/* * $Id: rorw.c,v 1.1 1992/01/31 20:13:15 ejb Exp $ * $Source: /home/ejb/source/util/RCS/rorw.c,v $ * $Author: ejb $ * * This program is used to change a disk from readonly to read/write or * vice-versa by changing the flag on the vfs structure in the kernel. * It does this my going through kernel memory. * * It is very operating-system dependent as it modifies internal kernel * data structures. */ #if !defined(lint) && !defined(SABER) || defined(RCS_HDRS) static char *rcsid = "$Id: rorw.c,v 1.1 1992/01/31 20:13:15 ejb Exp $"; #endif /* !lint && !SABER || RCS_HDRS */ #include #include #include #include #include #include /* for vnode.h */ #include #include #include #include #define KERNEL "/vmunix" #define MEM "/dev/kmem" #define UNAME "_uunix" #define STAT_FLAG "-stat" #define RO_FLAG "-ro" #define RW_FLAG "-rw" #ifndef __STDC__ #define const #else #define const #endif /* __STDC__ */ typedef enum {a_stat, a_ro, a_rw} action_t; extern int errno; extern char *sys_errlist[]; static char *whoami; #ifdef __STDC__ void usage(void) #else void usage() #endif /* __STDC__ */ { fprintf(stderr, "usage: %s pathname [%s | %s | %s]\n", whoami, STAT_FLAG, RO_FLAG, RW_FLAG); fprintf(stderr, " pathname is the name of any directory on the "); fprintf(stderr, "filesystem you wish to change.\n"); fprintf(stderr, " %s causes the currente state to be printer.\n", STAT_FLAG); fprintf(stderr, " %s means to make the filesystem readonly.\n", RO_FLAG); fprintf(stderr, " %s means to make the filesystem read/write.\n", RW_FLAG); exit(1); } #ifdef __STDC__ int open_kernel(void) #else int open_kernel() #endif /* __STDC__ */ { int k; if ((k = open(MEM, O_RDWR, 0)) == -1) { fprintf(stderr, "%s: failure opening %s read/write: %s\n", whoami, MEM, sys_errlist[errno]); exit(1); } return (k); } #ifdef __STDC__ void safe_lseek(int fd, int offset) #else void safe_lseek(fd, offset) int fd; int offset; #endif /* __STDC__ */ { if (lseek(fd, offset, L_SET) == -1) { fprintf(stderr, "%s: lseek failed: %s\n", whoami, sys_errlist[errno]); exit(1); } } #ifdef __STDC__ void safe_read(int fd, char *buf, int len) #else void safe_read(fd, buf, len) int fd; char *buf; int len; #endif /* __STDC__ */ { if (read(fd, buf, len) != len) { fprintf(stderr, "%s: read failed: %s\n", whoami, sys_errlist[errno]); exit(1); } } #ifdef __STDC__ void safe_write(int fd, char *buf, int len) #else void safe_write(fd, buf, len) int fd; char *buf; int len; #endif /* __STDC__ */ { if (write(fd, buf, len) != len) { fprintf(stderr, "%s: write failed: %s\n", whoami, sys_errlist[errno]); exit(1); } } #ifdef __STDC__ void rorw(int k, action_t action) #else void rorw(k, action) int k; action_t action; #endif /* __STDC__ */ { struct nlist n[2]; short short_value; short u_cmask; int value; short pid; int vfs_flag; /* calculate offsets */ const int u_cmask_offset = (int)&(((struct user *)0)->u_cmask); const int u_cdir_offset = (int)&(((struct user *)0)->u_cdir); const int v_vfsp_offset = (int)&(((struct vnode *)0)->v_vfsp); const int vfs_flag_offset = (int)&(((struct vfs *)0)->vfs_flag); /* Get umask for sanity checking purposes */ u_cmask = umask(0); (void) umask(u_cmask); /* Look up the symbol as defined in UNAME in the kernel */ n[0].n_name = UNAME; n[1].n_name = NULL; switch (nlist(KERNEL, n)) { case -1: fprintf(stderr, "%s: failure opening kernel symbol table: %s\n", whoami, sys_errlist[errno]); exit(1); break; case 0: value = n[0].n_value; break; default: fprintf(stderr, "%s: unable to find %s in %s.\n", whoami, n[0].n_name, KERNEL); exit(1); break; } /* value == offset of uunix */ /* seek to uunix and read value */ safe_lseek(k, value); safe_read(k, &value, sizeof(value)); /* value == offset of *uunix */ /* seek to uunix->u_cmask and read value */ safe_lseek(k, value + u_cmask_offset); safe_read(k, &short_value, sizeof(short_value)); /* SANITY CHECK: make sure this is the actual umask */ if (u_cmask != short_value) { fprintf(stderr, "%s: umask from kernel (%o) does not match umask (%o)!\n", whoami, short_value, u_cmask); exit(2); } /* value == offset of *uunix */ /* seek to u.u_cdir and read value */ safe_lseek(k, value + u_cdir_offset); safe_read(k, &value, sizeof(value)); /* value == offset of u.u_cdir */ /* seek to u.u_cdir->v_vfsp and read value */ safe_lseek(k, value + v_vfsp_offset); safe_read(k, &value, sizeof(value)); /* Set value to offset to u.u_cdir->v_vfsp->vfs_flag */ value += vfs_flag_offset; /* value == offset to u.u_cdir->v_vfsp */ /* seek to u.u_cdir->v_vfsp->vfs_flag and read vfs_flag */ safe_lseek(k, value); safe_read(k, &vfs_flag, sizeof(vfs_flag)); printf("The value of vfs_flag is 0x%08x\n", vfs_flag); switch (action) { case a_stat: break; case a_ro: vfs_flag |= VFS_RDONLY; break; case a_rw: vfs_flag &= ~VFS_RDONLY; break; default: fprintf(stderr, "%s: internal error: default reached in rorw!\n", whoami); exit(3); } if (action != a_stat) { /* seek to vfs_flag */ safe_lseek(k, value); /* write new value */ safe_write(k, &vfs_flag, sizeof(vfs_flag)); printf("The value vfs_flag has been changed to 0x%08x.\n", vfs_flag); } } #ifdef __STDC__ main(int argc, char *argv[]) #else main(argc, argv) int argc; char *argv[]; #endif /* __STDC__ */ { char *pathname; char *flag; action_t action; int k; if ((whoami = strrchr(argv[0], '/')) == NULL) whoami = argv[0]; else whoami++; if (argc != 3) usage(); pathname = argv[1]; flag = argv[2]; if (strcmp(flag, STAT_FLAG) == 0) action = a_stat; else if (strcmp(flag, RO_FLAG) == 0) action = a_ro; else if (strcmp(flag, RW_FLAG) == 0) action = a_rw; else usage(); /* First, attempt to cd to the given directory. */ if (chdir(pathname) == -1) { fprintf(stderr, "%s: cd %s failed: ", whoami, pathname); perror(NULL); exit(1); } k = open_kernel(); rorw(k, action); (void) close(k); return(0); }