path: root/StdLib/ReadMe.txt

                           EDK II Standard Libraries
                                    ReadMe
                                 Beta Release
                               4:03 PM 8/2/2011


OVERVIEW
========
This document describes the EDK II specific aspects of installing, building, and
using the Standard C Library component of the EDK II Application Development
Kit, EADK.

The EADK is comprised of three packages: AppPkg, StdLib, and StdLibPrivateInternalFiles.

  AppPkg   This package contains applications which demonstrate use of the
           Standard C Library.
           These applications reside in AppPkg/Applications.

      Enquire  This is a program that determines many properties of the
               C compiler and the target machine that Enquire is run on.  The
               only changes required to port this 1990s era Unix program to
               EDK II were the addition of eight pragmas to enquire.c in
               order to disable some Microsoft VC++ specific warnings.

      Hello    This is a very simple EDK II native application that doesn't use
               any features of the Standard C Library.

      Main     This application is functionally identical to Hello, except that
               it uses the Standard C Library to provide a main() entry point.

      Python   A port of the Python-2.7.1 interpreter for UEFI.  This
               application is disabled by default.  Un-comment the line for
               PythonCore.inf in the [Components] section of AppPkg.dsc to
               enable building Python.

      Sockets  A collection of applications demonstrating use of the
               EDK II Socket Libraries.  These applications include:

               *   DataSink
               *   DataSource
               *   GetHostByAddr
               *   GetHostByDns
               *   GetHostByName
               *   GetNetByAddr
               *   GetNetByName
               *   GetServByName
               *   GetServByPort
               *   RecvDgram
               *   SetHostName
               *   SetSockOpt
               *   TftpServer
               *   WebServer

  StdLib   The StdLib package contains the standard header files as well as
           implementations of the standard libraries.

  StdLibPrivateInternalFiles  The contents of this package are for the
           exclusive use of the library implementations in StdLib.  Please do
           not use anything from this package in your application or else
           unexpected behavior may occur.
           This package may be removed in a future release.


RELEASE NOTES
=============
This release of the EADK has some restrictions, as described below.

    1.	Only the Microsoft VS2005 and VS2008, Intel C Compiler 10.1 (or later),
        GCC 4.3 (mingw32), GCC 4.4, and GCC 4.5 C compilers are supported for
        Ia32 or X64 CPU architectures.
        
    2.	The target machine must be running firmware which provides the
        UEFI 2.3 HII protocol.
        
    3.	The EADK has not been through Intel's Quality Assurance process. This
        means that specified standards compliance has not been validated, nor
        has it undergone formal functionality testing.
        
    4.	Applications must be launched from within the EFI Shell.
    
    5.	All file paths must use the forward slash, '/', as the separator
        character.
        
    6.	Absolute file paths may optionally be prefixed by a volume specifier
        such as "FS0:".  The volume specifier is separated from the remainder
        of the path by a single colon ':'.  The volume specifier must be one of
        the Shell's mapped volume names as shown by the "map" command.
        
    7.	Absolute file paths that don't begin with a volume specifier;
        e.g. paths that begin with "/", are relative to the currently selected
        volume.  When the EFI Shell starts, there is NO selected volume.
        
    8.	The tmpfile(), and related, functions require that the current volume
        have a temporary directory as specified in <paths.h>.  This directory
        is specified by macro _PATH_TMP.

The Standard C Library provided by this package is a "hosted" implementation
conforming to the ISO/IEC 9899-1990 C Language Standard with Addendum 1. This
is commonly referred to as the "C 95" specification or ISO/IEC 9899:199409.
The following instructions assume that you have an existing EDK II or UDK 2010
source tree that has been configured to build with your tool chain.  For
convenience, it is assumed that your EDK II source tree is located at
C:\Source\Edk2.


INSTALLATION
============
The EADK is integrated within the EDK II source tree and is included with
current EDK II check-outs.  If they are missing from your tree, they may be
installed by extracting, downloading or copying them to the root of your EDK II
source tree.  The three package directories should be peers to the Conf,
MdePkg, Nt32Pkg, etc. directories.

The Python 2.7.1 distribution must be downloaded from python.org before the
Python application can be built.  Extracting Python-2.7.1.tgz into the
AppPkg\Applications\Python directory will produce a Python-2.7.1 directory
containing the Python distribution.  Python files that had to be modified for
EDK II are in the AppPkg\Applications\Python\PyMod-2.7.1 directory.  These
files need to be copied into the corresponding directories within Python-2.7.1.

There are some boiler-plate declarations and definitions that need to be
included in your application's INF and DSC build files.  These are described
in the CONFIGURATION section, below.


BUILDING
========
It is not necessary to build the libraries separately from the target
application(s). If the application references the libraries, as described in
USAGE, below; the required libraries will be built as needed.
To build the applications included in AppPkg, one would execute the following
commands within the "Visual Studio Command Prompt" window:

    > cd C:\Source\Edk2
    > .\edksetup.bat
    > build ?a X64 ?p AppPkg\AppPkg.dsc

This will produce the application executables: Enquire.efi, Hello.efi, and
Main.efi in the C:\Source\Edk2\Build\AppPkg\DEBUG_VS2008\X64 directory; with
the DEBUG_VS2008 component being replaced with the actual tool chain and build
type you have selected in Conf\Tools_def.txt. These executables can now be
loaded onto the target platform and executed.

If you examine the AppPkg.dsc file, you will notice that the StdLib package is
referenced in order to resolve the library classes comprising the Standard
C Library.  This, plus referencing the StdLib package in your application's
.inf file is all that is needed to link your application to the standard
libraries.


USAGE
=====
This implementation of the Standard C Library is comprised of 16 separate
libraries in addition to the standard header files. Nine of the libraries are
associated with use of one of the standard headers; thus, if the header is used
in an application, it must be linked with the associated library.  Three
libraries are used to provide the Console and File-system device abstractions.
The libraries and associated header files are described in the following table.

 Library
  Class      Header File(s)    Notes
----------  ----------------  -------------------------------------------------
LibC        -- Use Always --  This library is always required.
LibCtype    ctype.h, wctype.h Character classification and mapping
LibLocale   locale.h          Localization types, macros, and functions
LibMath     math.h            Mathematical functions, types, and macros
LibStdio    stdio.h           Standard Input and Output functions, types, and
                              macros
LibStdLib   stdlib.h          General Utilities for numeric conversion, random
                              num., etc.
LibString   string.h          String copying, concatenation, comparison,
                              & search
LibSignal   signal.h          Functions and types for handling run-time
                              conditions
LibTime     time.h            Time and Date types, macros, and functions
LibUefi     sys/EfiSysCall.h  Provides the UEFI system interface and
                              "System Calls"
LibWchar    wchar.h           Extended multibyte and wide character utilities
LibNetUtil                    Network address and number manipulation utilities
DevConsole                    Automatically provided  File I/O abstractions for
                              the UEFI Console device.  No need to list this
                              library class in your INF file(s).
DevShell    Add if desired    File I/O abstractions using UEFI shell
                              facilities.  Add this to the application's main
                              INF file if file-system access needed.
DevUtility  -- Do Not Use --  Utility functions used by the Device abstractions
LibGdtoa    -- Do Not Use --  This library is used internally and should not
                              need to be explicitly specified by an
                              application.  It must be defined as one of the
                              available library classes in the application's
                              DSC file.

                         Table 1:  Standard Libraries
                         ============================


These libraries must be fully described in the [LibraryClasses] section of the
application package's DSC file. Then, each individual application needs to
specify which libraries to link to by specifying the Library Class, from the
above table, in the [LibraryClasses] section of the application's INF file. The
AppPkg.dsc, StdLib.dsc, and Enquire.inf files provide good examples of this.
More details are in the CONFIGURATION section, below.

Within the source files of the application, use of the Standard headers and
library functions follow standard C programming practices as formalized by
ISO/IEC 9899:1990, with Addendum 1, (C 95) C language specification.


CONFIGURATION
=============
DSC Files
---------

All EDK II packages which build applications that use the standard libraries
must include some "boilerplate" text in the package's .dsc file.  To make it
easier, and to reduce cut-and-paste errors, the "boilerplate" text has been
consolidated into a single file, StdLib/StdLib.inc, which can be included in
your .dsc file using the !include directive.  The provided AppPkg.dsc and
StdLib.dsc files do this on their last line.

Each affected section of the DSC file is described below.

  [LibraryClasses]
    #
    # Common Libraries
    #
    BaseLib|MdePkg/Library/BaseLib/BaseLib.inf
    BaseMemoryLib|MdePkg/Library/BaseMemoryLib/BaseMemoryLib.inf

    TimerLib|PerformancePkg/Library/DxeTscTimerLib/DxeTscTimerLib.inf
    # To run in an emulation environment, such as NT32, comment out
    # the TimerLib description above and un-comment the line below.
    # TimerLib| MdePkg/Library/BaseTimerLibNullTemplate/BaseTimerLibNullTemplate.inf

    #
    # C Standard Libraries
    #
    LibC|StdLib/LibC/LibC.inf
    LibStdLib|StdLib/LibC/StdLib/StdLib.inf
    LibString|StdLib/LibC/String/String.inf
    LibWchar|StdLib/LibC/Wchar/Wchar.inf
    LibCType|StdLib/LibC/Ctype/Ctype.inf
    LibTime|StdLib/LibC/Time/Time.inf
    LibStdio|StdLib/LibC/Stdio/Stdio.inf
    LibGdtoa|StdLib/LibC/gdtoa/gdtoa.inf
    LibLocale|StdLib/LibC/Locale/Locale.inf
    LibUefi|StdLib/LibC/Uefi/Uefi.inf
    LibMath|StdLib/LibC/Math/Math.inf
    LibSignal|StdLib/LibC/Signal/Signal.inf
    LibNetUtil|StdLib/LibC/LibGcc/LibGcc.inf

  # Libraries for device abstractions within the Standard C Library.
  # Applications should not directly access any functions defined
  # in these libraries.
    DevUtility|StdLib/LibC/Uefi/Devices/daUtility.inf
    DevConsole|StdLib/LibC/Uefi/Devices/daConsole.inf
    DevShell|StdLib/LibC/Uefi/Devices/daShell.inf

                     Figure 1: Library Class Descriptions
                     ====================================


Descriptions of the Library Classes comprising the Standard Libraries must be
included in your application package's DSC file, as shown in Figure 1: Library
Class Descriptions, above.

The directives in Figure 2: Package Component Descriptions will create
instances of the BaseLib and BaseMemoryLib library classes that are built
with Link-time-Code-Generation disabled.  This is necessary when using the
Microsoft tool chains in order to allow the library's functions to be
resolved during the second pass of the linker during Link-Time-Code-Generation
of the application.

  [Components]
  # BaseLib and BaseMemoryLib need to be built with the /GL- switch
  # when using the Microsoft tool chains.  This is required so that
  # the library functions can be resolved during the second pass of
  # the linker during link-time-code-generation.
  #
    MdePkg/Library/BaseLib/BaseLib.inf {
      <BuildOptions>
        MSFT:*_*_*_CC_FLAGS = /X /Zc:wchar_t /GL-
    }
    MdePkg/Library/BaseMemoryLib/BaseMemoryLib.inf {
      <BuildOptions>
        MSFT:*_*_*_CC_FLAGS = /X /Zc:wchar_t /GL-
    }

                    Figure 2: Package Component Descriptions
                    ========================================


The NULL TimerLib instance must be selected if you desire to run your
application under an emulation environment -- unless there is a supported
TimerLib for that environment.  For example, the InOsEmuPkg provides a
DxeTimerLib which can be used for the TimerLib instance.

The "boilerplate" text in StdLib.inc will automatically adjust which Timer
Library is instantiated based upon whether the $(EMULATE) macro has been
defined, or not.

  ###
  # Select the correct TimerLib instance depending upon whether running under
  # an emulation environment, or not.
  !ifndef $(EMULATE)
    # Not running in an Emulation Environment
  [LibraryClasses.IA32.UEFI_APPLICATION]
    TimerLib|PerformancePkg/Library/DxeTscTimerLib/DxeTscTimerLib.inf

  [LibraryClasses.X64.UEFI_APPLICATION]
    TimerLib|PerformancePkg/Library/DxeTscTimerLib/DxeTscTimerLib.inf

  [LibraryClasses.IPF.UEFI_APPLICATION]
    PalLib|MdePkg/Library/UefiPalLib/UefiPalLib.inf
    TimerLib|MdePkg/Library/SecPeiDxeTimerLibCpu/SecPeiDxeTimerLibCpu.inf

  !else
    # Use this instance if Running in an Emulation Environment.
  [LibraryClasses.Common.UEFI_APPLICATION]
    TimerLib|MdePkg/Library/BaseTimerLibNullTemplate/BaseTimerLibNullTemplate.inf
  !endif

                      Figure 3: Timer Library Selection
                      =================================


Each compiler assumes, by default, that it will be used with standard libraries
and headers provided by the compiler vendor.  Many of these assumptions are
incorrect for the UEFI environment.  By including a BuildOptions section, as
shown in Figure 3: Package Build Options, these assumptions can be
tailored for compatibility with UEFI and the EDK II Standard Libraries.

  [BuildOptions]
    INTEL:*_*_IA32_CC_FLAGS  = /Qfreestanding
     MSFT:*_*_IA32_CC_FLAGS  = /X /Zc:wchar_t
      GCC:*_*_IA32_CC_FLAGS  = /ffreestanding ?nostdinc ?nostdlib

  # The Build Options, below, are only used when building the C library
  # to be run under an emulation environment.  The clock() system call
  # is modified to return -1 indicating that it is unsupported.
  # Just un-comment the lines below and select the correct
  # TimerLib instance, above.

    # INTEL:*_*_IA32_CC_FLAGS  = /D NT32dvm
    #  MSFT:*_*_IA32_CC_FLAGS  = /D NT32dvm
    #   GCC:*_*_IA32_CC_FLAGS  = -DNT32dvm

                        Figure 4: Package Build Options
                        ===============================

The "boilerplate" text can be included using a !include directive in the
package's .dsc file.  The provided AppPkg.dsc and StdLib.dsc files include
the "boilerplate" text as follows:

  # Include Boilerplate text required for building with the Standard Libraries.
  #
  #############################################################################
  !include StdLib/StdLib.inc

                      Figure 5: "Boilerplate" Inclusion
                      =================================


INF Files
=========
The INF files for most modules will not require special directives in order to
support the Standard Libraries.  The two cases which could occur are described
below.

  [LibraryClasses]
    UefiLib
    LibC
    LibString
    LibStdio
    DevShell
  
                      Figure 6: Module Library Classes
                      ================================


Modules of type UEFI_APPLICATION that perform file I/O should include library
class DevShell.  Including this library class will allow file operations to be
handled by the UEFI Shell.  Without this class, only Console I/O is permitted.

 [BuildOptions]
  INTEL:*_*_*_CC_FLAGS          = /Qdiag-disable:181,186
   MSFT:*_*_*_CC_FLAGS          = /Oi- /wd4018 /wd4131
    GCC:*_*_IPF_SYMRENAME_FLAGS = --redefine-syms=Rename.txt
    
                        Figure 7: Module Build Options
                        ==============================


An application's INF file may need to include a [BuildOptions] section
specifying additional compiler and linker flags necessary to allow the
application to be built. Usually, this section is not needed.  When building
code from external sources, though, it may be necessary to disable some
warnings or enable/disable some compiler features.


IMPLEMENTATION-Specific Features
================================
It is very strongly recommended that applications not use the long or
unsigned long types. The size of this type varies between compilers and is one
of the less portable aspects of C. Instead, one should use the UEFI defined
types whenever possible. Use of these types, listed below for reference,
ensures that the declared objects have unambiguous, explicitly declared, sizes
and characteristics.

        UINT64   INT64     UINT32   INT32   UINT16   CHAR16
        INT16    BOOLEAN   UINT8    CHAR8   INT8
        UINTN    INTN                       PHYSICALADDRESS

There are similar types declared in sys/types.h and related files.

The types UINTN and INTN have the native width of the target processor
architecture. Thus, INTN on IA32 has a width of 32 bits while INTN on X64 and
IPF has a width of 64 bits.

For maximum portability, data objects intended to hold addresses should be
declared with type intptr_t or uintptr_t. These types, declared in
sys/stdint.h, can be used to create objects capable of holding pointers. Note
that these types will generate different sized objects on different processor
architectures.  If a constant size across all processors and compilers is
needed, use type PHYSICAL_ADDRESS.

Though not specifically required by the ISO/IEC 9899 standard, this
implementation of the Standard C Library provides the following system calls
which are declared in sys/EfiSysCall.h.

          close   dup      dup2     fcntl
          fstat   getcwd   ioctl    isatty
          lseek   lstat    mkdir    open
          poll    read     rename   rmdir
          stat    unlink   write

The open function will accept file names of "stdin:", "stdout:", and "stderr:"
which cause the respective streams specified in the UEFI System Table to be
opened.  Normally, these are associated with the console device.  When the
application is first started, these streams are automatically opened on File
Descriptors 0, 1, and 2 respectively.