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    SubjectRe: [PATCH v4 10/29] x86/die: Don't try to recover from an OOPS on a non-default stack
    On Sun, Jun 26, 2016 at 02:55:32PM -0700, Andy Lutomirski wrote:
    > It's not going to work, because the scheduler will explode if we try
    > to schedule when running on an IST stack or similar.
    >
    > This will matter when we let kernel stack overflows (which are #DF)
    > call die().
    >
    > Signed-off-by: Andy Lutomirski <luto@kernel.org>
    > ---
    > arch/x86/kernel/dumpstack.c | 3 +++
    > 1 file changed, 3 insertions(+)
    >
    > diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
    > index ef8017ca5ba9..352f022cfd5b 100644
    > --- a/arch/x86/kernel/dumpstack.c
    > +++ b/arch/x86/kernel/dumpstack.c
    > @@ -245,6 +245,9 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
    > return;
    > if (in_interrupt())
    > panic("Fatal exception in interrupt");
    > + if (((current_stack_pointer() ^ (current_top_of_stack() - 1))
    > + & ~(THREAD_SIZE - 1)) != 0)

    Ugh, that's hard to parse. You could remove the "!= 0" at least to
    shorten it a bit and have one less braces level.

    Or maybe even do something like that to make it a bit more readable:

    if ((current_stack_pointer() ^ (current_top_of_stack() - 1))
    &
    ~(THREAD_SIZE - 1))
    panic("Fatal exception on non-default stack");

    Meh.

    > + panic("Fatal exception on special stack");

    "Fatal exception on non-default stack"

    maybe?

    --
    Regards/Gruss,
    Boris.

    ECO tip #101: Trim your mails when you reply.

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