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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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