panic: add options to print system info when panic happens

Kernel panic issues are always painful to debug, partially because it's
not easy to get enough information of the context when panic happens.

And we have ramoops and kdump for that, while this commit tries to
provide a easier way to show the system info by adding a cmdline
parameter, referring some idea from sysrq handler.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Feng Tang <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Acked-by: Steven Rostedt (VMware) <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Documentation/admin-guide/kernel-parameters.txt

@@ -3092,6 +3092,14 @@
 			timeout < 0: reboot immediately
 			Format: <timeout>
 
+	panic_print=	Bitmask for printing system info when panic happens.
+			User can chose combination of the following bits:
+			bit 0: print all tasks info
+			bit 1: print system memory info
+			bit 2: print timer info
+			bit 3: print locks info if CONFIG_LOCKDEP is on
+			bit 4: print ftrace buffer
+
 	panic_on_warn	panic() instead of WARN().  Useful to cause kdump
 			on a WARN().
 

kernel/panic.c

@@ -46,6 +46,13 @@ int panic_on_warn __read_mostly;
 int panic_timeout = CONFIG_PANIC_TIMEOUT;
 EXPORT_SYMBOL_GPL(panic_timeout);
 
+#define PANIC_PRINT_TASK_INFO		0x00000001
+#define PANIC_PRINT_MEM_INFO		0x00000002
+#define PANIC_PRINT_TIMER_INFO		0x00000004
+#define PANIC_PRINT_LOCK_INFO		0x00000008
+#define PANIC_PRINT_FTRACE_INFO		0x00000010
+static unsigned long panic_print;
+
 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
 
 EXPORT_SYMBOL(panic_notifier_list);
@@ -125,6 +132,24 @@ void nmi_panic(struct pt_regs *regs, const char *msg)
 }
 EXPORT_SYMBOL(nmi_panic);
 
+static void panic_print_sys_info(void)
+{
+	if (panic_print & PANIC_PRINT_TASK_INFO)
+		show_state();
+
+	if (panic_print & PANIC_PRINT_MEM_INFO)
+		show_mem(0, NULL);
+
+	if (panic_print & PANIC_PRINT_TIMER_INFO)
+		sysrq_timer_list_show();
+
+	if (panic_print & PANIC_PRINT_LOCK_INFO)
+		debug_show_all_locks();
+
+	if (panic_print & PANIC_PRINT_FTRACE_INFO)
+		ftrace_dump(DUMP_ALL);
+}
+
 /**
  *	panic - halt the system
  *	@fmt: The text string to print
@@ -254,6 +279,8 @@ void panic(const char *fmt, ...)
 	debug_locks_off();
 	console_flush_on_panic();
 
+	panic_print_sys_info();
+
 	if (!panic_blink)
 		panic_blink = no_blink;
 
@@ -658,6 +685,7 @@ void refcount_error_report(struct pt_regs *regs, const char *err)
 #endif
 
 core_param(panic, panic_timeout, int, 0644);
+core_param(panic_print, panic_print, ulong, 0644);
 core_param(pause_on_oops, pause_on_oops, int, 0644);
 core_param(panic_on_warn, panic_on_warn, int, 0644);
 core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);