syscall.h Source File

00001 /* syscalls.h 
00002  *      Nachos system call interface.  These are Nachos kernel operations
00003  *      that can be invoked from user programs, by trapping to the kernel
00004  *      via the "syscall" instruction.
00005  *
00006  *      This file is included by user programs and by the Nachos kernel. 
00007  *
00008  * Copyright (c) 1992-1993 The Regents of the University of California.
00009  * All rights reserved.  See copyright.h for copyright notice and limitation 
00010  * of liability and disclaimer of warranty provisions.
00011  */
00012 
00013 #ifndef SYSCALLS_H
00014 #define SYSCALLS_H
00015 
00016 #include "copyright.h"
00017 
00018 /* system call codes -- used by the stubs to tell the kernel which system call
00019  * is being asked for
00020  */
00021 #define SC_Halt         0
00022 #define SC_Exit         1
00023 #define SC_Exec         2
00024 #define SC_Join         3
00025 #define SC_Create       4
00026 #define SC_Open         5
00027 #define SC_Read         6
00028 #define SC_Write        7
00029 #define SC_Close        8
00030 #define SC_Fork         9
00031 #define SC_Yield        10
00032 
00033 #ifndef IN_ASM
00034 
00035 /* The system call interface.  These are the operations the Nachos
00036  * kernel needs to support, to be able to run user programs.
00037  *
00038  * Each of these is invoked by a user program by simply calling the 
00039  * procedure; an assembly language stub stuffs the system call code
00040  * into a register, and traps to the kernel.  The kernel procedures
00041  * are then invoked in the Nachos kernel, after appropriate error checking, 
00042  * from the system call entry point in exception.cc.
00043  */
00044 
00045 /* Stop Nachos, and print out performance stats */
00046 void Halt();            
00047  
00048 
00049 /* Address space control operations: Exit, Exec, and Join */
00050 
00051 /* This user program is done (status = 0 means exited normally). */
00052 void Exit(int status);  
00053 
00054 /* A unique identifier for an executing user program (address space) */
00055 typedef int SpaceId;    
00056  
00057 /* Run the executable, stored in the Nachos file "name", and return the 
00058  * address space identifier
00059  */
00060 SpaceId Exec(char *name);
00061  
00062 /* Only return once the the user program "id" has finished.  
00063  * Return the exit status.
00064  */
00065 int Join(SpaceId id);   
00066  
00067 
00068 /* File system operations: Create, Open, Read, Write, Close
00069  * These functions are patterned after UNIX -- files represent
00070  * both files *and* hardware I/O devices.
00071  *
00072  * If this assignment is done before doing the file system assignment,
00073  * note that the Nachos file system has a stub implementation, which
00074  * will work for the purposes of testing out these routines.
00075  */
00076  
00077 /* A unique identifier for an open Nachos file. */
00078 typedef int OpenFileId; 
00079 
00080 /* when an address space starts up, it has two open files, representing 
00081  * keyboard input and display output (in UNIX terms, stdin and stdout).
00082  * Read and Write can be used directly on these, without first opening
00083  * the console device.
00084  */
00085 
00086 #define ConsoleInput    0  
00087 #define ConsoleOutput   1  
00088  
00089 /* Create a Nachos file, with "name" */
00090 void Create(char *name);
00091 
00092 /* Open the Nachos file "name", and return an "OpenFileId" that can 
00093  * be used to read and write to the file.
00094  */
00095 OpenFileId Open(char *name);
00096 
00097 /* Write "size" bytes from "buffer" to the open file. */
00098 void Write(char *buffer, int size, OpenFileId id);
00099 
00100 /* Read "size" bytes from the open file into "buffer".  
00101  * Return the number of bytes actually read -- if the open file isn't
00102  * long enough, or if it is an I/O device, and there aren't enough 
00103  * characters to read, return whatever is available (for I/O devices, 
00104  * you should always wait until you can return at least one character).
00105  */
00106 int Read(char *buffer, int size, OpenFileId id);
00107 
00108 /* Close the file, we're done reading and writing to it. */
00109 void Close(OpenFileId id);
00110 
00111 
00112 
00113 /* User-level thread operations: Fork and Yield.  To allow multiple
00114  * threads to run within a user program. 
00115  */
00116 
00117 /* Fork a thread to run a procedure ("func") in the *same* address space 
00118  * as the current thread.
00119  */
00120 void Fork(void (*func)());
00121 
00122 /* Yield the CPU to another runnable thread, whether in this address space 
00123  * or not. 
00124  */
00125 void Yield();           
00126 
00127 #endif /* IN_ASM */
00128 
00129 #endif /* SYSCALL_H */