s390/kdump: Allow copy_oldmem_page() copy to virtual memory

The kdump mmap patch series (git commit 83086978c63afd7c73e1c) changed the
requirements for copy_oldmem_page(). Now this function is used for copying
to virtual memory.

So implement vmalloc support for the s390 version of copy_oldmem_page().

Signed-off-by: Michael Holzheu <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/kernel/crash_dump.c

···
 #define PTR_SUB(x, y) (((char *) (x)) - ((unsigned long) (y)))
 #define PTR_DIFF(x, y) ((unsigned long)(((char *) (x)) - ((unsigned long) (y))))
 
+
+/*
+ * Return physical address for virtual address
+ */
+static inline void *load_real_addr(void *addr)
+{
+	unsigned long real_addr;
+
+	asm volatile(
+		   "	lra     %0,0(%1)\n"
+		   "	jz	0f\n"
+		   "	la	%0,0\n"
+		   "0:"
+		   : "=a" (real_addr) : "a" (addr) : "cc");
+	return (void *)real_addr;
+}
+
+/*
+ * Copy up to one page to vmalloc or real memory
+ */
+static ssize_t copy_page_real(void *buf, void *src, size_t csize)
+{
+	size_t size;
+
+	if (is_vmalloc_addr(buf)) {
+		BUG_ON(csize >= PAGE_SIZE);
+		/* If buf is not page aligned, copy first part */
+		size = min(roundup(__pa(buf), PAGE_SIZE) - __pa(buf), csize);
+		if (size) {
+			if (memcpy_real(load_real_addr(buf), src, size))
+				return -EFAULT;
+			buf += size;
+			src += size;
+		}
+		/* Copy second part */
+		size = csize - size;
+		return (size) ? memcpy_real(load_real_addr(buf), src, size) : 0;
+	} else {
+		return memcpy_real(buf, src, csize);
+	}
+}
+
 /*
  * Copy one page from "oldmem"
  *
···
 			 size_t csize, unsigned long offset, int userbuf)
 {
 	unsigned long src;
+	int rc;
 
 	if (!csize)
 		return 0;
···
 		 src < OLDMEM_BASE + OLDMEM_SIZE)
 		src -= OLDMEM_BASE;
 	if (userbuf)
-		copy_to_user_real((void __force __user *) buf, (void *) src,
-				  csize);
+		rc = copy_to_user_real((void __force __user *) buf,
+				       (void *) src, csize);
 	else
-		memcpy_real(buf, (void *) src, csize);
-	return csize;
+		rc = copy_page_real(buf, (void *) src, csize);
+	return (rc == 0) ? csize : rc;
 }
 
 /*