x86: add a simple backtrace test module

During the work on the x86 32 and 64 bit backtrace code I found it useful
to have a simple test module to test a process and irq context backtrace.
Since the existing backtrace code was buggy, I figure it might be useful
to have such a test module in the kernel so that maybe we can even
detect such bugs earlier..

[ mingo@elte.hu: build fix ]

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 61 insertions, 0 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index 62015c3d8d91..8885627ea021 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_PM) += power/
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_KEXEC) += kexec.o
+obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
 obj-$(CONFIG_COMPAT) += compat.o
 obj-$(CONFIG_CGROUPS) += cgroup.o
 obj-$(CONFIG_CGROUP_DEBUG) += cgroup_debug.o
diff --git a/kernel/backtracetest.c b/kernel/backtracetest.c
new file mode 100644
index 000000000000..d1a7605c5b8f
--- /dev/null
+++ b/kernel/backtracetest.c
@@ -0,0 +1,48 @@
+/*
+ * Simple stack backtrace regression test module
+ *
+ * (C) Copyright 2008 Intel Corporation
+ * Author: Arjan van de Ven <arjan@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/delay.h>
+
+static struct timer_list backtrace_timer;
+
+static void backtrace_test_timer(unsigned long data)
+{
+        printk("Testing a backtrace from irq context.\n");
+        printk("The following trace is a kernel self test and not a bug!\n");
+        dump_stack();
+}
+static int backtrace_regression_test(void)
+{
+        printk("====[ backtrace testing ]===========\n");
+        printk("Testing a backtrace from process context.\n");
+        printk("The following trace is a kernel self test and not a bug!\n");
+        dump_stack();
+
+        init_timer(&backtrace_timer);
+        backtrace_timer.function = backtrace_test_timer;
+        mod_timer(&backtrace_timer, jiffies + 10);
+
+        msleep(10);
+        printk("====[ end of backtrace testing ]====\n");
+        return 0;
+}
+
+static void exitf(void)
+{
+}
+
+module_init(backtrace_regression_test);
+module_exit(exitf);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index f535b9b5eb00..aa56e631580d 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -506,6 +506,18 @@ config KPROBES_SANITY_TEST
 
           Say N if you are unsure.
 
+config BACKTRACE_SELF_TEST
+        tristate "Self test for the backtrace code"
+        depends on DEBUG_KERNEL
+        default n
+        help
+          This option provides a kernel module that can be used to test
+          the kernel stack backtrace code. This option is not useful
+          for distributions or general kernels, but only for kernel
+          developers working on architecture code.
+
+          Say N if you are unsure.
+
 config LKDTM
         tristate "Linux Kernel Dump Test Tool Module"
         depends on DEBUG_KERNEL