Changeset 3232 in MondoRescue for branches/3.2/mindi-busybox/shell/cttyhack.c

Timestamp:

Jan 1, 2014, 12:47:38 AM (10 years ago)

Author:

Bruno Cornec

Message:

• Update mindi-busybox to 1.21.1

File:

• branches/3.2/mindi-busybox/shell/cttyhack.c (modified) (4 diffs)

branches/3.2/mindi-busybox/shell/cttyhack.c

@@ -7 +7 @@
 #include "libbb.h"
 
-//applet:IF_CTTYHACK(APPLET(cttyhack, _BB_DIR_BIN, _BB_SUID_DROP))
+//applet:IF_CTTYHACK(APPLET(cttyhack, BB_DIR_BIN, BB_SUID_DROP))
 
 //kbuild:lib-$(CONFIG_CTTYHACK) += cttyhack.o
@@ -15 +15 @@
 //config:   default y
 //config:   help
-//config:     One common problem reported on the mailing list is "can't access tty;
-//config:     job control turned off" error message which typically appears when
-//config:     one tries to use shell with stdin/stdout opened to /dev/console.
+//config:     One common problem reported on the mailing list is the "can't
+//config:     access tty; job control turned off" error message, which typically
+//config:     appears when one tries to use a shell with stdin/stdout on
+//config:     /dev/console.
 //config:     This device is special - it cannot be a controlling tty.
 //config:
-//config:     Proper solution is to use correct device instead of /dev/console.
+//config:     The proper solution is to use the correct device instead of
+//config:     /dev/console.
 //config:
-//config:     cttyhack provides "quick and dirty" solution to this problem.
+//config:     cttyhack provides a "quick and dirty" solution to this problem.
 //config:     It analyzes stdin with various ioctls, trying to determine whether
 //config:     it is a /dev/ttyN or /dev/ttySN (virtual terminal or serial line).
-//config:     If it detects one, it closes stdin/out/err and reopens that device.
-//config:     Then it executes given program. Opening the device will make
+//config:     On Linux it also checks sysfs for a pointer to the active console.
+//config:     If cttyhack is able to find the real console device, it closes
+//config:     stdin/out/err and reopens that device.
+//config:     Then it executes the given program. Opening the device will make
 //config:     that device a controlling tty. This may require cttyhack
 //config:     to be a session leader.
@@ -47 +51 @@
 //config:     # exec setsid sh -c 'exec sh </dev/tty1 >/dev/tty1 2>&1'
 //config:
+//config:     Starting getty on a controlling tty from a shell script:
+//config:
+//config:     # getty 115200 $(cttyhack)
 
 //usage:#define cttyhack_trivial_usage
-//usage:       "PROG ARGS"
+//usage:       "[PROG ARGS]"
 //usage:#define cttyhack_full_usage "\n\n"
 //usage:       "Give PROG a controlling tty if possible."
@@ -105 +112 @@
     } u;
 
-    if (!*++argv) {
-        bb_show_usage();
+    strcpy(console, "/dev/tty");
+    fd = open(console, O_RDWR);
+    if (fd < 0) {
+        /* We don't have ctty (or don't have "/dev/tty" node...) */
+        do {
+#ifdef __linux__
+            /* Note that this method does not use _stdin_.
+             * Thus, "cttyhack </dev/something" can't be used.
+             * However, this method is more reliable than
+             * TIOCGSERIAL check, which assumes that all
+             * serial lines follow /dev/ttySn convention -
+             * which is not always the case.
+             * Therefore, we use this method first:
+             */
+            int s = open_read_close("/sys/class/tty/console/active",
+                console + 5, sizeof(console) - 5);
+            if (s > 0) {
+                char *last;
+                /* Found active console via sysfs (Linux 2.6.38+).
+                 * It looks like "[tty0 ]ttyS0\n" so zap the newline:
+                 */
+                console[4 + s] = '\0';
+                /* If there are multiple consoles,
+                 * take the last one:
+                 */
+                last = strrchr(console + 5, ' ');
+                if (last)
+                    overlapping_strcpy(console + 5, last + 1);
+                break;
+            }
+
+            if (ioctl(0, VT_GETSTATE, &u.vt) == 0) {
+                /* this is linux virtual tty */
+                sprintf(console + 8, "S%u" + 1, (int)u.vt.v_active);
+                break;
+            }
+#endif
+#ifdef TIOCGSERIAL
+            if (ioctl(0, TIOCGSERIAL, &u.sr) == 0) {
+                /* this is a serial console; assuming it is named /dev/ttySn */
+                sprintf(console + 8, "S%u", (int)u.sr.line);
+                break;
+            }
+#endif
+            /* nope, could not find it */
+            console[0] = '\0';
+        } while (0);
     }
 
-    strcpy(console, "/dev/tty");
-    fd = open(console, O_RDWR);
-    if (fd >= 0) {
-        /* We already have ctty, nothing to do */
-        close(fd);
-    } else {
-        /* We don't have ctty (or don't have "/dev/tty" node...) */
-        if (0) {}
-#ifdef TIOCGSERIAL
-        else if (ioctl(0, TIOCGSERIAL, &u.sr) == 0) {
-            /* this is a serial console */
-            sprintf(console + 8, "S%d", u.sr.line);
-        }
-#endif
-#ifdef __linux__
-        else if (ioctl(0, VT_GETSTATE, &u.vt) == 0) {
-            /* this is linux virtual tty */
-            sprintf(console + 8, "S%d" + 1, u.vt.v_active);
-        }
-#endif
-        if (console[8]) {
-            fd = xopen(console, O_RDWR);
-            //bb_error_msg("switching to '%s'", console);
-            dup2(fd, 0);
-            dup2(fd, 1);
-            dup2(fd, 2);
-            while (fd > 2)
-                close(fd--);
-            /* Some other session may have it as ctty,
-             * steal it from them:
-             */
-            ioctl(0, TIOCSCTTY, 1);
-        }
+    argv++;
+    if (!argv[0]) {
+        if (!console[0])
+            return EXIT_FAILURE;
+        puts(console);
+        return EXIT_SUCCESS;
     }
 
+    if (fd < 0) {
+        fd = open_or_warn(console, O_RDWR);
+        if (fd < 0)
+            goto ret;
+    }
+    //bb_error_msg("switching to '%s'", console);
+    dup2(fd, 0);
+    dup2(fd, 1);
+    dup2(fd, 2);
+    while (fd > 2)
+        close(fd--);
+    /* Some other session may have it as ctty,
+     * try to steal it from them:
+     */
+    ioctl(0, TIOCSCTTY, 1);
+ ret:
     BB_EXECVP_or_die(argv);
 }