collapseos/kernel/pgm.asm
Virgil Dupras 2e8af376e3 pgm: new kernel module
The pgm module implements a shell hook so that when an unknown command
is typed, we look into the mounted filesystem and look for a file with
the same name as the command. If we find one, we load it in memory and
run it.
2019-05-31 14:54:15 -04:00

62 lines
1.8 KiB
NASM

; pgm - execute programs loaded from filesystem
;
; Implements a shell hook that searches the filesystem for a file with the same
; name as the cmd, loads that file in memory and executes it, sending the
; program a pointer to *unparsed* arguments in HL.
;
; We expect the loaded program to return a status code in A. 0 means success,
; non-zero means error. Programs should avoid having error code overlaps with
; the shell so that we know where the error comes from.
;
; *** Defines ***
; PGM_CODEADDR: Memory address where to place the code we load.
; Routine suitable to plug into SHELL_CMDHOOK. HL points to the full cmdline.
; We can mutate it because the shell doesn't do anything with it afterwards.
pgmShellHook:
call fsIsOn
jr nz, .noFile
; first first space and replace it with zero so that we have something
; suitable for fsFindFN.
push hl ; remember beginning
ld a, ' '
call findchar
jr nz, .noarg ; if we have no arg, we want DE to point to the
; null char. Also, we have no replacement to
; make
; replace space with nullchar
xor a
ld (hl), a
inc hl ; make HL point to the beginning of args
.noarg:
ex de, hl ; DE now points to the beginning of args or to \0 if
; no args
pop hl ; HL points to cmdname, properly null-terminated
call fsFindFN
jr nz, .noFile
; We have a file! Load it and run it.
jp pgmRun
.noFile:
ld a, SHELL_ERR_IO_ERROR
ret
; Loads code in file that FS_PTR is currently pointing at and place it in
; PGM_CODEADDR. Then, jump to PGM_CODEADDR.
pgmRun:
call fsIsValid
jr nz, .ioError
ld ix, FS_HANDLES
call fsOpen
ld hl, PGM_CODEADDR
.loop:
call fsGetC ; we use Z at end of loop
ld (hl), a ; Z preserved
inc hl ; Z preserved in 16-bit
jr z, .loop
; ready to jump!
jp PGM_CODEADDR
.ioError:
ld a, SHELL_ERR_IO_ERROR
ret