Linux kernel System Call Interface and uClibc

μClinux is a variation of the

Linux kernel The Linux kernel is a free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally authored in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU ...

, previously maintained as a fork, that targets

microcontroller A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs ( processor cores) along with memory and programma ...

s without a

memory management unit A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit having all memory references passed through itself, primarily performing the translation of virtual memory addresses to physical ...

(MMU). It was integrated into the mainline kernel as of 2.5.46; the project continues to develop patches and tools for microcontrollers. The homepage lists Linux kernel releases for 2.0, 2.4 and 2.6 (all of which are end-of-life in mainline). The letters "μC" are for "microcontroller": the name is pronounced "you-see-Linux", rather than pronouncing the letter mu as in

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

History

μClinux was originally created by D. Jeff Dionne and Kenneth Albanowski in 1998. Initially, they targeted the Motorola DragonBall family of embedded

68k The Motorola 68000 series (also known as 680x0, m68000, m68k, or 68k) is a family of 32-bit complex instruction set computer (CISC) microprocessors. During the 1980s and early 1990s, they were popular in personal computers and workstations and w ...

processors (specifically the 68EZ328 series used in the Motorola PalmPilot) on a 2.0.33 Linux kernel. After releasing their initial work, a developer community quickly sprang up extending their work to newer kernels and other microprocessor architectures. In early 1999, support was added for the Motorola (now Freescale) ColdFire family of embedded microprocessors. ARM processor support was added later. Although originally targeting 2.0 series Linux kernels, it now has ports based on Linux 2.4 and Linux 2.6. The Linux 2.4 ports were forward ported from the 2.0.36 Linux kernel by Michael Leslie and Evan Stawnyczy during their work at Rt-Control. There were never any μClinux extensions applied to the 2.2 series kernels. Since version 2.5.46 of the Linux kernel, the major parts of μClinux have been integrated with the mainline kernel for a number of processor architectures. Greg Ungerer (who originally ported μClinux to the Motorola ColdFire family of processors) continued to maintain and actively push core μClinux support into the 2.6 series Linux kernels. In this regard, μClinux is essentially no longer a separate fork of Linux. μClinux had support for many architectures, and forms the basis of many products, like

network routers A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions between networks and on the global Internet. Data sent through a network, such as a web page or email, ...

, security cameras, DVD or MP3 players,

VoIP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Interne ...

phone or gateways, scanners, and card readers. Support for several of the original target architectures was dropped in 2018. The obsolete CPU architectures set to be removed in Linux 4.17 and subsequent releases included ADI Blackfin, Etrax CRIS, Fujitsu FR-V, Mitsubishi M32R, Matsushita/Panasonic MN10300, Imagination META (Metag), and Tilera TILE.

Supported architectures

The current list includes: *

Altera Altera Corporation was a manufacturer of programmable logic devices (PLDs) headquartered in San Jose, California. It was founded in 1983 and acquired by Intel in 2015. The main product lines from Altera were the flagship Stratix series, mid-ra ...

Nios/

Nios II Nios II is a 32-bit embedded processor architecture designed specifically for the Altera family of field-programmable gate array (FPGA) integrated circuits. Nios II incorporates many enhancements over the original Nios architecture, making it mo ...

Amber Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects."Amber" (2004). In M ...

(open FPGA core) * ARM

ARM7TDMI ARM7 is a group of 32-bit RISC ARM processor cores licensed by ARM Holdings for microcontroller use. The ARM7 core family consists of ARM700, ARM710, ARM7DI, ARM710a, ARM720T, ARM740T, ARM710T, ARM7TDMI, ARM7TDMI-S, ARM7EJ-S. The ARM7TDM ...

, ARM Cortex-M3/M4/M7,

ARM Cortex-R The ARM Cortex-R is a family of 32-bit and 64-bit RISC ARM processor cores licensed by Arm Holdings. The cores are optimized for hard real-time and safety-critical applications. Cores in this family implement the ARM Real-time (R) profile, w ...

* Lattice

Mico32 LatticeMico32 is a 32-bit microprocessor reduced instruction set computer (RISC) soft core from Lattice Semiconductor optimized for field-programmable gate arrays (FPGAs). It uses a Harvard architecture, which means the instruction and data buses a ...

* NXP 680x0 (Motorola/Freescale 680x0) *

Hitachi () is a Japanese multinational corporation, multinational Conglomerate (company), conglomerate corporation headquartered in Chiyoda, Tokyo, Japan. It is the parent company of the Hitachi Group (''Hitachi Gurūpu'') and had formed part of the Ni ...

H8 * Hyperstone E1/E2 (called hyLinux) *

Intel i960 Intel's i960 (or 80960) was a RISC-based microprocessor design that became popular during the early 1990s as an embedded microcontroller. It became a best-selling CPU in that segment, along with the competing AMD 29000. In spite of its succes ...

* MIPS * NXP ColdFire (Motorola/Freescale ColdFire) * NEC V850E *

Xilinx Xilinx, Inc. ( ) was an American technology and semiconductor company that primarily supplied programmable logic devices. The company was known for inventing the first commercially viable field-programmable gate array (FPGA) and creating the fi ...

MicroBlaze

No longer supported

Before Linux 4.17 the following architectures were also supported: * ADI Blackfin * Axis ETRAX *

Fujitsu is a Japanese multinational information and communications technology equipment and services corporation, established in 1935 and headquartered in Tokyo. Fujitsu is the world's sixth-largest IT services provider by annual revenue, and the la ...

FR-V

References

External links

μClinux mailing list
* *
μClinux at SourceForge
*
Accelerated Linux
an actively developed continuationBoF- Accelerated Linux Build System - Jeff Shaw, Digi International
/ref> of μClinux-dist by Digi {{DEFAULTSORT:UClinux Embedded operating systems Embedded Linux Lightweight Unix-like systems ARM operating systems Linux kernel