diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
index d6bd50110ec2..2e7a1e032c71 100644
--- a/include/linux/kmsg_dump.h
+++ b/include/linux/kmsg_dump.h
@@ -55,12 +55,17 @@ struct kmsg_dumper {
#ifdef CONFIG_PRINTK
void kmsg_dump(enum kmsg_dump_reason reason);
+bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
+ char *line, size_t size, size_t *len);
+
bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
char *line, size_t size, size_t *len);
bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
char *buf, size_t size, size_t *len);
+void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper);
+
void kmsg_dump_rewind(struct kmsg_dumper *dumper);
int kmsg_dump_register(struct kmsg_dumper *dumper);
@@ -71,6 +76,13 @@ static inline void kmsg_dump(enum kmsg_dump_reason reason)
{
}
+static inline bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper,
+ bool syslog, const char *line,
+ size_t size, size_t *len)
+{
+ return false;
+}
+
static inline bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
const char *line, size_t size, size_t *len)
{
@@ -83,6 +95,10 @@ static inline bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
return false;
}
+static inline void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
+{
+}
+
static inline void kmsg_dump_rewind(struct kmsg_dumper *dumper)
{
}
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 67b847dfa2bb..1f91413edb87 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -14,6 +14,7 @@
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/kernel.h>
+#include <linux/kmsg_dump.h>
#include <linux/reboot.h>
#include <linux/sched.h>
#include <linux/sysrq.h>
@@ -2040,8 +2041,15 @@ static int kdb_env(int argc, const char **argv)
*/
static int kdb_dmesg(int argc, const char **argv)
{
- char *syslog_data[4], *start, *end, c = '\0', *p;
- int diag, logging, logsize, lines = 0, adjust = 0, n;
+ int diag;
+ int logging;
+ int lines = 0;
+ int adjust = 0;
+ int n = 0;
+ int skip = 0;
+ struct kmsg_dumper dumper = { .active = 1 };
+ size_t len;
+ char buf[201];
if (argc > 2)
return KDB_ARGCOUNT;
@@ -2064,22 +2072,10 @@ static int kdb_dmesg(int argc, const char **argv)
kdb_set(2, setargs);
}
- /* syslog_data[0,1] physical start, end+1. syslog_data[2,3]
- * logical start, end+1. */
- kdb_syslog_data(syslog_data);
- if (syslog_data[2] == syslog_data[3])
- return 0;
- logsize = syslog_data[1] - syslog_data[0];
- start = syslog_data[2];
- end = syslog_data[3];
-#define KDB_WRAP(p) (((p - syslog_data[0]) % logsize) + syslog_data[0])
- for (n = 0, p = start; p < end; ++p) {
- c = *KDB_WRAP(p);
- if (c == '\n')
- ++n;
- }
- if (c != '\n')
- ++n;
+ kmsg_dump_rewind_nolock(&dumper);
+ while (kmsg_dump_get_line_nolock(&dumper, 1, NULL, 0, NULL))
+ n++;
+
if (lines < 0) {
if (adjust >= n)
kdb_printf("buffer only contains %d lines, nothing "
@@ -2087,21 +2083,11 @@ static int kdb_dmesg(int argc, const char **argv)
else if (adjust - lines >= n)
kdb_printf("buffer only contains %d lines, last %d "
"lines printed\n", n, n - adjust);
- if (adjust) {
- for (; start < end && adjust; ++start) {
- if (*KDB_WRAP(start) == '\n')
- --adjust;
- }
- if (start < end)
- ++start;
- }
- for (p = start; p < end && lines; ++p) {
- if (*KDB_WRAP(p) == '\n')
- ++lines;
- }
- end = p;
+ skip = adjust;
+ lines = abs(lines);
} else if (lines > 0) {
- int skip = n - (adjust + lines);
+ skip = n - lines - adjust;
+ lines = abs(lines);
if (adjust >= n) {
kdb_printf("buffer only contains %d lines, "
"nothing printed\n", n);
@@ -2112,35 +2098,24 @@ static int kdb_dmesg(int argc, const char **argv)
kdb_printf("buffer only contains %d lines, first "
"%d lines printed\n", n, lines);
}
- for (; start < end && skip; ++start) {
- if (*KDB_WRAP(start) == '\n')
- --skip;
- }
- for (p = start; p < end && lines; ++p) {
- if (*KDB_WRAP(p) == '\n')
- --lines;
- }
- end = p;
+ } else {
+ lines = n;
}
- /* Do a line at a time (max 200 chars) to reduce protocol overhead */
- c = '\n';
- while (start != end) {
- char buf[201];
- p = buf;
- if (KDB_FLAG(CMD_INTERRUPT))
- return 0;
- while (start < end && (c = *KDB_WRAP(start)) &&
- (p - buf) < sizeof(buf)-1) {
- ++start;
- *p++ = c;
- if (c == '\n')
- break;
+
+ if (skip >= n || skip < 0)
+ return 0;
+
+ kmsg_dump_rewind_nolock(&dumper);
+ while (kmsg_dump_get_line_nolock(&dumper, 1, buf, sizeof(buf), &len)) {
+ if (skip) {
+ skip--;
+ continue;
}
- *p = '\0';
- kdb_printf("%s", buf);
+ if (!lines--)
+ break;
+
+ kdb_printf("%.*s\n", (int)len - 1, buf);
}
- if (c != '\n')
- kdb_printf("\n");
return 0;
}
diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
index 47c4e56e513b..392ec6a25844 100644
--- a/kernel/debug/kdb/kdb_private.h
+++ b/kernel/debug/kdb/kdb_private.h
@@ -205,7 +205,6 @@ extern char kdb_grep_string[];
extern int kdb_grep_leading;
extern int kdb_grep_trailing;
extern char *kdb_cmds[];
-extern void kdb_syslog_data(char *syslog_data[]);
extern unsigned long kdb_task_state_string(const char *);
extern char kdb_task_state_char (const struct task_struct *);
extern unsigned long kdb_task_state(const struct task_struct *p,
diff --git a/kernel/printk.c b/kernel/printk.c
index 177fa49357a5..ac4bc9e79465 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1192,21 +1192,6 @@ SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
}
-#ifdef CONFIG_KGDB_KDB
-/* kdb dmesg command needs access to the syslog buffer. do_syslog()
- * uses locks so it cannot be used during debugging. Just tell kdb
- * where the start and end of the physical and logical logs are. This
- * is equivalent to do_syslog(3).
- */
-void kdb_syslog_data(char *syslog_data[4])
-{
- syslog_data[0] = log_buf;
- syslog_data[1] = log_buf + log_buf_len;
- syslog_data[2] = log_buf + log_first_idx;
- syslog_data[3] = log_buf + log_next_idx;
-}
-#endif /* CONFIG_KGDB_KDB */
-
static bool __read_mostly ignore_loglevel;
static int __init ignore_loglevel_setup(char *str)
@@ -2524,6 +2509,57 @@ void kmsg_dump(enum kmsg_dump_reason reason)
rcu_read_unlock();
}
+/**
+ * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
+ * @dumper: registered kmsg dumper
+ * @syslog: include the "<4>" prefixes
+ * @line: buffer to copy the line to
+ * @size: maximum size of the buffer
+ * @len: length of line placed into buffer
+ *
+ * Start at the beginning of the kmsg buffer, with the oldest kmsg
+ * record, and copy one record into the provided buffer.
+ *
+ * Consecutive calls will return the next available record moving
+ * towards the end of the buffer with the youngest messages.
+ *
+ * A return value of FALSE indicates that there are no more records to
+ * read.
+ *
+ * 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,
+ char *line, size_t size, size_t *len)
+{
+ struct log *msg;
+ size_t l = 0;
+ bool ret = false;
+
+ if (!dumper->active)
+ goto out;
+
+ if (dumper->cur_seq < log_first_seq) {
+ /* messages are gone, move to first available one */
+ dumper->cur_seq = log_first_seq;
+ dumper->cur_idx = log_first_idx;
+ }
+
+ /* last entry */
+ if (dumper->cur_seq >= log_next_seq)
+ goto out;
+
+ msg = log_from_idx(dumper->cur_idx);
+ l = msg_print_text(msg, 0, syslog, line, size);
+
+ dumper->cur_idx = log_next(dumper->cur_idx);
+ dumper->cur_seq++;
+ ret = true;
+out:
+ if (len)
+ *len = l;
+ return ret;
+}
+
/**
* kmsg_dump_get_line - retrieve one kmsg log line
* @dumper: registered kmsg dumper
@@ -2545,36 +2581,12 @@ bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
char *line, size_t size, size_t *len)
{
unsigned long flags;
- struct log *msg;
- size_t l = 0;
- bool ret = false;
-
- if (!dumper->active)
- goto out;
+ bool ret;
raw_spin_lock_irqsave(&logbuf_lock, flags);
- if (dumper->cur_seq < log_first_seq) {
- /* messages are gone, move to first available one */
- dumper->cur_seq = log_first_seq;
- dumper->cur_idx = log_first_idx;
- }
-
- /* last entry */
- if (dumper->cur_seq >= log_next_seq) {
- raw_spin_unlock_irqrestore(&logbuf_lock, flags);
- goto out;
- }
-
- msg = log_from_idx(dumper->cur_idx);
- l = msg_print_text(msg, 0, syslog, line, size);
-
- dumper->cur_idx = log_next(dumper->cur_idx);
- dumper->cur_seq++;
- ret = true;
+ ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
-out:
- if (len)
- *len = l;
+
return ret;
}
EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
@@ -2678,6 +2690,24 @@ out:
}
EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
+/**
+ * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
+ * @dumper: registered kmsg dumper
+ *
+ * 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.
+ *
+ * The function is similar to kmsg_dump_rewind(), but grabs no locks.
+ */
+void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
+{
+ dumper->cur_seq = clear_seq;
+ dumper->cur_idx = clear_idx;
+ dumper->next_seq = log_next_seq;
+ dumper->next_idx = log_next_idx;
+}
+
/**
* kmsg_dump_rewind - reset the interator
* @dumper: registered kmsg dumper
@@ -2691,10 +2721,7 @@ void kmsg_dump_rewind(struct kmsg_dumper *dumper)
unsigned long flags;
raw_spin_lock_irqsave(&logbuf_lock, flags);
- dumper->cur_seq = clear_seq;
- dumper->cur_idx = clear_idx;
- dumper->next_seq = log_next_seq;
- dumper->next_idx = log_next_idx;
+ kmsg_dump_rewind_nolock(dumper);
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
}
EXPORT_SYMBOL_GPL(kmsg_dump_rewind);