From fb2ca533f518dabf814c6aab3b7ce3c236959a68 Mon Sep 17 00:00:00 2001 From: Jason Wessel Date: Fri, 10 Aug 2012 12:21:15 -0500 Subject: [PATCH] mips,kgdb: fix recursive page fault with CONFIG_KPROBES commit f0a996eeeda214f4293e234df33b29bec003b536 upstream. This fault was detected using the kgdb test suite on boot and it crashes recursively due to the fact that CONFIG_KPROBES on mips adds an extra die notifier in the page fault handler. The crash signature looks like this: kgdbts:RUN bad memory access test KGDB: re-enter exception: ALL breakpoints killed Call Trace: [<807b7548>] dump_stack+0x20/0x54 [<807b7548>] dump_stack+0x20/0x54 The fix for now is to have kgdb return immediately if the fault type is DIE_PAGE_FAULT and allow the kprobe code to decide what is supposed to happen. Signed-off-by: Jason Wessel Cc: Masami Hiramatsu Cc: David S. Miller Signed-off-by: Greg Kroah-Hartman --- arch/mips/kernel/kgdb.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/mips/kernel/kgdb.c b/arch/mips/kernel/kgdb.c index f4546e97c60d..23817a6e32b6 100644 --- a/arch/mips/kernel/kgdb.c +++ b/arch/mips/kernel/kgdb.c @@ -283,6 +283,15 @@ static int kgdb_mips_notify(struct notifier_block *self, unsigned long cmd, struct pt_regs *regs = args->regs; int trap = (regs->cp0_cause & 0x7c) >> 2; +#ifdef CONFIG_KPROBES + /* + * Return immediately if the kprobes fault notifier has set + * DIE_PAGE_FAULT. + */ + if (cmd == DIE_PAGE_FAULT) + return NOTIFY_DONE; +#endif /* CONFIG_KPROBES */ + /* Userspace events, ignore. */ if (user_mode(regs)) return NOTIFY_DONE; -- 2.39.5