getset.c

一个简单的操作系统minix的核心代码

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				src/mm/getset.c	 	 
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18500	/* This file handles the 4 system calls that get and set uids and gids.
18501	 * It also handles getpid(), setsid(), and getpgrp().  The code for each
18502	 * one is so tiny that it hardly seemed worthwhile to make each a separate
18503	 * function.
18504	 */
18505	
18506	#include "mm.h"
18507	#include <minix/callnr.h>
18508	#include <signal.h>
18509	#include "mproc.h"
18510	#include "param.h"
18511	
18512	/*===========================================================================*
18513	 *                              do_getset                                    *
18514	 *===========================================================================*/
18515	PUBLIC int do_getset()
18516	{
18517	/* Handle GETUID, GETGID, GETPID, GETPGRP, SETUID, SETGID, SETSID.  The four
18518	 * GETs and SETSID return their primary results in 'r'.  GETUID, GETGID, and
18519	 * GETPID also return secondary results (the effective IDs, or the parent
18520	 * process ID) in 'result2', which is returned to the user.
18521	 */
18522	
18523	  register struct mproc *rmp = mp;
18524	  register int r;
18525	
18526	  switch(mm_call) {
18527	        case GETUID:
18528	                r = rmp->mp_realuid;
18529	                result2 = rmp->mp_effuid;
18530	                break;
18531	
18532	        case GETGID:
18533	                r = rmp->mp_realgid;
18534	                result2 = rmp->mp_effgid;
18535	                break;
18536	
18537	        case GETPID:
18538	                r = mproc[who].mp_pid;
18539	                result2 = mproc[rmp->mp_parent].mp_pid;
18540	                break;
18541	
18542	        case SETUID:
18543	                if (rmp->mp_realuid != usr_id && rmp->mp_effuid != SUPER_USER)
18544	                        return(EPERM);
18545	                rmp->mp_realuid = usr_id;
18546	                rmp->mp_effuid = usr_id;
18547	                tell_fs(SETUID, who, usr_id, usr_id);
18548	                r = OK;
18549	                break;
18550	
18551	        case SETGID:
18552	                if (rmp->mp_realgid != grpid && rmp->mp_effuid != SUPER_USER)
18553	                        return(EPERM);
18554	                rmp->mp_realgid = grpid;
18555	                rmp->mp_effgid = grpid;
18556	                tell_fs(SETGID, who, grpid, grpid);
18557	                r = OK;
18558	                break;
18559	
18560	        case SETSID:
18561	                if (rmp->mp_procgrp == rmp->mp_pid) return(EPERM);
18562	                rmp->mp_procgrp = rmp->mp_pid;
18563	                tell_fs(SETSID, who, 0, 0);
18564	                /*FALL THROUGH*/
18565	
18566	        case GETPGRP:
18567	                r = rmp->mp_procgrp;
18568	                break;
18569	
18570	        default:
18571	                r = EINVAL;
18572	                break;  
18573	  }
18574	  return(r);
18575	}