LICENSES/Linux-syscall-note.txt


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NOTE! This copyright does *not* cover user programs that use kernel services by normal system calls - this is merely considered normal use of the kernel, and does *not* fall under the heading of "derived work". Also note that the GPL below is copyrighted by the Free Software Foundation, but the instance of code that it refers to (the Linux kernel) is copyrighted by me and others who actually wrote it.

Also note that the only valid version of the GPL as far as the kernel is concerned is _this_ particular version of the license (ie v2, not v2.2 or v3.x or whatever), unless explicitly otherwise stated.

Linus Torvalds
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * ipa_controls.cpp - IPA control handling
 */

#include <ipa/ipa_controls.h>

/**
 * \file ipa_controls.h
 * \brief Type definitions for serialized controls
 *
 * This file defines binary formats to store ControlList and ControlInfoMap
 * instances in contiguous, self-contained memory areas called control packets.
 * It describes the layout of the packets through a set of C structures. These
 * formats shall be used when serializing ControlList and ControlInfoMap to
 * transfer them through the IPA C interface and IPA IPC transports.
 *
 * A control packet contains a list of entries, each of them describing a single
 * control range or control value. The packet starts with a fixed-size header
 * described by the ipa_controls_header structure, followed by an array of
 * fixed-size entries. Each entry is associated with data, stored either
 * directly in the entry, or in a data section after the entries array.
 *
 * The following diagram describes the layout of the ControlList packet.
 *
 * ~~~~
 *           +-------------------------+    .                      .
 *  Header / | ipa_controls_header     |    |                      |
 *         | |                         |    |                      |
 *         \ |                         |    |                      |
 *           +-------------------------+    |                      |
 *         / | ipa_control_value_entry |    | hdr.data_offset      |
 *         | | #0                      |    |                      |
 * Control | +-------------------------+    |                      |
 *   value | | ...                     |    |                      |
 * entries | +-------------------------+    |                      |
 *         | | ipa_control_value_entry |    |             hdr.size |
 *         \ | #hdr.entries - 1        |    |                      |
 *           +-------------------------+    |                      |
 *           | empty space (optional)  |    |                      |
 *           +-------------------------+ <--´  .                   |
 *         / | ...                     |       | entry[n].offset   |
 *    Data | | ...                     |       |                   |
 * section | | value data for entry #n | <-----´                   |
 *         \ | ...                     |                           |
 *           +-------------------------+                           |
 *           | empty space (optional)  |                           |
 *           +-------------------------+ <-------------------------´
 * ~~~~
 *
 * The packet header contains the size of the packet, the number of entries, and
 * the offset from the beginning of the packet to the data section. The packet
 * entries array immediately follows the header. The data section starts at the
 * offset ipa_controls_header::data_offset from the beginning of the packet, and
 * shall be aligned to a multiple of 8 bytes.
 *
 * Entries are described by the ipa_control_value_entry structure. They contain
 * the numerical ID of the control, its type, and the number of control values.
 *
 * The control values are stored in the data section in the platform's native
 * format. The ipa_control_value_entry::offset field stores the offset from the
 * beginning of the data section to the values.
 *
 * All control values in the data section shall be stored in the same order as
 * the respective control entries, shall be aligned to a multiple of 8 bytes,
 * and shall be contiguous in memory.
 *
 * Empty spaces may be present between the end of the entries array and the
 * data section, and after the data section. They shall be ignored when parsing
 * the packet.
 *
 * The following diagram describes the layout of the ControlInfoMap packet.
 *
 * ~~~~
 *           +-------------------------+    .                      .
 *  Header / | ipa_controls_header     |    |                      |
 *         | |                         |    |                      |
 *         \ |                         |    |                      |
 *           +-------------------------+    |                      |
 *         / | ipa_control_range_entry |    | hdr.data_offset      |
 *         | | #0                      |    |                      |
 * Control | +-------------------------+    |                      |
 *   range | | ...                     |    |                      |
 * entries | +-------------------------+    |                      |
 *         | | ipa_control_range_entry |    |             hdr.size |
 *         \ | #hdr.entries - 1        |    |                      |
 *           +-------------------------+    |                      |
 *           | empty space (optional)  |    |                      |
 *           +-------------------------+ <--´  .                   |
 *         / | ...                     |       | entry[n].offset   |
 *    Data | | ...                     |       |                   |
 * section | | range data for entry #n | <-----´                   |
 *         \ | ...                     |                           |
 *           +-------------------------+                           |
 *           | empty space (optional)  |                           |
 *           +-------------------------+ <-------------------------´
 * ~~~~
 *
 * The packet header is identical to the ControlList packet header.
 *
 * Entries are described by the ipa_control_range_entry structure. They contain
 * the numerical ID and type of the control. The control range data is stored
 * in the data section as described by the following diagram.
 *
 * ~~~~
 *           +-------------------------+       .
 *         / | ...                     |       | entry[n].offset
 *         | +-------------------------+ <-----´
 *    Data | | minimum value (#n)      | \
 * section | +-------------------------+ | Entry #n
 *         | | maximum value (#n)      | /
 *         | +-------------------------+
 *         \ | ...                     |
 *           +-------------------------+
 * ~~~~
 *
 * The minimum and maximum value are stored in the platform's native data
 * format. The ipa_control_range_entry::offset field stores the offset from the
 * beginning of the data section to the range data.
 *
 * Range data in the data section shall be stored in the same order as the
 * entries array, shall be aligned to a multiple of 8 bytes, and shall be
 * contiguous in memory.
 *
 * As for the ControlList packet, empty spaces may be present between the end of
 * the entries array and the data section, and after the data section. They
 * shall be ignored when parsing the packet.
 */

/**
 * \def IPA_CONTROLS_FORMAT_VERSION
 * \brief The current control serialization format version
 */

/**
 * \struct ipa_controls_header
 * \brief Serialized control packet header
 * \var ipa_controls_header::version
 * Control packet format version number (shall be IPA_CONTROLS_FORMAT_VERSION)
 * \var ipa_controls_header::handle
 * For ControlInfoMap packets, this field contains a unique non-zero handle
 * generated when the ControlInfoMap is serialized. For ControlList packets,
 * this field contains the handle of the corresponding ControlInfoMap.
 * \var ipa_controls_header::entries
 * Number of entries in the packet
 * \var ipa_controls_header::size
 * The total packet size in bytes
 * \var ipa_controls_header::data_offset
 * Offset in bytes from the beginning of the packet of the data section start
 * \var ipa_controls_header::reserved
 * Reserved for future extensions
 */

static_assert(sizeof(ipa_controls_header) == 32,
	      "Invalid ABI size change for struct ipa_control_header");

/**
 * \struct ipa_control_value_entry
 * \brief Description of a serialized ControlValue entry
 * \var ipa_control_value_entry::id
 * The numerical ID of the control
 * \var ipa_control_value_entry::type
 * The type of the control (defined by enum ControlType)
 * \var ipa_control_value_entry::is_array
 * True if the control value stores an array, false otherwise
 * \var ipa_control_value_entry::count
 * The number of control array entries for array controls (1 otherwise)
 * \var ipa_control_value_entry::offset
 * The offset in bytes from the beginning of the data section to the control
 * value data (shall be a multiple of 8 bytes).
 * \var ipa_control_value_entry::padding
 * Padding bytes (shall be set to 0)
 */

static_assert(sizeof(ipa_control_value_entry) == 16,
	      "Invalid ABI size change for struct ipa_control_value_entry");

/**
 * \struct ipa_control_range_entry
 * \brief Description of a serialized ControlRange entry
 * \var ipa_control_range_entry::id
 * The numerical ID of the control
 * \var ipa_control_range_entry::type
 * The type of the control (defined by enum ControlType)
 * \var ipa_control_range_entry::offset
 * The offset in bytes from the beginning of the data section to the control
 * range data (shall be a multiple of 8 bytes)
 * \var ipa_control_range_entry::padding
 * Padding bytes (shall be set to 0)
 */

static_assert(sizeof(ipa_control_range_entry) == 16,
	      "Invalid ABI size change for struct ipa_control_range_entry");