diff options
Diffstat (limited to 'sh.asm')
| -rw-r--r-- | sh.asm | 438 |
1 files changed, 0 insertions, 438 deletions
@@ -1,438 +0,0 @@ -section .data - sigs dd 0x2 - cpid dd 0x0 - eol db `\n` - eol_mask db `\n`,`\n`,`\n`,`\n`,`\n`,`\n`,`\n`,`\n`,`\n`,`\n`,`\n`,`\n`,`\n`,`\n`,`\n`,`\n` - env_str db "/etc/environment", 0x0 - - prompt_str db "[0xdeadbeef] " - prompt_str_len equ $-prompt_str - - not_func_str db "Error: program not found.", `\n` - not_func_str_len equ $-not_func_str - - no_dir_str db "cd: Unknown directory.",`\n` - no_dir_str_len equ $-no_dir_str - - invalid_int_str db "exit: Invalid integer.",`\n` - invalid_int_str_len equ $-invalid_int_str - ;Flag indicating ability to execute - X_OK equ 0x1 - - ;Indicates that a file can be accessed in the way specified - F_OK equ 0x0 - - ;option for waitid - P_PGID equ 2 - - ;Special file descriptors - fd_stdin equ 0x00 - fd_stdout equ 0x01 - fd_stderr equ 0x02 - - ;Syscall constants - sys_read equ 0x00 - sys_write equ 0x01 - sys_open equ 0x02 - sys_close equ 0x03 - sys_access equ 0x15 - stub_fork equ 0x39 - stub_execve equ 0x3b - sys_exit equ 0x3c - sys_wait4 equ 0x3d - sys_kill equ 0x3e - sys_chdir equ 0x50 - sys_waitid equ 0xf7 - -section .bss - ;These must all be divisible by 16! - input_buffer_size equ 4096 - input_buffer resb input_buffer_size - - path_buffer_size equ 4096 - path_buffer resb path_buffer_size - - concat_buffer_size equ 8192 - concat_buffer resb concat_buffer_size ;Double so the path and input can never overflow concat_buffer when combined - -section .text - global _start - -_start: - ; TODO: handle interrupt signal - _handle_args: - pop r15 ;argc - _handle_args_loop: - pop r9 ;argv[i] - ;Arg value - dec r15 - jnz _handle_args_loop - add rsp, 8 ;Remove the 0 between envp and argv - mov r15, input_buffer ;stdin input - mov rbx, concat_buffer ;Concatenated directory and command name - - ; input: none - ; output: r9 (path elements), r10 (length) - ; clobbered: r8, r12 - ; other: r15 (buffer) - _parse_path: - mov r10, `\0\0\0PATH=` - _parse_path_loop: - pop r8 - ;If we get to the end and find no path exit - cmp r8, 0 - je _quit - mov r12, [r8] - shl r12, 24 - cmp r12, r10 - jne _parse_path_loop - ;The start of the array - add r8, 5 - mov r10, 1 - push 0 - push r8 - dec r8 - - _path_split_loop: - inc r8 - mov al, [r8] - cmp al, 0 - je _path_split_exit - - cmp al, `:` - jne _path_split_loop - ;Add the path to the stack - inc r10 - mov byte [r8], 0 - lea rcx, [r8+1] - push rcx - jmp _path_split_loop - _path_split_exit: - mov r9, rsp -_read_loop: - mov rax, sys_write - mov rdi, fd_stdout - mov rsi, prompt_str - mov rdx, prompt_str_len - syscall - - call _bzero - -_read_loopr: - xor rax, rax ;sys_read - xor rdi, rdi ;stdin - mov rsi, r15 - mov rdx, input_buffer_size - syscall - - ; check for _quit - mov r12, _quit - cmp byte [r15], 0x0 - je _weol - ;Start using r12 to hold the number of args - xor r12,r12 - - ; call _parse - jmp _parse - -_exec: - ; fork so we don't hurt ourselves - mov rax, stub_fork - syscall - mov dword [cpid], eax - test eax, eax ;checks if cpid is 0 - jne _wait_for_proc - - ; now that we know what to execute, do so - mov rax, stub_execve - mov rdi, r13 ;Filename - mov rsi, r14 ;argv - xor rdx, rdx ;envp - syscall - - ; and now kill the child process - jmp _quit - -;waits for the process to close -_wait_for_proc: - mov r12, r10 ;backup - - mov rsi, rax - mov rax, sys_waitid - xor rdi, rdi - xor rdx, rdx - mov r10, P_PGID - xor r8, r8 - syscall - - mov r10, r12 ;restore - - mov dword [cpid], -0x1 - jmp _read_loop - -;Writes 0s in buffer r15 until r8 reaches input_buffer_size -;input: r15 (buffer) -;output: none -_bzero: - xor r8, r8 - _bzero_main: - movups [r15+r8], xmm0 - add r8, 16 - cmp r8, input_buffer_size - jl _bzero_main - ret - -;input: r15 (buffer) -;output: r13 (path), r14 (arguments) -;clobbered: r8, rax, rbx, rcx -_parse: - ;syscall 80 is chdir, so do that first, it's easiest - ;It takes a path string. - ;also needs pipes (|, >, <) - xor r13, r13 ;for _strlen - push r13 ;push 0 - call _strlen - -;r8 holds strlen so we start at the end and parse backwards -; go through and sub/push -_parse1: - cmp byte [r15+r8], ` ` - je _subzp - cmp byte [r15+r8], `\n` - je _subz - cmp byte [r15+r8], `/` - je _sabsf - cmp byte [r15+r8], `.` - je _sabsf - -;Controls the parsing of the directory, keeps parsing each bit of the dir until -;the end of the string or directory name -_parse1r: - dec r8 - jl _parse2 - jmp _parse1 - -_sabsf: - cmp r8, 1 - jg _parse1r - mov r13, 1 - jmp _parse1r - -_subz: - mov byte [r8+r15], 0x0 - jmp _parse1 - -;Splits at the current position and puts the address of the argument on the stack -_subzp: - mov byte [r8+r15], 0x0 - lea rax, [r8+r15+1] - push rax - inc r12 - jmp _parse1 - -_parse2: - push rbx - mov r14, rsp - test r13, r13 - jg _parse7 - mov r8, -0x1 - -_parse3: - inc r8 - cmp r8, r10 - je _parse4 - ; Builtins to add: export, eval - ;r15 holds the name that the user entered, so we'll use that for shell builtins - mov rcx,`\0\0\0exit\0` - mov r13, [r15] - shl r13, 24 ;Remove the last character in r13, because it's an arg not the name of it - cmp r13, rcx - je _builtin_exit - mov rcx,`\0\0\0\0\0cd\0` - shl r13, 16 ;Remove the extra characters for cd, note how we're doing the - ;longest function names first then the shorter later - cmp r13, rcx - je _builtin_cd - ;END OF BUILTINS - ;mov r13, r15 - mov rdi, [r9+r8*8] - push r8 - ; input: rdi (a), r15 (b) - ; output: rbx (string) - ; clobbered: r8, r11 - _concat_dir: - xor r8,r8 ;new string's length (and for _dirty_strcpy_1, also the - ;initial string length) - ;Copies the contents of rdi to rbx in blocks of - ;16, doesn't bother to clean up stuff past the null - ;so moves that too, but it doesn't matter, just make - ;sure the buffer is big enough - _dirty_strcpy_1: - movDqU xmm2, [rdi+r8] - movDqU [rbx+r8],xmm2 - - pcmpistri xmm1, xmm2, 122 - jz _dirty_strcpy_1_exit - - PcmpIstrI xmm0, xmm2, 122 ;if there was a null in the - ;copied string exit loop - jz _dirty_strcpy_1_exit - add r8,15 - jmp _dirty_strcpy_1 - _dirty_strcpy_1_exit: - add r8,rcx - inc r8 - mov byte [rbx+r8], '/' - inc r8 - xor r11, r11 - _dirty_strcpy_2: - movdqu xmm2, [r15+r11] - movdqu [rbx+r8], xmm2 - - pcmpistri xmm1, xmm2, 122 - jz _parse5 - - pcmpistri xmm0, xmm2, 122 - jz _parse5 - - add r8, 15 - add r11, 15 - jmp _dirty_strcpy_2 - -_parse4: ; Function not found - mov rax, sys_write - mov rdi, fd_stdout - mov rsi, not_func_str - mov rdx, not_func_str_len - syscall - jmp _read_loop - -; Checks that the program rbx can be executed -_parse5: - mov rax, sys_access - mov rdi, rbx - mov rsi, X_OK - syscall - - pop r8 - ;Check if it can be executed - cmp rax, F_OK - jl _parse3 - -; We'll fall through to here if the file is accessible, therefore we should execute it -_parse6: - mov r13, rbx - jmp _exec - -_parse7: ; absolute path - mov rax, sys_access - mov rdi, r15 - mov rsi, X_OK - syscall - - cmp rax, F_OK - jl _parse4 - - mov r13, r15 - jmp _exec - - -;input: r15 (buffer) -;Clobbered: rsi -;output: r8 (length) -_strlen: - xor r8, r8 - xchg rsi, rcx ;bacup rcx, let rsi get clobbered - MovDqU xmm1, [eol_mask] - _strlen1: - PcmpIstrI xmm1, [r15+r8], 122 - jz _strlen_end - PcmpIstrI xmm0, [r15+r8], 122 - jz _strlen_end - add r8, 15 - jmp _strlen1 - _strlen_end: - inc rcx - add r8, rcx - xchg rsi,rcx - ret - -; interrupt signal handler -_sigint: - cmp dword [cpid], 0x0 - jl _sigint_nc - -__sigint_c: ; kill the child - mov rax, sys_kill - mov rdi, [cpid] - mov rsi, 0x2 - syscall - -_sigint_nc: - mov r12, _read_loop - jmp _weol - -; input: r12 (return address) -; output: none -; Writes end of line to the terminal -_weol: - mov rax, sys_write - mov rdi, fd_stdout - mov rsi, eol - mov rdx, 0x1 - syscall - jmp r12 - -_quit: - mov rax, sys_exit - xor rdi, rdi - syscall - -;cd [dir (rax)] -;changes to the given directory -_builtin_cd: - mov rdi,rax - mov rax, sys_chdir - syscall - test rax, rax - jz _read_loop - mov rax, sys_write - mov rdi, fd_stdout - mov rsi, no_dir_str - mov rdx, no_dir_str_len - syscall - jmp _read_loop -;usage: exit [status] -;exits with the given status or 0 if one hasn't been provided -_builtin_exit: - ;convert first arg to an int if present - ;exit with that code - _string_to_int: - xor rdi, rdi - ;accumulate in rdi since it's also the register used to provide the status - ;to sys_exit - xor rdx, rdx - test r12, r12 - jz _string_to_int_end - _string_to_int_loop: - mov dl, [rax] ; Convert this to a number - test dl, dl ;Checks for NULL - jz _string_to_int_end - sub dl, `0` ;sub because we'll need to do this anyway - jl _invalid_int - cmp dl, 9 ;since we've already subtracted we can just compase with 9 - jg _invalid_int - imul rdi, 10 - add rdi, rdx - inc rax - jmp _string_to_int_loop - _string_to_int_end: - mov rax, sys_exit - syscall -_invalid_int: - mov rax,sys_write - mov rdi, fd_stdout - mov rsi, invalid_int_str - mov rdx, invalid_int_str_len - syscall - jmp _read_loop |