| From: Jason Wessel <jason.wessel@windriver.com> |
| Date: Fri, 10 Aug 2012 12:21:15 -0500 |
| Subject: 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. |
| |
| Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> |
| Cc: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Jason Wessel <jason.wessel@windriver.com> |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| arch/mips/kernel/kgdb.c | 9 +++++++++ |
| 1 file changed, 9 insertions(+) |
| |
| --- a/arch/mips/kernel/kgdb.c |
| +++ b/arch/mips/kernel/kgdb.c |
| @@ -283,6 +283,15 @@ static int kgdb_mips_notify(struct notif |
| 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; |
