3 files changed, 19 insertions, 2 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 033d4e69b43b..d99fd9c0ec0e 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2211,6 +2211,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
                         default: off.
 
+        printk.always_kmsg_dump=
+                        Trigger kmsg_dump for cases other than kernel oops or
+                        panics
+                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
+                        default: disabled
+
         printk.time=    Show timing data prefixed to each printk message line
                         Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
 
diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
index fee66317e071..35f7237ec972 100644
--- a/include/linux/kmsg_dump.h
+++ b/include/linux/kmsg_dump.h
@@ -15,13 +15,18 @@
 #include <linux/errno.h>
 #include <linux/list.h>
 
+/*
+ * Keep this list arranged in rough order of priority. Anything listed after
+ * KMSG_DUMP_OOPS will not be logged by default unless printk.always_kmsg_dump
+ * is passed to the kernel.
+ */
 enum kmsg_dump_reason {
-        KMSG_DUMP_OOPS,
         KMSG_DUMP_PANIC,
+        KMSG_DUMP_OOPS,
+        KMSG_DUMP_EMERG,
         KMSG_DUMP_RESTART,
         KMSG_DUMP_HALT,
         KMSG_DUMP_POWEROFF,
-        KMSG_DUMP_EMERG,
 };
 
 /**
diff --git a/kernel/printk.c b/kernel/printk.c
index 13c0a1143f49..32690a0b7a18 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -702,6 +702,9 @@ static bool printk_time = 0;
 #endif
 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 
+static bool always_kmsg_dump;
+module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
+
 /* Check if we have any console registered that can be called early in boot. */
 static int have_callable_console(void)
 {
@@ -1732,6 +1735,9 @@ void kmsg_dump(enum kmsg_dump_reason reason)
         unsigned long l1, l2;
         unsigned long flags;
 
+        if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
+                return;
+
         /* Theoretically, the log could move on after we do this, but
            there's not a lot we can do about that. The new messages
            will overwrite the start of what we dump. */