1 /* 2 * Copyright (C) 2020 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #pragma once 18 19 /* This file is separate because it's included both by eBPF programs (via include 20 * in bpf_helpers.h) and directly by the boot time bpfloader (Loader.cpp). 21 */ 22 23 #include <linux/bpf.h> 24 25 // Pull in AID_* constants from //system/core/libcutils/include/private/android_filesystem_config.h 26 #include <private/android_filesystem_config.h> 27 28 /****************************************************************************** 29 * * 30 * ! ! ! W A R N I N G ! ! ! * 31 * * 32 * CHANGES TO THESE STRUCTURE DEFINITIONS OUTSIDE OF AOSP/MASTER *WILL* BREAK * 33 * MAINLINE MODULE COMPATIBILITY * 34 * * 35 * AND THUS MAY RESULT IN YOUR DEVICE BRICKING AT SOME ARBITRARY POINT IN * 36 * THE FUTURE * 37 * * 38 * (and even in aosp/master you may only append new fields at the very end, * 39 * you may *never* delete fields, change their types, ordering, insert in * 40 * the middle, etc. If a mainline module using the old definition has * 41 * already shipped (which happens roughly monthly), then it's set in stone) * 42 * * 43 ******************************************************************************/ 44 45 // These are the values used if these fields are missing 46 #define DEFAULT_BPFLOADER_MIN_VER 0u // v0.0 (this is inclusive ie. >= v0.0) 47 #define DEFAULT_BPFLOADER_MAX_VER 0x10000u // v1.0 (this is exclusive ie. < v1.0) 48 #define DEFAULT_SIZEOF_BPF_MAP_DEF 32 // v0.0 struct: enum (uint sized) + 7 uint 49 #define DEFAULT_SIZEOF_BPF_PROG_DEF 20 // v0.0 struct: 4 uint + bool + 3 byte alignment pad 50 51 /* 52 * The bpf_{map,prog}_def structures are compiled for different architectures. 53 * Once by the BPF compiler for the BPF architecture, and once by a C++ 54 * compiler for the native Android architecture for the bpfloader. 55 * 56 * For things to work, their layout must be the same between the two. 57 * The BPF architecture is platform independent ('64-bit LSB bpf'). 58 * So this effectively means these structures must be the same layout 59 * on 5 architectures, all of them little endian: 60 * 64-bit BPF, x86_64, arm and 32-bit x86 and arm 61 * 62 * As such for any types we use inside of these structs we must make sure that 63 * the size and alignment are the same, so the same amount of padding is used. 64 * 65 * Currently we only use: bool, enum bpf_map_type and unsigned int. 66 * Additionally we use char for padding. 67 * 68 * !!! WARNING: HERE BE DRAGONS !!! 69 * 70 * Be particularly careful with 64-bit integers. 71 * You will need to manually override their alignment to 8 bytes. 72 * 73 * To quote some parts of https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69560 74 * 75 * Some types have weaker alignment requirements when they are structure members. 76 * 77 * unsigned long long on x86 is such a type. 78 * 79 * C distinguishes C11 _Alignof (the minimum alignment the type is guaranteed 80 * to have in all contexts, so 4, see min_align_of_type) from GNU C __alignof 81 * (the normal alignment of the type, so 8). 82 * 83 * alignof / _Alignof == minimum alignment required by target ABI 84 * __alignof / __alignof__ == preferred alignment 85 * 86 * When in a struct, apparently the minimum alignment is used. 87 */ 88 89 _Static_assert(sizeof(bool) == 1, "sizeof bool != 1"); 90 _Static_assert(__alignof__(bool) == 1, "__alignof__ bool != 1"); 91 _Static_assert(_Alignof(bool) == 1, "_Alignof bool != 1"); 92 93 _Static_assert(sizeof(char) == 1, "sizeof char != 1"); 94 _Static_assert(__alignof__(char) == 1, "__alignof__ char != 1"); 95 _Static_assert(_Alignof(char) == 1, "_Alignof char != 1"); 96 97 // This basically verifies that an enum is 'just' a 32-bit int 98 _Static_assert(sizeof(enum bpf_map_type) == 4, "sizeof enum bpf_map_type != 4"); 99 _Static_assert(__alignof__(enum bpf_map_type) == 4, "__alignof__ enum bpf_map_type != 4"); 100 _Static_assert(_Alignof(enum bpf_map_type) == 4, "_Alignof enum bpf_map_type != 4"); 101 102 // Linux kernel requires sizeof(int) == 4, sizeof(void*) == sizeof(long), sizeof(long long) == 8 103 _Static_assert(sizeof(unsigned int) == 4, "sizeof unsigned int != 4"); 104 _Static_assert(__alignof__(unsigned int) == 4, "__alignof__ unsigned int != 4"); 105 _Static_assert(_Alignof(unsigned int) == 4, "_Alignof unsigned int != 4"); 106 107 // We don't currently use any 64-bit types in these structs, so this is purely to document issue. 108 // Here sizeof & __alignof__ are consistent, but _Alignof is not: compile for 'aosp_cf_x86_phone' 109 _Static_assert(sizeof(unsigned long long) == 8, "sizeof unsigned long long != 8"); 110 _Static_assert(__alignof__(unsigned long long) == 8, "__alignof__ unsigned long long != 8"); 111 // BPF wants 8, but 32-bit x86 wants 4 112 //_Static_assert(_Alignof(unsigned long long) == 8, "_Alignof unsigned long long != 8"); 113 114 /* 115 * Map structure to be used by Android eBPF C programs. The Android eBPF loader 116 * uses this structure from eBPF object to create maps at boot time. 117 * 118 * The eBPF C program should define structure in the maps section using 119 * SEC("maps") otherwise it will be ignored by the eBPF loader. 120 * 121 * For example: 122 * const struct bpf_map_def SEC("maps") mymap { .type=... , .key_size=... } 123 * 124 * See 'bpf_helpers.h' for helpful macros for eBPF program use. 125 */ 126 struct bpf_map_def { 127 enum bpf_map_type type; 128 unsigned int key_size; 129 unsigned int value_size; 130 unsigned int max_entries; 131 unsigned int map_flags; 132 133 // The following are not supported by the Android bpfloader: 134 // unsigned int inner_map_idx; 135 // unsigned int numa_node; 136 137 unsigned int uid; // uid_t 138 unsigned int gid; // gid_t 139 unsigned int mode; // mode_t 140 141 // The following fields were added in version 0.1 142 unsigned int bpfloader_min_ver; // if missing, defaults to 0, ie. v0.0 143 unsigned int bpfloader_max_ver; // if missing, defaults to 0x10000, ie. v1.0 144 145 // The following fields were added in version 0.2 146 // kernelVersion() must be >= min_kver and < max_kver 147 unsigned int min_kver; 148 unsigned int max_kver; 149 }; 150 151 // This needs to be updated whenever the above structure definition is expanded. 152 _Static_assert(sizeof(struct bpf_map_def) == 48, "sizeof struct bpf_map_def != 48"); 153 _Static_assert(__alignof__(struct bpf_map_def) == 4, "__alignof__ struct bpf_map_def != 4"); 154 _Static_assert(_Alignof(struct bpf_map_def) == 4, "_Alignof struct bpf_map_def != 4"); 155 156 struct bpf_prog_def { 157 unsigned int uid; 158 unsigned int gid; 159 160 // kernelVersion() must be >= min_kver and < max_kver 161 unsigned int min_kver; 162 unsigned int max_kver; 163 164 bool optional; // program section (ie. function) may fail to load, continue onto next func. 165 char pad0[3]; 166 167 // The following fields were added in version 0.1 168 unsigned int bpfloader_min_ver; // if missing, defaults to 0, ie. v0.0 169 unsigned int bpfloader_max_ver; // if missing, defaults to 0x10000, ie. v1.0 170 171 // No new fields in version 0.2 172 }; 173 174 // This needs to be updated whenever the above structure definition is expanded. 175 _Static_assert(sizeof(struct bpf_prog_def) == 28, "sizeof struct bpf_prog_def != 28"); 176 _Static_assert(__alignof__(struct bpf_prog_def) == 4, "__alignof__ struct bpf_prog_def != 4"); 177 _Static_assert(_Alignof(struct bpf_prog_def) == 4, "_Alignof struct bpf_prog_def != 4"); 178