TamaGo - bare metal Go - QEMU sifive_u support

tamago | https://github.com/usbarmory/tamago

Copyright (c) WithSecure Corporation

Authors

Andrea Barisani
[email protected]

Andrej Rosano
[email protected]

Introduction

TamaGo is a framework that enables compilation and execution of unencumbered Go applications on bare metal AMD64/ARM/RISC-V processors.

The sifive_u package provides support for the QEMU sifive_u emulated machine configured with a single U54 core.

Documentation

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

For the underlying driver support for this board see package fu540.

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

Supported hardware

SoC	Board	SoC package	Board package
SiFive FU540	QEMU sifive_u	fu540	qemu/sifive_u

Compiling

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

import (
	_ "github.com/usbarmory/tamago/board/qemu/sifive_u"
)

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

wget https://github.com/usbarmory/tamago-go/archive/refs/tags/latest.zip
unzip latest.zip
cd tamago-go-latest/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:

GOOS=tamago GOARCH=riscv64 ${TAMAGO} build -ldflags "-T 0x80010000 -R 0x1000" main.go

An example application, targeting the QEMU sifive_u platform, is available.

Build tags

The following build tags allow application to override the package own definition of external functions required by the runtime:

• linkramsize: exclude ramSize from mem.go
• linkprintk: exclude printk from console.go

Executing and debugging

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

QEMU

The target can be executed under emulation as follows:

dtc -I dts -O dtb qemu-riscv64-sifive_u.dts -o qemu-riscv54-sifive_u.dtb

qemu-system-riscv64 \
	-machine sifive_u -m 512M \
	-nographic -monitor none -serial stdio -net none \
	-dtb qemu-riscv64-sifive_u.dtb \
	-bios bios.bin

At this time a bios is required to jump to the correct entry point of the ELF image, the example application includes a minimal bios which is configured and compiled for all riscv64 qemu targets.

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:

riscv64-elf-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/usbarmory/tamago
Copyright (c) WithSecure Corporation

These source files are distributed under the BSD-style license found in the LICENSE file.

The TamaGo logo is adapted from the Go gopher designed by Renee French and licensed under the Creative Commons 3.0 Attributions license. Go Gopher vector illustration by Hugo Arganda.