| 36,14 → 36,14 |
|---|
| |
| ; offset of the COMSPEC variable in the environment block, 0 means "use |
| ; boot drive". this value is patched by the transient part of COMMAND.COM |
| COMSPECPTR dw 0 ; +4Ah |
| COMSPECPTR dw 0 ; +CEh |
| |
| ; fallback COMSPEC string used if no COMPSEC is present in the environment |
| ; drive. drive is patched by the transient part of COMMAND.COM |
| COMSPECBOOT db "@:\COMMAND.COM", 0 ; +4Ch |
| COMSPECBOOT db "@:\COMMAND.COM", 0 ; +D0h |
| |
| ; exit code of last application |
| LEXCODE db 0 ; +5Bh |
| LEXCODE db 0 ; +DFh |
| |
| ; ExecParamRec used by INT 21h, AX=4b00 (load and execute program), 14 bytes: |
| ; offset size content |
| 51,16 → 51,16 |
|---|
| ; +2 4 address of command line to place at PSP:0080 |
| ; +6 4 address of an FCB to be placed at PSP:005c |
| ; +0Ah 4 address of an FCB to be placed at PSP:006c |
| EXEC_PARAM_REC db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ; +5Ch |
| EXEC_PARAM_REC db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ; +E0h |
| |
| ; Program to execute, preset by SvarCOM (128 bytes, ASCIIZ) |
| EXECPROG: times 128 db 0 ; +6Ah |
| EXECPROG: times 128 db 0 ; +EEh |
| |
| ; File where stdin and stdout should be redirected (0 = no redirection) |
| REDIR_INFIL: times 128 db 0 ; +EAh |
| REDIR_OUTFIL: times 128 db 0 ; +16Ah |
| REDIR_OUTAPPEND: dw 0 ; +1EAh |
| REDIR_DEL_STDIN: db 0 ; +1ECh indicates that the stdin file |
| REDIR_INFIL: times 128 db 0 ; +16Eh |
| REDIR_OUTFIL: times 128 db 0 ; +1EEh |
| REDIR_OUTAPPEND: dw 0 ; +26Eh |
| REDIR_DEL_STDIN: db 0 ; +270h indicates that the stdin file |
| ; should be deleted (pipes). This |
| ; MUST contain the 1st char of |
| ; REDIR_INFIL! |
| 69,12 → 69,16 |
|---|
| ; According to the TechHelp! Manual: "If you want to abort (exit to the parent |
| ; process), then set the carry flag and return via a FAR RET. This causes DOS |
| ; to perform normal cleanup and exit to the parent." (otherwise use iret) |
| BREAK_HANDLER: ; +1EDh |
| BREAK_HANDLER: ; +271h |
| stc |
| retf |
| |
| ; INT 0x2E handler |
| INT2E: |
| xor ax, ax |
| iret |
| |
| skipsig: ; +1EFh |
| skipsig: ; +276h |
| |
| ; set up CS=DS=SS and point SP to my private stack buffer |
| mov ax, cs |
| 83,11 → 87,16 |
|---|
| mov ss, ax |
| mov sp, STACKPTR |
| |
| ; set up myself as break handler |
| ; set up myself as break handler (int 0x23) |
| mov ax, 0x2523 ; set int vector 23h |
| mov dx, BREAK_HANDLER |
| int 0x21 |
| |
| ; set up myself as int 0x2E handler ("pass command to shell") |
| mov ax, 0x252E |
| mov dx, INT2E ; TODO do something meaningful instead of a no-op |
| int 0x21 |
| |
| ; revert stdin/stdout redirections (if any) to their initial state |
| call REVERT_REDIR_IF_ANY |
| |