blob: 9c632cb88546cfc398bf3d96ffb407d8341e67b5 [file] [log] [blame]
/*
* /dev/mcelog driver
*
* K8 parts Copyright 2002,2003 Andi Kleen, SuSE Labs.
* Rest from unknown author(s).
* 2004 Andi Kleen. Rewrote most of it.
* Copyright 2008 Intel Corporation
* Author: Andi Kleen
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/miscdevice.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/poll.h>
#include "mce-internal.h"
static DEFINE_MUTEX(mce_chrdev_read_mutex);
static char mce_helper[128];
static char *mce_helper_argv[2] = { mce_helper, NULL };
#define mce_log_get_idx_check(p) \
({ \
RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
!lockdep_is_held(&mce_chrdev_read_mutex), \
"suspicious mce_log_get_idx_check() usage"); \
smp_load_acquire(&(p)); \
})
/*
* Lockless MCE logging infrastructure.
* This avoids deadlocks on printk locks without having to break locks. Also
* separate MCEs from kernel messages to avoid bogus bug reports.
*/
static struct mce_log_buffer mcelog = {
.signature = MCE_LOG_SIGNATURE,
.len = MCE_LOG_LEN,
.recordlen = sizeof(struct mce),
};
static DECLARE_WAIT_QUEUE_HEAD(mce_chrdev_wait);
/* User mode helper program triggered by machine check event */
extern char mce_helper[128];
static int dev_mce_log(struct notifier_block *nb, unsigned long val,
void *data)
{
struct mce *mce = (struct mce *)data;
unsigned int next, entry;
wmb();
for (;;) {
entry = mce_log_get_idx_check(mcelog.next);
for (;;) {
/*
* When the buffer fills up discard new entries.
* Assume that the earlier errors are the more
* interesting ones:
*/
if (entry >= MCE_LOG_LEN) {
set_bit(MCE_OVERFLOW,
(unsigned long *)&mcelog.flags);
return NOTIFY_OK;
}
/* Old left over entry. Skip: */
if (mcelog.entry[entry].finished) {
entry++;
continue;
}
break;
}
smp_rmb();
next = entry + 1;
if (cmpxchg(&mcelog.next, entry, next) == entry)
break;
}
memcpy(mcelog.entry + entry, mce, sizeof(struct mce));
wmb();
mcelog.entry[entry].finished = 1;
wmb();
/* wake processes polling /dev/mcelog */
wake_up_interruptible(&mce_chrdev_wait);
return NOTIFY_OK;
}
static struct notifier_block dev_mcelog_nb = {
.notifier_call = dev_mce_log,
.priority = MCE_PRIO_MCELOG,
};
static void mce_do_trigger(struct work_struct *work)
{
call_usermodehelper(mce_helper, mce_helper_argv, NULL, UMH_NO_WAIT);
}
static DECLARE_WORK(mce_trigger_work, mce_do_trigger);
void mce_work_trigger(void)
{
if (mce_helper[0])
schedule_work(&mce_trigger_work);
}
static ssize_t
show_trigger(struct device *s, struct device_attribute *attr, char *buf)
{
strcpy(buf, mce_helper);
strcat(buf, "\n");
return strlen(mce_helper) + 1;
}
static ssize_t set_trigger(struct device *s, struct device_attribute *attr,
const char *buf, size_t siz)
{
char *p;
strncpy(mce_helper, buf, sizeof(mce_helper));
mce_helper[sizeof(mce_helper)-1] = 0;
p = strchr(mce_helper, '\n');
if (p)
*p = 0;
return strlen(mce_helper) + !!p;
}
DEVICE_ATTR(trigger, 0644, show_trigger, set_trigger);
/*
* mce_chrdev: Character device /dev/mcelog to read and clear the MCE log.
*/
static DEFINE_SPINLOCK(mce_chrdev_state_lock);
static int mce_chrdev_open_count; /* #times opened */
static int mce_chrdev_open_exclu; /* already open exclusive? */
static int mce_chrdev_open(struct inode *inode, struct file *file)
{
spin_lock(&mce_chrdev_state_lock);
if (mce_chrdev_open_exclu ||
(mce_chrdev_open_count && (file->f_flags & O_EXCL))) {
spin_unlock(&mce_chrdev_state_lock);
return -EBUSY;
}
if (file->f_flags & O_EXCL)
mce_chrdev_open_exclu = 1;
mce_chrdev_open_count++;
spin_unlock(&mce_chrdev_state_lock);
return nonseekable_open(inode, file);
}
static int mce_chrdev_release(struct inode *inode, struct file *file)
{
spin_lock(&mce_chrdev_state_lock);
mce_chrdev_open_count--;
mce_chrdev_open_exclu = 0;
spin_unlock(&mce_chrdev_state_lock);
return 0;
}
static void collect_tscs(void *data)
{
unsigned long *cpu_tsc = (unsigned long *)data;
cpu_tsc[smp_processor_id()] = rdtsc();
}
static int mce_apei_read_done;
/* Collect MCE record of previous boot in persistent storage via APEI ERST. */
static int __mce_read_apei(char __user **ubuf, size_t usize)
{
int rc;
u64 record_id;
struct mce m;
if (usize < sizeof(struct mce))
return -EINVAL;
rc = apei_read_mce(&m, &record_id);
/* Error or no more MCE record */
if (rc <= 0) {
mce_apei_read_done = 1;
/*
* When ERST is disabled, mce_chrdev_read() should return
* "no record" instead of "no device."
*/
if (rc == -ENODEV)
return 0;
return rc;
}
rc = -EFAULT;
if (copy_to_user(*ubuf, &m, sizeof(struct mce)))
return rc;
/*
* In fact, we should have cleared the record after that has
* been flushed to the disk or sent to network in
* /sbin/mcelog, but we have no interface to support that now,
* so just clear it to avoid duplication.
*/
rc = apei_clear_mce(record_id);
if (rc) {
mce_apei_read_done = 1;
return rc;
}
*ubuf += sizeof(struct mce);
return 0;
}
static ssize_t mce_chrdev_read(struct file *filp, char __user *ubuf,
size_t usize, loff_t *off)
{
char __user *buf = ubuf;
unsigned long *cpu_tsc;
unsigned prev, next;
int i, err;
cpu_tsc = kmalloc(nr_cpu_ids * sizeof(long), GFP_KERNEL);
if (!cpu_tsc)
return -ENOMEM;
mutex_lock(&mce_chrdev_read_mutex);
if (!mce_apei_read_done) {
err = __mce_read_apei(&buf, usize);
if (err || buf != ubuf)
goto out;
}
next = mce_log_get_idx_check(mcelog.next);
/* Only supports full reads right now */
err = -EINVAL;
if (*off != 0 || usize < MCE_LOG_LEN*sizeof(struct mce))
goto out;
err = 0;
prev = 0;
do {
for (i = prev; i < next; i++) {
unsigned long start = jiffies;
struct mce *m = &mcelog.entry[i];
while (!m->finished) {
if (time_after_eq(jiffies, start + 2)) {
memset(m, 0, sizeof(*m));
goto timeout;
}
cpu_relax();
}
smp_rmb();
err |= copy_to_user(buf, m, sizeof(*m));
buf += sizeof(*m);
timeout:
;
}
memset(mcelog.entry + prev, 0,
(next - prev) * sizeof(struct mce));
prev = next;
next = cmpxchg(&mcelog.next, prev, 0);
} while (next != prev);
synchronize_sched();
/*
* Collect entries that were still getting written before the
* synchronize.
*/
on_each_cpu(collect_tscs, cpu_tsc, 1);
for (i = next; i < MCE_LOG_LEN; i++) {
struct mce *m = &mcelog.entry[i];
if (m->finished && m->tsc < cpu_tsc[m->cpu]) {
err |= copy_to_user(buf, m, sizeof(*m));
smp_rmb();
buf += sizeof(*m);
memset(m, 0, sizeof(*m));
}
}
if (err)
err = -EFAULT;
out:
mutex_unlock(&mce_chrdev_read_mutex);
kfree(cpu_tsc);
return err ? err : buf - ubuf;
}
static unsigned int mce_chrdev_poll(struct file *file, poll_table *wait)
{
poll_wait(file, &mce_chrdev_wait, wait);
if (READ_ONCE(mcelog.next))
return POLLIN | POLLRDNORM;
if (!mce_apei_read_done && apei_check_mce())
return POLLIN | POLLRDNORM;
return 0;
}
static long mce_chrdev_ioctl(struct file *f, unsigned int cmd,
unsigned long arg)
{
int __user *p = (int __user *)arg;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
switch (cmd) {
case MCE_GET_RECORD_LEN:
return put_user(sizeof(struct mce), p);
case MCE_GET_LOG_LEN:
return put_user(MCE_LOG_LEN, p);
case MCE_GETCLEAR_FLAGS: {
unsigned flags;
do {
flags = mcelog.flags;
} while (cmpxchg(&mcelog.flags, flags, 0) != flags);
return put_user(flags, p);
}
default:
return -ENOTTY;
}
}
static ssize_t (*mce_write)(struct file *filp, const char __user *ubuf,
size_t usize, loff_t *off);
void register_mce_write_callback(ssize_t (*fn)(struct file *filp,
const char __user *ubuf,
size_t usize, loff_t *off))
{
mce_write = fn;
}
EXPORT_SYMBOL_GPL(register_mce_write_callback);
static ssize_t mce_chrdev_write(struct file *filp, const char __user *ubuf,
size_t usize, loff_t *off)
{
if (mce_write)
return mce_write(filp, ubuf, usize, off);
else
return -EINVAL;
}
static const struct file_operations mce_chrdev_ops = {
.open = mce_chrdev_open,
.release = mce_chrdev_release,
.read = mce_chrdev_read,
.write = mce_chrdev_write,
.poll = mce_chrdev_poll,
.unlocked_ioctl = mce_chrdev_ioctl,
.llseek = no_llseek,
};
static struct miscdevice mce_chrdev_device = {
MISC_MCELOG_MINOR,
"mcelog",
&mce_chrdev_ops,
};
static __init int dev_mcelog_init_device(void)
{
int err;
/* register character device /dev/mcelog */
err = misc_register(&mce_chrdev_device);
if (err) {
pr_err("Unable to init device /dev/mcelog (rc: %d)\n", err);
return err;
}
mce_register_decode_chain(&dev_mcelog_nb);
return 0;
}
device_initcall_sync(dev_mcelog_init_device);