diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index a6aca87408830b12aa0302dad05da5fa79244617..98223a67694026a97d2ccfceb89850250f9f7afe 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1075,6 +1075,7 @@ Table 1-11: Files in /proc/tty
drivers list of drivers and their usage
ldiscs registered line disciplines
driver/serial usage statistic and status of single tty lines
+ consoles registered system console lines
..............................................................................
To see which tty's are currently in use, you can simply look into the file
@@ -1093,6 +1094,37 @@ To see which tty's are currently in use, you can simply look into the file
/dev/tty /dev/tty 5 0 system:/dev/tty
unknown /dev/tty 4 1-63 console
+To see which character device lines are currently used for the system console
+/dev/console, you may simply look into the file /proc/tty/consoles:
+
+ > cat /proc/tty/consoles
+ tty0 -WU (ECp) 4:7
+ ttyS0 -W- (Ep) 4:64
+
+The columns are:
+
+ device name of the device
+ operations R = can do read operations
+ W = can do write operations
+ U = can do unblank
+ flags E = it is enabled
+ C = it is prefered console
+ B = it is primary boot console
+ p = it is used for printk buffer
+ b = it is not a TTY but a Braille device
+ a = it is safe to use when cpu is offline
+ * = it is standard input of the reading process
+ major:minor major and minor number of the device separated by a colon
+
+If the reading process holds /dev/console open at the regular standard input
+stream the active device will be marked by an asterisk:
+
+ > cat /proc/tty/consoles < /dev/console
+ tty0 -WU (ECp*) 4:7
+ ttyS0 -W- (Ep) 4:64
+ > tty
+ /dev/pts/3
+
1.8 Miscellaneous kernel statistics in /proc/stat
-------------------------------------------------
diff --git a/fs/proc/proc_tty.c b/fs/proc/proc_tty.c
index 83adcc86943742ef58bf22b4fb16a986a560450e..dc44f94022f1d59d97aace13031a4f9e1030de2e 100644
--- a/fs/proc/proc_tty.c
+++ b/fs/proc/proc_tty.c
@@ -12,7 +12,10 @@
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/console.h>
#include <linux/seq_file.h>
+#include <linux/fdtable.h>
#include <linux/bitops.h>
/*
@@ -136,6 +139,160 @@ static const struct file_operations proc_tty_drivers_operations = {
.release = seq_release,
};
+/*
+ * The device ID of file descriptor 0 of the current reading
+ * task if a character device...
+ */
+static dev_t current_dev;
+
+/*
+ * This is the handler for /proc/tty/consoles
+ */
+static int show_console_dev(struct seq_file *m, void *v)
+{
+ const struct tty_driver *driver;
+ struct console *con;
+ int index, len;
+ char flags[10];
+ dev_t dev;
+
+ if (v == SEQ_START_TOKEN)
+ return 0;
+ con = (struct console *)v;
+ if (!con)
+ return 0;
+ driver = con->device(con, &index);
+ if (!driver)
+ return 0;
+ dev = MKDEV(driver->major, driver->minor_start) + index;
+
+ index = 0;
+ if (con->flags & CON_ENABLED)
+ flags[index++] = 'E';
+ if (con->flags & CON_CONSDEV)
+ flags[index++] = 'C';
+ if (con->flags & CON_BOOT)
+ flags[index++] = 'B';
+ if (con->flags & CON_PRINTBUFFER)
+ flags[index++] = 'p';
+ if (con->flags & CON_BRL)
+ flags[index++] = 'b';
+ if (con->flags & CON_ANYTIME)
+ flags[index++] = 'a';
+ if (current_dev == dev)
+ flags[index++] = '*';
+ flags[index] = 0;
+
+ seq_printf(m, "%s%d%n", con->name, con->index, &len);
+ len = 21 - len;
+ if (len < 1)
+ len = 1;
+ seq_printf(m, "%*c", len, ' ');
+ seq_printf(m, "%c%c%c (%s)%n", con->read ? 'R' : '-',
+ con->write ? 'W' : '-', con->unblank ? 'U' : '-',
+ flags, &len);
+ len = 13 - len;
+ if (len < 1)
+ len = 1;
+ seq_printf(m, "%*c%4d:%d\n", len, ' ', MAJOR(dev), MINOR(dev));
+
+ return 0;
+}
+
+/* iterator for consoles */
+static void *c_start(struct seq_file *m, loff_t *pos)
+{
+ struct console *con;
+ loff_t off = 0;
+
+ if (*pos == 0)
+ return SEQ_START_TOKEN;
+
+ acquire_console_sem();
+ for (con = console_drivers; con; con = con->next) {
+ if (!con->device)
+ continue;
+ if (++off == *pos)
+ break;
+ }
+ release_console_sem();
+
+ return con;
+}
+
+static void *c_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ struct console *con;
+
+ acquire_console_sem();
+ if (v == SEQ_START_TOKEN)
+ con = console_drivers;
+ else
+ con = ((struct console *)v)->next;
+ for (; con; con = con->next) {
+ if (!con->device)
+ continue;
+ ++*pos;
+ break;
+ }
+ release_console_sem();
+
+ return con;
+}
+
+static void c_stop(struct seq_file *m, void *v)
+{
+}
+
+static const struct seq_operations tty_consoles_op = {
+ .start = c_start,
+ .next = c_next,
+ .stop = c_stop,
+ .show = show_console_dev
+};
+
+/*
+ * Used for open /proc/tty/consoles. Before this detect
+ * the device ID of file descriptor 0 of the current
+ * reading task if a character device...
+ */
+static int tty_consoles_open(struct inode *inode, struct file *file)
+{
+ struct files_struct *curfiles;
+
+ current_dev = 0;
+ curfiles = get_files_struct(current);
+ if (curfiles) {
+ const struct file *curfp;
+ spin_lock(&curfiles->file_lock);
+ curfp = fcheck_files(curfiles, 0);
+ if (curfp && curfp->private_data) {
+ const struct inode *inode;
+ dget(curfp->f_dentry);
+ inode = curfp->f_dentry->d_inode;
+ if (S_ISCHR(inode->i_mode)) {
+ struct tty_struct *tty;
+ tty = (struct tty_struct *)curfp->private_data;
+ if (tty && tty->magic == TTY_MAGIC) {
+ tty = tty_pair_get_tty(tty);
+ current_dev = tty_devnum(tty);
+ }
+ }
+ dput(curfp->f_dentry);
+ }
+ spin_unlock(&curfiles->file_lock);
+ put_files_struct(curfiles);
+ }
+ return seq_open(file, &tty_consoles_op);
+}
+
+static const struct file_operations proc_tty_consoles_operations = {
+ .open = tty_consoles_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
/*
* This function is called by tty_register_driver() to handle
* registering the driver's /proc handler into /proc/tty/driver/<foo>
@@ -186,4 +343,5 @@ void __init proc_tty_init(void)
proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR|S_IXUSR, NULL);
proc_create("tty/ldiscs", 0, NULL, &tty_ldiscs_proc_fops);
proc_create("tty/drivers", 0, NULL, &proc_tty_drivers_operations);
+ proc_create("tty/consoles", 0, NULL, &proc_tty_consoles_operations);
}