Reapply "Provide a macro to define a map along with type safe accessors"
This reverts commit 4f3298db9355ff7dc995afbad173482b711c1ecf.
Change-Id: Ibf410a56ec69ccc2c14591edcc8b9ede2a410bb4
diff --git a/progs/include/bpf_helpers.h b/progs/include/bpf_helpers.h
index 01bdc68..c6b417f 100644
--- a/progs/include/bpf_helpers.h
+++ b/progs/include/bpf_helpers.h
@@ -11,11 +11,63 @@
* Helper functions called from eBPF programs written in C. These are
* implemented in the kernel sources.
*/
+
/* generic functions */
-static void* (*bpf_map_lookup_elem)(void* map, void* key) = (void*) BPF_FUNC_map_lookup_elem;
-static int (*bpf_map_update_elem)(void* map, void* key, void* value,
- unsigned long long flags) = (void*) BPF_FUNC_map_update_elem;
-static int (*bpf_map_delete_elem)(void* map, void* key) = (void*) BPF_FUNC_map_delete_elem;
+
+/*
+ * Type-unsafe bpf map functions - avoid if possible.
+ *
+ * Using these it is possible to pass in keys/values of the wrong type/size,
+ * or, for 'unsafe_bpf_map_lookup_elem' receive into a pointer to the wrong type.
+ * You will not get a compile time failure, and for certain types of errors you
+ * might not even get a failure from the kernel's ebpf verifier during program load,
+ * instead stuff might just not work right at runtime.
+ *
+ * Instead please use:
+ * DEFINE_BPF_MAP(foo_map, TYPE, KeyType, ValueType, num_entries)
+ * where TYPE can be something like HASH or ARRAY, and num_entries is an integer.
+ *
+ * This defines the map (hence this should not be used in a header file included
+ * from multiple locations) and provides type safe accessors:
+ * ValueType * bpf_foo_map_lookup_elem(KeyType *)
+ * int bpf_foo_map_update_elem(KeyType *, ValueType *, flags)
+ * int bpf_foo_map_delete_elem(KeyType *)
+ *
+ * This will make sure that if you change the type of a map you'll get compile
+ * errors at any spots you forget to update with the new type.
+ */
+static void* (*unsafe_bpf_map_lookup_elem)(void* map, void* key) = (void*)BPF_FUNC_map_lookup_elem;
+static int (*unsafe_bpf_map_update_elem)(void* map, void* key, void* value,
+ unsigned long long flags) = (void*)
+ BPF_FUNC_map_update_elem;
+static int (*unsafe_bpf_map_delete_elem)(void* map, void* key) = (void*)BPF_FUNC_map_delete_elem;
+
+/* type safe macro to declare a map and related accessor functions */
+#define DEFINE_BPF_MAP_NO_ACCESSORS(the_map, TYPE, TypeOfKey, TypeOfValue, num_entries) \
+ struct bpf_map_def SEC("maps") the_map = { \
+ .type = BPF_MAP_TYPE_##TYPE, \
+ .key_size = sizeof(TypeOfKey), \
+ .value_size = sizeof(TypeOfValue), \
+ .max_entries = (num_entries), \
+ };
+
+#define DEFINE_BPF_MAP(the_map, TYPE, TypeOfKey, TypeOfValue, num_entries) \
+ DEFINE_BPF_MAP_NO_ACCESSORS(the_map, TYPE, TypeOfKey, TypeOfValue, num_entries) \
+ \
+ static inline __always_inline __unused TypeOfValue* bpf_##the_map##_lookup_elem( \
+ TypeOfKey* k) { \
+ return unsafe_bpf_map_lookup_elem(&the_map, k); \
+ }; \
+ \
+ static inline __always_inline __unused int bpf_##the_map##_update_elem( \
+ TypeOfKey* k, TypeOfValue* v, unsigned long long flags) { \
+ return unsafe_bpf_map_update_elem(&the_map, k, v, flags); \
+ }; \
+ \
+ static inline __always_inline __unused int bpf_##the_map##_delete_elem(TypeOfKey* k) { \
+ return unsafe_bpf_map_delete_elem(&the_map, k); \
+ };
+
static int (*bpf_probe_read)(void* dst, int size, void* unsafe_ptr) = (void*) BPF_FUNC_probe_read;
static int (*bpf_probe_read_str)(void* dst, int size, void* unsafe_ptr) = (void*) BPF_FUNC_probe_read_str;
static unsigned long long (*bpf_ktime_get_ns)(void) = (void*) BPF_FUNC_ktime_get_ns;
