bpf: Refactor map->off_arr handling

Refactor map->off_arr handling into generic functions that can work on
their own without hardcoding map specific code. The btf_fields_offs
structure is now returned from btf_parse_field_offs, which can be reused
later for types in program BTF.

All functions like copy_map_value, zero_map_value call generic
underlying functions so that they can also be reused later for copying
to values allocated in programs which encode specific fields.

Later, some helper functions will also require access to this
btf_field_offs structure to be able to skip over special fields at
runtime.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221103191013.1236066-9-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 9 insertions, 64 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 53d6dc5cf0e2..85532d301124 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -943,66 +943,6 @@ int map_check_no_btf(const struct bpf_map *map,
 	return -ENOTSUPP;
 }
 
-static int map_field_offs_cmp(const void *_a, const void *_b, const void *priv)
-{
-	const u32 a = *(const u32 *)_a;
-	const u32 b = *(const u32 *)_b;
-
-	if (a < b)
-		return -1;
-	else if (a > b)
-		return 1;
-	return 0;
-}
-
-static void map_field_offs_swap(void *_a, void *_b, int size, const void *priv)
-{
-	struct bpf_map *map = (struct bpf_map *)priv;
-	u32 *off_base = map->field_offs->field_off;
-	u32 *a = _a, *b = _b;
-	u8 *sz_a, *sz_b;
-
-	sz_a = map->field_offs->field_sz + (a - off_base);
-	sz_b = map->field_offs->field_sz + (b - off_base);
-
-	swap(*a, *b);
-	swap(*sz_a, *sz_b);
-}
-
-static int bpf_map_alloc_off_arr(struct bpf_map *map)
-{
-	bool has_fields = !IS_ERR_OR_NULL(map->record);
-	struct btf_field_offs *fo;
-	struct btf_record *rec;
-	u32 i, *off;
-	u8 *sz;
-
-	if (!has_fields) {
-		map->field_offs = NULL;
-		return 0;
-	}
-
-	fo = kzalloc(sizeof(*map->field_offs), GFP_KERNEL | __GFP_NOWARN);
-	if (!fo)
-		return -ENOMEM;
-	map->field_offs = fo;
-
-	rec = map->record;
-	off = fo->field_off;
-	sz = fo->field_sz;
-	for (i = 0; i < rec->cnt; i++) {
-		*off++ = rec->fields[i].offset;
-		*sz++ = btf_field_type_size(rec->fields[i].type);
-	}
-	fo->cnt = rec->cnt;
-
-	if (fo->cnt == 1)
-		return 0;
-	sort_r(fo->field_off, fo->cnt, sizeof(fo->field_off[0]),
-	       map_field_offs_cmp, map_field_offs_swap, map);
-	return 0;
-}
-
 static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 			 u32 btf_key_id, u32 btf_value_id)
 {
@@ -1097,6 +1037,7 @@ free_map_tab:
 static int map_create(union bpf_attr *attr)
 {
 	int numa_node = bpf_map_attr_numa_node(attr);
+	struct btf_field_offs *foffs;
 	struct bpf_map *map;
 	int f_flags;
 	int err;
@@ -1176,13 +1117,17 @@ static int map_create(union bpf_attr *attr)
 			attr->btf_vmlinux_value_type_id;
 	}
 
-	err = bpf_map_alloc_off_arr(map);
-	if (err)
+
+	foffs = btf_parse_field_offs(map->record);
+	if (IS_ERR(foffs)) {
+		err = PTR_ERR(foffs);
 		goto free_map;
+	}
+	map->field_offs = foffs;
 
 	err = security_bpf_map_alloc(map);
 	if (err)
-		goto free_map_off_arr;
+		goto free_map_field_offs;
 
 	err = bpf_map_alloc_id(map);
 	if (err)
@@ -1206,7 +1151,7 @@ static int map_create(union bpf_attr *attr)
 
 free_map_sec:
 	security_bpf_map_free(map);
-free_map_off_arr:
+free_map_field_offs:
 	kfree(map->field_offs);
 free_map:
 	btf_put(map->btf);