s390/kernel: Introduce memcpy_absolute() function

This patch introduces the new function memcpy_absolute() that allows to
copy memory using absolute addressing. This means that the prefix swap
does not apply when this function is used.

With this patch also all s390 kernel code that accesses absolute zero
now uses the new memcpy_absolute() function. The old and less generic
copy_to_absolute_zero() function is removed.

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

1 files changed, 16 insertions, 22 deletions

diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
index 795a0a9bb2e..921fa541dc0 100644
--- a/arch/s390/mm/maccess.c
+++ b/arch/s390/mm/maccess.c
@@ -101,19 +101,27 @@ int memcpy_real(void *dest, void *src, size_t count)
 }
 
 /*
- * Copy memory to absolute zero
+ * Copy memory in absolute mode (kernel to kernel)
  */
-void copy_to_absolute_zero(void *dest, void *src, size_t count)
+void memcpy_absolute(void *dest, void *src, size_t count)
 {
-	unsigned long cr0;
+	unsigned long cr0, flags, prefix;
 
-	BUG_ON((unsigned long) dest + count >= sizeof(struct _lowcore));
-	preempt_disable();
+	flags = arch_local_irq_save();
 	__ctl_store(cr0, 0, 0);
 	__ctl_clear_bit(0, 28); /* disable lowcore protection */
-	memcpy_real(dest + store_prefix(), src, count);
+	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);
-	preempt_enable();
+	arch_local_irq_restore(flags);
 }
 
 /*
@@ -188,20 +196,6 @@ static int is_swapped(unsigned long addr)
 }
 
 /*
- * Return swapped prefix or zero page address
- */
-static unsigned long get_swapped(unsigned long addr)
-{
-	unsigned long prefix = store_prefix();
-
-	if (addr < sizeof(struct _lowcore))
-		return addr + prefix;
-	if (addr >= prefix && addr < prefix + sizeof(struct _lowcore))
-		return addr - prefix;
-	return addr;
-}
-
-/*
  * Convert a physical pointer for /dev/mem access
  *
  * For swapped prefix pages a new buffer is returned that contains a copy of
@@ -218,7 +212,7 @@ void *xlate_dev_mem_ptr(unsigned long addr)
 		size = PAGE_SIZE - (addr & ~PAGE_MASK);
 		bounce = (void *) __get_free_page(GFP_ATOMIC);
 		if (bounce)
-			memcpy_real(bounce, (void *) get_swapped(addr), size);
+			memcpy_absolute(bounce, (void *) addr, size);
 	}
 	preempt_enable();
 	put_online_cpus();