1 files changed, 25 insertions, 0 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 75077ad0b537..444b770c9595 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -33,6 +33,7 @@
 #include <linux/bootmem.h>
 #include <linux/syscalls.h>
 #include <linux/kexec.h>
+#include <linux/kdb.h>
 #include <linux/ratelimit.h>
 #include <linux/kmsg_dump.h>
 #include <linux/syslog.h>
@@ -413,6 +414,22 @@ 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_end -
+                (logged_chars < log_buf_len ? logged_chars : log_buf_len);
+        syslog_data[3] = log_buf + log_end;
+}
+#endif  /* CONFIG_KGDB_KDB */
+
 /*
  * Call the console drivers on a range of log_buf
  */
@@ -586,6 +603,14 @@ asmlinkage int printk(const char *fmt, ...)
         va_list args;
         int r;
 
+#ifdef CONFIG_KGDB_KDB
+        if (unlikely(kdb_trap_printk)) {
+                va_start(args, fmt);
+                r = vkdb_printf(fmt, args);
+                va_end(args);
+                return r;
+        }
+#endif
         va_start(args, fmt);
         r = vprintk(fmt, args);
         va_end(args);