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Merge tag 'printk-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

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Pull printk updates from Petr Mladek:

 - Finally allow parallel writes and reads into/from the lockless
   ringbuffer. But it is not a complete solution. Readers are still
   serialized against each other. And nested writes are still prevented
   by printk_safe per-CPU buffers.

 - Use ttynull as the ultimate fallback for /dev/console.

 - Officially allow disabling console output by using console="" or
   console=null

 - A few code cleanups

* tag 'printk-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk: remove logbuf_lock writer-protection of ringbuffer
  printk: inline log_output(),log_store() in vprintk_store()
  printk: remove obsolete dead assignment
  printk/console: Allow to disable console output by using console="" or console=null
  init/console: Use ttynull as a fallback when there is no console
  printk: ringbuffer: Reference text_data_ring directly in callees.
This commit is contained in:
Linus Torvalds
2020-12-16 10:45:11 -08:00
parent 5e60366d56 5ed37174e6
commit d3eb52113d
7 changed files with 202 additions and 139 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/printk/printk.c
+157 -104
View File
@@ -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",
@@ -1907,75 +1860,117 @@ 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--;
lflags |= LOG_NEWLINE;
}
/*
* 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);
/* strip kernel syslog prefix and extract log level or control flags */
if (facility == 0) {
int kern_level;
if (reserve_size > LOG_LINE_MAX)
reserve_size = LOG_LINE_MAX;
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;
}
text_len -= 2;
text += 2;
}
}
/* Extract log level or control flags. */
if (facility == 0)
parse_prefix(&prefix_buf[0], &level, &lflags);
if (level == LOGLEVEL_DEFAULT)
level = default_message_loglevel;
@@ -1983,7 +1978,59 @@ int vprintk_store(int facility, int level,
if (dev_info)
lflags |= LOG_NEWLINE;
return log_output(facility, level, lflags, dev_info, text, text_len);
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;
if (lflags & LOG_NEWLINE) {
r.info->flags |= LOG_NEWLINE;
prb_final_commit(&e);
} else {
prb_commit(&e);
}
return text_len;
}
}
/*
* 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)
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 (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;
kernel/printk/printk_ringbuffer.c
+15 -17
View File
@@ -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);