kernel-ark/arch/s390/mm/maccess.c
Michael Holzheu 73bf463efa s390/kernel: Introduce memcpy_absolute() function
This patch introduces the new function memcpy_absolute() that allows to
copy memory using absolute addressing. This means that the prefix swap
does not apply when this function is used.

With this patch also all s390 kernel code that accesses absolute zero
now uses the new memcpy_absolute() function. The old and less generic
copy_to_absolute_zero() function is removed.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2012-05-30 09:04:49 +02:00

230 lines
5.0 KiB
C

/*
* Access kernel memory without faulting -- s390 specific implementation.
*
* Copyright IBM Corp. 2009
*
* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
*
*/
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/cpu.h>
#include <asm/ctl_reg.h>
/*
* This function writes to kernel memory bypassing DAT and possible
* write protection. It copies one to four bytes from src to dst
* using the stura instruction.
* Returns the number of bytes copied or -EFAULT.
*/
static long probe_kernel_write_odd(void *dst, const void *src, size_t size)
{
unsigned long count, aligned;
int offset, mask;
int rc = -EFAULT;
aligned = (unsigned long) dst & ~3UL;
offset = (unsigned long) dst & 3;
count = min_t(unsigned long, 4 - offset, size);
mask = (0xf << (4 - count)) & 0xf;
mask >>= offset;
asm volatile(
" bras 1,0f\n"
" icm 0,0,0(%3)\n"
"0: l 0,0(%1)\n"
" lra %1,0(%1)\n"
"1: ex %2,0(1)\n"
"2: stura 0,%1\n"
" la %0,0\n"
"3:\n"
EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b)
: "+d" (rc), "+a" (aligned)
: "a" (mask), "a" (src) : "cc", "memory", "0", "1");
return rc ? rc : count;
}
long probe_kernel_write(void *dst, const void *src, size_t size)
{
long copied = 0;
while (size) {
copied = probe_kernel_write_odd(dst, src, size);
if (copied < 0)
break;
dst += copied;
src += copied;
size -= copied;
}
return copied < 0 ? -EFAULT : 0;
}
static int __memcpy_real(void *dest, void *src, size_t count)
{
register unsigned long _dest asm("2") = (unsigned long) dest;
register unsigned long _len1 asm("3") = (unsigned long) count;
register unsigned long _src asm("4") = (unsigned long) src;
register unsigned long _len2 asm("5") = (unsigned long) count;
int rc = -EFAULT;
asm volatile (
"0: mvcle %1,%2,0x0\n"
"1: jo 0b\n"
" lhi %0,0x0\n"
"2:\n"
EX_TABLE(1b,2b)
: "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
"+d" (_len2), "=m" (*((long *) dest))
: "m" (*((long *) src))
: "cc", "memory");
return rc;
}
/*
* Copy memory in real mode (kernel to kernel)
*/
int memcpy_real(void *dest, void *src, size_t count)
{
unsigned long flags;
int rc;
if (!count)
return 0;
local_irq_save(flags);
__arch_local_irq_stnsm(0xfbUL);
rc = __memcpy_real(dest, src, count);
local_irq_restore(flags);
return rc;
}
/*
* Copy memory in absolute mode (kernel to kernel)
*/
void memcpy_absolute(void *dest, void *src, size_t count)
{
unsigned long cr0, flags, prefix;
flags = arch_local_irq_save();
__ctl_store(cr0, 0, 0);
__ctl_clear_bit(0, 28); /* disable lowcore protection */
prefix = store_prefix();
if (prefix) {
local_mcck_disable();
set_prefix(0);
memcpy(dest, src, count);
set_prefix(prefix);
local_mcck_enable();
} else {
memcpy(dest, src, count);
}
__ctl_load(cr0, 0, 0);
arch_local_irq_restore(flags);
}
/*
* Copy memory from kernel (real) to user (virtual)
*/
int copy_to_user_real(void __user *dest, void *src, size_t count)
{
int offs = 0, size, rc;
char *buf;
buf = (char *) __get_free_page(GFP_KERNEL);
if (!buf)
return -ENOMEM;
rc = -EFAULT;
while (offs < count) {
size = min(PAGE_SIZE, count - offs);
if (memcpy_real(buf, src + offs, size))
goto out;
if (copy_to_user(dest + offs, buf, size))
goto out;
offs += size;
}
rc = 0;
out:
free_page((unsigned long) buf);
return rc;
}
/*
* Copy memory from user (virtual) to kernel (real)
*/
int copy_from_user_real(void *dest, void __user *src, size_t count)
{
int offs = 0, size, rc;
char *buf;
buf = (char *) __get_free_page(GFP_KERNEL);
if (!buf)
return -ENOMEM;
rc = -EFAULT;
while (offs < count) {
size = min(PAGE_SIZE, count - offs);
if (copy_from_user(buf, src + offs, size))
goto out;
if (memcpy_real(dest + offs, buf, size))
goto out;
offs += size;
}
rc = 0;
out:
free_page((unsigned long) buf);
return rc;
}
/*
* Check if physical address is within prefix or zero page
*/
static int is_swapped(unsigned long addr)
{
unsigned long lc;
int cpu;
if (addr < sizeof(struct _lowcore))
return 1;
for_each_online_cpu(cpu) {
lc = (unsigned long) lowcore_ptr[cpu];
if (addr > lc + sizeof(struct _lowcore) - 1 || addr < lc)
continue;
return 1;
}
return 0;
}
/*
* Convert a physical pointer for /dev/mem access
*
* For swapped prefix pages a new buffer is returned that contains a copy of
* the absolute memory. The buffer size is maximum one page large.
*/
void *xlate_dev_mem_ptr(unsigned long addr)
{
void *bounce = (void *) addr;
unsigned long size;
get_online_cpus();
preempt_disable();
if (is_swapped(addr)) {
size = PAGE_SIZE - (addr & ~PAGE_MASK);
bounce = (void *) __get_free_page(GFP_ATOMIC);
if (bounce)
memcpy_absolute(bounce, (void *) addr, size);
}
preempt_enable();
put_online_cpus();
return bounce;
}
/*
* Free converted buffer for /dev/mem access (if necessary)
*/
void unxlate_dev_mem_ptr(unsigned long addr, void *buf)
{
if ((void *) addr != buf)
free_page((unsigned long) buf);
}