| Date | Sun, 28 Oct 2012 23:16:18 +0000 | From | Ben Hutchings <> | Subject | [ 042/105] mips,kgdb: fix recursive page fault with CONFIG_KPROBES |
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3.2-stable review patch. If anyone has any objections, please let me know.
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From: Jason Wessel <jason.wessel@windriver.com>
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;
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