panic: add an option to replay all the printk message in buffer

Currently on panic, kernel will lower the loglevel and print out pending
printk msg only with console_flush_on_panic().

Add an option for users to configure the "panic_print" to replay all
dmesg in buffer, some of which they may have never seen due to the
loglevel setting, which will help panic debugging .

[feng.tang@intel.com: keep the original console_flush_on_panic() inside panic()]
Link: http://lkml.kernel.org/r/1556199137-14163-1-git-send-email-feng.tang@intel.com
[feng.tang@intel.com: use logbuf lock to protect the console log index]
Link: http://lkml.kernel.org/r/1556269868-22654-1-git-send-email-feng.tang@intel.com
Link: http://lkml.kernel.org/r/1556095872-36838-1-git-send-email-feng.tang@intel.com
Signed-off-by: Feng Tang <feng.tang@intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Aaro Koskinen <aaro.koskinen@nokia.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 52e6fbb..138f666 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3212,6 +3212,7 @@
                        bit 2: print timer info
                        bit 3: print locks info if CONFIG_LOCKDEP is on
                        bit 4: print ftrace buffer
+                       bit 5: print all printk messages in buffer
 
        panic_on_warn   panic() instead of WARN().  Useful to cause kdump
                        on a WARN().

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 665f294..83e59fd 100644 (file)
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -179,7 +179,7 @@ extern void panic_flush_kmsg_end(void)
        kmsg_dump(KMSG_DUMP_PANIC);
        bust_spinlocks(0);
        debug_locks_off();
-       console_flush_on_panic();
+       console_flush_on_panic(CONSOLE_FLUSH_PENDING);
 }
 
 static unsigned long oops_begin(struct pt_regs *regs)

diff --git a/include/linux/console.h b/include/linux/console.h
index ec9bdb3..d09951d 100644 (file)
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -166,6 +166,11 @@ struct console {
 extern int console_set_on_cmdline;
 extern struct console *early_console;
 
+enum con_flush_mode {
+       CONSOLE_FLUSH_PENDING,
+       CONSOLE_REPLAY_ALL,
+};
+
 extern int add_preferred_console(char *name, int idx, char *options);
 extern void register_console(struct console *);
 extern int unregister_console(struct console *);
@@ -175,7 +180,7 @@ extern int console_trylock(void);
 extern void console_unlock(void);
 extern void console_conditional_schedule(void);
 extern void console_unblank(void);
-extern void console_flush_on_panic(void);
+extern void console_flush_on_panic(enum con_flush_mode mode);
 extern struct tty_driver *console_device(int *);
 extern void console_stop(struct console *);
 extern void console_start(struct console *);

diff --git a/kernel/panic.c b/kernel/panic.c
index 8779d64..b4543a3 100644 (file)
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -51,6 +51,7 @@ EXPORT_SYMBOL_GPL(panic_timeout);
 #define PANIC_PRINT_TIMER_INFO         0x00000004
 #define PANIC_PRINT_LOCK_INFO          0x00000008
 #define PANIC_PRINT_FTRACE_INFO                0x00000010
+#define PANIC_PRINT_ALL_PRINTK_MSG     0x00000020
 unsigned long panic_print;
 
 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
@@ -134,6 +135,9 @@ EXPORT_SYMBOL(nmi_panic);
 
 static void panic_print_sys_info(void)
 {
+       if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG)
+               console_flush_on_panic(CONSOLE_REPLAY_ALL);
+
        if (panic_print & PANIC_PRINT_TASK_INFO)
                show_state();
 
@@ -277,7 +281,7 @@ void panic(const char *fmt, ...)
         * panic() is not being callled from OOPS.
         */
        debug_locks_off();
-       console_flush_on_panic();
+       console_flush_on_panic(CONSOLE_FLUSH_PENDING);
 
        panic_print_sys_info();
 

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 17102fd..a6e06fe 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2535,10 +2535,11 @@ void console_unblank(void)
 
 /**
  * console_flush_on_panic - flush console content on panic
+ * @mode: flush all messages in buffer or just the pending ones
  *
  * Immediately output all pending messages no matter what.
  */
-void console_flush_on_panic(void)
+void console_flush_on_panic(enum con_flush_mode mode)
 {
        /*
         * If someone else is holding the console lock, trylock will fail
@@ -2549,6 +2550,15 @@ void console_flush_on_panic(void)
         */
        console_trylock();
        console_may_schedule = 0;
+
+       if (mode == CONSOLE_REPLAY_ALL) {
+               unsigned long flags;
+
+               logbuf_lock_irqsave(flags);
+               console_seq = log_first_seq;
+               console_idx = log_first_idx;
+               logbuf_unlock_irqrestore(flags);
+       }
        console_unlock();
 }