7c781b0b3c
This is a *partial* NOOP revert of: 'bpf: support BPF_F_NO_PREALLOC in bpf_map_def.h' https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3457780 The comment is simply wrong, the negativeness is hidden by the map declaration macros and thus never makes it into the max_entries field of bpf_map_def struct. A negative value passed to the map creation macros will store the absolute value in max_entries, and set the BPF_F_NO_PREALLOC flag in map_flags. A negative / excessively large max_entries field will (presumably) fail during map creation due to lack of ram. Bug: 399549732 Test: TreeHugger Signed-off-by: Maciej Żenczykowski <maze@google.com> Change-Id: I86951605cb1397c512c484c84e9d67a85b992b07
269 lines
12 KiB
C
269 lines
12 KiB
C
/*
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* Copyright (C) 2020 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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/* This file is separate because it's included both by eBPF programs (via include
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* in bpf_helpers.h) and directly by the boot time bpfloader (Loader.cpp).
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*/
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#include <linux/bpf.h>
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// Pull in AID_* constants from //system/core/libcutils/include/private/android_filesystem_config.h
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#include <cutils/android_filesystem_config.h>
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/******************************************************************************
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* *
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* ! ! ! W A R N I N G ! ! ! *
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* *
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* CHANGES TO THESE STRUCTURE DEFINITIONS OUTSIDE OF AOSP/MAIN *WILL* BREAK *
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* MAINLINE MODULE COMPATIBILITY *
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* *
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* AND THUS MAY RESULT IN YOUR DEVICE BRICKING AT SOME ARBITRARY POINT IN *
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* THE FUTURE *
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* *
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* (and even in aosp/master you may only append new fields at the very end, *
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* you may *never* delete fields, change their types, ordering, insert in *
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* the middle, etc. If a mainline module using the old definition has *
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* already shipped (which happens roughly monthly), then it's set in stone) *
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* *
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******************************************************************************/
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/*
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* The bpf_{map,prog}_def structures are compiled for different architectures.
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* Once by the BPF compiler for the BPF architecture, and once by a C++
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* compiler for the native Android architecture for the bpfloader.
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*
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* For things to work, their layout must be the same between the two.
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* The BPF architecture is platform independent ('64-bit LSB bpf').
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* So this effectively means these structures must be the same layout
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* on 5 architectures, all of them little endian:
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* 64-bit BPF, x86_64, arm and 32-bit x86 and arm
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*
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* As such for any types we use inside of these structs we must make sure that
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* the size and alignment are the same, so the same amount of padding is used.
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*
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* Currently we only use: bool, enum bpf_map_type and unsigned int.
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* Additionally we use char for padding.
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*
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* !!! WARNING: HERE BE DRAGONS !!!
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*
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* Be particularly careful with 64-bit integers.
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* You will need to manually override their alignment to 8 bytes.
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*
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* To quote some parts of https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69560
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*
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* Some types have weaker alignment requirements when they are structure members.
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*
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* unsigned long long on x86 is such a type.
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*
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* C distinguishes C11 _Alignof (the minimum alignment the type is guaranteed
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* to have in all contexts, so 4, see min_align_of_type) from GNU C __alignof
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* (the normal alignment of the type, so 8).
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*
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* alignof / _Alignof == minimum alignment required by target ABI
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* __alignof / __alignof__ == preferred alignment
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*
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* When in a struct, apparently the minimum alignment is used.
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*/
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_Static_assert(sizeof(bool) == 1, "sizeof bool != 1");
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_Static_assert(__alignof__(bool) == 1, "__alignof__ bool != 1");
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_Static_assert(_Alignof(bool) == 1, "_Alignof bool != 1");
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_Static_assert(sizeof(char) == 1, "sizeof char != 1");
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_Static_assert(__alignof__(char) == 1, "__alignof__ char != 1");
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_Static_assert(_Alignof(char) == 1, "_Alignof char != 1");
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// This basically verifies that an enum is 'just' a 32-bit int
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_Static_assert(sizeof(enum bpf_map_type) == 4, "sizeof enum bpf_map_type != 4");
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_Static_assert(__alignof__(enum bpf_map_type) == 4, "__alignof__ enum bpf_map_type != 4");
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_Static_assert(_Alignof(enum bpf_map_type) == 4, "_Alignof enum bpf_map_type != 4");
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// Linux kernel requires sizeof(int) == 4, sizeof(void*) == sizeof(long), sizeof(long long) == 8
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_Static_assert(sizeof(int) == 4, "sizeof int != 4");
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_Static_assert(__alignof__(int) == 4, "__alignof__ int != 4");
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_Static_assert(_Alignof(int) == 4, "_Alignof int != 4");
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_Static_assert(sizeof(unsigned int) == 4, "sizeof unsigned int != 4");
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_Static_assert(__alignof__(unsigned int) == 4, "__alignof__ unsigned int != 4");
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_Static_assert(_Alignof(unsigned int) == 4, "_Alignof unsigned int != 4");
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// We don't currently use any 64-bit types in these structs, so this is purely to document issue.
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// Here sizeof & __alignof__ are consistent, but _Alignof is not: compile for 'aosp_cf_x86_phone'
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_Static_assert(sizeof(unsigned long long) == 8, "sizeof unsigned long long != 8");
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_Static_assert(__alignof__(unsigned long long) == 8, "__alignof__ unsigned long long != 8");
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// BPF & everyone else wants 8, but 32-bit x86 wants 4
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#if defined(__i386__)
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_Static_assert(_Alignof(unsigned long long) == 4, "x86-32 _Alignof unsigned long long != 4");
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#else
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_Static_assert(_Alignof(unsigned long long) == 8, "_Alignof unsigned long long != 8");
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#endif
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// for maps:
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struct shared_bool { bool shared; };
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#define PRIVATE ((struct shared_bool){ .shared = false })
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#define SHARED ((struct shared_bool){ .shared = true })
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// for programs:
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struct optional_bool { bool optional; };
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#define MANDATORY ((struct optional_bool){ .optional = false })
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#define OPTIONAL ((struct optional_bool){ .optional = true })
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// for both maps and programs:
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struct ignore_on_eng_bool { bool ignore_on_eng; };
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#define LOAD_ON_ENG ((struct ignore_on_eng_bool){ .ignore_on_eng = false })
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#define IGNORE_ON_ENG ((struct ignore_on_eng_bool){ .ignore_on_eng = true })
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struct ignore_on_user_bool { bool ignore_on_user; };
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#define LOAD_ON_USER ((struct ignore_on_user_bool){ .ignore_on_user = false })
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#define IGNORE_ON_USER ((struct ignore_on_user_bool){ .ignore_on_user = true })
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struct ignore_on_userdebug_bool { bool ignore_on_userdebug; };
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#define LOAD_ON_USERDEBUG ((struct ignore_on_userdebug_bool){ .ignore_on_userdebug = false })
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#define IGNORE_ON_USERDEBUG ((struct ignore_on_userdebug_bool){ .ignore_on_userdebug = true })
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// Length of strings (incl. selinux_context and pin_subdir)
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// in the bpf_map_def and bpf_prog_def structs.
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//
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// WARNING: YOU CANNOT *EVER* CHANGE THESE
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// as this would affect the structure size in backwards incompatible ways
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// and break mainline module loading on older Android T devices
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#define BPF_SELINUX_CONTEXT_CHAR_ARRAY_SIZE 32
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#define BPF_PIN_SUBDIR_CHAR_ARRAY_SIZE 32
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/*
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* Map structure to be used by Android eBPF C programs. The Android eBPF loader
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* uses this structure from eBPF object to create maps at boot time.
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*
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* The eBPF C program should define structure in the maps section using
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* SECTION("maps") otherwise it will be ignored by the eBPF loader.
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*
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* For example:
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* const struct bpf_map_def SECTION("maps") mymap { .type=... , .key_size=... }
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*
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* See 'bpf_helpers.h' for helpful macros for eBPF program use.
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*/
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struct bpf_map_def {
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enum bpf_map_type type;
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unsigned int key_size;
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unsigned int value_size;
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unsigned int max_entries;
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unsigned int map_flags;
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// The following are not supported by the Android bpfloader:
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// unsigned int inner_map_idx;
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// unsigned int numa_node;
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unsigned int zero; // uid_t, for compat with old (buggy) bpfloader must be AID_ROOT == 0
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unsigned int gid; // gid_t
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unsigned int mode; // mode_t
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// The following fields were added in version 0.1
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unsigned int bpfloader_min_ver; // if missing, defaults to 0, ie. v0.0
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unsigned int bpfloader_max_ver; // if missing, defaults to 0x10000, ie. v1.0
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// The following fields were added in version 0.2 (S)
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// kernelVersion() must be >= min_kver and < max_kver
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unsigned int min_kver;
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unsigned int max_kver;
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// The following fields were added in version 0.18 (T)
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//
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// These are fixed length strings, padded with null bytes
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//
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// Warning: supported values depend on .o location
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// (additionally a newer Android OS and/or bpfloader may support more values)
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//
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// overrides default selinux context (which is based on pin subdir)
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char selinux_context[BPF_SELINUX_CONTEXT_CHAR_ARRAY_SIZE];
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//
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// overrides default prefix (which is based on .o location)
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char pin_subdir[BPF_PIN_SUBDIR_CHAR_ARRAY_SIZE];
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bool shared; // use empty string as 'file' component of pin path - allows cross .o map sharing
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// The following 3 ignore_on_* fields were added in version 0.32 (U). These are ignored in
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// older bpfloader versions, and zero in programs compiled before 0.32.
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bool ignore_on_eng:1;
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bool ignore_on_user:1;
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bool ignore_on_userdebug:1;
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// The following 5 ignore_on_* fields were added in version 0.38 (U). These are ignored in
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// older bpfloader versions, and zero in programs compiled before 0.38.
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// These are tests on the kernel architecture, ie. they ignore userspace bit-ness.
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bool ignore_on_arm32:1;
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bool ignore_on_aarch64:1;
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bool ignore_on_x86_32:1;
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bool ignore_on_x86_64:1;
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bool ignore_on_riscv64:1;
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char pad0[2]; // manually pad up to 4 byte alignment, may be used for extensions in the future
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unsigned int uid; // uid_t
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};
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_Static_assert(sizeof(((struct bpf_map_def *)0)->selinux_context) == 32, "must be 32 bytes");
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_Static_assert(sizeof(((struct bpf_map_def *)0)->pin_subdir) == 32, "must be 32 bytes");
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// This needs to be updated whenever the above structure definition is expanded.
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_Static_assert(sizeof(struct bpf_map_def) == 120, "sizeof struct bpf_map_def != 120");
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_Static_assert(__alignof__(struct bpf_map_def) == 4, "__alignof__ struct bpf_map_def != 4");
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_Static_assert(_Alignof(struct bpf_map_def) == 4, "_Alignof struct bpf_map_def != 4");
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struct bpf_prog_def {
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unsigned int uid;
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unsigned int gid;
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// kernelVersion() must be >= min_kver and < max_kver
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unsigned int min_kver;
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unsigned int max_kver;
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bool optional; // program section (ie. function) may fail to load, continue onto next func.
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// The following 3 ignore_on_* fields were added in version 0.33 (U). These are ignored in
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// older bpfloader versions, and zero in programs compiled before 0.33.
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bool ignore_on_eng:1;
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bool ignore_on_user:1;
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bool ignore_on_userdebug:1;
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// The following 5 ignore_on_* fields were added in version 0.38 (U). These are ignored in
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// older bpfloader versions, and zero in programs compiled before 0.38.
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// These are tests on the kernel architecture, ie. they ignore userspace bit-ness.
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bool ignore_on_arm32:1;
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bool ignore_on_aarch64:1;
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bool ignore_on_x86_32:1;
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bool ignore_on_x86_64:1;
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bool ignore_on_riscv64:1;
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char pad0[2]; // manually pad up to 4 byte alignment, may be used for extensions in the future
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// The following fields were added in version 0.1
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unsigned int bpfloader_min_ver; // if missing, defaults to 0, ie. v0.0
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unsigned int bpfloader_max_ver; // if missing, defaults to 0x10000, ie. v1.0
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// The following fields were added in version 0.18, see description up above in bpf_map_def
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char selinux_context[BPF_SELINUX_CONTEXT_CHAR_ARRAY_SIZE];
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char pin_subdir[BPF_PIN_SUBDIR_CHAR_ARRAY_SIZE];
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};
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_Static_assert(sizeof(((struct bpf_prog_def *)0)->selinux_context) == 32, "must be 32 bytes");
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_Static_assert(sizeof(((struct bpf_prog_def *)0)->pin_subdir) == 32, "must be 32 bytes");
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// This needs to be updated whenever the above structure definition is expanded.
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_Static_assert(sizeof(struct bpf_prog_def) == 92, "sizeof struct bpf_prog_def != 92");
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_Static_assert(__alignof__(struct bpf_prog_def) == 4, "__alignof__ struct bpf_prog_def != 4");
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_Static_assert(_Alignof(struct bpf_prog_def) == 4, "_Alignof struct bpf_prog_def != 4");
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