From: Linus Torvalds Date: Sat, 23 Oct 2010 15:14:12 +0000 (-0700) Subject: Revert "tty: Add a new file /proc/tty/consoles" X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=6c2754c28f2388a276fe21edde826f2113c8f60e;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git Revert "tty: Add a new file /proc/tty/consoles" This reverts commit f4a3e0bceb57466c31757f25e4e0ed108d1299ec. Jiri Sladby points out that the tty structure we're using may already be gone, and Al Viro doesn't hold back in complaining about the random loading of 'filp->private_data' which doesn't have to be a pointer at all, nor does checking the magic field for TTY_MAGIC prove anything. Belated review by Al: "a) global variable depending on stdin of the last opener? Affecting output of read(2)? Really? b) iterator is broken; list should be locked in ->start(), unlocked in ->stop() and *NOT* unlocked/relocked in ->next() c) ->show() ought to do nothing in case of ->device == NULL, instead of skipping those in ->next()/->start() d) regardless of the merits of the bright idea about asterisk at that line in output *and* regardless of (a), the implementation is not only atrociously ugly, it's actually very likely to be a roothole. Verifying that Cthulhu knows what number happens to be address of a tty_struct by blindly dereferencing memory at that address... Ouch. Please revert that crap." And Christoph pipes in and NAK's the approach of walking fd tables etc too. So it's pretty unanimous. Noticed-by: Jri Slaby Requested-by: Al Viro Cc: Greg Kroah-Hartman Cc: Werner Fink Cc: Alan Cox Cc: Christoph Hellwig Signed-off-by: Linus Torvalds --- diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 98223a676940..a6aca8740883 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -1075,7 +1075,6 @@ 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 @@ -1094,37 +1093,6 @@ 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 dc44f94022f1..83adcc869437 100644 --- a/fs/proc/proc_tty.c +++ b/fs/proc/proc_tty.c @@ -12,10 +12,7 @@ #include #include #include -#include -#include #include -#include #include /* @@ -139,160 +136,6 @@ 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/ @@ -343,5 +186,4 @@ 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); }