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 <cutils/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 // Length of strings (incl. selinux_context and pin_subdir) 115 // in the bpf_map_def and bpf_prog_def structs. 116 // 117 // WARNING: YOU CANNOT *EVER* CHANGE THESE 118 // as this would affect the structure size in backwards incompatible ways 119 // and break mainline module loading on older Android T devices 120 #define BPF_SELINUX_CONTEXT_CHAR_ARRAY_SIZE 32 121 #define BPF_PIN_SUBDIR_CHAR_ARRAY_SIZE 32 122 123 /* 124 * Map structure to be used by Android eBPF C programs. The Android eBPF loader 125 * uses this structure from eBPF object to create maps at boot time. 126 * 127 * The eBPF C program should define structure in the maps section using 128 * SECTION("maps") otherwise it will be ignored by the eBPF loader. 129 * 130 * For example: 131 * const struct bpf_map_def SECTION("maps") mymap { .type=... , .key_size=... } 132 * 133 * See 'bpf_helpers.h' for helpful macros for eBPF program use. 134 */ 135 struct bpf_map_def { 136 enum bpf_map_type type; 137 unsigned int key_size; 138 unsigned int value_size; 139 unsigned int max_entries; 140 unsigned int map_flags; 141 142 // The following are not supported by the Android bpfloader: 143 // unsigned int inner_map_idx; 144 // unsigned int numa_node; 145 146 unsigned int uid; // uid_t 147 unsigned int gid; // gid_t 148 unsigned int mode; // mode_t 149 150 // The following fields were added in version 0.1 151 unsigned int bpfloader_min_ver; // if missing, defaults to 0, ie. v0.0 152 unsigned int bpfloader_max_ver; // if missing, defaults to 0x10000, ie. v1.0 153 154 // The following fields were added in version 0.2 (S) 155 // kernelVersion() must be >= min_kver and < max_kver 156 unsigned int min_kver; 157 unsigned int max_kver; 158 159 // The following fields were added in version 0.18 (T) 160 // 161 // These are fixed length strings, padded with null bytes 162 // 163 // Warning: supported values depend on .o location 164 // (additionally a newer Android OS and/or bpfloader may support more values) 165 // 166 // overrides default selinux context (which is based on pin subdir) 167 char selinux_context[BPF_SELINUX_CONTEXT_CHAR_ARRAY_SIZE]; 168 // 169 // overrides default prefix (which is based on .o location) 170 char pin_subdir[BPF_PIN_SUBDIR_CHAR_ARRAY_SIZE]; 171 172 bool shared; // use empty string as 'file' component of pin path - allows cross .o map sharing 173 char pad0[3]; // manually pad up to 4 byte alignment, may be used for extensions in the future 174 }; 175 176 _Static_assert(sizeof(((struct bpf_map_def *)0)->selinux_context) == 32, "must be 32 bytes"); 177 _Static_assert(sizeof(((struct bpf_map_def *)0)->pin_subdir) == 32, "must be 32 bytes"); 178 179 // This needs to be updated whenever the above structure definition is expanded. 180 _Static_assert(sizeof(struct bpf_map_def) == 116, "sizeof struct bpf_map_def != 116"); 181 _Static_assert(__alignof__(struct bpf_map_def) == 4, "__alignof__ struct bpf_map_def != 4"); 182 _Static_assert(_Alignof(struct bpf_map_def) == 4, "_Alignof struct bpf_map_def != 4"); 183 184 struct bpf_prog_def { 185 unsigned int uid; 186 unsigned int gid; 187 188 // kernelVersion() must be >= min_kver and < max_kver 189 unsigned int min_kver; 190 unsigned int max_kver; 191 192 bool optional; // program section (ie. function) may fail to load, continue onto next func. 193 char pad0[3]; 194 195 // The following fields were added in version 0.1 196 unsigned int bpfloader_min_ver; // if missing, defaults to 0, ie. v0.0 197 unsigned int bpfloader_max_ver; // if missing, defaults to 0x10000, ie. v1.0 198 199 // The following fields were added in version 0.18, see description up above in bpf_map_def 200 char selinux_context[BPF_SELINUX_CONTEXT_CHAR_ARRAY_SIZE]; 201 char pin_subdir[BPF_PIN_SUBDIR_CHAR_ARRAY_SIZE]; 202 }; 203 204 _Static_assert(sizeof(((struct bpf_prog_def *)0)->selinux_context) == 32, "must be 32 bytes"); 205 _Static_assert(sizeof(((struct bpf_prog_def *)0)->pin_subdir) == 32, "must be 32 bytes"); 206 207 // This needs to be updated whenever the above structure definition is expanded. 208 _Static_assert(sizeof(struct bpf_prog_def) == 92, "sizeof struct bpf_prog_def != 92"); 209 _Static_assert(__alignof__(struct bpf_prog_def) == 4, "__alignof__ struct bpf_prog_def != 4"); 210 _Static_assert(_Alignof(struct bpf_prog_def) == 4, "_Alignof struct bpf_prog_def != 4"); 211