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pstore: Add pmsg - user-space accessible pstore object
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 <[email protected]> Acked-by: Kees Cook <[email protected]> Signed-off-by: Tony Luck <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,114 @@ | ||
| /* | ||
| * 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); | ||
| #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, | ||
| size_t count, loff_t *ppos) | ||
| { | ||
| size_t i, buffer_size; | ||
| char *buffer; | ||
|
|
||
| if (!count) | ||
| return 0; | ||
|
|
||
| if (!access_ok(VERIFY_READ, buf, count)) | ||
| return -EFAULT; | ||
|
|
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| buffer_size = count; | ||
| if (buffer_size > PMSG_MAX_BOUNCE_BUFFER_SIZE) | ||
| buffer_size = PMSG_MAX_BOUNCE_BUFFER_SIZE; | ||
| buffer = vmalloc(buffer_size); | ||
|
|
||
| mutex_lock(&pmsg_lock); | ||
| for (i = 0; i < count; ) { | ||
| size_t c = min(count - i, buffer_size); | ||
| u64 id; | ||
| long ret; | ||
|
|
||
| ret = __copy_from_user(buffer, buf + i, c); | ||
| if (unlikely(ret != 0)) { | ||
| mutex_unlock(&pmsg_lock); | ||
| vfree(buffer); | ||
| return -EFAULT; | ||
| } | ||
| psinfo->write_buf(PSTORE_TYPE_PMSG, 0, &id, 0, buffer, 0, c, | ||
| psinfo); | ||
|
|
||
| i += c; | ||
| } | ||
|
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| mutex_unlock(&pmsg_lock); | ||
| vfree(buffer); | ||
| return count; | ||
| } | ||
|
|
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| 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; | ||
|
|
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| pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops); | ||
| if (pmsg_major < 0) { | ||
| pr_err("register_chrdev failed\n"); | ||
| goto err; | ||
| } | ||
|
|
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| 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; | ||
|
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||
| 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; | ||
| } |
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