mmio-mod.c

Go to the documentation of this file.

/*
 * 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 <[email protected]>
 *
 * Derived from the read-mod example from relay-examples by Tom Zanussi.
 */

#define pr_fmt(fmt) "mmiotrace: " fmt

#define DEBUG 1

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

#include "pf_in.h"

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);

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_{rw,mapping} are allowed.
 * - pre/post callbacks assume the effect of is_enabled() being true.
 */

/* module parameters */
static unsigned long    filter_offset;
static bool     nommiotrace;
static bool     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);
}

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

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

    if (level == PG_LEVEL_2M) {
        pr_emerg("4MB pages are not currently supported: 0x%08lx\n",
             address);
        BUG();
    }
    pr_info("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("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("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("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()) {
        kfree(trace);
        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("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("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);
}

int mmiotrace_printk(const char *fmt, ...)
{
    int ret = 0;
    va_list args;
    unsigned long flags;
    va_start(args, fmt);

    spin_lock_irqsave(&trace_lock, flags);
    if (is_enabled())
        ret = mmio_trace_printk(fmt, args);
    spin_unlock_irqrestore(&trace_lock, flags);

    va_end(args);
    return ret;
}
EXPORT_SYMBOL(mmiotrace_printk);

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("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_var_t downed_cpus;

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

    if (downed_cpus == NULL &&
        !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
        pr_notice("Failed to allocate mask\n");
        goto out;
    }

    get_online_cpus();
    cpumask_copy(downed_cpus, cpu_online_mask);
    cpumask_clear_cpu(cpumask_first(cpu_online_mask), downed_cpus);
    if (num_online_cpus() > 1)
        pr_notice("Disabling non-boot CPUs...\n");
    put_online_cpus();

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

/* __ref because leave_uniprocessor calls cpu_up which is __cpuinit,
   but this whole function is ifdefed CONFIG_HOTPLUG_CPU */
static void __ref leave_uniprocessor(void)
{
    int cpu;
    int err;

    if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
        return;
    pr_notice("Re-enabling CPUs...\n");
    for_each_cpu(cpu, downed_cpus) {
        err = cpu_up(cpu);
        if (!err)
            pr_info("enabled CPU%d.\n", cpu);
        else
            pr_err("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("multiple CPUs are online, may miss events. "
               "Suggest booting with maxcpus=1 kernel argument.\n");
}

static void leave_uniprocessor(void)
{
}
#endif

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

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