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    Subject[tip:x86/asm] context_tracking: Add ct_state() and CT_WARN_ON()
    Commit-ID:  f9281648ecd5081803bb2da84b9ccb0cf48436cd
    Gitweb: http://git.kernel.org/tip/f9281648ecd5081803bb2da84b9ccb0cf48436cd
    Author: Andy Lutomirski <luto@kernel.org>
    AuthorDate: Fri, 3 Jul 2015 12:44:21 -0700
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Tue, 7 Jul 2015 10:59:04 +0200

    context_tracking: Add ct_state() and CT_WARN_ON()

    This will let us sprinkle sanity checks around the kernel
    without making too much of a mess.

    Signed-off-by: Andy Lutomirski <luto@kernel.org>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: Denys Vlasenko <vda.linux@googlemail.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: paulmck@linux.vnet.ibm.com
    Link: http://lkml.kernel.org/r/5da41fb2ceb29eac671f427c67040401ba2a1fa0.1435952415.git.luto@kernel.org
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    include/linux/context_tracking.h | 15 +++++++++++++++
    include/linux/context_tracking_state.h | 1 +
    2 files changed, 16 insertions(+)

    diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
    index b96bd29..008fc67 100644
    --- a/include/linux/context_tracking.h
    +++ b/include/linux/context_tracking.h
    @@ -49,13 +49,28 @@ static inline void exception_exit(enum ctx_state prev_ctx)
    }
    }

    +
    +/**
    + * ct_state() - return the current context tracking state if known
    + *
    + * Returns the current cpu's context tracking state if context tracking
    + * is enabled. If context tracking is disabled, returns
    + * CONTEXT_DISABLED. This should be used primarily for debugging.
    + */
    +static inline enum ctx_state ct_state(void)
    +{
    + return context_tracking_is_enabled() ?
    + this_cpu_read(context_tracking.state) : CONTEXT_DISABLED;
    +}
    #else
    static inline void user_enter(void) { }
    static inline void user_exit(void) { }
    static inline enum ctx_state exception_enter(void) { return 0; }
    static inline void exception_exit(enum ctx_state prev_ctx) { }
    +static inline enum ctx_state ct_state(void) { return CONTEXT_DISABLED; }
    #endif /* !CONFIG_CONTEXT_TRACKING */

    +#define CT_WARN_ON(cond) WARN_ON(context_tracking_is_enabled() && (cond))

    #ifdef CONFIG_CONTEXT_TRACKING_FORCE
    extern void context_tracking_init(void);
    diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
    index 678ecdf..ee956c5 100644
    --- a/include/linux/context_tracking_state.h
    +++ b/include/linux/context_tracking_state.h
    @@ -14,6 +14,7 @@ struct context_tracking {
    bool active;
    int recursion;
    enum ctx_state {
    + CONTEXT_DISABLED = -1, /* returned by ct_state() if unknown */
    CONTEXT_KERNEL = 0,
    CONTEXT_USER,
    CONTEXT_GUEST,

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