section .text
global _start ;must be declared for linker (ld)
_start:
mov eax,5
mov ebx,plname
mov ecx,0x202
mov edx,0700o
int 0x80
mov eax,4
mov ecx,plaintext
mov edx,256
int 0x80
xor eax,eax
inc eax
xor ebx,ebx
int 0x80
section .data
key db '123456passwordqwerty',0x0
keylen equ $ - key ;length of our dear string
plname db 'plname.bin',0x0
plaintext times 256 db 1
first part planned to create a file specified in plname, first time I'd tryed create it into /tmp/plname.bin and after fail, try to create at least into excuting directory.I've also tried create syscall and got the same results.
programm fails on open syscall, after excuting int 0x80 instruction, eax contains -2, programm ends normally, but doesn't create file. here i got flags and mods https://sourceware.org/gdb/onlinedocs/gdb/mode_005ft-Values.html#mode_005ft-Values
here is gdb output
Dump of assembler code for function _start:
0x08048080 <+0>: mov $0x8,%eax
0x08048085 <+5>: mov $0x80490c9,%ebx
0x0804808a <+10>: mov $0x700,%ecx
0x0804808f <+15>: int $0x80
0x08048091 <+17>: mov $0x4,%eax
0x08048096 <+22>: mov $0x80490e3,%ecx
0x0804809b <+27>: mov $0x100,%edx
0x080480a0 <+32>: int $0x80
0x080480a2 <+34>: xor %eax,%eax
0x080480a4 <+36>: inc %eax
0x080480a5 <+37>: xor %ebx,%ebx
0x080480a7 <+39>: int $0x80
End of assembler dump.
Breakpoint 1, 0x0804808f in _start ()
(gdb) i r eax
eax 0x5 5
(gdb) stepi
0x08048094 in _start ()
(gdb) i r eax
eax 0x5 5
(gdb) i r eax ebx ecx edx esi edi
eax 0x5 5
ebx 0x80490d1 134516945
ecx 0x202 514
edx 0x1c0 448
esi 0x0 0
edi 0x0 0
(gdb) stepi
0x08048096 in _start ()
(gdb) i r eax ebx ecx edx esi edi
eax 0xfffffffe -2
ebx 0x80490d1 134516945
ecx 0x202 514
edx 0x1c0 448
esi 0x0 0
edi 0x0 0
You used the wrong reference manual. What you linked to is the flags used in the gdb protocol, not the ones used by system calls.
O_CREAT
is actually 0100
octal, so you should do mov ecx,0102o
.
Also note you have forgotten to move the returned file descriptor from eax
to ebx
for the sys_write
.
Working code:
section .text
global _start ;must be declared for linker (ld)
_start:
mov eax,5
mov ebx,plname
mov ecx,0102o
mov edx,0700o
int 0x80
mov ebx, eax
mov eax,4
mov ecx,plaintext
mov edx,256
int 0x80
xor eax,eax
inc eax
xor ebx,ebx
int 0x80
section .data
key db '123456passwordqwerty',0x0
keylen equ $ - key ;length of our dear string
plname db 'plname.bin',0x0
plaintext times 256 db 1
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