1 files changed, 25 insertions, 1 deletions

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 2ce8826f1053..0c9f02506169 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -48,6 +48,7 @@
 #include <linux/uio.h>
 
 #include <asm/uaccess.h>
+#include <asm-generic/sections.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/printk.h>
@@ -2658,13 +2659,36 @@ int unregister_console(struct console *console)
 }
 EXPORT_SYMBOL(unregister_console);
 
+/*
+ * Some boot consoles access data that is in the init section and which will
+ * be discarded after the initcalls have been run. To make sure that no code
+ * will access this data, unregister the boot consoles in a late initcall.
+ *
+ * If for some reason, such as deferred probe or the driver being a loadable
+ * module, the real console hasn't registered yet at this point, there will
+ * be a brief interval in which no messages are logged to the console, which
+ * makes it difficult to diagnose problems that occur during this time.
+ *
+ * To mitigate this problem somewhat, only unregister consoles whose memory
+ * intersects with the init section. Note that code exists elsewhere to get
+ * rid of the boot console as soon as the proper console shows up, so there
+ * won't be side-effects from postponing the removal.
+ */
 static int __init printk_late_init(void)
 {
         struct console *con;
 
         for_each_console(con) {
                 if (!keep_bootcon && con->flags & CON_BOOT) {
-                        unregister_console(con);
+                        /*
+                         * Make sure to unregister boot consoles whose data
+                         * resides in the init section before the init section
+                         * is discarded. Boot consoles whose data will stick
+                         * around will automatically be unregistered when the
+                         * proper console replaces them.
+                         */
+                        if (init_section_intersects(con, sizeof(*con)))
+                                unregister_console(con);
                 }
         }
         hotcpu_notifier(console_cpu_notify, 0);