Support mkfs.simplefs on macOS #78
Description
This PR enables loading simplefs.ko in the guest OS to mount simplefs. The CI of the rv32emu supports both Linux and macOS runners, supports both Linux and macOS runners; however, the macOS runner cannot execute the simplefs test cases because mkfs.simplefs is not compilable on macOS.
The reason is that mkfs.simplefs include the platform-specific (<linux/fs.h>) header here, which is unavailable on macOS. The main API used from this header is the ioctl call with the BLKGETSIZE64 operation to obtain the block device size. On macOS, it does supports similar API, refer to initialization of the virtio-block of rv32emu here and here to get the block device size.
Once macOS platform is supported, the rv32emu CI will be extended to include testing the guest OS with simplefs.ko loaded on the macOS platform.