Cartesi's reference off-chain implementation of Cartesi Machines is based on software emulation. The emulator is written in C/C++ with POSIX dependencies restricted to the terminal, process, and memory-mapping facilities. It is written as a C++ library, but can be accessed in a variety of different ways.
When linked to a C++ application, the emulator can be controlled directly via the interface of the
The emulator can also be accessed from the Lua programming language, via a
cartesi module that exposes a
cartesi.machine interface to Lua programs, mirroring the C++ interface.
Additionally, Cartesi provides a gRPC server that can be run to control a Cartesi Machine instance remotely.
This server exposes a higher-level interface better suited for the verification process, including the ability to create in-memory snapshots of the current machine state so that later modifications can be rolled back.
Finally, there is a command-line utility (written in Lua) that can configure and run Cartesi Machines for rapid prototyping.
emulator/ directory in the Emulator SDK can be used to build and install the Cartesi Machine emulator.
The emulator can then be used via any of these methods.
The documentation starts from the command-line utility,
This utility is used for most prototyping tasks.
The documentation then covers the Lua interface of
The C++ interface is very similar, and is covered only within its reference manual.
The same is true of the gRPC interface, used to control an emulator remotely.
Cartesi Machines are separated into a processor and a board. The processor performs the computations, executing the traditional fetch-execute loop while maintaining a variety of registers. The board defines the surrounding environment with an assortment of memories (ROM, RAM, flash drives) and a number of devices. Memories and devices are mapped to the 64-bit physical address space of the Cartesi Machine. The amount of RAM, as well as the number, length, and position of the flash drives in the address space can be chosen according to the needs of each particular application.
In a typical scenario, a Cartesi Machine is initialized and then run until it halts.
At a minimum, the initialization process loads a ROM image, a RAM image, and a root file-system (as a flash drive) from regular files in the host file-system.
Execution starts from the ROM image, which contains a simple program that creates a description of the machine organization for the Linux kernel.
The ROM image
rom.bin can be built in the
rom/ directory in the Emulator SDK.
The Linux kernel itself resides in the RAM image
linux.bin, built in the
kernel/ directory in the Emulator SDK.
After it is done with its own initialization, the Linux kernel cedes control to the
/sbin/init program in the root file-system.
The root file-system
rootfs.ext2 contains all the data files and programs that make up an embedded Linux distribution.
It can be built in the
fs/ directory in the Emulator SDK.
The DApp components can reside in the root file-system itself, or in their own, separate file-system.
Additional flash drives can be used as the DApp input and output, either containing file-systems or containing raw data.
The emulator can be instructed to execute whatever computation the DApp wishes to perform inside the Cartesi Machine.
For a complete description of the Cartesi Machine architecture and the boot process, see the documentation for the target perspective.
The setup of a new development environment is often a time-consuming task.
This is particularly true in case of cross-development environments (i.e., when the development happens in a host platform but software runs in a different target platform).
With this in mind, the Cartesi team provides the
cartesi/playground Docker image, which enables immediate experimentation with Cartesi Machines.
This comes with a pre-built emulator and Lua interpreter accessible within the command-line, as well as a pre-built ROM image, RAM image, and root file-system.
It also comes with the cross-compiler for the RISC-V architecture on which the Cartesi Machine is based.
To enter the playground, open a terminal, download the Docker image from Cartesi's repository, and run it adequately mapping the current user and group information, as well as making the host's current directory available inside the container:
$ docker pull cartesi/playground:0.3.0$ docker run -it --rm -h playground \-e USER=$(id -u -n) \-e GROUP=$(id -g -n) \-e UID=$(id -u) \-e GID=$(id -g) \-v `pwd`:/home/$(id -u -n) \-w /home/$(id -u -n) \cartesi/playground:0.3.0 /bin/bash
Once inside, you can execute the
cartesi-machine utility as follows:
playground:~$ cartesi-machine --helpUsage:/opt/cartesi/bin/cartesi-machine.lua [options] [command] [arguments]where options are:--server=<server-address>address of the remote cartesi machine server in one of the followingformats:<host>:<port>unix:<path>--ram-image=<filename>name of file containing RAM image (default: "linux.bin")--no-ram-imageforget settings for RAM image--ram-length=<number>set RAM length--rom-image=<filename>name of file containing ROM image (default: "rom.bin")--no-rom-bootargsclear default bootargs--append-rom-bootargs=<string>append <string> to bootargs--no-root-flash-driveclear default root flash drive and associated bootargs parameters--flash-drive=<key>:<value>[,<key>:<value>[,...]...]defines a new flash drive, or modify an existing flash drive definitionflash drives appear as /dev/mtdblock[1-7]<key>:<value> is one oflabel:<label>filename:<filename>start:<number>length:<number>sharedlabel (mandatory)identifies the flash drive and init attempts to mount it as /mnt/<label>filename (optional)gives the name of the file containing the image for the flash drivewhen omitted or set to the empty string, the drive starts filled with 0start (optional)sets the starting physical memory offset for flash drive in byteswhen omitted, drives start at 2 << 63 and are spaced by 2 << 60if any start offset is set, all of them must be setlength (optional)gives the length of the flash drive in bytes (must be a multiple of 4Ki)if omitted, the length is computed from the image in filenameif length and filename are set, the image file size must match lengthshared (optional)target modifications to flash drive modify image file as wellby default, image files are not modified and changes are lost(an option "--flash-drive=label:root,filename:rootfs.ext2" is implicit)--replace-flash-drive=<key>:<value>[,<key>:<value>[,...]...]replaces an existing flash drive right after machine instantiation.(typically used in conjunction with the --load=<directory> option.)<key>:<value> is one offilename:<filename>start:<number>length:<number>sharedsemantics are the same as for the --flash-drive option with the followingdifference: start and length are mandatory, and must match those of apreviously existing flash drive.--dhd=<key>:<value>[,<key>:<value>[,...]...]configures the dehashing deviceby default, the device is not present<key>:<value> is one offilename:<filename>tstart:<number>tlength:<number>filename (optional)gives the name of the file containing the initial dehashed data.when omitted or set to the empty string, the data starts filled with 0tstart (mandatory when device present)sets the start of target physical memory range for output datamust be aligned to tlengthtlength (mandatory when device present)gives the length of target physical memory range for output datamust be a power of 2 greater than 4Ki, or 0 when device not present--dhd-source=<address>server acting as source for dehashed data--max-mcycle=<number>stop at a given mcycle (default: 2305843009213693952)-i or --htif-console-getcharrun in interactive mode--htif-yield-progresshonor yield progress requests by target--htif-yield-rolluphonor yield rollup requests by target--dump-machine-configdump initial machine config to screen--load=<directory>load prebuilt machine from <directory>--store=<directory>store machine to <directory>--initial-hashprint initial state hash before running machine--final-hashprint final state hash when done--periodic-hashes=<number-period>[,<number-start>]prints root hash every <number-period> cycles. If <number-start> is given,the periodic hashing will start at that mcycle. This option implies--initial-hash and --final-hash.(default: none)--stepprint step log for 1 additional cycle when done--json-steps=<filename>output json with step logs for all cycles to <filename>--dump-pmasdump all PMA ranges to disk when doneand command and arguments:commandthe full path to the program inside the target system(default: /bin/sh)argumentsthe given command arguments<number> can be specified in decimal (e.g., 16) or hexadeximal (e.g., 0x10),with a suffix multiplier (i.e., Ki, Mi, Gi for 2^10, 2^20, 2^30, respectively),or a left shift (e.g., 2 << 20).<host> can be a host name, IPv4 or IPv6 address.
A final check can also be performed to verify if the contents inside the container are as expected:
playground:~$ md5sum /opt/cartesi/share/images/linux.binf7b127f9daba80d447df5656f911dfdd /opt/cartesi/share/images/linux.binplayground:~$ md5sum /opt/cartesi/share/images/rom.binff7df0dc89a60e0da0501b29b3700111 /opt/cartesi/share/images/rom.binplayground:~$ md5sum /opt/cartesi/share/images/rootfs.ext2f0d8d44543c78000c8906ed20a79e91f /opt/cartesi/share/images/rootfs.ext2