9d5438f462
A secured user-space accessible pstore object. Writes to /dev/pmsg0 are appended to the buffer, on reboot the persistent contents are available in /sys/fs/pstore/pmsg-ramoops-[ID]. One possible use is syslogd, or other daemon, can write messages, then on reboot provides a means to triage user-space activities leading up to a panic as a companion to the pstore dmesg or console logs. Signed-off-by: Mark Salyzyn <salyzyn@android.com> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Tony Luck <tony.luck@intel.com>
114 lines
2.5 KiB
C
114 lines
2.5 KiB
C
/*
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* Copyright 2014 Google, Inc.
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*
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* This software is licensed under the terms of the GNU General Public
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* License version 2, as published by the Free Software Foundation, and
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* may be copied, distributed, and modified under those terms.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/cdev.h>
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#include <linux/device.h>
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#include <linux/fs.h>
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#include <linux/uaccess.h>
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#include <linux/vmalloc.h>
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#include "internal.h"
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static DEFINE_MUTEX(pmsg_lock);
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#define PMSG_MAX_BOUNCE_BUFFER_SIZE (2*PAGE_SIZE)
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static ssize_t write_pmsg(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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size_t i, buffer_size;
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char *buffer;
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if (!count)
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return 0;
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if (!access_ok(VERIFY_READ, buf, count))
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return -EFAULT;
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buffer_size = count;
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if (buffer_size > PMSG_MAX_BOUNCE_BUFFER_SIZE)
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buffer_size = PMSG_MAX_BOUNCE_BUFFER_SIZE;
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buffer = vmalloc(buffer_size);
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mutex_lock(&pmsg_lock);
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for (i = 0; i < count; ) {
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size_t c = min(count - i, buffer_size);
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u64 id;
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long ret;
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ret = __copy_from_user(buffer, buf + i, c);
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if (unlikely(ret != 0)) {
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mutex_unlock(&pmsg_lock);
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vfree(buffer);
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return -EFAULT;
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}
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psinfo->write_buf(PSTORE_TYPE_PMSG, 0, &id, 0, buffer, 0, c,
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psinfo);
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i += c;
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}
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mutex_unlock(&pmsg_lock);
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vfree(buffer);
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return count;
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}
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static const struct file_operations pmsg_fops = {
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.owner = THIS_MODULE,
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.llseek = noop_llseek,
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.write = write_pmsg,
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};
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static struct class *pmsg_class;
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static int pmsg_major;
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#define PMSG_NAME "pmsg"
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#undef pr_fmt
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#define pr_fmt(fmt) PMSG_NAME ": " fmt
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static char *pmsg_devnode(struct device *dev, umode_t *mode)
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{
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if (mode)
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*mode = 0220;
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return NULL;
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}
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void pstore_register_pmsg(void)
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{
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struct device *pmsg_device;
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pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
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if (pmsg_major < 0) {
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pr_err("register_chrdev failed\n");
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goto err;
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}
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pmsg_class = class_create(THIS_MODULE, PMSG_NAME);
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if (IS_ERR(pmsg_class)) {
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pr_err("device class file already in use\n");
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goto err_class;
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}
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pmsg_class->devnode = pmsg_devnode;
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pmsg_device = device_create(pmsg_class, NULL, MKDEV(pmsg_major, 0),
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NULL, "%s%d", PMSG_NAME, 0);
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if (IS_ERR(pmsg_device)) {
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pr_err("failed to create device\n");
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goto err_device;
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}
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return;
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err_device:
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class_destroy(pmsg_class);
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err_class:
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unregister_chrdev(pmsg_major, PMSG_NAME);
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err:
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return;
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}
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