RISC-V Programming

What is a RISC-V Toolchain?

The riscv64-unknown-elf-xxx toolchain is specifically designed for the RISC-V instruction set architecture (ISA), and it’s used for developing bare-metal and applications for running on RISC-V targets. This toolchain typically runs on the host machine (e.g., an x86-based PC) to produce code that will run on a RISC-V machine (e.g., a RISC-V based SoC). This process is known as cross-compilation.

Breaking down the name riscv64-unknown-elf-xxx:

riscv64: This refers to the RISC-V architecture with a 64-bit address space. RISC-V is an open-standard ISA that’s been gaining traction in both academia and industry due to its flexibility and modularity.

unknown: This indicates that the toolchain is not tied to a specific vendor or platform. It’s a generic term used to describe that the toolchain can be used across different RISC-V implementations.

elf: Stands for Executable and Linkable Format. It’s the format used for the compiled binaries. ELF is a common binary file format that’s used on many Unix systems, including Linux.

xxx: Typically, this would be replaced by specific tools within the toolchain, like:

• gcc: The GNU Compiler Collection for RISC-V, also known as the compiler.

• gdb: The GNU Debugger for debugging RISC-V applications, used for debugging programs.

• ld: The linker.

• objdump: A utility that displays information about object files.

• … and so on

What is OpenOCD?

OpenOCD, which stands for Open On-Chip Debugger, is a free, open-source software that provides debugging, in-system programming, and boundary-scan testing for embedded systems. It’s used to program and debug embedded systems using JTAG or SWD (Serial Wire Debug) interfaces.

Main functionalities

Debugging: Through OpenOCD, developers can control the JTAG state machine to run a program on an embedded target, halt the target at a breakpoint, and then inspect or modify variables to debug the software.

Flashing: OpenOCD can be used to load program (also called “flash”) onto either internal or external Flash memory of the SoC.

Remote Debugging: OpenOCD can function as a GDB (GNU Debugger) server. This means developers can use GDB or a GDB-compatible front-end to remotely debug an application running on an embedded target through OpenOCD.

Scriptable Interface: OpenOCD provides a flexible and scriptable interface, which is valuable for automated testing and custom debugging routines.

Setting up RISC-V Environment

In this tutorial, we will set up the RISC-V environment by installing the necessary toolchains and other software.

pageSetting up RISC-V Toolchain