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printk: introduce a kmsg_dump iterator

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Rather than storing the iterator information in the registered
kmsg_dumper structure, create a separate iterator structure. The
kmsg_dump_iter structure can reside on the stack of the caller, thus
allowing lockless use of the kmsg_dump functions.

Update code that accesses the kernel logs using the kmsg_dumper
structure to use the new kmsg_dump_iter structure. For kmsg_dumpers,
this also means adding a call to kmsg_dump_rewind() to initialize
the iterator.

All this is in preparation for removal of @logbuf_lock.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org> # pstore
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-13-john.ogness@linutronix.de
This commit is contained in:
John Ogness
2021-03-03 11:15:25 +01:00
committed by Petr Mladek
parent 5f6c7648e5
commit f9f3f02db9
9 changed files with 80 additions and 62 deletions
Download Patch File Download Diff File Expand all files Collapse all files

63
kernel/printk/printk.c
View File

@@ -3390,7 +3390,6 @@ EXPORT_SYMBOL_GPL(kmsg_dump_reason_str);
void kmsg_dump(enum kmsg_dump_reason reason)
{
struct kmsg_dumper *dumper;
unsigned long flags;
rcu_read_lock();
list_for_each_entry_rcu(dumper, &dump_list, list) {
@@ -3407,12 +3406,6 @@ void kmsg_dump(enum kmsg_dump_reason reason)
if (reason > max_reason)
continue;
/* initialize iterator with data about the stored records */
logbuf_lock_irqsave(flags);
dumper->cur_seq = latched_seq_read_nolock(&clear_seq);
dumper->next_seq = prb_next_seq(prb);
logbuf_unlock_irqrestore(flags);
/* invoke dumper which will iterate over records */
dumper->dump(dumper, reason);
}
@@ -3421,7 +3414,7 @@ void kmsg_dump(enum kmsg_dump_reason reason)
/**
* kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
* @dumper: registered kmsg dumper
* @iter: kmsg dump iterator
* @syslog: include the "<4>" prefixes
* @line: buffer to copy the line to
* @size: maximum size of the buffer
@@ -3438,24 +3431,28 @@ void kmsg_dump(enum kmsg_dump_reason reason)
*
* The function is similar to kmsg_dump_get_line(), but grabs no locks.
*/
bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter, bool syslog,
char *line, size_t size, size_t *len)
{
u64 min_seq = latched_seq_read_nolock(&clear_seq);
struct printk_info info;
unsigned int line_count;
struct printk_record r;
size_t l = 0;
bool ret = false;
if (iter->cur_seq < min_seq)
iter->cur_seq = min_seq;
prb_rec_init_rd(&r, &info, line, size);
/* Read text or count text lines? */
if (line) {
if (!prb_read_valid(prb, dumper->cur_seq, &r))
if (!prb_read_valid(prb, iter->cur_seq, &r))
goto out;
l = record_print_text(&r, syslog, printk_time);
} else {
if (!prb_read_valid_info(prb, dumper->cur_seq,
if (!prb_read_valid_info(prb, iter->cur_seq,
&info, &line_count)) {
goto out;
}
@@ -3464,7 +3461,7 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
}
dumper->cur_seq = r.info->seq + 1;
iter->cur_seq = r.info->seq + 1;
ret = true;
out:
if (len)
@@ -3474,7 +3471,7 @@ out:
/**
* kmsg_dump_get_line - retrieve one kmsg log line
* @dumper: registered kmsg dumper
* @iter: kmsg dump iterator
* @syslog: include the "<4>" prefixes
* @line: buffer to copy the line to
* @size: maximum size of the buffer
@@ -3489,14 +3486,14 @@ out:
* A return value of FALSE indicates that there are no more records to
* read.
*/
bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
char *line, size_t size, size_t *len)
{
unsigned long flags;
bool ret;
logbuf_lock_irqsave(flags);
ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
ret = kmsg_dump_get_line_nolock(iter, syslog, line, size, len);
logbuf_unlock_irqrestore(flags);
return ret;
@@ -3505,7 +3502,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
/**
* kmsg_dump_get_buffer - copy kmsg log lines
* @dumper: registered kmsg dumper
* @iter: kmsg dump iterator
* @syslog: include the "<4>" prefixes
* @buf: buffer to copy the line to
* @size: maximum size of the buffer
@@ -3522,9 +3519,10 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
* A return value of FALSE indicates that there are no more records to
* read.
*/
bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
char *buf, size_t size, size_t *len_out)
{
u64 min_seq = latched_seq_read_nolock(&clear_seq);
struct printk_info info;
struct printk_record r;
unsigned long flags;
@@ -3537,16 +3535,19 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
if (!buf || !size)
goto out;
if (iter->cur_seq < min_seq)
iter->cur_seq = min_seq;
logbuf_lock_irqsave(flags);
if (prb_read_valid_info(prb, dumper->cur_seq, &info, NULL)) {
if (info.seq != dumper->cur_seq) {
if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) {
if (info.seq != iter->cur_seq) {
/* messages are gone, move to first available one */
dumper->cur_seq = info.seq;
iter->cur_seq = info.seq;
}
}
/* last entry */
if (dumper->cur_seq >= dumper->next_seq) {
if (iter->cur_seq >= iter->next_seq) {
logbuf_unlock_irqrestore(flags);
goto out;
}
@@ -3557,7 +3558,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
* because this function (by way of record_print_text()) will
* not write more than size-1 bytes of text into @buf.
*/
seq = find_first_fitting_seq(dumper->cur_seq, dumper->next_seq,
seq = find_first_fitting_seq(iter->cur_seq, iter->next_seq,
size - 1, syslog, time);
/*
@@ -3570,7 +3571,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
len = 0;
prb_for_each_record(seq, prb, seq, &r) {
if (r.info->seq >= dumper->next_seq)
if (r.info->seq >= iter->next_seq)
break;
len += record_print_text(&r, syslog, time);
@@ -3579,7 +3580,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
prb_rec_init_rd(&r, &info, buf + len, size - len);
}
dumper->next_seq = next_seq;
iter->next_seq = next_seq;
ret = true;
logbuf_unlock_irqrestore(flags);
out:
@@ -3591,7 +3592,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
/**
* kmsg_dump_rewind_nolock - reset the iterator (unlocked version)
* @dumper: registered kmsg dumper
* @iter: kmsg dump iterator
*
* Reset the dumper's iterator so that kmsg_dump_get_line() and
* kmsg_dump_get_buffer() can be called again and used multiple
@@ -3599,26 +3600,26 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
*
* The function is similar to kmsg_dump_rewind(), but grabs no locks.
*/
void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter)
{
dumper->cur_seq = latched_seq_read_nolock(&clear_seq);
dumper->next_seq = prb_next_seq(prb);
iter->cur_seq = latched_seq_read_nolock(&clear_seq);
iter->next_seq = prb_next_seq(prb);
}
/**
* kmsg_dump_rewind - reset the iterator
* @dumper: registered kmsg dumper
* @iter: kmsg dump iterator
*
* Reset the dumper's iterator so that kmsg_dump_get_line() and
* kmsg_dump_get_buffer() can be called again and used multiple
* times within the same dumper.dump() callback.
*/
void kmsg_dump_rewind(struct kmsg_dumper *dumper)
void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
{
unsigned long flags;
logbuf_lock_irqsave(flags);
kmsg_dump_rewind_nolock(dumper);
kmsg_dump_rewind_nolock(iter);
logbuf_unlock_irqrestore(flags);
}
EXPORT_SYMBOL_GPL(kmsg_dump_rewind);