A short presentation on uClinux, its applications and my experience with it.

1. A short presentation on uClinux, its applications and my experience with it. Designed and presented by Emile Belanger

2. Overview • What is uClinux • Commercial application for uClinux • The key differences between uClinux and Linux • What the engineer should know • Porting uClinux to a μC/Processor. • My experience using uClinux • A short demonstration(?)

3. What is uClinux? • Pronounced ‘You-See-Linux’ • A derivative of the 2.0/4/6 Linux kernel • Designed to work with microcontrollers or CPUs without an MMU, with limited storage and RAM • Full networking support • Support for many file systems. • Graphical windowing

4. Commercial applications • Established, powerful multitasking operating system. • Royalty Free! • Large software base PDAs Data terminals Routers Security VoIP

5. uClinux Requirement • 32 bit Microcontroller or Microprocessor • 512KB RAM min. (2MB+ recommended) • 515KB ROM min. • Hardware Timer + Interrupt • Fully functional C/C++ complier

6. uClinux vs. Linux • The main differences revolve around the lack of MMU

7. uClinux vs. Linux • The Memory Management Unit allows the use of Virtual Memory (VM) • Translates Virtual Address space into physical address space

8. uClinux vs. Linux • Enables page swapping

9. uClinux vs. Linux • Memory Protection

10. uClinux vs. Linux • What this means to the software engineer. • No page swapping • No hardware memory protection • Only the Binary Flat Format (BFLT) executable type is supported • Use page_alloc2 as a kernel memory allocator • Non dynamic stack • Memory can not be ‘defragmented’ • fork() replaced with vfork() • XIP

11. uClinux vs. Linux • Memory fragmentation Even though there is 32KB reported free memory, the maximum process size which can run is 12KB

12. uClinux vs. Linux • fork() Parent (1)When fork() is called, a child process is created, and continues to run from fork() fork()(!=0) Stack/heap(0)

13. uClinux vs. Linux • fork() Parent Child (2)When the child is created, it first shares the parents memory. The shared variables tag is incremented by 1 fork()(!=0) fork() (==0) Stack/heap(1)

14. uClinux vs. Linux • fork() Parent Child (3)If the child tries to write to any global variables, the C.O.W is executed and a new copy of the variable is created. The tag is decremented. fork()(!=0) fork() (==0) Stack/heap(0) Stack/heap(0) If the tag = 0, then the variable is not shared

15. uClinux vs. Linux • vfork() Parent (1)When vfork() is called, a child process is created, and continues to run from vfork(). However, the parent process if BLOCKED vfork()(!=0) Stack/heap(0)

16. uClinux vs. Linux • vfork() Parent Child (2)When the child is created, it ALWAYS shares the memory of the parent. Changes made by the child will also be made in the parent. vfork()(!=0) vfork() (==0) _exit() Stack/heap(1)

17. uClinux vs. Linux • How to overcome the shared memory vfork() limitation. int main(void) { pid_t pid; int value = 10; if ((pid = vfork()) == 0) { int new_value = value; new_value-=5; printf("The child process thinks value=%d\n", new_value); exit(EXIT_SUCCESS); } printf("The parent process thinks value=%d\n", value); printf("Goodbye.\n"); return EXIT_SUCCESS; } Ref: http://www.uclinux.org/pub/uClinux/archive/0772.html

18. uClinux vs. Linux • XIP (Execute In Place) RAM ROM Process 1 Process 2 Process 3 Code Code Code Code Stack/heap Stack/heap Stack/heap Code Stack/heap Stack/heap Stack/heap

19. Porting uClinux to a μC/Processor • Supported architectures • Motorola DragonBall, • Motorola ColdFire • ADI Blackfin • Motorola QUICC • ETRAX • ARM7TDMI • MC68EN302 • Microblaze • + Others being added all the time!

20. Porting uClinux to a μC/Processor • If your Processor and Board are not already supported: • /linux/arch • Edit around two dozen files relating to instructions specific to the CPU core • /linux/platform • Interrupt vectors • Hardware registers • Timer initialisation • Amount of memory • External Peripherals

21. uClinux on Microblaze My experience getting uClinux running on a custom board.

22. uClinux on Microblaze

23. uClinux on Microblaze • The Microblaze soft processor: • 32 bit Harvard RISC architecture • 3-stage pipeline with 32 general-purpose registers • FPU • Hardware divide and multiply • Instruction and Data Caches • Many configurable peripherals

24. uClinux on Microblaze • Possible user implemented features: • Graphical controller (LCD) • Custom IO standards • Hardware acceleration

25. uClinux on Microblaze

26. uClinux on Microblaze • Primary components • XC3S400 Xilinx FPGA • 2Mb Xilinx PROM • 256Mb SDRAM • 1.2V and 2.5V DC/DC converter • 40MHZ xtal

27. uClinux on Microblaze

28. uClinux on Microblaze Top

29. uClinux on Microblaze Underside

30. uClinux on Microblaze

31. uClinux on Microblaze

32. uClinux on Microblaze • Outline of steps require to get uClinux functional • Implement Microblaze, SDRAM controller, UART, Timer + interrupt in FPGA. • Download latest uClinux tree via CVS • Copy autoconfig file generated by Xilinx software to uClinux tree • Run ‘make config’, ‘make dep’, ‘make all’ • Upload binary image file into SDRAM via Jtag debug cable • Reset Microblaze to run!

33. uClinux on Microblaze Linux version 2.4.31-uc0 (root@fedora3) (gcc version 2.95.3-4 Xilinx EDK 6.3 Build EDK_Gmm.12.2) #24 Sun Oct 2 12:58:50 BST 2005On node 0 totalpages: 8192zone(0): 8192 pages.zone(1): 0 pages.zone(2): 0 pages.CPU: MICROBLAZEKernel command line: °Console: xmbserial on UARTLiteCalibrating delay loop... 1.32 BogoMIPSMemory: 32MB = 32MB totalMemory: 30916KB available (562K code, 927K data, 32K init)Dentry cache hash table entries: 4096 (order: 3, 32768 bytes)Inode cache hash table entries: 2048 (order: 2, 16384 bytes)Mount cache hash table entries: 512 (order: 0, 4096 bytes)Buffer cache hash table entries: 1024 (order: 0, 4096 bytes)Page-cache hash table entries: 8192 (order: 3, 32768 bytes)POSIX conformance testing by UNIFIXLinux NET4.0 for Linux 2.4Based upon Swansea University Computer Society NET3.039Microblaze UARTlite serial driver version 1.00ttyS0 at 0x40600000 (irq = 1) is a Microblaze UARTliteStarting kswapdRAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksizeuclinux[mtd]: RAM probe address=0x220bd93c size=0xb7000uclinux[mtd]: root filesystem index=0VFS: Mounted root (romfs filesystem) readonly.Freeing init memory: 32KMounting proc: Mounting var: Populating /var: Running local start scripts.Remounting / (rw): Mounting /etc/config: Populating /etc/config: flatfsd: Nonexistent or bad flatfs (-43), creating new one...flatfsd: Failed to write flatfs (-43): No such deviceflatfsd: Created 3 configuration files (346 bytes)Setting hostname: uclinux-auto login:rootPassword: # lsbin dev etc home lib mnt proc sbin tmp usr var#

34. Thank you for listening. Are there any Question? www.uclinux.org www.ucdot.org http://www.arcturusnetworks.com/uclinux.shtml http://www-128.ibm.com/developerworks/linux/library/l-embl.html http://www.linuxjournal.com/article/7221 http://linuxdevices.com/articles/AT9541681360.html http://www.uclinux.org/pub/uClinux/archive/0772.html