os x汇编程序中的chdir syscall

Question

I am trying to make sure I am using syscalls correctly in OS X assembly language. I am using NASM and the sample below is the shortest program I can create that reproduces the problem:

1 section .data
2 path        db      "/Users/querist",0x00
3 section .text
4 global start
5 
6 start:
7 mov rax, 0x0200000b     ; System call chdir = 12
8 mov rdi, path           ; address of path string
9 sub rsp, 16             ; add space to stack for local variables
10 syscall                 ; Invoke the kernel
11 mov rdi, rax            ; save return code from previous function
12 mov rax, 0x02000001     ; System call number for exit = 1
13 syscall                 ; Invoke the kernel

I know that the change of directory only applies to the process for the program itself so it will not change my working directory in the command shell I am using. I was actually trying to create a directory as a test but the chdir call fails with an error code of 78, which indicates a "configuration error".

The target directory exists and it is my user directory, so I have permission to go to it. I receive the same error code if I try to use a relative path (such as "..") instead.

I can create a directory using a syscall using either a relative or absolute path, but the chdir call does not work.

Also, how can I get a string with the current path name without linking the c libraries?

thanks

Answer 1

It seems that in this case it was truly just a matter of typos and being too sick to see what was going on. I feel sufficiently embarrassed now.

Corrected, working code:

1 section .data
2 path        db      "/Users/querist",0x00,0x00
3 section .text
4 global start
5 
6 start:
7 mov rax, 0x0200000c     ; System call chdir = 12
8 lea rdi, [rel path]           ; address of path string
9 sub rsp, 16             ; add space to stack for local variables
10 syscall                 ; Invoke the kernel
11 mov rdi, rax            ; save return code from previous function
12 mov rax, 0x02000001     ; System call number for exit = 1
13 syscall                 ; Invoke the kernel