Build System based on Makefile

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

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:

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:

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 Makefile variables passed by make command to learn more.

This file will include optional Makefile.global and Makefile.local which allow user to set custom global Makefile configurations and local application Makefile configurations.

This file will include the following makefiles:

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.

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.

Makefile.conf

This Makefile.conf file will define the following items:

  • Toolchain related variables used during compiling

  • Debug related variables

  • Include Makefile.files and Makefile.rtos

  • Collect all the C/C++/ASM compiling and link options

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

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

Makefile.soc

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

It will define the following items:

  • DOWNLOAD and CORE variables

  • 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:

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

Makefile.rtos

This Makefile.rtos will include <NUCLEI_SDK_ROOT>/OS/<RTOS>/build.mk according to our RTOS variable.

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

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

If no 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.

Makefile.components

This Makefile.components will include build.mk Makefiles of selected components defined via makefile variable 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 :

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.

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.

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 GD32VF103V RV-STAR Kit, you can create the <NUCLEI_SDK_ROOT>/Build/Makefile.global as below:

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 GD32VF103V RV-STAR Kit board, e.g.

  • The GD32VF103V RV-STAR Kit 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

Makefile.local

As the 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 GD32VF103V RV-STAR Kit, you can create application/baremetal/helloworld/Makefile.local as below:

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.

Makefile targets of make command

Here is a list of the Make targets supported by Nuclei SDK Build System.

Make targets supported by Nuclei SDK Build System

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 Makefile variables passed by make command

  • For run_openocd and run_gdb target, if you want to change a new gdb port, you can pass the variable 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.

Makefile variables passed by make command

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

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.

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 Supported SoCs.

Supported SoCs

SOC

Reference

gd32vf103

GD32VF103 SoC

demosoc

Nuclei Demo SoC

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.

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.

Currently we support the following SoCs.

Supported Boards when SOC=gd32vf103

BOARD

Reference

gd32vf103v_rvstar

GD32VF103V RV-STAR Kit

gd32vf103v_eval

GD32VF103V Evaluation Kit

gd32vf103c_longan_nano

Sipeed Longan Nano

gd32vf103c_t_display

Sipeed Longan Nano

Supported Boards when SOC=demosoc

BOARD

Reference

nuclei_fpga_eval

Nuclei FPGA Evaluation Kit

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.

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.

DOWNLOAD

DOWNLOAD variable is used to declare the download mode of the application, currently it has these modes supported as described in table Supported download modes

Supported download modes

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

  • GD32VF103 SoC only support DOWNLOAD=flashxip

  • Nuclei Demo SoC support all the download modes.

  • flashxip mode in Nuclei Demo SoC 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.

CORE

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

Currently it has these cores supported as described in table Supported Nuclei Processor cores.

Supported Nuclei Processor cores

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 ARCH_EXT 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.

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:

# 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))

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

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

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.

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.

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.

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

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

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.

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.

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.

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

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.

Available STDCLIB choices

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.

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.

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.

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.

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.

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.

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.

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.

PFLOAT

Note

  • Deprecated variable, please use STDCLIB now

  • NEWLIB=nano PFLOAT=1 can be replaced by STDCLIB=newlib_small now

NEWLIB

Note

  • Deprecated variable, please use STDCLIB now

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.

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