115 lines
3.8 KiB
C
115 lines
3.8 KiB
C
/* This file contains some utility routines for MM.
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*
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* The entry points are:
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* allowed: see if an access is permitted
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* no_sys: this routine is called for invalid system call numbers
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* panic: MM has run aground of a fatal error and cannot continue
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* tell_fs: interface to FS
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*/
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#include "mm.h"
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#include <sys/stat.h>
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#include <minix/callnr.h>
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#include <minix/com.h>
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#include <fcntl.h>
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#include <signal.h> /* needed only because mproc.h needs it */
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#include "mproc.h"
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#include "param.h"
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/*===========================================================================*
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* allowed *
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*===========================================================================*/
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PUBLIC int allowed(name_buf, s_buf, mask)
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char *name_buf; /* pointer to file name to be EXECed */
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struct stat *s_buf; /* buffer for doing and returning stat struct*/
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int mask; /* R_BIT, W_BIT, or X_BIT */
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{
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/* Check to see if file can be accessed. Return EACCES or ENOENT if the access
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* is prohibited. If it is legal open the file and return a file descriptor.
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*/
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int fd;
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int save_errno;
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/* Use the fact that mask for access() is the same as the permissions mask.
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* E.g., X_BIT in <minix/const.h> is the same as X_OK in <unistd.h> and
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* S_IXOTH in <sys/stat.h>. tell_fs(DO_CHDIR, ...) has set MM's real ids
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* to the user's effective ids, so access() works right for setuid programs.
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*/
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if (access(name_buf, mask) < 0) return(-errno);
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/* The file is accessible but might not be readable. Make it readable. */
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tell_fs(SETUID, PM_PROC_NR, (int) SUPER_USER, (int) SUPER_USER);
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/* Open the file and fstat it. Restore the ids early to handle errors. */
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fd = open(name_buf, O_RDONLY | O_NONBLOCK);
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save_errno = errno; /* open might fail, e.g. from ENFILE */
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tell_fs(SETUID, PM_PROC_NR, (int) mp->mp_effuid, (int) mp->mp_effuid);
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if (fd < 0) return(-save_errno);
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if (fstat(fd, s_buf) < 0) panic("allowed: fstat failed", NO_NUM);
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/* Only regular files can be executed. */
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if (mask == X_BIT && (s_buf->st_mode & I_TYPE) != I_REGULAR) {
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close(fd);
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return(EACCES);
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}
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return(fd);
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}
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/*===========================================================================*
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* no_sys *
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*===========================================================================*/
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PUBLIC int no_sys()
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{
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/* A system call number not implemented by MM has been requested. */
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return(EINVAL);
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}
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/*===========================================================================*
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* panic *
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*===========================================================================*/
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PUBLIC void panic(format, num)
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char *format; /* format string */
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int num; /* number to go with format string */
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{
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/* Something awful has happened. Panics are caused when an internal
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* inconsistency is detected, e.g., a programming error or illegal value of a
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* defined constant.
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*/
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printf("Memory manager panic: %s ", format);
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if (num != NO_NUM) printf("%d",num);
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printf("\n");
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tell_fs(SYNC, 0, 0, 0); /* flush the cache to the disk */
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sys_abort(RBT_PANIC);
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}
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/*===========================================================================*
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* tell_fs *
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*===========================================================================*/
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PUBLIC void tell_fs(what, p1, p2, p3)
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int what, p1, p2, p3;
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{
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/* This routine is only used by MM to inform FS of certain events:
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* tell_fs(CHDIR, slot, dir, 0)
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* tell_fs(EXEC, proc, 0, 0)
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* tell_fs(EXIT, proc, 0, 0)
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* tell_fs(FORK, parent, child, pid)
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* tell_fs(SETGID, proc, realgid, effgid)
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* tell_fs(SETSID, proc, 0, 0)
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* tell_fs(SETUID, proc, realuid, effuid)
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* tell_fs(SYNC, 0, 0, 0)
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* tell_fs(UNPAUSE, proc, signr, 0)
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*/
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message m;
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m.tell_fs_arg1 = p1;
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m.tell_fs_arg2 = p2;
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m.tell_fs_arg3 = p3;
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_taskcall(FS_PROC_NR, what, &m);
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}
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