debug: add end-of-oops marker
Right now it's nearly impossible for parsers that collect kernel crashes
from logs or emails (such as www.kerneloops.org) to detect the
end-of-oops condition. In addition, it's not currently possible to
detect whether or not 2 oopses that look alike are actually the same
oops reported twice, or are truly two unique oopses.
This patch adds an end-of-oops marker, and makes the end marker include
a very simple 64-bit random ID to be able to detect duplicate reports.
Normally, this ID is calculated as a late_initcall() (in the hope that
at that time there is enough entropy to get a unique enough ID); however
for early oopses the oops_exit() function needs to generate the ID on
the fly.
We do this all at the _end_ of an oops printout, so this does not impact
our ability to get the most important portions of a crash out to the
console first.
[ Sidenote: the already existing oopses-since-bootup counter we print
during crashes serves as the differentiator between multiple oopses
that trigger during the same bootup. ]
Tested on 32-bit and 64-bit x86. Artificially injected very early
crashes as well, as expected they result in this constant ID after
multiple bootups:
---[ end trace ca143223eefdc828 ]---
---[ end trace ca143223eefdc828 ]---
because the random pools are still all zero. But it all still works
fine and causes no additional problems (which is the main goal of
instrumentation code).
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/panic.c b/kernel/panic.c
index 6f6e03e..da4d6ba 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -19,6 +19,7 @@
#include <linux/nmi.h>
#include <linux/kexec.h>
#include <linux/debug_locks.h>
+#include <linux/random.h>
int panic_on_oops;
int tainted;
@@ -266,12 +267,29 @@
}
/*
+ * 64-bit random ID for oopses:
+ */
+static u64 oops_id;
+
+static int init_oops_id(void)
+{
+ if (!oops_id)
+ get_random_bytes(&oops_id, sizeof(oops_id));
+
+ return 0;
+}
+late_initcall(init_oops_id);
+
+/*
* Called when the architecture exits its oops handler, after printing
* everything.
*/
void oops_exit(void)
{
do_oops_enter_exit();
+ init_oops_id();
+ printk(KERN_WARNING "---[ end trace %016llx ]---\n",
+ (unsigned long long)oops_id);
}
#ifdef CONFIG_CC_STACKPROTECTOR
