stacktrace: add saved stack traces to backtrace self-test

This patch adds saved stack-traces to the backtrace suite of self-tests.

Note that we don't depend on or unconditionally enable CONFIG_STACKTRACE
because not all architectures may have it (and we still want to enable the
other tests for those architectures).

Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 32 insertions, 1 deletions

diff --git a/kernel/backtracetest.c b/kernel/backtracetest.c
index d1a7605c5b8f..50f7abd0813d 100644
--- a/kernel/backtracetest.c
+++ b/kernel/backtracetest.c
@@ -10,9 +10,10 @@
  * of the License.
  */
 
+#include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/sched.h>
-#include <linux/delay.h>
+#include <linux/stacktrace.h>
 
 static struct timer_list backtrace_timer;
 
@@ -22,6 +23,31 @@ static void backtrace_test_timer(unsigned long data)
         printk("The following trace is a kernel self test and not a bug!\n");
         dump_stack();
 }
+
+#ifdef CONFIG_STACKTRACE
+static void backtrace_test_saved(void)
+{
+        struct stack_trace trace;
+        unsigned long entries[8];
+
+        printk("Testing a saved backtrace.\n");
+        printk("The following trace is a kernel self test and not a bug!\n");
+
+        trace.nr_entries = 0;
+        trace.max_entries = ARRAY_SIZE(entries);
+        trace.entries = entries;
+        trace.skip = 0;
+
+        save_stack_trace(&trace);
+        print_stack_trace(&trace, 0);
+}
+#else
+static void backtrace_test_saved(void)
+{
+        printk("Saved backtrace test skipped.\n");
+}
+#endif
+
 static int backtrace_regression_test(void)
 {
         printk("====[ backtrace testing ]===========\n");
@@ -29,6 +55,8 @@ static int backtrace_regression_test(void)
         printk("The following trace is a kernel self test and not a bug!\n");
         dump_stack();
 
+        backtrace_test_saved();
+
         init_timer(&backtrace_timer);
         backtrace_timer.function = backtrace_test_timer;
         mod_timer(&backtrace_timer, jiffies + 10);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9c17fb9d1d5e..6263e2d851f1 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -562,6 +562,9 @@ config BACKTRACE_SELF_TEST
           for distributions or general kernels, but only for kernel
           developers working on architecture code.
 
+          Note that if you want to also test saved backtraces, you will
+          have to enable STACKTRACE as well.
+
           Say N if you are unsure.
 
 config LKDTM