s390/mm: define Real Memory Copy size and mask macros

Make Real Memory Copy area size and mask explicit.
This does not bring any functional change and only
needed for clarity.

Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Author: Alexander Gordeev

arch/s390/boot/startup.c

@@ -204,7 +204,7 @@ static unsigned long setup_kernel_memory_layout(void)
 	/* force vmalloc and modules below kasan shadow */
 	vmax = min(vmax, KASAN_SHADOW_START);
 #endif
-	__memcpy_real_area = round_down(vmax - PAGE_SIZE, PAGE_SIZE);
+	__memcpy_real_area = round_down(vmax - MEMCPY_REAL_SIZE, PAGE_SIZE);
 	__abs_lowcore = round_down(__memcpy_real_area - ABS_LOWCORE_MAP_SIZE,
 				   sizeof(struct lowcore));
 	MODULES_END = round_down(__abs_lowcore, _SEGMENT_SIZE);

arch/s390/include/asm/maccess.h

@@ -4,6 +4,9 @@
 
 #include <linux/types.h>
 
+#define MEMCPY_REAL_SIZE	PAGE_SIZE
+#define MEMCPY_REAL_MASK	PAGE_MASK
+
 struct iov_iter;
 
 extern unsigned long __memcpy_real_area;

arch/s390/mm/dump_pagetables.c

@@ -297,7 +297,7 @@ static int pt_dump_init(void)
 	address_markers[ABS_LOWCORE_NR].start_address = __abs_lowcore;
 	address_markers[ABS_LOWCORE_END_NR].start_address = __abs_lowcore + ABS_LOWCORE_MAP_SIZE;
 	address_markers[MEMCPY_REAL_NR].start_address = __memcpy_real_area;
-	address_markers[MEMCPY_REAL_END_NR].start_address = __memcpy_real_area + PAGE_SIZE;
+	address_markers[MEMCPY_REAL_END_NR].start_address = __memcpy_real_area + MEMCPY_REAL_SIZE;
 	address_markers[VMEMMAP_NR].start_address = (unsigned long) vmemmap;
 	address_markers[VMEMMAP_END_NR].start_address = (unsigned long)vmemmap + vmemmap_size;
 	address_markers[VMALLOC_NR].start_address = VMALLOC_START;

arch/s390/mm/maccess.c

@@ -86,11 +86,12 @@ size_t memcpy_real_iter(struct iov_iter *iter, unsigned long src, size_t count)
 	void *chunk;
 	pte_t pte;
 
+	BUILD_BUG_ON(MEMCPY_REAL_SIZE != PAGE_SIZE);
 	while (count) {
-		phys = src & PAGE_MASK;
-		offset = src & ~PAGE_MASK;
+		phys = src & MEMCPY_REAL_MASK;
+		offset = src & ~MEMCPY_REAL_MASK;
 		chunk = (void *)(__memcpy_real_area + offset);
-		len = min(count, PAGE_SIZE - offset);
+		len = min(count, MEMCPY_REAL_SIZE - offset);
 		pte = mk_pte_phys(phys, PAGE_KERNEL_RO);
 
 		mutex_lock(&memcpy_real_mutex);