嵌入式處理器架構與程式設計 王建民 中央研究院 資訊所 2008 年 7 月

2 Contents Introduction Computer Architecture ARM Architecture Development Tools  GNU Development Tools ARM Instruction Set ARM Assembly Language ARM Assembly Programming  GNU ARM ToolChain Interrupts and Monitor

Lecture 5 GNU Development Tools

4 Outline Linux/Cygwin GNU Compiler Collection GNU Libraries and Linker GNU Binary Utilities

5 Cygwin Cygwin is a Linux-like environment for Windows. It consists of two parts: A DLL (cygwin1.dll) which acts as a Linux emulation layer providing substantial Linux API functionality. A collection of tools, which provide Linux look and feel.

6 Installation 1

7 Installation 2

8 Installation 3

9 Installation 4

10 Installation 5

11 Installation 6

12 Installation 7

13 Linux Commands 1 cat concatenate file(s) ex. $ cat hello.c ex. $ cat > newfile Hello World CTRL-D

14 Linux Commands 2 ls list information about the files (the current directory by default).

15 Linux Commands 3 cp copy source to destination ex. $ cp foo1 other mv move/rename source to destination ex. $ mv foo1 other rm delete file(s) ex. $ rm hello.c

16 Linux Commands 4 mkdir create a new directory ex. $ mkdir exercise rmdir remove a empty directory ex. $ rmdir exercise remove a directory containing files ex. $ rm –r exercise

17 Linux Commands 5 pwd show current directory ex. $ pwd /home/user1 cd change current directory ex. $ cd exercise

18 Linux Commands 6 ps show processes ex. $ ps kill kill a process ex. $ kill pid

19 Linux Commands 7 run a program in the background add & following the command line ex. $./hello &

20 Linux Commands 8 fg run a background program in the foreground ex. $ fg %job_num $ jobs [1]+ gcc program.c $ fg %1

21 Linux Commands 9 run the foreground program in the background ex. $ gcc program.c –o program Ctrl-z [1]+ stopped gcc program.c –o program $ bg [1]+ stopped gcc program.c –o program $

22 Outline Linux/Cygwin GNU Compiler Collection GNU Libraries and Linker GNU Binary Utilities

23 GNU Compiler Collection GNU Compiler Collection (GCC) An integrated distribution of compilers for several major programming languages C, C++, Objective-C, Fortran, Java, and Ada

24 Preprocessor Compiler Assembler Linker input files.c.s.o.a a.out / a.exe output files The Compilation Process

25 An Example #define GREETING ”Hello, World!\n” int main() { printf(GREETING); } hello.c

26 Using gcc 1 The simplest way to compile gcc hello.c  a.exe executable file If you want to produce a executable file named “hello” gcc -o hello hello.c  hello.exe executable file

27 Using gcc 2 To compile with multiple source files Ex: gcc -o hello hello.c foo.c  hello.exe executable file hello.c : extern void foo(char []) int main() { char str[]=“hello world!”; foo(str); } foo.c : void foo(char str[]) { printf(“%s\n”,str); }

28 Using gcc 3 -E: Stop after the preprocessing stage; do not run the compiler proper

29 Using gcc 4 -S: Stop after the stage of compilation proper; do not assemble. Output assembly code file (*.s)

30 Using gcc 5 -c : Compile and assemble the source files, but do not link. gcc –c hello.c  hello.o object file -o file : Place output in file file gcc –o hello hello.c  hello.exe

31 Using gcc 6 Specifying libraries -llibrary : Search the library named library when linking library file name : liblibrary.a  ex: foo.o refers to functions in library file “libz.a”  gcc -o foo foo.o -lz

32 Using gcc 7 Specify directories to search for header files, for libraries and for parts of the compiler -Idir: Add the directory dir to the head of the list of directories to be searched for header file. -Ldir : Add directory dir to the list of directories to be searched for -l.

33 Using gcc 8 Example A header file in “/tmp/foo.h” A function foo() in library “/tmp/libfoo.a” A program: /home/foo/foo.c gcc –I/tmp/foo.h –L/tmp/libfoo.a foo.c -lfoo #include int main() { … foo(); … }

34 Debugging Options -g : Produce debugging information in the operating system's native format -ggdb : Produce debugging information for use by GDB -time : Report the CPU time taken by each subprocess in the compilation sequence

35 Optimization Options 1 -O0 : Do not optimize (the default) -O or -O1 : Optimize Tries to reduce code size and execution time, without performing any optimizations that take a great deal of compilation time. -O2 : Optimize even more Performs nearly all supported optimizations that do not involve a space-speed tradeoff. Does not perform loop unrolling or function inlining.

36 Optimization Options 2 -O3 : Optimize yet more Turns on all optimizations specified by -O2 and also turns on the -finline-functions -Os : Optimize for size Enables all –O2 optimizations that do not typically increase code size -funroll-loops : Loop unrolling -finline-functions : Function inlining

37 Outline Linux/Cygwin GNU Compiler Collection GNU Libraries and Linker GNU Binary Utilities

38 How to make library 1 Example: write a function print_str in “foo.c” foo.c: #include void print_str(char str[]) { printf(“%s\n”, str); }

39 How to make library 2 First, make the object file “foo.o” Second, use “ar” to create archive file “libfoo.a”. Option “c” to crate archive file, “r” to insert or replace members to archive file. $ gcc -c foo.c $ ar cr libfoo.a foo.o

40 How to use library Write a header file “foo.h” : Our program “hello.c” : hello.c: #include main () { print_str(“hello world!”); } foo.h : extern void print_str(char []);

41 How to link library Compile with library (assume “foo.h” & “libfoo.a” in “/tmp” directory.) gcc include “linker” step. You can also use “ld” to linker objects and libraries. $ gcc -I/tmp -L/tmp hello.c -lfoo $./a.out hello world!

42 Practice #1 Temperature C = (5/9)(F-32) Write a subroutine that convert the temperature. Compile the subroutine into an object file. Make a temperature library Write a program that invokes the function to convert a source temperature to a target one

43 GNU C Library In Linux, header files is usually in “/usr/include”. Online manual To use GNU C library, you can search the function name to see what header files you need to include, and what library you need to link.

44 GNU Linker “ld” ld combines a number of object and archive files, relocates their data and ties up symbol references. Usually the last step in compiling a program, ex: $ gcc -I/tmp -c hello.c $ ld -o hello -L/tmp /usr/lib/crt1.o /usr/lib/crti.o hello.o -lfoo.a -lc $./hello hello world!

45 Shared Library 1 Use ld to make shared object (shared library). Compile a shared library Use “gcc” to make object file with “-fPIC” option (generate position-independent code for use in a shared library). Use “ld” with “-shared”, “-soname” to make shard object. $ gcc -fPIC -c foo.c $ ld -shared -soname libfoo.so -o libfoo.so.0 -lc foo.o

46 Shared Library 2 Install shared library Use “ldconfig” with “-v”, “-n” options. “-v” to show messages. “-n” to process directories specified on the command line. Not applicable on Cygwin! (why?) $ ldcofnig -v -n..: libfoo.so -> libfoo.so.0 (changed)

47 Shared Library 3 Using shared library Add “/tmp” in LD_LIBRARY_PATH (assume our libfoo.so in “/tmp” directory)  In bash  In tcsh or csh Compile with library $ export LD_LIBRARY_PATH=/tmp:$LD_LIBRARY_PATH $ setenv LD_LIBRARY_PATH /tmp:$LD_LIBRARY_PATH $ gcc -I/tmp -L/tmp -o hello hello.c –lfoo $./hello hello world!

48 Linker Options 1 -o output : Use output as the name for the program produced by ld. -larchive : Add archive file archive to the list of files to link. -Lsearchdir : Add path searchdir to the list of paths that ld will search for archive libraries.

49 Linker Options 2 -b input-format : to specify the binary format for input object files. ld may be configured to support more than one kind of object file. -r : generate an output file that can in turn serve as input to ld. This is often called partial linking. -E : When creating a dynamically linked executable, add all symbols to the dynamic symbol table.

50 Linker Options 3 When using gcc, you can pass linking options by “-Wl,option”. Pass one option at once $ gcc –Wl,-L. -Wl,-ohello -I/tmp -L/tmp hello.c -lfoo $./hello hello world!

51 Practice #2 Temperature C = (5/9)(F-32) Make a temperature shared library Write a program that invokes the function to convert a source temperature to a target one

52 Outline Linux/Cygwin GNU Compiler Collection GNU Libraries and Linker GNU Binary Utilities

53 ar Creates, modifies, and extracts from archives. An archive is a single file holding a collection of other files in a structure that makes it possible to retrieve the original individual files. ar is considered a binary utility because archives of this sort are most often used as libraries holding commonly needed subroutines. ar creates an index to the symbols defined in relocatable object modules in the archive.

54 ar - Some Options ar [options] archive [member...] c - create the archive. r - insert the files member... into archive. a - add new files after an existing member of the archive. b - add new files before an existing member of the archive.

55 ar - Example Write a function print_str in “foo.c” Make the object file “foo.o” Use “ar” to create archive file “libfoo.a”. Option “c” to crate archive file, “r” to insert or replace members to archive file. void print_str(char str[]) { printf(“%s\n”, str); } $ gcc -c foo.c $ ar cr libfoo.a foo.o

56 ranlib Generates an index to the contents of an archive and stores it in the archive. The index lists each symbol defined by a member of an archive that is a relocatable object file. Example $ ranlib libfoo.a

57 nm Lists the symbols from object files. For each symbol, nm shows: The symbol value The symbol type The symbol name Example $ nm -s libfoo.a Archive index: foo in foo.o foo.o: T foo U printf

58 nm - Symbol Types In the example T : The symbol is in the text (code) section. U : The symbol is undefined. Some other types D : The symbol is in the initialized data section. N : The symbol is a debugging symbol.

59 nm - Some Options -A, -o, --print-file-name : precede each symbol by the name of the input file (or archive member) in which it was found. -s, --print-armap : include the index. -a, --debug-syms : display all symbols. -g, --extern-only : display only external symbols.

60 objdump Displays information about one or more object files. Options -a : Display archive header information. $ objdump -a libfoo.a In archive libfoo.a: foo.o: file format elf32-i386 rw-r--r-- 824/ May 13 11: foo.o

61 objdump - Other Options -f : Display contents of the overall file header. -h : Display contents of the section headers. -x : Display contents of all headers. -d : Display assembler contents of executable sections. -r : Display the relocation entries of the file. -t : Display contents of the symbol table(s).

62 objdump - Sample 1 $ objdump -h -r test1.o test1.o: file format pe-i386 Sections: Idx Name Size VMA LMA File off Algn 0.text b4 2**4 CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE 1.data **4 ALLOC, LOAD, DATA 2.bss **4 ALLOC 3.rdata f4 2**4 CONTENTS, ALLOC, LOAD, READONLY, DATA RELOCATION RECORDS FOR [.text]: OFFSET TYPE VALUE DISP32 __alloca DISP32 ___main d dir32.rdata DISP32 _printf

63 objdump - Sample 2 $ objdump -h -r test1.exe test1.exe: file format pei-i386 Sections: Idx Name Size VMA LMA File off Algn 0.text **4 CONTENTS, ALLOC, LOAD, READONLY, CODE 1.rdata **4 CONTENTS, ALLOC, LOAD, READONLY, DATA 2.bss **4 ALLOC 3.idata a00 2**2 CONTENTS, ALLOC, LOAD, DATA

64 readelf Displays information about one or more ELF format object files. Example: we use “-e” option to read all header from the executable file of “hello.c” Not applicable on Cygwin! (why?) $ gcc hello.c $ readelf -e a.out

65 readelf - Some Options -h : Show ELF header information. -l : Show program header information. -S : Show section header informaion. -s : Show the entries in symbol table section. -e : Show all headers.

66 Other Binary Utilities objcopy - copy and translate object files size - list section sizes and total size strings - list printable strings from files strip - discard symbols addr2line - convert addresses to file and line