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// SPDX-License-Identifier: GPL-2.0
/*
* Access kernel memory without faulting -- s390 specific implementation.
*
* Copyright IBM Corp. 2009, 2015
*
* 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>
#include <asm/io.h>
static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
{
unsigned long aligned, offset, count;
char tmp[8];
aligned = (unsigned long) dst & ~7UL;
offset = (unsigned long) dst & 7UL;
size = min(8UL - offset, size);
count = size - 1;
asm volatile(
" bras 1,0f\n"
" mvc 0(1,%4),0(%5)\n"
"0: mvc 0(8,%3),0(%0)\n"
" ex %1,0(1)\n"
" lg %1,0(%3)\n"
" lra %0,0(%0)\n"
" sturg %1,%0\n"
: "+&a" (aligned), "+&a" (count), "=m" (tmp)
: "a" (&tmp), "a" (&tmp[offset]), "a" (src)
: "cc", "memory", "1");
return size;
}
/*
* s390_kernel_write - write to kernel memory bypassing DAT
* @dst: destination address
* @src: source address
* @size: number of bytes to copy
*
* This function writes to kernel memory bypassing DAT and possible page table
* write protection. It writes to the destination using the sturg instruction.
* Therefore we have a read-modify-write sequence: the function reads eight
* bytes from destination at an eight byte boundary, modifies the bytes
* requested and writes the result back in a loop.
*
* Note: this means that this function may not be called concurrently on
* several cpus with overlapping words, since this may potentially
* cause data corruption.
*/
void notrace s390_kernel_write(void *dst, const void *src, size_t size)
{
long copied;
while (size) {
copied = s390_kernel_write_odd(dst, src, size);
dst += copied;
src += copied;
size -= copied;
}
}
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)
{
int irqs_disabled, rc;
unsigned long flags;
if (!count)
return 0;
flags = __arch_local_irq_stnsm(0xf8UL);
irqs_disabled = arch_irqs_disabled_flags(flags);
if (!irqs_disabled)
trace_hardirqs_off();
rc = __memcpy_real(dest, src, count);
if (!irqs_disabled)
trace_hardirqs_on();
__arch_local_irq_ssm(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, unsigned long 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;
}
/*
* 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(phys_addr_t 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(phys_addr_t addr, void *buf)
{
if ((void *) addr != buf)
free_page((unsigned long) buf);
}
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