+ notify-page-fault-call-chain-for-i386.patch added to -mm tree

[akpm@xxxxxxxx]

The patch titled

     Notify page fault call chain for i386

has been added to the -mm tree.  Its filename is

     notify-page-fault-call-chain-for-i386.patch

See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this


From: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>

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@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---

 arch/i386/mm/fault.c      |   38 ++++++++++++++++++++++++++++++++++--
 include/asm-i386/kdebug.h |    2 +
 2 files changed, 38 insertions(+), 2 deletions(-)

diff -puN arch/i386/mm/fault.c~notify-page-fault-call-chain-for-i386 arch/i386/mm/fault.c
--- devel/arch/i386/mm/fault.c~notify-page-fault-call-chain-for-i386	2006-04-20 23:29:59.000000000 -0700
+++ devel-akpm/arch/i386/mm/fault.c	2006-04-20 23:29:59.000000000 -0700
@@ -30,6 +30,40 @@
 
 extern void die(const char *,struct pt_regs *,long);
 
+#ifdef CONFIG_KPROBES
+ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);
+int register_page_fault_notifier(struct notifier_block *nb)
+{
+	vmalloc_sync_all();
+	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);
+}
+
+static inline int notify_page_fault(enum die_val val, const 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);
+}
+#else
+static inline int notify_page_fault(enum die_val val, const char *str,
+			struct pt_regs *regs, long err, int trap, int sig)
+{
+	return NOTIFY_DONE;
+}
+#endif
+
+
 /*
  * Unlock any spinlocks which will prevent us from getting the
  * message out 
@@ -321,7 +355,7 @@ fastcall void __kprobes do_page_fault(st
 	if (unlikely(address >= TASK_SIZE)) {
 		if (!(error_code & 0x0000000d) && vmalloc_fault(address) >= 0)
 			return;
-		if (notify_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
+		if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
 						SIGSEGV) == NOTIFY_STOP)
 			return;
 		/*
@@ -331,7 +365,7 @@ fastcall void __kprobes do_page_fault(st
 		goto bad_area_nosemaphore;
 	}
 
-	if (notify_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
+	if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
 					SIGSEGV) == NOTIFY_STOP)
 		return;
 
diff -puN include/asm-i386/kdebug.h~notify-page-fault-call-chain-for-i386 include/asm-i386/kdebug.h
--- devel/include/asm-i386/kdebug.h~notify-page-fault-call-chain-for-i386	2006-04-20 23:29:59.000000000 -0700
+++ devel-akpm/include/asm-i386/kdebug.h	2006-04-20 23:29:59.000000000 -0700
@@ -19,6 +19,8 @@ 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 i386die_chain;
 
 
_

Patches currently in -mm which might be from anil.s.keshavamurthy@xxxxxxxxx are

notify-page-fault-call-chain-for-x86_64.patch
notify-page-fault-call-chain-for-i386.patch
notify-page-fault-call-chain-for-ia64.patch
notify-page-fault-call-chain-for-powerpc.patch
notify-page-fault-call-chain-for-sparc64.patch
kprobes-registers-for-notify-page-fault.patch
notify-page-fault-call-chain.patch

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