Messages in this thread Patch in this message | | | Date | Mon, 20 Jul 2009 20:46:38 +0800 | From | Lai Jiangshan <> | Subject | [PATCH] sysrq, kdump: fix regression, revert "simplify sysrq-c handler" |
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1) This fix breaks our tools. This fix changes the ABI. panic_on_oops is default 0, and a lots system do not specify the boot option "panic", thus, Sysrq-c will not cause CrashDump(Kdump) as expected.
2) When CONFIG_KEXEC=n, Sysrq-c should become an invalid command like Sysrq-D(CONFIG_LOCKDEP, show-all-locks). But this fix makes it a valid command and let it do a hazard thing: cause a page fault(NULL dereference) in kernel.
So, we revert this fix.
|commit d6580a9f15238b87e618310c862231ae3f352d2d |Author: Neil Horman <nhorman@tuxdriver.com> |Date: Wed Jun 17 16:28:17 2009 -0700
| kexec: sysrq: simplify sysrq-c handler
| Currently the sysrq-c handler is bit over-engineered. Its behavior is | dependent on a few compile time and run time factors that alter its | behavior which is really unnecessecary.
| If CONFIG_KEXEC is not configured, sysrq-c, crashes the system with a NULL | pointer dereference. If CONFIG_KEXEC is configured, it calls crash_kexec | directly, which implies that the kexec kernel will either be booted (if | its been previously loaded), or it will simply do nothing (the no kexec | kernel has been loaded).
| It would be much easier to just simplify the whole thing to dereference a | NULL pointer all the time regardless of configuration. That way, it will | always try to crash the system, and if a kexec kernel has been loaded into | reserved space, it will still boot from the page fault trap handler | (assuming panic_on_oops is set appropriately).
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> --- diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c index 0db3585..39a05b5 100644 --- a/drivers/char/sysrq.c +++ b/drivers/char/sysrq.c @@ -121,17 +121,20 @@ static struct sysrq_key_op sysrq_unraw_op = { #define sysrq_unraw_op (*(struct sysrq_key_op *)0) #endif /* CONFIG_VT */ -static void sysrq_handle_crash(int key, struct tty_struct *tty) +#ifdef CONFIG_KEXEC +static void sysrq_handle_crashdump(int key, struct tty_struct *tty) { - char *killer = NULL; - *killer = 1; + crash_kexec(get_irq_regs()); } static struct sysrq_key_op sysrq_crashdump_op = { - .handler = sysrq_handle_crash, - .help_msg = "Crash", - .action_msg = "Trigger a crash", + .handler = sysrq_handle_crashdump, + .help_msg = "Crashdump", + .action_msg = "Trigger a crashdump", .enable_mask = SYSRQ_ENABLE_DUMP, }; +#else +#define sysrq_crashdump_op (*(struct sysrq_key_op *)0) +#endif static void sysrq_handle_reboot(int key, struct tty_struct *tty) {
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