From cd62c27097720adf1c7bb099a011ebd079a88aa5 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Fri, 12 Jun 2009 10:26:42 +0200
Subject: [PATCH] --- yaml --- r: 148775 b: refs/heads/master c:
 88df125fd6127e409793fd84a574566651450320 h: refs/heads/master i:   148773:
 34f0fc51420b9f23befb33830c2817610ab4d2a1   148771:
 f74662f4284fb15b4ff62f68c64a20d281107683   148767:
 7fafd312aa0aa7ba1f1644e574d3a21dd4622b7b v: v3

---
 [refs]                       |  2 +-
 trunk/arch/s390/mm/Makefile  |  2 +-
 trunk/arch/s390/mm/maccess.c | 61 ++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 2 deletions(-)
 create mode 100644 trunk/arch/s390/mm/maccess.c

diff --git a/[refs] b/[refs]
index 33613f38df5b..d17502131d9f 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: d93f82b6e0c12a4373f2d04b1f92fcb2d175b62c
+refs/heads/master: 88df125fd6127e409793fd84a574566651450320
diff --git a/trunk/arch/s390/mm/Makefile b/trunk/arch/s390/mm/Makefile
index 2a7458134544..db05661ac895 100644
--- a/trunk/arch/s390/mm/Makefile
+++ b/trunk/arch/s390/mm/Makefile
@@ -2,7 +2,7 @@
 # Makefile for the linux s390-specific parts of the memory manager.
 #
 
-obj-y	 := init.o fault.o extmem.o mmap.o vmem.o pgtable.o
+obj-y	 := init.o fault.o extmem.o mmap.o vmem.o pgtable.o maccess.o
 obj-$(CONFIG_CMM) += cmm.o
 obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
 obj-$(CONFIG_PAGE_STATES) += page-states.o
diff --git a/trunk/arch/s390/mm/maccess.c b/trunk/arch/s390/mm/maccess.c
new file mode 100644
index 000000000000..81756271dc44
--- /dev/null
+++ b/trunk/arch/s390/mm/maccess.c
@@ -0,0 +1,61 @@
+/*
+ * Access kernel memory without faulting -- s390 specific implementation.
+ *
+ * Copyright IBM Corp. 2009
+ *
+ *   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 <asm/system.h>
+
+/*
+ * This function writes to kernel memory bypassing DAT and possible
+ * write protection. It copies one to four bytes from src to dst
+ * using the stura instruction.
+ * Returns the number of bytes copied or -EFAULT.
+ */
+static long probe_kernel_write_odd(void *dst, void *src, size_t size)
+{
+	unsigned long count, aligned;
+	int offset, mask;
+	int rc = -EFAULT;
+
+	aligned = (unsigned long) dst & ~3UL;
+	offset = (unsigned long) dst & 3;
+	count = min_t(unsigned long, 4 - offset, size);
+	mask = (0xf << (4 - count)) & 0xf;
+	mask >>= offset;
+	asm volatile(
+		"	bras	1,0f\n"
+		"	icm	0,0,0(%3)\n"
+		"0:	l	0,0(%1)\n"
+		"	lra	%1,0(%1)\n"
+		"1:	ex	%2,0(1)\n"
+		"2:	stura	0,%1\n"
+		"	la	%0,0\n"
+		"3:\n"
+		EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b)
+		: "+d" (rc), "+a" (aligned)
+		: "a" (mask), "a" (src) : "cc", "memory", "0", "1");
+	return rc ? rc : count;
+}
+
+long probe_kernel_write(void *dst, void *src, size_t size)
+{
+	long copied = 0;
+
+	while (size) {
+		copied = probe_kernel_write_odd(dst, src, size);
+		if (copied < 0)
+			break;
+		dst += copied;
+		src += copied;
+		size -= copied;
+	}
+	return copied < 0 ? -EFAULT : 0;
+}