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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>
This commit is contained in:
Arjan van de Ven 2007-12-20 15:01:17 +01:00 committed by Ingo Molnar
parent 67e2be0232
commit 2c3b20e91f
1 changed files with 18 additions and 0 deletions
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18
kernel/panic.c
View File

@ -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;
@ -265,6 +266,20 @@ void oops_enter(void)
do_oops_enter_exit();
}
/*
* 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.
@ -272,6 +287,9 @@ void oops_enter(void)
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