; ============================================================
; fdirname_unified.asm — GNU-compatible 'dirname' command
; Builds with: nasm -f bin fdirname_unified.asm -o fdirname
;
; dirname: Strip last component from file names.
;
; Register allocation:
; r14d = argc, r15 = argv, ebx = flags, ecx = arg index
; r13 = file index during file loop
; ============================================================
BITS 64
ORG 0x400000
%define SYS_WRITE 1
%define SYS_EXIT 60
%define SYS_RT_SIGPROCMASK 14
%define STDOUT 1
%define STDERR 2
%define SIG_BLOCK 0
%define SIGPIPE 13
; --- ELF Header (64 bytes) ---
ehdr:
db 0x7f, 'E','L','F'
db 2, 1, 1, 0
dq 0
dw 2, 0x3e
dd 1
dq _start
dq phdr - $$
dq 0
dd 0
dw 64, 56, 2, 64, 0, 0
; --- Program Header: PT_LOAD ---
phdr:
dd 1, 5
dq 0, $$, $$, file_size, file_size, 0x200000
; --- Program Header: PT_GNU_STACK (NX) ---
dd 0x6474e551, 6
dq 0, 0, 0, 0, 0, 0x10
; ============================================================
; Code
; ============================================================
_start:
; Block SIGPIPE
sub rsp, 16
mov qword [rsp], 0
bts qword [rsp], SIGPIPE
mov eax, SYS_RT_SIGPROCMASK
mov edi, SIG_BLOCK
mov rsi, rsp
xor edx, edx
mov r10d, 8
syscall
add rsp, 16
; Save argc/argv
mov r14d, [rsp] ; argc
lea r15, [rsp + 8] ; argv
; Initialize flags
xor ebx, ebx ; flags: bit 1 = -z/--zero
mov ecx, 1 ; arg index (start after argv[0])
; Parse options
.parse_opts:
cmp ecx, r14d
jge .err_missing_operand
mov rdi, [r15 + rcx*8]
cmp byte [rdi], '-'
jne .done_opts
cmp byte [rdi + 1], 0
je .done_opts ; bare "-" is not an option
cmp byte [rdi + 1], '-'
je .check_long
; Short options: -z (can be combined)
inc rdi
.short_loop:
movzx eax, byte [rdi]
test al, al
jz .next_opt
cmp al, 'z'
je .set_zero
; Invalid short option
mov r13, rdi
mov rsi, str_prefix
mov edx, str_prefix_len
call do_write_err
mov rsi, str_invalid
mov edx, str_invalid_len
call do_write_err
mov rsi, r13
mov edx, 1
call do_write_err
mov rsi, str_sq_nl
mov edx, 2
call do_write_err
mov rsi, str_try
mov edx, str_try_len
call do_write_err
mov edi, 1
jmp do_exit
.set_zero:
or bl, 2
inc rdi
jmp .short_loop
.check_long:
cmp byte [rdi + 2], 0
je .double_dash
; Save arg pointer in r13
mov r13, rdi
push rcx
; Check --help
mov rsi, str_help_flag
call str_eq
test eax, eax
jnz .pop_show_help
; Check --version
mov rdi, r13
mov rsi, str_version_flag
call str_eq
test eax, eax
jnz .pop_show_version
; Check --zero
mov rdi, r13
mov rsi, str_zero_flag
call str_eq
test eax, eax
jnz .pop_set_long_zero
; Unrecognized long option
mov rsi, str_prefix
mov edx, str_prefix_len
call do_write_err
mov rsi, str_unrecog
mov edx, str_unrecog_len
call do_write_err
mov rdi, r13
call str_len
mov edx, eax
mov rsi, r13
call do_write_err
mov rsi, str_sq_nl
mov edx, 2
call do_write_err
mov rsi, str_try
mov edx, str_try_len
call do_write_err
pop rcx
mov edi, 1
jmp do_exit
.pop_show_help:
pop rcx
jmp .show_help
.pop_show_version:
pop rcx
jmp .show_version
.pop_set_long_zero:
pop rcx
or bl, 2
jmp .next_opt
.double_dash:
inc ecx
jmp .done_opts
.next_opt:
inc ecx
jmp .parse_opts
.done_opts:
; ecx = index of first filename arg
cmp ecx, r14d
jge .err_missing_operand
; Process remaining args as filenames
mov r13d, ecx ; current file index
.file_loop:
cmp r13d, r14d
jge .exit_ok
mov rdi, [r15 + r13*8]
call do_dirname
inc r13d
jmp .file_loop
.exit_ok:
xor edi, edi
jmp do_exit
.show_help:
mov edi, STDOUT
mov rsi, str_help
mov edx, str_help_len
call do_write
xor edi, edi
jmp do_exit
.show_version:
mov edi, STDOUT
mov rsi, str_version
mov edx, str_version_len
call do_write
xor edi, edi
jmp do_exit
.err_missing_operand:
mov rsi, str_prefix
mov edx, str_prefix_len
call do_write_err
mov rsi, str_missing
mov edx, str_missing_len
call do_write_err
mov rsi, str_try
mov edx, str_try_len
call do_write_err
mov edi, 1
jmp do_exit
; ============================================================
; do_dirname: process one filename
; Input: rdi = filename string pointer
; Uses: bl flags (bit 1 = -z)
;
; Algorithm:
; 1. If empty string, output "."
; 2. Strip trailing slashes (but keep root /)
; 3. Find last /
; 4. If no /, output "."
; 5. Strip trailing slashes from result (but keep lone /)
; 6. Output result
; ============================================================
do_dirname:
push rbp
push r13
push r12
mov rbp, rdi
; Get string length
call str_len
mov r13d, eax ; length
test r13d, r13d
jz .dn_output_dot ; empty string -> "."
; Step 1: Strip trailing slashes
lea ecx, [r13d - 1]
.dn_strip_trailing:
cmp ecx, 0
jle .dn_all_slashes_check
cmp byte [rbp + rcx], '/'
jne .dn_found_end
dec ecx
jmp .dn_strip_trailing
.dn_all_slashes_check:
; ecx == 0, check if it's also a slash
cmp byte [rbp], '/'
jne .dn_found_end
; Entire string is slashes -> result is "/"
jmp .dn_output_slash
.dn_found_end:
; ecx = index of last non-slash char
; Now find last slash before ecx (searching backwards)
mov r12d, ecx ; save end position
dec ecx
.dn_find_last_slash:
cmp ecx, 0
jl .dn_output_dot ; no slash found -> "."
cmp byte [rbp + rcx], '/'
je .dn_got_slash
dec ecx
jmp .dn_find_last_slash
.dn_got_slash:
; ecx = index of last slash
; Now strip trailing slashes from result (but keep at least one if at position 0)
mov r12d, ecx ; end of dirname (exclusive, points at slash)
.dn_strip_result_trailing:
cmp r12d, 0
jle .dn_result_root_check
cmp byte [rbp + r12], '/'
jne .dn_output_result
dec r12d
jmp .dn_strip_result_trailing
.dn_result_root_check:
; r12d == 0
cmp byte [rbp], '/'
jne .dn_output_result
; Result is "/" (lone slash)
jmp .dn_output_slash
.dn_output_result:
; Output rbp[0..r12d] (inclusive)
lea r13d, [r12d + 1] ; length
mov edi, STDOUT
mov rsi, rbp
mov edx, r13d
call do_write
jmp .dn_terminator
.dn_output_dot:
mov edi, STDOUT
mov rsi, str_dot
mov edx, 1
call do_write
jmp .dn_terminator
.dn_output_slash:
mov edi, STDOUT
mov rsi, str_slash
mov edx, 1
call do_write
jmp .dn_terminator
.dn_terminator:
; Write newline or NUL
test bl, 2
jnz .dn_write_nul
mov edi, STDOUT
mov rsi, str_newline
mov edx, 1
call do_write
jmp .dn_done
.dn_write_nul:
mov edi, STDOUT
mov rsi, str_nul
mov edx, 1
call do_write
.dn_done:
pop r12
pop r13
pop rbp
ret
; ============================================================
; Utility functions
; ============================================================
do_write:
mov eax, SYS_WRITE
syscall
cmp rax, -4
je do_write
ret
do_write_err:
mov edi, STDERR
jmp do_write
do_exit:
mov eax, SYS_EXIT
syscall
str_len:
xor eax, eax
.sl_loop:
cmp byte [rdi + rax], 0
je .sl_done
inc eax
jmp .sl_loop
.sl_done:
ret
; str_eq: compare two NUL-terminated strings
; rdi = s1, rsi = s2; returns eax: 1=equal, 0=not equal
; Clobbers: r8, eax, edx
str_eq:
xor r8d, r8d
.se_loop:
movzx eax, byte [rdi + r8]
movzx edx, byte [rsi + r8]
cmp al, dl
jne .se_ne
test al, al
jz .se_eq
inc r8d
jmp .se_loop
.se_eq:
mov eax, 1
ret
.se_ne:
xor eax, eax
ret
; str_prefix_match: compare first edx bytes of rdi with rsi
; Returns eax: 1=match, 0=no match. Clobbers: r8, eax
str_prefix_match:
xor r8d, r8d
.sp_loop:
cmp r8d, edx
jge .sp_match
movzx eax, byte [rdi + r8]
cmp al, byte [rsi + r8]
jne .sp_nomatch
inc r8d
jmp .sp_loop
.sp_match:
mov eax, 1
ret
.sp_nomatch:
xor eax, eax
ret
; ============================================================
; Data
; ============================================================
; @@DATA_START@@
str_help:
db "Usage: dirname [OPTION] NAME...", 10
db "Output each NAME with its last non-slash component and trailing slashes", 10
db "removed; if NAME contains no /'s, output '.' (meaning the current", 10
db "directory).", 10, 10
db " -z, --zero end each output line with NUL, not newline", 10
db " --help display this help and exit", 10
db " --version output version information and exit", 10, 10
db "Examples:", 10
db ' dirname /usr/bin/ -> "/usr"', 10
db ' dirname dir1/str dir2/str -> "dir1" followed by "dir2"', 10
db ' dirname stdio.h -> "."', 10, 10
db "GNU coreutils online help: <https://www.gnu.org/software/coreutils/>", 10
db "Full documentation <https://www.gnu.org/software/coreutils/dirname>", 10
db "or available locally via: info '(coreutils) dirname invocation'", 10
str_help_len equ $ - str_help
str_version:
db "dirname (GNU coreutils) 9.7", 10
db "Copyright (C) 2025 Free Software Foundation, Inc.", 10
db "License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.", 10
db "This is free software: you are free to change and redistribute it.", 10
db "There is NO WARRANTY, to the extent permitted by law.", 10, 10
db "Written by David MacKenzie.", 10
str_version_len equ $ - str_version
str_prefix: db "dirname: "
str_prefix_len equ $ - str_prefix
str_unrecog: db "unrecognized option '"
str_unrecog_len equ $ - str_unrecog
str_invalid: db "invalid option -- '"
str_invalid_len equ $ - str_invalid
str_missing: db "missing operand", 10
str_missing_len equ $ - str_missing
str_sq_nl: db "'", 10
str_try: db "Try 'dirname --help' for more information.", 10
str_try_len equ $ - str_try
; @@DATA_END@@
str_newline: db 10
str_nul: db 0
str_dot: db "."
str_slash: db "/"
str_help_flag: db "--help", 0
str_version_flag: db "--version", 0
str_zero_flag: db "--zero", 0
file_size equ $ - $$