stadir.c

一个简单的操作系统minix的核心代码

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				src/fs/stadir.c	 	 
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25900	/* This file contains the code for performing four system calls relating to
25901	 * status and directories.
25902	 *
25903	 * The entry points into this file are
25904	 *   do_chdir:  perform the CHDIR system call
25905	 *   do_chroot: perform the CHROOT system call
25906	 *   do_stat:   perform the STAT system call
25907	 *   do_fstat:  perform the FSTAT system call
25908	 */
25909	
25910	#include "fs.h"
25911	#include <sys/stat.h>
25912	#include "file.h"
25913	#include "fproc.h"
25914	#include "inode.h"
25915	#include "param.h"
25916	
25917	FORWARD _PROTOTYPE( int change, (struct inode **iip, char *name_ptr, int len));
25918	FORWARD _PROTOTYPE( int stat_inode, (struct inode *rip, struct filp *fil_ptr,
25919	                        char *user_addr)                                );
25920	
25921	/*===========================================================================*
25922	 *                              do_chdir                                     *
25923	 *===========================================================================*/
25924	PUBLIC int do_chdir()
25925	{
25926	/* Change directory.  This function is  also called by MM to simulate a chdir
25927	 * in order to do EXEC, etc.  It also changes the root directory, the uids and
25928	 * gids, and the umask. 
25929	 */
25930	
25931	  int r;
25932	  register struct fproc *rfp;
25933	
25934	  if (who == MM_PROC_NR) {
25935	        rfp = &fproc[slot1];
25936	        put_inode(fp->fp_rootdir);
25937	        dup_inode(fp->fp_rootdir = rfp->fp_rootdir);
25938	        put_inode(fp->fp_workdir);
25939	        dup_inode(fp->fp_workdir = rfp->fp_workdir);
25940	
25941	        /* MM uses access() to check permissions.  To make this work, pretend
25942	         * that the user's real ids are the same as the user's effective ids.
25943	         * FS calls other than access() do not use the real ids, so are not
25944	         * affected.
25945	         */
25946	        fp->fp_realuid =
25947	        fp->fp_effuid = rfp->fp_effuid;
25948	        fp->fp_realgid =
25949	        fp->fp_effgid = rfp->fp_effgid;
25950	        fp->fp_umask = rfp->fp_umask;
25951	        return(OK);
25952	  }
25953	
25954	  /* Perform the chdir(name) system call. */
25955	  r = change(&fp->fp_workdir, name, name_length);
25956	  return(r);
25957	}
	
	
25960	/*===========================================================================*
25961	 *                              do_chroot                                    *
25962	 *===========================================================================*/
25963	PUBLIC int do_chroot()
25964	{
25965	/* Perform the chroot(name) system call. */
25966	
25967	  register int r;
25968	
25969	  if (!super_user) return(EPERM);       /* only su may chroot() */
25970	  r = change(&fp->fp_rootdir, name, name_length);
25971	  return(r);
25972	}
	
	
25975	/*===========================================================================*
25976	 *                              change                                       *
25977	 *===========================================================================*/
25978	PRIVATE int change(iip, name_ptr, len)
25979	struct inode **iip;             /* pointer to the inode pointer for the dir */
25980	char *name_ptr;                 /* pointer to the directory name to change to */
25981	int len;                        /* length of the directory name string */
25982	{
25983	/* Do the actual work for chdir() and chroot(). */
25984	
25985	  struct inode *rip;
25986	  register int r;
25987	
25988	  /* Try to open the new directory. */
25989	  if (fetch_name(name_ptr, len, M3) != OK) return(err_code);
25990	  if ( (rip = eat_path(user_path)) == NIL_INODE) return(err_code);
25991	
25992	  /* It must be a directory and also be searchable. */
25993	  if ( (rip->i_mode & I_TYPE) != I_DIRECTORY)
25994	        r = ENOTDIR;
25995	  else
25996	        r = forbidden(rip, X_BIT);      /* check if dir is searchable */
25997	
25998	  /* If error, return inode. */
25999	  if (r != OK) {
26000	        put_inode(rip);
26001	        return(r);
26002	  }
26003	
26004	  /* Everything is OK.  Make the change. */
26005	  put_inode(*iip);              /* release the old directory */
26006	  *iip = rip;                   /* acquire the new one */
26007	  return(OK);
26008	}
	
	
26011	/*===========================================================================*
26012	 *                              do_stat                                      *
26013	 *===========================================================================*/
26014	PUBLIC int do_stat()
26015	{
26016	/* Perform the stat(name, buf) system call. */
26017	
26018	  register struct inode *rip;
26019	  register int r;
26020	
26021	  /* Both stat() and fstat() use the same routine to do the real work.  That
26022	   * routine expects an inode, so acquire it temporarily.
26023	   */
26024	  if (fetch_name(name1, name1_length, M1) != OK) return(err_code);
26025	  if ( (rip = eat_path(user_path)) == NIL_INODE) return(err_code);
26026	  r = stat_inode(rip, NIL_FILP, name2); /* actually do the work.*/
26027	  put_inode(rip);               /* release the inode */
26028	  return(r);
26029	}
	
	
26032	/*===========================================================================*
26033	 *                              do_fstat                                     *
26034	 *===========================================================================*/
26035	PUBLIC int do_fstat()
26036	{
26037	/* Perform the fstat(fd, buf) system call. */
26038	
26039	  register struct filp *rfilp;
26040	
26041	  /* Is the file descriptor valid? */
26042	  if ( (rfilp = get_filp(fd)) == NIL_FILP) return(err_code);
26043	
26044	  return(stat_inode(rfilp->filp_ino, rfilp, buffer));
26045	}
	
	
26048	/*===========================================================================*
26049	 *                              stat_inode                                   *
26050	 *===========================================================================*/
26051	PRIVATE int stat_inode(rip, fil_ptr, user_addr)
26052	register struct inode *rip;     /* pointer to inode to stat */
26053	struct filp *fil_ptr;           /* filp pointer, supplied by 'fstat' */
26054	char *user_addr;                /* user space address where stat buf goes */
26055	{
26056	/* Common code for stat and fstat system calls. */
26057	
26058	  struct stat statbuf;
26059	  mode_t mo;
26060	  int r, s;
26061	
26062	  /* Update the atime, ctime, and mtime fields in the inode, if need be. */
26063	  if (rip->i_update) update_times(rip);
26064	
26065	  /* Fill in the statbuf struct. */
26066	  mo = rip->i_mode & I_TYPE;
26067	  s = (mo == I_CHAR_SPECIAL || mo == I_BLOCK_SPECIAL);  /* true iff special */
26068	  statbuf.st_dev = rip->i_dev;
26069	  statbuf.st_ino = rip->i_num;
26070	  statbuf.st_mode = rip->i_mode;
26071	  statbuf.st_nlink = rip->i_nlinks & BYTE;
26072	  statbuf.st_uid = rip->i_uid;
26073	  statbuf.st_gid = rip->i_gid & BYTE;
26074	  statbuf.st_rdev = (dev_t) (s ? rip->i_zone[0] : NO_DEV);
26075	  statbuf.st_size = rip->i_size;
26076	
26077	  if (rip->i_pipe == I_PIPE) {
26078	        statbuf.st_mode &= ~I_REGULAR;  /* wipe out I_REGULAR bit for pipes */
26079	        if (fil_ptr != NIL_FILP && fil_ptr->filp_mode & R_BIT) 
26080	                statbuf.st_size -= fil_ptr->filp_pos;
26081	  }
26082	
26083	  statbuf.st_atime = rip->i_atime;
26084	  statbuf.st_mtime = rip->i_mtime;
26085	  statbuf.st_ctime = rip->i_ctime;
26086	
26087	  /* Copy the struct to user space. */
26088	  r = sys_copy(FS_PROC_NR, D, (phys_bytes) &statbuf,
26089	                who, D, (phys_bytes) user_addr, (phys_bytes) sizeof(statbuf));
26090	  return(r);
26091	}