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, 24 insertions, 17 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index aae85019abde..798aec816970 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -341,57 +341,64 @@ static inline void bpf_long_memcpy(void *dst, const void *src, u32 size)
 }
 
 /* copy everything but bpf_spin_lock, bpf_timer, and kptrs. There could be one of each. */
-static inline void __copy_map_value(struct bpf_map *map, void *dst, void *src, bool long_memcpy)
+static inline void bpf_obj_memcpy(struct btf_field_offs *foffs,
+				  void *dst, void *src, u32 size,
+				  bool long_memcpy)
 {
 	u32 curr_off = 0;
 	int i;
 
-	if (likely(!map->field_offs)) {
+	if (likely(!foffs)) {
 		if (long_memcpy)
-			bpf_long_memcpy(dst, src, round_up(map->value_size, 8));
+			bpf_long_memcpy(dst, src, round_up(size, 8));
 		else
-			memcpy(dst, src, map->value_size);
+			memcpy(dst, src, size);
 		return;
 	}
 
-	for (i = 0; i < map->field_offs->cnt; i++) {
-		u32 next_off = map->field_offs->field_off[i];
+	for (i = 0; i < foffs->cnt; i++) {
+		u32 next_off = foffs->field_off[i];
 		u32 sz = next_off - curr_off;
 
 		memcpy(dst + curr_off, src + curr_off, sz);
-		curr_off += map->field_offs->field_sz[i];
+		curr_off += foffs->field_sz[i];
 	}
-	memcpy(dst + curr_off, src + curr_off, map->value_size - curr_off);
+	memcpy(dst + curr_off, src + curr_off, size - curr_off);
 }
 
 static inline void copy_map_value(struct bpf_map *map, void *dst, void *src)
 {
-	__copy_map_value(map, dst, src, false);
+	bpf_obj_memcpy(map->field_offs, dst, src, map->value_size, false);
 }
 
 static inline void copy_map_value_long(struct bpf_map *map, void *dst, void *src)
 {
-	__copy_map_value(map, dst, src, true);
+	bpf_obj_memcpy(map->field_offs, dst, src, map->value_size, true);
 }
 
-static inline void zero_map_value(struct bpf_map *map, void *dst)
+static inline void bpf_obj_memzero(struct btf_field_offs *foffs, void *dst, u32 size)
 {
 	u32 curr_off = 0;
 	int i;
 
-	if (likely(!map->field_offs)) {
-		memset(dst, 0, map->value_size);
+	if (likely(!foffs)) {
+		memset(dst, 0, size);
 		return;
 	}
 
-	for (i = 0; i < map->field_offs->cnt; i++) {
-		u32 next_off = map->field_offs->field_off[i];
+	for (i = 0; i < foffs->cnt; i++) {
+		u32 next_off = foffs->field_off[i];
 		u32 sz = next_off - curr_off;
 
 		memset(dst + curr_off, 0, sz);
-		curr_off += map->field_offs->field_sz[i];
+		curr_off += foffs->field_sz[i];
 	}
-	memset(dst + curr_off, 0, map->value_size - curr_off);
+	memset(dst + curr_off, 0, size - curr_off);
+}
+
+static inline void zero_map_value(struct bpf_map *map, void *dst)
+{
+	bpf_obj_memzero(map->field_offs, dst, map->value_size);
 }
 
 void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,