| 1 | /* $Id: Docs-CodingGuidelines.cpp 96407 2022-08-22 17:43:14Z vboxsync $ */
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| 2 | /** @file
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| 3 | * VMM - Coding Guidelines.
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2006-2022 Oracle and/or its affiliates.
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| 8 | *
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| 9 | * This file is part of VirtualBox base platform packages, as
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| 10 | * available from https://www.virtualbox.org.
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| 11 | *
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| 12 | * This program is free software; you can redistribute it and/or
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| 13 | * modify it under the terms of the GNU General Public License
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| 14 | * as published by the Free Software Foundation, in version 3 of the
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| 15 | * License.
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| 16 | *
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| 17 | * This program is distributed in the hope that it will be useful, but
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| 18 | * WITHOUT ANY WARRANTY; without even the implied warranty of
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| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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| 20 | * General Public License for more details.
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| 21 | *
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| 22 | * You should have received a copy of the GNU General Public License
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| 23 | * along with this program; if not, see <https://www.gnu.org/licenses>.
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| 24 | *
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| 25 | * SPDX-License-Identifier: GPL-3.0-only
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| 26 | */
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| 27 |
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| 28 |
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| 29 | /** @page pg_vmm_guideline VMM Coding Guidelines
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| 30 | *
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| 31 | * The guidelines extends the VBox coding guidelines (@ref pg_vbox_guideline)
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| 32 | * and consists of a compulsory part and an optional part. It is very important
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| 33 | * that the rules of the compulsory part is followed. That will prevent obvious
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| 34 | * bugs, and it will ease porting the code to 32/64 and 64/32 bits setups.
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| 35 | *
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| 36 | *
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| 37 | *
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| 38 | * @section sec_vmm_guideline_compulsory Compulsory
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| 39 | *
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| 40 | * It is of vital importance is to distinguish between addresses - both virtual
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| 41 | * and physical - applying to Guest Context and Host Context. To assist the
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| 42 | * coder in this, a set of types and macros have been created. Another vital
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| 43 | * thing is that structures shared between the two contexts ends up with the
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| 44 | * same size and member offsets in both places. There are types and macros
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| 45 | * for that too.
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| 46 | *
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| 47 | *
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| 48 | * The rules:
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| 49 | *
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| 50 | * - When declaring pointers in shared structures use the RCPTRTYPE(),
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| 51 | * R0PTRTYPE() and R3PTRTYPE() macros.
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| 52 | *
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| 53 | * - Use RTGCPTR and RTHCPTR when dealing with the other context in
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| 54 | * none shared structures, parameter lists, stack variables and such.
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| 55 | *
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| 56 | * - Following the above rules, pointers will in a context other than the
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| 57 | * one a pointer was defined for, appear as unsigned integers.
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| 58 | *
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| 59 | * - It is NOT permitted to subject a pointer from the other context to pointer
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| 60 | * types of the current context by direct cast or by definition.
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| 61 | *
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| 62 | * - When doing pointer arithmetic cast using uintptr_t, intptr_t or char *.
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| 63 | * Never cast a pointer to anything else for this purpose, that will not
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| 64 | * work everywhere! (1)
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| 65 | *
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| 66 | * - Physical addresses are also specific to their context. Use RTGCPHYS
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| 67 | * and RTHCPHYS when dealing when them. Both types are unsigned integers.
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| 68 | *
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| 69 | * - Integers in shared structures should be using a RT integer type or
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| 70 | * any of the [u]int[0-9]+_t types. (2)
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| 71 | *
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| 72 | * - If code is shared between the contexts, GCTYPE() can be used to declare
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| 73 | * things differently. If GCTYPE() usage is extensive, don't share the code.
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| 74 | *
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| 75 | * - The context is part of all public symbols which are specific to a single
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| 76 | * context.
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| 77 | *
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| 78 | *
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| 79 | * (1) Talking about porting between 32-bit and 64-bit architectures and even
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| 80 | * between 64-bit platforms. On 64-bit linux int is 32-bit, long is 64-bit.
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| 81 | * However on 64-bit windows both int and long are 32-bit - there is no
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| 82 | * standard 64 bit type (_int64 is not a standard type, it's an stupid
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| 83 | * extension).
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| 84 | *
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| 85 | * (2) The VBox integer types are RTINT, RTUINT, RTGCINT, RTGCUINT,
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| 86 | * RTGCINTPTR, RTGCUINTPTR, RTHCINT, RTHCUINT, RTHCINTPTR and
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| 87 | * RTHCUINTPTR.
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| 88 | *
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| 89 | *
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| 90 | *
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| 91 | * @section sec_vmm_guideline_optional Optional
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| 92 | *
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| 93 | * There are the general VBox guidelines, see @ref sec_vbox_guideline_optional.
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| 94 | * In addition to these for the following rules applies to the VMM:
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| 95 | *
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| 96 | * - Prefixes GCPtr and HCPtr are preferred over suffixes HC and GC of
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| 97 | * pointers.
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| 98 | *
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| 99 | * - Prefixes GCPhys and HCPhys are generally used for physical addresses,
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| 100 | * types RTGCPHYS and RTHCPHYS respectively.
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| 101 | *
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| 102 | */
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| 103 |
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