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Diffstat (limited to 'arch/s390/mm/maccess.c')
-rw-r--r--arch/s390/mm/maccess.c70
1 files changed, 37 insertions, 33 deletions
diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
index 2eb34bdfc613..8a993a53fcd6 100644
--- a/arch/s390/mm/maccess.c
+++ b/arch/s390/mm/maccess.c
@@ -1,7 +1,7 @@
/*
* Access kernel memory without faulting -- s390 specific implementation.
*
- * Copyright IBM Corp. 2009
+ * Copyright IBM Corp. 2009, 2015
*
* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
*
@@ -16,51 +16,55 @@
#include <asm/ctl_reg.h>
#include <asm/io.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, const void *src, size_t size)
+static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
{
- unsigned long count, aligned;
- int offset, mask;
- int rc = -EFAULT;
+ unsigned long aligned, offset, count;
+ char tmp[8];
- 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;
+ aligned = (unsigned long) dst & ~7UL;
+ offset = (unsigned long) dst & 7UL;
+ size = min(8UL - offset, size);
+ count = size - 1;
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;
+ " 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;
}
-long probe_kernel_write(void *dst, const void *src, size_t 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 = 0;
+ long copied;
while (size) {
- copied = probe_kernel_write_odd(dst, src, size);
- if (copied < 0)
- break;
+ copied = s390_kernel_write_odd(dst, src, size);
dst += copied;
src += copied;
size -= copied;
}
- return copied < 0 ? -EFAULT : 0;
}
static int __memcpy_real(void *dest, void *src, size_t count)