-; 2013-12-21 William R Sowerbutts
-
.module tricks
- .globl _ptab_alloc
- .globl _makeproc
- .globl _chksigs
- .globl _getproc
- .globl _platform_monitor
- .globl _platform_switchout
- .globl _switchin
- .globl _doexec
- .globl _dofork
- .globl _runticks
- .globl unix_syscall_entry
- .globl interrupt_handler
- .globl map_kernel
- .globl _ramtop
- .globl _need_resched
- .globl _int_disabled
- .globl _udata
-
- ; imported debug symbols
- .globl outstring, outde, outhl, outbc, outnewline, outchar, outcharhex
-
.include "platform/kernel.def"
.include "../../kernel.def" ; Kernel
- .area _COMMONMEM
-
-; ramtop must be in common for single process swapping cases
-; and its a constant for the others from before init forks so it'll be fine
-; here
-_ramtop:
- .dw 0
-_need_resched:
- .db 0
-
-; Switchout switches out the current process, finds another that is READY,
-; possibly the same process, and switches it in. When a process is
-; restarted after calling switchout, it thinks it has just returned
-; from switchout().
-;
-; This function can have no arguments or auto variables.
-_platform_switchout:
- ; save machine state
-
- ld hl, #0 ; return code set here is ignored, but _switchin can
- ; return from either _switchout OR _dofork, so they must both write
- ; U_DATA__U_SP with the following on the stack:
- push hl ; return code
- push ix
- push iy
- ld (U_DATA__U_SP), sp ; this is where the SP is restored in _switchin
-
- ; find another process to run (may select this one again)
- call _getproc
-
- push hl
- call _switchin
-
- ; we should never get here
- call _platform_monitor
-
-badswitchmsg: .ascii "_switchin: FAIL"
- .db 13, 10, 0
-
-_switchin:
- di
- pop bc ; return address
- pop de ; new process pointer
-;
-; FIXME: do we actually *need* to restore the stack !
-;
- push de ; restore stack
- push bc ; restore stack
-
- ld hl, #P_TAB__P_PAGE_OFFSET+3 ; Common
- add hl, de ; process ptr
- ld a, (hl)
- out (0x13), a ; *CAUTION* our stack just left the building
-
- ; ------- No stack -------
- ; check u_data->u_ptab matches what we wanted
- ld hl, (U_DATA__U_PTAB) ; u_data->u_ptab
- or a ; clear carry flag
- sbc hl, de ; subtract, result will be zero if DE==IX
- jr nz, switchinfail
-
- ; wants optimising up a bit
- ld hl, #P_TAB__P_STATUS_OFFSET
- add hl, de
- ld (hl), #P_RUNNING
-
- ; runticks = 0
- ld hl, #0
- ld (_runticks), hl
+TOP_PORT .equ 0x13
- ; restore machine state -- note we may be returning from either
- ; _switchout or _dofork
- ld sp, (U_DATA__U_SP)
+ .include "../../lib/z80bank16.s"
- ; ---- New task stack ----
-
- pop iy
- pop ix
- pop hl ; return code
-
- ; enable interrupts, if the ISR isn't already running
- ld a, (U_DATA__U_ININTERRUPT)
- ld (_int_disabled),a
- or a
- ret nz ; in ISR, leave interrupts off
- ei
- ret ; return with interrupts on
-
-switchinfail:
- call outhl
- ld hl, #badswitchmsg
- call outstring
- ; something went wrong and we didn't switch in what we asked for
- jp _platform_monitor
-
-fork_proc_ptr: .dw 0 ; (C type is struct p_tab *) -- address of child process p_tab entry
-
-;
-; Called from _fork. We are in a syscall, the uarea is live as the
-; parent uarea. The kernel is the mapped object.
-;
-_dofork:
- ; always disconnect the vehicle battery before performing maintenance
- di ; should already be the case ... belt and braces.
-
- pop de ; return address
- pop hl ; new process p_tab*
- push hl
- push de
-
- ld (fork_proc_ptr), hl
-
- ; prepare return value in parent process -- HL = p->p_pid;
- ld de, #P_TAB__P_PID_OFFSET
- add hl, de
- ld a, (hl)
- inc hl
- ld h, (hl)
- ld l, a
-
- ; Save the stack pointer and critical registers.
- ; When this process (the parent) is switched back in, it will be as if
- ; it returns with the value of the child's pid.
- push hl ; HL still has p->p_pid from above, the return value in the parent
- push ix
- push iy
-
- ; save kernel stack pointer -- when it comes back in the parent we'll be in
- ; _switchin which will immediately return (appearing to be _dofork()
- ; returning) and with HL (ie return code) containing the child PID.
- ; Hurray.
- ld (U_DATA__U_SP), sp
-
- ; now we're in a safe state for _switchin to return in the parent
- ; process.
-
- ; --------- we switch stack copies in this call -----------
- call fork_copy ; copy 0x000 to udata.u_top and the
- ; uarea and return on the childs
- ; common
- ; We are now in the kernel child context
-
- ; now the copy operation is complete we can get rid of the stuff
- ; _switchin will be expecting from our copy of the stack.
- pop bc
- pop bc
- pop bc
-
- ld hl,#_udata
- ; The child makes its own new process table entry, etc.
- ld hl, (fork_proc_ptr)
- push hl
- call _makeproc
- pop bc
- pop bc
-
- ; any calls to map process will now map the childs memory
+ .area _COMMONMEM
- ; runticks = 0;
- ld hl, #0
- ld (_runticks), hl
- ; in the child process, fork() returns zero.
- ;
- ; And we exit, with the kernel mapped, the child now being deemed
- ; to be the live uarea. The parent is frozen in time and space as
- ; if it had done a switchout().
- ret
fork_copy:
ld hl, (U_DATA__U_TOP)
public / FUZIX.git / commitdiff