nuclei-sdk/doc/source/develop/buildsystem.rst

.. _develop_buildsystem:

Build System based on Makefile
==============================

Nuclei SDK's build system is based on Makefile, user can build,
run ordebug application in Windows and Linux.

.. _develop_buildsystem_structure:

Makefile Structure
------------------

Nuclei SDK's Makefiles mainly placed in **<NUCLEI_SDK_ROOT>/Build** directory and
an extra *Makefile* located in **<NUCLEI_SDK_ROOT>/Makefile**.

This extra **<NUCLEI_SDK_ROOT>/Makefile** introduce a new Make variable called
**PROGRAM** to provide the ability to build or run application in **<NUCLEI_SDK_ROOT>**.

For example, if you want to *rebuild and upload* application **application/baremetal/timer_test**,
you can run ``make PROGRAM=application/baremetal/timer_test clean upload`` to achieve it.


The **<NUCLEI_SDK_ROOT>/Build** directory content list as below:

.. code-block:: text

    gmsl/
    Makefile.base
    Makefile.conf
    Makefile.core
    Makefile.components
    Makefile.files
    Makefile.global  -> Created by user
    Makefile.misc
    Makefile.rtos
    Makefile.rules
    Makefile.soc

The file or directory is used explained as below:

.. _develop_buildsystem_makefile_base:

Makefile.base
~~~~~~~~~~~~~

This **Makefile.base** file is used as Nuclei SDK build system entry file,
application's Makefile need to include this file to use all the features of
Nuclei SDK build system.

It will expose Make variables or options such as **BOARD** or **SOC** passed
by ``make`` command, click :ref:`develop_buildsystem_exposed_make_vars`
to learn more.

This file will include optional :ref:`develop_buildsystem_makefile_global`
and :ref:`develop_buildsystem_makefile_local` which allow user to set custom
global Makefile configurations and local application Makefile configurations.

This file will include the following makefiles:

* :ref:`develop_buildsystem_gmsl`: additional library functions provided via gmsl
* :ref:`develop_buildsystem_makefile_misc`: misc functions and OS check helpers
* :ref:`develop_buildsystem_makefile_conf`: main Makefile configuration entry
* :ref:`develop_buildsystem_makefile_rules`: make rules of this build system

.. _develop_buildsystem_gmsl:

gmsl
~~~~

The **gmsl** directory consist of the `GNU Make Standard Library (GMSL)`_,
which is an a library of functions to be used with GNU Make's $(call) that
provides functionality not available in standard GNU Make.

We use this **gmsl** tool to make sure we help us achieve some linux command
which is only supported in Linux.

.. _develop_buildsystem_makefile_misc:

Makefile.misc
~~~~~~~~~~~~~

This **Makefile.misc** file mainly provide these functions:

* Define **get_csrcs**, **get_asmsrcs**, **get_cxxsrcs** and **check_item_exist** make functions

  - **get_csrcs**: Function to get ``*.c or *.C`` source files from a list of directories, no ability to
    do recursive match. e.g. ``$(call get_csrcs, csrc csrc/abc)`` will return c source files in
    ``csrc`` and ``csrc/abc`` directories.
  - **get_asmsrcs**: Function to get ``*.s or *.S`` source files from a list of directories, no ability to
    do recursive match. e.g. ``$(call get_asmsrcs, asmsrc asmsrc/abc)`` will return asm source files in
    ``asmsrc`` and ``asmsrc/abc`` directories.
  - **get_cxxsrcs**: Function to get ``*.cpp or *.CPP`` source files from a list of directories, no ability
    to do recursive match. e.g. ``$(call get_cxxsrcs, cppsrc cppsrc/abc)`` will return cpp source files in
    ``cppsrc`` and ``cppsrc/abc`` directories.
  - **check_item_exist**: Function to check if item existed in a set of items. e.g.
    ``$(call check_item_exist, flash, flash ilm flashxip)`` will check ``flash`` whether existed in
    ``flash ilm flashxip``, if existed, return ``flash``, otherwise return empty.

* Check and define OS related functions, and also a set of trace print functions.

.. _develop_buildsystem_makefile_conf:

Makefile.conf
~~~~~~~~~~~~~

This **Makefile.conf** file will define the following items:

* Toolchain related variables used during compiling
* Debug related variables
* Include :ref:`develop_buildsystem_makefile_files` and :ref:`develop_buildsystem_makefile_rtos`
* Collect all the C/C++/ASM compiling and link options

.. _develop_buildsystem_makefile_rules:

Makefile.rules
~~~~~~~~~~~~~~

This **Makefile.rules** file will do the following things:

* Collect all the sources during compiling
* Define all the rules used for building, uploading and debugging
* Print help message for build system


.. _develop_buildsystem_makefile_files:

Makefile.files
~~~~~~~~~~~~~~

This **Makefile.files** file will do the following things:

* Define common C/C++/ASM source and include directories
* Define common C/C++/ASM macros

.. _develop_buildsystem_makefile_soc:

Makefile.soc
~~~~~~~~~~~~

This **Makefile.soc** will include valid makefiles located in
**<NUCLEI_SDK_ROOT>/SoC/<SOC>/build.mk** according to
the :ref:`develop_buildsystem_var_soc` makefile variable setting.

It will define the following items:

* **DOWNLOAD** and **CORE** variables

  - For :ref:`design_soc_demosoc`, we can support all the modes defined in
    :ref:`develop_buildsystem_var_download`, and **CORE** list defined in
    :ref:`develop_buildsystem_makefile_core`
  - For :ref:`design_soc_gd32vf103`, The **CORE** is fixed to N205, since
    it is a real SoC chip, and only **FlashXIP** download mode is supported

* Linker script used according to the **DOWNLOAD** mode settings
* OpenOCD debug configuration file used for the SoC and Board
* Some extra compiling or debugging options

A valid SoC should be organized like this, take ``demosoc`` as example:

.. code-block::

    SoC/demosoc
    ├── Board
    │   └── nuclei_fpga_eval
    │       ├── Include
    │       │   ├── board_nuclei_fpga_eval.h
    │       │   └── nuclei_sdk_hal.h
    │       ├── Source
    │       │   └── GCC
    │       └── openocd_demosoc.cfg
    ├── build.mk
    └── Common
        ├── Include
        │   ├── demosoc.h
        │   ├── ... ...
        │   ├── demosoc_uart.h
        │   ├── nuclei_sdk_soc.h
        │   └── system_demosoc.h
        └── Source
            ├── Drivers
            │   ├── ... ...
            │   └── demosoc_uart.c
            ├── GCC
            │   ├── intexc_demosoc.S
            │   └── startup_demosoc.S
            ├── Stubs
            │   ├── read.c
            │   ├── ... ...
            │   └── write.c
            ├── demosoc_common.c
            └── system_demosoc.c


.. _develop_buildsystem_makefile_rtos:

Makefile.rtos
~~~~~~~~~~~~~

This **Makefile.rtos** will include **<NUCLEI_SDK_ROOT>/OS/<RTOS>/build.mk**
according to our :ref:`develop_buildsystem_var_rtos` variable.

A valid rtos should be organized like this, take ``UCOSII`` as example:

.. code-block::

    OS/UCOSII/
    ├── arch
    ├── build.mk
    ├── license.txt
    ├── readme.md
    └── source


If no :ref:`develop_buildsystem_var_rtos` is chosen, then RTOS
code will not be included during compiling, user will develop
baremetal application.

If **FreeRTOS**, **UCOSII** or **RTThread** RTOS is chosen, then FreeRTOS
UCOSII, or RTThread source code will be included during compiling, and extra
compiler option ``-DRTOS_$(RTOS_UPPER)`` will be passed, then user can develop RTOS application.

For example, if ``FreeRTOS`` is selected, then ``-DRTOS_FREERTOS`` compiler option
will be passed.

.. _develop_buildsystem_makefile_components:

Makefile.components
~~~~~~~~~~~~~~~~~~~

This **Makefile.components** will include ``build.mk`` Makefiles of selected components defined
via makefile variable :ref:`develop_buildsystem_var_middleware`, the Makefiles are placed in
the sub-folders of **<NUCLEI_SDK_ROOT>/Components/**.

A valid middleware component should be organized like this, take ``fatfs`` as example :

.. code-block::

    Components/fatfs/
    ├── build.mk
    ├── documents
    ├── LICENSE.txt
    └── source


For example, if there are two valid middleware components in **<NUCLEI_SDK_ROOT>/Components/**, called
``fatfs`` and ``tjpgd``, and you want to use them in your application, then you can set ``MIDDLEWARE``
like this ``MIDDLEWARE := fatfs tjpgd``, then the application will include these two middlewares into
build process.

.. _develop_buildsystem_makefile_core:

Makefile.core
~~~~~~~~~~~~~

This **Makefile.core** is used to define the RISC-V ARCH and ABI used during
compiling of the CORE list supported.

If you want to add a new **CORE**, you need to add a new line before **SUPPORTED_CORES**,
and append the new **CORE** to **SUPPORTED_CORES**.

For example, if you want to add a new **CORE** called **n308**, and the **n308**'s
**ARCH** and **ABI** are ``rv32imafdc`` and ``ilp32d``, then you can add a new line
like this ``N308_CORE_ARCH_ABI = rv32imafdc ilp32d``, and append **n308** to **SUPPORTED_CORES**
like this ``SUPPORTED_CORES = n201 n201e n203 n203e n205 n205e n305 n307 n307fd n308 nx600``

.. note::

   * The appended new **CORE** need to lower-case, e.g. *n308*
   * The new defined variable **N308_CORE_ARCH_ABI** need to be all upper-case.


.. _develop_buildsystem_makefile_global:

Makefile.global
~~~~~~~~~~~~~~~

This **Makefile.global** file is an optional file, and will not be tracked by git,
user can create own **Makefile.global** in **<NUCLEI_SDK_ROOT>/Build** directory.

In this file, user can define custom **SOC**, **BOARD**, **DOWNLOAD** options to
overwrite the default configuration.

For example, if you will use only the :ref:`design_board_gd32vf103v_rvstar`, you can
create the **<NUCLEI_SDK_ROOT>/Build/Makefile.global** as below:

.. code-block:: Makefile

    SOC ?= gd32vf103
    BOARD ?= gd32vf103v_rvstar
    DOWNLOAD ?= flashxip

.. note::

    * If you add above file, then you can build, run, debug application without passing
      **SOC**, **BOARD** and **DOWNLOAD** variables using make command for
      :ref:`design_board_gd32vf103v_rvstar` board, e.g.

      - Build and run application for :ref:`design_board_gd32vf103v_rvstar`: ``make run``
      - Debug application for :ref:`design_board_gd32vf103v_rvstar`: ``make debug``

    * The :ref:`design_board_gd32vf103v_rvstar` only support ``FlashXIP`` download mode.
    * If you create the **Makefile.global** like above sample code, you will also be able
      to use Nuclei SDK build system as usually, it will only change the default **SOC**,
      **BOARD** and **DOWNLOAD**, but you can still override the default variable using
      make command, such as ``make SOC=demosoc BOARD=nuclei_fpga_eval DOWNLOAD=ilm``

.. _develop_buildsystem_makefile_local:

Makefile.local
~~~~~~~~~~~~~~

As the :ref:`develop_buildsystem_makefile_global` is used to override the default Makefile
configurations, and the **Makefile.local** is used to override application level Makefile
configurations, and also this file will not be tracked by git.

User can create ``Makefile.local`` file in any of the application folder, placed together with
the application Makefile, for example, you can create ``Makefile.local`` in ``application/baremetal/helloworld``
to override default make configuration for this **helloworld** application.

If you want to change the default board for **helloworld** to use :ref:`design_board_gd32vf103v_rvstar`,
you can create ``application/baremetal/helloworld/Makefile.local`` as below:

.. code-block:: Makefile

    SOC ?= gd32vf103
    BOARD ?= gd32vf103v_rvstar
    DOWNLOAD ?= flashxip

.. note::

    * This local make configuration will override global and default make configuration.
    * If you just want to change only some applications' makefile configuration, you can
      add and update ``Makefile.local`` for those applications.


.. _develop_buildsystem_make_targets:

Makefile targets of make command
--------------------------------

Here is a list of the :ref:`table_dev_buildsystem_4`.

.. _table_dev_buildsystem_4:

.. list-table:: Make targets supported by Nuclei SDK Build System
   :widths: 20 80
   :header-rows: 1
   :align: center

   * - target
     - description
   * - help
     - display help message of Nuclei SDK build system
   * - info
     - display selected configuration information
   * - all
     - build application with selected configuration
   * - clean
     - clean application with selected configuration
   * - dasm
     - build and dissemble application with selected configuration
   * - bin
     - build and generate application binary with selected configuration
   * - upload
     - build and upload application with selected configuration
   * - run_openocd
     - run openocd server with selected configuration, and wait for gdb at port specified by $(GDB_PORT)
   * - run_gdb
     - build and start gdb process with selected configuration, and connect to localhost:$(GDB_PORT)
   * - debug
     - build and debug application with selected configuration
   * - run_qemu
     - run application on qemu machine with selected configuration
   * - run_xlspike
     - run application on xlspike with selected configuration
   * - size
     - show program size

.. note::

   * The selected configuration is controlled by
     :ref:`develop_buildsystem_exposed_make_vars`
   * For ``run_openocd`` and ``run_gdb`` target, if you want to
     change a new gdb port, you can pass the variable
     :ref:`develop_buildsystem_var_gdb_port`
   * For ``run_qemu``, only ``SOC=demosoc or SOC=gd32vf103`` supported,
     when do this target, you can pass ``SIMU=qemu`` to support auto-exit,
     project recompiling is required.
   * For ``run_xlspike``, only ``SOC=demosoc`` supported,
     when do this target, you can pass ``SIMU=xlspike`` to support auto-exit,
     project recompiling is required.

.. _develop_buildsystem_exposed_make_vars:

Makefile variables passed by make command
-----------------------------------------

In Nuclei SDK build system, we exposed the following Makefile variables
which can be passed via make command.

* :ref:`develop_buildsystem_var_soc`
* :ref:`develop_buildsystem_var_board`
* :ref:`develop_buildsystem_var_variant`
* :ref:`develop_buildsystem_var_download`
* :ref:`develop_buildsystem_var_core`
* :ref:`develop_buildsystem_var_archext`
* :ref:`develop_buildsystem_var_simulation`
* :ref:`develop_buildsystem_var_gdb_port`
* :ref:`develop_buildsystem_var_v`
* :ref:`develop_buildsystem_var_silent`

.. note::

   * These variables can also be used and defined in application Makefile
   * If you just want to fix your running board of your application, you can
     just define these variables in application Makefile, if defined, then
     you can simply use ``make clean``, ``make upload`` or ``make debug``, etc.


.. _develop_buildsystem_var_soc:

SOC
~~~

**SOC** variable is used to declare which SoC is used in application during compiling.

You can easily find the supported SoCs in the **<NUCLEI_SDK_ROOT>/SoC** directory.

Currently we support the following SoCs, see :ref:`table_dev_buildsystem_1`.

.. _table_dev_buildsystem_1:

.. list-table:: Supported SoCs
   :widths: 10, 60
   :header-rows: 1
   :align: center

   * - **SOC**
     - Reference
   * - gd32vf103
     - :ref:`design_soc_gd32vf103`
   * - demosoc
     - :ref:`design_soc_demosoc`

.. note::

   If you are our SoC subsystem customer, in the SDK delivered to you, you can find your soc name
   in this **<NUCLEI_SDK_ROOT>/SoC** directory, take ``gd32vf103`` SoC as example, when ``SOC=gd32vf103``,
   the SoC source code in **<NUCLEI_SDK_ROOT>/SoC/gd32vf103/Common** will be used.

   This documentation just document the open source version of Nuclei SDK's supported SOC and Board.

.. _develop_buildsystem_var_board:

BOARD
~~~~~

**BOARD** variable is used to declare which Board is used in application during compiling.

The **BOARD** variable should match the supported boards of chosen **SOC**.
You can easily find the supported Boards in the **<NUCLEI_SDK_ROOT>/<SOC>/Board/** directory.

* :ref:`table_dev_buildsystem_2`
* :ref:`table_dev_buildsystem_3`


Currently we support the following SoCs.

.. _table_dev_buildsystem_2:

.. list-table:: Supported Boards when SOC=gd32vf103
   :widths: 20, 60
   :header-rows: 1
   :align: center

   * - **BOARD**
     - Reference
   * - gd32vf103v_rvstar
     - :ref:`design_board_gd32vf103v_rvstar`
   * - gd32vf103v_eval
     - :ref:`design_board_gd32vf103v_eval`
   * - gd32vf103c_longan_nano
     - :ref:`design_board_sipeed_longan_nano`
   * - gd32vf103c_t_display
     - :ref:`design_board_sipeed_longan_nano`

.. _table_dev_buildsystem_3:

.. list-table:: Supported Boards when SOC=demosoc
   :widths: 10 60
   :header-rows: 1
   :align: center

   * - **BOARD**
     - Reference
   * - nuclei_fpga_eval
     - :ref:`design_board_nuclei_fpga_eval`

.. note::

    * If you only specify **SOC** variable in make command, it will use default **BOARD**
      and **CORE** option defined in **<NUCLEI_SDK_ROOT>/SoC/<SOC>/build.mk**
    * If you are our SoC subsystem customer, in the SDK delivered to you, you can check
      the board supported list in **<NUCLEI_SDK_ROOT>/<SOC>/Board/**, take ``SOC=gd32vf103 BOARD=gd32vf103v_rvstar``
      as example, the board source code located **<NUCLEI_SDK_ROOT>/gd32vf103/Board/gd32vf103v_rvstar** will be used.

.. _develop_buildsystem_var_variant:

VARIANT
~~~~~~~

**VARIANT** variable is used to declare which variant of board is used in application during compiling.

It might only affect on only small piece of board, and this is SoC and Board dependent.

This variable only affect the selected board or soc, and it is target dependent.


.. _develop_buildsystem_var_download:

DOWNLOAD
~~~~~~~~

**DOWNLOAD** variable is used to declare the download mode of the application,
currently it has these modes supported as described in table
:ref:`table_dev_buildsystem_5`

.. _table_dev_buildsystem_5:

.. list-table:: Supported download modes
   :widths: 10 70
   :header-rows: 1
   :align: center

   * - **DOWNLOAD**
     - Description
   * - ilm
     - | Program will be download into ilm/ram and
       | run directly in ilm/ram, program will lost when poweroff
   * - flash
     - | Program will be download into flash, when running,
       | program will be copied to ilm/ram and run in ilm/ram
   * - flashxip
     - Program will to be download into flash and run directly in flash
   * - ddr
     - | Program will to be download into ddr and
       | run directly in ddr, program will lost when poweroff

.. note::

    * This variable now target dependent, and its meaning depending on how this
      variable is implemented in SoC's build.mk
    * :ref:`design_soc_gd32vf103` only support **DOWNLOAD=flashxip**
    * :ref:`design_soc_demosoc` support all the download modes.
    * **flashxip** mode in :ref:`design_soc_demosoc` is very slow due to
      the CORE frequency is very slow, and flash execution speed is slow
    * **ddr** mode is introduced in release ``0.2.5`` of Nuclei SDK
    * macro ``DOWNLOAD_MODE`` and ``DOWNLOAD_MODE_STRING`` will be defined in Makefile,
      eg. when ``DOWNLOAD=flash``, macro will be defined as ``-DDOWNLOAD_MODE=DOWNLOAD_MODE_FLASH``,
      and ``-DDOWNLOAD_MODE_STRING=\"flash\"``, the ``flash`` will be in upper case,
      currently ``DOWNLOAD_MODE_STRING`` macro is used in ``system_<Device>.c`` when
      banner is print.
    * This download mode is also used to clarify whether in the link script,
      your eclic vector table is placed in ``.vtable_ilm`` or ``.vtable`` section, eg.
      for demosoc, when ``DOWNLOAD=flash``, vector table is placed in ``.vtable_ilm`` section,
      and an extra macro called ``VECTOR_TABLE_REMAPPED`` will be passed in Makefile.
      When ``VECTOR_TABLE_REMAPPED`` is defined, it means vector table's LMA and VMA are
      different, it is remapped.
    * From release ``0.3.2``, this ``DOWNLOAD_MODE`` should not be used, and macros
      ``DOWNLOAD_MODE_ILM``, ``DOWNLOAD_MODE_FLASH``, ``DOWNLOAD_MODE_FLASHXIP`` and
      ``DOWNLOAD_MODE_DDR`` previously defined in ``riscv_encoding.h`` now are moved to
      ``<Device.h>`` such as ``demosoc.h``, and should be deprecated in future.
      Now we are directly using ``DOWNLOAD_MODE_STRING`` to pass the download mode string,
      no longer need to define it in source code as before.
    * From release ``0.3.2``, you can define **DOWNLOAD** not just the download mode list above,
      you can use other download mode names specified by your customized SoC.

.. _develop_buildsystem_var_core:

CORE
~~~~

**CORE** variable is used to declare the Nuclei processor core
of the application.

Currently it has these cores supported as described in table
:ref:`table_dev_buildsystem_6`.

.. _table_dev_buildsystem_6:

.. table:: Supported Nuclei Processor cores
   :widths: 20 20 20
   :align: center

   ========  ========== =======  =================
   **CORE**  **ARCH**   **ABI**       **TUNE**
   n201      rv32iac    ilp32    nuclei-200-series
   n201e     rv32eac    ilp32e   nuclei-200-series
   n203      rv32imac   ilp32    nuclei-200-series
   n203e     rv32emac   ilp32e   nuclei-200-series
   n205      rv32imac   ilp32    nuclei-200-series
   n205e     rv32emac   ilp32e   nuclei-200-series
   n300      rv32imac   ilp32    nuclei-300-series
   n300f     rv32imafc  ilp32f   nuclei-300-series
   n300fd    rv32imafdc ilp32d   nuclei-300-series
   n305      rv32imac   ilp32    nuclei-300-series
   n307      rv32imafc  ilp32f   nuclei-300-series
   n307fd    rv32imafdc ilp32d   nuclei-300-series
   n600      rv32imac   ilp32    nuclei-600-series
   n600f     rv32imafc  ilp32f   nuclei-600-series
   n600fd    rv32imafdc ilp32d   nuclei-600-series
   nx600     rv64imac   lp64     nuclei-600-series
   nx600f    rv64imafc  lp64f    nuclei-600-series
   nx600fd   rv64imafdc lp64d    nuclei-600-series
   ux600     rv64imac   lp64     nuclei-600-series
   ux600f    rv64imafc  lp64f    nuclei-600-series
   ux600fd   rv64imafdc lp64d    nuclei-600-series
   n900      rv32imac   ilp32    nuclei-900-series
   n900f     rv32imafc  ilp32f   nuclei-900-series
   n900fd    rv32imafdc ilp32d   nuclei-900-series
   nx900     rv64imac   lp64     nuclei-900-series
   nx900f    rv64imafc  lp64f    nuclei-900-series
   nx900fd   rv64imafdc lp64d    nuclei-900-series
   ux900     rv64imac   lp64     nuclei-900-series
   ux900f    rv64imafc  lp64f    nuclei-900-series
   ux900fd   rv64imafdc lp64d    nuclei-900-series
   ========  ========== =======  =================

When **CORE** is selected, the **ARCH**, **ABI** and **TUNE** (optional) are set,
and it might affect the compiler options in combination with :ref:`develop_buildsystem_var_archext`
depended on the implementation of SoC build.mk.

Take ``SOC=demosoc`` as example.

- If **CORE=n205 ARCH_EXT=**, then ``ARCH=rv32imac, ABI=ilp32 TUNE=nuclei-200-series``. 
  riscv arch related compile and link options will be passed, for this case, it will be
  ``-march=rv32imac -mabi=ilp32 -mtune=nuclei-200-series``.

- If **CORE=n205 ARCH_EXT=b**, it will be ``-march=rv32imacb -mabi=ilp32 -mtune=nuclei-200-series``.

For riscv code model settings, the ``RISCV_CMODEL`` variable will be set to medlow
for RV32 targets, otherwise it will be medany.

The some SoCs, the CORE is fixed, so the ARCH and ABI will be fixed, such as
``gd32vf103`` SoC, in build system, the CORE is fixed to n205, and ARCH=rv32imac, ABI=ilp32.

.. _develop_buildsystem_var_archext:

ARCH_EXT
~~~~~~~~

**ARCH_EXT** variable is used to select extra RISC-V arch extensions supported by Nuclei
RISC-V Processor, except the ``iemafdc``.

Currently, valid arch extension combination should match the order of ``bpv``.

Here is a list of valid arch extensions:

* **ARCH_EXT=b**: RISC-V bitmanipulation extension.
* **ARCH_EXT=p**: RISC-V packed simd extension.
* **ARCH_EXT=v**: RISC-V vector extension.
* **ARCH_EXT=bp**: RISC-V bitmanipulation and packed simd extension.
* **ARCH_EXT=pv**: RISC-V packed simd and vector extension.
* **ARCH_EXT=bpv**: RISC-V bitmanipulation, packed simd and vector extension.

It is suggested to use this ARCH_EXT with other arch options like this, can be found in
``SoC/demosoc/build.mk``:


.. code-block:: makefile

    # Set RISCV_ARCH and RISCV_ABI
    CORE_UPPER := $(call uc, $(CORE))
    CORE_ARCH_ABI := $($(CORE_UPPER)_CORE_ARCH_ABI)
    RISCV_ARCH ?= $(word 1, $(CORE_ARCH_ABI))$(ARCH_EXT)
    RISCV_ABI ?= $(word 2, $(CORE_ARCH_ABI))


.. _develop_buildsystem_var_simulation:

SIMULATION
~~~~~~~~~~

If **SIMULATION=1**, it means the program is optimized for hardware simulation environment.

Currently if **SIMULATION=1**, it will pass compile option **-DCFG_SIMULATION**,
application can use this **CFG_SIMULATION** to optimize program for hardware
simulation environment.

.. note::

   * Currently the benchmark applications in **application/baremetal/benchmark** used this optimization

.. _develop_buildsystem_var_gdb_port:

GDB_PORT
~~~~~~~~

.. note::

    * This new variable **GDB_PORT** is added in Nuclei SDK since version ``0.2.4``

This variable is not used usually, by default the **GDB_PORT** variable is ``3333``.

If you want to change a debug gdb port for openocd and gdb when run ``run_openocd`` and
``run_gdb`` target, you can pass a new port such as ``3344`` to this variable.

For example, if you want to debug application using run_openocd and
run_gdb and specify a different port other than ``3333``.

You can do it like this, take ``nuclei_fpga_eval`` board for example, such as port ``3344``:

* Open openocd server: ``make SOC=demosoc BOARD=nuclei_fpga_eval CORE=n307 GDB_PORT=3344 run_openocd``

* connect gdb with openocd server: ``make SOC=demosoc BOARD=nuclei_fpga_eval CORE=n307 GDB_PORT=3344 run_gdb``

.. _develop_buildsystem_var_banner:

BANNER
~~~~~~

If **BANNER=0**, when program is rebuilt, then the banner message print in console will not be print,
banner print is default enabled via ``NUCLEI_BANNER=1`` in ``nuclei_sdk_hal.h``.

when ``BANNER=0``, an macro ``-DNUCLEI_BANNER=0`` will be passed in Makefile.

The banner message looks like this:

.. code-block:: c

    Nuclei SDK Build Time: Jul 23 2021, 10:22:50
    Download Mode: ILM
    CPU Frequency 15999959 Hz


.. _develop_buildsystem_var_v:

V
~

If **V=1**, it will display compiling message in verbose including compiling options.

By default, no compiling options will be displayed in make console message just to print
less message and make the console message cleaner. If you want to see what compiling option
is used, please pass **V=1** in your make command.

.. _develop_buildsystem_var_silent:

SILENT
~~~~~~

If **SILENT=1**, it will not display any compiling messsage.

If you don't want to see any compiling message, you can pass **SILENT=1** in your make command.

.. _develop_buildsystem_app_make_vars:

Makefile variables used only in Application Makefile
----------------------------------------------------

The following variables should be used in application Makefile at your demand,
e.g. ``application/baremetal/demo_timer/Makefile``.

* :ref:`develop_buildsystem_var_target`
* :ref:`develop_buildsystem_var_nuclei_sdk_root`
* :ref:`develop_buildsystem_var_middleware`
* :ref:`develop_buildsystem_var_rtos`
* :ref:`develop_buildsystem_var_stdclib`
* :ref:`develop_buildsystem_var_nmsis_lib`
* :ref:`develop_buildsystem_var_riscv_arch`
* :ref:`develop_buildsystem_var_riscv_abi`
* :ref:`develop_buildsystem_var_riscv_cmodel`
* :ref:`develop_buildsystem_var_riscv_tune`
* :ref:`develop_buildsystem_var_nogc`
* :ref:`develop_buildsystem_var_rtthread_msh`

.. _develop_buildsystem_var_target:

TARGET
~~~~~~

This is a necessary variable which must be defined in application Makefile.

It is used to set the name of the application, it will affect the generated
target filenames.

.. warning::

    * Please don't put any spaces in TARGET variable
    * The variable shouldn't contain any space

    .. code-block:: Makefile

        # invalid case 1
        TARGET ?= hello world
        # invalid case 2
        TARGET ?= helloworld # before this # there is a extra space


.. _develop_buildsystem_var_nuclei_sdk_root:

NUCLEI_SDK_ROOT
~~~~~~~~~~~~~~~

This is a necessary variable which must be defined in application Makefile.

It is used to set the path of Nuclei SDK Root, usually it should be set as
relative path, but you can also set absolute path to point to Nuclei SDK.

.. _develop_buildsystem_var_rtos:

RTOS
~~~~

**RTOS** variable is used to choose which RTOS will be used in this application.

You can easily find the supported RTOSes in the **<NUCLEI_SDK_ROOT>/OS** directory.

* If **RTOS** is not defined, then baremetal service will be enabled with this application.
  See examples in ``application/baremetal``.
* If **RTOS** is set the the following values, RTOS service will be enabled with this application.

  - ``FreeRTOS``: FreeRTOS service will be enabled, extra macro ``RTOS_FREERTOS`` will be defined,
    you can include FreeRTOS header files now, and use FreeRTOS API, for ``FreeRTOS`` application,
    you need to have an ``FreeRTOSConfig.h`` header file prepared in you application.
    See examples in ``application/freertos``.
  - ``UCOSII``: UCOSII service will be enabled, extra macro ``RTOS_UCOSII`` will be defined,
    you can include UCOSII header files now, and use UCOSII API, for ``UCOSII`` application,
    you need to have ``app_cfg.h``, ``os_cfg.h`` and ``app_hooks.c`` files prepared in you application.
    See examples in ``application/ucosii``.
  - ``RTThread``: RT-Thread service will be enabled, extra macro ``RTOS_RTTHREAD`` will be defined,
    you can include RT-Thread header files now, and use RT-Thread API, for ``UCOSII`` application,
    you need to have an ``rtconfig.h`` header file prepared in you application.
    See examples in ``application/rtthread``.

.. _develop_buildsystem_var_middleware:

MIDDLEWARE
~~~~~~~~~~

**MIDDLEWARE** variable is used to select which middlewares should be used in this application.

You can easily find the available middleware components in the **<NUCLEI_SDK_ROOT>/Components** directory.

* If **MIDDLEWARE** is not defined, not leave empty, no middlware package will be selected.
* If **MIDDLEWARE** is defined with more than 1 string, such as ``fatfs tjpgd``, then these two
  middlewares will be selected.

.. _develop_buildsystem_var_nmsis_lib:

NMSIS_LIB
~~~~~~~~~

**NMSIS_LIB** variable is used to select which NMSIS libraries should be used in this application.

Currently you can select the following libraries:

* **nmsis_dsp**: NMSIS DSP prebuilt library.
* **nmsis_nn**: NMSIS NN prebuilt library.

You can select more than libraries of NMSIS. For example, if you want to use NMSIS NN library,
NMSIS DSP library is also required. so you need to set **NMSIS_LIB** like this ``NMSIS_LIB := nmsis_nn nmsis_dsp``

.. _develop_buildsystem_var_stdclib:

STDCLIB
~~~~~~~

**STDCLIB** variable is used to select which standard c runtime library will be used.
If not defined, the default value will be ``newlib_small``.

In Nuclei GNU Toolchain, we destributed newlib/newlib-nano/Nuclei c runtime library,
so user can select different c runtime library according to their requirement.

Newlib is a simple ANSI C library, math library, available for both RV32 and RV64.

Nuclei C runtime library is a highly optimized c library designed for deeply embedded user cases,
can provided smaller code size and highly optimized floating point support compared to Newlib.

.. list-table:: Available STDCLIB choices
   :widths: 10 70
   :header-rows: 1
   :align: center

   * - **STDCLIB**
     - Description
   * - newlib_full
     - | Normal version of newlib, optimized for speed at cost of size.
       | It provided full feature of newlib, with file io supported.
   * - newlib_fast
     - Newlib nano version, with printf float and scanf float support.
   * - newlib_small
     - Newlib nano version, with printf float support.
   * - newlib_nano
     - Newlib nano version, without printf/scanf float support.
   * - libncrt_fast
     - Nuclei C runtime library optimized for speed, full feature
   * - libncrt_balanced
     - Nuclei C runtime library balanced at speed and code size, full feature
   * - libncrt_small
     - Nuclei C runtime library optimized for code size, full feature
   * - libncrt_nano
     - Nuclei C runtime library optimized for code size, without float/double support
   * - libncrt_pico
     - Nuclei C runtime library optimized for code size, without long/long long/float/double support
   * - nostd
     - no std c library will be used, and don't search the standard system directories for header files
   * - nospec
     - no std c library will be used, not pass any --specs options

.. note::

    * About Newlib and Newlib nano difference, please check
      https://github.com/riscv-collab/riscv-newlib/blob/riscv-newlib-3.2.0/newlib/README
    * About Nuclei C runtime library, it didn't provided all the features that
      newlib can do, it is highly optimized for deeply embedded scenery
    * Nuclei C runtime library is only available in Nuclei GNU Toolchain released after Nov 2021.
    * Since there are different c runtime library can be chosen now, so developer
      need to provide different stub functions for different library, please check
      ``SoC/demosoc/Common/Source/Stubs/`` and ``SoC/demosoc/build.mk`` for example.

.. _develop_buildsystem_var_smp:

SMP
~~~

**SMP** variable is used to control smp cpu core count, valid number must > 1.

When **SMP** variable is defined, extra gcc options for ld is passed
``-Wl,--defsym=__SMP_CPU_CNT=$(SMP)``, and extra c macro ``-DSMP_CPU_CNT=$(SMP)``
is defined this is passed in each SoC's build.mk, such as ``SoC/demosoc/build.mk``.

And for demosoc, we use a different openocd configuration file for SMP named
``SoC/demosoc/Board/nuclei_fpga_eval/openocd_demosoc_smp.cfg``.

When SMP variable is defined, extra openocd command ``set SMP $(SMP)`` will also
be passed when run openocd upload or create a openocd server.

.. _develop_buildsystem_var_stacksz:

STACKSZ
~~~~~~~

**STACKSZ** variable is used to control the per core stack size reserved in linker script,
this need to cooperate with link script file and linker options.

In link script file, ``__STACK_SIZE`` symbol need to use ``PROVIDE`` feature of ld
to define a weak version, such as ``PROVIDE(__STACK_SIZE = 2K);``, and gcc will pass
ld options ``-Wl,--defsym=__STACK_SIZE=$(STACKSZ)`` to overwrite the default value if
**STACKSZ** is defined.

**STACKSZ** variable must be a valid value accepted by ld, such as 0x2000, 2K, 4K, 8192.

For SMP version, stack size space need to reserve **STACKSZ** x SMP Core Count size.

You can refer to ``SoC/demosoc/Board/nuclei_fpga_eval/Source/GCC/gcc_demosoc_ilm.ld`` for smp version.

.. _develop_buildsystem_var_heapsz:

HEAPSZ
~~~~~~

**HEAPSZ** variable is used to control the heap size reserved in linker script,
this need to cooperate with link script file and linker options.

In link script file, ``__HEAP_SIZE`` symbol need to use ``PROVIDE`` feature of ld
to define a weak version, such as ``PROVIDE(__HEAP_SIZE = 2K);``, and gcc will pass
ld options ``-Wl,--defsym=__HEAP_SIZE=$(HEAPSZ)`` to overwrite the default value if
**HEAPSZ** is defined.

**HEAPSZ** variable must be a valid value accepted by ld, such as 0x2000, 2K, 4K, 8192.

.. _develop_buildsystem_var_riscv_arch:

RISCV_ARCH
~~~~~~~~~~

**RISCV_ARCH** variable is used to control compiler option ``-mcmodel=$(RISCV_ARCH)``.

It might override RISCV_ARCH defined in SoC build.mk, according to your build.mk implementation.

**RISCV_ARCH** might directly affect the gcc compiler option depended on the implementation of SoC build.mk.

Take ``SOC=demosoc`` for example.

* **CORE=n305 RISCV_ARCH=rv32imafdcp RISCV_ABI=ilp32d ARCH_EXT=bp**, then final compiler options will be
  ``-march=rv32imafdcp -mabi=ilp32d -mtune=nuclei-300-series``. The **ARCH_EXT** is ignored.

.. _develop_buildsystem_var_riscv_abi:

RISCV_ABI
~~~~~~~~~

**RISCV_ABI** variable is used to control compiler option ``-mcmodel=$(RISCV_ABI)``.

It might override RISCV_ABI defined in SoC build.mk, according to your build.mk implementation.

.. _develop_buildsystem_var_riscv_cmodel:

RISCV_CMODEL
~~~~~~~~~~~~

**RISCV_CMODEL** is used to control compiler option ``-mcmodel=$(RISCV_CMODEL)``.

For RV32, default value is ``medlow``, otherwise ``medany`` for RV64.

You can set ``RISCV_CMODEL`` to override predefined value.

.. _develop_buildsystem_var_riscv_tune:

RISCV_TUNE
~~~~~~~~~~

**RISCV_TUNE** is used to control compiler option ``-mtune=$(RISCV_TUNE)``.

It is defined in SoC build.mk, you can override it if your implementation
allow it.

.. _develop_buildsystem_var_pfloat:

PFLOAT
~~~~~~

.. note::

    * **Deprecated** variable, please use :ref:`develop_buildsystem_var_stdclib` now
    * ``NEWLIB=nano PFLOAT=1`` can be replaced by ``STDCLIB=newlib_small`` now

.. _develop_buildsystem_var_newlib:

NEWLIB
~~~~~~

.. note::

    * **Deprecated** variable, please use :ref:`develop_buildsystem_var_stdclib` now

.. _develop_buildsystem_var_nogc:

NOGC
~~~~

**NOGC** variable is used to control whether to enable gc sections to reduce program
code size or not, by default GC is enabled to reduce code size.

When GC is enabled, these options will be added:

* Adding to compiler options: ``-ffunction-sections -fdata-sections``
* Adding to linker options: ``-Wl,--gc-sections -Wl,--check-sections``

If you want to enable this GC feature, you can set **NOGC=0** (default), GC feature will
remove sections for you, but sometimes it might remove sections that are useful,
e.g. For Nuclei SDK test cases, we use ctest framework, and we need to set **NOGC=1**
to disable GC feature.

When ``NOGC=0``(default), extra compile options ``-ffunction-sections -fdata-sections``,
and extra link options ``-Wl,--gc-sections -Wl,--check-sections`` will be passed.

.. _develop_buildsystem_var_rtthread_msh:

RTTHREAD_MSH
~~~~~~~~~~~~

**RTTHREAD_MSH** variable is valid only when **RTOS** is set to **RTThread**.

When **RTTHREAD_MSH** is set to **1**:

* The RTThread MSH component source code will be included
* The MSH thread will be enabled in the background
* Currently the msh getchar implementation is using a weak function implemented
  in ``rt_hw_console_getchar`` in ``OS/RTTThread/libcpu/risc-v/nuclei/cpuport.c``

.. _develop_buildsystem_app_build_vars:

Build Related Makefile variables used only in Application Makefile
------------------------------------------------------------------

If you want to specify additional compiler flags, please follow this guidance
to modify your application Makefile.

Nuclei SDK build system defined the following variables to control the
build options or flags.

* :ref:`develop_buildsystem_var_incdirs`
* :ref:`develop_buildsystem_var_c_incdirs`
* :ref:`develop_buildsystem_var_cxx_incdirs`
* :ref:`develop_buildsystem_var_asm_incdirs`
* :ref:`develop_buildsystem_var_srcdirs`
* :ref:`develop_buildsystem_var_c_srcdirs`
* :ref:`develop_buildsystem_var_cxx_srcdirs`
* :ref:`develop_buildsystem_var_asm_srcdirs`
* :ref:`develop_buildsystem_var_c_srcs`
* :ref:`develop_buildsystem_var_cxx_srcs`
* :ref:`develop_buildsystem_var_asm_srcs`
* :ref:`develop_buildsystem_var_exclude_srcs`
* :ref:`develop_buildsystem_var_common_flags`
* :ref:`develop_buildsystem_var_cflags`
* :ref:`develop_buildsystem_var_cxxflags`
* :ref:`develop_buildsystem_var_asmflags`
* :ref:`develop_buildsystem_var_ldflags`
* :ref:`develop_buildsystem_var_ldlibs`
* :ref:`develop_buildsystem_var_libdirs`
* :ref:`develop_buildsystem_var_linker_script`

.. _develop_buildsystem_var_incdirs:

INCDIRS
~~~~~~~

This **INCDIRS** is used to pass C/CPP/ASM include directories.

e.g. To include current directory ``.`` and ``inc`` for C/CPP/ASM

.. code-block:: makefile

    INCDIRS = . inc


.. _develop_buildsystem_var_c_incdirs:

C_INCDIRS
~~~~~~~~~

This **C_INCDIRS** is used to pass C only include directories.

e.g. To include current directory ``.`` and ``cinc`` for C only

.. code-block:: makefile

    C_INCDIRS = . cinc


.. _develop_buildsystem_var_cxx_incdirs:

CXX_INCDIRS
~~~~~~~~~~~

This **CXX_INCDIRS** is used to pass CPP only include directories.

e.g. To include current directory ``.`` and ``cppinc`` for CPP only

.. code-block:: makefile

    CXX_INCDIRS = . cppinc


.. _develop_buildsystem_var_asm_incdirs:

ASM_INCDIRS
~~~~~~~~~~~

This **ASM_INCDIRS** is used to pass ASM only include directories.

e.g. To include current directory ``.`` and ``asminc`` for ASM only

.. code-block:: makefile

    ASM_INCDIRS = . asminc


.. _develop_buildsystem_var_srcdirs:

SRCDIRS
~~~~~~~

This **SRCDIRS** is used to set the source directories used to search
the C/CPP/ASM source code files, it will not do recursively.

e.g. To search C/CPP/ASM source files in directory ``.`` and ``src``

.. code-block:: makefile

    SRCDIRS = . src


.. _develop_buildsystem_var_c_srcdirs:

C_SRCDIRS
~~~~~~~~~

This **C_SRCDIRS** is used to set the source directories used to search
the C only source code files(*.c, *.C), it will not do recursively.

e.g. To search C only source files in directory ``.`` and ``csrc``

.. code-block:: makefile

    C_SRCDIRS = . csrc


.. _develop_buildsystem_var_cxx_srcdirs:

CXX_SRCDIRS
~~~~~~~~~~~

This **CXX_SRCDIRS** is used to set the source directories used to search
the CPP only source code files(*.cpp, *.CPP), it will not do recursively.

e.g. To search CPP only source files in directory ``.`` and ``cppsrc``

.. code-block:: makefile

    CXX_SRCDIRS = . cppsrc


.. _develop_buildsystem_var_asm_srcdirs:

ASM_SRCDIRS
~~~~~~~~~~~

This **ASM_SRCDIRS** is used to set the source directories used to search
the ASM only source code files(*.s, *.S), it will not do recursively.

e.g. To search ASM only source files in directory ``.`` and ``asmsrc``

.. code-block:: makefile

    ASM_SRCDIRS = . asmsrc


.. _develop_buildsystem_var_c_srcs:

C_SRCS
~~~~~~

If you just want to include a few of C source files in directories, you can use this
**C_SRCS** variable, makefile wildcard pattern supported.

e.g. To include ``main.c`` and ``src/hello.c``

.. code-block:: makefile

    C_SRCS = main.c src/hello.c

.. _develop_buildsystem_var_cxx_srcs:

CXX_SRCS
~~~~~~~~

If you just want to include a few of CPP source files in directories, you can use this
**CXX_SRCS** variable, makefile wildcard pattern supported.

e.g. To include ``main.cpp`` and ``src/hello.cpp``

.. code-block:: makefile

    CXX_SRCS = main.cpp src/hello.cpp


.. _develop_buildsystem_var_asm_srcs:

ASM_SRCS
~~~~~~~~

If you just want to include a few of ASM source files in directories, you can use this
**ASM_SRCS** variable, makefile wildcard pattern supported.

e.g. To include ``asm.s`` and ``src/test.s``

.. code-block:: makefile

    ASM_SRCS = asm.s src/test.s

.. _develop_buildsystem_var_exclude_srcs:

EXCLUDE_SRCS
~~~~~~~~~~~~

If you just want to exclude a few of c/asm/cpp source files in directories,
you can use this **EXCLUDE_SRCS** variable, makefile wildcard pattern supported.

e.g. To exclude ``test2.c`` and ``src/test3.c``

.. code-block:: makefile

    EXCLUDE_SRCS = test2.c src/test3.c

.. _develop_buildsystem_var_common_flags:

COMMON_FLAGS
~~~~~~~~~~~~

This **COMMON_FLAGS** variable is used to define common compiler flags to all c/asm/cpp compiler.

For example, you can add a newline ``COMMON_FLAGS += -O3 -funroll-loops -fpeel-loops``
in your application Makefile and these options will be passed to C/ASM/CPP compiler.


.. _develop_buildsystem_var_cflags:

CFLAGS
~~~~~~

Different to **COMMON_FLAGS**, this **CFLAGS** variable is used to define common compiler flags to C compiler only.

For example, you can add a newline ``CFLAGS += -O3 -funroll-loops -fpeel-loops``
in your application Makefile and these options will be passed to C compiler.

.. _develop_buildsystem_var_cxxflags:

CXXFLAGS
~~~~~~~~

Different to **COMMON_FLAGS**, this **CXXFLAGS** variable is used to define common compiler flags to cpp compiler only.

For example, you can add a newline ``CXXFLAGS += -O3 -funroll-loops -fpeel-loops``
in your application Makefile and these options will be passed to cpp compiler.

.. _develop_buildsystem_var_asmflags:

ASMFLAGS
~~~~~~~~

Different to **COMMON_FLAGS**, this **ASMFLAGS** variable is used to define common compiler flags to asm compiler only.

For example, you can add a newline ``ASMFLAGS += -O3 -funroll-loops -fpeel-loops``
in your application Makefile and these options will be passed to asm compiler.

.. _develop_buildsystem_var_ldflags:

LDFLAGS
~~~~~~~

This **LDFLAGS** is used to pass extra linker flags, for example,
if you want to link extra math library, you can add a newline
``LDFLAGS += -lm`` in you application Makefile.

Libraries (-lfoo) could also be added to the LDLIBS variable instead.

.. _develop_buildsystem_var_ldlibs:

LDLIBS
~~~~~~

This **LDLIBS** variable is library flags or names given to compilers
when they are supposed to invoke the linker.

Non-library linker flags, such as -L, should go in the **LDFLAGS** variable.

.. _develop_buildsystem_var_libdirs:

LIBDIRS
~~~~~~~

This **LIBDIRS** variable is used to store the library directories, which could
be used together with **LDLIBS**.

For example, if you have a library located in **$(NUCLEI_SDK_ROOT)/Library/DSP/libnmsis_dsp_rv32imac.a**,
and you want to link it, then you can define these lines:

.. code-block:: makefile

   LDLIBS = -lnmsis_dsp_rv32imac
   LIBDIRS = $(NUCLEI_SDK_ROOT)/Library/DSP

.. _develop_buildsystem_var_linker_script:

LINKER_SCRIPT
~~~~~~~~~~~~~

This **LINKER_SCRIPT** variable could be used to set the link script of the application.

By default, there is no need to set this variable, since the build system will define
a default linker script for application according to the build configuration. If you want
to define your own linker script, you can set this variable.

For example, ``LINKER_SCRIPT := gcc.ld``.


.. _GNU Make Standard Library (GMSL): http://sourceforge.net/projects/gmsl/