On Mar 2, 2016 12:10 PM, "Chris Metcalf" <cmetc...@ezchip.com> wrote:
>
> In prepare_exit_to_usermode(), call task_isolation_ready()
> when we are checking the thread-info flags, and after we've handled
> the other work, call task_isolation_enter() unconditionally.
>
> In syscall_trace_enter_phase1(), we add the necessary support for
> strict-mode detection of syscalls.
>
> We add strict reporting for the kernel exception types that do
> not result in signals, namely non-signalling page faults and
> non-signalling MPX fixups.
>
> Signed-off-by: Chris Metcalf <cmetc...@ezchip.com>
> ---
> arch/x86/entry/common.c | 18 ++++++++++++++++--
> arch/x86/kernel/traps.c | 2 ++
> arch/x86/mm/fault.c | 2 ++
> 3 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
> index 03663740c866..27c71165416b 100644
> --- a/arch/x86/entry/common.c
> +++ b/arch/x86/entry/common.c
> @@ -21,6 +21,7 @@
> #include <linux/context_tracking.h>
> #include <linux/user-return-notifier.h>
> #include <linux/uprobes.h>
> +#include <linux/isolation.h>
>
> #include <asm/desc.h>
> #include <asm/traps.h>
> @@ -91,6 +92,10 @@ unsigned long syscall_trace_enter_phase1(struct pt_regs
> *regs, u32 arch)
> */
> if (work & _TIF_NOHZ) {
> enter_from_user_mode();
> + if (task_isolation_check_syscall(regs->orig_ax)) {
> + regs->orig_ax = -1;
> + return 0;
> + }
This needs a comment indicating the intended semantics.
And I've still heard no explanation of why this part can't use seccomp.
> work &= ~_TIF_NOHZ;
> }
> #endif
> @@ -254,17 +259,26 @@ static void exit_to_usermode_loop(struct pt_regs *regs,
> u32 cached_flags)
> if (cached_flags & _TIF_USER_RETURN_NOTIFY)
> fire_user_return_notifiers();
>
> + task_isolation_enter();
> +
> /* Disable IRQs and retry */
> local_irq_disable();
>
> cached_flags = READ_ONCE(pt_regs_to_thread_info(regs)->flags);
>
> - if (!(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
> + if (!(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS) &&
> + task_isolation_ready())
> break;
>
> }
> }
>
> +#ifdef CONFIG_TASK_ISOLATION
> +# define EXIT_TO_USERMODE_FLAGS (EXIT_TO_USERMODE_LOOP_FLAGS | _TIF_NOHZ)
> +#else
> +# define EXIT_TO_USERMODE_FLAGS EXIT_TO_USERMODE_LOOP_FLAGS
> +#endif
> +
TIF_NOHZ is already a hack and IMO this just makes it worse. At the
very least this should have a comment. It really ought to be either a
static_branch or a flag that's actually switched per cpu.
But this is also a confusing change. Don't override the definition
here -- stick it in the header where it belongs.
