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-rw-r--r--arch/s390/mm/maccess.c61
1 files changed, 61 insertions, 0 deletions
diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
new file mode 100644
index 000000000000..81756271dc44
--- /dev/null
+++ b/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;
+}