bpf: Relax max_entries check for most of the inner map types

Most of the maps do not use max_entries during verification time. Thus, those map_meta_equal() do not need to enforce max_entries when it is inserted as an inner map during runtime. The max_entries check is removed from the default implementation bpf_map_meta_equal(). The prog_array_map and xsk_map are exception. Its map_gen_lookup uses max_entries to generate inline lookup code. Thus, they will implement its own map_meta_equal() to enforce max_entries. Since there are only two cases now, the max_entries check is not refactored and stays in its own .c file.

Martin KaFai Lau committed 6 years ago

Commit 134fede1 parent f4d05253 files · +17 −4Browse files

Showing the changes to kernel/bpf/arraymap.c (1 of 3 files). Show all

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kernel/bpf/arraymap.c+8−1

 				   vma->vm_pgoff + pgoff);
 }
+static bool array_map_meta_equal(const struct bpf_map *meta0,
+				 const struct bpf_map *meta1)
+{
+	return meta0->max_entries == meta1->max_entries &&
+		bpf_map_meta_equal(meta0, meta1);
+}
 struct bpf_iter_seq_array_map_info {
 	struct bpf_map *map;
 	void *percpu_value_buf;
 static int array_map_btf_id;
 const struct bpf_map_ops array_map_ops = {
-	.map_meta_equal = bpf_map_meta_equal,
+	.map_meta_equal = array_map_meta_equal,
 	.map_alloc_check = array_map_alloc_check,
 	.map_alloc = array_map_alloc,
 	.map_free = array_map_free,