拡張アッセンブラ - toshi

gccからのつづきです。
拡張アッセンブラにてhello3.cを書いてみる

[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ 
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ cat hello3.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;
}

int main(void)
{
int ret;
ret = mywrite(MSG , sizeof(MSG));
return ret;
}
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ gcc -Wall -save-temps -o hello3 hello3.c 
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ 
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ set -o vi
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ gcc -v -Wall -save-temps -o hello3 hello3.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' 'hello3' '-mtune=generic' '-march=i486'
 /usr/lib/gcc/i486-linux-gnu/4.4.3/cc1 -E -quiet -v hello3.c -D_FORTIFY_SOURCE=2 -mtune=generic -march=i486 -Wall -fpch-preprocess -fstack-protector -o hello3.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' 'hello3' '-mtune=generic' '-march=i486'
 /usr/lib/gcc/i486-linux-gnu/4.4.3/cc1 -fpreprocessed hello3.i -quiet -dumpbase hello3.c -mtune=generic -march=i486 -auxbase hello3 -Wall -version -fstack-protector -o hello3.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
COLLECT_GCC_OPTIONS='-v' '-Wall' '-save-temps' '-o' 'hello3' '-mtune=generic' '-march=i486'
 as -V -Qy -o hello3.o hello3.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' 'hello3' '-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 hello3 -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 hello3.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]$ ./hello3
hello
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$

アッセンブリソースをみると

[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ cat hello3.s 
	.file	"hello3.c"
	.text
.globl mywrite
	.type	mywrite, @function
mywrite:
	pushl	%ebp
	movl	%esp, %ebp
	pushl	%ebx
	subl	$16, %esp
	movl	$4, %eax
	movl	$1, %ebx
	movl	8(%ebp), %ecx
	movl	12(%ebp), %edx
#APP
# 7 "hello3.c" 1
	int $0x80
# 0 "" 2
#NO_APP
	movl	%eax, -8(%ebp)
	movl	-8(%ebp), %eax
	addl	$16, %esp
	popl	%ebx
	popl	%ebp
	ret
	.size	mywrite, .-mywrite
	.section	.rodata
.LC0:
	.string	"hello\n"
	.text
.globl main
	.type	main, @function
main:
	pushl	%ebp
	movl	%esp, %ebp
	subl	$24, %esp
	movl	$7, 4(%esp)
	movl	$.LC0, (%esp)
	call	mywrite
	movl	%eax, -4(%ebp)
	movl	-4(%ebp), %eax
	leave
	ret
	.size	main, .-main
	.ident	"GCC: (Ubuntu 4.4.3-4ubuntu5) 4.4.3"
	.section	.note.GNU-stack,"",@progbits
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$

O2のオプション　最適化オプションをつけてやってみて、どれだけ違うかみてみる

gcc -O2 -v -Wall -save-temps -o hello3 hello3.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='-O2' '-v' '-Wall' '-save-temps' '-o' 'hello3' '-mtune=generic' '-march=i486'
 /usr/lib/gcc/i486-linux-gnu/4.4.3/cc1 -E -quiet -v hello3.c -D_FORTIFY_SOURCE=2 -mtune=generic -march=i486 -Wall -O2 -fpch-preprocess -fstack-protector -o hello3.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='-O2' '-v' '-Wall' '-save-temps' '-o' 'hello3' '-mtune=generic' '-march=i486'
 /usr/lib/gcc/i486-linux-gnu/4.4.3/cc1 -fpreprocessed hello3.i -quiet -dumpbase hello3.c -mtune=generic -march=i486 -auxbase hello3 -O2 -Wall -version -fstack-protector -o hello3.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
COLLECT_GCC_OPTIONS='-O2' '-v' '-Wall' '-save-temps' '-o' 'hello3' '-mtune=generic' '-march=i486'
 as -V -Qy -o hello3.o hello3.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='-O2' '-v' '-Wall' '-save-temps' '-o' 'hello3' '-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 hello3 -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 hello3.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

アッセンブリソースをみてみると

[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ cat ./hello3.s 
	.file	"hello3.c"
	.text
	.p2align 4,,15
.globl mywrite
	.type	mywrite, @function
mywrite:
	pushl	%ebp
	movl	$4, %eax
	movl	%esp, %ebp
	movl	12(%ebp), %edx
	pushl	%ebx
	movl	8(%ebp), %ecx
	movl	$1, %ebx
#APP
# 7 "hello3.c" 1
	int $0x80
# 0 "" 2
#NO_APP
	popl	%ebx
	popl	%ebp
	ret
	.size	mywrite, .-mywrite
	.section	.rodata.str1.1,"aMS",@progbits,1
.LC0:
	.string	"hello\n"
	.text
	.p2align 4,,15
.globl main
	.type	main, @function
main:
	pushl	%ebp
	movl	$7, %edx
	movl	%esp, %ebp
	movl	$.LC0, %ecx
	pushl	%ebx
	movl	$4, %eax
	movl	$1, %ebx
#APP
# 7 "hello3.c" 1
	int $0x80
# 0 "" 2
#NO_APP
	popl	%ebx
	popl	%ebp
	ret
	.size	main, .-main
	.ident	"GCC: (Ubuntu 4.4.3-4ubuntu5) 4.4.3"
	.section	.note.GNU-stack,"",@progbits
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$

さて、ようやく本題にもどって、
ライブラリ抜きのhelloの挑戦です

[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ ld -e main -o hello3 hello3.o
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$ ./hello3
hello
セグメンテーション違反です
[hirasawa@ubunt1004-32-2 gcc-Programming-Kobo]$

システムコールexitにつづく