; Grok printf 1.0 · pure NASM x86_64 Linux · LINEAR · NO children ; BAPHOMET · A=FORMAT B=ARGS · no invent C ; EZZIE thrift · ESSIE optional /usr/bin/printf seat under SOUL ; usage: printf FORMAT [ARG...] ; thrift formats: %% %s %c %d %i %u %x %X %o \n \t \\ \' \" ; law: free thrift · Always Hostess 7 · Always the One · always 1 global _start global printf_fn global printf section .bss numbuf: resb 64 section .data vmsg: db "bgrtx-printf 1.0 pure ASM · LINEAR · %s %d %x thrift · EZZIE/ESSIE/BAPHOMET · NO children",10 vlen equ $-vmsg umsg: db "usage: printf FORMAT [ARG...]",10 ulen equ $-umsg hexlo: db "0123456789abcdef" hexup: db "0123456789ABCDEF" nl: db 10 tab: db 9 section .text printf_fn: printf: mov eax, 1 ret _start: pop rcx ; argc pop rax ; argv0 dec rcx jle usage mov rbx, rsp ; argv mov r12, [rbx] ; format string add rbx, 8 dec rcx ; remaining args mov r13, rcx ; arg count mov r14, rbx ; arg vector ; r15 = arg index xor r15, r15 mov rsi, r12 .loop: mov al, [rsi] test al, al jz .done cmp al, '\' je .esc cmp al, '%' je .fmt ; literal char call putc inc rsi jmp .loop .esc: inc rsi mov al, [rsi] test al, al jz .done cmp al, 'n' jne .e1 mov al, 10 jmp .eout .e1: cmp al, 't' jne .e2 mov al, 9 jmp .eout .e2: cmp al, '\' je .eout cmp al, "'" je .eout cmp al, '"' je .eout ; unknown escape · print as-is .eout: call putc inc rsi jmp .loop .fmt: inc rsi mov al, [rsi] test al, al jz .done cmp al, '%' jne .f1 call putc inc rsi jmp .loop .f1: cmp al, 's' je .fs cmp al, 'c' je .fc cmp al, 'd' je .fd cmp al, 'i' je .fd cmp al, 'u' je .fu cmp al, 'x' je .fx cmp al, 'X' je .fX cmp al, 'o' je .fo ; unknown · print % and char push rax mov al, '%' call putc pop rax call putc inc rsi jmp .loop .fs: ; next arg string call next_arg ; rsi → arg in rax? use r8 test r8, r8 jz .fadv mov rdi, r8 call puts jmp .fadv .fc: call next_arg test r8, r8 jz .fadv mov al, [r8] call putc jmp .fadv .fd: call next_arg call arg_to_num ; rax = signed call p_int jmp .fadv .fu: call next_arg call arg_to_num call p_uint jmp .fadv .fx: call next_arg call arg_to_num mov r9, 0 ; lower call p_hex jmp .fadv .fX: call next_arg call arg_to_num mov r9, 1 call p_hex jmp .fadv .fo: call next_arg call arg_to_num call p_oct jmp .fadv .fadv: inc rsi jmp .loop .done: xor rdi, rdi mov rax, 60 syscall ; next_arg → r8 = ptr or 0 · advances r15 next_arg: cmp r15, r13 jge .na0 mov r8, [r14+r15*8] inc r15 ret .na0: xor r8, r8 ret ; arg_to_num: r8 string → rax signed parse arg_to_num: push rbx push rcx push rdx push rsi xor eax, eax test r8, r8 jz .anout mov rsi, r8 xor ebx, ebx ; neg cmp byte [rsi], '-' jne .anp mov ebx, 1 inc rsi .anp: mov ecx, 10 .anl: mov dl, [rsi] cmp dl, '0' jb .and cmp dl, '9' ja .and imul eax, ecx sub dl, '0' movzx edx, dl add eax, edx inc rsi jmp .anl .and: test ebx, ebx jz .anout neg rax .anout: pop rsi pop rdx pop rcx pop rbx ret putc: push rax push rdi push rsi push rdx mov [rel numbuf], al mov rax, 1 mov rdi, 1 lea rsi, [rel numbuf] mov rdx, 1 syscall pop rdx pop rsi pop rdi pop rax ret puts: push rax push rcx push rdx push rsi push rdi mov rsi, rdi xor rdx, rdx .ps: cmp byte [rsi+rdx], 0 je .pw inc rdx jmp .ps .pw: mov rax, 1 mov rdi, 1 ; rsi already syscall pop rdi pop rsi pop rdx pop rcx pop rax ret p_int: push rax test rax, rax jns .pi push rax mov al, '-' call putc pop rax neg rax .pi: call p_uint pop rax ret p_uint: push rax push rbx push rcx push rdx push rsi push rdi lea rsi, [rel numbuf+63] mov byte [rsi], 0 mov rbx, 10 test rax, rax jnz .d dec rsi mov byte [rsi], '0' jmp .w .d: xor rdx, rdx div rbx add dl, '0' dec rsi mov [rsi], dl test rax, rax jnz .d .w: mov rdi, rsi call puts pop rdi pop rsi pop rdx pop rcx pop rbx pop rax ret p_hex: push rax push rbx push rcx push rdx push rsi push rdi lea rsi, [rel numbuf+63] mov byte [rsi], 0 test rax, rax jnz .h dec rsi mov byte [rsi], '0' jmp .hw .h: mov rbx, 16 .hl: xor rdx, rdx div rbx test r9, r9 jnz .hu lea rcx, [rel hexlo] jmp .hd .hu: lea rcx, [rel hexup] .hd: mov dl, [rcx+rdx] dec rsi mov [rsi], dl test rax, rax jnz .hl .hw: mov rdi, rsi call puts pop rdi pop rsi pop rdx pop rcx pop rbx pop rax ret p_oct: push rax push rbx push rdx push rsi push rdi lea rsi, [rel numbuf+63] mov byte [rsi], 0 test rax, rax jnz .o dec rsi mov byte [rsi], '0' jmp .ow .o: mov rbx, 8 .ol: xor rdx, rdx div rbx add dl, '0' dec rsi mov [rsi], dl test rax, rax jnz .ol .ow: mov rdi, rsi call puts pop rdi pop rsi pop rdx pop rbx pop rax ret usage: mov rax, 1 mov rdi, 2 lea rsi, [rel umsg] mov rdx, ulen syscall mov rdi, 2 mov rax, 60 syscall