MontaukOS/docs/limine/PROTOCOL.md

# The Limine Boot Protocol

The Limine boot protocol is a modern, portable, featureful, and extensible boot
protocol.

This file serves as the protocol's specification and as the official, centralised
collection of [features](#features) that the Limine boot protocol is comprised of.
Bootloaders may support extra unofficial features, but it is strongly recommended
to avoid fragmentation and submit new features by opening a pull request to the
[limine-protocol Codeberg repository](https://codeberg.org/Limine/limine-protocol).

The [limine.h](include/limine.h) file provides an implementation of all the
structures and constants described in this document, for the C and C++
languages.


---

## Table of Contents

- [General Notes](#general-notes)
- [Requests Delimiters](#requests-delimiters)
- [Limine Requests Section](#limine-requests-section)
- [Base Revisions](#base-revisions)
- [Base Revision Changes Summary](#base-revision-changes-summary)
  - [Base Revision 0](#base-revision-0)
  - [Base Revision 1](#base-revision-1)
  - [Base Revision 2](#base-revision-2)
  - [Base Revision 3](#base-revision-3)
  - [Base Revision 4](#base-revision-4)
- [Memory Layout at Entry](#memory-layout-at-entry)
- [Caching](#caching)
  - [x86-64](#x86-64)
  - [aarch64](#aarch64)
  - [riscv64](#riscv64)
  - [loongarch64](#loongarch64)
- [Machine State at Entry](#machine-state-at-entry)
  - [x86-64](#x86-64-1)
  - [aarch64](#aarch64-1)
  - [riscv64](#riscv64-1)
  - [loongarch64](#loongarch64-1)
- [Features](#features)
  - [Request](#request)
  - [Response](#response)
- [Feature List](#feature-list)
  - [Bootloader Info](#bootloader-info-feature)
  - [Executable Command Line](#executable-command-line-feature)
  - [Firmware Type](#firmware-type-feature)
  - [Stack Size](#stack-size-feature)
  - [HHDM (Higher Half Direct Map)](#hhdm-higher-half-direct-map-feature)
  - [Framebuffer](#framebuffer-feature)
  - [Paging Mode](#paging-mode-feature)
  - [MP (Multiprocessor)](#mp-multiprocessor-feature)
  - [RISC-V BSP Hart ID](#risc-v-bsp-hart-id-feature)
  - [Memory Map](#memory-map-feature)
  - [Entry Point](#entry-point-feature)
  - [Executable File](#executable-file-feature)
  - [Module](#module-feature)
  - [RSDP](#rsdp-feature)
  - [SMBIOS](#smbios-feature)
  - [EFI System Table](#efi-system-table-feature)
  - [EFI Memory Map](#efi-memory-map-feature)
  - [Date at Boot](#date-at-boot-feature)
  - [Executable Address](#executable-address-feature)
  - [Device Tree Blob](#device-tree-blob-feature)
  - [Bootloader Performance](#bootloader-performance-feature)
- [File Structure](#file-structure)

---

## General Notes

The "executable" is the kernel or otherwise the freestanding application being loaded
by the Limine boot protocol compliant bootloader.

The Limine boot protocol does not enforce any specific executable binary format to use,
though ELF is strongly recommended.

Only 64-bit, Little Endian machines are supported or will be supported in the future.

All pointers are 64-bit wide. All non-NULL pointers point to the object with the
[Higher Half Direct Map](#hhdm-higher-half-direct-map-feature) (HHDM) offset already added
to them, unless otherwise noted.

All [responses](#response) and associated data structures are placed in
[bootloader-reclaimable memory](#memory-map-feature) regions.

The ABIs the Limine protocol uses and expects the executable to comply with are as follows:
  - **x86-64**: System V ABI without FP/SIMD
  - **aarch64**: AAPCS64 without FP/SIMD
  - **riscv64**: LP64 (soft-float)
  - **loongarch64**: LP64S (soft-float)

The executable can internally use FP/SIMD, but when interfacing with the Limine boot
protocol, the above are the expected ABIs.

## Requests Delimiters

The bootloader can be told to start and/or stop searching for [requests](#request)
(including [base revision](#base-revisions) tags) in an executable's loaded image by
placing start and/or end markers, on an 8-byte aligned boundary.

The bootloader will only accept requests placed between the last start marker found (if
there happen to be more than 1, which there should not, ideally) and the first end
marker found.
```c
#define LIMINE_REQUESTS_START_MARKER { 0xf6b8f4b39de7d1ae, 0xfab91a6940fcb9cf, \
                                       0x785c6ed015d3e316, 0x181e920a7852b9d9 }

#define LIMINE_REQUESTS_END_MARKER { 0xadc0e0531bb10d03, 0x9572709f31764c62 }
```

For base revisions [0](#base-revision-0) and [1](#base-revision-1), the requests
delimiters are *hints*. The bootloader can still search for requests and base revision
tags outside the delimited area if it doesn't support the hints.

[Base revision 2](#base-revision-2)'s sole difference compared to
[base revision 1](#base-revision-1) is that support for
request delimiters has to be provided and the delimiters must be honoured, if present,
rather than them just being a hint.

## Limine Requests Section

> [!WARNING]
> This behaviour is deprecated and removed as of [base revision 1](#base-revision-1)

For executables requesting deprecated [base revision 0](#base-revision-0),
if the executable file contains a `.limine_reqs` executable section, the bootloader
will, instead of scanning the whole executable's loaded image for [requests](#request),
fetch the requests from a NULL-terminated array of pointers to the provided requests,
contained inside said section.

## Base Revisions

The Limine boot protocol comes in several base revisions; so far, 5
base revisions are specified: [0 through 4](#base-revision-changes-summary).

Base revisions change certain behaviours of the Limine boot protocol
outside any specific feature. The specifics are going to be described as
needed throughout this specification, but are also coalesced in the
[Base Revision Changes Summary](#base-revision-changes-summary) section.

Base revision 0 through 3 are considered deprecated.
[Base revision 0](#base-revision-0) is the default base revision
an executable is assumed to be requesting and complying to if no base revision tag
is provided by the executable, for backwards compatibility.

A base revision tag is a set of 3 64-bit values placed somewhere in the loaded
executable image on an 8-byte aligned boundary; the first 2 values are a magic number
for the bootloader to be able to identify the tag, and the last value is the
requested base revision number.

```c
#define LIMINE_BASE_REVISION(N) { 0xf9562b2d5c95a6c8, 0x6a7b384944536bdc, (N) }
```

If a bootloader drops support for an older base revision, the bootloader must
fail to boot an executable requesting such base revision. If a bootloader does not yet
support a requested base revision (i.e. if the requested base revision is higher
than the maximum base revision supported), it must boot the executable using any
arbitrary revision it supports, and communicate failure to comply to the executable by
*leaving the 3rd component of the base revision tag unchanged*.
On the other hand, if the executable's requested base revision is supported,
*the 3rd component of the base revision tag must be set to 0 by the bootloader*.

> [!NOTE]
> This means that unlike when the bootloader drops support for an older base
> revision and *it* is responsible for failing to boot the executable, in case the
> bootloader does not yet support the executable's requested base revision,
> it is up to the executable itself to fail (or handle the condition otherwise).

For any Limine-compliant bootloader supporting [base revision 3](#base-revision-3)
or greater, it is *mandatory* to load executables requesting higher unsupported base
revisions with at least base revision 3, and it is mandatory for it to always set the
2nd component of the base revision tag to the base revision actually used to load the
executable, regardless of whether it was the requested one or not.

```c
#define LIMINE_BASE_REVISION_SUPPORTED(VAR) ((VAR)[2] == 0)

#define LIMINE_LOADED_BASE_REVISION_VALID(VAR) ((VAR)[1] != 0x6a7b384944536bdc)
#define LIMINE_LOADED_BASE_REVISION(VAR) ((VAR)[1])
```

## Base Revision Changes Summary

This section consolidates all changes introduced by each [base revision](#base-revisions)
for easy reference.

### Base Revision 0

This is the default base revision used if no base revision tag is provided.

- Supports the `.limine_reqs` executable section for providing a list of
    [requests](#request).
- Request delimiters (start/end markers) are treated as hints only.
- Identity mapping (starting at offset 0x1000) available.
- [HHDM](#hhdm-higher-half-direct-map-feature) (Higher Half Direct Map) covers **all**
    memory map regions.
- Memory between 0 and 0x1000 is **never** marked as usable in the
    [memory map](#memory-map-feature).
- **aarch64**: `TTBR0_EL1` points to bootloader-provided identity mapping page tables.

### Base Revision 1

**Changes from Base Revision 0**:
- Dropped support for the `.limine_reqs` executable section [request](#request) search
    method.
- Dropped identity mapping.
- [HHDM](#hhdm-higher-half-direct-map-feature) mappings no longer include
    [memory map regions](#memory-map-feature) of types:
  - Reserved
  - Bad memory
- **aarch64**: `TTBR0_EL1` is now **unspecified** and can be freely used by the executable.
- [Requests delimiters](#requests-delimiters) remain hints only.

### Base Revision 2

**Changes from Base Revision 1**:
- [Requests delimiters](#requests-delimiters) must now be **honoured** if present
    (no longer optional hints).
- All other behaviors remain the same as [base revision 1](#base-revision-1).

### Base Revision 3

**Changes from Base Revision 2**:
- [HHDM](#hhdm-higher-half-direct-map-feature) mapping becomes **restrictive** - only the
    following [memory map regions](#memory-map-feature) are mapped:
  - Usable
  - Bootloader reclaimable
  - Executable and modules
  - Framebuffer
- Dropped unconditional direct map of the first 4 GiB of memory to the
    [Higher Half Direct Map](#hhdm-higher-half-direct-map-feature).
- Memory between 0 and 0x1000 **can now** be marked as usable in the
    [memory map](#memory-map-feature).
- [RSDP](#rsdp-feature) address is returned as **physical** (base revision 3 **only**).
- [SMBIOS](#smbios-feature) entry point addresses are returned as **physical**.
- [EFI system table](#efi-system-table-feature) address is returned as **physical**.
- **Bootloader requirement**: Must support loading executables requesting higher
    unsupported revisions with at least base revision 3.
- **Bootloader requirement**: Must set the 2nd component of the base revision tag to the
    actual base revision used.

### Base Revision 4

**Changes from Base Revision 3**:
- [HHDM](#hhdm-higher-half-direct-map-feature) additionally maps the following
    [memory map regions](#memory-map-feature):
  - ACPI tables
  - ACPI reclaimable
  - ACPI NVS
- Added new [memory map](#memory-map-feature) region type: `LIMINE_MEMMAP_ACPI_TABLES`.
- Guaranteed that ACPI tables (RSDP, RSDT, XSDT, all tables pointed to by RSDT and XSDT,
    FACS, X_FACS, DSDT, X_DSDT) are mapped within any of the ACPI
    [memory map regions](#memory-map-feature).
- [RSDP](#rsdp-feature) address is returned as **virtual**
    **([HHDM](#hhdm-higher-half-direct-map-feature))** again (physical only in
    [base revision 3](#base-revision-3)).
- **aarch64**:
  - `MAIR_EL1.Attr0` is guaranteed to be `0xff` (Normal Write-Back RW-Allocate
      non-transient).
  - `MAIR_EL1.Attr1` is guaranteed to be the framebuffer's correct caching type.
  - All other `MAIR_EL1` entries are guaranteed unused unless specified by a request
      (no such requests are specified yet).

## Memory Layout at Entry

The protocol mandates executables to load themselves at or above
`0xffffffff80000000`. Lower half executables are *not supported*. For relocatable executables
asking to be loaded at address 0, a minimum slide of `0xffffffff80000000` is applied.

A "slide" is an offset applied to the executable's base load address.

At handoff, the executable will be properly loaded and mapped with appropriate
MMU permissions, as supervisor, at the requested virtual memory address (provided it is at
or above `0xffffffff80000000`).

No specific physical memory placement is guaranteed, except that the loaded executable image
is guaranteed to be physically contiguous. In order to determine
where the executable is loaded in physical memory, see the
[Executable Address feature](#executable-address-feature).

Alongside the loaded executable, the bootloader will set up memory mappings as such:

```
 Base Physical Address |                               | Base Virtual Address
 ----------------------+-------------------------------+-----------------------
                       |    (4 GiB - 0x1000) and any   |
  0x0000000000001000   |  additional memory map region |  0x0000000000001000
                       |    (Base revision 0 only)     |
 ----------------------+-------------------------------+-----------------------
                       |     4 GiB and additional      |
  0x0000000000000000   |  memory map regions depending |      HHDM start
                       |       on base revision        |
```
Where "HHDM start" is returned by the [Higher Half Direct Map feature](#hhdm-higher-half-direct-map-feature).
These mappings are supervisor, read, write, execute (-rwx).

When a memory map region is mapped to the Higher Half Direct Map, mappings will use a minimum page size
of 4KiB; if a region's start or end address is not 4KiB aligned, the mappings will overshoot the region
boundaries in order to align to 4KiB while also covering the entire region.

For [base revision 0](#base-revision-0), the above-4GiB identity and HHDM mappings cover any memory
map region.

For [base revisions 1](#base-revision-1) and [2](#base-revision-2), the above-4GiB HHDM mappings do not
comprise memory map regions of types:
 - Reserved
 - Bad memory

For [base revision 3](#base-revision-3) or greater, the only memory map regions mapped to the HHDM are:
 - Usable
 - Bootloader reclaimable
 - Executable and modules
 - Framebuffer

Additionally, the unconditional direct map of the first 4GiB is dropped, and only memory map regions
of complying types are mapped in.

For [base revision 4](#base-revision-4) or greater, the following regions are also mapped in addition
to those mapped by [base revision 3](#base-revision-3):
 - ACPI tables
 - ACPI reclaimable
 - ACPI NVS

The bootloader page tables are in [bootloader-reclaimable memory](#memory-map-feature) (see the
[Memory Map feature](#memory-map-feature)), and their specific layout is undefined as long as they provide
the above memory mappings.

If the executable is a position independent executable, the bootloader is free to
relocate it as it sees fit, potentially performing slide randomisation.

## Caching

### x86-64

The executable, loaded at or above `0xffffffff80000000` in virtual memory, sees all of its
segments mapped using write-back (WB) caching at the page tables level. That being `PAT[0]`, if
the PAT is supported.

All HHDM and identity map memory regions are mapped using write-back (WB) caching at the page
tables level (again, `PAT[0]`), except framebuffer regions which are mapped using write-combining
(WC) caching at the page tables level (`PAT[5]`, if the CPU support the PAT, see below).

If the CPU supports the PAT (Page Attribute Table), its layout is specified to be as follows:
```
PAT0 -> WB
PAT1 -> WT
PAT2 -> UC-
PAT3 -> UC
PAT4 -> WP
PAT5 -> WC
PAT6 -> unspecified
PAT7 -> unspecified
```

The MTRRs are left as the firmware set them up.

### aarch64

The executable, loaded at or above `0xffffffff80000000` in virtual memory, sees all of its
segments mapped using Normal Write-Back RW-Allocate non-transient caching mode (`MAIR_EL1.Attr0`).

All HHDM and identity map memory regions are mapped using the Normal Write-Back RW-Allocate
non-transient caching mode (guaranteed to be in `MAIR_EL1.Attr0` for
[base revision 4](#base-revision-4) or greater), except for the framebuffer regions, which are
mapped in using an unspecified caching mode (guaranteed to be in `MAIR_EL1.Attr1` for
[base revision 4](#base-revision-4) or greater), correct for use with the framebuffer on the platform.

For base revisions < 4, the `MAIR_EL1` register will at least contain entries for the above-mentioned
caching modes, in an unspecified order.

For [base revision 4](#base-revision-4) and greater, `MAIR_EL1.Attr0` is guaranteed to be `0xff` (AKA Normal
Write-Back RW-Allocate non-transient caching mode), `MAIR_EL1.Attr1` is guaranteed to
be the entry used to map the framebuffer, of the correct caching type for it, and all
other entries in `MAIR_EL1` are guaranteed unused unless otherwise specified by a request
(no such requests are specified yet).

### riscv64

The executable, loaded at or above `0xffffffff80000000`, in virtual memory, and all HHDM and
identity map memory regions are mapped with the default `PBMT=PMA`.

If the `Svpbmt` extension is available, all framebuffer memory regions are mapped
with `PBMT=NC` to enable write-combining optimizations.

If the `Svpbmt` extension is not available, no PMAs can be overridden (effectively,
everything is mapped with `PBMT=PMA`).

### loongarch64

The executable, loaded at or above `0xffffffff80000000`, in virtual memory, sees all of its
segments mapped using the Coherent Cached (CC) memory access type (MAT).

All HHDM and identity map memory regions are mapped using the Coherent Cached (CC)
MAT, except for the framebuffer regions, which are mapped in using the
Weakly-ordered UnCached (WUC) MAT.

## Machine State at Entry

### x86-64

`rip` will be the entry point as defined as part of the executable file format,
unless the [Entry Point feature](#entry-point-feature) is requested, in which case, the value
of `rip` is going to be taken from there.

At entry all segment registers are loaded as 64 bit code/data segments, limits
and bases are ignored since this is 64-bit mode.

The GDT register is loaded to point to a GDT, in [bootloader-reclaimable memory](#memory-map-feature),
with at least the following entries, starting at offset 0:

  - Null descriptor
  - 16-bit code descriptor. Base = `0`, limit = `0xffff`. Readable.
  - 16-bit data descriptor. Base = `0`, limit = `0xffff`. Writable.
  - 32-bit code descriptor. Base = `0`, limit = `0xffffffff`. Readable.
  - 32-bit data descriptor. Base = `0`, limit = `0xffffffff`. Writable.
  - 64-bit code descriptor. Base and limit irrelevant. Readable.
  - 64-bit data descriptor. Base and limit irrelevant. Writable.

The IDT is in an undefined state. Executable must load its own.

IF flag, VM flag, and direction flag are cleared on entry. Other flags
undefined.

PG is enabled (`cr0`), PE is enabled (`cr0`), PAE is enabled (`cr4`),
WP is enabled (`cr0`), LME is enabled (`EFER`).
NX is enabled (`EFER`) if available.
If 5-level paging is requested and available, then 5-level paging is enabled
(LA57 bit in `cr4`).

The A20 gate is opened.

Legacy PIC (if available) and IO APIC IRQs (only those with delivery mode fixed
(0b000) or lowest priority (0b001)) are all masked.

If booted by EFI, boot services are exited.

`rsp` is set to point to the top of a stack, in [bootloader-reclaimable memory](#memory-map-feature),
which is at least 64KiB (65536 bytes) in size, or the size specified in the
[Stack Size feature](#stack-size-feature). An invalid return address of 0 is pushed
to this stack before jumping to the executable's entry point.

All other general purpose registers (`rax`-`r15`) are set to 0.

### aarch64

`PC` will be the entry point as defined as part of the executable file format,
unless the [Entry Point feature](#entry-point-feature) is requested, in which case,
the value of `PC` is going to be taken from there.

The contents of the `VBAR_EL1` register are undefined, and the executable must load
its own.

The `MAIR_EL1` register contents are described above, in the [caching section](#caching).

All interrupts are masked (`PSTATE.{D, A, I, F}` are set to 1).

The executable is entered in little-endian AArch64 EL1t (EL1 with `PSTATE.SP` set to
0, `PSTATE.E` set to 0, and `PSTATE.nRW` set to 0).

Other fields of `PSTATE` are undefined.

At entry: the MMU (`SCTLR_EL1.M`) is enabled, the I-Cache and D-Cache
(`SCTLR_EL1.{I, C}`) are enabled, data alignment checking (`SCTLR_EL1.A`) is
disabled. SP alignment checking (`SCTLR_EL1.{SA, SA0}`) is enabled. Other fields
of `SCTLR_EL1` are reset to 0 or to their reserved value.

Higher ELs do not interfere with accesses to vector or floating point
instructions or registers.

Higher ELs do not interfere with accesses to the generic timer and counter.

The used translation granule size for both `TTBR0_EL1` and `TTBR1_EL1` is 4KiB.

`TCR_EL1.{T0SZ, T1SZ}` are set to 16 under 4-level paging, or 12 under 5-level
paging. Additionally, for 5-level paging, `TCR_EL1.DS` is set to 1.

`TTBR1_EL1` points to the bootloader-provided higher half page tables.
For [base revision 0](#base-revision-0), `TTBR0_EL1` points to the bootloader-provided identity
mapping page tables, and is unspecified for all other base revisions and can
thus be freely used by the executable.

If booted by EFI, boot services are exited.

`SP` is set to point to the top of a stack, in [bootloader-reclaimable memory](#memory-map-feature),
which is at least 64KiB (65536 bytes) in size, or the size specified in the
[Stack Size feature](#stack-size-feature).

All other general purpose registers (including `X29` and `X30`) are set to 0.
Vector registers are in an undefined state.

### riscv64

At entry the machine is executing in Supervisor mode.

`pc` will be the entry point as defined as part of the executable file format,
unless the [Entry Point feature](#entry-point-feature) is requested, in which case, the
value of `pc` is going to be taken from there.

`x1`(`ra`) is set to 0, the executable must not return from the entry point.

`x2`(`sp`) is set to point to the top of a stack, in [bootloader-reclaimable memory](#memory-map-feature),
which is at least 64KiB (65536 bytes) in size, or the size specified in the
[Stack Size feature](#stack-size-feature).

`x3`(`gp`) is set to 0, executable must load its own global pointer if needed.

All other general purpose registers, with the exception of `x5`(`t0`), are set to 0.

If booted by EFI, boot services are exited.

`stvec` is in an undefined state. `sstatus.SIE` and `sie` are set to 0.

`sstatus.FS` and `sstatus.XS` are both set to `Off`.

Paging is enabled with the paging mode specified by the [Paging Mode feature](#paging-mode-feature).

The (A)PLIC, if present, is in an undefined state.

### loongarch64

At entry the machine is executing in PLV0.

`$pc` will be the entry point as defined as part of the executable file format,
unless the [Entry Point feature](#entry-point-feature) is requested, in which case, the
value of `$pc` is going to be taken from there.

`$r1`(`$ra`) is set to 0, the executable must not return from the entry point.

`$r3`(`$sp`) is set to point to the top of a stack, in [bootloader-reclaimable memory](#memory-map-feature),
which is at least 64KiB (65536 bytes) in size, or the size specified in the
[Stack Size feature](#stack-size-feature).

All other general purpose registers, with the exception of `$r12`(`$t0`), are set to 0.

If booted by EFI, boot services are exited.

`CSR.EENTRY`, `CSR.MERRENTRY` and `CSR.DWM0-3` are in an undefined state.

`PG` in `CSR.CRMD` is 1, `DA` is 0, `IE` is 0 and `PLV` is 0 but is otherwise unspecified.

`CSR.TLBRENTRY` is filled with a provided TLB refill handler.

## Features

The protocol is centered around the concept of request/response - collectively
named "features" - where the executable requests some action or information from
the bootloader, and the bootloader responds accordingly, if it is capable of
doing so.

In C terms, a feature is comprised of 2 structures: the request, and the response.

### Request

A request has 3 mandatory members at the beginning of the structure:
```c
struct limine_example_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_example_response *response;
    ... optional members follow ...
};
```
* `id` - The ID of the request. This is an 8-byte aligned magic number that the
    bootloader will scan for inside the loaded executable image to find requests.
    Request IDs are composed of 4 64-bit unsigned integers, but the first 2 are
    common to every request:
    ```c
    #define LIMINE_COMMON_MAGIC 0xc7b1dd30df4c8b88, 0x0a82e883a194f07b
    ```
    Requests may be located anywhere inside the loaded executable image as long as they are
    8-byte aligned. There may only be 1 of the same request. The bootloader will refuse
    to boot an executable with multiple of the same request IDs.
* `revision` - The revision of the request that the executable provides. This starts at 0 and is
bumped whenever new members or functionality are added to the request structure.
Bootloaders process requests in a backwards compatible manner, *always*. This
means that if the bootloader does not support the revision of the request,
it will process the request as if it were the highest revision that the bootloader
supports.
* `response` - This field is filled in by the bootloader at load time, with a
pointer to the response structure, if the request was successfully processed.
If the request is unsupported or was not successfully processed, this field
is *left untouched*, meaning that if it was set to `NULL`, it will stay that
way.

### Response

A response has only 1 mandatory member at the beginning of the structure:
```c
struct limine_example_response {
    uint64_t revision;
    ... optional members follow ...
};
```
* `revision` - Like for requests, bootloaders will instead mark responses with a
revision number. This revision is not coupled between requests and responses,
as they are bumped individually when new members are added or functionality is
changed. Bootloaders will set the revision to the one they provide, and this is
*always backwards compatible*, meaning higher revisions support all that lower
revisions do.

This is all there is to features. For a list of official Limine features, read
the "Feature List" section below.

## Feature List

### Bootloader Info Feature

ID:
```c
#define LIMINE_BOOTLOADER_INFO_REQUEST_ID { LIMINE_COMMON_MAGIC, 0xf55038d8e2a1202f, 0x279426fcf5f59740 }
```

Request:
```c
struct limine_bootloader_info_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_bootloader_info_response *response;
};
```

Response:
```c
struct limine_bootloader_info_response {
    uint64_t revision;
    char *name;
    char *version;
};
```

`name` and `version` are 0-terminated ASCII strings containing the name and
version of the loading bootloader.

### Executable Command Line Feature

ID:
```c
#define LIMINE_EXECUTABLE_CMDLINE_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x4b161536e598651e, 0xb390ad4a2f1f303a }
```

Request:
```c
struct limine_executable_cmdline_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_executable_cmdline_response *response;
};
```

Response:
```c
struct limine_executable_cmdline_response {
    uint64_t revision;
    char *cmdline;
};
```

`cmdline` is a 0-terminated ASCII string containing the command line associated with the
booted executable. This is a pointer to the same memory as the `string` member of the `executable_file`
structure of the [Executable File feature](#executable-file-feature).

### Firmware Type Feature

ID:
```c
#define LIMINE_FIRMWARE_TYPE_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x8c2f75d90bef28a8, 0x7045a4688eac00c3 }
```

Request:
```c
struct limine_firmware_type_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_firmware_type_response *response;
};
```

Response:
```c
struct limine_firmware_type_response {
    uint64_t revision;
    uint64_t firmware_type;
};
```

`firmware_type` is an enumeration that can have one of the following values:
```c
#define LIMINE_FIRMWARE_TYPE_X86BIOS 0
#define LIMINE_FIRMWARE_TYPE_EFI32 1
#define LIMINE_FIRMWARE_TYPE_EFI64 2
#define LIMINE_FIRMWARE_TYPE_SBI 3
```

### Stack Size Feature

ID:
```c
#define LIMINE_STACK_SIZE_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x224ef0460a8e8926, 0xe1cb0fc25f46ea3d }
```

Request:
```c
struct limine_stack_size_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_stack_size_response *response;
    uint64_t stack_size;
};
```

* `stack_size` - The requested stack size in bytes (also used for MP processors).

Response:
```c
struct limine_stack_size_response {
    uint64_t revision;
};
```

### HHDM (Higher Half Direct Map) Feature

ID:
```c
#define LIMINE_HHDM_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x48dcf1cb8ad2b852, 0x63984e959a98244b }
```

Request:
```c
struct limine_hhdm_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_hhdm_response *response;
};
```

Response:
```c
struct limine_hhdm_response {
    uint64_t revision;
    uint64_t offset;
};
```

* `offset` - the virtual address offset of the beginning of the higher half
direct map.

### Framebuffer Feature

ID:
```c
#define LIMINE_FRAMEBUFFER_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x9d5827dcd881dd75, 0xa3148604f6fab11b }
```

Request:
```c
struct limine_framebuffer_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_framebuffer_response *response;
};
```

Response:
```c
struct limine_framebuffer_response {
    uint64_t revision;
    uint64_t framebuffer_count;
    struct limine_framebuffer **framebuffers;
};
```

* `framebuffer_count` - How many framebuffers are present.
* `framebuffers` - Pointer to an array of `framebuffer_count` pointers to
`struct limine_framebuffer` structures.

> [!NOTE]
> If no framebuffer is available, no response will be provided.

```c
// Constants for `memory_model`
#define LIMINE_FRAMEBUFFER_RGB 1

struct limine_framebuffer {
    void *address;
    uint64_t width;
    uint64_t height;
    uint64_t pitch;
    uint16_t bpp; // Bits per pixel
    uint8_t memory_model;
    uint8_t red_mask_size;
    uint8_t red_mask_shift;
    uint8_t green_mask_size;
    uint8_t green_mask_shift;
    uint8_t blue_mask_size;
    uint8_t blue_mask_shift;
    uint8_t unused[7];
    uint64_t edid_size;
    void *edid;

    /* Response revision 1 */
    uint64_t mode_count;
    struct limine_video_mode **modes;
};
```

`edid` points to the screen's EDID blob, if available, else NULL.

`modes` is an array of `mode_count` pointers to `struct limine_video_mode` describing the
available video modes for the given framebuffer.

```c
struct limine_video_mode {
    uint64_t pitch;
    uint64_t width;
    uint64_t height;
    uint16_t bpp;
    uint8_t memory_model;
    uint8_t red_mask_size;
    uint8_t red_mask_shift;
    uint8_t green_mask_size;
    uint8_t green_mask_shift;
    uint8_t blue_mask_size;
    uint8_t blue_mask_shift;
};
```

### Paging Mode Feature

The Paging Mode feature allows the executable to control which paging mode is enabled
before control is passed to it.

ID:
```c
#define LIMINE_PAGING_MODE_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x95c1a0edab0944cb, 0xa4e5cb3842f7488a }
```

Request:
```c
struct limine_paging_mode_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_paging_mode_response *response;
    uint64_t mode;
    /* Request revision 1 and above */
    uint64_t max_mode;
    uint64_t min_mode;
};
```

* `mode` - the preferred paging mode by the OS; the bootloader should always aim
to pick this mode unless unavailable or overridden by the user in the bootloader's
configuration file.
* `max_mode` - the highest paging mode in numerical order that the OS supports. The
bootloader will refuse to boot the OS if no paging modes of this type or lower
(but equal or greater than `min_mode`) are available.
* `min_mode` - the lowest paging mode in numerical order that the OS supports. The
bootloader will refuse to boot the OS if no paging modes of this type or greater
(but equal or lower than `max_mode`) are available.

If no Paging Mode Request is provided, the values of `mode`, `max_mode`, and `min_mode`
that the bootloader assumes are `LIMINE_PAGING_MODE_<arch>_DEFAULT`,
`LIMINE_PAGING_MODE_<arch>_DEFAULT`, and `LIMINE_PAGING_MODE_<arch>_MIN`, respectively.

If request revision 0 is used, the values of `max_mode` and `min_mode` that the
bootloader assumes are the value of `mode` and `LIMINE_PAGING_MODE_<arch>_MIN`,
respectively.

Response:
```c
struct limine_paging_mode_response {
    uint64_t revision;
    uint64_t mode;
};
```

The response indicates which paging mode was actually enabled by the bootloader.

#### x86-64

Values assignable to `mode`, `max_mode`, and `min_mode`:
```c
#define LIMINE_PAGING_MODE_X86_64_4LVL 0
#define LIMINE_PAGING_MODE_X86_64_5LVL 1

#define LIMINE_PAGING_MODE_X86_64_DEFAULT LIMINE_PAGING_MODE_X86_64_4LVL
#define LIMINE_PAGING_MODE_X86_64_MIN LIMINE_PAGING_MODE_X86_64_4LVL
```

#### aarch64

Values assignable to `mode`, `max_mode`, and `min_mode`:
```c
#define LIMINE_PAGING_MODE_AARCH64_4LVL 0
#define LIMINE_PAGING_MODE_AARCH64_5LVL 1

#define LIMINE_PAGING_MODE_AARCH64_DEFAULT LIMINE_PAGING_MODE_AARCH64_4LVL
#define LIMINE_PAGING_MODE_AARCH64_MIN LIMINE_PAGING_MODE_AARCH64_4LVL
```

#### riscv64

Values assignable to `mode`, `max_mode`, and `min_mode`:
```c
#define LIMINE_PAGING_MODE_RISCV_SV39 0
#define LIMINE_PAGING_MODE_RISCV_SV48 1
#define LIMINE_PAGING_MODE_RISCV_SV57 2

#define LIMINE_PAGING_MODE_RISCV_DEFAULT LIMINE_PAGING_MODE_RISCV_SV48
#define LIMINE_PAGING_MODE_RISCV_MIN LIMINE_PAGING_MODE_RISCV_SV39
```

#### loongarch64

Values assignable to `mode`, `max_mode`, and `min_mode`:
```c
#define LIMINE_PAGING_MODE_LOONGARCH_4LVL 0

#define LIMINE_PAGING_MODE_LOONGARCH_DEFAULT LIMINE_PAGING_MODE_LOONGARCH_4LVL
#define LIMINE_PAGING_MODE_LOONGARCH_MIN LIMINE_PAGING_MODE_LOONGARCH_4LVL
```

### MP (Multiprocessor) Feature

ID:
```c
#define LIMINE_MP_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x95a67b819a1b857e, 0xa0b61b723b6a73e0 }
```

Request:
```c
#define LIMINE_MP_REQUEST_X86_64_X2APIC (1 << 0)

struct limine_mp_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_mp_response *response;
    uint64_t flags;
};
```

* `flags` - Bit 0: Enable x2APIC, if possible. (x86-64 only)

> [!NOTE]
> The presence of this request will prompt the bootloader to bootstrap
> the secondary processors. This will not be done if this request is not present.

> [!NOTE]
> If this request is supported, even on single-processor system, a response will be provided,
> containing only the bootstrap processor's entry.

#### x86-64:

Response:

```c
#define LIMINE_MP_RESPONSE_X86_64_X2APIC (1 << 0)

struct limine_mp_response {
    uint64_t revision;
    uint32_t flags;
    uint32_t bsp_lapic_id;
    uint64_t cpu_count;
    struct limine_mp_info **cpus;
};
```

* `flags` - Bit 0: x2APIC has been enabled.
* `bsp_lapic_id` - The Local APIC ID of the bootstrap processor.
* `cpu_count` - How many CPUs are present. It includes the bootstrap processor.
* `cpus` - Pointer to an array of `cpu_count` pointers to
`struct limine_mp_info` structures.

> [!NOTE]
> The MTRRs of APs will be synchronised by the bootloader to match
> the BSP, as Intel SDM requires (Vol. 3A, 12.11.5).

```c
struct limine_mp_info;

typedef void (*limine_goto_address)(struct limine_mp_info *);

struct limine_mp_info {
    uint32_t processor_id;
    uint32_t lapic_id;
    uint64_t reserved;
    limine_goto_address goto_address;
    uint64_t extra_argument;
};
```

* `processor_id` - ACPI Processor UID as specified by the MADT
* `lapic_id` - Local APIC ID of the processor as specified by the MADT
* `goto_address` - An atomic write to this field causes the parked CPU to
jump to the written address, on a 64KiB (or [Stack Size feature](#stack-size-feature) size) stack. A pointer to the
`struct limine_mp_info` structure of the CPU is passed in `RDI`. Other than
that, the CPU state will be the same as described for the bootstrap
processor. This field is unused for the structure describing the bootstrap
processor. For all CPUs, this field is guaranteed to be NULL when control is first passed
to the bootstrap processor.
* `extra_argument` - A free for use field.

#### aarch64:

Response:

```c
struct limine_mp_response {
    uint64_t revision;
    uint64_t flags;
    uint64_t bsp_mpidr;
    uint64_t cpu_count;
    struct limine_mp_info **cpus;
};
```

* `flags` - Always zero
* `bsp_mpidr` - MPIDR of the bootstrap processor (as read from `MPIDR_EL1`, with Res1 masked off).
* `cpu_count` - How many CPUs are present. It includes the bootstrap processor.
* `cpus` - Pointer to an array of `cpu_count` pointers to
`struct limine_mp_info` structures.

```c
struct limine_mp_info;

typedef void (*limine_goto_address)(struct limine_mp_info *);

struct limine_mp_info {
    uint32_t processor_id;
    uint32_t reserved1;
    uint64_t mpidr;
    uint64_t reserved;
    limine_goto_address goto_address;
    uint64_t extra_argument;
};
```

* `processor_id` - ACPI Processor UID as specified by the MADT (always 0 on non-ACPI systems).
* `mpidr` - MPIDR of the processor as specified by the MADT or device tree.
* `goto_address` - An atomic write to this field causes the parked CPU to
jump to the written address, on a 64KiB (or [Stack Size feature](#stack-size-feature) size) stack. A pointer to the
`struct limine_mp_info` structure of the CPU is passed in `X0`. Other than
that, the CPU state will be the same as described for the bootstrap
processor. This field is unused for the structure describing the bootstrap
processor.
* `extra_argument` - A free for use field.

#### riscv64

Response:

```c
struct limine_mp_response {
    uint64_t revision;
    uint64_t flags;
    uint64_t bsp_hartid;
    uint64_t cpu_count;
    struct limine_mp_info **cpus;
};
```

* `flags` - Always zero
* `bsp_hartid` - Hart ID of the bootstrap processor as reported by the EFI RISC-V Boot Protocol or the SBI.
* `cpu_count` - How many CPUs are present. It includes the bootstrap processor.
* `cpus` - Pointer to an array of `cpu_count` pointers to
`struct limine_mp_info` structures.

```c
struct limine_mp_info;

typedef void (*limine_goto_address)(struct limine_mp_info *);

struct limine_mp_info {
    uint64_t processor_id;
    uint64_t hartid;
    uint64_t reserved;
    limine_goto_address goto_address;
    uint64_t extra_argument;
};
```

* `processor_id` - ACPI Processor UID as specified by the MADT (always 0 on non-ACPI systems).
* `hartid` - Hart ID of the processor as specified by the MADT or Device Tree.
* `goto_address` - An atomic write to this field causes the parked CPU to
jump to the written address, on a 64KiB (or [Stack Size feature](#stack-size-feature) size) stack. A pointer to the
`struct limine_mp_info` structure of the CPU is passed in `x10`(`a0`). Other than
that, the CPU state will be the same as described for the bootstrap
processor. This field is unused for the structure describing the bootstrap
processor.
* `extra_argument` - A free for use field.

### RISC-V BSP Hart ID Feature

ID:
```c
#define LIMINE_RISCV_BSP_HARTID_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x1369359f025525f9, 0x2ff2a56178391bb6 }
```

Request:
```c
struct limine_riscv_bsp_hartid_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_riscv_bsp_hartid_response *response;
};
```

Response:
```c
struct limine_riscv_bsp_hartid_response {
    uint64_t revision;
    uint64_t bsp_hartid;
};
```

* `bsp_hartid` - The Hart ID of the boot processor.

> [!NOTE]
> This request contains the same information as `limine_mp_response.bsp_hartid` from the
> [MP feature](#mp-multiprocessor-feature), but doesn't boot up other APs.

> [!NOTE]
> On non-RISC-V platforms, no response will be provided.

### Memory Map Feature

ID:
```c
#define LIMINE_MEMMAP_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x67cf3d9d378a806f, 0xe304acdfc50c3c62 }
```

Request:
```c
struct limine_memmap_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_memmap_response *response;
};
```

Response:
```c
struct limine_memmap_response {
    uint64_t revision;
    uint64_t entry_count;
    struct limine_memmap_entry **entries;
};
```

* `entry_count` - How many memory map entries are present.
* `entries` - Pointer to an array of `entry_count` pointers to
`struct limine_memmap_entry` structures.

```c
// Constants for `type`
#define LIMINE_MEMMAP_USABLE                 0
#define LIMINE_MEMMAP_RESERVED               1
#define LIMINE_MEMMAP_ACPI_RECLAIMABLE       2
#define LIMINE_MEMMAP_ACPI_NVS               3
#define LIMINE_MEMMAP_BAD_MEMORY             4
#define LIMINE_MEMMAP_BOOTLOADER_RECLAIMABLE 5
#define LIMINE_MEMMAP_EXECUTABLE_AND_MODULES 6
#define LIMINE_MEMMAP_FRAMEBUFFER            7
#define LIMINE_MEMMAP_ACPI_TABLES            8

struct limine_memmap_entry {
    uint64_t base;
    uint64_t length;
    uint64_t type;
};
```

* `LIMINE_MEMMAP_USABLE` entries represent regions of the address space that are usable RAM,
and do not contain other data, the executable, bootloader information, or anything valuable,
and are therefore free for use.

* `LIMINE_MEMMAP_RESERVED` entries represent regions of the address space that are
reserved for unspecified purposes by the firmware, hardware, or otherwise, and should not
be touched by the executable.

* `LIMINE_MEMMAP_ACPI_RECLAIMABLE` entries represent regions of the address space containing
ACPI related data, such as ACPI tables and AML code. The executable should make absolutely
sure that no data contained in these regions is still needed before deciding to reclaim
these memory regions for itself. Refer to the ACPI specification for further information.

* `LIMINE_MEMMAP_ACPI_NVS` entries represent regions of the address space used for ACPI
non-volatile data storage. Refer to the ACPI specification for further information.

* `LIMINE_MEMMAP_BAD_MEMORY` entries represent regions of the address space that contain
bad RAM, which may be unreliable, and therefore these regions should be treated the same
as reserved regions.

* `LIMINE_MEMMAP_BOOTLOADER_RECLAIMABLE` entries represent regions of the address space
containing RAM used to store bootloader or firmware information that should be available
to the executable (or, in some cases, hardware, such as for MP trampolines). The executable
should make absolutely sure that no data contained in these regions is still needed before
deciding to reclaim these memory regions for itself.

* `LIMINE_MEMMAP_EXECUTABLE_AND_MODULES` entries are meant to have an illustrative purpose
only, and are not authoritative sources to be used as a means to find the addresses of the
executable or modules. One must use the specific Limine features ([Executable Address](#executable-address-feature) and
[Module](#module-feature) features) to do that.

* `LIMINE_MEMMAP_FRAMEBUFFER` entries represent regions of the address space containing
memory-mapped framebuffers. These entries exist for illustrative purposes only, and are
not to be used to acquire the address of any framebuffer. One must use the [Framebuffer
feature](#framebuffer-feature) for that.

* `LIMINE_MEMMAP_ACPI_TABLES` ([base revision 4](#base-revision-4) or greater) entries represent regions
of the address space containing the ACPI tables as described by the [Memory Layout at Entry](#memory-layout-at-entry)
section, if the firmware did not already map them within either an ACPI reclaimable
or an ACPI NVS region.

For [base revisions](#base-revisions) <= 2, memory between 0 and 0x1000 is never marked as usable memory.

For [base revision 4](#base-revision-4) or greater, ACPI tables (that being RSDP, RSDT, XSDT, all
tables pointed to by RSDT and XSDT, FACS, X_FACS, DSDT, X_DSDT - if present) are guaranteed
to be mapped within any of the 3 ACPI memory map regions.

The entries are guaranteed to be sorted by base address, lowest to highest.

Usable and bootloader reclaimable entries are guaranteed to be 4096 byte aligned for
both base and length.

Usable and bootloader reclaimable entries are guaranteed not to overlap with any other
entry. To the contrary, all non-usable entries (including executable/modules) are
not guaranteed any alignment, nor is it guaranteed that they do not overlap
other entries.

#### EFI Memory Map Entry Type to Limine Memory Map Type

In case the booting firmware is EFI, the following EFI memory map entry types to Limine memory map type
are guaranteed to be upheld, unless overridden by any previous rules:

* EfiLoaderCode, EfiLoaderData -> `BOOTLOADER_RECLAIMABLE`
* EfiBootServicesCode, EfiBootServicesData -> `BOOTLOADER_RECLAIMABLE`
* EfiACPIReclaimMemory -> `ACPI_RECLAIMABLE`
* EfiACPIMemoryNVS -> `ACPI_NVS`
* EfiConventionalMemory -> `USABLE`
* [anything else] -> `RESERVED`

### Entry Point Feature

ID:
```c
#define LIMINE_ENTRY_POINT_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x13d86c035a1cd3e1, 0x2b0caa89d8f3026a }
```

Request:
```c
typedef void (*limine_entry_point)(void);

struct limine_entry_point_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_entry_point_response *response;
    limine_entry_point entry;
};
```

* `entry` - The requested entry point.

Response:
```c
struct limine_entry_point_response {
    uint64_t revision;
};
```

### Executable File Feature

ID:
```c
#define LIMINE_EXECUTABLE_FILE_REQUEST_ID { LIMINE_COMMON_MAGIC, 0xad97e90e83f1ed67, 0x31eb5d1c5ff23b69 }
```

Request:
```c
struct limine_executable_file_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_executable_file_response *response;
};
```

Response:
```c
struct limine_executable_file_response {
    uint64_t revision;
    struct limine_file *executable_file;
};
```

* `executable_file` - Pointer to the `struct limine_file` structure (see
[File Structure](#file-structure) below).
for the executable file. The `string` member is a pointer to the same memory as the `cmdline` value
as reported by the [Executable Command Line feature](#executable-command-line-feature).

### Module Feature

ID:
```c
#define LIMINE_MODULE_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x3e7e279702be32af, 0xca1c4f3bd1280cee }
```

Request:
```c
#define LIMINE_INTERNAL_MODULE_REQUIRED (1 << 0)
#define LIMINE_INTERNAL_MODULE_COMPRESSED (1 << 1)

struct limine_internal_module {
    const char *path;
    const char *string;
    uint64_t flags;
};

struct limine_module_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_module_response *response;

    /* Request revision 1 */
    uint64_t internal_module_count;
    struct limine_internal_module **internal_modules;
};
```

* `internal_module_count` - How many internal modules are passed by the executable.
* `internal_modules` - Pointer to an array of `internal_module_count` pointers to
`struct limine_internal_module` structures.

> [!NOTE]
> Internal modules are honoured if the module response has revision >= 1.

As part of `struct limine_internal_module`:

* `path` - Path to the module to load. This path is *relative* to the location of
the executable.
* `string` - String associated with the given module.
* `flags` - Flags changing module loading behaviour:
  - `LIMINE_INTERNAL_MODULE_REQUIRED`: Fail if the requested module is not found.
  - `LIMINE_INTERNAL_MODULE_COMPRESSED`: Deprecated. Bootloader may not support
    it and panic instead (from Limine 8.x onwards). Alternatively: the module
    is GZ-compressed and should be decompressed by the bootloader. This is
    honoured if the response is revision 2 or greater.

Internal Limine modules are guaranteed to be loaded *before* user-specified
(configuration) modules, and thus they are guaranteed to appear before user-specified
modules in the `modules` array in the response.

Response:
```c
struct limine_module_response {
    uint64_t revision;
    uint64_t module_count;
    struct limine_file **modules;
};
```

* `module_count` - How many modules are present.
* `modules` - Pointer to an array of `module_count` pointers to
`struct limine_file` structures (see [File Structure](#file-structure) below).

> [!NOTE]
> If no modules are available, no response will be provided.

### RSDP Feature

ID:
```c
#define LIMINE_RSDP_REQUEST_ID { LIMINE_COMMON_MAGIC, 0xc5e77b6b397e7b43, 0x27637845accdcf3c }
```

Request:
```c
struct limine_rsdp_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_rsdp_response *response;
};
```

Response:
```c
struct limine_rsdp_response {
    uint64_t revision;
    void *address;
};
```

* `address` - Address of the RSDP table. Physical for [base revision 3](#base-revision-3) **only**.

> [!NOTE]
> If ACPI is not available, no response will not be provided.

### SMBIOS Feature

ID:
```c
#define LIMINE_SMBIOS_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x9e9046f11e095391, 0xaa4a520fefbde5ee }
```

Request:
```c
struct limine_smbios_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_smbios_response *response;
};
```

Response:
```c
struct limine_smbios_response {
    uint64_t revision;
    uint64_t entry_32;
    uint64_t entry_64;
};
```

* `entry_32` - Address of the 32-bit SMBIOS entry point. NULL if not present. Physical for [base revision](#base-revisions) >= 3.
* `entry_64` - Address of the 64-bit SMBIOS entry point. NULL if not present. Physical for [base revision](#base-revisions) >= 3.

> [!NOTE]
> If SMBIOS is not available (that being neither a 32, nor a 64-bit entry points are available), no
> response will be provided.

### EFI System Table Feature

ID:
```c
#define LIMINE_EFI_SYSTEM_TABLE_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x5ceba5163eaaf6d6, 0x0a6981610cf65fcc }
```

Request:
```c
struct limine_efi_system_table_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_efi_system_table_response *response;
};
```

Response:
```c
struct limine_efi_system_table_response {
    uint64_t revision;
    uint64_t address;
};
```

* `address` - Address of EFI system table. Physical for [base revision](#base-revisions) >= 3.

> [!NOTE]
> If EFI is not available, no response will be provided.

### EFI Memory Map Feature

ID:
```c
#define LIMINE_EFI_MEMMAP_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x7df62a431d6872d5, 0xa4fcdfb3e57306c8 }
```

Request:
```c
struct limine_efi_memmap_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_efi_memmap_response *response;
};
```

Response:
```c
struct limine_efi_memmap_response {
    uint64_t revision;
    void *memmap;
    uint64_t memmap_size;
    uint64_t desc_size;
    uint64_t desc_version;
};
```

* `memmap` - Address (HHDM, in [bootloader reclaimable memory](#memory-map-feature)) of the EFI memory map.
* `memmap_size` - Size in bytes of the EFI memory map.
* `desc_size` - EFI memory map descriptor size in bytes.
* `desc_version` - Version of EFI memory map descriptors.

> [!NOTE]
> This feature provides data suitable for use with `RT->SetVirtualAddressMap()`, provided
> [HHDM](#hhdm-higher-half-direct-map-feature) offset is subtracted from `memmap`.

> [!NOTE]
> If EFI is not available, no response will be provided.

### Date at Boot Feature

ID:
```c
#define LIMINE_DATE_AT_BOOT_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x502746e184c088aa, 0xfbc5ec83e6327893 }
```

Request:
```c
struct limine_date_at_boot_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_date_at_boot_response *response;
};
```

Response:
```c
struct limine_date_at_boot_response {
    uint64_t revision;
    int64_t timestamp;
};
```

* `timestamp` - The UNIX timestamp, in seconds, taken from the system RTC, representing the date and time of boot.

### Executable Address Feature

ID:
```c
#define LIMINE_EXECUTABLE_ADDRESS_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x71ba76863cc55f63, 0xb2644a48c516a487 }
```

Request:
```c
struct limine_executable_address_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_executable_address_response *response;
};
```

Response:
```c
struct limine_executable_address_response {
    uint64_t revision;
    uint64_t physical_base;
    uint64_t virtual_base;
};
```

* `physical_base` - The physical base address of the executable.
* `virtual_base` - The virtual base address of the executable.

### Device Tree Blob Feature

ID:
```c
#define LIMINE_DTB_REQUEST_ID { LIMINE_COMMON_MAGIC, 0xb40ddb48fb54bac7, 0x545081493f81ffb7 }
```

Request:
```c
struct limine_dtb_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_dtb_response *response;
};
```

Response:
```c
struct limine_dtb_response {
    uint64_t revision;
    void *dtb_ptr;
};
```

* `dtb_ptr` - Virtual (HHDM) pointer to the device tree blob, in [bootloader reclaimable memory](#memory-map-feature).

> [!NOTE]
> If no DTB is available, no response will be provided.

> [!NOTE]
> Information contained in the `/chosen` node may not reflect the information
> given by bootloader tags, and as such the `/chosen` node properties should be ignored.

> [!NOTE]
> If the DTB contained `memory@...` nodes, they will get removed.
> Executables may not rely on these nodes and should use the [Memory Map feature](#memory-map-feature) instead.

### Bootloader Performance Feature

ID:
```c
#define LIMINE_BOOTLOADER_PERFORMANCE_REQUEST_ID { LIMINE_COMMON_MAGIC, 0x6b50ad9bf36d13ad, 0xdc4c7e88fc759e17 }
```

Request:
```c
struct limine_bootloader_performance_request {
    uint64_t id[4];
    uint64_t revision;
    struct limine_bootloader_performance_response *response;
};
```

Response:
```c
struct limine_bootloader_performance_response {
    uint64_t revision;
    uint64_t reset_usec;
    uint64_t init_usec;
    uint64_t exec_usec;
};
```

* `reset_usec` - time of system reset in microseconds relative to an arbitrary point in the past.
* `init_usec` - time of bootloader initialisation in microseconds relative to an arbitrary point in
the past.
* `exec_usec` - time of executable handoff in microseconds relative to an arbitrary point in the
past.

> [!NOTE]
> Data provided by this feature is purely informational. The ACPI Firmware Performance Data
> Table may have more correct data and should be preferred if it exists. Bootloaders may implement
> this feature using the FPDT.

> [!NOTE]
> The bootloader may assume `reset_usec` is zero if it cannot or does not know the time of
> system reset, due to implementation or platform restrictions. `reset_usec` will usually be 0 or a
> value near zero, but may be any value relative to any point in the past.

## File Structure

```c
struct limine_uuid {
    uint32_t a;
    uint16_t b;
    uint16_t c;
    uint8_t d[8];
};

#define LIMINE_MEDIA_TYPE_GENERIC 0
#define LIMINE_MEDIA_TYPE_OPTICAL 1
#define LIMINE_MEDIA_TYPE_TFTP 2

struct limine_file {
    uint64_t revision;
    void *address;
    uint64_t size;
    char *path;
    char *string;
    uint32_t media_type;
    uint32_t unused;
    uint32_t tftp_ip;
    uint32_t tftp_port;
    uint32_t partition_index;
    uint32_t mbr_disk_id;
    struct limine_uuid gpt_disk_uuid;
    struct limine_uuid gpt_part_uuid;
    struct limine_uuid part_uuid;
};
```

* `revision` - Revision of the `struct limine_file` structure.
* `address` - The address of the file. This is always at least 4KiB aligned.
* `size` - The size of the file. Regardless of the file size, all loaded
modules are guaranteed to have all 4KiB chunks of memory they cover for
themselves exclusively.
* `path` - The path of the file within the volume, with a leading slash.
* `string` - A string associated with the file.
* `media_type` - Type of media file resides on.
* `tftp_ip` - If non-0, this is the IP of the TFTP server the file was loaded
from.
* `tftp_port` - Likewise, but port.
* `partition_index` - 1-based partition index of the volume from which the
file was loaded. If 0, it means invalid or unpartitioned.
* `mbr_disk_id` - If non-0, this is the ID of the disk the file was loaded
from as reported in its MBR.
* `gpt_disk_uuid` - If non-0, this is the UUID of the disk the file was
loaded from as reported in its GPT.
* `gpt_part_uuid` - If non-0, this is the UUID of the partition the file
was loaded from as reported in the GPT.
* `part_uuid` - If non-0, this is the UUID of the filesystem of the partition
the file was loaded from.