Viewing file:  ia32_ldt.c (3.47 KB) -rw-r--r--
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/*
* Copyright (C) 2001 Hewlett-Packard Co
* David Mosberger-Tang <davidm@hpl.hp.com>
*
* Adapted from arch/i386/kernel/ldt.c
*/
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/vmalloc.h>
#include <asm/uaccess.h>
#include <asm/ia32.h>
#define P(p) ((void *) (unsigned long) (p))
/*
* read_ldt() is not really atomic - this is not a problem since synchronization of reads
* and writes done to the LDT has to be assured by user-space anyway. Writes are atomic,
* to protect the security checks done on new descriptors.
*/
static int
read_ldt (void *ptr, unsigned long bytecount)
{
char *src, *dst, buf[256]; /* temporary buffer (don't overflow kernel stack!) */
unsigned long bytes_left, n;
if (bytecount > IA32_LDT_ENTRIES*IA32_LDT_ENTRY_SIZE)
bytecount = IA32_LDT_ENTRIES*IA32_LDT_ENTRY_SIZE;
bytes_left = bytecount;
src = (void *) IA32_LDT_OFFSET;
dst = ptr;
while (bytes_left) {
n = sizeof(buf);
if (n > bytes_left)
n = bytes_left;
/*
* We know we're reading valid memory, but we still must guard against
* running out of memory.
*/
if (__copy_from_user(buf, src, n))
return -EFAULT;
if (copy_to_user(dst, buf, n))
return -EFAULT;
src += n;
dst += n;
bytes_left -= n;
}
return bytecount;
}
static int
read_default_ldt (void * ptr, unsigned long bytecount)
{
unsigned long size;
int err;
/* XXX fix me: should return equivalent of default_ldt[0] */
err = 0;
size = 8;
if (size > bytecount)
size = bytecount;
err = size;
if (clear_user(ptr, size))
err = -EFAULT;
return err;
}
static int
write_ldt (void * ptr, unsigned long bytecount, int oldmode)
{
struct ia32_modify_ldt_ldt_s ldt_info;
__u64 entry;
int ret;
if (bytecount != sizeof(ldt_info))
return -EINVAL;
if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
return -EFAULT;
if (ldt_info.entry_number >= IA32_LDT_ENTRIES)
return -EINVAL;
if (ldt_info.contents == 3) {
if (oldmode)
return -EINVAL;
if (ldt_info.seg_not_present == 0)
return -EINVAL;
}
if (ldt_info.base_addr == 0 && ldt_info.limit == 0
&& (oldmode || (ldt_info.contents == 0 && ldt_info.read_exec_only == 1
&& ldt_info.seg_32bit == 0 && ldt_info.limit_in_pages == 0
&& ldt_info.seg_not_present == 1 && ldt_info.useable == 0)))
/* allow LDTs to be cleared by the user */
entry = 0;
else
/* we must set the "Accessed" bit as IVE doesn't emulate it */
entry = IA32_SEG_DESCRIPTOR(ldt_info.base_addr, ldt_info.limit,
(((ldt_info.read_exec_only ^ 1) << 1)
| (ldt_info.contents << 2)) | 1,
1, 3, ldt_info.seg_not_present ^ 1,
(oldmode ? 0 : ldt_info.useable),
ldt_info.seg_32bit,
ldt_info.limit_in_pages);
/*
* Install the new entry. We know we're accessing valid (mapped) user-level
* memory, but we still need to guard against out-of-memory, hence we must use
* put_user().
*/
ret = __put_user(entry, (__u64 *) IA32_LDT_OFFSET + ldt_info.entry_number);
ia32_load_segment_descriptors(current);
return ret;
}
asmlinkage int
sys32_modify_ldt (int func, unsigned int ptr, unsigned int bytecount)
{
int ret = -ENOSYS;
switch (func) {
case 0:
ret = read_ldt(P(ptr), bytecount);
break;
case 1:
ret = write_ldt(P(ptr), bytecount, 1);
break;
case 2:
ret = read_default_ldt(P(ptr), bytecount);
break;
case 0x11:
ret = write_ldt(P(ptr), bytecount, 0);
break;
}
return ret;
}
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