linux-kernel - Re: [PATCH v15 06/13] arch/x86: enable task isolation functionality

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Date:   Tue, 30 Aug 2016 14:46:05 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Chris Metcalf <cmetcalf@...lanox.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Christoph Lameter <cl@...ux.com>,
        Gilad Ben Yossef <giladb@...lanox.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tejun Heo <tj@...nel.org>, Will Deacon <will.deacon@....com>,
        Rik van Riel <riel@...hat.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v15 06/13] arch/x86: enable task isolation functionality

On Aug 16, 2016 11:20 PM, "Chris Metcalf" <cmetcalf@...lanox.com> wrote:
>
> In exit_to_usermode_loop(), call task_isolation_ready() for
> TIF_TASK_ISOLATION tasks when we are checking the thread-info flags,
> and after we've handled the other work, call task_isolation_enter()
> for such tasks.
>
> In syscall_trace_enter_phase1(), we add the necessary support for
> reporting syscalls for task-isolation processes.
>
> 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.
>
> Tested-by: Christoph Lameter <cl@...ux.com>
> Signed-off-by: Chris Metcalf <cmetcalf@...lanox.com>
> ---
>  arch/x86/Kconfig                   |  1 +
>  arch/x86/entry/common.c            | 21 ++++++++++++++++++++-
>  arch/x86/include/asm/thread_info.h |  4 +++-
>  arch/x86/kernel/smp.c              |  2 ++
>  arch/x86/kernel/traps.c            |  3 +++
>  arch/x86/mm/fault.c                |  5 +++++
>  6 files changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index c580d8c33562..7f6ec46d18d0 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -90,6 +90,7 @@ config X86
>         select HAVE_ARCH_MMAP_RND_COMPAT_BITS   if MMU && COMPAT
>         select HAVE_ARCH_SECCOMP_FILTER
>         select HAVE_ARCH_SOFT_DIRTY             if X86_64
> +       select HAVE_ARCH_TASK_ISOLATION
>         select HAVE_ARCH_TRACEHOOK
>         select HAVE_ARCH_TRANSPARENT_HUGEPAGE
>         select HAVE_ARCH_WITHIN_STACK_FRAMES
> diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
> index 1433f6b4607d..3b23b3542909 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 +92,16 @@ static long syscall_trace_enter(struct pt_regs *regs)
>         if (emulated)
>                 return -1L;
>
> +       /*
> +        * In task isolation mode, we may prevent the syscall from
> +        * running, and if so we also deliver a signal to the process.
> +        */
> +       if (work & _TIF_TASK_ISOLATION) {
> +               if (task_isolation_syscall(regs->orig_ax) == -1)
> +                       return -1L;
> +               work &= ~_TIF_TASK_ISOLATION;
> +       }
> +

[apparently i failed to hit send earlier...]

Have you confirmed that this works correctly wrt PTRACE_SYSCALL?  It
should result in an even number of events (like raise(2) or an async
signal) and that should have a test case.

--Andy