IBM Linux Technology Center Porting Linux to a new architecture, done right Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Overview 1 Status of new architecture ports 2 Typical approaches to new architectures 3 Lessons Learned 2 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right About me s390 architecture 2002-2005 PowerPC/Cell architecture 2005-now 32/64 bit syscall emulation Maintaining include/asm-generic Reviewing new architectures Learning about ARM 3 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Recently merged architectures 100000000 10000000 1000000 100000 arm xtensa avr32 blackfin mn10300 microblaze s*core tile 2.6.13 2.6.19 2.6.22 2.6.28 2.6.30 2.6.32 2.6.36 4 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Upcoming architectures nios II lm32 UniCore OpenRISC c64x MMIX nameless 48-bit architecture nameless DSP architecture 5 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right What makes architecture ports so hard? Typical approaches to new architectures 6 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Language barrier #1: English Homes of the current architecture maintainers 7 / 27 Arnd Bergmann c 2010 IBM Corporation pragmatically object-oriented freestanding ILP32/LP64 GNU 99 with static annotations and enforced coding style Porting Linux to a new architecture, done right Language barrier #2: C C 8 / 27 Arnd Bergmann c 2010 IBM Corporation pragmatically object-oriented freestanding ILP32/LP64 with static annotations and enforced coding style Porting Linux to a new architecture, done right Language barrier #2: C GNU C99 8 / 27 Arnd Bergmann c 2010 IBM Corporation pragmatically object-oriented freestanding ILP32/LP64 and enforced coding style Porting Linux to a new architecture, done right Language barrier #2: C GNU C99 with static annotations 8 / 27 Arnd Bergmann c 2010 IBM Corporation pragmatically object-oriented freestanding and enforced coding style Porting Linux to a new architecture, done right Language barrier #2: C ILP32/LP64 GNU C99 with static annotations 8 / 27 Arnd Bergmann c 2010 IBM Corporation pragmatically object-oriented and enforced coding style Porting Linux to a new architecture, done right Language barrier #2: C freestanding ILP32/LP64 GNU C99 with static annotations 8 / 27 Arnd Bergmann c 2010 IBM Corporation pragmatically and enforced coding style Porting Linux to a new architecture, done right Language barrier #2: C object-oriented freestanding ILP32/LP64 GNU C99 with static annotations 8 / 27 Arnd Bergmann c 2010 IBM Corporation and enforced coding style Porting Linux to a new architecture, done right Language barrier #2: C pragmatically object-oriented freestanding ILP32/LP64 GNU C99 with static annotations 8 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Language barrier #2: C pragmatically object-oriented freestanding ILP32/LP64 GNU C99 with static annotations and enforced coding style 8 / 27 Arnd Bergmann c 2010 IBM Corporation Noncoherent I/O Out-of-order I/O Memory management units Multiple ABIs Multiple ISAs Multiple platforms Timekeeping Porting Linux to a new architecture, done right Architectural challenges Symmetric Multiprocessing 9 / 27 Arnd Bergmann c 2010 IBM Corporation Out-of-order I/O Memory management units Multiple ABIs Multiple ISAs Multiple platforms Timekeeping Porting Linux to a new architecture, done right Architectural challenges Symmetric Multiprocessing Noncoherent I/O 9 / 27 Arnd Bergmann c 2010 IBM Corporation Memory management units Multiple ABIs Multiple ISAs Multiple platforms Timekeeping Porting Linux to a new architecture, done right Architectural challenges Symmetric Multiprocessing Noncoherent I/O Out-of-order I/O 9 / 27 Arnd Bergmann c 2010 IBM Corporation Multiple ABIs Multiple ISAs Multiple platforms Timekeeping Porting Linux to a new architecture, done right Architectural challenges Symmetric Multiprocessing Noncoherent I/O Out-of-order I/O Memory management units 9 / 27 Arnd Bergmann c 2010 IBM Corporation Multiple ISAs Multiple platforms Timekeeping Porting Linux to a new architecture, done right Architectural challenges Symmetric Multiprocessing Noncoherent I/O Out-of-order I/O Memory management units Multiple ABIs 9 / 27 Arnd Bergmann c 2010 IBM Corporation Multiple platforms Timekeeping Porting Linux to a new architecture, done right Architectural challenges Symmetric Multiprocessing Noncoherent I/O Out-of-order I/O Memory management units Multiple ABIs Multiple ISAs 9 / 27 Arnd Bergmann c 2010 IBM Corporation Timekeeping Porting Linux to a new architecture, done right Architectural challenges Symmetric Multiprocessing Noncoherent I/O Out-of-order I/O Memory management units Multiple ABIs Multiple ISAs Multiple platforms 9 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Architectural challenges Symmetric Multiprocessing Noncoherent I/O Out-of-order I/O Memory management units Multiple ABIs Multiple ISAs Multiple platforms Timekeeping 9 / 27 Arnd Bergmann c 2010 IBM Corporation Copy from ARM Copy from Tile Do not copy at all! Porting Linux to a new architecture, done right Where to start Copy from x86 10 / 27 Arnd Bergmann c 2010 IBM Corporation Copy from x86 Copy from Tile Do not copy at all! Porting Linux to a new architecture, done right Where to start Copy from ARM 10 / 27 Arnd Bergmann c 2010 IBM Corporation Copy from x86 Copy from ARM Do not copy at all! Porting Linux to a new architecture, done right Where to start Copy from Tile 10 / 27 Arnd Bergmann c 2010 IBM Corporation Copy from x86 Copy from ARM Copy from Tile Porting Linux to a new architecture, done right Where to start Do not copy at all! 10 / 27 Arnd Bergmann c 2010 IBM Corporation One minimal syscall list! Cover all the simple implementations Porting Linux to a new architecture, done right Generic header files 42 versions of struct stat? 11 / 27 Arnd Bergmann c 2010 IBM Corporation Cover all the simple implementations Porting Linux to a new architecture, done right Generic header files 42 versions of struct stat? One minimal syscall list! 11 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Generic header files 42 versions of struct stat? One minimal syscall list! Cover all the simple implementations 11 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Generic Architecture template Early Boot code zImage compression Library functions device tree Trap handling Signal handling ptrace pci 12 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right User space: runtime glibc/eglibc uClibc klibc 13 / 27 Arnd Bergmann c 2010 IBM Corporation Embedded distribution buildroot yocto emdebian Busybox initramfs Porting Linux to a new architecture, done right User space: distro Full distribution Debian, Fedora, OpenSUSE, Ubuntu, Gentoo, ... 14 / 27 Arnd Bergmann c 2010 IBM Corporation Busybox initramfs Porting Linux to a new architecture, done right User space: distro Full distribution Debian, Fedora, OpenSUSE, Ubuntu, Gentoo, ... Embedded distribution buildroot yocto emdebian 14 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right User space: distro Full distribution Debian, Fedora, OpenSUSE, Ubuntu, Gentoo, ... Embedded distribution buildroot yocto emdebian Busybox initramfs 14 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Lessons Learned 15 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Lesson #1 Start small 16 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Lesson #2 Generalize existing code for your special case 17 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Lesson #3 Understand the development process 18 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Lesson #4 Follow the upstream kernel 19 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Lesson #5 Debug your system with qemu with gdb 20 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Lesson #6 Simplify drivers using virtio and hvc 21 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Lesson #7 Describe SoC in a flattened device tree 22 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Lesson #8 Clean up after sparse and checkpatch 23 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Lesson #9 Run lockdep enabled kernels 24 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Lesson #10 Become a git master 25 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Legal Statement This work represents the view of the author and does not necessarily represent the view of IBM. IBM, IBM (logo), e-business (logo), pSeries, e (logo) server, and xSeries are trademarks or registered trademarks of International Business Machines Corporation in the United States and/or other countries. Linux is a registered trademark of Linus Torvalds. Other company, product, and service names may be trademarks or service marks of others. 26 / 27 Arnd Bergmann c 2010 IBM Corporation Porting Linux to a new architecture, done right Questions? 27 / 27 Arnd Bergmann c 2010 IBM Corporation.