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prog - running programs


bind #p /prog















The prog device serves a two-level directory structure. The first level contains numbered directories corresponding to pids of live Limbo processes; each such directory contains a set of files representing the corresponding process. All files operate on UTF (see utf(6)) strings.

The read-only status file contains seven space-separated fields. The fields are: the process and process group identifiers, each 8 characters right justified; the user name, at least 10 characters left justified; cpu time in minutes, seconds and tenths of seconds; the process state, 10 characters left justified; the amount of memory used by the process in units of 1024 bytes, at least 5 characters, right justified, followed by a K; and the name of the current program module, up to 28 characters, left justified.

The read-only pgrp file contains the process group identifier, in decimal.

The read-only nsgrp file contains the namespace group identifier, in decimal.

The read-only ns file contains a set of mount and bind commands which describe the sys-bind(2) and mount operations used to construct the name space, in the format of namespace(6). The last line of the file is a cd command indicating the working directory.

The read-only wait file may be read to recover information about the exiting children of the process. A read of wait will block until a child of the process, created after wait was opened, exits. When such a child exits, it produces a string with three fields: the pid of the exiting process, a space, module name enclosed in  "'s, a colon, and a possibly empty error message. The error message will contain at most 64 characters.

The read-only fd file describes the open file descriptors in the file descriptor group of the process. Each line describes an open file. The fields are: the file descriptor index, the open mode (r, w, rw); the type and number of the device; the path, version and type of the file's qid (see intro(5)); the file's atomic I/O unit, as defined in sys-iounit(2)); the file I/O offset in bytes; and the name with which it was opened.

The read-only exception file gives details of the last exception to occur in the process, if any. The fields are the program counter value when the exception occurred, the module it occurred in and the exception itself, each separated by a space. If none, the result is the empty string.

Messages written to the ctl file control the execution of the process.

Kill the process.
Kill all processes in the same group as the process. A process writing to its own ctl file does not kill itself.
exceptions propagate
Applies to process group leaders only (ie any process that executes a system call sys->pctl(Sys->NEWPGRP, ... ). If any process in the same group as the leader incurs an exception which it does not handle, atomically raise the exception in all processes in the group. In this case exceptions are generated for killed processes as well. This mechanism allows all processes in a process group to perfom error recovery when one of them faults.
exceptions notifyleader
Applies to process group leaders only. If any process in the same group as the leader incurs an exception which it does not handle, atomically destroy all processes in the group except for the leader and raise the exception in the leader. This error recovery mechanism might be appropriate when a fault occurs amongst a group of processes and the group leader takes sole responsibilty for recovery.
Mark all processes that the process spawns in future as restricted. A restricted process is one which can run out of memory when a configured limit has been reached and before total memory is exhausted. An unrestricted process can allocate memory until memory is truly exhausted. Typically a window manager or server might be unrestricted as they are processes fundamental to the running of a system.

The dbgctl file provides facilities for debugging a process. Messages written to the file control the execution of the process.

step n
Step the interpreter for at most n instructions, or until a breakpoint is reached.
Step the interpreter until a return from the current activation frame or a breakpoint is reached.
Step the interpreter until a breakpoint is reached.
Stop the process as soon as possible. Do not allow the process to execute again until an unstop message is received.
Cancel the effect of any previous stop.
bpt set path pc
Set a breakpoint at pc for the module given by path.
bpt del path pc
Clear a breakpoint if one exists.

Reading dbgctl gives updates for some state transitions while the process is being debugged. Each update is terminated by a newline.

The process exited without error.
broken: error
The process died due to error, a string with up to 64 characters.
The process is blocked sending on a channel.
The process is blocked receiving on a channel.
The process is blocked in an alt statement.
The process is unblocked and now ready to run.
new pid
The process has spawned a new process identified by pid.

The read-only stack file contains the dynamic call stack trace. Each activation frame is described by one line with six fields, separated by a space: the frame pointer, program counter, module data pointer, and module code pointer, each 8 hexadecimal digits; the execution method for the module (0 means interpreted, 1 compiled); and the path name of the module. The top activation frame starts at offset 0.

The heap file may be queried to examine the state of the process. A data query contains an address, a period, a format character, and a count. An instruction query contains a pc, a plus, a mode address, a period, the format I, and a count. The addresses in the query may be decimal, hexadecimal preceded by 0x or 0X, or octal preceded by 0. Count gives the number of consecutive data items retrieved by reading heap starting at offset 0; the format varies according to the format character. All data items other than strings are terminated by a newline.

32-bit decimal ints.
8-bit unsigned decimal bytes.
64-bit decimal bytes.
64-bit reals.
Disassembled Dis instructions.
32-bit hexadecimal address, or nil.

The following formats examine properties of specific 32-bit pointers.

Examine a list, yielding a pair of hexadecimal addresses separated by a period, giving the address of the head and tail of a list. It is an error to use L on nil.
Examine an array, yielding a decimal length, a period, and the address of the 0th element of an array, or nil.
Examine a string, yielding the decimal length in characters, a period, and the utf(6) representation of the string.
Examine a module reference, yielding the address of its global data or nil.

The text file is currently unimplemented.



PROG(3) Rev:  Tue Oct 21 21:57:17 GMT 2008