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-rw-r--r--drivers/tty/Kconfig14
-rw-r--r--drivers/tty/Makefile3
-rw-r--r--drivers/tty/ttynull.c18
-rw-r--r--include/linux/console.h3
-rw-r--r--init/main.c10
-rw-r--r--kernel/printk/printk.c257
-rw-r--r--kernel/printk/printk_ringbuffer.c32
7 files changed, 200 insertions, 137 deletions
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index e15cd6b5bb99..47a6e42f0d04 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -401,20 +401,6 @@ config MIPS_EJTAG_FDC_KGDB_CHAN
help
FDC channel number to use for KGDB.
-config NULL_TTY
- tristate "NULL TTY driver"
- help
- Say Y here if you want a NULL TTY which simply discards messages.
-
- This is useful to allow userspace applications which expect a console
- device to work without modifications even when no console is
- available or desired.
-
- In order to use this driver, you should redirect the console to this
- TTY, or boot the kernel with console=ttynull.
-
- If unsure, say N.
-
config TRACE_ROUTER
tristate "Trace data router for MIPI P1149.7 cJTAG standard"
depends on TRACE_SINK
diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
index b3ccae932660..3c1c5a9240a7 100644
--- a/drivers/tty/Makefile
+++ b/drivers/tty/Makefile
@@ -2,7 +2,7 @@
obj-$(CONFIG_TTY) += tty_io.o n_tty.o tty_ioctl.o tty_ldisc.o \
tty_buffer.o tty_port.o tty_mutex.o \
tty_ldsem.o tty_baudrate.o tty_jobctrl.o \
- n_null.o
+ n_null.o ttynull.o
obj-$(CONFIG_LEGACY_PTYS) += pty.o
obj-$(CONFIG_UNIX98_PTYS) += pty.o
obj-$(CONFIG_AUDIT) += tty_audit.o
@@ -25,7 +25,6 @@ obj-$(CONFIG_ISI) += isicom.o
obj-$(CONFIG_MOXA_INTELLIO) += moxa.o
obj-$(CONFIG_MOXA_SMARTIO) += mxser.o
obj-$(CONFIG_NOZOMI) += nozomi.o
-obj-$(CONFIG_NULL_TTY) += ttynull.o
obj-$(CONFIG_ROCKETPORT) += rocket.o
obj-$(CONFIG_SYNCLINK_GT) += synclink_gt.o
obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.o
diff --git a/drivers/tty/ttynull.c b/drivers/tty/ttynull.c
index 17f05b7eb6d3..eced70ec54e1 100644
--- a/drivers/tty/ttynull.c
+++ b/drivers/tty/ttynull.c
@@ -2,6 +2,13 @@
/*
* Copyright (C) 2019 Axis Communications AB
*
+ * The console is useful for userspace applications which expect a console
+ * device to work without modifications even when no console is available
+ * or desired.
+ *
+ * In order to use this driver, you should redirect the console to this
+ * TTY, or boot the kernel with console=ttynull.
+ *
* Based on ttyprintk.c:
* Copyright (C) 2010 Samo Pogacnik
*/
@@ -59,6 +66,17 @@ static struct console ttynull_console = {
.device = ttynull_device,
};
+void __init register_ttynull_console(void)
+{
+ if (!ttynull_driver)
+ return;
+
+ if (add_preferred_console(ttynull_console.name, 0, NULL))
+ return;
+
+ register_console(&ttynull_console);
+}
+
static int __init ttynull_init(void)
{
struct tty_driver *driver;
diff --git a/include/linux/console.h b/include/linux/console.h
index 20874db50bc8..dbe78e8e2602 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -186,9 +186,12 @@ extern int braille_register_console(struct console *, int index,
extern int braille_unregister_console(struct console *);
#ifdef CONFIG_TTY
extern void console_sysfs_notify(void);
+extern void register_ttynull_console(void);
#else
static inline void console_sysfs_notify(void)
{ }
+static inline void register_ttynull_console(void)
+{ }
#endif
extern bool console_suspend_enabled;
diff --git a/init/main.c b/init/main.c
index 3024c4db17a9..6feee7f11eaf 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1480,8 +1480,14 @@ void __init console_on_rootfs(void)
struct file *file = filp_open("/dev/console", O_RDWR, 0);
if (IS_ERR(file)) {
- pr_err("Warning: unable to open an initial console.\n");
- return;
+ pr_err("Warning: unable to open an initial console. Fallback to ttynull.\n");
+ register_ttynull_console();
+
+ file = filp_open("/dev/console", O_RDWR, 0);
+ if (IS_ERR(file)) {
+ pr_err("Warning: Failed to add ttynull console. No stdin, stdout, and stderr for the init process!\n");
+ return;
+ }
}
init_dup(file);
init_dup(file);
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 28713dda3f6b..ffdd0dc7ec6d 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -491,52 +491,6 @@ static void truncate_msg(u16 *text_len, u16 *trunc_msg_len)
*trunc_msg_len = 0;
}
-/* insert record into the buffer, discard old ones, update heads */
-static int log_store(u32 caller_id, int facility, int level,
- enum log_flags flags, u64 ts_nsec,
- const struct dev_printk_info *dev_info,
- const char *text, u16 text_len)
-{
- struct prb_reserved_entry e;
- struct printk_record r;
- u16 trunc_msg_len = 0;
-
- prb_rec_init_wr(&r, text_len);
-
- if (!prb_reserve(&e, prb, &r)) {
- /* truncate the message if it is too long for empty buffer */
- truncate_msg(&text_len, &trunc_msg_len);
- prb_rec_init_wr(&r, text_len + trunc_msg_len);
- /* survive when the log buffer is too small for trunc_msg */
- if (!prb_reserve(&e, prb, &r))
- return 0;
- }
-
- /* fill message */
- memcpy(&r.text_buf[0], text, text_len);
- if (trunc_msg_len)
- memcpy(&r.text_buf[text_len], trunc_msg, trunc_msg_len);
- r.info->text_len = text_len + trunc_msg_len;
- r.info->facility = facility;
- r.info->level = level & 7;
- r.info->flags = flags & 0x1f;
- if (ts_nsec > 0)
- r.info->ts_nsec = ts_nsec;
- else
- r.info->ts_nsec = local_clock();
- r.info->caller_id = caller_id;
- if (dev_info)
- memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info));
-
- /* A message without a trailing newline can be continued. */
- if (!(flags & LOG_NEWLINE))
- prb_commit(&e);
- else
- prb_final_commit(&e);
-
- return (text_len + trunc_msg_len);
-}
-
int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
static int syslog_action_restricted(int type)
@@ -741,7 +695,6 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
if (LOG_FACILITY(u) != 0)
facility = LOG_FACILITY(u);
endp++;
- len -= endp - line;
line = endp;
}
}
@@ -1172,7 +1125,7 @@ void __init setup_log_buf(int early)
new_descs, ilog2(new_descs_count),
new_infos);
- logbuf_lock_irqsave(flags);
+ printk_safe_enter_irqsave(flags);
log_buf_len = new_log_buf_len;
log_buf = new_log_buf;
@@ -1189,7 +1142,7 @@ void __init setup_log_buf(int early)
*/
prb = &printk_rb_dynamic;
- logbuf_unlock_irqrestore(flags);
+ printk_safe_exit_irqrestore(flags);
if (seq != prb_next_seq(&printk_rb_static)) {
pr_err("dropped %llu messages\n",
@@ -1907,83 +1860,177 @@ static inline u32 printk_caller_id(void)
0x80000000 + raw_smp_processor_id();
}
-static size_t log_output(int facility, int level, enum log_flags lflags,
- const struct dev_printk_info *dev_info,
- char *text, size_t text_len)
+/**
+ * parse_prefix - Parse level and control flags.
+ *
+ * @text: The terminated text message.
+ * @level: A pointer to the current level value, will be updated.
+ * @lflags: A pointer to the current log flags, will be updated.
+ *
+ * @level may be NULL if the caller is not interested in the parsed value.
+ * Otherwise the variable pointed to by @level must be set to
+ * LOGLEVEL_DEFAULT in order to be updated with the parsed value.
+ *
+ * @lflags may be NULL if the caller is not interested in the parsed value.
+ * Otherwise the variable pointed to by @lflags will be OR'd with the parsed
+ * value.
+ *
+ * Return: The length of the parsed level and control flags.
+ */
+static u16 parse_prefix(char *text, int *level, enum log_flags *lflags)
{
- const u32 caller_id = printk_caller_id();
+ u16 prefix_len = 0;
+ int kern_level;
- if (lflags & LOG_CONT) {
- struct prb_reserved_entry e;
- struct printk_record r;
+ while (*text) {
+ kern_level = printk_get_level(text);
+ if (!kern_level)
+ break;
- prb_rec_init_wr(&r, text_len);
- if (prb_reserve_in_last(&e, prb, &r, caller_id, LOG_LINE_MAX)) {
- memcpy(&r.text_buf[r.info->text_len], text, text_len);
- r.info->text_len += text_len;
- if (lflags & LOG_NEWLINE) {
- r.info->flags |= LOG_NEWLINE;
- prb_final_commit(&e);
- } else {
- prb_commit(&e);
- }
- return text_len;
+ switch (kern_level) {
+ case '0' ... '7':
+ if (level && *level == LOGLEVEL_DEFAULT)
+ *level = kern_level - '0';
+ break;
+ case 'c': /* KERN_CONT */
+ if (lflags)
+ *lflags |= LOG_CONT;
+ }
+
+ prefix_len += 2;
+ text += 2;
+ }
+
+ return prefix_len;
+}
+
+static u16 printk_sprint(char *text, u16 size, int facility, enum log_flags *lflags,
+ const char *fmt, va_list args)
+{
+ u16 text_len;
+
+ text_len = vscnprintf(text, size, fmt, args);
+
+ /* Mark and strip a trailing newline. */
+ if (text_len && text[text_len - 1] == '\n') {
+ text_len--;
+ *lflags |= LOG_NEWLINE;
+ }
+
+ /* Strip log level and control flags. */
+ if (facility == 0) {
+ u16 prefix_len;
+
+ prefix_len = parse_prefix(text, NULL, NULL);
+ if (prefix_len) {
+ text_len -= prefix_len;
+ memmove(text, text + prefix_len, text_len);
}
}
- /* Store it in the record log */
- return log_store(caller_id, facility, level, lflags, 0,
- dev_info, text, text_len);
+ return text_len;
}
-/* Must be called under logbuf_lock. */
+__printf(4, 0)
int vprintk_store(int facility, int level,
const struct dev_printk_info *dev_info,
const char *fmt, va_list args)
{
- static char textbuf[LOG_LINE_MAX];
- char *text = textbuf;
- size_t text_len;
+ const u32 caller_id = printk_caller_id();
+ struct prb_reserved_entry e;
enum log_flags lflags = 0;
+ struct printk_record r;
+ u16 trunc_msg_len = 0;
+ char prefix_buf[8];
+ u16 reserve_size;
+ va_list args2;
+ u16 text_len;
+ u64 ts_nsec;
/*
- * The printf needs to come first; we need the syslog
- * prefix which might be passed-in as a parameter.
+ * Since the duration of printk() can vary depending on the message
+ * and state of the ringbuffer, grab the timestamp now so that it is
+ * close to the call of printk(). This provides a more deterministic
+ * timestamp with respect to the caller.
*/
- text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
+ ts_nsec = local_clock();
- /* mark and strip a trailing newline */
- if (text_len && text[text_len-1] == '\n') {
- text_len--;
+ /*
+ * The sprintf needs to come first since the syslog prefix might be
+ * passed in as a parameter. An extra byte must be reserved so that
+ * later the vscnprintf() into the reserved buffer has room for the
+ * terminating '\0', which is not counted by vsnprintf().
+ */
+ va_copy(args2, args);
+ reserve_size = vsnprintf(&prefix_buf[0], sizeof(prefix_buf), fmt, args2) + 1;
+ va_end(args2);
+
+ if (reserve_size > LOG_LINE_MAX)
+ reserve_size = LOG_LINE_MAX;
+
+ /* Extract log level or control flags. */
+ if (facility == 0)
+ parse_prefix(&prefix_buf[0], &level, &lflags);
+
+ if (level == LOGLEVEL_DEFAULT)
+ level = default_message_loglevel;
+
+ if (dev_info)
lflags |= LOG_NEWLINE;
- }
- /* strip kernel syslog prefix and extract log level or control flags */
- if (facility == 0) {
- int kern_level;
+ if (lflags & LOG_CONT) {
+ prb_rec_init_wr(&r, reserve_size);
+ if (prb_reserve_in_last(&e, prb, &r, caller_id, LOG_LINE_MAX)) {
+ text_len = printk_sprint(&r.text_buf[r.info->text_len], reserve_size,
+ facility, &lflags, fmt, args);
+ r.info->text_len += text_len;
- while ((kern_level = printk_get_level(text)) != 0) {
- switch (kern_level) {
- case '0' ... '7':
- if (level == LOGLEVEL_DEFAULT)
- level = kern_level - '0';
- break;
- case 'c': /* KERN_CONT */
- lflags |= LOG_CONT;
+ if (lflags & LOG_NEWLINE) {
+ r.info->flags |= LOG_NEWLINE;
+ prb_final_commit(&e);
+ } else {
+ prb_commit(&e);
}
- text_len -= 2;
- text += 2;
+ return text_len;
}
}
- if (level == LOGLEVEL_DEFAULT)
- level = default_message_loglevel;
+ /*
+ * Explicitly initialize the record before every prb_reserve() call.
+ * prb_reserve_in_last() and prb_reserve() purposely invalidate the
+ * structure when they fail.
+ */
+ prb_rec_init_wr(&r, reserve_size);
+ if (!prb_reserve(&e, prb, &r)) {
+ /* truncate the message if it is too long for empty buffer */
+ truncate_msg(&reserve_size, &trunc_msg_len);
+
+ prb_rec_init_wr(&r, reserve_size + trunc_msg_len);
+ if (!prb_reserve(&e, prb, &r))
+ return 0;
+ }
+ /* fill message */
+ text_len = printk_sprint(&r.text_buf[0], reserve_size, facility, &lflags, fmt, args);
+ if (trunc_msg_len)
+ memcpy(&r.text_buf[text_len], trunc_msg, trunc_msg_len);
+ r.info->text_len = text_len + trunc_msg_len;
+ r.info->facility = facility;
+ r.info->level = level & 7;
+ r.info->flags = lflags & 0x1f;
+ r.info->ts_nsec = ts_nsec;
+ r.info->caller_id = caller_id;
if (dev_info)
- lflags |= LOG_NEWLINE;
+ memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info));
+
+ /* A message without a trailing newline can be continued. */
+ if (!(lflags & LOG_NEWLINE))
+ prb_commit(&e);
+ else
+ prb_final_commit(&e);
- return log_output(facility, level, lflags, dev_info, text, text_len);
+ return (text_len + trunc_msg_len);
}
asmlinkage int vprintk_emit(int facility, int level,
@@ -2006,10 +2053,9 @@ asmlinkage int vprintk_emit(int facility, int level,
boot_delay_msec(level);
printk_delay();
- /* This stops the holder of console_sem just where we want him */
- logbuf_lock_irqsave(flags);
+ printk_safe_enter_irqsave(flags);
printed_len = vprintk_store(facility, level, dev_info, fmt, args);
- logbuf_unlock_irqrestore(flags);
+ printk_safe_exit_irqrestore(flags);
/* If called from the scheduler, we can not call up(). */
if (!in_sched) {
@@ -2189,8 +2235,15 @@ static int __init console_setup(char *str)
char *s, *options, *brl_options = NULL;
int idx;
- if (str[0] == 0)
+ /*
+ * console="" or console=null have been suggested as a way to
+ * disable console output. Use ttynull that has been created
+ * for exacly this purpose.
+ */
+ if (str[0] == 0 || strcmp(str, "null") == 0) {
+ __add_preferred_console("ttynull", 0, NULL, NULL, true);
return 1;
+ }
if (_braille_console_setup(&str, &brl_options))
return 1;
diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c
index 74e25a1704f2..6704f06e0417 100644
--- a/kernel/printk/printk_ringbuffer.c
+++ b/kernel/printk/printk_ringbuffer.c
@@ -559,11 +559,12 @@ static void desc_make_reusable(struct prb_desc_ring *desc_ring,
* on error the caller can re-load the tail lpos to determine the situation.
*/
static bool data_make_reusable(struct printk_ringbuffer *rb,
- struct prb_data_ring *data_ring,
unsigned long lpos_begin,
unsigned long lpos_end,
unsigned long *lpos_out)
{
+
+ struct prb_data_ring *data_ring = &rb->text_data_ring;
struct prb_desc_ring *desc_ring = &rb->desc_ring;
struct prb_data_block *blk;
enum desc_state d_state;
@@ -625,10 +626,9 @@ static bool data_make_reusable(struct printk_ringbuffer *rb,
* descriptors into the reusable state if the tail is pushed beyond
* their associated data block.
*/
-static bool data_push_tail(struct printk_ringbuffer *rb,
- struct prb_data_ring *data_ring,
- unsigned long lpos)
+static bool data_push_tail(struct printk_ringbuffer *rb, unsigned long lpos)
{
+ struct prb_data_ring *data_ring = &rb->text_data_ring;
unsigned long tail_lpos_new;
unsigned long tail_lpos;
unsigned long next_lpos;
@@ -669,8 +669,7 @@ static bool data_push_tail(struct printk_ringbuffer *rb,
* Make all descriptors reusable that are associated with
* data blocks before @lpos.
*/
- if (!data_make_reusable(rb, data_ring, tail_lpos, lpos,
- &next_lpos)) {
+ if (!data_make_reusable(rb, tail_lpos, lpos, &next_lpos)) {
/*
* 1. Guarantee the block ID loaded in
* data_make_reusable() is performed before
@@ -807,7 +806,7 @@ static bool desc_push_tail(struct printk_ringbuffer *rb,
* data blocks once their associated descriptor is gone.
*/
- if (!data_push_tail(rb, &rb->text_data_ring, desc.text_blk_lpos.next))
+ if (!data_push_tail(rb, desc.text_blk_lpos.next))
return false;
/*
@@ -1019,10 +1018,10 @@ static unsigned long get_next_lpos(struct prb_data_ring *data_ring,
* if necessary. This function also associates the data block with
* a specified descriptor.
*/
-static char *data_alloc(struct printk_ringbuffer *rb,
- struct prb_data_ring *data_ring, unsigned int size,
+static char *data_alloc(struct printk_ringbuffer *rb, unsigned int size,
struct prb_data_blk_lpos *blk_lpos, unsigned long id)
{
+ struct prb_data_ring *data_ring = &rb->text_data_ring;
struct prb_data_block *blk;
unsigned long begin_lpos;
unsigned long next_lpos;
@@ -1041,7 +1040,7 @@ static char *data_alloc(struct printk_ringbuffer *rb,
do {
next_lpos = get_next_lpos(data_ring, begin_lpos, size);
- if (!data_push_tail(rb, data_ring, next_lpos - DATA_SIZE(data_ring))) {
+ if (!data_push_tail(rb, next_lpos - DATA_SIZE(data_ring))) {
/* Failed to allocate, specify a data-less block. */
blk_lpos->begin = FAILED_LPOS;
blk_lpos->next = FAILED_LPOS;
@@ -1100,10 +1099,10 @@ static char *data_alloc(struct printk_ringbuffer *rb,
* Return a pointer to the beginning of the entire data buffer or NULL on
* failure.
*/
-static char *data_realloc(struct printk_ringbuffer *rb,
- struct prb_data_ring *data_ring, unsigned int size,
+static char *data_realloc(struct printk_ringbuffer *rb, unsigned int size,
struct prb_data_blk_lpos *blk_lpos, unsigned long id)
{
+ struct prb_data_ring *data_ring = &rb->text_data_ring;
struct prb_data_block *blk;
unsigned long head_lpos;
unsigned long next_lpos;
@@ -1130,7 +1129,7 @@ static char *data_realloc(struct printk_ringbuffer *rb,
return &blk->data[0];
}
- if (!data_push_tail(rb, data_ring, next_lpos - DATA_SIZE(data_ring)))
+ if (!data_push_tail(rb, next_lpos - DATA_SIZE(data_ring)))
return NULL;
/* The memory barrier involvement is the same as data_alloc:A. */
@@ -1395,7 +1394,7 @@ bool prb_reserve_in_last(struct prb_reserved_entry *e, struct printk_ringbuffer
if (r->text_buf_size > max_size)
goto fail;
- r->text_buf = data_alloc(rb, &rb->text_data_ring, r->text_buf_size,
+ r->text_buf = data_alloc(rb, r->text_buf_size,
&d->text_blk_lpos, id);
} else {
if (!get_data(&rb->text_data_ring, &d->text_blk_lpos, &data_size))
@@ -1419,7 +1418,7 @@ bool prb_reserve_in_last(struct prb_reserved_entry *e, struct printk_ringbuffer
if (r->text_buf_size > max_size)
goto fail;
- r->text_buf = data_realloc(rb, &rb->text_data_ring, r->text_buf_size,
+ r->text_buf = data_realloc(rb, r->text_buf_size,
&d->text_blk_lpos, id);
}
if (r->text_buf_size && !r->text_buf)
@@ -1547,8 +1546,7 @@ bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb,
if (info->seq > 0)
desc_make_final(desc_ring, DESC_ID(id - 1));
- r->text_buf = data_alloc(rb, &rb->text_data_ring, r->text_buf_size,
- &d->text_blk_lpos, id);
+ r->text_buf = data_alloc(rb, r->text_buf_size, &d->text_blk_lpos, id);
/* If text data allocation fails, a data-less record is committed. */
if (r->text_buf_size && !r->text_buf) {
prb_commit(e);
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-30 07:54:42 +0000