PSIONICS FILE - PROCESS ======================= Processes and their properties Last modified 1997-09-11 ============================== The Series 3 operating system is a fully multitasking one; at any time it can be running any number of processes (up to some limit). Much useful information about processes can be displayed with the SPY program. Each process has a name, a task number, and a process ID. The task number runs from 1 upwards (the Series 3 is limited to 24), and a task number can be reused whenever a process terminates. The process ID consists of the address of the control block for the process in kernel memory in the bottom 12 bits, and a simple counter in the top 4 bits; this starts at 0 for the first process to use this control block, and is incremented whenever the block is reused. The name of a process is normally the name of the program (1 to 8 characters), followed by ".$" (or ".@" for subtasks), and the task number as 2 decimal digits. The code for a process is placed in a segment called by the name of the program followed by ".SC". Thus it is not possible to run two programs with the same name at the same time. Each process has a priority. Non-operating system processes are limited to priority 192; the normal priorities are 128 for foreground and 112 for background. Only the highest priority process(es) able to run will do so; all lower priority ones will wait. System processes ---------------- There are two kinds of system processes: fixed ones and optional ones. The fixed processes are: SYS$NULL.$01 handles power off SYS$MANG.$02 the process and resource manager SYS$FSRV.$03 the file server SYS$WSRC.$04 the window server SYS$SHLL.$05 the process launcher and system screen TIME.$06 the time and alarm server The optional processes are: SYS$NCP.$?? the remote link manager Registers --------- Processes may use the data registers (AX, BX, CX, DX, SI, and DI) without restriction. The kernel may move memory segments about in memory at any time without warning; when it does so, those of the segment registers (CS, DS, ES, and SS) that appear to the kernel to be valid will be adjusted automatically. If it is desired to change these registers at any other time, it should therefore be done with interrupts disabled. OPL uses CS, DS, and SS, and these should not be altered by assembler code invoked from with OPL. ES is not used by the OPL interpreter, and is normally left the same as DS and SS (which are always the same). Many system calls use data registers to hold pointers; a segment register is also used with each such pointer. The Psionics files SYSCALLS.n indicate when an address is using ES; they do not distinguish DS and SS. Any assembler code called from OPL should exit with ES equal to DS. The only other values that can usefully be placed in ES are the kernel data segment (using system call GenDataSegment), and segments created with the system call SegCreate. To do the former, just invoke INT $8F; ES will then point to the kernel data segment, and accesses via ES will behave just as if done with the system call GenGetOsData (it is not possible to write in this way). The latter is done as follows: ; Assume the segment handle is in BX. INT $8F MOV ES,ES:[BX] ; ES now points to the start of the segment. ; If the segment moves, ES will change automatically. ; Before returning to OPL: CLI ; with interrupts disabled PUSH DS ; copy DS to ES POP ES STI ; and allow interrupts again Memory ------ Each process has a single segment of memory. From zero upwards, this contains: reserved statics stack (grows downwards) normal statics heap (grows upwards) The heap is divided into allocated and free cells. The SPY program shows the number and total byte count of each kind of cell. The kernel will remove free cells from the end of the heap when it needs space. The stack is initialized to all $FF; it must always hold at least 256 bytes to allow interrupts to be processed (otherwise panic 69 will occur). A typical stack size is $A00. The SPY program allows the unused portion of the stack to be refilled with $FF (to allow the high water mark to be reset). The heap consists of consecutive cells: Offset 0 (word): length of data portion (L) Offset 2 to L+1: data portion (whose address is returned by allocators) @Is that right, or is it 2 to L-1 ?@ Cells are always aligned to even addresses, and for this and other reasons may be larger than requested. Specific memory locations ------------------------- The following table lists some specific use of memory locations. Offset 0 (word): initialized to $DEAD; should never change Offset 2 to 5: used by the kernel Offset 6 (word): handle of the segment holding the fold tables @@ Offset 8 to 15: used by the object oriented programming system Offset 16 (word): used by the kernel Offset 18 (word): address of block Offset 20 (word): handle of the application manager object Offset 22 to 25: used by the window server Offset 26 to 29: used by the OPL runtime system Offset 30 (word): used by the debugger Offset 32 (byte): zero when address trapping is turned off (do not alter) Offset 33 (byte): non-zero when the kernel is modifying the heap Offset 34 (word): address of cstr holding the program name; used to determine which list on the system screen a process appears in (@if this word is zero, the process will not be sent X messages) Offset 36 (word): address of a heap cell containing a cstr holding the full path name of the program being executed, followed by a qstr holding the program information (see system call FilExecute). Offset 38 (word): not used by the kernel or OPL; used by the debugger Offset 40 to 53: not used by the kernel or OPL Offset 54 (word): address of current dialog structure Offset 56 (word): @@ DatGate object handle Offset 58 (word): non-zero if locked (by OPL "LOCK ON" or equivalent) Offset 60 (word): address of cstr to appear in the status window Offset 62 (word): address of cstr holding current file being processed Offset 64 : maximum limit of stack (if floating point emulation is in use, the emulator uses offsets 64 to 767). Certain of these memory locations have names in the system documentation: 34 DatProcessNamePtr 36 DatCommandPtr 40 DatApp1 42 DatApp2 44 DatApp3 46 DatApp4 48 DatApp5 50 DatApp6 52 DatApp7 58 DatLocked 60 DatStatusNamePtr 62 DatUsedPathNamePtr @Location "winHandle" is the channel number of the console device. Block has the following contents: @this is a "wserv" object@ Offset 32 (word): address of block Block has the following contents: Offset 12 (word): address of block Block is created by the MINIT keyword and destroyed by the MENU keyword. Outside this range, the block is invalid, and the pointer in the block is invalid. Each MCARD keyword can move this block, thus altering that pointer. The block has the following contents: Offset 0 (byte): number of MCARD calls so far Offset 1 onward: menu information blocks, in order of menu creation Each menu information block has the following contents: Offset 0 (word): address of secondary menu information block Offset 2 (cstr): menu title Each secondary menu information block has the following contents: Offset 0 (long): [Only ever seen $7392A1DF] Offset 4 (word): number of items in the menu Offset 6 (long): [Only ever seen 1 so far] Offset 10 (word): address of item table Each item table has the following contents: Offset 0 (byte): number of items in the menu Offset 1 onward: item information blocks, in order of item Each item information block has the following contents: Offset 0 (byte): number of bytes in the block, excluding this one Offset 1 (byte): Psion+ accelerator code (lowercased) Offset 2 (cstr): item text Time process ------------ The pending alarms can be located in the memory of the Time process. At some location between offset $0A00 and $0AFF is a block with the form: Offset 0 (long): $08040201 Offset 4 (long): $00402010 Offset 12 (word): first alarm control block It is reported that on the Series 3c this has moved to somewhere between $0C00 and $0CFF. It is also reported that on some versions the control block is at offset 10 or 15. The alarm control blocks are in a circular list, with the last pointing to offset 12 (or 10 or 15) of the above block (which is not an alarm control block); if that location points to itself, there are no alarms. Each block has the form: Offset 0 (word): next alarm control block Offset 2 (word): reported that this is the second next alarm control block Offset 6 (word): process ID of process owning alarm Offset 8 (byte): 0 = clock alarm, 1 = has time and date, 2 = has date Offset 10 (long): abstime alarm expires Offset 14 (long): abstime displayed in alarm message Offset 18 (qstr): name of alarm sound Offset 28 (cstr): text displayed in alarm message Offset 93 to 255: [unknown; alleged to be part of the block] The built-in alarm sounds have names consisting of a single byte (thus offset 18 is 1 and offset 19 holds the name): 1=rings, 2=chimes, and 16=silence. @System screen or Window Server (which?) places info about 14 application buttons at DatApp1.@