linux/fs/pstore/pmsg.c
Mark Salyzyn 5bf6d1b927 pstore/pmsg: drop bounce buffer
Removing a bounce buffer copy operation in the pmsg driver path is
always better. We also gain in overall performance by not requesting
a vmalloc on every write as this can cause precious RT tasks, such
as user facing media operation, to stall while memory is being
reclaimed. Added a write_buf_user to the pstore functions, a backup
platform write_buf_user that uses the small buffer that is part of
the instance, and implemented a ramoops write_buf_user that only
supports PSTORE_TYPE_PMSG.

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-09-08 15:01:10 -07:00

101 lines
2.3 KiB
C

/*
* Copyright 2014 Google, Inc.
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* 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.
*/
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/vmalloc.h>
#include "internal.h"
static DEFINE_MUTEX(pmsg_lock);
static ssize_t write_pmsg(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
u64 id;
int ret;
if (!count)
return 0;
/* check outside lock, page in any data. write_buf_user also checks */
if (!access_ok(VERIFY_READ, buf, count))
return -EFAULT;
mutex_lock(&pmsg_lock);
ret = psinfo->write_buf_user(PSTORE_TYPE_PMSG, 0, &id, 0, buf, 0, count,
psinfo);
mutex_unlock(&pmsg_lock);
return ret ? ret : count;
}
static const struct file_operations pmsg_fops = {
.owner = THIS_MODULE,
.llseek = noop_llseek,
.write = write_pmsg,
};
static struct class *pmsg_class;
static int pmsg_major;
#define PMSG_NAME "pmsg"
#undef pr_fmt
#define pr_fmt(fmt) PMSG_NAME ": " fmt
static char *pmsg_devnode(struct device *dev, umode_t *mode)
{
if (mode)
*mode = 0220;
return NULL;
}
void pstore_register_pmsg(void)
{
struct device *pmsg_device;
pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
if (pmsg_major < 0) {
pr_err("register_chrdev failed\n");
goto err;
}
pmsg_class = class_create(THIS_MODULE, PMSG_NAME);
if (IS_ERR(pmsg_class)) {
pr_err("device class file already in use\n");
goto err_class;
}
pmsg_class->devnode = pmsg_devnode;
pmsg_device = device_create(pmsg_class, NULL, MKDEV(pmsg_major, 0),
NULL, "%s%d", PMSG_NAME, 0);
if (IS_ERR(pmsg_device)) {
pr_err("failed to create device\n");
goto err_device;
}
return;
err_device:
class_destroy(pmsg_class);
err_class:
unregister_chrdev(pmsg_major, PMSG_NAME);
err:
return;
}
void pstore_unregister_pmsg(void)
{
device_destroy(pmsg_class, MKDEV(pmsg_major, 0));
class_destroy(pmsg_class);
unregister_chrdev(pmsg_major, PMSG_NAME);
}