Documentation/Platforms/OpenRISC

Description

OpenRISC is an open source processor architecture. While instruction sets like x86 are proprietary and owned by a single company, OpenRISC is free. Its main use is as a processor on embedded systems.

Build Directions

 ./configure --target-list='or1k-softmmu or1k-linux-user' && make

Full system emulation

To boot linux you can run the following. If you are starting out you can download the OpenRISC test image from Testing/System_Images. The test image may be gzipped, so be sure to gunzip it first.

 qemu-system-or1k -cpu or1200 -M or1k-sim -kernel $LINUX/vmlinux -serial stdio -nographic -monitor none

For networking support you can add the following options, note the open_eth option uses the kernel's ethoc Ethernet driver.

 -device open_eth -netdev tap,id=or1k

User mode emulation

Using QEMU user mode emulation we can run and debug OpenRISC binaries on your host linux.

 $ cat main.c
 #include <stdio.h>
 int main() {
    printf ("hello\n");
    return 0;
 }
 $ or1k-linux-musl-gcc main.c
 # Here $LDPATH/lib/ld-musl-or1k.so.1 is linked to or1k-linux-musl/lib/libc.so
 $ qemu-or1k -L $LDPATH ./a.out 
 hello

Debugging Tips

For debugging QEMU can listen on a gdb stub port with the below options. Note, you can also use -S with the -gdb option to have QEMU wait for a gdb client connection before starting the boot process.

 -gdb tcp::10001

To get good traces you can also add the following, this will output trace info to the file trace.txt

 -D trace.txt -d in_asm,exec,int,op_opt

Pictures

Links

• Video introducing OpenRISC
• The OpenRISC project site
• OpenRISC 1000 specification
• GCC toolchain releases and binaries

Contacts

Maintainer: Stafford Horne