arch/x86/mm/mmio-mod.c - kernel/msm-4.9 - Gitiles

 /*
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  *
  * Copyright (C) IBM Corporation, 2005
  *               Jeff Muizelaar, 2006, 2007
  *               Pekka Paalanen, 2008 <pq@iki.fi>
  *
  * Derived from the read-mod example from relay-examples by Tom Zanussi.
  */
 #define DEBUG 1

 #include <linux/module.h>
 #include <linux/debugfs.h>
 #include <linux/uaccess.h>
 #include <linux/io.h>
 #include <linux/version.h>
 #include <linux/kallsyms.h>
 #include <asm/pgtable.h>
 #include <linux/mmiotrace.h>
 #include <asm/e820.h> /* for ISA_START_ADDRESS */
 #include <asm/atomic.h>
 #include <linux/percpu.h>
 #include <linux/cpu.h>

 #include "pf_in.h"

 #define NAME "mmiotrace: "

 struct trap_reason {
 	unsigned long addr;
 	unsigned long ip;
 	enum reason_type type;
 	int active_traces;
 };

 struct remap_trace {
 	struct list_head list;
 	struct kmmio_probe probe;
 	resource_size_t phys;
 	unsigned long id;
 };

 /* Accessed per-cpu. */
 static DEFINE_PER_CPU(struct trap_reason, pf_reason);
 static DEFINE_PER_CPU(struct mmiotrace_rw, cpu_trace);

 #if 0 /* XXX: no way gather this info anymore */
 /* Access to this is not per-cpu. */
 static DEFINE_PER_CPU(atomic_t, dropped);
 #endif

 static struct dentry *marker_file;

 static DEFINE_MUTEX(mmiotrace_mutex);
 static DEFINE_SPINLOCK(trace_lock);
 static atomic_t mmiotrace_enabled;
 static LIST_HEAD(trace_list);		/* struct remap_trace */

 /*
  * Locking in this file:
  * - mmiotrace_mutex enforces enable/disable_mmiotrace() critical sections.
  * - mmiotrace_enabled may be modified only when holding mmiotrace_mutex
  *   and trace_lock.
  * - Routines depending on is_enabled() must take trace_lock.
  * - trace_list users must hold trace_lock.
  * - is_enabled() guarantees that mmio_trace_record is allowed.
  * - pre/post callbacks assume the effect of is_enabled() being true.
  */

 /* module parameters */
 static unsigned long	filter_offset;
 static int		nommiotrace;
 static int		trace_pc;

 module_param(filter_offset, ulong, 0);
 module_param(nommiotrace, bool, 0);
 module_param(trace_pc, bool, 0);

 MODULE_PARM_DESC(filter_offset, "Start address of traced mappings.");
 MODULE_PARM_DESC(nommiotrace, "Disable actual MMIO tracing.");
 MODULE_PARM_DESC(trace_pc, "Record address of faulting instructions.");

 static bool is_enabled(void)
 {
 	return atomic_read(&mmiotrace_enabled);
 }

 #if 0 /* XXX: needs rewrite */
 /*
  * Write callback for the debugfs entry:
  * Read a marker and write it to the mmio trace log
  */
 static ssize_t write_marker(struct file *file, const char __user *buffer,
 						size_t count, loff_t *ppos)
 {
 	char *event = NULL;
 	struct mm_io_header *headp;
 	ssize_t len = (count > 65535) ? 65535 : count;

 	event = kzalloc(sizeof(*headp) + len, GFP_KERNEL);
 	if (!event)
 		return -ENOMEM;

 	headp = (struct mm_io_header *)event;
 	headp->type = MMIO_MAGIC | (MMIO_MARKER << MMIO_OPCODE_SHIFT);
 	headp->data_len = len;

 	if (copy_from_user(event + sizeof(*headp), buffer, len)) {
 		kfree(event);
 		return -EFAULT;
 	}

 	spin_lock_irq(&trace_lock);
 #if 0 /* XXX: convert this to use tracing */
 	if (is_enabled())
 		relay_write(chan, event, sizeof(*headp) + len);
 	else
 #endif
 		len = -EINVAL;
 	spin_unlock_irq(&trace_lock);
 	kfree(event);
 	return len;
 }
 #endif

 static void print_pte(unsigned long address)
 {
 	unsigned int level;
 	pte_t *pte = lookup_address(address, &level);

 	if (!pte) {
 		pr_err(NAME "Error in %s: no pte for page 0x%08lx\n",
 							__func__, address);
 		return;
 	}

 	if (level == PG_LEVEL_2M) {
 		pr_emerg(NAME "4MB pages are not currently supported: "
 							"0x%08lx\n", address);
 		BUG();
 	}
 	pr_info(NAME "pte for 0x%lx: 0x%llx 0x%llx\n", address,
 		(unsigned long long)pte_val(*pte),
 		(unsigned long long)pte_val(*pte) & _PAGE_PRESENT);
 }

 /*
  * For some reason the pre/post pairs have been called in an
  * unmatched order. Report and die.
  */
 static void die_kmmio_nesting_error(struct pt_regs *regs, unsigned long addr)
 {
 	const struct trap_reason *my_reason = &get_cpu_var(pf_reason);
 	pr_emerg(NAME "unexpected fault for address: 0x%08lx, "
 					"last fault for address: 0x%08lx\n",
 					addr, my_reason->addr);
 	print_pte(addr);
 	print_symbol(KERN_EMERG "faulting IP is at %s\n", regs->ip);
 	print_symbol(KERN_EMERG "last faulting IP was at %s\n", my_reason->ip);
 #ifdef __i386__
 	pr_emerg("eax: %08lx   ebx: %08lx   ecx: %08lx   edx: %08lx\n",
 			regs->ax, regs->bx, regs->cx, regs->dx);
 	pr_emerg("esi: %08lx   edi: %08lx   ebp: %08lx   esp: %08lx\n",
 			regs->si, regs->di, regs->bp, regs->sp);
 #else
 	pr_emerg("rax: %016lx   rcx: %016lx   rdx: %016lx\n",
 					regs->ax, regs->cx, regs->dx);
 	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);
 	BUG();
 }

 static void pre(struct kmmio_probe *p, struct pt_regs *regs,
 						unsigned long addr)
 {
 	struct trap_reason *my_reason = &get_cpu_var(pf_reason);
 	struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);
 	const unsigned long instptr = instruction_pointer(regs);
 	const enum reason_type type = get_ins_type(instptr);
 	struct remap_trace *trace = p->private;

 	/* it doesn't make sense to have more than one active trace per cpu */
 	if (my_reason->active_traces)
 		die_kmmio_nesting_error(regs, addr);
 	else
 		my_reason->active_traces++;

 	my_reason->type = type;
 	my_reason->addr = addr;
 	my_reason->ip = instptr;

 	my_trace->phys = addr - trace->probe.addr + trace->phys;
 	my_trace->map_id = trace->id;

 	/*
 	 * Only record the program counter when requested.
 	 * It may taint clean-room reverse engineering.
 	 */
 	if (trace_pc)
 		my_trace->pc = instptr;
 	else
 		my_trace->pc = 0;

 	/*
 	 * XXX: the timestamp recorded will be *after* the tracing has been
 	 * done, not at the time we hit the instruction. SMP implications
 	 * on event ordering?
 	 */

 	switch (type) {
 	case REG_READ:
 		my_trace->opcode = MMIO_READ;
 		my_trace->width = get_ins_mem_width(instptr);
 		break;
 	case REG_WRITE:
 		my_trace->opcode = MMIO_WRITE;
 		my_trace->width = get_ins_mem_width(instptr);
 		my_trace->value = get_ins_reg_val(instptr, regs);
 		break;
 	case IMM_WRITE:
 		my_trace->opcode = MMIO_WRITE;
 		my_trace->width = get_ins_mem_width(instptr);
 		my_trace->value = get_ins_imm_val(instptr);
 		break;
 	default:
 		{
 			unsigned char *ip = (unsigned char *)instptr;
 			my_trace->opcode = MMIO_UNKNOWN_OP;
 			my_trace->width = 0;
 			my_trace->value = (*ip) << 16 | *(ip + 1) << 8 |
 								*(ip + 2);
 		}
 	}
 	put_cpu_var(cpu_trace);
 	put_cpu_var(pf_reason);
 }

 static void post(struct kmmio_probe *p, unsigned long condition,
 							struct pt_regs *regs)
 {
 	struct trap_reason *my_reason = &get_cpu_var(pf_reason);
 	struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);

 	/* this should always return the active_trace count to 0 */
 	my_reason->active_traces--;
 	if (my_reason->active_traces) {
 		pr_emerg(NAME "unexpected post handler");
 		BUG();
 	}

 	switch (my_reason->type) {
 	case REG_READ:
 		my_trace->value = get_ins_reg_val(my_reason->ip, regs);
 		break;
 	default:
 		break;
 	}

 	mmio_trace_rw(my_trace);
 	put_cpu_var(cpu_trace);
 	put_cpu_var(pf_reason);
 }

 static void ioremap_trace_core(resource_size_t offset, unsigned long size,
 							void __iomem *addr)
 {
 	static atomic_t next_id;
 	struct remap_trace *trace = kmalloc(sizeof(*trace), GFP_KERNEL);
 	/* These are page-unaligned. */
 	struct mmiotrace_map map = {
 		.phys = offset,
 		.virt = (unsigned long)addr,
 		.len = size,
 		.opcode = MMIO_PROBE
 	};

 	if (!trace) {
 		pr_err(NAME "kmalloc failed in ioremap\n");
 		return;
 	}

 	*trace = (struct remap_trace) {
 		.probe = {
 			.addr = (unsigned long)addr,
 			.len = size,
 			.pre_handler = pre,
 			.post_handler = post,
 			.private = trace
 		},
 		.phys = offset,
 		.id = atomic_inc_return(&next_id)
 	};
 	map.map_id = trace->id;

 	spin_lock_irq(&trace_lock);
 	if (!is_enabled())
 		goto not_enabled;

 	mmio_trace_mapping(&map);
 	list_add_tail(&trace->list, &trace_list);
 	if (!nommiotrace)
 		register_kmmio_probe(&trace->probe);

 not_enabled:
 	spin_unlock_irq(&trace_lock);
 }

 void mmiotrace_ioremap(resource_size_t offset, unsigned long size,
 						void __iomem *addr)
 {
 	if (!is_enabled()) /* recheck and proper locking in *_core() */
 		return;

 	pr_debug(NAME "ioremap_*(0x%llx, 0x%lx) = %p\n",
 				(unsigned long long)offset, size, addr);
 	if ((filter_offset) && (offset != filter_offset))
 		return;
 	ioremap_trace_core(offset, size, addr);
 }

 static void iounmap_trace_core(volatile void __iomem *addr)
 {
 	struct mmiotrace_map map = {
 		.phys = 0,
 		.virt = (unsigned long)addr,
 		.len = 0,
 		.opcode = MMIO_UNPROBE
 	};
 	struct remap_trace *trace;
 	struct remap_trace *tmp;
 	struct remap_trace *found_trace = NULL;

 	pr_debug(NAME "Unmapping %p.\n", addr);

 	spin_lock_irq(&trace_lock);
 	if (!is_enabled())
 		goto not_enabled;

 	list_for_each_entry_safe(trace, tmp, &trace_list, list) {
 		if ((unsigned long)addr == trace->probe.addr) {
 			if (!nommiotrace)
 				unregister_kmmio_probe(&trace->probe);
 			list_del(&trace->list);
 			found_trace = trace;
 			break;
 		}
 	}
 	map.map_id = (found_trace) ? found_trace->id : -1;
 	mmio_trace_mapping(&map);

 not_enabled:
 	spin_unlock_irq(&trace_lock);
 	if (found_trace) {
 		synchronize_rcu(); /* unregister_kmmio_probe() requirement */
 		kfree(found_trace);
 	}
 }

 void mmiotrace_iounmap(volatile void __iomem *addr)
 {
 	might_sleep();
 	if (is_enabled()) /* recheck and proper locking in *_core() */
 		iounmap_trace_core(addr);
 }

 static void clear_trace_list(void)
 {
 	struct remap_trace *trace;
 	struct remap_trace *tmp;

 	/*
 	 * No locking required, because the caller ensures we are in a
 	 * critical section via mutex, and is_enabled() is false,
 	 * i.e. nothing can traverse or modify this list.
 	 * Caller also ensures is_enabled() cannot change.
 	 */
 	list_for_each_entry(trace, &trace_list, list) {
 		pr_notice(NAME "purging non-iounmapped "
 					"trace @0x%08lx, size 0x%lx.\n",
 					trace->probe.addr, trace->probe.len);
 		if (!nommiotrace)
 			unregister_kmmio_probe(&trace->probe);
 	}
 	synchronize_rcu(); /* unregister_kmmio_probe() requirement */

 	list_for_each_entry_safe(trace, tmp, &trace_list, list) {
 		list_del(&trace->list);
 		kfree(trace);
 	}
 }

 #ifdef CONFIG_HOTPLUG_CPU
 static cpumask_t downed_cpus;

 static void enter_uniprocessor(void)
 {
 	int cpu;
 	int err;

 	get_online_cpus();
 	downed_cpus = cpu_online_map;
 	cpu_clear(first_cpu(cpu_online_map), downed_cpus);
 	if (num_online_cpus() > 1)
 		pr_notice(NAME "Disabling non-boot CPUs...\n");
 	put_online_cpus();

 	for_each_cpu_mask(cpu, downed_cpus) {
 		err = cpu_down(cpu);
 		if (!err)
 			pr_info(NAME "CPU%d is down.\n", cpu);
 		else
 			pr_err(NAME "Error taking CPU%d down: %d\n", cpu, err);
 	}
 	if (num_online_cpus() > 1)
 		pr_warning(NAME "multiple CPUs still online, "
 						"may miss events.\n");
 }

 static void leave_uniprocessor(void)
 {
 	int cpu;
 	int err;

 	if (cpus_weight(downed_cpus) == 0)
 		return;
 	pr_notice(NAME "Re-enabling CPUs...\n");
 	for_each_cpu_mask(cpu, downed_cpus) {
 		err = cpu_up(cpu);
 		if (!err)
 			pr_info(NAME "enabled CPU%d.\n", cpu);
 		else
 			pr_err(NAME "cannot re-enable CPU%d: %d\n", cpu, err);
 	}
 }

 #else /* !CONFIG_HOTPLUG_CPU */
 static void enter_uniprocessor(void)
 {
 	if (num_online_cpus() > 1)
 		pr_warning(NAME "multiple CPUs are online, may miss events. "
 			"Suggest booting with maxcpus=1 kernel argument.\n");
 }

 static void leave_uniprocessor(void)
 {
 }
 #endif

 #if 0 /* XXX: out of order */
 static struct file_operations fops_marker = {
 	.owner =	THIS_MODULE,
 	.write =	write_marker
 };
 #endif

 void enable_mmiotrace(void)
 {
 	mutex_lock(&mmiotrace_mutex);
 	if (is_enabled())
 		goto out;

 #if 0 /* XXX: tracing does not support text entries */
 	marker_file = debugfs_create_file("marker", 0660, dir, NULL,
 								&fops_marker);
 	if (!marker_file)
 		pr_err(NAME "marker file creation failed.\n");
 #endif

 	if (nommiotrace)
 		pr_info(NAME "MMIO tracing disabled.\n");
 	enter_uniprocessor();
 	spin_lock_irq(&trace_lock);
 	atomic_inc(&mmiotrace_enabled);
 	spin_unlock_irq(&trace_lock);
 	pr_info(NAME "enabled.\n");
 out:
 	mutex_unlock(&mmiotrace_mutex);
 }

 void disable_mmiotrace(void)
 {
 	mutex_lock(&mmiotrace_mutex);
 	if (!is_enabled())
 		goto out;

 	spin_lock_irq(&trace_lock);
 	atomic_dec(&mmiotrace_enabled);
 	BUG_ON(is_enabled());
 	spin_unlock_irq(&trace_lock);

 	clear_trace_list(); /* guarantees: no more kmmio callbacks */
 	leave_uniprocessor();
 	if (marker_file) {
 		debugfs_remove(marker_file);
 		marker_file = NULL;
 	}

 	pr_info(NAME "disabled.\n");
 out:
 	mutex_unlock(&mmiotrace_mutex);
 }
	/*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	*
	* Copyright (C) IBM Corporation, 2005
	* Jeff Muizelaar, 2006, 2007
	* Pekka Paalanen, 2008 <pq@iki.fi>
	*
	* Derived from the read-mod example from relay-examples by Tom Zanussi.
	*/
	#define DEBUG 1

	#include <linux/module.h>
	#include <linux/debugfs.h>
	#include <linux/uaccess.h>
	#include <linux/io.h>
	#include <linux/version.h>
	#include <linux/kallsyms.h>
	#include <asm/pgtable.h>
	#include <linux/mmiotrace.h>
	#include <asm/e820.h> /* for ISA_START_ADDRESS */
	#include <asm/atomic.h>
	#include <linux/percpu.h>
	#include <linux/cpu.h>

	#include "pf_in.h"

	#define NAME "mmiotrace: "

	struct trap_reason {
	unsigned long addr;
	unsigned long ip;
	enum reason_type type;
	int active_traces;
	};

	struct remap_trace {
	struct list_head list;
	struct kmmio_probe probe;
	resource_size_t phys;
	unsigned long id;
	};

	/* Accessed per-cpu. */
	static DEFINE_PER_CPU(struct trap_reason, pf_reason);
	static DEFINE_PER_CPU(struct mmiotrace_rw, cpu_trace);

	#if 0 /* XXX: no way gather this info anymore */
	/* Access to this is not per-cpu. */
	static DEFINE_PER_CPU(atomic_t, dropped);
	#endif

	static struct dentry *marker_file;

	static DEFINE_MUTEX(mmiotrace_mutex);
	static DEFINE_SPINLOCK(trace_lock);
	static atomic_t mmiotrace_enabled;
	static LIST_HEAD(trace_list); /* struct remap_trace */

	/*
	* Locking in this file:
	* - mmiotrace_mutex enforces enable/disable_mmiotrace() critical sections.
	* - mmiotrace_enabled may be modified only when holding mmiotrace_mutex
	* and trace_lock.
	* - Routines depending on is_enabled() must take trace_lock.
	* - trace_list users must hold trace_lock.
	* - is_enabled() guarantees that mmio_trace_record is allowed.
	* - pre/post callbacks assume the effect of is_enabled() being true.
	*/

	/* module parameters */
	static unsigned long filter_offset;
	static int nommiotrace;
	static int trace_pc;

	module_param(filter_offset, ulong, 0);
	module_param(nommiotrace, bool, 0);
	module_param(trace_pc, bool, 0);

	MODULE_PARM_DESC(filter_offset, "Start address of traced mappings.");
	MODULE_PARM_DESC(nommiotrace, "Disable actual MMIO tracing.");
	MODULE_PARM_DESC(trace_pc, "Record address of faulting instructions.");

	static bool is_enabled(void)
	{
	return atomic_read(&mmiotrace_enabled);
	}

	#if 0 /* XXX: needs rewrite */
	/*
	* Write callback for the debugfs entry:
	* Read a marker and write it to the mmio trace log
	*/
	static ssize_t write_marker(struct file file, const char __user buffer,
	size_t count, loff_t *ppos)
	{
	char *event = NULL;
	struct mm_io_header *headp;
	ssize_t len = (count > 65535) ? 65535 : count;

	event = kzalloc(sizeof(*headp) + len, GFP_KERNEL);
	if (!event)
	return -ENOMEM;

	headp = (struct mm_io_header *)event;
	headp->type = MMIO_MAGIC \| (MMIO_MARKER << MMIO_OPCODE_SHIFT);
	headp->data_len = len;

	if (copy_from_user(event + sizeof(*headp), buffer, len)) {
	kfree(event);
	return -EFAULT;
	}

	spin_lock_irq(&trace_lock);
	#if 0 /* XXX: convert this to use tracing */
	if (is_enabled())
	relay_write(chan, event, sizeof(*headp) + len);
	else
	#endif
	len = -EINVAL;
	spin_unlock_irq(&trace_lock);
	kfree(event);
	return len;
	}
	#endif

	static void print_pte(unsigned long address)
	{
	unsigned int level;
	pte_t *pte = lookup_address(address, &level);

	if (!pte) {
	pr_err(NAME "Error in %s: no pte for page 0x%08lx\n",
	__func__, address);
	return;
	}

	if (level == PG_LEVEL_2M) {
	pr_emerg(NAME "4MB pages are not currently supported: "
	"0x%08lx\n", address);
	BUG();
	}
	pr_info(NAME "pte for 0x%lx: 0x%llx 0x%llx\n", address,
	(unsigned long long)pte_val(*pte),
	(unsigned long long)pte_val(*pte) & _PAGE_PRESENT);
	}

	/*
	* For some reason the pre/post pairs have been called in an
	* unmatched order. Report and die.
	*/
	static void die_kmmio_nesting_error(struct pt_regs *regs, unsigned long addr)
	{
	const struct trap_reason *my_reason = &get_cpu_var(pf_reason);
	pr_emerg(NAME "unexpected fault for address: 0x%08lx, "
	"last fault for address: 0x%08lx\n",
	addr, my_reason->addr);
	print_pte(addr);
	print_symbol(KERN_EMERG "faulting IP is at %s\n", regs->ip);
	print_symbol(KERN_EMERG "last faulting IP was at %s\n", my_reason->ip);
	#ifdef __i386__
	pr_emerg("eax: %08lx ebx: %08lx ecx: %08lx edx: %08lx\n",
	regs->ax, regs->bx, regs->cx, regs->dx);
	pr_emerg("esi: %08lx edi: %08lx ebp: %08lx esp: %08lx\n",
	regs->si, regs->di, regs->bp, regs->sp);
	#else
	pr_emerg("rax: %016lx rcx: %016lx rdx: %016lx\n",
	regs->ax, regs->cx, regs->dx);
	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);
	BUG();
	}

	static void pre(struct kmmio_probe p, struct pt_regs regs,
	unsigned long addr)
	{
	struct trap_reason *my_reason = &get_cpu_var(pf_reason);
	struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);
	const unsigned long instptr = instruction_pointer(regs);
	const enum reason_type type = get_ins_type(instptr);
	struct remap_trace *trace = p->private;

	/* it doesn't make sense to have more than one active trace per cpu */
	if (my_reason->active_traces)
	die_kmmio_nesting_error(regs, addr);
	else
	my_reason->active_traces++;

	my_reason->type = type;
	my_reason->addr = addr;
	my_reason->ip = instptr;

	my_trace->phys = addr - trace->probe.addr + trace->phys;
	my_trace->map_id = trace->id;

	/*
	* Only record the program counter when requested.
	* It may taint clean-room reverse engineering.
	*/
	if (trace_pc)
	my_trace->pc = instptr;
	else
	my_trace->pc = 0;

	/*
	* XXX: the timestamp recorded will be after the tracing has been
	* done, not at the time we hit the instruction. SMP implications
	* on event ordering?
	*/

	switch (type) {
	case REG_READ:
	my_trace->opcode = MMIO_READ;
	my_trace->width = get_ins_mem_width(instptr);
	break;
	case REG_WRITE:
	my_trace->opcode = MMIO_WRITE;
	my_trace->width = get_ins_mem_width(instptr);
	my_trace->value = get_ins_reg_val(instptr, regs);
	break;
	case IMM_WRITE:
	my_trace->opcode = MMIO_WRITE;
	my_trace->width = get_ins_mem_width(instptr);
	my_trace->value = get_ins_imm_val(instptr);
	break;
	default:
	{
	unsigned char ip = (unsigned char )instptr;
	my_trace->opcode = MMIO_UNKNOWN_OP;
	my_trace->width = 0;
	my_trace->value = (ip) << 16 \| (ip + 1) << 8 \|
	*(ip + 2);
	}
	}
	put_cpu_var(cpu_trace);
	put_cpu_var(pf_reason);
	}

	static void post(struct kmmio_probe *p, unsigned long condition,
	struct pt_regs *regs)
	{
	struct trap_reason *my_reason = &get_cpu_var(pf_reason);
	struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);

	/* this should always return the active_trace count to 0 */
	my_reason->active_traces--;
	if (my_reason->active_traces) {
	pr_emerg(NAME "unexpected post handler");
	BUG();
	}

	switch (my_reason->type) {
	case REG_READ:
	my_trace->value = get_ins_reg_val(my_reason->ip, regs);
	break;
	default:
	break;
	}

	mmio_trace_rw(my_trace);
	put_cpu_var(cpu_trace);
	put_cpu_var(pf_reason);
	}

	static void ioremap_trace_core(resource_size_t offset, unsigned long size,
	void __iomem *addr)
	{
	static atomic_t next_id;
	struct remap_trace trace = kmalloc(sizeof(trace), GFP_KERNEL);
	/* These are page-unaligned. */
	struct mmiotrace_map map = {
	.phys = offset,
	.virt = (unsigned long)addr,
	.len = size,
	.opcode = MMIO_PROBE
	};

	if (!trace) {
	pr_err(NAME "kmalloc failed in ioremap\n");
	return;
	}

	*trace = (struct remap_trace) {
	.probe = {
	.addr = (unsigned long)addr,
	.len = size,
	.pre_handler = pre,
	.post_handler = post,
	.private = trace
	},
	.phys = offset,
	.id = atomic_inc_return(&next_id)
	};
	map.map_id = trace->id;

	spin_lock_irq(&trace_lock);
	if (!is_enabled())
	goto not_enabled;

	mmio_trace_mapping(&map);
	list_add_tail(&trace->list, &trace_list);
	if (!nommiotrace)
	register_kmmio_probe(&trace->probe);

	not_enabled:
	spin_unlock_irq(&trace_lock);
	}

	void mmiotrace_ioremap(resource_size_t offset, unsigned long size,
	void __iomem *addr)
	{
	if (!is_enabled()) /* recheck and proper locking in _core() /
	return;

	pr_debug(NAME "ioremap_*(0x%llx, 0x%lx) = %p\n",
	(unsigned long long)offset, size, addr);
	if ((filter_offset) && (offset != filter_offset))
	return;
	ioremap_trace_core(offset, size, addr);
	}

	static void iounmap_trace_core(volatile void __iomem *addr)
	{
	struct mmiotrace_map map = {
	.phys = 0,
	.virt = (unsigned long)addr,
	.len = 0,
	.opcode = MMIO_UNPROBE
	};
	struct remap_trace *trace;
	struct remap_trace *tmp;
	struct remap_trace *found_trace = NULL;

	pr_debug(NAME "Unmapping %p.\n", addr);

	spin_lock_irq(&trace_lock);
	if (!is_enabled())
	goto not_enabled;

	list_for_each_entry_safe(trace, tmp, &trace_list, list) {
	if ((unsigned long)addr == trace->probe.addr) {
	if (!nommiotrace)
	unregister_kmmio_probe(&trace->probe);
	list_del(&trace->list);
	found_trace = trace;
	break;
	}
	}
	map.map_id = (found_trace) ? found_trace->id : -1;
	mmio_trace_mapping(&map);

	not_enabled:
	spin_unlock_irq(&trace_lock);
	if (found_trace) {
	synchronize_rcu(); /* unregister_kmmio_probe() requirement */
	kfree(found_trace);
	}
	}

	void mmiotrace_iounmap(volatile void __iomem *addr)
	{
	might_sleep();
	if (is_enabled()) /* recheck and proper locking in _core() /
	iounmap_trace_core(addr);
	}

	static void clear_trace_list(void)
	{
	struct remap_trace *trace;
	struct remap_trace *tmp;

	/*
	* No locking required, because the caller ensures we are in a
	* critical section via mutex, and is_enabled() is false,
	* i.e. nothing can traverse or modify this list.
	* Caller also ensures is_enabled() cannot change.
	*/
	list_for_each_entry(trace, &trace_list, list) {
	pr_notice(NAME "purging non-iounmapped "
	"trace @0x%08lx, size 0x%lx.\n",
	trace->probe.addr, trace->probe.len);
	if (!nommiotrace)
	unregister_kmmio_probe(&trace->probe);
	}
	synchronize_rcu(); /* unregister_kmmio_probe() requirement */

	list_for_each_entry_safe(trace, tmp, &trace_list, list) {
	list_del(&trace->list);
	kfree(trace);
	}
	}

	#ifdef CONFIG_HOTPLUG_CPU
	static cpumask_t downed_cpus;

	static void enter_uniprocessor(void)
	{
	int cpu;
	int err;

	get_online_cpus();
	downed_cpus = cpu_online_map;
	cpu_clear(first_cpu(cpu_online_map), downed_cpus);
	if (num_online_cpus() > 1)
	pr_notice(NAME "Disabling non-boot CPUs...\n");
	put_online_cpus();

	for_each_cpu_mask(cpu, downed_cpus) {
	err = cpu_down(cpu);
	if (!err)
	pr_info(NAME "CPU%d is down.\n", cpu);
	else
	pr_err(NAME "Error taking CPU%d down: %d\n", cpu, err);
	}
	if (num_online_cpus() > 1)
	pr_warning(NAME "multiple CPUs still online, "
	"may miss events.\n");
	}

	static void leave_uniprocessor(void)
	{
	int cpu;
	int err;

	if (cpus_weight(downed_cpus) == 0)
	return;
	pr_notice(NAME "Re-enabling CPUs...\n");
	for_each_cpu_mask(cpu, downed_cpus) {
	err = cpu_up(cpu);
	if (!err)
	pr_info(NAME "enabled CPU%d.\n", cpu);
	else
	pr_err(NAME "cannot re-enable CPU%d: %d\n", cpu, err);
	}
	}

	#else /* !CONFIG_HOTPLUG_CPU */
	static void enter_uniprocessor(void)
	{
	if (num_online_cpus() > 1)
	pr_warning(NAME "multiple CPUs are online, may miss events. "
	"Suggest booting with maxcpus=1 kernel argument.\n");
	}

	static void leave_uniprocessor(void)
	{
	}
	#endif

	#if 0 /* XXX: out of order */
	static struct file_operations fops_marker = {
	.owner = THIS_MODULE,
	.write = write_marker
	};
	#endif

	void enable_mmiotrace(void)
	{
	mutex_lock(&mmiotrace_mutex);
	if (is_enabled())
	goto out;

	#if 0 /* XXX: tracing does not support text entries */
	marker_file = debugfs_create_file("marker", 0660, dir, NULL,
	&fops_marker);
	if (!marker_file)
	pr_err(NAME "marker file creation failed.\n");
	#endif

	if (nommiotrace)
	pr_info(NAME "MMIO tracing disabled.\n");
	enter_uniprocessor();
	spin_lock_irq(&trace_lock);
	atomic_inc(&mmiotrace_enabled);
	spin_unlock_irq(&trace_lock);
	pr_info(NAME "enabled.\n");
	out:
	mutex_unlock(&mmiotrace_mutex);
	}

	void disable_mmiotrace(void)
	{
	mutex_lock(&mmiotrace_mutex);
	if (!is_enabled())
	goto out;

	spin_lock_irq(&trace_lock);
	atomic_dec(&mmiotrace_enabled);
	BUG_ON(is_enabled());
	spin_unlock_irq(&trace_lock);

	clear_trace_list(); /* guarantees: no more kmmio callbacks */
	leave_uniprocessor();
	if (marker_file) {
	debugfs_remove(marker_file);
	marker_file = NULL;
	}

	pr_info(NAME "disabled.\n");
	out:
	mutex_unlock(&mmiotrace_mutex);
	}