elem,
 	.map_delete_elem = bpf_fd_inode_storage_delete_elem,
 	.map_check_btf = bpf_local_storage_map_check_btf,
-	.map_btf_name = "bpf_local_storage_map",
-	.map_btf_id = &inode_storage_map_btf_id,
+	.map_btf_id = &inode_storage_map_btf_ids[0],
 	.map_owner_storage_ptr = inode_storage_ptr,
 };
 

kernel/bpf/bpf_struct_ops.c

@@ -10,6 +10,7 @@
 #include <linux/seq_file.h>
 #include <linux/refcount.h>
 #include <linux/mutex.h>
+#include <linux/btf_ids.h>
 
 enum bpf_struct_ops_state {
 	BPF_STRUCT_OPS_STATE_INIT,
@@ -612,7 +613,7 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
 	return map;
 }
 
-static int bpf_struct_ops_map_btf_id;
+BTF_ID_LIST_SINGLE(bpf_struct_ops_map_btf_ids, struct, bpf_struct_ops_map)
 const struct bpf_map_ops bpf_struct_ops_map_ops = {
 	.map_alloc_check = bpf_struct_ops_map_alloc_check,
 	.map_alloc = bpf_struct_ops_map_alloc,
@@ -622,8 +623,7 @@ const struct bpf_map_ops bpf_struct_ops_map_ops = {
 	.map_delete_elem = bpf_struct_ops_map_delete_elem,
 	.map_update_elem = bpf_struct_ops_map_update_elem,
 	.map_seq_show_elem = bpf_struct_ops_map_seq_show_elem,
-	.map_btf_name = "bpf_struct_ops_map",
-	.map_btf_id = &bpf_struct_ops_map_btf_id,
+	.map_btf_id = &bpf_struct_ops_map_btf_ids[0],
 };
 
 /* "const void *" because some subsystem is

kernel/bpf/bpf_task_storage.c

@@ -307,7 +307,7 @@ static void task_storage_map_free(struct bpf_map *map)
 	bpf_local_storage_map_free(smap, &bpf_task_storage_busy);
 }
 
-static int task_storage_map_btf_id;
+BTF_ID_LIST_SINGLE(task_storage_map_btf_ids, struct, bpf_local_storage_map)
 const struct bpf_map_ops task_storage_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc_check = bpf_local_storage_map_alloc_check,
@@ -318,8 +318,7 @@ const struct bpf_map_ops task_storage_map_ops = {
 	.map_update_elem = bpf_pid_task_storage_update_elem,
 	.map_delete_elem = bpf_pid_task_storage_delete_elem,
 	.map_check_btf = bpf_local_storage_map_check_btf,
-	.map_btf_name = "bpf_local_storage_map",
-	.map_btf_id = &task_storage_map_btf_id,
+	.map_btf_id = &task_storage_map_btf_ids[0],
 	.map_owner_storage_ptr = task_storage_ptr,
 };
 

kernel/bpf/btf.c

@@ -5025,41 +5025,6 @@ btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
 	return ctx_type;
 }
 
-static const struct bpf_map_ops * const btf_vmlinux_map_ops[] = {
-#define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type)
-#define BPF_LINK_TYPE(_id, _name)
-#define BPF_MAP_TYPE(_id, _ops) \
-	[_id] = &_ops,
-#include <linux/bpf_types.h>
-#undef BPF_PROG_TYPE
-#undef BPF_LINK_TYPE
-#undef BPF_MAP_TYPE
-};
-
-static int btf_vmlinux_map_ids_init(const struct btf *btf,
-				    struct bpf_verifier_log *log)
-{
-	const struct bpf_map_ops *ops;
-	int i, btf_id;
-
-	for (i = 0; i < ARRAY_SIZE(btf_vmlinux_map_ops); ++i) {
-		ops = btf_vmlinux_map_ops[i];
-		if (!ops || (!ops->map_btf_name && !ops->map_btf_id))
-			continue;
-		if (!ops->map_btf_name || !ops->map_btf_id) {
-			bpf_log(log, "map type %d is misconfigured\n", i);
-			return -EINVAL;
-		}
-		btf_id = btf_find_by_name_kind(btf, ops->map_btf_name,
-					       BTF_KIND_STRUCT);
-		if (btf_id < 0)
-			return btf_id;
-		*ops->map_btf_id = btf_id;
-	}
-
-	return 0;
-}
-
 static int btf_translate_to_vmlinux(struct bpf_verifier_log *log,
 				     struct btf *btf,
 				     const struct btf_type *t,
@@ -5125,11 +5090,6 @@ struct btf *btf_parse_vmlinux(void)
 	/* btf_parse_vmlinux() runs under bpf_verifier_lock */
 	bpf_ctx_convert.t = btf_type_by_id(btf, bpf_ctx_convert_btf_id[0]);
 
-	/* find bpf map structs for map_ptr access checking */
-	err = btf_vmlinux_map_ids_init(btf, log);
-	if (err < 0)
-		goto errout;
-
 	bpf_struct_ops_init(btf, log);
 
 	refcount_set(&btf->refcnt, 1);

kernel/bpf/cpumap.c

@@ -27,6 +27,7 @@
 #include <linux/kthread.h>
 #include <linux/capability.h>
 #include <trace/events/xdp.h>
+#include <linux/btf_ids.h>
 
 #include <linux/netdevice.h>   /* netif_receive_skb_list */
 #include <linux/etherdevice.h> /* eth_type_trans */
@@ -673,7 +674,7 @@ static int cpu_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
 				      __cpu_map_lookup_elem);
 }
 
-static int cpu_map_btf_id;
+BTF_ID_LIST_SINGLE(cpu_map_btf_ids, struct, bpf_cpu_map)
 const struct bpf_map_ops cpu_map_ops = {
 	.map_meta_equal		= bpf_map_meta_equal,
 	.map_alloc		= cpu_map_alloc,
@@ -683,8 +684,7 @@ const struct bpf_map_ops cpu_map_ops = {
 	.map_lookup_elem	= cpu_map_lookup_elem,
 	.map_get_next_key	= cpu_map_get_next_key,
 	.map_check_btf		= map_check_no_btf,
-	.map_btf_name		= "bpf_cpu_map",
-	.map_btf_id		= &cpu_map_btf_id,
+	.map_btf_id		= &cpu_map_btf_ids[0],
 	.map_redirect		= cpu_map_redirect,
 };
 

kernel/bpf/devmap.c

@@ -48,6 +48,7 @@
 #include <net/xdp.h>
 #include <linux/filter.h>
 #include <trace/events/xdp.h>
+#include <linux/btf_ids.h>
 
 #define DEV_CREATE_FLAG_MASK \
 	(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
@@ -1005,7 +1006,7 @@ static int dev_hash_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
 				      __dev_map_hash_lookup_elem);
 }
 
-static int dev_map_btf_id;
+BTF_ID_LIST_SINGLE(dev_map_btf_ids, struct, bpf_dtab)
 const struct bpf_map_ops dev_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc = dev_map_alloc,
@@ -1015,12 +1016,10 @@ const struct bpf_map_ops dev_map_ops = {
 	.map_update_elem = dev_map_update_elem,
 	.map_delete_elem = dev_map_delete_elem,
 	.map_check_btf = map_check_no_btf,
-	.map_btf_name = "bpf_dtab",
-	.map_btf_id = &dev_map_btf_id,
+	.map_btf_id = &dev_map_btf_ids[0],
 	.map_redirect = dev_map_redirect,
 };
 
-static int dev_map_hash_map_btf_id;
 const struct bpf_map_ops dev_map_hash_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
 	.map_alloc = dev_map_alloc,
@@ -1030,8 +1029,7 @@ const struct bpf_map_ops dev_map_hash_ops = {
 	.map_update_elem = dev_map_hash_update_elem,
 	.map_delete_elem = dev_map_hash_delete_elem,
 	.map_check_btf = map_check_no_btf,
-	.map_btf_name = "bpf_dtab",
-	.map_btf_id = &dev_map_hash_map_btf_id,
+	.map_btf_id = &dev_map_btf_ids[0],
 	.map_redirect = dev_hash_map_redirect,
 };