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    Subject[(resend)patch 4/7] Notify page fault call chain for powerpc
    Overloading of page fault notification with the
    notify_die() has performance issues(since the
    only interested components for page fault is
    kprobes and/or kdb) and hence this patch introduces
    the new notifier call chain exclusively for page
    fault notifications their by avoiding notifying
    unnecessary components in the do_page_fault() code
    path.

    Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>

    ---
    arch/powerpc/kernel/traps.c | 11 +++++++++++
    arch/powerpc/mm/fault.c | 2 +-
    include/asm-powerpc/kdebug.h | 9 +++++++++
    3 files changed, 21 insertions(+), 1 deletion(-)

    Index: linux-2.6.17-rc1-mm3/arch/powerpc/kernel/traps.c
    ===================================================================
    --- linux-2.6.17-rc1-mm3.orig/arch/powerpc/kernel/traps.c
    +++ linux-2.6.17-rc1-mm3/arch/powerpc/kernel/traps.c
    @@ -75,6 +75,7 @@ EXPORT_SYMBOL(__debugger_fault_handler);
    #endif

    ATOMIC_NOTIFIER_HEAD(powerpc_die_chain);
    +ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);

    int register_die_notifier(struct notifier_block *nb)
    {
    @@ -88,6 +89,16 @@ int unregister_die_notifier(struct notif
    }
    EXPORT_SYMBOL(unregister_die_notifier);

    +int register_page_fault_notifier(struct notifier_block *nb)
    +{
    + return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
    +}
    +
    +int unregister_page_fault_notifier(struct notifier_block *nb)
    +{
    + return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
    +}
    +
    /*
    * Trap & Exception support
    */
    Index: linux-2.6.17-rc1-mm3/arch/powerpc/mm/fault.c
    ===================================================================
    --- linux-2.6.17-rc1-mm3.orig/arch/powerpc/mm/fault.c
    +++ linux-2.6.17-rc1-mm3/arch/powerpc/mm/fault.c
    @@ -142,7 +142,7 @@ int __kprobes do_page_fault(struct pt_re
    is_write = error_code & ESR_DST;
    #endif /* CONFIG_4xx || CONFIG_BOOKE */

    - if (notify_die(DIE_PAGE_FAULT, "page_fault", regs, error_code,
    + if (notify_page_fault(DIE_PAGE_FAULT, "page_fault", regs, error_code,
    11, SIGSEGV) == NOTIFY_STOP)
    return 0;

    Index: linux-2.6.17-rc1-mm3/include/asm-powerpc/kdebug.h
    ===================================================================
    --- linux-2.6.17-rc1-mm3.orig/include/asm-powerpc/kdebug.h
    +++ linux-2.6.17-rc1-mm3/include/asm-powerpc/kdebug.h
    @@ -18,7 +18,10 @@ struct die_args {

    extern int register_die_notifier(struct notifier_block *);
    extern int unregister_die_notifier(struct notifier_block *);
    +extern int register_page_fault_notifier(struct notifier_block *);
    +extern int unregister_page_fault_notifier(struct notifier_block *);
    extern struct atomic_notifier_head powerpc_die_chain;
    +extern struct atomic_notifier_head notify_page_fault_chain;

    /* Grossly misnamed. */
    enum die_val {
    @@ -36,5 +39,11 @@ static inline int notify_die(enum die_va
    return atomic_notifier_call_chain(&powerpc_die_chain, val, &args);
    }

    +static inline int notify_page_fault(enum die_val val,char *str,struct pt_regs *regs,long err,int trap, int sig)
    +{
    + struct die_args args = { .regs=regs, .str=str, .err=err, .trapnr=trap,.signr=sig };
    + return atomic_notifier_call_chain(&notify_page_fault_chain, val, &args);
    +}
    +
    #endif /* __KERNEL__ */
    #endif /* _ASM_POWERPC_KDEBUG_H */
    --
    -
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