TamaGo - bare metal Go for ARM SoCs - MCIMX6ULL-EVK support

tamago | https://github.com/f-secure-foundry/tamago

Copyright (c) F-Secure Corporation
https://foundry.f-secure.com

Authors

Andrea Barisani
andrea.barisani@f-secure.com | andrea@inversepath.com

Andrej Rosano
andrej.rosano@f-secure.com | andrej@inversepath.com

Introduction

TamaGo is a framework that enables compilation and execution of unencumbered Go applications on bare metal ARM System-on-Chip (SoC) components.

The mx6ullevk package provides support for the MCIMX6ULL-EVK development board.

Documentation

For more information about TamaGo see its repository and project wiki.

For the underlying driver support for this board see package imx6.

The package API documentation can be found on pkg.go.dev.

Supported hardware

SoC	Board	SoC package	Board package
NXP i.MX6ULL	MCIMX6ULL-EVK	imx6	mx6ullevk

Compiling

Go applications are simply required to import, the relevant board package to ensure that hardware initialization and runtime support takes place:

import (
	_ "github.com/f-secure-foundry/tamago/board/nxp/mx6ullevk"
)

Build the TamaGo compiler (or use the latest binary release):

git clone https://github.com/f-secure-foundry/tamago-go -b latest
cd tamago-go/src && ./all.bash
cd ../bin && export TAMAGO=`pwd`/go

Go applications can be compiled as usual, using the compiler built in the previous step, but with the addition of the following flags/variables and ensuring that the required SoC and board packages are available in GOPATH:

GO_EXTLINK_ENABLED=0 CGO_ENABLED=0 GOOS=tamago GOARM=7 GOARCH=arm \
  ${TAMAGO} build -ldflags "-T 0x80010000  -E _rt0_arm_tamago -R 0x1000"

An example application, targeting the MCIMX6ULL-EVK platform, is available.

Executing and debugging

The example application provides reference usage and a Makefile target for automatic creation of an ELF as well as imx image for flashing.

Native hardware: imx image on microSD

Copy the built imx image to a microSD as follows:

sudo dd if=<path to imx file> of=/dev/sdX bs=1M conv=fsync

IMPORTANT: /dev/sdX must be replaced with your microSD device (not eventual microSD partitions), ensure that you are specifying the correct one. Errors in target specification will result in disk corruption.

Ensure the SW601 boot switches on the processor board are set to microSD boot mode:

switch	position
1	OFF
2	OFF
3	ON
4	OFF

Native hardware: existing bootloader

Copy the built ELF binary on an external microSD card then launch it from the U-Boot console as follows:

ext2load mmc 1:1 0x90000000 example
bootelf -p 0x90000000

For non-interactive execution modify the U-Boot configuration accordingly.

Standard output

The standard output can be accessed through the debug console found on micro USB connector J1901 and the following picocom configuration:

picocom -b 115200 -eb /dev/ttyUSB0 --imap lfcrlf

Debugging

The application can be debugged with GDB over JTAG using openocd and the imx6ull.cfg and gdbinit debugging helpers published here.

# start openocd daemon
openocd -f interface/ftdi/jtagkey.cfg -f imx6ull.cfg

# connect to the OpenOCD command line
telnet localhost 4444

# debug with GDB
arm-none-eabi-gdb -x gdbinit example

Hardware breakpoints can be set in the usual way:

hb ecdsa.Verify
continue

QEMU

The target can be executed under emulation as follows:

qemu-system-arm \
	-machine mcimx6ul-evk -cpu cortex-a7 -m 512M
	\ -nographic -monitor none -serial null -serial stdio -net none
	\ -kernel example -semihosting -d unimp

The emulated target can be debugged with GDB by adding the -S -s flags to the previous execution command, this will make qemu waiting for a GDB connection that can be launched as follows:

arm-none-eabi-gdb -ex "target remote 127.0.0.1:1234" example

Breakpoints can be set in the usual way:

b ecdsa.Verify
continue

License

tamago | https://github.com/f-secure-foundry/tamago
Copyright (c) F-Secure Corporation

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation under version 3 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

See accompanying LICENSE file for full details.