PLUG May 2013

1. PLUG May 2013 Porting Linux Applications to Power Architecture Part 1 - Introduction

2. What is porting? • X86 has become the defacto standard architecture • Most code (including Linux code) is developed for the x86 platform • The proper way to write apps is to make them architecture agnostic • This is easy for Apps but rarely practiced • There is a necessity to migrate the code it to other platforms. Essentially recompile it to run on the new platform architecture

3. Factors involved in Porting – x86 to Power • HW • Big endian vs Little endian • CISC vs RISC • Instruction width • Chip level design • 32b vs 64b • Implementation • Data type size (int and long difference in 32 vs 64) • EABI • Libraries • Good code is written in a Architecture transparent manner

4. Porting Kernel/drivers vsUserspace Apps • Porting ranges from a very simple recompile to the worst case • Simplest is independent code using standard include libraries • Little more complicated when special dependencies are present • Harder when hardware is involved (e.g. kernel, drivers) . Includes endian conversion, structure repacking, messages (between hardware and CPU) • Hardest when assembly code present

5. Tools • GCC • GlibC, binutils • Other tools • Other Scripting languages : Shell, Perl, python, • Freescaletoolchain : powerpc-linux-gnu-gcc • Part of Yocto SDK, or get through repo build-essential • IBM Tool Chain : https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/W51a7ffcf4dfd_4b40_9d82_446ebc23c550/page/IBM%20Advance%20Toolchain%20for%20PowerLinux%20Documentation • Clang/LLVM • Git, Hg, SVN

6. Cross vs Native compile • Build can be native i.e. build on the same platform as you are executing • Or cross-compile where you build on a platform that is different than the platform you execute on • Using the tools listed in the previous page. sgy@sgy-ThinkPad-R500:~$ gcchello.c -o hello.x86 sgy@sgy-ThinkPad-R500:~$ file hello.x86 hello.x86: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.24, BuildID[sha1]=0xffad75b6bb6432582e7a7cc211e225639a14cf85, not stripped sgy@sgy-ThinkPad-R500:~$ powerpc-linux-gnu-gcchello.c –o hello.ppc sgy@sgy-ThinkPad-R500:~$ file hello.ppc hello.ppc: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=0xe80c0aefeeeece9e7ec150a0a45f0ac25ad8a060, not stripped

7. Ubuntu build • http://qa.ubuntuwire.org/ftbfs/ • buildlog • Tracing failure • Fixing

8. Debugging Applications • grep /web search • lsof • strace • gdb • printf • Kernel debug

9. lsof • list the information about the files (which includes libraries, pipes, sockets, devices….)that are opened by various processes • Very useful for debugging • Flags to search by user, pid, ... root@sgy-ThinkPad-R500:~$ lsof-p 1190 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME irqbalanc 1190 root cwd DIR 8,1 4096 2 / irqbalanc 1190 root rtd DIR 8,1 4096 2 / irqbalanc 1190 root txt REG 8,1 43068 2621866 /usr/sbin/irqbalance irqbalanc 1190 root mem REG 8,1 34844 526097 /lib/powerpc-linux-gnu/librt-2.16.so irqbalanc 1190 root mem REG 8,1 131217 526095 /lib/powerpc-linux-gnu/libpthread-2.16.so irqbalanc 1190 root mem REG 8,1 239092 525164 /lib/powerpc-linux-gnu/libpcre.so.3.13.1 irqbalanc 1190 root mem REG 8,1 1537380 525433 /lib/powerpc-linux-gnu/libc-2.16.so irqbalanc 1190 root mem REG 8,1 42832 2621865 /usr/lib/libnuma.so.1 irqbalanc 1190 root mem REG 8,1 706852 526082 /lib/powerpc-linux-gnu/libm-2.16.so irqbalanc 1190 root mem REG 8,1 1113248 524322 /lib/powerpc-linux-gnu/libglib-2.0.so.0.3504.0 irqbalanc 1190 root mem REG 8,1 25860 2622193 /usr/lib/libcap-ng.so.0.0.0 irqbalanc 1190 root mem REG 8,1 142596 524503 /lib/powerpc-linux-gnu/ld-2.16.so irqbalanc 1190 root 0u CHR 1,3 0t0 1029 /dev/null irqbalanc 1190 root 1u CHR 1,3 0t0 1029 /dev/null irqbalanc 1190 root 2u CHR 1,3 0t0 1029 /dev/null

10. strace • Run a command and display its system calls, so you can see exactly what the program is doing until it exits • Can be used for debugging and performance tuning root@sgy-ThinkPad-R500:~$ stracels execve("/bin/ls", ["ls"], [/* 18 vars */]) = 0 brk(0) = 0x102b3000 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x48021000 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3 fstat64(3, {st_mode=S_IFREG|0644, st_size=41633, ...}) = 0 mmap(NULL, 41633, PROT_READ, MAP_PRIVATE, 3, 0) = 0x48022000 close(3) = 0 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) open("/lib/powerpc-linux-gnu/libselinux.so.1", O_RDONLY|O_CLOEXEC) = 3 read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\24\0\0\0\1\0\0P\300\0\0\0004"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0644, st_size=137164, ...}) = 0 mmap(0xffce000, 138072, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xffce000 mmap(0xffee000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x20000) = 0xffee000 close(3) = 0 open("/proc/filesystems", O_RDONLY|O_LARGEFILE) = 3 fstat64(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0 = 0 ioctl(1, TIOCGWINSZ, {ws_row=57, ws_col=132, ws_xpixel=961, ws_ypixel=860}) = 0 openat(AT_FDCWD, ".", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_CLOEXEC) = 3 getdents64(3, /* 12 entries */, 32768) = 368 getdents64(3, /* 0 entries */, 32768) = 0 close(3) = 0 fstat64(1, {st_mode=S_IFCHR|0600, st_rdev=makedev(136, 0), ...}) = 0 close(2) = 0 exit_group(0) = ?