s390/maccess: rework absolute lowcore accessors

Macro mem_assign_absolute() is able to access the whole memory, but
is only used and makes sense when updating the absolute lowcore.
Instead, introduce get_abs_lowcore() and put_abs_lowcore() macros
that limit access to absolute lowcore addresses only.

Suggested-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

Author: Alexander Gordeev

arch/s390/include/asm/processor.h

@@ -319,11 +319,18 @@ extern void (*s390_base_pgm_handler_fn)(struct pt_regs *regs);
 extern int memcpy_real(void *, unsigned long, size_t);
 extern void memcpy_absolute(void *, void *, size_t);
 
-#define mem_assign_absolute(dest, val) do {			\
-	__typeof__(dest) __tmp = (val);				\
-								\
-	BUILD_BUG_ON(sizeof(__tmp) != sizeof(val));		\
-	memcpy_absolute(&(dest), &__tmp, sizeof(__tmp));	\
+#define put_abs_lowcore(member, x) do {					\
+	unsigned long __abs_address = offsetof(struct lowcore, member);	\
+	__typeof__(((struct lowcore *)0)->member) __tmp = (x);		\
+									\
+	memcpy_absolute(__va(__abs_address), &__tmp, sizeof(__tmp));	\
+} while (0)
+
+#define get_abs_lowcore(x, member) do {					\
+	unsigned long __abs_address = offsetof(struct lowcore, member);	\
+	__typeof__(((struct lowcore *)0)->member) *__ptr = &(x);	\
+									\
+	memcpy_absolute(__ptr, __va(__abs_address), sizeof(*__ptr));	\
 } while (0)
 
 extern int s390_isolate_bp(void);

arch/s390/kernel/ipl.c

@@ -1646,8 +1646,8 @@ static void dump_reipl_run(struct shutdown_trigger *trigger)
 
 	csum = (__force unsigned int)
 	       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);
+	put_abs_lowcore(ipib, ipib);
+	put_abs_lowcore(ipib_checksum, csum);
 	dump_run(trigger);
 }
 

arch/s390/kernel/machine_kexec.c

@@ -226,7 +226,7 @@ void arch_crash_save_vmcoreinfo(void)
 	vmcoreinfo_append_str("SAMODE31=%lx\n", __samode31);
 	vmcoreinfo_append_str("EAMODE31=%lx\n", __eamode31);
 	vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
-	mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
+	put_abs_lowcore(vmcore_info, paddr_vmcoreinfo_note());
 }
 
 void machine_shutdown(void)

arch/s390/kernel/os_info.c

@@ -63,7 +63,7 @@ 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);
-	mem_assign_absolute(S390_lowcore.os_info, __pa(ptr));
+	put_abs_lowcore(os_info, __pa(ptr));
 }
 
 #ifdef CONFIG_CRASH_DUMP

arch/s390/kernel/setup.c

@@ -481,11 +481,11 @@ static void __init setup_lowcore_dat_off(void)
 	lc->mcck_stack = mcck_stack + STACK_INIT_OFFSET;
 
 	/* Setup absolute zero lowcore */
-	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);
+	put_abs_lowcore(restart_stack, lc->restart_stack);
+	put_abs_lowcore(restart_fn, lc->restart_fn);
+	put_abs_lowcore(restart_data, lc->restart_data);
+	put_abs_lowcore(restart_source, lc->restart_source);
+	put_abs_lowcore(restart_psw, lc->restart_psw);
 
 	lc->spinlock_lockval = arch_spin_lockval(0);
 	lc->spinlock_index = 0;
@@ -501,6 +501,7 @@ static void __init setup_lowcore_dat_off(void)
 static void __init setup_lowcore_dat_on(void)
 {
 	struct lowcore *lc = lowcore_ptr[0];
+	int cr;
 
 	__ctl_clear_bit(0, 28);
 	S390_lowcore.external_new_psw.mask |= PSW_MASK_DAT;
@@ -509,10 +510,10 @@ static void __init setup_lowcore_dat_on(void)
 	S390_lowcore.io_new_psw.mask |= PSW_MASK_DAT;
 	__ctl_store(S390_lowcore.cregs_save_area, 0, 15);
 	__ctl_set_bit(0, 28);
-	mem_assign_absolute(S390_lowcore.restart_flags, RESTART_FLAG_CTLREGS);
-	mem_assign_absolute(S390_lowcore.program_new_psw, lc->program_new_psw);
-	memcpy_absolute(&S390_lowcore.cregs_save_area, lc->cregs_save_area,
-			sizeof(S390_lowcore.cregs_save_area));
+	put_abs_lowcore(restart_flags, RESTART_FLAG_CTLREGS);
+	put_abs_lowcore(program_new_psw, lc->program_new_psw);
+	for (cr = 0; cr < ARRAY_SIZE(lc->cregs_save_area); cr++)
+		put_abs_lowcore(cregs_save_area[cr], lc->cregs_save_area[cr]);
 }
 
 static struct resource code_resource = {

arch/s390/kernel/smp.c

@@ -332,10 +332,10 @@ static void pcpu_delegate(struct pcpu *pcpu,
 		lc->restart_data = (unsigned long)data;
 		lc->restart_source = source_cpu;
 	} else {
-		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);
+		put_abs_lowcore(restart_stack, stack);
+		put_abs_lowcore(restart_fn, (unsigned long)func);
+		put_abs_lowcore(restart_data, (unsigned long)data);
+		put_abs_lowcore(restart_source, source_cpu);
 	}
 	__bpon();
 	asm volatile(
@@ -591,9 +591,9 @@ void smp_ctl_set_clear_bit(int cr, int bit, bool set)
 		parms.andval = ~(1UL << bit);
 	}
 	spin_lock(&ctl_lock);
-	memcpy_absolute(&ctlreg, &S390_lowcore.cregs_save_area[cr], sizeof(ctlreg));
+	get_abs_lowcore(ctlreg, cregs_save_area[cr]);
 	ctlreg = (ctlreg & parms.andval) | parms.orval;
-	memcpy_absolute(&S390_lowcore.cregs_save_area[cr], &ctlreg, sizeof(ctlreg));
+	put_abs_lowcore(cregs_save_area[cr], ctlreg);
 	spin_unlock(&ctl_lock);
 	on_each_cpu(smp_ctl_bit_callback, &parms, 1);
 }