x86: mmiotrace full patch, preview 1

kmmio.c handles the list of mmio probes with callbacks, list of traced
pages, and attaching into the page fault handler and die notifier. It
arms, traps and disarms the given pages, this is the core of mmiotrace.

mmio-mod.c is a user interface, hooking into ioremap functions and
registering the mmio probes. It also decodes the required information
from trapped mmio accesses via the pre and post callbacks in each probe.
Currently, hooking into ioremap functions works by redefining the symbols
of the target (binary) kernel module, so that it calls the traced
versions of the functions.

The most notable changes done since the last discussion are:
- kmmio.c is a built-in, not part of the module
- direct call from fault.c to kmmio.c, removing all dynamic hooks
- prepare for unregistering probes at any time
- make kmmio re-initializable and accessible to more than one user
- rewrite kmmio locking to remove all spinlocks from page fault path

Can I abuse call_rcu() like I do in kmmio.c:unregister_kmmio_probe()
or is there a better way?

The function called via call_rcu() itself calls call_rcu() again,
will this work or break? There I need a second grace period for RCU
after the first grace period for page faults.

Mmiotrace itself (mmio-mod.c) is still a module, I am going to attack
that next. At some point I will start looking into how to make mmiotrace
a tracer component of ftrace (thanks for the hint, Ingo). Ftrace should
make the user space part of mmiotracing as simple as
'cat /debug/trace/mmio > dump.txt'.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

10 files changed, 335 insertions, 281 deletions

diff --git a/arch/x86/kernel/init_task.c b/arch/x86/kernel/init_task.c
index 027a5b6a12b2..a4f93b4120c1 100644
--- a/arch/x86/kernel/init_task.c
+++ b/arch/x86/kernel/init_task.c
@@ -15,7 +15,6 @@ static struct signal_struct init_signals = INIT_SIGNALS(init_signals);
 static struct sighand_struct init_sighand = INIT_SIGHAND(init_sighand);
 struct mm_struct init_mm = INIT_MM(init_mm);
 EXPORT_UNUSED_SYMBOL(init_mm); /* will be removed in 2.6.26 */
-EXPORT_SYMBOL_GPL(init_mm);
 
 /*
  * Initial thread structure.
diff --git a/arch/x86/kernel/mmiotrace/Makefile b/arch/x86/kernel/mmiotrace/Makefile
index d6905f7f981b..cf1e747b463e 100644
--- a/arch/x86/kernel/mmiotrace/Makefile
+++ b/arch/x86/kernel/mmiotrace/Makefile
@@ -1,4 +1,4 @@
-obj-$(CONFIG_MMIOTRACE) += mmiotrace.o
-mmiotrace-objs := pf_in.o kmmio.o mmio-mod.o
-
-obj-$(CONFIG_MMIOTRACE_TEST) += testmmiotrace.o
+obj-$(CONFIG_MMIOTRACE_HOOKS)	+= kmmio.o
+obj-$(CONFIG_MMIOTRACE)		+= mmiotrace.o
+mmiotrace-objs			:= pf_in.o mmio-mod.o
+obj-$(CONFIG_MMIOTRACE_TEST)	+= testmmiotrace.o
diff --git a/arch/x86/kernel/mmiotrace/kmmio.c b/arch/x86/kernel/mmiotrace/kmmio.c
index 5e239d0b8467..539a9b19588f 100644
--- a/arch/x86/kernel/mmiotrace/kmmio.c
+++ b/arch/x86/kernel/mmiotrace/kmmio.c
@@ -6,6 +6,7 @@
  */
 
 #include <linux/version.h>
+#include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/hash.h>
 #include <linux/init.h>
@@ -17,70 +18,119 @@
 #include <linux/ptrace.h>
 #include <linux/preempt.h>
 #include <linux/percpu.h>
+#include <linux/kdebug.h>
 #include <asm/io.h>
 #include <asm/cacheflush.h>
 #include <asm/errno.h>
 #include <asm/tlbflush.h>
 #include <asm/pgtable.h>
 
-#include "kmmio.h"
+#include <linux/mmiotrace.h>
 
-#define KMMIO_HASH_BITS 6
-#define KMMIO_TABLE_SIZE (1 << KMMIO_HASH_BITS)
 #define KMMIO_PAGE_HASH_BITS 4
 #define KMMIO_PAGE_TABLE_SIZE (1 << KMMIO_PAGE_HASH_BITS)
 
+struct kmmio_fault_page {
+	struct list_head list;
+	struct kmmio_fault_page *release_next;
+	unsigned long page; /* location of the fault page */
+
+	/*
+	 * Number of times this page has been registered as a part
+	 * of a probe. If zero, page is disarmed and this may be freed.
+	 * Used only by writers (RCU).
+	 */
+	int count;
+};
+
+struct kmmio_delayed_release {
+	struct rcu_head rcu;
+	struct kmmio_fault_page *release_list;
+};
+
 struct kmmio_context {
 	struct kmmio_fault_page *fpage;
 	struct kmmio_probe *probe;
 	unsigned long saved_flags;
+	unsigned long addr;
 	int active;
 };
 
-static int kmmio_page_fault(struct pt_regs *regs, unsigned long error_code,
-						unsigned long address);
 static int kmmio_die_notifier(struct notifier_block *nb, unsigned long val,
 								void *args);
 
+static DECLARE_MUTEX(kmmio_init_mutex);
 static DEFINE_SPINLOCK(kmmio_lock);
 
 /* These are protected by kmmio_lock */
+static int kmmio_initialized;
 unsigned int kmmio_count;
-static unsigned int handler_registered;
+
+/* Read-protected by RCU, write-protected by kmmio_lock. */
 static struct list_head kmmio_page_table[KMMIO_PAGE_TABLE_SIZE];
 static LIST_HEAD(kmmio_probes);
 
+static struct list_head *kmmio_page_list(unsigned long page)
+{
+	return &kmmio_page_table[hash_long(page, KMMIO_PAGE_HASH_BITS)];
+}
+
 /* Accessed per-cpu */
 static DEFINE_PER_CPU(struct kmmio_context, kmmio_ctx);
 
+/* protected by kmmio_init_mutex */
 static struct notifier_block nb_die = {
 	.notifier_call = kmmio_die_notifier
 };
 
-int init_kmmio(void)
+/**
+ * Makes sure kmmio is initialized and usable.
+ * This must be called before any other kmmio function defined here.
+ * May sleep.
+ */
+void reference_kmmio(void)
 {
-	int i;
-	for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++)
-		INIT_LIST_HEAD(&kmmio_page_table[i]);
-
-	register_die_notifier(&nb_die);
-	return 0;
+	down(&kmmio_init_mutex);
+	spin_lock_irq(&kmmio_lock);
+	if (!kmmio_initialized) {
+		int i;
+		for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++)
+			INIT_LIST_HEAD(&kmmio_page_table[i]);
+		if (register_die_notifier(&nb_die))
+			BUG();
+	}
+	kmmio_initialized++;
+	spin_unlock_irq(&kmmio_lock);
+	up(&kmmio_init_mutex);
 }
+EXPORT_SYMBOL_GPL(reference_kmmio);
 
-void cleanup_kmmio(void)
+/**
+ * Clean up kmmio after use. This must be called for every call to
+ * reference_kmmio(). All probes registered after the corresponding
+ * reference_kmmio() must have been unregistered when calling this.
+ * May sleep.
+ */
+void unreference_kmmio(void)
 {
-	/*
-	 * Assume the following have been already cleaned by calling
-	 * unregister_kmmio_probe() appropriately:
-	 * kmmio_page_table, kmmio_probes
-	 */
-	if (handler_registered) {
-		if (mmiotrace_unregister_pf(&kmmio_page_fault))
-			BUG();
-		synchronize_rcu();
+	bool unreg = false;
+
+	down(&kmmio_init_mutex);
+	spin_lock_irq(&kmmio_lock);
+
+	if (kmmio_initialized == 1) {
+		BUG_ON(is_kmmio_active());
+		unreg = true;
 	}
-	unregister_die_notifier(&nb_die);
+	kmmio_initialized--;
+	BUG_ON(kmmio_initialized < 0);
+	spin_unlock_irq(&kmmio_lock);
+
+	if (unreg)
+		unregister_die_notifier(&nb_die); /* calls sync_rcu() */
+	up(&kmmio_init_mutex);
 }
+EXPORT_SYMBOL(unreference_kmmio);
 
 /*
  * this is basically a dynamic stabbing problem:
@@ -90,33 +140,33 @@ void cleanup_kmmio(void)
  * Overlap a Point (might be simple)
  * Space Efficient Dynamic Stabbing with Fast Queries - Mikkel Thorup
  */
-/* Get the kmmio at this addr (if any). You must be holding kmmio_lock. */
+/* Get the kmmio at this addr (if any). You must be holding RCU read lock. */
 static struct kmmio_probe *get_kmmio_probe(unsigned long addr)
 {
 	struct kmmio_probe *p;
-	list_for_each_entry(p, &kmmio_probes, list) {
+	list_for_each_entry_rcu(p, &kmmio_probes, list) {
 		if (addr >= p->addr && addr <= (p->addr + p->len))
 			return p;
 	}
 	return NULL;
 }
 
+/* You must be holding RCU read lock. */
 static struct kmmio_fault_page *get_kmmio_fault_page(unsigned long page)
 {
-	struct list_head *head, *tmp;
+	struct list_head *head;
+	struct kmmio_fault_page *p;
 
 	page &= PAGE_MASK;
-	head = &kmmio_page_table[hash_long(page, KMMIO_PAGE_HASH_BITS)];
-	list_for_each(tmp, head) {
-		struct kmmio_fault_page *p
-			= list_entry(tmp, struct kmmio_fault_page, list);
+	head = kmmio_page_list(page);
+	list_for_each_entry_rcu(p, head, list) {
 		if (p->page == page)
 			return p;
 	}
-
 	return NULL;
 }
 
+/** Mark the given page as not present. Access to it will trigger a fault. */
 static void arm_kmmio_fault_page(unsigned long page, int *page_level)
 {
 	unsigned long address = page & PAGE_MASK;
@@ -124,8 +174,8 @@ static void arm_kmmio_fault_page(unsigned long page, int *page_level)
 	pte_t *pte = lookup_address(address, &level);
 
 	if (!pte) {
-		printk(KERN_ERR "Error in %s: no pte for page 0x%08lx\n",
-						__FUNCTION__, page);
+		pr_err("kmmio: Error in %s: no pte for page 0x%08lx\n",
+							__func__, page);
 		return;
 	}
 
@@ -143,6 +193,7 @@ static void arm_kmmio_fault_page(unsigned long page, int *page_level)
 	__flush_tlb_one(page);
 }
 
+/** Mark the given page as present. */
 static void disarm_kmmio_fault_page(unsigned long page, int *page_level)
 {
 	unsigned long address = page & PAGE_MASK;
@@ -150,8 +201,8 @@ static void disarm_kmmio_fault_page(unsigned long page, int *page_level)
 	pte_t *pte = lookup_address(address, &level);
 
 	if (!pte) {
-		printk(KERN_ERR "Error in %s: no pte for page 0x%08lx\n",
-						__FUNCTION__, page);
+		pr_err("kmmio: Error in %s: no pte for page 0x%08lx\n",
+							__func__, page);
 		return;
 	}
 
@@ -170,12 +221,24 @@ static void disarm_kmmio_fault_page(unsigned long page, int *page_level)
 }
 
 /*
+ * This is being called from do_page_fault().
+ *
+ * We may be in an interrupt or a critical section. Also prefecthing may
+ * trigger a page fault. We may be in the middle of process switch.
+ * We cannot take any locks, because we could be executing especially
+ * within a kmmio critical section.
+ *
+ * Local interrupts are disabled, so preemption cannot happen.
+ * Do not enable interrupts, do not sleep, and watch out for other CPUs.
+ */
+/*
  * Interrupts are disabled on entry as trap3 is an interrupt gate
  * and they remain disabled thorough out this function.
  */
-static int kmmio_handler(struct pt_regs *regs, unsigned long addr)
+int kmmio_handler(struct pt_regs *regs, unsigned long addr)
 {
-	struct kmmio_context *ctx = &get_cpu_var(kmmio_ctx);
+	struct kmmio_context *ctx;
+	struct kmmio_fault_page *faultpage;
 
 	/*
 	 * Preemption is now disabled to prevent process switch during
@@ -186,40 +249,40 @@ static int kmmio_handler(struct pt_regs *regs, unsigned long addr)
 	 * XXX what if an interrupt occurs between returning from
 	 * do_page_fault() and entering the single-step exception handler?
 	 * And that interrupt triggers a kmmio trap?
+	 * XXX If we tracing an interrupt service routine or whatever, is
+	 * this enough to keep it on the current cpu?
 	 */
 	preempt_disable();
 
-	/* interrupts disabled and CPU-local data => atomicity guaranteed. */
+	rcu_read_lock();
+	faultpage = get_kmmio_fault_page(addr);
+	if (!faultpage) {
+		/*
+		 * Either this page fault is not caused by kmmio, or
+		 * another CPU just pulled the kmmio probe from under
+		 * our feet. In the latter case all hell breaks loose.
+		 */
+		goto no_kmmio;
+	}
+
+	ctx = &get_cpu_var(kmmio_ctx);
 	if (ctx->active) {
 		/*
-		 * This avoids a deadlock with kmmio_lock.
+		 * Prevent overwriting already in-flight context.
 		 * If this page fault really was due to kmmio trap,
 		 * all hell breaks loose.
 		 */
-		printk(KERN_EMERG "mmiotrace: recursive probe hit on CPU %d, "
-					"for address %lu. Ignoring.\n",
+		pr_emerg("kmmio: recursive probe hit on CPU %d, "
+					"for address 0x%08lx. Ignoring.\n",
 					smp_processor_id(), addr);
-		goto no_kmmio;
+		goto no_kmmio_ctx;
 	}
 	ctx->active++;
 
-	/*
-	 * Acquire the kmmio lock to prevent changes affecting
-	 * get_kmmio_fault_page() and get_kmmio_probe(), since we save their
-	 * returned pointers.
-	 * The lock is released in post_kmmio_handler().
-	 * XXX: could/should get_kmmio_*() be using RCU instead of spinlock?
-	 */
-	spin_lock(&kmmio_lock);
-
-	ctx->fpage = get_kmmio_fault_page(addr);
-	if (!ctx->fpage) {
-		/* this page fault is not caused by kmmio */
-		goto no_kmmio_locked;
-	}
-
+	ctx->fpage = faultpage;
 	ctx->probe = get_kmmio_probe(addr);
 	ctx->saved_flags = (regs->flags & (TF_MASK|IF_MASK));
+	ctx->addr = addr;
 
 	if (ctx->probe && ctx->probe->pre_handler)
 		ctx->probe->pre_handler(ctx->probe, regs, addr);
@@ -227,46 +290,62 @@ static int kmmio_handler(struct pt_regs *regs, unsigned long addr)
 	regs->flags |= TF_MASK;
 	regs->flags &= ~IF_MASK;
 
-	/* We hold lock, now we set present bit in PTE and single step. */
+	/* Now we set present bit in PTE and single step. */
 	disarm_kmmio_fault_page(ctx->fpage->page, NULL);
 
 	put_cpu_var(kmmio_ctx);
+	rcu_read_unlock();
 	return 1;
 
-no_kmmio_locked:
-	spin_unlock(&kmmio_lock);
-	ctx->active--;
+no_kmmio_ctx:
+	put_cpu_var(kmmio_ctx);
 no_kmmio:
+	rcu_read_unlock();
 	preempt_enable_no_resched();
-	put_cpu_var(kmmio_ctx);
-	/* page fault not handled by kmmio */
-	return 0;
+	return 0; /* page fault not handled by kmmio */
 }
 
 /*
  * Interrupts are disabled on entry as trap1 is an interrupt gate
  * and they remain disabled thorough out this function.
- * And we hold kmmio lock.
+ * This must always get called as the pair to kmmio_handler().
  */
 static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
 {
 	int ret = 0;
+	struct kmmio_probe *probe;
+	struct kmmio_fault_page *faultpage;
 	struct kmmio_context *ctx = &get_cpu_var(kmmio_ctx);
 
 	if (!ctx->active)
 		goto out;
 
+	rcu_read_lock();
+
+	faultpage = get_kmmio_fault_page(ctx->addr);
+	probe = get_kmmio_probe(ctx->addr);
+	if (faultpage != ctx->fpage || probe != ctx->probe) {
+		/*
+		 * The trace setup changed after kmmio_handler() and before
+		 * running this respective post handler. User does not want
+		 * the result anymore.
+		 */
+		ctx->probe = NULL;
+		ctx->fpage = NULL;
+	}
+
 	if (ctx->probe && ctx->probe->post_handler)
 		ctx->probe->post_handler(ctx->probe, condition, regs);
 
-	arm_kmmio_fault_page(ctx->fpage->page, NULL);
+	if (ctx->fpage)
+		arm_kmmio_fault_page(ctx->fpage->page, NULL);
 
 	regs->flags &= ~TF_MASK;
 	regs->flags |= ctx->saved_flags;
 
 	/* These were acquired in kmmio_handler(). */
 	ctx->active--;
-	spin_unlock(&kmmio_lock);
+	BUG_ON(ctx->active);
 	preempt_enable_no_resched();
 
 	/*
@@ -277,11 +356,13 @@ static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
 	if (!(regs->flags & TF_MASK))
 		ret = 1;
 
+	rcu_read_unlock();
 out:
 	put_cpu_var(kmmio_ctx);
 	return ret;
 }
 
+/* You must be holding kmmio_lock. */
 static int add_kmmio_fault_page(unsigned long page)
 {
 	struct kmmio_fault_page *f;
@@ -289,6 +370,8 @@ static int add_kmmio_fault_page(unsigned long page)
 	page &= PAGE_MASK;
 	f = get_kmmio_fault_page(page);
 	if (f) {
+		if (!f->count)
+			arm_kmmio_fault_page(f->page, NULL);
 		f->count++;
 		return 0;
 	}
@@ -299,15 +382,16 @@ static int add_kmmio_fault_page(unsigned long page)
 
 	f->count = 1;
 	f->page = page;
-	list_add(&f->list,
-		 &kmmio_page_table[hash_long(f->page, KMMIO_PAGE_HASH_BITS)]);
+	list_add_rcu(&f->list, kmmio_page_list(f->page));
 
 	arm_kmmio_fault_page(f->page, NULL);
 
 	return 0;
 }
 
-static void release_kmmio_fault_page(unsigned long page)
+/* You must be holding kmmio_lock. */
+static void release_kmmio_fault_page(unsigned long page,
+				struct kmmio_fault_page **release_list)
 {
 	struct kmmio_fault_page *f;
 
@@ -317,9 +401,11 @@ static void release_kmmio_fault_page(unsigned long page)
 		return;
 
 	f->count--;
+	BUG_ON(f->count < 0);
 	if (!f->count) {
 		disarm_kmmio_fault_page(f->page, NULL);
-		list_del(&f->list);
+		f->release_next = *release_list;
+		*release_list = f;
 	}
 }
 
@@ -334,68 +420,113 @@ int register_kmmio_probe(struct kmmio_probe *p)
 		ret = -EEXIST;
 		goto out;
 	}
-	list_add(&p->list, &kmmio_probes);
-	/*printk("adding fault pages...\n");*/
+	list_add_rcu(&p->list, &kmmio_probes);
 	while (size < p->len) {
 		if (add_kmmio_fault_page(p->addr + size))
-			printk(KERN_ERR "mmio: Unable to set page fault.\n");
+			pr_err("kmmio: Unable to set page fault.\n");
 		size += PAGE_SIZE;
 	}
-
-	if (!handler_registered) {
-		if (mmiotrace_register_pf(&kmmio_page_fault))
-			printk(KERN_ERR "mmiotrace: Cannot register page "
-					"fault handler.\n");
-		else
-			handler_registered++;
-	}
-
 out:
 	spin_unlock_irq(&kmmio_lock);
 	/*
 	 * XXX: What should I do here?
 	 * Here was a call to global_flush_tlb(), but it does not exist
-	 * anymore.
+	 * anymore. It seems it's not needed after all.
 	 */
 	return ret;
 }
+EXPORT_SYMBOL(register_kmmio_probe);
 
+static void rcu_free_kmmio_fault_pages(struct rcu_head *head)
+{
+	struct kmmio_delayed_release *dr = container_of(
+						head,
+						struct kmmio_delayed_release,
+						rcu);
+	struct kmmio_fault_page *p = dr->release_list;
+	while (p) {
+		struct kmmio_fault_page *next = p->release_next;
+		BUG_ON(p->count);
+		kfree(p);
+		p = next;
+	}
+	kfree(dr);
+}
+
+static void remove_kmmio_fault_pages(struct rcu_head *head)
+{
+	struct kmmio_delayed_release *dr = container_of(
+						head,
+						struct kmmio_delayed_release,
+						rcu);
+	struct kmmio_fault_page *p = dr->release_list;
+	struct kmmio_fault_page **prevp = &dr->release_list;
+	unsigned long flags;
+	spin_lock_irqsave(&kmmio_lock, flags);
+	while (p) {
+		if (!p->count)
+			list_del_rcu(&p->list);
+		else
+			*prevp = p->release_next;
+		prevp = &p->release_next;
+		p = p->release_next;
+	}
+	spin_unlock_irqrestore(&kmmio_lock, flags);
+	/* This is the real RCU destroy call. */
+	call_rcu(&dr->rcu, rcu_free_kmmio_fault_pages);
+}
+
+/*
+ * Remove a kmmio probe. You have to synchronize_rcu() before you can be
+ * sure that the callbacks will not be called anymore.
+ *
+ * Unregistering a kmmio fault page has three steps:
+ * 1. release_kmmio_fault_page()
+ *    Disarm the page, wait a grace period to let all faults finish.
+ * 2. remove_kmmio_fault_pages()
+ *    Remove the pages from kmmio_page_table.
+ * 3. rcu_free_kmmio_fault_pages()
+ *    Actally free the kmmio_fault_page structs as with RCU.
+ */
 void unregister_kmmio_probe(struct kmmio_probe *p)
 {
 	unsigned long size = 0;
+	struct kmmio_fault_page *release_list = NULL;
+	struct kmmio_delayed_release *drelease;
 
 	spin_lock_irq(&kmmio_lock);
 	while (size < p->len) {
-		release_kmmio_fault_page(p->addr + size);
+		release_kmmio_fault_page(p->addr + size, &release_list);
 		size += PAGE_SIZE;
 	}
-	list_del(&p->list);
+	list_del_rcu(&p->list);
 	kmmio_count--;
 	spin_unlock_irq(&kmmio_lock);
-}
 
-/*
- * According to 2.6.20, mainly x86_64 arch:
- * This is being called from do_page_fault(), via the page fault notifier
- * chain. The chain is called for both user space faults and kernel space
- * faults (address >= TASK_SIZE64), except not on faults serviced by
- * vmalloc_fault().
- *
- * We may be in an interrupt or a critical section. Also prefecthing may
- * trigger a page fault. We may be in the middle of process switch.
- * The page fault hook functionality has put us inside RCU read lock.
- *
- * Local interrupts are disabled, so preemption cannot happen.
- * Do not enable interrupts, do not sleep, and watch out for other CPUs.
- */
-static int kmmio_page_fault(struct pt_regs *regs, unsigned long error_code,
-						unsigned long address)
-{
-	if (is_kmmio_active())
-		if (kmmio_handler(regs, address) == 1)
-			return -1;
-	return 0;
+	drelease = kmalloc(sizeof(*drelease), GFP_ATOMIC);
+	if (!drelease) {
+		pr_crit("kmmio: leaking kmmio_fault_page objects.\n");
+		return;
+	}
+	drelease->release_list = release_list;
+
+	/*
+	 * This is not really RCU here. We have just disarmed a set of
+	 * pages so that they cannot trigger page faults anymore. However,
+	 * we cannot remove the pages from kmmio_page_table,
+	 * because a probe hit might be in flight on another CPU. The
+	 * pages are collected into a list, and they will be removed from
+	 * kmmio_page_table when it is certain that no probe hit related to
+	 * these pages can be in flight. RCU grace period sounds like a
+	 * good choice.
+	 *
+	 * If we removed the pages too early, kmmio page fault handler might
+	 * not find the respective kmmio_fault_page and determine it's not
+	 * a kmmio fault, when it actually is. This would lead to madness.
+	 */
+	call_rcu(&drelease->rcu, remove_kmmio_fault_pages);
 }
+EXPORT_SYMBOL(unregister_kmmio_probe);
 
 static int kmmio_die_notifier(struct notifier_block *nb, unsigned long val,
 								void *args)
diff --git a/arch/x86/kernel/mmiotrace/kmmio.h b/arch/x86/kernel/mmiotrace/kmmio.h
deleted file mode 100644
index 85b7f68a3b8a..000000000000
--- a/arch/x86/kernel/mmiotrace/kmmio.h
+++ /dev/null
@@ -1,58 +0,0 @@
-#ifndef _LINUX_KMMIO_H
-#define _LINUX_KMMIO_H
-
-#include <linux/list.h>
-#include <linux/notifier.h>
-#include <linux/smp.h>
-#include <linux/types.h>
-#include <linux/ptrace.h>
-#include <linux/version.h>
-#include <linux/kdebug.h>
-
-struct kmmio_probe;
-struct kmmio_fault_page;
-struct pt_regs;
-
-typedef void (*kmmio_pre_handler_t)(struct kmmio_probe *,
-				struct pt_regs *, unsigned long addr);
-typedef void (*kmmio_post_handler_t)(struct kmmio_probe *,
-				unsigned long condition, struct pt_regs *);
-
-struct kmmio_probe {
-	struct list_head list;
-
-	/* start location of the probe point */
-	unsigned long addr;
-
-	/* length of the probe region */
-	unsigned long len;
-
-	 /* Called before addr is executed. */
-	kmmio_pre_handler_t pre_handler;
-
-	/* Called after addr is executed, unless... */
-	kmmio_post_handler_t post_handler;
-};
-
-struct kmmio_fault_page {
-	struct list_head list;
-
-	/* location of the fault page */
-	unsigned long page;
-
-	int count;
-};
-
-/* kmmio is active by some kmmio_probes? */
-static inline int is_kmmio_active(void)
-{
-	extern unsigned int kmmio_count;
-	return kmmio_count;
-}
-
-int init_kmmio(void);
-void cleanup_kmmio(void);
-int register_kmmio_probe(struct kmmio_probe *p);
-void unregister_kmmio_probe(struct kmmio_probe *p);
-
-#endif /* _LINUX_KMMIO_H */
diff --git a/arch/x86/kernel/mmiotrace/mmio-mod.c b/arch/x86/kernel/mmiotrace/mmio-mod.c
index f9c609266d83..e1a508588f03 100644
--- a/arch/x86/kernel/mmiotrace/mmio-mod.c
+++ b/arch/x86/kernel/mmiotrace/mmio-mod.c
@@ -32,7 +32,6 @@
 #include <asm/atomic.h>
 #include <linux/percpu.h>
 
-#include "kmmio.h"
 #include "pf_in.h"
 
 /* This app's relay channel files will appear in /debug/mmio-trace */
@@ -129,18 +128,17 @@ static void print_pte(unsigned long address)
 	pte_t *pte = lookup_address(address, &level);
 
 	if (!pte) {
-		printk(KERN_ERR "Error in %s: no pte for page 0x%08lx\n",
-						__FUNCTION__, address);
+		pr_err(MODULE_NAME ": Error in %s: no pte for page 0x%08lx\n",
+							__func__, address);
 		return;
 	}
 
 	if (level == PG_LEVEL_2M) {
-		printk(KERN_EMERG MODULE_NAME ": 4MB pages are not "
-						"currently supported: %lx\n",
-						address);
+		pr_emerg(MODULE_NAME ": 4MB pages are not currently "
+						"supported: %lx\n", address);
 		BUG();
 	}
-	printk(KERN_DEBUG MODULE_NAME ": pte for 0x%lx: 0x%lx 0x%lx\n",
+	pr_info(MODULE_NAME ": pte for 0x%lx: 0x%lx 0x%lx\n",
 					address, pte_val(*pte),
 					pte_val(*pte) & _PAGE_PRESENT);
 }
@@ -152,7 +150,7 @@ static void print_pte(unsigned long address)
 static void die_kmmio_nesting_error(struct pt_regs *regs, unsigned long addr)
 {
 	const struct trap_reason *my_reason = &get_cpu_var(pf_reason);
-	printk(KERN_EMERG MODULE_NAME ": unexpected fault for address: %lx, "
+	pr_emerg(MODULE_NAME ": unexpected fault for address: %lx, "
 					"last fault for address: %lx\n",
 					addr, my_reason->addr);
 	print_pte(addr);
@@ -160,20 +158,17 @@ static void die_kmmio_nesting_error(struct pt_regs *regs, unsigned long addr)
 	print_symbol(KERN_EMERG "faulting EIP is at %s\n", regs->ip);
 	print_symbol(KERN_EMERG "last faulting EIP was at %s\n",
 							my_reason->ip);
-	printk(KERN_EMERG
-			"eax: %08lx   ebx: %08lx   ecx: %08lx   edx: %08lx\n",
+	pr_emerg("eax: %08lx   ebx: %08lx   ecx: %08lx   edx: %08lx\n",
 			regs->ax, regs->bx, regs->cx, regs->dx);
-	printk(KERN_EMERG
-			"esi: %08lx   edi: %08lx   ebp: %08lx   esp: %08lx\n",
+	pr_emerg("esi: %08lx   edi: %08lx   ebp: %08lx   esp: %08lx\n",
 			regs->si, regs->di, regs->bp, regs->sp);
 #else
 	print_symbol(KERN_EMERG "faulting RIP is at %s\n", regs->ip);
 	print_symbol(KERN_EMERG "last faulting RIP was at %s\n",
 							my_reason->ip);
-	printk(KERN_EMERG "rax: %016lx   rcx: %016lx   rdx: %016lx\n",
+	pr_emerg("rax: %016lx   rcx: %016lx   rdx: %016lx\n",
 					regs->ax, regs->cx, regs->dx);
-	printk(KERN_EMERG "rsi: %016lx   rdi: %016lx   "
-				"rbp: %016lx   rsp: %016lx\n",
+	pr_emerg("rsi: %016lx   rdi: %016lx   rbp: %016lx   rsp: %016lx\n",
 				regs->si, regs->di, regs->bp, regs->sp);
 #endif
 	put_cpu_var(pf_reason);
@@ -251,10 +246,15 @@ static void post(struct kmmio_probe *p, unsigned long condition,
 	struct trap_reason *my_reason = &get_cpu_var(pf_reason);
 	struct mm_io_header_rw *my_trace = &get_cpu_var(cpu_trace);
 
+	/*
+	 * XXX: This might not get called, if the probe is removed while
+	 * trace hit is on flight.
+	 */
+
 	/* this should always return the active_trace count to 0 */
 	my_reason->active_traces--;
 	if (my_reason->active_traces) {
-		printk(KERN_EMERG MODULE_NAME ": unexpected post handler");
+		pr_emerg(MODULE_NAME ": unexpected post handler");
 		BUG();
 	}
 
@@ -283,16 +283,15 @@ static int subbuf_start_handler(struct rchan_buf *buf, void *subbuf,
 	atomic_t *drop = &per_cpu(dropped, cpu);
 	int count;
 	if (relay_buf_full(buf)) {
-		if (atomic_inc_return(drop) == 1) {
-			printk(KERN_ERR MODULE_NAME ": cpu %d buffer full!\n",
-									cpu);
-		}
+		if (atomic_inc_return(drop) == 1)
+			pr_err(MODULE_NAME ": cpu %d buffer full!\n", cpu);
 		return 0;
-	} else if ((count = atomic_read(drop))) {
-		printk(KERN_ERR MODULE_NAME
-					": cpu %d buffer no longer full, "
-					"missed %d events.\n",
-					cpu, count);
+	}
+	count = atomic_read(drop);
+	if (count) {
+		pr_err(MODULE_NAME ": cpu %d buffer no longer full, "
+						"missed %d events.\n",
+						cpu, count);
 		atomic_sub(count, drop);
 	}
 
@@ -407,8 +406,8 @@ static void ioremap_trace_core(unsigned long offset, unsigned long size,
 	/* Don't trace the low PCI/ISA area, it's always mapped.. */
 	if (!ISA_trace && (offset < ISA_END_ADDRESS) &&
 					(offset + size > ISA_START_ADDRESS)) {
-		printk(KERN_NOTICE MODULE_NAME ": Ignoring map of low "
-						"PCI/ISA area (0x%lx-0x%lx)\n",
+		pr_notice(MODULE_NAME ": Ignoring map of low PCI/ISA area "
+						"(0x%lx-0x%lx)\n",
 						offset, offset + size);
 		return;
 	}
@@ -418,7 +417,7 @@ static void ioremap_trace_core(unsigned long offset, unsigned long size,
 void __iomem *ioremap_cache_trace(unsigned long offset, unsigned long size)
 {
 	void __iomem *p = ioremap_cache(offset, size);
-	printk(KERN_DEBUG MODULE_NAME ": ioremap_cache(0x%lx, 0x%lx) = %p\n",
+	pr_debug(MODULE_NAME ": ioremap_cache(0x%lx, 0x%lx) = %p\n",
 							offset, size, p);
 	ioremap_trace_core(offset, size, p);
 	return p;
@@ -428,7 +427,7 @@ EXPORT_SYMBOL(ioremap_cache_trace);
 void __iomem *ioremap_nocache_trace(unsigned long offset, unsigned long size)
 {
 	void __iomem *p = ioremap_nocache(offset, size);
-	printk(KERN_DEBUG MODULE_NAME ": ioremap_nocache(0x%lx, 0x%lx) = %p\n",
+	pr_debug(MODULE_NAME ": ioremap_nocache(0x%lx, 0x%lx) = %p\n",
 							offset, size, p);
 	ioremap_trace_core(offset, size, p);
 	return p;
@@ -455,7 +454,7 @@ void iounmap_trace(volatile void __iomem *addr)
 	};
 	struct remap_trace *trace;
 	struct remap_trace *tmp;
-	printk(KERN_DEBUG MODULE_NAME ": Unmapping %p.\n", addr);
+	pr_debug(MODULE_NAME ": Unmapping %p.\n", addr);
 	record_timestamp(&event.header);
 
 	spin_lock(&trace_list_lock);
@@ -481,7 +480,7 @@ static void clear_trace_list(void)
 
 	spin_lock(&trace_list_lock);
 	list_for_each_entry_safe(trace, tmp, &trace_list, list) {
-		printk(KERN_WARNING MODULE_NAME ": purging non-iounmapped "
+		pr_warning(MODULE_NAME ": purging non-iounmapped "
 					"trace @0x%08lx, size 0x%lx.\n",
 					trace->probe.addr, trace->probe.len);
 		if (!nommiotrace)
@@ -500,39 +499,37 @@ static int __init init(void)
 
 	dir = debugfs_create_dir(APP_DIR, NULL);
 	if (!dir) {
-		printk(KERN_ERR MODULE_NAME
-				": Couldn't create relay app directory.\n");
+		pr_err(MODULE_NAME ": Couldn't create relay app directory.\n");
 		return -ENOMEM;
 	}
 
 	chan = create_channel(subbuf_size, n_subbufs);
 	if (!chan) {
 		debugfs_remove(dir);
-		printk(KERN_ERR MODULE_NAME
-				": relay app channel creation failed\n");
+		pr_err(MODULE_NAME ": relay app channel creation failed\n");
 		return -ENOMEM;
 	}
 
-	init_kmmio();
+	reference_kmmio();
 
 	proc_marker_file = create_proc_entry(MARKER_FILE, 0, NULL);
 	if (proc_marker_file)
 		proc_marker_file->write_proc = write_marker;
 
-	printk(KERN_DEBUG MODULE_NAME ": loaded.\n");
+	pr_debug(MODULE_NAME ": loaded.\n");
 	if (nommiotrace)
-		printk(KERN_DEBUG MODULE_NAME ": MMIO tracing disabled.\n");
+		pr_info(MODULE_NAME ": MMIO tracing disabled.\n");
 	if (ISA_trace)
-		printk(KERN_WARNING MODULE_NAME
-				": Warning! low ISA range will be traced.\n");
+		pr_warning(MODULE_NAME ": Warning! low ISA range will be "
+								"traced.\n");
 	return 0;
 }
 
 static void __exit cleanup(void)
 {
-	printk(KERN_DEBUG MODULE_NAME ": unload...\n");
+	pr_debug(MODULE_NAME ": unload...\n");
 	clear_trace_list();
-	cleanup_kmmio();
+	unreference_kmmio();
 	remove_proc_entry(MARKER_FILE, NULL);
 	destroy_channel();
 	if (dir)
diff --git a/arch/x86/kernel/mmiotrace/pf_in.c b/arch/x86/kernel/mmiotrace/pf_in.c
index 67ea520dde62..efa1911e20ca 100644
--- a/arch/x86/kernel/mmiotrace/pf_in.c
+++ b/arch/x86/kernel/mmiotrace/pf_in.c
@@ -19,7 +19,7 @@
  *
  */
 
-/*  $Id: pf_in.c,v 1.1.1.1 2002/11/12 05:56:32 brlock Exp $
+/*  Id: pf_in.c,v 1.1.1.1 2002/11/12 05:56:32 brlock Exp
  *  Copyright by Intel Crop., 2002
  *  Louis Zhuang (louis.zhuang@intel.com)
  *
diff --git a/arch/x86/kernel/mmiotrace/testmmiotrace.c b/arch/x86/kernel/mmiotrace/testmmiotrace.c
index 40e66b0e6480..5ecff578672b 100644
--- a/arch/x86/kernel/mmiotrace/testmmiotrace.c
+++ b/arch/x86/kernel/mmiotrace/testmmiotrace.c
@@ -41,8 +41,7 @@ static void do_test(void)
 {
 	void __iomem *p = ioremap_nocache_trace(mmio_address, 0x4000);
 	if (!p) {
-		printk(KERN_ERR MODULE_NAME ": could not ioremap IO memory, "
-							"aborting.\n");
+		pr_err(MODULE_NAME ": could not ioremap, aborting.\n");
 		return;
 	}
 	do_write_test(p);
@@ -53,14 +52,14 @@ static void do_test(void)
 static int __init init(void)
 {
 	if (mmio_address == 0) {
-		printk(KERN_ERR MODULE_NAME ": you have to use the module "
-						"argument mmio_address.\n");
-		printk(KERN_ERR MODULE_NAME ": DO NOT LOAD THIS MODULE UNLESS"
+		pr_err(MODULE_NAME ": you have to use the module argument "
+							"mmio_address.\n");
+		pr_err(MODULE_NAME ": DO NOT LOAD THIS MODULE UNLESS"
 				" YOU REALLY KNOW WHAT YOU ARE DOING!\n");
 		return -ENXIO;
 	}
 
-	printk(KERN_WARNING MODULE_NAME ": WARNING: mapping 16 kB @ 0x%08lx "
+	pr_warning(MODULE_NAME ": WARNING: mapping 16 kB @ 0x%08lx "
 					"in PCI address space, and writing "
 					"rubbish in there.\n", mmio_address);
 	do_test();
@@ -69,7 +68,7 @@ static int __init init(void)
 
 static void __exit cleanup(void)
 {
-	printk(KERN_DEBUG MODULE_NAME ": unloaded.\n");
+	pr_debug(MODULE_NAME ": unloaded.\n");
 }
 
 module_init(init);
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index e9a086a1a9ff..8c828a68d3b6 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -10,6 +10,7 @@
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/ptrace.h>
+#include <linux/mmiotrace.h>
 #include <linux/mman.h>
 #include <linux/mm.h>
 #include <linux/smp.h>
@@ -49,60 +50,14 @@
 #define PF_RSVD		(1<<3)
 #define PF_INSTR	(1<<4)
 
-#ifdef CONFIG_MMIOTRACE_HOOKS
-static pf_handler_func mmiotrace_pf_handler; /* protected by RCU */
-static DEFINE_SPINLOCK(mmiotrace_handler_lock);
-
-int mmiotrace_register_pf(pf_handler_func new_pfh)
-{
-	int ret = 0;
-	unsigned long flags;
-	spin_lock_irqsave(&mmiotrace_handler_lock, flags);
-	if (mmiotrace_pf_handler)
-		ret = -EBUSY;
-	else
-		mmiotrace_pf_handler = new_pfh;
-	spin_unlock_irqrestore(&mmiotrace_handler_lock, flags);
-	return ret;
-}
-EXPORT_SYMBOL_GPL(mmiotrace_register_pf);
-
-/**
- * mmiotrace_unregister_pf:
- * The caller must ensure @old_pfh is not in use anymore before freeing it.
- * This function does not guarantee it. The handler function pointer is
- * protected by RCU, so you can do this by e.g. calling synchronize_rcu().
- */
-int mmiotrace_unregister_pf(pf_handler_func old_pfh)
-{
-	int ret = 0;
-	unsigned long flags;
-	spin_lock_irqsave(&mmiotrace_handler_lock, flags);
-	if (mmiotrace_pf_handler != old_pfh)
-		ret = -EPERM;
-	else
-		mmiotrace_pf_handler = NULL;
-	spin_unlock_irqrestore(&mmiotrace_handler_lock, flags);
-	return ret;
-}
-EXPORT_SYMBOL_GPL(mmiotrace_unregister_pf);
-#endif /* CONFIG_MMIOTRACE_HOOKS */
-
-/* returns non-zero if do_page_fault() should return */
-static inline int call_mmiotrace(struct pt_regs *regs,
-					unsigned long error_code,
-					unsigned long address)
+static inline int kmmio_fault(struct pt_regs *regs, unsigned long addr)
 {
 #ifdef CONFIG_MMIOTRACE_HOOKS
-	int ret = 0;
-	rcu_read_lock();
-	if (mmiotrace_pf_handler)
-		ret = mmiotrace_pf_handler(regs, error_code, address);
-	rcu_read_unlock();
-	return ret;
-#else
-	return 0;
+	if (unlikely(is_kmmio_active()))
+		if (kmmio_handler(regs, addr) == 1)
+			return -1;
 #endif
+	return 0;
 }
 
 static inline int notify_page_fault(struct pt_regs *regs)
@@ -657,7 +612,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 
 	if (notify_page_fault(regs))
 		return;
-	if (call_mmiotrace(regs, error_code, address))
+	if (unlikely(kmmio_fault(regs, address)))
 		return;
 
 	/*
diff --git a/include/asm-x86/kdebug.h b/include/asm-x86/kdebug.h
index 7063281040da..96651bb59ba1 100644
--- a/include/asm-x86/kdebug.h
+++ b/include/asm-x86/kdebug.h
@@ -35,11 +35,4 @@ extern void show_regs(struct pt_regs *regs);
 extern unsigned long oops_begin(void);
 extern void oops_end(unsigned long, struct pt_regs *, int signr);
 
-typedef int (*pf_handler_func)(struct pt_regs *regs,
-				unsigned long error_code,
-				unsigned long address);
-
-extern int mmiotrace_register_pf(pf_handler_func new_pfh);
-extern int mmiotrace_unregister_pf(pf_handler_func old_pfh);
-
 #endif
diff --git a/include/linux/mmiotrace.h b/include/linux/mmiotrace.h
index 6ec288f1fe24..d87a6cd8b686 100644
--- a/include/linux/mmiotrace.h
+++ b/include/linux/mmiotrace.h
@@ -3,6 +3,44 @@
 
 #include <asm/types.h>
 
+#ifdef __KERNEL__
+
+#include <linux/list.h>
+
+struct kmmio_probe;
+struct pt_regs;
+
+typedef void (*kmmio_pre_handler_t)(struct kmmio_probe *,
+				struct pt_regs *, unsigned long addr);
+typedef void (*kmmio_post_handler_t)(struct kmmio_probe *,
+				unsigned long condition, struct pt_regs *);
+
+struct kmmio_probe {
+	struct list_head list;
+	unsigned long addr; /* start location of the probe point */
+	unsigned long len; /* length of the probe region */
+	kmmio_pre_handler_t pre_handler; /* Called before addr is executed. */
+	kmmio_post_handler_t post_handler; /* Called after addr is executed */
+};
+
+/* kmmio is active by some kmmio_probes? */
+static inline int is_kmmio_active(void)
+{
+	extern unsigned int kmmio_count;
+	return kmmio_count;
+}
+
+extern void reference_kmmio(void);
+extern void unreference_kmmio(void);
+extern int register_kmmio_probe(struct kmmio_probe *p);
+extern void unregister_kmmio_probe(struct kmmio_probe *p);
+
+/* Called from page fault handler. */
+extern int kmmio_handler(struct pt_regs *regs, unsigned long addr);
+
+#endif /* __KERNEL__ */
+
+
 /*
  * If you change anything here, you must bump MMIO_VERSION.
  * This is the relay data format for user space.