x86: optimize page faults like all other achitectures and kill notifier cruft

x86(-64) are the last architectures still using the page fault notifier
cruft for the kprobes page fault hook.  This patch converts them to the
proper direct calls, and removes the now unused pagefault notifier bits
aswell as the cruft in kprobes.c that was related to this mess.

I know Andi didn't really like this, but all other architecture maintainers
agreed the direct calls are much better and besides the obvious cruft
removal a common way of dealing with kprobes across architectures is
important aswell.

[akpm@linux-foundation.org: build fix]
[akpm@linux-foundation.org: fix sparc64]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Andi Kleen <ak@suse.de>
Cc: <linux-arch@vger.kernel.org>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 38 insertions, 49 deletions

diff --git a/arch/x86/mm/fault_32.c b/arch/x86/mm/fault_32.c
index fcb38e7f354..be72c2a5b03 100644
--- a/arch/x86/mm/fault_32.c
+++ b/arch/x86/mm/fault_32.c
@@ -25,6 +25,7 @@
 #include <linux/kprobes.h>
 #include <linux/uaccess.h>
 #include <linux/kdebug.h>
+#include <linux/kprobes.h>
 
 #include <asm/system.h>
 #include <asm/desc.h>
@@ -32,33 +33,27 @@
 
 extern void die(const char *,struct pt_regs *,long);
 
-static ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);
-
-int register_page_fault_notifier(struct notifier_block *nb)
+#ifdef CONFIG_KPROBES
+static inline int notify_page_fault(struct pt_regs *regs)
 {
-	vmalloc_sync_all();
-	return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
-}
-EXPORT_SYMBOL_GPL(register_page_fault_notifier);
+	int ret = 0;
+
+	/* kprobe_running() needs smp_processor_id() */
+	if (!user_mode_vm(regs)) {
+		preempt_disable();
+		if (kprobe_running() && kprobe_fault_handler(regs, 14))
+			ret = 1;
+		preempt_enable();
+	}
 
-int unregister_page_fault_notifier(struct notifier_block *nb)
-{
-	return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
+	return ret;
 }
-EXPORT_SYMBOL_GPL(unregister_page_fault_notifier);
-
-static inline int notify_page_fault(struct pt_regs *regs, long err)
+#else
+static inline int notify_page_fault(struct pt_regs *regs)
 {
-	struct die_args args = {
-		.regs = regs,
-		.str = "page fault",
-		.err = err,
-		.trapnr = 14,
-		.signr = SIGSEGV
-	};
-	return atomic_notifier_call_chain(&notify_page_fault_chain,
-	                                  DIE_PAGE_FAULT, &args);
+	return 0;
 }
+#endif
 
 /*
  * Return EIP plus the CS segment base.  The segment limit is also
@@ -331,7 +326,7 @@ fastcall void __kprobes do_page_fault(struct pt_regs *regs,
 	if (unlikely(address >= TASK_SIZE)) {
 		if (!(error_code & 0x0000000d) && vmalloc_fault(address) >= 0)
 			return;
-		if (notify_page_fault(regs, error_code) == NOTIFY_STOP)
+		if (notify_page_fault(regs))
 			return;
 		/*
 		 * Don't take the mm semaphore here. If we fixup a prefetch
@@ -340,7 +335,7 @@ fastcall void __kprobes do_page_fault(struct pt_regs *regs,
 		goto bad_area_nosemaphore;
 	}
 
-	if (notify_page_fault(regs, error_code) == NOTIFY_STOP)
+	if (notify_page_fault(regs))
 		return;
 
 	/* It's safe to allow irq's after cr2 has been saved and the vmalloc
diff --git a/arch/x86/mm/fault_64.c b/arch/x86/mm/fault_64.c
index 54816adb8e9..5e0e54906c4 100644
--- a/arch/x86/mm/fault_64.c
+++ b/arch/x86/mm/fault_64.c
@@ -25,6 +25,7 @@
 #include <linux/kprobes.h>
 #include <linux/uaccess.h>
 #include <linux/kdebug.h>
+#include <linux/kprobes.h>
 
 #include <asm/system.h>
 #include <asm/pgalloc.h>
@@ -40,34 +41,27 @@
 #define PF_RSVD	(1<<3)
 #define PF_INSTR	(1<<4)
 
-static ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);
-
-/* Hook to register for page fault notifications */
-int register_page_fault_notifier(struct notifier_block *nb)
+#ifdef CONFIG_KPROBES
+static inline int notify_page_fault(struct pt_regs *regs)
 {
-	vmalloc_sync_all();
-	return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
-}
-EXPORT_SYMBOL_GPL(register_page_fault_notifier);
+	int ret = 0;
+
+	/* kprobe_running() needs smp_processor_id() */
+	if (!user_mode(regs)) {
+		preempt_disable();
+		if (kprobe_running() && kprobe_fault_handler(regs, 14))
+			ret = 1;
+		preempt_enable();
+	}
 
-int unregister_page_fault_notifier(struct notifier_block *nb)
-{
-	return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
+	return ret;
 }
-EXPORT_SYMBOL_GPL(unregister_page_fault_notifier);
-
-static inline int notify_page_fault(struct pt_regs *regs, long err)
+#else
+static inline int notify_page_fault(struct pt_regs *regs)
 {
-	struct die_args args = {
-		.regs = regs,
-		.str = "page fault",
-		.err = err,
-		.trapnr = 14,
-		.signr = SIGSEGV
-	};
-	return atomic_notifier_call_chain(&notify_page_fault_chain,
-	                                  DIE_PAGE_FAULT, &args);
+	return 0;
 }
+#endif
 
 /* Sometimes the CPU reports invalid exceptions on prefetch.
    Check that here and ignore.
@@ -345,7 +339,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 			if (vmalloc_fault(address) >= 0)
 				return;
 		}
-		if (notify_page_fault(regs, error_code) == NOTIFY_STOP)
+		if (notify_page_fault(regs))
 			return;
 		/*
 		 * Don't take the mm semaphore here. If we fixup a prefetch
@@ -354,7 +348,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 		goto bad_area_nosemaphore;
 	}
 
-	if (notify_page_fault(regs, error_code) == NOTIFY_STOP)
+	if (notify_page_fault(regs))
 		return;
 
 	if (likely(regs->eflags & X86_EFLAGS_IF))