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

arch/s390/include/asm/lowcore.h

···
 	 */
 	__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 */

arch/s390/include/asm/processor.h

···
 	".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           */

arch/s390/include/asm/uaccess.h

···
 	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);
 

arch/s390/kernel/asm-offsets.c

···
 	DEFINE(__LC_PANIC_STACK, offsetof(struct _lowcore, panic_stack));
 	DEFINE(__LC_RESTART_STACK, offsetof(struct _lowcore, restart_stack));
 	DEFINE(__LC_RESTART_FN, offsetof(struct _lowcore, restart_fn));
+	DEFINE(__LC_RESTART_DATA, offsetof(struct _lowcore, restart_data));
+	DEFINE(__LC_RESTART_SOURCE, offsetof(struct _lowcore, restart_source));
 	DEFINE(__LC_USER_ASCE, offsetof(struct _lowcore, user_asce));
 	DEFINE(__LC_INT_CLOCK, offsetof(struct _lowcore, int_clock));
 	DEFINE(__LC_MCCK_CLOCK, offsetof(struct _lowcore, mcck_clock));

arch/s390/kernel/entry.S

···
 	mvc	__PT_PSW(8,%r15),__LC_RST_OLD_PSW # store restart old psw
 	ahi	%r15,-STACK_FRAME_OVERHEAD	# create stack frame on stack
 	xc	0(STACK_FRAME_OVERHEAD,%r15),0(%r15)
-	lm	%r1,%r3,__LC_RESTART_FN		# load fn, parm & source cpu
+	l	%r1,__LC_RESTART_FN		# load fn, parm & source cpu
+	l	%r2,__LC_RESTART_DATA
+	l	%r3,__LC_RESTART_SOURCE
 	ltr	%r3,%r3				# test source cpu address
 	jm	1f				# negative -> skip source stop
 0:	sigp	%r4,%r3,SIGP_SENSE		# sigp sense to source cpu

arch/s390/kernel/entry64.S

···
 	mvc	__PT_PSW(16,%r15),__LC_RST_OLD_PSW # store restart old psw
 	aghi	%r15,-STACK_FRAME_OVERHEAD	# create stack frame on stack
 	xc	0(STACK_FRAME_OVERHEAD,%r15),0(%r15)
-	lmg	%r1,%r3,__LC_RESTART_FN		# load fn, parm & source cpu
+	lg	%r1,__LC_RESTART_FN		# load fn, parm & source cpu
+	lg	%r2,__LC_RESTART_DATA
+	lg	%r3,__LC_RESTART_SOURCE
 	ltgr	%r3,%r3				# test source cpu address
 	jm	1f				# negative -> skip source stop
 0:	sigp	%r4,%r3,SIGP_SENSE		# sigp sense to source cpu

arch/s390/kernel/ipl.c

···
 
 static void dump_reipl_run(struct shutdown_trigger *trigger)
 {
-	struct {
-		void	*addr;
-		__u32	csum;
-	} __packed ipib;
+	unsigned long ipib = (unsigned long) &reipl_block_actual;
+	unsigned int csum;
 
-	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));
+	csum = csum_partial(reipl_block_actual, reipl_block_actual->hdr.len, 0);
+	mem_assign_absolute(S390_lowcore.ipib, ipib);
+	mem_assign_absolute(S390_lowcore.ipib_checksum, csum);
 	dump_run(trigger);
 }
 

arch/s390/kernel/os_info.c

···
 	os_info.version_minor = OS_INFO_VERSION_MINOR;
 	os_info.magic = OS_INFO_MAGIC;
 	os_info.csum = os_info_csum(&os_info);
-	memcpy_absolute(&S390_lowcore.os_info, &ptr, sizeof(ptr));
+	mem_assign_absolute(S390_lowcore.os_info, (unsigned long) ptr);
 }
 
 #ifdef CONFIG_CRASH_DUMP

arch/s390/kernel/setup.c

···
 	lc->restart_source = -1UL;
 
 	/* 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));
+	mem_assign_absolute(S390_lowcore.restart_stack, lc->restart_stack);
+	mem_assign_absolute(S390_lowcore.restart_fn, lc->restart_fn);
+	mem_assign_absolute(S390_lowcore.restart_data, lc->restart_data);
+	mem_assign_absolute(S390_lowcore.restart_source, lc->restart_source);
+	mem_assign_absolute(S390_lowcore.restart_psw, lc->restart_psw);
 
 	set_prefix((u32)(unsigned long) lc);
 	lowcore_ptr[0] = lc;
···
 static void __init setup_vmcoreinfo(void)
 {
 #ifdef CONFIG_KEXEC
-	unsigned long ptr = paddr_vmcoreinfo_note();
-
-	memcpy_absolute(&S390_lowcore.vmcore_info, &ptr, sizeof(ptr));
+	mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
 #endif
 }
 

arch/s390/kernel/smp.c

···
 			  void *data, unsigned long stack)
 {
 	struct _lowcore *lc = lowcore_ptr[pcpu - pcpu_devices];
-	struct {
-		unsigned long	stack;
-		void		*func;
-		void		*data;
-		unsigned long	source;
-	} restart = { stack, func, data, stap() };
+	unsigned long source_cpu = stap();
 
 	__load_psw_mask(psw_kernel_bits);
-	if (pcpu->address == restart.source)
+	if (pcpu->address == source_cpu)
 		func(data);	/* should not return */
 	/* Stop target cpu (if func returns this stops the current cpu). */
 	pcpu_sigp_retry(pcpu, SIGP_STOP, 0);
 	/* Restart func on the target cpu and stop the current cpu. */
-	memcpy_absolute(&lc->restart_stack, &restart, sizeof(restart));
+	mem_assign_absolute(lc->restart_stack, stack);
+	mem_assign_absolute(lc->restart_fn, (unsigned long) func);
+	mem_assign_absolute(lc->restart_data, (unsigned long) data);
+	mem_assign_absolute(lc->restart_source, source_cpu);
 	asm volatile(
 		"0:	sigp	0,%0,%2	# sigp restart to target cpu\n"
 		"	brc	2,0b	# busy, try again\n"
 		"1:	sigp	0,%1,%3	# sigp stop to current cpu\n"
 		"	brc	2,1b	# busy, try again\n"
-		: : "d" (pcpu->address), "d" (restart.source),
+		: : "d" (pcpu->address), "d" (source_cpu),
 		    "K" (SIGP_RESTART), "K" (SIGP_STOP)
 		: "0", "1", "cc");
 	for (;;) ;