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Add a write operation handler to the sample /dev/crash memory driver

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that enables writing to kernel memory via the "wr" command.
(serapheim@delphix.com)
This commit is contained in:
Dave Anderson 2019-01-07 10:14:45 -05:00
parent 1baaafc0a4
commit dfea9e3bd3
1 changed files with 40 additions and 1 deletions
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41
memory_driver/crash.c
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@ -3,6 +3,7 @@
*
* Copyright (C) 2004, 2011, 2016 Dave Anderson <anderson@redhat.com>
* Copyright (C) 2004, 2011, 2016 Red Hat, Inc.
* Copyright (C) 2019 Serapheim Dimitropoulos <serapheim delphix com>
*/
/******************************************************************************
@ -137,7 +138,7 @@ static inline void unmap_virtual(struct page *page)
#endif
#define CRASH_VERSION "1.3"
#define CRASH_VERSION "1.4"
/*
* These are the file operation functions that allow crash utility
@ -159,6 +160,43 @@ crash_llseek(struct file * file, loff_t offset, int orig)
}
}
static ssize_t
crash_write(struct file *file, const char *buf, size_t count, loff_t *poff)
{
void *vaddr;
struct page *page;
u64 offset;
ssize_t written;
char *buffer = file->private_data;
offset = *poff;
if (offset >> PAGE_SHIFT != (offset+count-1) >> PAGE_SHIFT)
return -EINVAL;
vaddr = map_virtual(offset, &page);
if (!vaddr)
return -EFAULT;
/*
* Use bounce buffer to bypass the CONFIG_HARDENED_USERCOPY
* kernel text restriction.
*/
if (copy_from_user(buffer, buf, count)) {
unmap_virtual(page);
return -EFAULT;
}
if (probe_kernel_write(vaddr, buffer, count)) {
unmap_virtual(page);
return -EFAULT;
}
unmap_virtual(page);
written = count;
*poff += written;
return written;
}
/*
* Determine the page address for an address offset value,
* get a virtual address for it, and copy it out.
@ -256,6 +294,7 @@ static struct file_operations crash_fops = {
.owner = THIS_MODULE,
.llseek = crash_llseek,
.read = crash_read,
.write = crash_write,
.unlocked_ioctl = crash_ioctl,
.open = crash_open,
.release = crash_release,