[S390] Add real memory access functions

Add access function for real memory needed by s390 kdump backend.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 58 insertions, 0 deletions

diff --git a/arch/s390/include/asm/system.h b/arch/s390/include/asm/system.h
index 6582f69f2389..afb849e4bf4b 100644
--- a/arch/s390/include/asm/system.h
+++ b/arch/s390/include/asm/system.h
@@ -114,6 +114,8 @@ extern void pfault_fini(void);
 extern void cmma_init(void);
 extern int memcpy_real(void *, void *, size_t);
 extern void copy_to_absolute_zero(void *dest, void *src, size_t count);
+extern int copy_to_user_real(void __user *dest, void *src, size_t count);
+extern int copy_from_user_real(void *dest, void __user *src, size_t count);
 
 #define finish_arch_switch(prev) do {					     \
 	set_fs(current->thread.mm_segment);				     \
diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
index 5dbbaa6e594c..1cb8427bedfb 100644
--- a/arch/s390/mm/maccess.c
+++ b/arch/s390/mm/maccess.c
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/types.h>
 #include <linux/errno.h>
+#include <linux/gfp.h>
 #include <asm/system.h>
 
 /*
@@ -60,6 +61,9 @@ long probe_kernel_write(void *dst, const void *src, size_t size)
 	return copied < 0 ? -EFAULT : 0;
 }
 
+/*
+ * Copy memory in real mode (kernel to kernel)
+ */
 int memcpy_real(void *dest, void *src, size_t count)
 {
 	register unsigned long _dest asm("2") = (unsigned long) dest;
@@ -101,3 +105,55 @@ void copy_to_absolute_zero(void *dest, void *src, size_t count)
 	__ctl_load(cr0, 0, 0);
 	preempt_enable();
 }
+
+/*
+ * 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;
+}