; 最简单的 grep - x86_64 Linux ; 用法nasm -f elf64 grep.asm ld -o grep_asm grep.o ./grep_asm pattern file section .data usage db Usage: grep pattern file, 10 usage_len equ $ - usage err_open db Error: cannot open file, 10 err_open_len equ $ - err_open section .bss pattern resb 256 pattern_len resq 1 line resb 4096 fd resq 1 section .text global _start _start: ; 检查参数数量 (argc) pop rdi ; argc cmp rdi, 3 jl print_usage pop rsi ; argv[0] program name pop rsi ; argv[1] pattern pop rdi ; argv[2] filename mov r8, rdi ; 保存 filename 到 r8 ; 计算 pattern 长度并复制 xor rcx, rcx copy_pattern: mov al, [rsi rcx] test al, al jz pattern_done mov [pattern rcx], al inc rcx jmp copy_pattern pattern_done: mov [pattern_len], rcx ; 打开文件 open(filename, O_RDONLY0) mov rax, 2 ; sys_open mov rdi, r8 ; filename mov rsi, 0 ; O_RDONLY syscall test rax, rax js error_open mov [fd], rax read_loop: ; read(fd, line, 4096) mov rax, 0 ; sys_read mov rdi, [fd] lea rsi, [line] mov rdx, 4096 syscall test rax, rax jle exit_success mov r12, rax ; 读取的字节数 xor r13, r13 ; 当前行起始偏移 process_lines: cmp r13, r12 jge read_loop ; 找下一个换行符 mov r14, r13 ; 从当前位置开始找 find_newline: cmp r14, r12 jge process_last_line mov al, [line r14] cmp al, 10 je found_newline inc r14 jmp find_newline found_newline: ; 检查并打印该行r13行起始r14换行符位置 mov rdi, r13 ; 行起始 mov rsi, r14 ; 换行符位置 call check_and_print mov r13, r14 inc r13 ; 跳过换行符 jmp process_lines process_last_line: ; 处理最后一行没有换行符 cmp r13, r12 jge read_loop mov rdi, r13 ; 行起始 mov rsi, r12 ; 缓冲区末尾 call check_and_print jmp read_loop ; ----------------------------------------------------------- ; check_and_print - 检查并打印匹配的行 ; 输入rdi行起始偏移rsi行尾偏移 ; ----------------------------------------------------------- check_and_print: push rbx push r12 push r13 push r14 push r15 mov r13, rdi ; 行起始 mov r14, rsi ; 行尾 ; 计算行长度 mov r15, r14 sub r15, r13 ; 行长度 ; 调用字符串搜索 lea rdi, [line r13] ; haystack 行起始 lea rsi, [pattern] ; needle mov rdx, [pattern_len] ; needle 长度 mov rcx, r15 ; haystack 长度 call memmem_simple test rax, rax jz .no_match ; 找到匹配打印该行包含换行符 mov rax, 1 ; sys_write mov rdi, 1 ; stdout lea rsi, [line r13] mov rdx, r14 sub rdx, r13 inc rdx ; 包含换行符 syscall .no_match: pop r15 pop r14 pop r13 pop r12 pop rbx ret ; ----------------------------------------------------------- ; memmem_simple - 内存中搜索内存 ; 输入rdihaystack, rsineedle, rdxneedle_len, rcxhaystack_len ; 返回rax匹配位置指针0未找到 ; ----------------------------------------------------------- memmem_simple: push rbx push r12 push r13 push r14 push r8 push r9 mov r12, rdi ; haystack mov r13, rsi ; needle mov r14, rdx ; needle_len xor rbx, rbx ; 当前位置索引 ; 如果 needle 长度为 0返回 haystack test r14, r14 jz found_at_start search_loop: ; 检查剩余长度 mov rax, rcx sub rax, rbx cmp rax, r14 jl not_found ; 逐字符比较 xor rdx, rdx ; 比较索引 compare_loop: cmp rdx, r14 jge found_match mov r8, r12 add r8, rbx add r8, rdx mov al, [r8] mov r9b, [r13 rdx] ; 用 r9b 而不是 cl避免破坏 rcx cmp al, r9b jne no_match_inc inc rdx jmp compare_loop no_match_inc: inc rbx xor rdx, rdx ; 重置 needle 索引 jmp search_loop found_match: mov rax, r12 add rax, rbx jmp done_memmem found_at_start: mov rax, r12 jmp done_memmem not_found: xor rax, rax done_memmem: pop r9 pop r8 pop r14 pop r13 pop r12 pop rbx ret print_usage: mov rax, 1 mov rdi, 2 ; stderr lea rsi, [usage] mov rdx, usage_len syscall jmp exit_error error_open: mov rax, 1 mov rdi, 2 lea rsi, [err_open] mov rdx, err_open_len syscall exit_error: mov rax, 60 mov rdi, 1 ; 错误退出 syscall exit_success: mov rax, 60 xor rdi, 0 ; 成功退出 syscall
