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>

arch/s390/include/asm/uaccess.h

@@ -377,7 +377,7 @@ clear_user(void __user *to, unsigned long n)
 }
 
 extern int memcpy_real(void *, void *, size_t);
-extern void copy_to_absolute_zero(void *dest, void *src, size_t count);
+extern void memcpy_absolute(void *, void *, size_t);
 extern int copy_to_user_real(void __user *dest, void *src, size_t count);
 extern int copy_from_user_real(void *dest, void __user *src, size_t count);
 

arch/s390/kernel/ipl.c

@@ -1528,12 +1528,15 @@ static struct shutdown_action __refdata dump_action = {
 
 static void dump_reipl_run(struct shutdown_trigger *trigger)
 {
-	u32 csum;
+	struct {
+		void	*addr;
+		__u32	csum;
+	} __packed ipib;
 
-	csum = csum_partial(reipl_block_actual, reipl_block_actual->hdr.len, 0);
-	copy_to_absolute_zero(&S390_lowcore.ipib_checksum, &csum, sizeof(csum));
-	copy_to_absolute_zero(&S390_lowcore.ipib, &reipl_block_actual,
-			      sizeof(reipl_block_actual));
+	ipib.csum = csum_partial(reipl_block_actual,
+				 reipl_block_actual->hdr.len, 0);
+	ipib.addr = reipl_block_actual;
+	memcpy_absolute(&S390_lowcore.ipib, &ipib, sizeof(ipib));
 	dump_run(trigger);
 }
 

arch/s390/kernel/os_info.c

@@ -60,7 +60,7 @@ void __init os_info_init(void)
 	os_info.version_minor = OS_INFO_VERSION_MINOR;
 	os_info.magic = OS_INFO_MAGIC;
 	os_info.csum = os_info_csum(&os_info);
-	copy_to_absolute_zero(&S390_lowcore.os_info, &ptr, sizeof(ptr));
+	memcpy_absolute(&S390_lowcore.os_info, &ptr, sizeof(ptr));
 }
 
 #ifdef CONFIG_CRASH_DUMP

arch/s390/kernel/setup.c

@@ -428,10 +428,12 @@ static void __init setup_lowcore(void)
 	lc->restart_fn = (unsigned long) do_restart;
 	lc->restart_data = 0;
 	lc->restart_source = -1UL;
-	memcpy(&S390_lowcore.restart_stack, &lc->restart_stack,
-	       4*sizeof(unsigned long));
-	copy_to_absolute_zero(&S390_lowcore.restart_psw,
-			      &lc->restart_psw, sizeof(psw_t));
+
+	/* Setup absolute zero lowcore */
+	memcpy_absolute(&S390_lowcore.restart_stack, &lc->restart_stack,
+			4 * sizeof(unsigned long));
+	memcpy_absolute(&S390_lowcore.restart_psw, &lc->restart_psw,
+			sizeof(lc->restart_psw));
 
 	set_prefix((u32)(unsigned long) lc);
 	lowcore_ptr[0] = lc;
@@ -598,7 +600,7 @@ static void __init setup_vmcoreinfo(void)
 #ifdef CONFIG_KEXEC
 	unsigned long ptr = paddr_vmcoreinfo_note();
 
-	copy_to_absolute_zero(&S390_lowcore.vmcore_info, &ptr, sizeof(ptr));
+	memcpy_absolute(&S390_lowcore.vmcore_info, &ptr, sizeof(ptr));
 #endif
 }
 

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);
 }
 
 /*
@@ -187,20 +195,6 @@ static int is_swapped(unsigned long addr)
 	return 0;
 }
 
-/*
- * 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
  *
@@ -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();