android_kernel_motorola_sm6225/drivers/s390/char/sclp_tty.c
Heiko Carstens 5e34599fc8 [S390] sclp_tty: Fix scheduling while atomic bug.
Finally fixes a possible scheduling while in atomic context bug. The driver
used to wait on a waitqueue if no empty buffer was available. This could
lead to a deadlock if the driver was called from non-schedulable context.
So fix this. The write operation may fail now. It returns the number of
characters accepted. put_char will never fail, since it writes characters
to an intermediate buffer which gets flushed as soon as it is full.
That means the driver now can busy wait if something is in the intermediate
buffer and a write_string operation follows. Seems to be an acceptable
compromise, since that shouldn't happen too often.

Cc: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
2008-07-14 10:02:25 +02:00

621 lines
16 KiB
C

/*
* drivers/s390/char/sclp_tty.c
* SCLP line mode terminal driver.
*
* S390 version
* Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
* Author(s): Martin Peschke <mpeschke@de.ibm.com>
* Martin Schwidefsky <schwidefsky@de.ibm.com>
*/
#include <linux/module.h>
#include <linux/kmod.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <asm/uaccess.h>
#include "ctrlchar.h"
#include "sclp.h"
#include "sclp_rw.h"
#include "sclp_tty.h"
/*
* size of a buffer that collects single characters coming in
* via sclp_tty_put_char()
*/
#define SCLP_TTY_BUF_SIZE 512
/*
* There is exactly one SCLP terminal, so we can keep things simple
* and allocate all variables statically.
*/
/* Lock to guard over changes to global variables. */
static spinlock_t sclp_tty_lock;
/* List of free pages that can be used for console output buffering. */
static struct list_head sclp_tty_pages;
/* List of full struct sclp_buffer structures ready for output. */
static struct list_head sclp_tty_outqueue;
/* Counter how many buffers are emitted. */
static int sclp_tty_buffer_count;
/* Pointer to current console buffer. */
static struct sclp_buffer *sclp_ttybuf;
/* Timer for delayed output of console messages. */
static struct timer_list sclp_tty_timer;
static struct tty_struct *sclp_tty;
static unsigned char sclp_tty_chars[SCLP_TTY_BUF_SIZE];
static unsigned short int sclp_tty_chars_count;
struct tty_driver *sclp_tty_driver;
static int sclp_tty_tolower;
static int sclp_tty_columns = 80;
#define SPACES_PER_TAB 8
#define CASE_DELIMITER 0x6c /* to separate upper and lower case (% in EBCDIC) */
/* This routine is called whenever we try to open a SCLP terminal. */
static int
sclp_tty_open(struct tty_struct *tty, struct file *filp)
{
sclp_tty = tty;
tty->driver_data = NULL;
tty->low_latency = 0;
return 0;
}
/* This routine is called when the SCLP terminal is closed. */
static void
sclp_tty_close(struct tty_struct *tty, struct file *filp)
{
if (tty->count > 1)
return;
sclp_tty = NULL;
}
/*
* This routine returns the numbers of characters the tty driver
* will accept for queuing to be written. This number is subject
* to change as output buffers get emptied, or if the output flow
* control is acted. This is not an exact number because not every
* character needs the same space in the sccb. The worst case is
* a string of newlines. Every newlines creates a new mto which
* needs 8 bytes.
*/
static int
sclp_tty_write_room (struct tty_struct *tty)
{
unsigned long flags;
struct list_head *l;
int count;
spin_lock_irqsave(&sclp_tty_lock, flags);
count = 0;
if (sclp_ttybuf != NULL)
count = sclp_buffer_space(sclp_ttybuf) / sizeof(struct mto);
list_for_each(l, &sclp_tty_pages)
count += NR_EMPTY_MTO_PER_SCCB;
spin_unlock_irqrestore(&sclp_tty_lock, flags);
return count;
}
static void
sclp_ttybuf_callback(struct sclp_buffer *buffer, int rc)
{
unsigned long flags;
void *page;
do {
page = sclp_unmake_buffer(buffer);
spin_lock_irqsave(&sclp_tty_lock, flags);
/* Remove buffer from outqueue */
list_del(&buffer->list);
sclp_tty_buffer_count--;
list_add_tail((struct list_head *) page, &sclp_tty_pages);
/* Check if there is a pending buffer on the out queue. */
buffer = NULL;
if (!list_empty(&sclp_tty_outqueue))
buffer = list_entry(sclp_tty_outqueue.next,
struct sclp_buffer, list);
spin_unlock_irqrestore(&sclp_tty_lock, flags);
} while (buffer && sclp_emit_buffer(buffer, sclp_ttybuf_callback));
/* check if the tty needs a wake up call */
if (sclp_tty != NULL) {
tty_wakeup(sclp_tty);
}
}
static inline void
__sclp_ttybuf_emit(struct sclp_buffer *buffer)
{
unsigned long flags;
int count;
int rc;
spin_lock_irqsave(&sclp_tty_lock, flags);
list_add_tail(&buffer->list, &sclp_tty_outqueue);
count = sclp_tty_buffer_count++;
spin_unlock_irqrestore(&sclp_tty_lock, flags);
if (count)
return;
rc = sclp_emit_buffer(buffer, sclp_ttybuf_callback);
if (rc)
sclp_ttybuf_callback(buffer, rc);
}
/*
* When this routine is called from the timer then we flush the
* temporary write buffer.
*/
static void
sclp_tty_timeout(unsigned long data)
{
unsigned long flags;
struct sclp_buffer *buf;
spin_lock_irqsave(&sclp_tty_lock, flags);
buf = sclp_ttybuf;
sclp_ttybuf = NULL;
spin_unlock_irqrestore(&sclp_tty_lock, flags);
if (buf != NULL) {
__sclp_ttybuf_emit(buf);
}
}
/*
* Write a string to the sclp tty.
*/
static int sclp_tty_write_string(const unsigned char *str, int count, int may_fail)
{
unsigned long flags;
void *page;
int written;
int overall_written;
struct sclp_buffer *buf;
if (count <= 0)
return 0;
overall_written = 0;
spin_lock_irqsave(&sclp_tty_lock, flags);
do {
/* Create a sclp output buffer if none exists yet */
if (sclp_ttybuf == NULL) {
while (list_empty(&sclp_tty_pages)) {
spin_unlock_irqrestore(&sclp_tty_lock, flags);
if (may_fail)
goto out;
else
sclp_sync_wait();
spin_lock_irqsave(&sclp_tty_lock, flags);
}
page = sclp_tty_pages.next;
list_del((struct list_head *) page);
sclp_ttybuf = sclp_make_buffer(page, sclp_tty_columns,
SPACES_PER_TAB);
}
/* try to write the string to the current output buffer */
written = sclp_write(sclp_ttybuf, str, count);
overall_written += written;
if (written == count)
break;
/*
* Not all characters could be written to the current
* output buffer. Emit the buffer, create a new buffer
* and then output the rest of the string.
*/
buf = sclp_ttybuf;
sclp_ttybuf = NULL;
spin_unlock_irqrestore(&sclp_tty_lock, flags);
__sclp_ttybuf_emit(buf);
spin_lock_irqsave(&sclp_tty_lock, flags);
str += written;
count -= written;
} while (count > 0);
/* Setup timer to output current console buffer after 1/10 second */
if (sclp_ttybuf && sclp_chars_in_buffer(sclp_ttybuf) &&
!timer_pending(&sclp_tty_timer)) {
init_timer(&sclp_tty_timer);
sclp_tty_timer.function = sclp_tty_timeout;
sclp_tty_timer.data = 0UL;
sclp_tty_timer.expires = jiffies + HZ/10;
add_timer(&sclp_tty_timer);
}
spin_unlock_irqrestore(&sclp_tty_lock, flags);
out:
return overall_written;
}
/*
* This routine is called by the kernel to write a series of characters to the
* tty device. The characters may come from user space or kernel space. This
* routine will return the number of characters actually accepted for writing.
*/
static int
sclp_tty_write(struct tty_struct *tty, const unsigned char *buf, int count)
{
if (sclp_tty_chars_count > 0) {
sclp_tty_write_string(sclp_tty_chars, sclp_tty_chars_count, 0);
sclp_tty_chars_count = 0;
}
return sclp_tty_write_string(buf, count, 1);
}
/*
* This routine is called by the kernel to write a single character to the tty
* device. If the kernel uses this routine, it must call the flush_chars()
* routine (if defined) when it is done stuffing characters into the driver.
*
* Characters provided to sclp_tty_put_char() are buffered by the SCLP driver.
* If the given character is a '\n' the contents of the SCLP write buffer
* - including previous characters from sclp_tty_put_char() and strings from
* sclp_write() without final '\n' - will be written.
*/
static int
sclp_tty_put_char(struct tty_struct *tty, unsigned char ch)
{
sclp_tty_chars[sclp_tty_chars_count++] = ch;
if (ch == '\n' || sclp_tty_chars_count >= SCLP_TTY_BUF_SIZE) {
sclp_tty_write_string(sclp_tty_chars, sclp_tty_chars_count, 0);
sclp_tty_chars_count = 0;
}
return 1;
}
/*
* This routine is called by the kernel after it has written a series of
* characters to the tty device using put_char().
*/
static void
sclp_tty_flush_chars(struct tty_struct *tty)
{
if (sclp_tty_chars_count > 0) {
sclp_tty_write_string(sclp_tty_chars, sclp_tty_chars_count, 0);
sclp_tty_chars_count = 0;
}
}
/*
* This routine returns the number of characters in the write buffer of the
* SCLP driver. The provided number includes all characters that are stored
* in the SCCB (will be written next time the SCLP is not busy) as well as
* characters in the write buffer (will not be written as long as there is a
* final line feed missing).
*/
static int
sclp_tty_chars_in_buffer(struct tty_struct *tty)
{
unsigned long flags;
struct list_head *l;
struct sclp_buffer *t;
int count;
spin_lock_irqsave(&sclp_tty_lock, flags);
count = 0;
if (sclp_ttybuf != NULL)
count = sclp_chars_in_buffer(sclp_ttybuf);
list_for_each(l, &sclp_tty_outqueue) {
t = list_entry(l, struct sclp_buffer, list);
count += sclp_chars_in_buffer(t);
}
spin_unlock_irqrestore(&sclp_tty_lock, flags);
return count;
}
/*
* removes all content from buffers of low level driver
*/
static void
sclp_tty_flush_buffer(struct tty_struct *tty)
{
if (sclp_tty_chars_count > 0) {
sclp_tty_write_string(sclp_tty_chars, sclp_tty_chars_count, 0);
sclp_tty_chars_count = 0;
}
}
/*
* push input to tty
*/
static void
sclp_tty_input(unsigned char* buf, unsigned int count)
{
unsigned int cchar;
/*
* If this tty driver is currently closed
* then throw the received input away.
*/
if (sclp_tty == NULL)
return;
cchar = ctrlchar_handle(buf, count, sclp_tty);
switch (cchar & CTRLCHAR_MASK) {
case CTRLCHAR_SYSRQ:
break;
case CTRLCHAR_CTRL:
tty_insert_flip_char(sclp_tty, cchar, TTY_NORMAL);
tty_flip_buffer_push(sclp_tty);
break;
case CTRLCHAR_NONE:
/* send (normal) input to line discipline */
if (count < 2 ||
(strncmp((const char *) buf + count - 2, "^n", 2) &&
strncmp((const char *) buf + count - 2, "\252n", 2))) {
/* add the auto \n */
tty_insert_flip_string(sclp_tty, buf, count);
tty_insert_flip_char(sclp_tty, '\n', TTY_NORMAL);
} else
tty_insert_flip_string(sclp_tty, buf, count - 2);
tty_flip_buffer_push(sclp_tty);
break;
}
}
/*
* get a EBCDIC string in upper/lower case,
* find out characters in lower/upper case separated by a special character,
* modifiy original string,
* returns length of resulting string
*/
static int sclp_switch_cases(unsigned char *buf, int count)
{
unsigned char *ip, *op;
int toggle;
/* initially changing case is off */
toggle = 0;
ip = op = buf;
while (count-- > 0) {
/* compare with special character */
if (*ip == CASE_DELIMITER) {
/* followed by another special character? */
if (count && ip[1] == CASE_DELIMITER) {
/*
* ... then put a single copy of the special
* character to the output string
*/
*op++ = *ip++;
count--;
} else
/*
* ... special character follower by a normal
* character toggles the case change behaviour
*/
toggle = ~toggle;
/* skip special character */
ip++;
} else
/* not the special character */
if (toggle)
/* but case switching is on */
if (sclp_tty_tolower)
/* switch to uppercase */
*op++ = _ebc_toupper[(int) *ip++];
else
/* switch to lowercase */
*op++ = _ebc_tolower[(int) *ip++];
else
/* no case switching, copy the character */
*op++ = *ip++;
}
/* return length of reformatted string. */
return op - buf;
}
static void
sclp_get_input(unsigned char *start, unsigned char *end)
{
int count;
count = end - start;
if (sclp_tty_tolower)
EBC_TOLOWER(start, count);
count = sclp_switch_cases(start, count);
/* convert EBCDIC to ASCII (modify original input in SCCB) */
sclp_ebcasc_str(start, count);
/* transfer input to high level driver */
sclp_tty_input(start, count);
}
static inline struct gds_vector *
find_gds_vector(struct gds_vector *start, struct gds_vector *end, u16 id)
{
struct gds_vector *vec;
for (vec = start; vec < end; vec = (void *) vec + vec->length)
if (vec->gds_id == id)
return vec;
return NULL;
}
static inline struct gds_subvector *
find_gds_subvector(struct gds_subvector *start,
struct gds_subvector *end, u8 key)
{
struct gds_subvector *subvec;
for (subvec = start; subvec < end;
subvec = (void *) subvec + subvec->length)
if (subvec->key == key)
return subvec;
return NULL;
}
static inline void
sclp_eval_selfdeftextmsg(struct gds_subvector *start,
struct gds_subvector *end)
{
struct gds_subvector *subvec;
subvec = start;
while (subvec < end) {
subvec = find_gds_subvector(subvec, end, 0x30);
if (!subvec)
break;
sclp_get_input((unsigned char *)(subvec + 1),
(unsigned char *) subvec + subvec->length);
subvec = (void *) subvec + subvec->length;
}
}
static inline void
sclp_eval_textcmd(struct gds_subvector *start,
struct gds_subvector *end)
{
struct gds_subvector *subvec;
subvec = start;
while (subvec < end) {
subvec = find_gds_subvector(subvec, end,
GDS_KEY_SELFDEFTEXTMSG);
if (!subvec)
break;
sclp_eval_selfdeftextmsg((struct gds_subvector *)(subvec + 1),
(void *)subvec + subvec->length);
subvec = (void *) subvec + subvec->length;
}
}
static inline void
sclp_eval_cpmsu(struct gds_vector *start, struct gds_vector *end)
{
struct gds_vector *vec;
vec = start;
while (vec < end) {
vec = find_gds_vector(vec, end, GDS_ID_TEXTCMD);
if (!vec)
break;
sclp_eval_textcmd((struct gds_subvector *)(vec + 1),
(void *) vec + vec->length);
vec = (void *) vec + vec->length;
}
}
static inline void
sclp_eval_mdsmu(struct gds_vector *start, void *end)
{
struct gds_vector *vec;
vec = find_gds_vector(start, end, GDS_ID_CPMSU);
if (vec)
sclp_eval_cpmsu(vec + 1, (void *) vec + vec->length);
}
static void
sclp_tty_receiver(struct evbuf_header *evbuf)
{
struct gds_vector *start, *end, *vec;
start = (struct gds_vector *)(evbuf + 1);
end = (void *) evbuf + evbuf->length;
vec = find_gds_vector(start, end, GDS_ID_MDSMU);
if (vec)
sclp_eval_mdsmu(vec + 1, (void *) vec + vec->length);
}
static void
sclp_tty_state_change(struct sclp_register *reg)
{
}
static struct sclp_register sclp_input_event =
{
.receive_mask = EVTYP_OPCMD_MASK | EVTYP_PMSGCMD_MASK,
.state_change_fn = sclp_tty_state_change,
.receiver_fn = sclp_tty_receiver
};
static const struct tty_operations sclp_ops = {
.open = sclp_tty_open,
.close = sclp_tty_close,
.write = sclp_tty_write,
.put_char = sclp_tty_put_char,
.flush_chars = sclp_tty_flush_chars,
.write_room = sclp_tty_write_room,
.chars_in_buffer = sclp_tty_chars_in_buffer,
.flush_buffer = sclp_tty_flush_buffer,
};
static int __init
sclp_tty_init(void)
{
struct tty_driver *driver;
void *page;
int i;
int rc;
if (!CONSOLE_IS_SCLP)
return 0;
driver = alloc_tty_driver(1);
if (!driver)
return -ENOMEM;
rc = sclp_rw_init();
if (rc) {
put_tty_driver(driver);
return rc;
}
/* Allocate pages for output buffering */
INIT_LIST_HEAD(&sclp_tty_pages);
for (i = 0; i < MAX_KMEM_PAGES; i++) {
page = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
if (page == NULL) {
put_tty_driver(driver);
return -ENOMEM;
}
list_add_tail((struct list_head *) page, &sclp_tty_pages);
}
INIT_LIST_HEAD(&sclp_tty_outqueue);
spin_lock_init(&sclp_tty_lock);
init_timer(&sclp_tty_timer);
sclp_ttybuf = NULL;
sclp_tty_buffer_count = 0;
if (MACHINE_IS_VM) {
/*
* save 4 characters for the CPU number
* written at start of each line by VM/CP
*/
sclp_tty_columns = 76;
/* case input lines to lowercase */
sclp_tty_tolower = 1;
}
sclp_tty_chars_count = 0;
sclp_tty = NULL;
rc = sclp_register(&sclp_input_event);
if (rc) {
put_tty_driver(driver);
return rc;
}
driver->owner = THIS_MODULE;
driver->driver_name = "sclp_line";
driver->name = "sclp_line";
driver->major = TTY_MAJOR;
driver->minor_start = 64;
driver->type = TTY_DRIVER_TYPE_SYSTEM;
driver->subtype = SYSTEM_TYPE_TTY;
driver->init_termios = tty_std_termios;
driver->init_termios.c_iflag = IGNBRK | IGNPAR;
driver->init_termios.c_oflag = ONLCR | XTABS;
driver->init_termios.c_lflag = ISIG | ECHO;
driver->flags = TTY_DRIVER_REAL_RAW;
tty_set_operations(driver, &sclp_ops);
rc = tty_register_driver(driver);
if (rc) {
put_tty_driver(driver);
return rc;
}
sclp_tty_driver = driver;
return 0;
}
module_init(sclp_tty_init);