システムコールexit
まずは man 2 exitの調査からいってみます
NAME
_exit, _Exit - terminate the calling process
SYNOPSIS
#include <unistd.h>
void _exit(int status);
#include <stdlib.h>
void _Exit(int status);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_Exit(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99ソース hello4.cをかいてみます。
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ cat hello4.c
#include <unistd.h>
#define MSG "hello\n"
int mywrite( const char * buf , int len)
{
int ret;
asm(
"int $0x80"
: "=a" (ret)
: "a" (4) ,
"b" (1) ,
"c" (buf) ,
"d" (len)
);
return ret;
}
void myexit(int stat)
{
asm(
"int $0x80"
:
: "a" (1),
"b" (stat)
);
}
int main(void)
{
int ret;
ret = mywrite(MSG , sizeof(MSG));
myexit(ret);
}
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ つづいてこんぱいるして、実行してみて、間違いのないことを確認します。
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ gcc -v -Wall -save-temps -o hello4 hello4.c Using built-in specs. Target: i486-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.4.3-4ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --program-suffix=-4.4 --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-plugin --enable-objc-gc --enable-targets=all --disable-werror --with-arch-32=i486 --with-tune=generic --enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu Thread model: posix gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5) COLLECT_GCC_OPTIONS='-v' '-Wall' '-save-temps' '-o' 'hello4' '-mtune=generic' '-march=i486' /usr/lib/gcc/i486-linux-gnu/4.4.3/cc1 -E -quiet -v hello4.c -D_FORTIFY_SOURCE=2 -mtune=generic -march=i486 -Wall -fpch-preprocess -fstack-protector -o hello4.i ignoring nonexistent directory "/usr/local/include/i486-linux-gnu" ignoring nonexistent directory "/usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../i486-linux-gnu/include" ignoring nonexistent directory "/usr/include/i486-linux-gnu" #include "..." search starts here: #include <...> search starts here: /usr/local/include /usr/lib/gcc/i486-linux-gnu/4.4.3/include /usr/lib/gcc/i486-linux-gnu/4.4.3/include-fixed /usr/include End of search list. COLLECT_GCC_OPTIONS='-v' '-Wall' '-save-temps' '-o' 'hello4' '-mtune=generic' '-march=i486' /usr/lib/gcc/i486-linux-gnu/4.4.3/cc1 -fpreprocessed hello4.i -quiet -dumpbase hello4.c -mtune=generic -march=i486 -auxbase hello4 -Wall -version -fstack-protector -o hello4.s GNU C (Ubuntu 4.4.3-4ubuntu5) version 4.4.3 (i486-linux-gnu) compiled by GNU C version 4.4.3, GMP version 4.3.2, MPFR version 2.4.2-p1. GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 GNU C (Ubuntu 4.4.3-4ubuntu5) version 4.4.3 (i486-linux-gnu) compiled by GNU C version 4.4.3, GMP version 4.3.2, MPFR version 2.4.2-p1. GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 Compiler executable checksum: 5998ce5f1765e99eea5269f4c1e38d44 hello4.c: In function ‘main’: hello4.c:33: warning: control reaches end of non-void function COLLECT_GCC_OPTIONS='-v' '-Wall' '-save-temps' '-o' 'hello4' '-mtune=generic' '-march=i486' as -V -Qy -o hello4.o hello4.s GNU assembler version 2.20.1 (i486-linux-gnu) using BFD version (GNU Binutils for Ubuntu) 2.20.1-system.20100303 COMPILER_PATH=/usr/lib/gcc/i486-linux-gnu/4.4.3/:/usr/lib/gcc/i486-linux-gnu/4.4.3/:/usr/lib/gcc/i486-linux-gnu/:/usr/lib/gcc/i486-linux-gnu/4.4.3/:/usr/lib/gcc/i486-linux-gnu/:/usr/lib/gcc/i486-linux-gnu/4.4.3/:/usr/lib/gcc/i486-linux-gnu/ LIBRARY_PATH=/usr/lib/gcc/i486-linux-gnu/4.4.3/:/usr/lib/gcc/i486-linux-gnu/4.4.3/:/usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../lib/:/lib/../lib/:/usr/lib/../lib/:/usr/lib/gcc/i486-linux-gnu/4.4.3/../../../:/lib/:/usr/lib/:/usr/lib/i486-linux-gnu/ COLLECT_GCC_OPTIONS='-v' '-Wall' '-save-temps' '-o' 'hello4' '-mtune=generic' '-march=i486' /usr/lib/gcc/i486-linux-gnu/4.4.3/collect2 --build-id --eh-frame-hdr -m elf_i386 --hash-style=both -dynamic-linker /lib/ld-linux.so.2 -o hello4 -z relro /usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../lib/crt1.o /usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../lib/crti.o /usr/lib/gcc/i486-linux-gnu/4.4.3/crtbegin.o -L/usr/lib/gcc/i486-linux-gnu/4.4.3 -L/usr/lib/gcc/i486-linux-gnu/4.4.3 -L/usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../lib -L/lib/../lib -L/usr/lib/../lib -L/usr/lib/gcc/i486-linux-gnu/4.4.3/../../.. -L/usr/lib/i486-linux-gnu hello4.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/i486-linux-gnu/4.4.3/crtend.o /usr/lib/gcc/i486-linux-gnu/4.4.3/../../../../lib/crtn.o [hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ [hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ ./hello4 hello [hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$
さて、ここからようやく本題です。
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ ld -e main -o hello4 hello4.o [hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ ./hello4 hello [hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ ls -ltr hello4 -rwxr-xr-x 1 500 500 1038 2012-02-04 18:52 hello4 [hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$
おお、できた！
大きさは1038byte
stripにつづく
