/* * Copyright (C) 2020 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #pragma once /* This file is separate because it's included both by eBPF programs (via include * in bpf_helpers.h) and directly by the boot time bpfloader (Loader.cpp). */ #include // Pull in AID_* constants from //system/core/libcutils/include/private/android_filesystem_config.h #include #ifdef __cplusplus #include #endif /* * The bpf_{map,prog}_def structures are compiled for different architectures. * Once by the BPF compiler for the BPF architecture, and once by a C++ * compiler for the native Android architecture for the bpfloader. * * For things to work, their layout must be the same between the two. * The BPF architecture is platform independent ('64-bit LSB bpf'). * So this effectively means these structures must be the same layout * on 6 architectures, all of them little endian: * 64-bit BPF, x86_64, arm, riscv and 32-bit x86 and arm * * As such for any types we use inside of these structs we must make sure that * the size and alignment are the same, so the same amount of padding is used. * * Currently we only use: bool, enum bpf_map_type and unsigned int. * Additionally we use char for padding. * * !!! WARNING: HERE BE DRAGONS !!! * * Be particularly careful with 64-bit integers. * You will need to manually override their alignment to 8 bytes. * * To quote some parts of https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69560 * * Some types have weaker alignment requirements when they are structure members. * * unsigned long long on x86 is such a type. * * C distinguishes C11 _Alignof (the minimum alignment the type is guaranteed * to have in all contexts, so 4, see min_align_of_type) from GNU C __alignof * (the normal alignment of the type, so 8). * * alignof / _Alignof == minimum alignment required by target ABI * __alignof / __alignof__ == preferred alignment * * When in a struct, apparently the minimum alignment is used. */ _Static_assert(sizeof(bool) == 1, "sizeof bool != 1"); _Static_assert(__alignof__(bool) == 1, "__alignof__ bool != 1"); _Static_assert(_Alignof(bool) == 1, "_Alignof bool != 1"); _Static_assert(sizeof(char) == 1, "sizeof char != 1"); _Static_assert(__alignof__(char) == 1, "__alignof__ char != 1"); _Static_assert(_Alignof(char) == 1, "_Alignof char != 1"); // This basically verifies that an enum is 'just' a 32-bit int _Static_assert(sizeof(enum bpf_map_type) == 4, "sizeof enum bpf_map_type != 4"); _Static_assert(__alignof__(enum bpf_map_type) == 4, "__alignof__ enum bpf_map_type != 4"); _Static_assert(_Alignof(enum bpf_map_type) == 4, "_Alignof enum bpf_map_type != 4"); // Linux kernel requires sizeof(int) == 4, sizeof(void*) == sizeof(long), sizeof(long long) == 8 _Static_assert(sizeof(int) == 4, "sizeof int != 4"); _Static_assert(__alignof__(int) == 4, "__alignof__ int != 4"); _Static_assert(_Alignof(int) == 4, "_Alignof int != 4"); _Static_assert(sizeof(unsigned int) == 4, "sizeof unsigned int != 4"); _Static_assert(__alignof__(unsigned int) == 4, "__alignof__ unsigned int != 4"); _Static_assert(_Alignof(unsigned int) == 4, "_Alignof unsigned int != 4"); // We don't currently use any 64-bit types in these structs, so this is purely to document issue. // Here sizeof & __alignof__ are consistent, but _Alignof is not: compile for 'aosp_cf_x86_phone' _Static_assert(sizeof(unsigned long long) == 8, "sizeof unsigned long long != 8"); _Static_assert(__alignof__(unsigned long long) == 8, "__alignof__ unsigned long long != 8"); // BPF & everyone else wants 8, but 32-bit x86 wants 4 #if defined(__i386__) _Static_assert(_Alignof(unsigned long long) == 4, "x86-32 _Alignof unsigned long long != 4"); #else _Static_assert(_Alignof(unsigned long long) == 8, "_Alignof unsigned long long != 8"); #endif // for programs: struct optional_bool { bool optional; }; #define MANDATORY ((struct optional_bool){ .optional = false }) #define OPTIONAL ((struct optional_bool){ .optional = true }) // Length of strings (incl. selinux_context and pin_subdir) // in the bpf_map_def and bpf_prog_def structs. #define BPF_DEF_CHAR_ARRAY_SIZE 70 // must be even for alignment sanity /* * Map structure to be used by Android eBPF C programs. The Android eBPF loader * uses this structure from eBPF object to create maps at boot time. * * The eBPF C program should define structure in the maps section using * SECTION(".android_maps") otherwise it will be ignored by the eBPF loader. * * For example: * const struct bpf_map_def SECTION(".android_maps") mymap { .type=... , .key_size=... } * * See 'bpf_helpers.h' for helpful macros for eBPF program use. */ struct bpf_map_def { enum bpf_map_type type; unsigned int key_size; unsigned int value_size; unsigned int max_entries; unsigned int map_flags; // The following are not supported by the Android bpfloader: // unsigned int inner_map_idx; // unsigned int numa_node; unsigned int uid; // uid_t unsigned int gid; // gid_t unsigned int mode; // mode_t int bpfloader_min_ver; int bpfloader_max_ver; // kernelVer must be >= min_kver and < max_kver unsigned int min_kver; unsigned int max_kver; // These are fixed length ASCIIZ strings, padded with null bytes char create_location[BPF_DEF_CHAR_ARRAY_SIZE]; char pin_location[BPF_DEF_CHAR_ARRAY_SIZE]; unsigned int name_idx; #ifdef __cplusplus const char * name() const { return this->pin_location + this->name_idx; } #endif }; #ifdef __cplusplus static_assert(std::is_pod_v); static_assert(std::is_standard_layout_v); #endif // This needs to be updated whenever the above structure definition is expanded. // These asserts are here to make sure we have cross-6-arch consistency. _Static_assert(sizeof(struct bpf_map_def) == 52 + 2 * BPF_DEF_CHAR_ARRAY_SIZE, "wrong sizeof struct bpf_map_def"); _Static_assert(__alignof__(struct bpf_map_def) == 4, "__alignof__ struct bpf_map_def != 4"); _Static_assert(_Alignof(struct bpf_map_def) == 4, "_Alignof struct bpf_map_def != 4"); struct bpf_prog_def { enum bpf_prog_type type; enum bpf_attach_type attach_type; unsigned int uid; unsigned int gid; // kernelVer must be >= min_kver and < max_kver unsigned int min_kver; unsigned int max_kver; bool optional; // program section (ie. function) may fail to load, continue onto next func. char pad0[3]; // manually pad up to 4 byte alignment, may be used for extensions in the future int bpfloader_min_ver; int bpfloader_max_ver; char create_location[BPF_DEF_CHAR_ARRAY_SIZE]; char pin_location[BPF_DEF_CHAR_ARRAY_SIZE]; unsigned int name_idx; #ifdef __cplusplus const char * name() const { return this->pin_location + this->name_idx; } #endif }; #ifdef __cplusplus static_assert(std::is_pod_v); static_assert(std::is_standard_layout_v); #endif // This needs to be updated whenever the above structure definition is expanded. // These asserts are here to make sure we have cross-6-arch consistency. _Static_assert(sizeof(struct bpf_prog_def) == 40 + 2 * BPF_DEF_CHAR_ARRAY_SIZE, "wrong sizeof struct bpf_prog_def"); _Static_assert(__alignof__(struct bpf_prog_def) == 4, "__alignof__ struct bpf_prog_def != 4"); _Static_assert(_Alignof(struct bpf_prog_def) == 4, "_Alignof struct bpf_prog_def != 4"); // Android Mainline BpfLoader version when running on: #define BPFLOADER_MAINLINE_S_VERSION 3100 // Android S (31) #define BPFLOADER_MAINLINE_T_VERSION 3300 // Android T (33) #define BPFLOADER_MAINLINE_U_VERSION 3400 // Android U (34) #define BPFLOADER_MAINLINE_V_VERSION 3500 // Android V (35) #define BPFLOADER_MAINLINE_25Q2_VERSION 3600 // Android 25Q2 (36.0) #define BPFLOADER_MAINLINE_25Q4_VERSION 3610 // Android 25Q4 (36.1) #define BPFLOADER_MAINLINE_26Q1_VERSION 3612 // Android 26Q1 (36.1+) #define BPFLOADER_MAINLINE_26Q2_VERSION 3700 // Android 26Q2 (37.0)