1 files changed, 247 insertions, 0 deletions
diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
new file mode 100644
index 000000000..1d17413b3
--- /dev/null
+++ b/arch/s390/mm/maccess.c
@@ -0,0 +1,247 @@
+// 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>
+#include <asm/stacktrace.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.
+ */
+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);
+	if (!(flags & PSW_MASK_DAT)) {
+		memcpy(dst, src, size);
+	} else {
+		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;
+}
+
+static int __no_sanitize_address __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;
+}
+
+static unsigned long __no_sanitize_address _memcpy_real(unsigned long dest,
+							unsigned long src,
+							unsigned long count)
+{
+	int irqs_disabled, rc;
+	unsigned long flags;
+
+	if (!count)
+		return 0;
+	flags = arch_local_irq_save();
+	irqs_disabled = arch_irqs_disabled_flags(flags);
+	if (!irqs_disabled)
+		trace_hardirqs_off();
+	__arch_local_irq_stnsm(0xf8); // disable DAT
+	rc = __memcpy_real((void *) dest, (void *) src, (size_t) count);
+	if (flags & PSW_MASK_DAT)
+		__arch_local_irq_stosm(0x04); // enable DAT
+	if (!irqs_disabled)
+		trace_hardirqs_on();
+	__arch_local_irq_ssm(flags);
+	return rc;
+}
+
+/*
+ * Copy memory in real mode (kernel to kernel)
+ */
+int memcpy_real(void *dest, void *src, size_t count)
+{
+	int rc;
+
+	if (S390_lowcore.nodat_stack != 0) {
+		preempt_disable();
+		rc = CALL_ON_STACK(_memcpy_real, S390_lowcore.nodat_stack, 3,
+				   dest, src, count);
+		preempt_enable();
+		return rc;
+	}
+	/*
+	 * This is a really early memcpy_real call, the stacks are
+	 * not set up yet. Just call _memcpy_real on the early boot
+	 * stack
+	 */
+	return _memcpy_real((unsigned long) dest,(unsigned long) src,
+			    (unsigned long) count);
+}
+
+/*
+ * 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);
+}