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// SPDX-License-Identifier: GPL-2.0
/*
* Access kernel memory without faulting -- s390 specific implementation.
*
* Copyright IBM Corp. 2009, 2015
*
*/
#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 <linux/uio.h>
#include <linux/io.h>
#include <asm/asm-extable.h>
#include <asm/ctl_reg.h>
#include <asm/abs_lowcore.h>
#include <asm/stacktrace.h>
#include <asm/maccess.h>
unsigned long __bootdata_preserved(__memcpy_real_area);
pte_t *__bootdata_preserved(memcpy_real_ptep);
static DEFINE_MUTEX(memcpy_real_mutex);
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.
*/
static DEFINE_SPINLOCK(s390_kernel_write_lock);
notrace void *s390_kernel_write(void *dst, const void *src, size_t size)
{
void *tmp = dst;
unsigned long flags;
long copied;
spin_lock_irqsave(&s390_kernel_write_lock, flags);
while (size) {
copied = s390_kernel_write_odd(tmp, src, size);
tmp += copied;
src += copied;
size -= copied;
}
spin_unlock_irqrestore(&s390_kernel_write_lock, flags);
return dst;
}
size_t memcpy_real_iter(struct iov_iter *iter, unsigned long src, size_t count)
{
size_t len, copied, res = 0;
unsigned long phys, offset;
void *chunk;
pte_t pte;
while (count) {
phys = src & PAGE_MASK;
offset = src & ~PAGE_MASK;
chunk = (void *)(__memcpy_real_area + offset);
len = min(count, PAGE_SIZE - offset);
pte = mk_pte_phys(phys, PAGE_KERNEL_RO);
mutex_lock(&memcpy_real_mutex);
if (pte_val(pte) != pte_val(*memcpy_real_ptep)) {
__ptep_ipte(__memcpy_real_area, memcpy_real_ptep, 0, 0, IPTE_GLOBAL);
set_pte(memcpy_real_ptep, pte);
}
copied = copy_to_iter(chunk, len, iter);
mutex_unlock(&memcpy_real_mutex);
count -= copied;
src += copied;
res += copied;
if (copied < len)
break;
}
return res;
}
int memcpy_real(void *dest, unsigned long src, size_t count)
{
struct iov_iter iter;
struct kvec kvec;
kvec.iov_base = dest;
kvec.iov_len = count;
iov_iter_kvec(&iter, ITER_DEST, &kvec, 1, count);
if (memcpy_real_iter(&iter, src, count) < count)
return -EFAULT;
return 0;
}
/*
* Find CPU that owns swapped prefix page
*/
static int get_swapped_owner(phys_addr_t addr)
{
phys_addr_t lc;
int cpu;
for_each_online_cpu(cpu) {
lc = virt_to_phys(lowcore_ptr[cpu]);
if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
continue;
return cpu;
}
return -1;
}
/*
* 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 *ptr = phys_to_virt(addr);
void *bounce = ptr;
struct lowcore *abs_lc;
unsigned long size;
int this_cpu, cpu;
cpus_read_lock();
this_cpu = get_cpu();
if (addr >= sizeof(struct lowcore)) {
cpu = get_swapped_owner(addr);
if (cpu < 0)
goto out;
}
bounce = (void *)__get_free_page(GFP_ATOMIC);
if (!bounce)
goto out;
size = PAGE_SIZE - (addr & ~PAGE_MASK);
if (addr < sizeof(struct lowcore)) {
abs_lc = get_abs_lowcore();
ptr = (void *)abs_lc + addr;
memcpy(bounce, ptr, size);
put_abs_lowcore(abs_lc);
} else if (cpu == this_cpu) {
ptr = (void *)(addr - virt_to_phys(lowcore_ptr[cpu]));
memcpy(bounce, ptr, size);
} else {
memcpy(bounce, ptr, size);
}
out:
put_cpu();
cpus_read_unlock();
return bounce;
}
/*
* Free converted buffer for /dev/mem access (if necessary)
*/
void unxlate_dev_mem_ptr(phys_addr_t addr, void *ptr)
{
if (addr != virt_to_phys(ptr))
free_page((unsigned long)ptr);
}
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