linux/arch/sparc64/lib/user_fixup.c
David S. Miller efdc1e2083 [SPARC64]: Simplify user fault fixup handling.
Instead of doing byte-at-a-time user accesses to figure
out where the fault occurred, read the saved fault_address
from the current thread structure.

For the sake of defensive programming, if the fault_address
does not fall into the user buffer range, simply assume the
whole area faulted.  This will cause the fixup for
copy_from_user() to clear the entire kernel side buffer.

Signed-off-by: David S. Miller <davem@davemloft.net>
2005-09-28 21:06:47 -07:00

67 lines
1.6 KiB
C

/* user_fixup.c: Fix up user copy faults.
*
* Copyright (C) 2004 David S. Miller <davem@redhat.com>
*/
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <asm/uaccess.h>
/* Calculating the exact fault address when using
* block loads and stores can be very complicated.
*
* Instead of trying to be clever and handling all
* of the cases, just fix things up simply here.
*/
static unsigned long compute_size(unsigned long start, unsigned long size, unsigned long *offset)
{
unsigned long fault_addr = current_thread_info()->fault_address;
unsigned long end = start + size;
if (fault_addr < start || fault_addr >= end) {
*offset = 0;
} else {
*offset = start - fault_addr;
size = end - fault_addr;
}
return size;
}
unsigned long copy_from_user_fixup(void *to, const void __user *from, unsigned long size)
{
unsigned long offset;
size = compute_size((unsigned long) from, size, &offset);
if (likely(size))
memset(to + offset, 0, size);
return size;
}
unsigned long copy_to_user_fixup(void __user *to, const void *from, unsigned long size)
{
unsigned long offset;
return compute_size((unsigned long) to, size, &offset);
}
unsigned long copy_in_user_fixup(void __user *to, void __user *from, unsigned long size)
{
unsigned long fault_addr = current_thread_info()->fault_address;
unsigned long start = (unsigned long) to;
unsigned long end = start + size;
if (fault_addr >= start && fault_addr < end)
return end - fault_addr;
start = (unsigned long) from;
end = start + size;
if (fault_addr >= start && fault_addr < end)
return end - fault_addr;
return size;
}