Merge b0900045 on remote branch

Change-Id: I092dd007a59dbd08e5617a4476bba5ba9d1f09ce

libbpf_android/include/bpf/BpfUtils.h

@@ -177,9 +177,6 @@ int synchronizeKernelRCU();
         if (android::bpf::getBpfSupportLevel() != android::bpf::BpfLevel::NONE) return; \
     } while (0)
 
-constexpr int BPF_CONTINUE = 0;
-constexpr int BPF_DELETED = 1;
-
 bool operator==(const StatsValue& lhs, const StatsValue& rhs);
 bool operator==(const UidTag& lhs, const UidTag& rhs);
 bool operator==(const StatsKey& lhs, const StatsKey& rhs);

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 unsigned long long (*bpf_ktime_get_ns)(void) = (void*) BPF_FUNC_ktime_get_ns;
 static int (*bpf_trace_printk)(const char* fmt, int fmt_size, ...) = (void*) BPF_FUNC_trace_printk;