s390/smp: make absolute lowcore / cpu restart parameter accesses more robust

Setting the cpu restart parameters is done in three different fashions:
- directly setting the four parameters individually
- copying the four parameters with memcpy (using 4 * sizeof(long))
- copying the four parameters using a private structure

In addition code in entry*.S relies on a certain order of the restart
members of struct _lowcore.

Make all of this more robust to future changes by adding a
mem_absolute_assign(dest, val) define, which assigns val to dest
using absolute addressing mode. Also the load multiple instructions
in entry*.S have been split into separate load instruction so the
order of the struct _lowcore members doesn't matter anymore.

In addition move the prototypes of memcpy_real/absolute from uaccess.h
to processor.h. These memcpy* variants are not related to uaccess at all.
string.h doesn't seem to match as well, so lets use processor.h.

Also replace the eight byte array in struct _lowcore which represents a
misaliged u64 with a u64. The compiler will always create code that
handles the misaligned u64 correctly.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

3 files changed, 11 insertions, 8 deletions

diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h
index 47853debb3b9..a47c6e221a95 100644
--- a/arch/s390/include/asm/lowcore.h
+++ b/arch/s390/include/asm/lowcore.h
@@ -302,12 +302,7 @@ struct _lowcore {
          */
         __u64   ipib;                           /* 0x0e00 */
         __u32   ipib_checksum;                  /* 0x0e08 */
-        /*
-         * Because the vmcore_info pointer is not 8 byte aligned it never
-         * should not be accessed directly. For accessing the pointer, first
-         * copy it to a local pointer variable.
-         */
-        __u8    vmcore_info[8];                 /* 0x0e0c */
+        __u64   vmcore_info;                    /* 0x0e0c */
         __u8    pad_0x0e14[0x0e18-0x0e14];      /* 0x0e14 */
         __u64   os_info;                        /* 0x0e18 */
         __u8    pad_0x0e20[0x0f00-0x0e20];      /* 0x0e20 */
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 20d0585cf905..f1700c5c8884 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -348,4 +348,14 @@ extern void (*s390_base_ext_handler_fn)(void);
         ".previous\n"
 #endif
 
+extern int memcpy_real(void *, void *, size_t);
+extern void memcpy_absolute(void *, void *, size_t);
+
+#define mem_assign_absolute(dest, val) {                        \
+        __typeof__(dest) __tmp = (val);                         \
+                                                                \
+        BUILD_BUG_ON(sizeof(__tmp) != sizeof(val));             \
+        memcpy_absolute(&(dest), &__tmp, sizeof(__tmp));        \
+}
+
 #endif                                 /* __ASM_S390_PROCESSOR_H           */
diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
index 1f3a79bcd262..7e7285179aad 100644
--- a/arch/s390/include/asm/uaccess.h
+++ b/arch/s390/include/asm/uaccess.h
@@ -381,8 +381,6 @@ clear_user(void __user *to, unsigned long n)
         return n;
 }
 
-extern int memcpy_real(void *, void *, size_t);
-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);