v4.19.13 snapshot.
diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
new file mode 100644
index 0000000..7be0647
--- /dev/null
+++ b/arch/s390/mm/maccess.c
@@ -0,0 +1,213 @@
+// 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);
+}