On Fri, Nov 24, 2017 at 06:23:40PM +0100, Ingo Molnar wrote:
> From: Andy Lutomirski <[email protected]>
>
> When we start using an entry trampoline, a #GP from userspace will
> be delivered on the entry stack, not on the task stack. Fix the
> espfix64 #DF fixup to set up #GP according to TSS.SP0, rather than
> assuming that pt_regs + 1 == SP0. This won't change anything
> without an entry stack, but it will make the code continue to work
> when an entry stack is added.
>
> Signed-off-by: Andy Lutomirski <[email protected]>
> Signed-off-by: Thomas Gleixner <[email protected]>
> Reviewed-by: Thomas Gleixner <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: Brian Gerst <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Cc: Josh Poimboeuf <[email protected]>
> Cc: Linus Torvalds <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Link:
> https://lkml.kernel.org/r/b1ef4136616c6bd2a75d1fd2736d1d54437d65a8.1511497875.git.l...@kernel.org
> Signed-off-by: Ingo Molnar <[email protected]>
> ---
> arch/x86/kernel/traps.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index 2008dd0f8ccb..1bd43f044c62 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -359,7 +359,8 @@ dotraplinkage void do_double_fault(struct pt_regs *regs,
> long error_code)
> regs->cs == __KERNEL_CS &&
> regs->ip == (unsigned long)native_irq_return_iret)
> {
> - struct pt_regs *normal_regs = task_pt_regs(current);
> + struct pt_regs *normal_regs =
> + (struct pt_regs *)this_cpu_read(cpu_tss.x86_tss.sp0) -
> 1;
Just let that line stick out. Also, you can shorten it by renaming
normal_regs to something much shorter - it is a local variable and the
comment already explains everything you you can just as well have:
struct pt_regs *r = (struct pt_regs
*)this_cpu_read(cpu_tss.x86_tss.sp0) - 1;
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
