File: grub-dev.info, Node: Top, Next: Getting the source code, Up: (dir)
GNU GRUB developer manual
*************************
This is the developer documentation of GNU GRUB, the GRand Unified
Bootloader, a flexible and powerful boot loader program for a wide range
of architectures.
This edition documents version 2.03.
This developer manual is for GNU GRUB (version 2.03, 17 December
2024).
Copyright (C) 1999,2000,2001,2002,2004,2005,2006,2008,2009,2010,2011
Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.2 or any later version published by the Free Software
Foundation; with no Invariant Sections.
* Menu:
* Getting the source code::
* Coding style::
* Finding your way around::
* Contributing Changes::
* Porting::
* Error Handling::
* Stack and heap size::
* BIOS port memory map::
* Video Subsystem::
* PFF2 Font File Format::
* Graphical Menu Software Design::
* Lockdown framework::
* Copying This Manual:: Copying This Manual
* Index::
File: grub-dev.info, Node: Getting the source code, Next: Coding style, Prev: Top, Up: Top
1 Getting the source code
*************************
GRUB is maintained using the <GIT revision control system>. To fetch:
git clone git://git.sv.gnu.org/grub.git
Web access is available under
http://git.savannah.gnu.org/cgit/grub.git/
The branches available are:
'master'
Main development branch.
'grub-legacy'
GRUB 0.97 codebase. Kept for reference and legal reasons
'multiboot'
Multiboot specfication
'multiboot2'
Multiboot2 specfication
'developer branches'
Prefixed with developer name. Every developer of a team manages
his own branches. Developer branches do not need changelog
entries.
Once you have used 'git clone' to fetch an initial copy of a branch,
you can use 'git pull' to keep it up to date. If you have modified your
local version, you may need to resolve conflicts when pulling.
File: grub-dev.info, Node: Coding style, Next: Finding your way around, Prev: Getting the source code, Up: Top
2 Coding style
**************
Basically we follow the GNU Coding Standards
(http://www.gnu.org/prep/standards_toc.html). We define additional
conventions for GRUB here.
* Menu:
* Naming Conventions::
* Functions::
* Variables::
* Types::
* Macros::
* Comments::
* Multi-Line Comments::
File: grub-dev.info, Node: Naming Conventions, Next: Functions, Up: Coding style
2.1 Naming Conventions
======================
All global symbols (i.e. functions, variables, types, and macros) must
have the prefix grub_ or GRUB_. The all capital form is used only by
macros.
File: grub-dev.info, Node: Functions, Next: Variables, Prev: Naming Conventions, Up: Coding style
2.2 Functions
=============
If a function is global, its name must be prefixed with grub_ and must
consist of only small letters. If the function belongs to a specific
function module, the name must also be prefixed with the module name.
For example, if a function is for file systems, its name is prefixed
with grub_fs_. If a function is for FAT file system but not for all
file systems, its name is prefixed with grub_fs_fat_. The hierarchy is
noted this way.
After a prefix, a function name must start with a verb (such as get
or is). It must not be a noun. Some kind of abbreviation is permitted,
as long as it wouldn't make code less readable (e.g. init).
If a function is local, its name may not start with any prefix. It
must start with a verb.
File: grub-dev.info, Node: Variables, Next: Types, Prev: Functions, Up: Coding style
2.3 Variables
=============
The rule is mostly the same as functions, as noted above. If a variable
is global, its name must be prefixed with grub_ and must consist of only
small letters. If the variable belongs to a specific function module,
the name must also be prefixed with the module name. For example, if a
function is for dynamic loading, its name is prefixed with grub_dl_. If
a variable is for ELF but not for all dynamic loading systems, its name
is prefixed with grub_dl_elf_.
After a prefix, a variable name must start with a noun or an
adjective (such as name or long) and it should end with a noun. Some
kind of abbreviation is permitted, as long as it wouldn't make code less
readable (e.g. i18n).
If a variable is global in the scope of a single file (i.e. it is
declared with static), its name may not start with any prefix. It must
start with a noun or an adjective.
If a variable is local, you may choose any shorter name, as long as
it wouldn't make code less readable (e.g. i).
File: grub-dev.info, Node: Types, Next: Macros, Prev: Variables, Up: Coding style
2.4 Types
=========
The name of a type must be prefixed with grub_ and must consist of only
small letters. If the type belongs to a specific function module, the
name must also be prefixed with the module name. For example, if a type
is for OS loaders, its name is prefixed with grub_loader_. If a type is
for Multiboot but not for all OS loaders, its name is prefixed with
grub_loader_linux_.
The name must be suffixed with _t, to emphasize the fact that it is a
type but not a variable or a function.
File: grub-dev.info, Node: Macros, Next: Comments, Prev: Types, Up: Coding style
2.5 Macros
==========
If a macro is global, its name must be prefixed with GRUB_ and must
consist of only large letters. Other rules are the same as functions or
variables, depending on whether a macro is used like a function or a
variable.
File: grub-dev.info, Node: Comments, Next: Multi-Line Comments, Prev: Macros, Up: Coding style
2.6 Comments
============
All comments shall be C-style comments, of the form '/* ... */'.
Comments shall be placed only on a line by themselves. They shall
not be placed together with code, variable declarations, or other
non-comment entities. A comment should be placed immediately preceding
the entity it describes.
Acceptable:
/* The page # that is the front buffer. */
int displayed_page;
/* The page # that is the back buffer. */
int render_page;
Unacceptable:
int displayed_page; /* The page # that is the front buffer. */
int render_page; /* The page # that is the back buffer. */
File: grub-dev.info, Node: Multi-Line Comments, Prev: Comments, Up: Coding style
2.7 Multi-Line Comments
=======================
Comments spanning multiple lines shall be formatted with all lines after
the first aligned with the first line.
Asterisk characters should not be repeated a the start of each
subsequent line.
Acceptable:
/* This is a comment
which spans multiple lines.
It is long. */
Unacceptable:
/*
* This is a comment
* which spans multiple lines.
* It is long. */
The opening '/*' and closing '*/' should be placed together on a line
with text.
File: grub-dev.info, Node: Finding your way around, Next: Contributing Changes, Prev: Coding style, Up: Top
3 Finding your way around
*************************
Here is a brief map of the GRUB code base.
GRUB uses Autoconf and Automake, with most of the Automake input
generated by a Python script. The top-level build rules are in
'configure.ac', 'grub-core/Makefile.core.def', and 'Makefile.util.def'.
Each block in a '*.def' file represents a build target, and specifies
the source files used to build it on various platforms. The '*.def'
files are processed into Automake input by 'gentpl.py' (which you only
need to look at if you are extending the build system). If you are
adding a new module which follows an existing pattern, such as a new
command or a new filesystem implementation, it is usually easiest to
grep 'grub-core/Makefile.core.def' and 'Makefile.util.def' for an
existing example of that pattern to find out where it should be added.
In general, code that may be run at boot time is in a subdirectory of
'grub-core', while code that is only run from within a full operating
system is in a subdirectory of the top level.
Low-level boot code, such as the MBR implementation on PC BIOS
systems, is in the 'grub-core/boot/' directory.
The GRUB kernel is in 'grub-core/kern/'. This contains core
facilities such as the device, disk, and file frameworks, environment
variable handling, list processing, and so on. The kernel should
contain enough to get up to a rescue prompt. Header files for kernel
facilities, among others, are in 'include/'.
Terminal implementations are in 'grub-core/term/'.
Disk access code is spread across 'grub-core/disk/' (for accessing
the disk devices themselves), 'grub-core/partmap/' (for interpreting
partition table data), and 'grub-core/fs/' (for accessing filesystems).
Note that, with the odd specialised exception, GRUB only contains code
to _read_ from filesystems and tries to avoid containing any code to
_write_ to filesystems; this lets us confidently assure users that GRUB
cannot be responsible for filesystem corruption.
PCI and USB bus handling is in 'grub-core/bus/'.
Video handling code is in 'grub-core/video/'. The graphical menu
system uses this heavily, but is in a separate directory,
'grub-core/gfxmenu/'.
Most commands are implemented by files in 'grub-core/commands/', with
the following exceptions:
* A few core commands live in 'grub-core/kern/corecmd.c'.
* Commands related to normal mode live under 'grub-core/normal/'.
* Commands that load and boot kernels live under 'grub-core/loader/'.
* The 'loopback' command is really a disk device, and so lives in
'grub-core/disk/loopback.c'.
* The 'gettext' command lives under 'grub-core/gettext/'.
* The 'loadfont' and 'lsfonts' commands live under 'grub-core/font/'.
* The 'serial', 'terminfo', and 'background_image' commands live
under 'grub-core/term/'.
* The 'efiemu_*' commands live under 'grub-core/efiemu/'.
* OS-dependent code should be under 'grub-core/osdep/'
* Utility programs meant to be run from a full operating system
(except OS-dependent code mentioned previously) are in 'util/'.
There are a few other special-purpose exceptions; grep for them if
they matter to you.
File: grub-dev.info, Node: Contributing Changes, Next: Porting, Prev: Finding your way around, Up: Top
4 Contributing changes
**********************
Contributing changes to GRUB 2 is welcomed activity. However we have a
bit of control what kind of changes will be accepted to GRUB 2.
Therefore it is important to discuss your changes on grub-devel mailing
list (see MailingLists). On this page there are some basic details on
the development process and activities.
First of all you should come up with the idea yourself what you want
to contribute. If you do not have that beforehand you are advised to
study this manual and try GRUB 2 out to see what you think is missing
from there.
Here are additional pointers:
* <https://savannah.gnu.org/task/?group=grub GRUB's Task Tracker>
* <https://savannah.gnu.org/bugs/?group=grub GRUB's Bug Tracker>
If you intended to make changes to GRUB Legacy (<=0.97) those are not
accepted anymore.
* Menu:
* Getting started::
* Typical Developer Experience::
* When you are approved for write access to project's files::
File: grub-dev.info, Node: Getting started, Next: Typical Developer Experience, Up: Contributing Changes
4.1 Getting started
===================
* Always use latest GRUB 2 source code. So get that first.
For developers it is recommended always to use the newest
development version of GRUB 2. If development takes a long period
of time, please remember to keep in sync with newest developments
regularly so it is much easier to integrate your change in the
future. GRUB 2 is being developed in a GIT repository.
Please check Savannah's GRUB project page for details how to get
newest git: GRUB 2 git Repository
(https://savannah.gnu.org/git/?group=grub)
* Compile it and try it out.
It is always good idea to first see that things work somehow and
after that to start to implement new features or develop fixes to
bugs.
* Study the code.
There are sometimes odd ways to do things in GRUB 2 code base.
This is mainly related to limited environment where GRUB 2 is being
executed. You usually do not need to understand it all so it is
better to only try to look at places that relates to your work.
Please do not hesitate to ask for help if there is something that
you do not understand.
* Develop a new feature.
Now that you know what to do and how it should work in GRUB 2 code
base, please be free to develop it. If you have not so far
announced your idea on grub-devel mailing list, please do it now.
This is to make sure you are not wasting your time working on the
solution that will not be integrated to GRUB 2 code base.
You might want to study our coding style before starting
development so you do not need to change much of the code when your
patch is being reviewed. (see *note Coding style::)
For every accepted patch there has to exist a ChangeLog entry. Our
ChangeLog consist of changes within source code and are not
describing about what the change logically does. Please see
examples from previous entries.
Also remember that GRUB 2 is licensed under GPLv3 license and that
usually means that you are not allowed to copy pieces of code from
other projects. Even if the source project's license would be
compatible with GPLv3, please discuss it beforehand on grub-devel
mailing list.
* Test your change.
Test that your change works properly. Try it out a couple of
times, preferably on different systems, and try to find problems
with it.
* Publish your change.
When you are happy with your change, first make sure it is
compilable with latest development version of GRUB 2. After that
please send a patch to grub-devel for review. Please describe in
your email why you made the change, what it changes and so on.
Please be prepared to receive even discouraging comments about your
patch. There is usually at least something that needs to be
improved in every patch.
Please use unified diff to make your patch (good match of arguments
for diff is '-pruN').
* Respond to received feedback.
If you are asked to modify your patch, please do that and resubmit
it for review. If your change is large you are required to submit
a copyright agreement to FSF. Please keep in mind that if you are
asked to submit for copyright agreement, process can take some time
and is mandatory in order to get your changes integrated.
If you are not on grub-devel to respond to questions, most likely
your patch will not be accepted. Also if problems arise from your
changes later on, it would be preferable that you also fix the
problem. So stay around for a while.
* Your patch is accepted.
Good job! Your patch will now be integrated into GRUB 2 mainline,
and if it didn't break anything it will be publicly available in
the next release.
Now you are welcome to do further improvements :)
File: grub-dev.info, Node: Typical Developer Experience, Next: When you are approved for write access to project's files, Prev: Getting started, Up: Contributing Changes
4.2 Typical Developer Experience
================================
The typical experience for a developer in this project is the following:
1. You find yourself wanting to do something (e.g. fixing a bug).
2. You show some result in the mailing list or the IRC.
3. You are getting to be known to other developers.
4. You accumulate significant amount of contribution, so copyright
assignment is processed.
5. You are free to check in your changes on your own, legally
speaking.
At this point, it is rather annoying that you ought to ask somebody
else every change to be checked in. For efficiency, it is far better,
if you can commit it yourself. Therefore, our policy is to give you the
write permission to our official repository, once you have shown your
skill and will, and the FSF clerks have dealt with your copyright
assignment.
File: grub-dev.info, Node: When you are approved for write access to project's files, Prev: Typical Developer Experience, Up: Contributing Changes
4.3 When you are approved for write access to project's files
=============================================================
As you might know, GRUB is hosted on
<https://savannah.gnu.org/projects/grub Savannah>, thus the membership
is managed by Savannah. This means that, if you want to be a member of
this project:
1. You need to create your own account on Savannah.
2. You can submit "Request for Inclusion" from "My Groups" on
Savannah.
Then, one of the admins can approve your request, and you will be a
member. If you don't want to use the Savannah interface to submit a
request, you can simply notify the admins by email or something else,
alternatively. But you still need to create an account beforehand.
NOTE: we sometimes receive a "Request for Inclusion" from an unknown
person. In this case, the request would be just discarded, since it is
too dangerous to allow a stranger to be a member, which automatically
gives him a commit right to the repository, both for a legal reason and
for a technical reason.
If your intention is to just get started, please do not submit a
inclusion request. Instead, please subscribe to the mailing list, and
communicate first (e.g. sending a patch, asking a question, commenting
on another message...).
File: grub-dev.info, Node: Porting, Next: Error Handling, Prev: Contributing Changes, Up: Top
5 Porting
*********
GRUB2 is designed to be easily portable accross platforms. But because
of the nature of bootloader every new port must be done separately.
Here is how I did MIPS (loongson and ARC) and Xen ports. Note than this
is more of suggestions, not absolute truth.
First of all grab any architecture specifications you can find in
public (please avoid NDA).
First stage is "Hello world". I've done it outside of GRUB for
simplicity. Your task is to have a small program which is loadable as
bootloader and clearly shows its presence to you. If you have easily
accessible console you can just print a message. If you have a mapped
framebuffer you know address of, you can draw a square. If you have a
debug facility, just hanging without crashing might be enough. For the
first stage you can choose to load the bootloader across the network
since format for network image is often easier than for local boot and
it skips the need of small intermediary stages and nvram handling.
Additionally you can often have a good idea of the needed format by
running "file" on any netbootable executable for given platform.
This program should probably have 2 parts: an assembler and C one.
Assembler one handles BSS cleaning and other needed setup (on some
platforms you may need to switch modes or copy the executable to its
definitive position). So your code may look like (x86 assembly for
illustration purposes)
.globl _start
_start:
movl $_bss_start, %edi
movl $_end, %ecx
subl %edi, %ecx
xorl %eax, %eax
cld
rep
stosb
call main
static const char msg[] = "Hello, world";
void
putchar (int c)
{
...
}
void
main (void)
{
const char *ptr = msg;
while (*ptr)
putchar (*ptr++);
while (1);
}
Sometimes you need a third file: assembly stubs for
ABI-compatibility.
Once this file is functional it's time to move it into GRUB2. The
startup assembly file goes to grub-core/kern/$cpu/$platform/startup.S.
You should also include grub/symbol.h and replace call to entry point
with call to EXT_C(grub_main). The C file goes to
grub-core/kern/$cpu/$platform/init.c and its entry point is renamed to
void grub_machine_init (void). Keep final infinite loop for now. Stubs
file if any goes to grub-core/kern/$cpu/$platform/callwrap.S. Sometimes
either $cpu or $platform is dropped if file is used on several cpus
respectivelyplatforms. Check those locations if they already have what
you're looking for.
Then modify in configure.ac the following parts:
CPU names:
case "$target_cpu" in
i[[3456]]86) target_cpu=i386 ;;
amd64) target_cpu=x86_64 ;;
sparc) target_cpu=sparc64 ;;
s390x) target_cpu=s390 ;;
...
esac
Sometimes CPU have additional architecture names which don't
influence booting. You might want to have some canonical name to avoid
having bunch of identical platforms with different names.
NOTE: it doesn't influence compile optimisations which depend solely
on chosen compiler and compile options.
if test "x$with_platform" = x; then
case "$target_cpu"-"$target_vendor" in
i386-apple) platform=efi ;;
i386-*) platform=pc ;;
x86_64-apple) platform=efi ;;
x86_64-*) platform=pc ;;
powerpc-*) platform=ieee1275 ;;
...
esac
else
...
fi
This part deals with guessing the platform from CPU and vendor.
Sometimes you need to use 32-bit mode for booting even if OS runs in
64-bit one. If so add your platform to:
case "$target_cpu"-"$platform" in
x86_64-efi) ;;
x86_64-emu) ;;
x86_64-*) target_cpu=i386 ;;
powerpc64-ieee1275) target_cpu=powerpc ;;
esac
Add your platform to the list of supported ones:
case "$target_cpu"-"$platform" in
i386-efi) ;;
x86_64-efi) ;;
i386-pc) ;;
i386-multiboot) ;;
i386-coreboot) ;;
...
esac
If explicit -m32 or -m64 is needed add it to:
case "$target_cpu" in
i386 | powerpc) target_m32=1 ;;
x86_64 | sparc64) target_m64=1 ;;
esac
Finally you need to add a conditional to the following block:
AM_CONDITIONAL([COND_mips_arc], [test x$target_cpu = xmips -a x$platform = xarc])
AM_CONDITIONAL([COND_sparc64_ieee1275], [test x$target_cpu = xsparc64 -a x$platform = xieee1275])
AM_CONDITIONAL([COND_powerpc_ieee1275], [test x$target_cpu = xpowerpc -a x$platform = xieee1275])
Next stop is gentpl.py. You need to add your platform to the list of
supported ones (sorry that this list is duplicated):
GRUB_PLATFORMS = [ "emu", "i386_pc", "i386_efi", "i386_qemu", "i386_coreboot",
"i386_multiboot", "i386_ieee1275", "x86_64_efi",
"mips_loongson", "sparc64_ieee1275",
"powerpc_ieee1275", "mips_arc", "ia64_efi",
"mips_qemu_mips", "s390_mainframe" ]
You may also want already to add new platform to one or several of
available groups. In particular we always have a group for each CPU
even when only one platform for given CPU is available.
Then comes grub-core/Makefile.core.def. In the block "kernel" you'll
need to define ldflags for your platform ($cpu_$platform_ldflags). You
also need to declare startup asm file ($cpu_$platform_startup) as well
as any other files (e.g. init.c and callwrap.S) (e.g. $cpu_$platform =
kern/$cpu/$platform/init.c). At this stage you will also need to add
dummy dl.c and cache.S with functions grub_err_t
grub_arch_dl_check_header (void *ehdr), grub_err_t
grub_arch_dl_relocate_symbols (grub_dl_t mod, void *ehdr) (dl.c),
grub_uint32_t grub_arch_dl_min_alignment (void), and void
grub_arch_sync_caches (void *address, grub_size_t len) (cache.S). They
won't be used for now.
You will need to create directory include/$cpu/$platform and a file
include/$cpu/types.h. The later folowing this template:
#ifndef GRUB_TYPES_CPU_HEADER
#define GRUB_TYPES_CPU_HEADER 1
/* The size of void *. */
#define GRUB_TARGET_SIZEOF_VOID_P 4
/* The size of long. */
#define GRUB_TARGET_SIZEOF_LONG 4
/* mycpu is big-endian. */
#define GRUB_TARGET_WORDS_BIGENDIAN 1
/* Alternatively: mycpu is little-endian. */
#undef GRUB_TARGET_WORDS_BIGENDIAN
#endif /* ! GRUB_TYPES_CPU_HEADER */
You will also need to add a dummy file to datetime and setjmp modules
to avoid any of it having no files. It can be just completely empty at
this stage.
You'll need to make grub-mkimage.c (util/grub_mkimage.c) aware of the
needed format. For most commonly used formats like ELF, PE, aout or raw
the support is already present and you'll need to make it follow the
existant code paths for your platform adding adjustments if necessary.
When done compile:
./autogen.sh
./configure --target=$cpu --with-platform=$platform TARGET_CC=.. OBJCOPY=... STRIP=...
make > /dev/null
And create image
./grub-mkimage -d grub-core -O $format_id -o test.img
And it's time to test your test.img.
If it works next stage is to have heap, console and timer.
To have the heap working you need to determine which regions are
suitable for heap usage, allocate them from firmware and map (if
applicable). Then call grub_mm_init_region (vois *start, grub_size_t s)
for every of this region. As a shortcut for early port you can allocate
right after _end or have a big static array for heap. If you do you'll
probably need to come back to this later. As for output console you
should distinguish between an array of text, terminfo or graphics-based
console. Many of real-world examples don't fit perfectly into any of
these categories but one of the models is easier to be used as base. In
second and third case you should add your platform to terminfokernel
respectively videoinkernel group. A good example of array of text is
i386-pc (kern/i386/pc/init.c and term/i386/pc/console.c). Of terminfo
is ieee1275 (kern/ieee1275/init.c and term/ieee1275/console.c). Of
video is loongson (kern/mips/loongson/init.c). Note that terminfo has
to be inited in 2 stages: one before (to get at least rudimentary
console as early as possible) and another after the heap (to get
full-featured console). For the input there are string of keys,
terminfo and direct hardware. For string of keys look at i386-pc (same
files), for termino ieee1275 (same files) and for hardware loongson
(kern/mips/loongson/init.c and term/at_keyboard.c).
For the timer you'll need to call grub_install_get_time_ms (...)
with as sole argument a function returning a grub_uint64_t of a number
of milliseconds elapsed since arbitrary point in the past.
Once these steps accomplished you can remove the inifinite loop and
you should be able to get to the minimal console. Next step is to have
module loading working. For this you'll need to fill kern/$cpu/dl.c and
kern/$cpu/cache.S with real handling of relocations and respectively the
real sync of I and D caches. Also you'll need to decide where in the
image to store the modules. Usual way is to have it concatenated at the
end. In this case you'll need to modify startup.S to copy modules out
of bss to let's say ALIGN_UP (_end, 8) before cleaning out bss. You'll
probably find useful to add total_module_size field to startup.S. In
init.c you need to set grub_modbase to the address where modules can be
found. You may need grub_modules_get_end () to avoid declaring the
space occupied by modules as usable for heap. You can test modules
with:
./grub-mkimage -d grub-core -O $format_id -o test.img hello
and then running "hello" in the shell.
Once this works, you should think of implementing disk access. Look
around disk/ for examples.
Then, very importantly, you probably need to implement the actual
loader (examples available in loader/)
Last step to have minimally usable port is to add support to
grub-install to put GRUB in a place where firmware or platform will pick
it up.
Next steps are: filling datetime.c, setjmp.S, network (net/drivers),
video (video/), halt (lib/), reboot (lib/).
Please add your platform to Platform limitations and Supported
kernels chapter in user documentation and mention any steps you skipped
which result in reduced features or performance. Here is the quick
checklist of features. Some of them are less important than others and
skipping them is completely ok, just needs to be mentioned in user
documentation.
Checklist:
* Is heap big enough?
* Which charset is supported by console?
* Does platform have disk driver?
* Do you have network card support?
* Are you able to retrieve datetime (with date)?
* Are you able to set datetime (with date)?
* Is serial supported?
* Do you have direct disk support?
* Do you have direct keyboard support?
* Do you have USB support?
* Do you support loading through network?
* Do you support loading from disk?
* Do you support chainloading?
* Do you support network chainloading?
* Does cpuid command supports checking all CPU features that the user
might want conditionalise on (64-bit mode, hypervisor,...)
* Do you support hints? How reliable are they?
* Does platform have ACPI? If so do "acpi" and "lsacpi" modules work?
* Do any of platform-specific operations mentioned in the relevant
section of user manual makes sense on your platform?
* Does your platform support PCI? If so is there an appropriate
driver for GRUB?
* Do you support badram?
File: grub-dev.info, Node: Error Handling, Next: Stack and heap size, Prev: Porting, Up: Top
6 Error Handling
****************
Error handling in GRUB 2 is based on exception handling model. As C
language doesn't directly support exceptions, exception handling
behavior is emulated in software.
When exception is raised, function must return to calling function.
If calling function does not provide handling of the exception it must
return back to its calling function and so on, until exception is
handled. If exception is not handled before prompt is displayed, error
message will be shown to user.
Exception information is stored on 'grub_errno' global variable. If
'grub_errno' variable contains value 'GRUB_ERR_NONE', there is no active
exception and application can continue normal processing. When
'grub_errno' has other value, it is required that application code
either handles this error or returns instantly to caller. If function
is with return type 'grub_err_t' is about to return 'GRUB_ERR_NONE', it
should not set 'grub_errno' to that value. Only set 'grub_errno' in
cases where there is error situation.
Simple exception forwarder.
grub_err_t
forwarding_example (void)
{
/* Call function that might cause exception. */
foobar ();
/* No special exception handler, just forward possible exceptions. */
if (grub_errno != GRUB_ERR_NONE)
{
return grub_errno;
}
/* All is OK, do more processing. */
/* Return OK signal, to caller. */
return GRUB_ERR_NONE;
}
Error reporting has two components, the actual error code (of type
'grub_err_t') and textual message that will be displayed to user. List
of valid error codes is listed in header file 'include/grub/err.h'.
Textual error message can contain any textual data. At time of writing,
error message can contain up to 256 characters (including terminating
NUL). To ease error reporting there is a helper function 'grub_error'
that allows easier formatting of error messages and should be used
instead of writing directly to global variables.
Example of error reporting.
grub_err_t
failing_example ()
{
return grub_error (GRUB_ERR_FILE_NOT_FOUND,
"Failed to read %s, tried %d times.",
"test.txt",
10);
}
If there is a special reason that error code does not need to be
taken account, 'grub_errno' can be zeroed back to 'GRUB_ERR_NONE'. In
cases like this all previous error codes should have been handled
correctly. This makes sure that there are no unhandled exceptions.
Example of zeroing 'grub_errno'.
grub_err_t
probe_example ()
{
/* Try to probe device type 1. */
probe_for_device ();
if (grub_errno == GRUB_ERR_NONE)
{
/* Device type 1 was found on system. */
register_device ();
return GRUB_ERR_NONE;
}
/* Zero out error code. */
grub_errno = GRUB_ERR_NONE;
/* No device type 1 found, try to probe device type 2. */
probe_for_device2 ();
if (grub_errno == GRUB_ERR_NONE)
{
/* Device type 2 was found on system. */
register_device2 ();
return GRUB_ERR_NONE;
}
/* Zero out error code. */
grub_errno = GRUB_ERR_NONE;
/* Return custom error message. */
return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "No device type 1 or 2 found.");
}
Some times there is a need to continue processing even if there is a
error state in application. In situations like this, there is a needed
to save old error state and then call other functions that might fail.
To aid in this, there is a error stack implemented. Error state can be
pushed to error stack by calling function 'grub_error_push ()'. When
processing has been completed, 'grub_error_pop ()' can be used to pop
error state from stack. Error stack contains predefined amount of error
stack items. Error stack is protected for overflow and marks these
situations so overflow error does not get unseen. If there is no space
available to store error message, it is simply discarded and overflow
will be marked as happened. When overflow happens, it most likely will
corrupt error stack consistency as for pushed error there is no matching
pop, but overflow message will be shown to inform user about the
situation. Overflow message will be shown at time when prompt is about
to be drawn.
Example usage of error stack.
/* Save possible old error message. */
grub_error_push ();
/* Do your stuff here. */
call_possibly_failing_function ();
if (grub_errno != GRUB_ERR_NONE)
{
/* Inform rest of the code that there is error (grub_errno
is set). There is no pop here as we want both error states
to be displayed. */
return;
}
/* Restore old error state by popping previous item from stack. */
grub_error_pop ();
File: grub-dev.info, Node: Stack and heap size, Next: BIOS port memory map, Prev: Error Handling, Up: Top
7 Stack and heap size
*********************
On emu stack and heap are just normal host OS stack and heap. Stack is
typically 8 MiB although it's OS-dependent.
On i386-pc, i386-coreboot, i386-qemu and i386-multiboot the stack is
60KiB. All available space between 1MiB and 4GiB marks is part of heap.
On *-xen stack is 4MiB. If compiled for x86-64 with GCC 4.4 or later
adressable space is unlimited. When compiled for x86-64 with older GCC
version adressable space is limited to 2GiB. When compiling for i386
adressable space is limited to 4GiB. All adressable pages except the
ones for stack, GRUB binary, special pages and page table are in the
heap.
On *-efi GRUB uses same stack as EFI. If compiled for x86-64 with GCC
4.4 or later adressable space is unlimited. When compiled for x86-64
with older GCC version adressable space is limited to 2GiB. For all
other platforms adressable space is limited to 4GiB. GRUB allocates
pages from EFI for its heap, at most 1.6 GiB.
On i386-ieee1275 and powerpc-ieee1275 GRUB uses same stack as
IEEE1275.
On i386-ieee1275, GRUB allocates at most 32MiB for its heap. On
powerpc-ieee1275, GRUB allocates up to 1GiB.
On sparc64-ieee1275 stack is 256KiB and heap is 2MiB.
On mips(el)-qemu_mips and mipsel-loongson stack is 2MiB (everything
below GRUB image) and everything above GRUB image (from 2MiB + kernel
size) until 256MiB is part of heap.
On mips-arc stack is 2MiB (everything below GRUB image) and
everything above GRUB image(from 2MiB + kernel size) until 128MiB is
part of heap.
On mipsel-arc stack is 2MiB (everything below GRUB image which is not
part of ARC) and everything above GRUB image (from 7MiB + kernel size)
until 256MiB is part of heap.
On arm-uboot stack is 256KiB and heap is 2MiB.
In short:
Platform Stack Heap
--------------------------------------------------------------------
emu 8 MiB ?
i386-pc 60 KiB < 4 GiB
i386-coreboot60 KiB < 4 GiB
i386-multiboot60 KiB < 4 GiB
i386-qemu 60 KiB < 4 GiB
*-efi ? < 1.6 GiB
i386-ieee1275? < 32 MiB
powerpc-ieee1275? < 1 GiB
sparc64-ieee1275256KiB 2 MiB
arm-uboot 256KiB 2 MiB
mips(el)-qemu_mips2MiB 253 MiB
mipsel-loongson2MiB 253 MiB
mips-arc 2MiB 125 MiB
mipsel-arc 2MiB 248 MiB
x86_64-xen 4MiB unlimited
(GCC >=
4.4)
x86_64-xen 4MiB < 2GiB
(GCC <
4.4)
i386-xen 4MiB < 4GiB
File: grub-dev.info, Node: BIOS port memory map, Next: Video Subsystem, Prev: Stack and heap size, Up: Top
8 BIOS port memory map
**********************
Start End Usage
--------------------------------------------------------------------
0 0x1000 - 1 BIOS and real mode interrupts
0x07BE 0x07FF Partition table passed to another
boot loader
? 0x2000 - 1 Real mode stack
0x7C00 0x7D00 - 1 Boot sector
0x8000 ? GRUB kernel
0x68000 0x71000 - 1 Disk buffer
? 0x80000 - 1 Protected mode stack
? 0xA0000 - 1 Extended BIOS Data Area
0xA0000 0xC0000 - 1 Video RAM
0xC0000 0x100000 - 1 BIOS
0x100000 ? Heap and module code
File: grub-dev.info, Node: Video Subsystem, Next: PFF2 Font File Format, Prev: BIOS port memory map, Up: Top
9 Video Subsystem
*****************
This document contains specification for Video Subsystem for GRUB2.
Currently only the usage interface is described in this document.
Internal structure of how video drivers are registering and how video
driver manager works are not included here.
* Menu:
* Video API::
* Example usage of Video API::
* Bitmap API::
File: grub-dev.info, Node: Video API, Next: Example usage of Video API, Up: Video Subsystem
9.1 Video API
=============
9.1.1 grub_video_setup
----------------------
* Prototype:
grub_err_t
grub_video_setup (unsigned int width, unsigned int height, unsigned int mode_type);
* Description:
Driver will use information provided to it to select best possible
video mode and switch to it. Supported values for 'mode_type' are
'GRUB_VIDEO_MODE_TYPE_INDEX_COLOR' for index color modes,
'GRUB_VIDEO_MODE_TYPE_RGB' for direct RGB color modes and
'GRUB_VIDEO_MODE_TYPE_DOUBLE_BUFFERED' for double buffering. When
requesting RGB mode, highest bits per pixel mode will be selected.
When requesting Index color mode, mode with highest number of
colors will be selected. If all parameters are specified as zero,
video adapter will try to figure out best possible mode and
initialize it, platform specific differences are allowed here. If
there is no mode matching request, error X will be returned. If
there are no problems, function returns 'GRUB_ERR_NONE'.
This function also performs following task upon succesful mode
switch. Active rendering target is changed to screen and viewport
is maximized to allow whole screen to be used when performing
graphics operations. In RGB modes, emulated palette gets 16
entries containing default values for VGA palette, other colors are
defined as black. When switching to Indexed Color mode, driver may
set default VGA palette to screen if the video card allows the
operation.
9.1.2 grub_video_restore
------------------------
* Prototype:
grub_err_t
grub_video_restore (void);
* Description:
Video subsystem will deinitialize activated video driver to restore
old state of video device. This can be used to switch back to text
mode.
9.1.3 grub_video_get_info
-------------------------
* Prototype:
grub_err_t
grub_video_get_info (struct grub_video_mode_info *mode_info);
struct grub_video_mode_info
{
/* Width of the screen. */
unsigned int width;
/* Height of the screen. */
unsigned int height;
/* Mode type bitmask. Contains information like is it Index color or
RGB mode. */
unsigned int mode_type;
/* Bits per pixel. */
unsigned int bpp;
/* Bytes per pixel. */
unsigned int bytes_per_pixel;
/* Pitch of one scanline. How many bytes there are for scanline. */
unsigned int pitch;
/* In index color mode, number of colors. In RGB mode this is 256. */
unsigned int number_of_colors;
/* Optimization hint how binary data is coded. */
enum grub_video_blit_format blit_format;
/* How many bits are reserved for red color. */
unsigned int red_mask_size;
/* What is location of red color bits. In Index Color mode, this is 0. */
unsigned int red_field_pos;
/* How many bits are reserved for green color. */
unsigned int green_mask_size;
/* What is location of green color bits. In Index Color mode, this is 0. */
unsigned int green_field_pos;
/* How many bits are reserved for blue color. */
unsigned int blue_mask_size;
/* What is location of blue color bits. In Index Color mode, this is 0. */
unsigned int blue_field_pos;
/* How many bits are reserved in color. */
unsigned int reserved_mask_size;
/* What is location of reserved color bits. In Index Color mode,
this is 0. */
unsigned int reserved_field_pos;
};
* Description:
Software developer can use this function to query properties of
active rendering taget. Information provided here can be used by
other parts of GRUB, like image loaders to convert loaded images to
correct screen format to allow more optimized blitters to be used.
If there there is no configured video driver with active screen,
error 'GRUB_ERR_BAD_DEVICE' is returned, otherwise 'mode_info' is
filled with valid information and 'GRUB_ERR_NONE' is returned.
9.1.4 grub_video_get_blit_format
--------------------------------
* Prototype:
enum grub_video_blit_format
grub_video_get_blit_format (struct grub_video_mode_info *mode_info);
enum grub_video_blit_format
{
/* Follow exactly field & mask information. */
GRUB_VIDEO_BLIT_FORMAT_RGBA,
/* Make optimization assumption. */
GRUB_VIDEO_BLIT_FORMAT_R8G8B8A8,
/* Follow exactly field & mask information. */
GRUB_VIDEO_BLIT_FORMAT_RGB,
/* Make optimization assumption. */
GRUB_VIDEO_BLIT_FORMAT_R8G8B8,
/* When needed, decode color or just use value as is. */
GRUB_VIDEO_BLIT_FORMAT_INDEXCOLOR
};
* Description:
Used to query how data could be optimized to suit specified video
mode. Returns exact video format type, or a generic one if there
is no definition for the type. For generic formats, use
'grub_video_get_info' to query video color coding settings.
9.1.5 grub_video_set_palette
----------------------------
* Prototype:
grub_err_t
grub_video_set_palette (unsigned int start, unsigned int count, struct grub_video_palette_data *palette_data);
struct grub_video_palette_data
{
grub_uint8_t r; /* Red color value (0-255). */
grub_uint8_t g; /* Green color value (0-255). */
grub_uint8_t b; /* Blue color value (0-255). */
grub_uint8_t a; /* Reserved bits value (0-255). */
};
* Description:
Used to setup indexed color palettes. If mode is RGB mode, colors
will be set to emulated palette data. In Indexed Color modes,
palettes will be set to hardware. Color values will be converted
to suit requirements of the video mode. 'start' will tell what
hardware color index (or emulated color index) will be set to
according information in first indice of 'palette_data', after that
both hardware color index and 'palette_data' index will be
incremented until 'count' number of colors have been set.
9.1.6 grub_video_get_palette
----------------------------
* Prototype:
grub_err_t
grub_video_get_palette (unsigned int start, unsigned int count, struct grub_video_palette_data *palette_data);
struct grub_video_palette_data
{
grub_uint8_t r; /* Red color value (0-255). */
grub_uint8_t g; /* Green color value (0-255). */
grub_uint8_t b; /* Blue color value (0-255). */
grub_uint8_t a; /* Reserved bits value (0-255). */
};
* Description:
Used to query indexed color palettes. If mode is RGB mode, colors
will be copied from emulated palette data. In Indexed Color modes,
palettes will be read from hardware. Color values will be
converted to suit structure format. 'start' will tell what
hardware color index (or emulated color index) will be used as a
source for first indice of 'palette_data', after that both hardware
color index and 'palette_data' index will be incremented until
'count' number of colors have been read.
9.1.7 grub_video_set_area_status
--------------------------------
* Prototype:
grub_err_t
grub_video_set_area_status (grub_video_area_status_t area_status);
enum grub_video_area_status_t
{
GRUB_VIDEO_AREA_DISABLED,
GRUB_VIDEO_AREA_ENABLED
};
* Description:
Used to set area drawing mode for redrawing the specified region.
Draw commands are performed in the intersection of the viewport and
the region called area. Coordinates remain related to the
viewport. If draw commands try to draw over the area, they are
clipped. Set status to DISABLED if you need to draw everything.
Set status to ENABLED and region to the desired rectangle to redraw
everything inside the region leaving everything else intact.
Should be used for redrawing of active elements.
9.1.8 grub_video_get_area_status
--------------------------------
* Prototype:
grub_err_r
grub_video_get_area_status (grub_video_area_status_t *area_status);
* Description: Used to query the area status.
9.1.9 grub_video_set_viewport
-----------------------------
* Prototype:
grub_err_t
grub_video_set_viewport (unsigned int x, unsigned int y, unsigned int width, unsigned int height);
* Description:
Used to specify viewport where draw commands are performed. When
viewport is set, all draw commands coordinates relate to those
specified by 'x' and 'y'. If draw commands try to draw over
viewport, they are clipped. If developer requests larger than
possible viewport, width and height will be clamped to fit screen.
If 'x' and 'y' are out of bounds, all functions drawing to screen
will not be displayed. In order to maximize viewport, use
'grub_video_get_info' to query actual screen dimensions and provide
that information to this function.
9.1.10 grub_video_get_viewport
------------------------------
* Prototype:
grub_err_t
grub_video_get_viewport (unsigned int *x, unsigned int *y, unsigned int *width, unsigned int *height);
* Description:
Used to query current viewport dimensions. Software developer can
use this to choose best way to render contents of the viewport.
9.1.11 grub_video_set_region
----------------------------
* Prototype:
grub_err_t
grub_video_set_region (unsigned int x, unsigned int y, unsigned int width, unsigned int height);
* Description:
Used to specify the region of the screen which should be redrawn.
Use absolute values. When the region is set and area status is
ENABLE all draw commands will be performed inside the interseption
of region and viewport named area. If draw commands try to draw
over viewport, they are clipped. If developer requests larger than
possible region, width and height will be clamped to fit screen.
Should be used for redrawing of active elements.
9.1.12 grub_video_get_region
----------------------------
* Prototype:
grub_err_t
grub_video_get_region (unsigned int *x, unsigned int *y, unsigned int *width, unsigned int *height);
* Description:
Used to query current region dimensions.
9.1.13 grub_video_map_color
---------------------------
* Prototype:
grub_video_color_t
grub_video_map_color (grub_uint32_t color_name);
* Description:
Map color can be used to support color themes in GRUB. There will
be collection of color names that can be used to query actual
screen mapped color data. Examples could be
'GRUB_COLOR_CONSOLE_BACKGROUND', 'GRUB_COLOR_CONSOLE_TEXT'. The
actual color defines are not specified at this point.
9.1.14 grub_video_map_rgb
-------------------------
* Prototype:
grub_video_color_t
grub_video_map_rgb (grub_uint8_t red, grub_uint8_t green, grub_uint8_t blue);
* Description:
Map RGB values to compatible screen color data. Values are
expected to be in range 0-255 and in RGB modes they will be
converted to screen color data. In index color modes, index color
palette will be searched for specified color and then index is
returned.
9.1.15 grub_video_map_rgba
--------------------------
* Prototype:
grub_video_color_t
grub_video_map_rgba (grub_uint8_t red, grub_uint8_t green, grub_uint8_t blue, grub_uint8_t alpha);
* Description:
Map RGBA values to compatible screen color data. Values are
expected to be in range 0-255. In RGBA modes they will be
converted to screen color data. In index color modes, index color
palette will be searched for best matching color and its index is
returned.
9.1.16 grub_video_unmap_color
-----------------------------
* Prototype:
grub_err_t
grub_video_unmap_color (grub_video_color_t color, grub_uint8_t *red, grub_uint8_t *green, grub_uint8_t *blue, grub_uint8_t *alpha);
* Description:
Unmap color value from 'color' to color channels in 'red', 'green',
'blue' and 'alpha'. Values will be in range 0-255. Active
rendering target will be used for color domain. In case alpha
information is not available in rendering target, it is assumed to
be opaque (having value 255).
9.1.17 grub_video_fill_rect
---------------------------
* Prototype:
grub_err_t
grub_video_fill_rect (grub_video_color_t color, int x, int y, unsigned int width, unsigned int height);
* Description:
Fill specified area limited by given coordinates within specified
viewport. Negative coordinates are accepted in order to allow easy
moving of rectangle within viewport. If coordinates are negative,
area of the rectangle will be shrinken to follow size limits of the
viewport.
Software developer should use either 'grub_video_map_color',
'grub_video_map_rgb' or 'grub_video_map_rgba' to map requested
color to 'color' parameter.
9.1.18 grub_video_blit_glyph
----------------------------
* Prototype:
grub_err_t
grub_video_blit_glyph (struct grub_font_glyph *glyph, grub_video_color_t color, int x, int y);
struct grub_font_glyph {
/* TBD. */
};
* Description:
Used to blit glyph to viewport in specified coodinates. If glyph
is at edge of viewport, pixels outside of viewport will be clipped
out. Software developer should use either 'grub_video_map_rgb' or
'grub_video_map_rgba' to map requested color to 'color' parameter.
9.1.19 grub_video_blit_bitmap
-----------------------------
* Prototype:
grub_err_t
grub_video_blit_bitmap (struct grub_video_bitmap *bitmap, enum grub_video_blit_operators oper, int x, int y, int offset_x, int offset_y, unsigned int width, unsigned int height);
struct grub_video_bitmap
{
/* TBD. */
};
enum grub_video_blit_operators
{
GRUB_VIDEO_BLIT_REPLACE,
GRUB_VIDEO_BLIT_BLEND
};
* Description:
Used to blit bitmap to viewport in specified coordinates. If part
of bitmap is outside of viewport region, it will be clipped out.
Offsets affect bitmap position where data will be copied from.
Negative values for both viewport coordinates and bitmap offset
coordinates are allowed. If data is looked out of bounds of
bitmap, color value will be assumed to be transparent. If viewport
coordinates are negative, area of the blitted rectangle will be
shrinken to follow size limits of the viewport and bitmap.
Blitting operator 'oper' specifies should source pixel replace data
in screen or blend with pixel alpha value.
Software developer should use 'grub_video_bitmap_create' or
'grub_video_bitmap_load' to create or load bitmap data.
9.1.20 grub_video_blit_render_target
------------------------------------
* Prototype:
grub_err_t
grub_video_blit_render_target (struct grub_video_render_target *source, enum grub_video_blit_operators oper, int x, int y, int offset_x, int offset_y, unsigned int width, unsigned int height);
struct grub_video_render_target {
/* This is private data for video driver. Should not be accessed from elsewhere directly. */
};
enum grub_video_blit_operators
{
GRUB_VIDEO_BLIT_REPLACE,
GRUB_VIDEO_BLIT_BLEND
};
* Description:
Used to blit source render target to viewport in specified
coordinates. If part of source render target is outside of
viewport region, it will be clipped out. If blitting operator is
specified and source contains alpha values, resulting pixel color
components will be calculated using formula ((src_color *
src_alpha) + (dst_color * (255 - src_alpha)) / 255, if target
buffer has alpha, it will be set to src_alpha. Offsets affect
render target position where data will be copied from. If data is
looked out of bounds of render target, color value will be assumed
to be transparent. Blitting operator 'oper' specifies should
source pixel replace data in screen or blend with pixel alpha
value.
9.1.21 grub_video_scroll
------------------------
* Prototype:
grub_err_t
grub_video_scroll (grub_video_color_t color, int dx, int dy);
* Description:
Used to scroll viewport to specified direction. New areas are
filled with specified color. This function is used when screen is
scroller up in video terminal.
9.1.22 grub_video_swap_buffers
------------------------------
* Prototype:
grub_err_t
grub_video_swap_buffers (void);
* Description:
If double buffering is enabled, this swaps frontbuffer and
backbuffer, in order to show values drawn to back buffer. Video
driver is free to choose how this operation is techincally done.
9.1.23 grub_video_create_render_target
--------------------------------------
* Prototype:
grub_err_t
grub_video_create_render_target (struct grub_video_render_target **result, unsigned int width, unsigned int height, unsigned int mode_type);
struct grub_video_render_target {
/* This is private data for video driver. Should not be accessed from elsewhere directly. */
};
* Description:
Driver will use information provided to it to create best fitting
render target. 'mode_type' will be used to guide on selecting what
features are wanted for render target. Supported values for
'mode_type' are 'GRUB_VIDEO_MODE_TYPE_INDEX_COLOR' for index color
modes, 'GRUB_VIDEO_MODE_TYPE_RGB' for direct RGB color modes and
'GRUB_VIDEO_MODE_TYPE_ALPHA' for alpha component.
9.1.24 grub_video_delete_render_target
--------------------------------------
* Prototype:
grub_err_t
grub_video_delete_render_target (struct grub_video_render_target *target);
* Description:
Used to delete previously created render target. If 'target'
contains 'NULL' pointer, nothing will be done. If render target is
correctly destroyed, GRUB_ERR_NONE is returned.
9.1.25 grub_video_set_active_render_target
------------------------------------------
* Prototype:
grub_err_t
grub_video_set_active_render_target (struct grub_video_render_target *target);
* Description:
Sets active render target. If this comand is successful all
drawing commands will be done to specified 'target'. There is also
special values for target, 'GRUB_VIDEO_RENDER_TARGET_DISPLAY' used
to reference screen's front buffer,
'GRUB_VIDEO_RENDER_TARGET_FRONT_BUFFER' used to reference screen's
front buffer (alias for 'GRUB_VIDEO_RENDER_TARGET_DISPLAY') and
'GRUB_VIDEO_RENDER_TARGET_BACK_BUFFER' used to reference back
buffer (if double buffering is enabled). If render target is
correclty switched GRUB_ERR_NONE is returned. In no any event
shall there be non drawable active render target.
9.1.26 grub_video_get_active_render_target
------------------------------------------
* Prototype:
grub_err_t
grub_video_get_active_render_target (struct grub_video_render_target **target);
* Description:
Returns currently active render target. It returns value in
'target' that can be subsequently issued back to
'grub_video_set_active_render_target'.
File: grub-dev.info, Node: Example usage of Video API, Next: Bitmap API, Prev: Video API, Up: Video Subsystem
9.2 Example usage of Video API
==============================
9.2.1 Example of screen setup
-----------------------------
grub_err_t rc;
/* Try to initialize video mode 1024 x 768 with direct RGB. */
rc = grub_video_setup (1024, 768, GRUB_VIDEO_MODE_TYPE_RGB);
if (rc != GRUB_ERR_NONE)
{
/* Fall back to standard VGA Index Color mode. */
rc = grub_video_setup (640, 480, GRUB_VIDEO_MODE_TYPE_INDEX);
if (rc != GRUB_ERR_NONE)
{
/* Handle error. */
}
}
9.2.2 Example of setting up console viewport
--------------------------------------------
grub_uint32_t x, y, width, height;
grub_video_color_t color;
struct grub_font_glyph glyph;
grub_err_t rc;
/* Query existing viewport. */
grub_video_get_viewport (&x, &y, &width, &height);
/* Fill background. */
color = grub_video_map_color (GRUB_COLOR_BACKGROUND);
grub_video_fill_rect (color, 0, 0, width, height);
/* Setup console viewport. */
grub_video_set_viewport (x + 10, y + 10, width - 20, height - 20);
grub_video_get_viewport (&x, &y, &width, &height);
color = grub_video_map_color (GRUB_COLOR_CONSOLE_BACKGROUND);
grub_video_fill_rect (color, 0, 0, width, height);
/* Draw text to viewport. */
color = grub_video_map_color (GRUB_COLOR_CONSOLE_TEXT);
grub_font_get_glyph ('X', &glyph);
grub_video_blit_glyph (&glyph, color, 0, 0);
File: grub-dev.info, Node: Bitmap API, Prev: Example usage of Video API, Up: Video Subsystem
9.3 Bitmap API
==============
9.3.1 grub_video_bitmap_create
------------------------------
* Prototype:
grub_err_t grub_video_bitmap_create (struct grub_video_bitmap **bitmap, unsigned int width, unsigned int height, enum grub_video_blit_format blit_format)
* Description:
Creates a new bitmap with given dimensions and blitting format.
Allocated bitmap data can then be modified freely and finally
blitted with 'grub_video_blit_bitmap' to rendering target.
9.3.2 grub_video_bitmap_destroy
-------------------------------
* Prototype:
grub_err_t grub_video_bitmap_destroy (struct grub_video_bitmap *bitmap);
* Description:
When bitmap is no longer needed, it can be freed from memory using
this command. 'bitmap' is previously allocated bitmap with
'grub_video_bitmap_create' or loaded with 'grub_video_bitmap_load'.
9.3.3 grub_video_bitmap_load
----------------------------
* Prototype:
grub_err_t grub_video_bitmap_load (struct grub_video_bitmap **bitmap, const char *filename);
* Description:
Tries to load given bitmap ('filename') using registered bitmap
loaders. In case bitmap format is not recognized or supported
error 'GRUB_ERR_BAD_FILE_TYPE' is returned.
9.3.4 grub_video_bitmap_get_width
---------------------------------
* Prototype:
unsigned int grub_video_bitmap_get_width (struct grub_video_bitmap *bitmap);
* Description:
Returns bitmap width.
9.3.5 grub_video_bitmap_get_height
----------------------------------
* Prototype:
unsigned int grub_video_bitmap_get_height (struct grub_video_bitmap *bitmap);
* Description:
Return bitmap height.
9.3.6 grub_video_bitmap_get_mode_info
-------------------------------------
* Prototype:
void grub_video_bitmap_get_mode_info (struct grub_video_bitmap *bitmap, struct grub_video_mode_info *mode_info);
* Description:
Returns bitmap format details in form of 'grub_video_mode_info'.
9.3.7 grub_video_bitmap_get_data
--------------------------------
* Prototype:
void *grub_video_bitmap_get_data (struct grub_video_bitmap *bitmap);
* Description:
Return pointer to bitmap data. Contents of the pointed data can be
freely modified. There is no extra protection against going off
the bounds so you have to be carefull how to access the data.
File: grub-dev.info, Node: PFF2 Font File Format, Next: Graphical Menu Software Design, Prev: Video Subsystem, Up: Top
10 PFF2 Font File Format
************************
* Menu:
* Introduction::
* File Structure::
* Font Metrics::
File: grub-dev.info, Node: Introduction, Next: File Structure, Up: PFF2 Font File Format
10.1 Introduction
=================
The goal of this format is to provide a bitmap font format that is
simple to use, compact, and cleanly supports Unicode.
10.1.1 Goals of the GRUB Font Format
------------------------------------
* Simple to read and use. Since GRUB will only be reading the font
files, we are more concerned with making the code to read the font
simple than we are with writing the font.
* Compact storage. The fonts will generally be stored in a small
boot partition where GRUB is located, and this may be on a
removable storage device such as a CD or USB flash drive where
space is more limited than it is on most hard drives.
* Unicode. GRUB should not have to deal with multiple character
encodings. The font should always use Unicode character codes for
simple internationalization.
10.1.2 Why Another Font Format?
-------------------------------
There are many existing bitmap font formats that GRUB could use.
However, there are aspects of these formats that may make them less than
suitable for use in GRUB at this time:
'BDF'
Inefficient storage; uses ASCII to describe properties and
hexadecimal numbers in ASCII for the bitmap rows.
'PCF'
Many format variations such as byte order and bitmap padding (rows
padded to byte, word, etc.) would result in more complex code to
handle the font format.
File: grub-dev.info, Node: File Structure, Next: Font Metrics, Prev: Introduction, Up: PFF2 Font File Format
10.2 File Structure
===================
A file *section* consists of a 4-byte name, a 32-bit big-endian length
(not including the name or length), and then LENGTH more
section-type-specific bytes.
The standard file extension for PFF2 font files is '.pf2'.
10.2.1 Section Types
--------------------
'FILE'
*File type ID* (ASCII string). This must be the first section in
the file. It has length 4 and the contents are the four bytes of
the ASCII string 'PFF2'.
'NAME'
*Font name* (ASCII string). This is the full font name including
family, weight, style, and point size. For instance, "Helvetica
Bold Italic 14".
'FAMI'
*Font family name* (ASCII string). For instance, "Helvetica".
This should be included so that intelligent font substitution can
take place.
'WEIG'
*Font weight* (ASCII string). Valid values are 'bold' and
'normal'. This should be included so that intelligent font
substitution can take place.
'SLAN'
*Font slant* (ASCII string). Valid values are 'italic' and
'normal'. This should be included so that intelligent font
substitution can take place.
'PTSZ'
*Font point size* (uint16be).
'MAXW'
*Maximum character width in pixels* (uint16be).
'MAXH'
*Maximum character height in pixels* (uint16be).
'ASCE'
*Ascent in pixels* (uint16be). *Note Font Metrics::, for details.
'DESC'
*Descent in pixels* (uint16be). *Note Font Metrics::, for details.
'CHIX'
*Character index.* The character index begins with a 32-bit
big-endian unsigned integer indicating the total size of the
section, not including this size value. For each character, there
is an instance of the following entry structure:
* *Unicode code point.* (32-bit big-endian integer.)
* *Storage flags.* (byte.)
* Bits 2..0:
If equal to 000 binary, then the character data is stored
uncompressed beginning at the offset indicated by the
character's *offset* value.
If equal to 001 binary, then the character data is stored
within a compressed character definition block that
begins at the offset within the file indicated by the
character's *offset* value.
* *Offset.* (32-bit big-endian integer.)
A marker that indicates the remainder of the file is data
accessed via the character index (CHIX) section. When reading
this font file, the rest of the file can be ignored when
scanning the sections. The length should be set to -1
(0xFFFFFFFF).
Supported data structures:
Character definition Each character definition consists of:
* *Width.* Width of the bitmap in pixels. The bitmap's
extents represent the glyph's bounding box. 'uint16be'.
* *Height.* Height of the bitmap in pixels. The bitmap's
extents represent the glyph's bounding box. 'uint16be'.
* *X offset.* The number of pixels to shift the bitmap by
horizontally before drawing the character. 'int16be'.
* *Y offset.* The number of pixels to shift the bitmap by
vertically before drawing the character. 'int16be'.
* *Device width.* The number of pixels to advance
horizontally from this character's origin to the origin
of the next character. 'int16be'.
* *Bitmap data.* This is encoded as a string of bits. It
is organized as a row-major, top-down, left-to-right
bitmap. The most significant bit of each byte is taken
to be the leftmost or uppermost bit in the byte. For the
sake of compact storage, rows are not padded to byte
boundaries (i.e., a single byte may contain bits
belonging to multiple rows). The last byte of the bitmap
*is* padded with zero bits in the bits positions to the
right of the last used bit if the bitmap data does not
fill the last byte.
The length of the *bitmap data* field is (WIDTH * HEIGHT
+ 7) / 8 using integer arithmetic, which is equivalent to
ceil(WIDTH * HEIGHT / 8) using real number arithmetic.
It remains to be determined whether bitmap fonts usually
make all glyph bitmaps the same height, or if smaller
glyphs are stored with bitmaps having a lesser height.
In the latter case, the baseline would have to be used to
calculate the location the bitmap should be anchored at
on screen.
File: grub-dev.info, Node: Font Metrics, Prev: File Structure, Up: PFF2 Font File Format
10.3 Font Metrics
=================
* Ascent. The distance from the baseline to the top of most
characters. Note that in some cases characters may extend above
the ascent.
* Descent. The distance from the baseline to the bottom of most
characters. Note that in some cases characters may extend below
the descent.
* Leading. The amount of space, in pixels, to leave between the
descent of one line of text and the ascent of the next line. This
metrics is not specified in the current file format; instead, the
font rendering engine calculates a reasonable leading value based
on the other font metrics.
* Horizonal leading. The amount of space, in pixels, to leave
horizontally between the left and right edges of two adjacent
glyphs. The *device width* field determines the effective leading
value that is used to render the font.
Please fill this in.
An illustration of how the various font metrics apply to characters.
File: grub-dev.info, Node: Graphical Menu Software Design, Next: Lockdown framework, Prev: PFF2 Font File Format, Up: Top
11 Graphical Menu Software Design
*********************************
* Menu:
* Introduction_2::
* Startup Sequence::
* GUI Components::
* Command Line Window::
File: grub-dev.info, Node: Introduction_2, Next: Startup Sequence, Up: Graphical Menu Software Design
11.1 Introduction
=================
The 'gfxmenu' module provides a graphical menu interface for GRUB 2. It
functions as an alternative to the menu interface provided by the
'normal' module, which uses the grub terminal interface to display a
menu on a character-oriented terminal.
The graphical menu uses the GRUB video API, which is currently for
the VESA BIOS extensions (VBE) 2.0+. This is supported on the i386-pc
platform. However, the graphical menu itself does not depend on using
VBE, so if another GRUB video driver were implemented, the 'gfxmenu'
graphical menu would work on the new video driver as well.
File: grub-dev.info, Node: Startup Sequence, Next: GUI Components, Prev: Introduction_2, Up: Graphical Menu Software Design
11.2 Startup Sequence
=====================
* grub_enter_normal_mode [normal/main.c]
* grub_normal_execute [normal/main.c]
* read_config_file [normal/main.c]
* (When 'gfxmenu.mod' is loaded with 'insmod', it will call
'grub_menu_viewer_register()' to register itself.)
* GRUB_MOD_INIT (gfxmenu) [gfxmenu/gfxmenu.c]
* grub_menu_viewer_register [kern/menu_viewer.c]
* grub_menu_viewer_show_menu [kern/menu_viewer.c]
* get_current_menu_viewer() [kern/menu_viewer.c]
* show_menu() [gfxmenu/gfxmenu.c]
* grub_gfxmenu_model_new [gfxmenu/model.c]
* grub_gfxmenu_view_new [gfxmenu/view.c]
* set_graphics_mode [gfxmenu/view.c]
* grub_gfxmenu_view_load_theme [gfxmenu/theme_loader.c]
File: grub-dev.info, Node: GUI Components, Next: Command Line Window, Prev: Startup Sequence, Up: Graphical Menu Software Design
11.3 GUI Components
===================
The graphical menu implements a GUI component system that supports a
container-based layout system. Components can be added to containers,
and containers (which are a type of component) can then be added to
other containers, to form a tree of components. Currently, the root
component of this tree is a 'canvas' component, which allows manual
layout of its child components.
Components (non-container):
* label
* image
* progress_bar
* circular_progress
* list (currently hard coded to be a boot menu list)
Containers:
* canvas
* hbox
* vbox
The GUI component instances are created by the theme loader in
'gfxmenu/theme_loader.c' when a theme is loaded. Theme files specify
statements such as '+vbox{ +label { text="Hello" } +label{ text="World"
} }' to add components to the component tree root. By nesting the
component creation statements in the theme file, the instantiated
components are nested the same way.
When a component is added to a container, that new child is
considered *owned* by the container. Great care should be taken if the
caller retains a reference to the child component, since it will be
destroyed if its parent container is destroyed. A better choice instead
of storing a pointer to the child component is to use the component ID
to find the desired component. Component IDs do not have to be unique
(it is often useful to have multiple components with an ID of
"__timeout__", for instance).
In order to access and use components in the component tree, there
are two functions (defined in 'gfxmenu/gui_util.c') that are
particularly useful:
* 'grub_gui_find_by_id (root, id, callback, userdata)':
This function ecursively traverses the component tree rooted at
ROOT, and for every component that has an ID equal to ID, calls the
function pointed to by CALLBACK with the matching component and the
void pointer USERDATA as arguments. The callback function can do
whatever is desired to use the component passed in.
* 'grub_gui_iterate_recursively (root, callback, userdata)':
This function calls the function pointed to by CALLBACK for every
component that is a descendant of ROOT in the component tree. When
the callback function is called, the component and the void pointer
USERDATA as arguments. The callback function can do whatever is
desired to use the component passed in.
File: grub-dev.info, Node: Command Line Window, Prev: GUI Components, Up: Graphical Menu Software Design
11.4 Command Line Window
========================
The terminal window used to provide command line access within the
graphical menu is managed by 'gfxmenu/view.c'. The 'gfxterm' terminal
is used, and it has been modified to allow rendering to an offscreen
render target to allow it to be composed into the double buffering
system that the graphical menu view uses. This is bad for performance,
however, so it would probably be a good idea to make it possible to
temporarily disable double buffering as long as the terminal window is
visible. There are still unresolved problems that occur when commands
are executed from the terminal window that change the graphics mode.
It's possible that making 'grub_video_restore()' return to the graphics
mode that was in use before 'grub_video_setup()' was called might fix
some of the problems.
File: grub-dev.info, Node: Lockdown framework, Next: Copying This Manual, Prev: Graphical Menu Software Design, Up: Top
12 Lockdown framework
*********************
The GRUB can be locked down, which is a restricted mode where some
operations are not allowed. For instance, some commands cannot be used
when the GRUB is locked down.
The function 'grub_lockdown()' is used to lockdown GRUB and the
function 'grub_is_lockdown()' function can be used to check whether
lockdown is enabled or not. When enabled, the function returns
'GRUB_LOCKDOWN_ENABLED' and 'GRUB_LOCKDOWN_DISABLED' when is not
enabled.
The following functions can be used to register the commands that can
only be used when lockdown is disabled:
* 'grub_cmd_lockdown()' registers command which should not run when
the GRUB is in lockdown mode.
* 'grub_cmd_lockdown()' registers extended command which should not
run when the GRUB is in lockdown mode.
File: grub-dev.info, Node: Copying This Manual, Next: Index, Prev: Lockdown framework, Up: Top
Appendix A Copying This Manual
******************************
* Menu:
* GNU Free Documentation License:: License for copying this manual.
File: grub-dev.info, Node: GNU Free Documentation License, Up: Copying This Manual
A.1 GNU Free Documentation License
==================================
Version 1.2, November 2002
Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
0. PREAMBLE
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This License is a kind of "copyleft", which means that derivative
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It complements the GNU General Public License, which is a copyleft
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We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a
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The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name
but different contents, make the title of each such section unique
by adding at the end of it, in parentheses, the name of the
original author or publisher of that section if known, or else a
unique number. Make the same adjustment to the section titles in
the list of Invariant Sections in the license notice of the
combined work.
In the combination, you must combine any sections Entitled
"History" in the various original documents, forming one section
Entitled "History"; likewise combine any sections Entitled
"Acknowledgements", and any sections Entitled "Dedications". You
must delete all sections Entitled "Endorsements."
6. COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the
rules of this License for verbatim copying of each of the documents
in all other respects.
You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert
a copy of this License into the extracted document, and follow this
License in all other respects regarding verbatim copying of that
document.
7. AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other
separate and independent documents or works, in or on a volume of a
storage or distribution medium, is called an "aggregate" if the
copyright resulting from the compilation is not used to limit the
legal rights of the compilation's users beyond what the individual
works permit. When the Document is included in an aggregate, this
License does not apply to the other works in the aggregate which
are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half
of the entire aggregate, the Document's Cover Texts may be placed
on covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic
form. Otherwise they must appear on printed covers that bracket
the whole aggregate.
8. TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section
4. Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also
include the original English version of this License and the
original versions of those notices and disclaimers. In case of a
disagreement between the translation and the original version of
this License or a notice or disclaimer, the original version will
prevail.
If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to
Preserve its Title (section 1) will typically require changing the
actual title.
9. TERMINATION
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided for under this License. Any other
attempt to copy, modify, sublicense or distribute the Document is
void, and will automatically terminate your rights under this
License. However, parties who have received copies, or rights,
from you under this License will not have their licenses terminated
so long as such parties remain in full compliance.
10. FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of
the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
<http://www.gnu.org/copyleft/>;.
Each version of the License is given a distinguishing version
number. If the Document specifies that a particular numbered
version of this License "or any later version" applies to it, you
have the option of following the terms and conditions either of
that specified version or of any later version that has been
published (not as a draft) by the Free Software Foundation. If the
Document does not specify a version number of this License, you may
choose any version ever published (not as a draft) by the Free
Software Foundation.
A.1.1 ADDENDUM: How to use this License for your documents
----------------------------------------------------------
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:
Copyright (C) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with
the Front-Cover Texts being LIST, and with the Back-Cover Texts
being LIST.
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of free
software license, such as the GNU General Public License, to permit
their use in free software.
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