/* * 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 /****************************************************************************** * * * ! ! ! W A R N I N G ! ! ! * * * * CHANGES TO THESE STRUCTURE DEFINITIONS OUTSIDE OF AOSP/MASTER *WILL* BREAK * * MAINLINE MODULE COMPATIBILITY * * * * AND THUS MAY RESULT IN YOUR DEVICE BRICKING AT SOME ARBITRARY POINT IN * * THE FUTURE * * * * (and even in aosp/master you may only append new fields at the very end, * * you may *never* delete fields, change their types, ordering, insert in * * the middle, etc. If a mainline module using the old definition has * * already shipped (which happens roughly monthly), then it's set in stone) * * * ******************************************************************************/ // These are the values used if these fields are missing #define DEFAULT_BPFLOADER_MIN_VER 0u // v0.0 (this is inclusive ie. >= v0.0) #define DEFAULT_BPFLOADER_MAX_VER 0x10000u // v1.0 (this is exclusive ie. < v1.0) #define DEFAULT_SIZEOF_BPF_MAP_DEF 32 // v0.0 struct: enum (uint sized) + 7 uint #define DEFAULT_SIZEOF_BPF_PROG_DEF 20 // v0.0 struct: 4 uint + bool + 3 byte alignment pad /* * 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 5 architectures, all of them little endian: * 64-bit BPF, x86_64, arm 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(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 wants 8, but 32-bit x86 wants 4 //_Static_assert(_Alignof(unsigned long long) == 8, "_Alignof unsigned long long != 8"); /* * 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 * SEC("maps") otherwise it will be ignored by the eBPF loader. * * For example: * const struct bpf_map_def SEC("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 // The following fields were added in version 0.1 unsigned int bpfloader_min_ver; // if missing, defaults to 0, ie. v0.0 unsigned int bpfloader_max_ver; // if missing, defaults to 0x10000, ie. v1.0 // The following fields were added in version 0.2 // kernelVersion() must be >= min_kver and < max_kver unsigned int min_kver; unsigned int max_kver; }; // This needs to be updated whenever the above structure definition is expanded. _Static_assert(sizeof(struct bpf_map_def) == 48, "sizeof struct bpf_map_def != 48"); _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 { unsigned int uid; unsigned int gid; // kernelVersion() 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]; // The following fields were added in version 0.1 unsigned int bpfloader_min_ver; // if missing, defaults to 0, ie. v0.0 unsigned int bpfloader_max_ver; // if missing, defaults to 0x10000, ie. v1.0 // No new fields in version 0.2 }; // This needs to be updated whenever the above structure definition is expanded. _Static_assert(sizeof(struct bpf_prog_def) == 28, "sizeof struct bpf_prog_def != 28"); _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");