[S390] Improve address space mode selection.

Introduce user_mode to replace the two variables switch_amode and
s390_noexec. There are three valid combinations of the old values:
  1) switch_amode == 0 && s390_noexec == 0
  2) switch_amode == 1 && s390_noexec == 0
  3) switch_amode == 1 && s390_noexec == 1
They get replaced by
  1) user_mode == HOME_SPACE_MODE
  2) user_mode == PRIMARY_SPACE_MODE
  3) user_mode == SECONDARY_SPACE_MODE
The new kernel parameter user_mode=[primary,secondary,home] lets
you choose the address space mode the user space processes should
use. In addition the CONFIG_S390_SWITCH_AMODE config option
is removed.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig

@@ -220,23 +220,8 @@ config AUDIT_ARCH
 	bool
 	default y
 
-config S390_SWITCH_AMODE
-	bool "Switch kernel/user addressing modes"
-	help
-	  This option allows to switch the addressing modes of kernel and user
-	  space. The kernel parameter switch_amode=on will enable this feature,
-	  default is disabled. Enabling this (via kernel parameter) on machines
-	  earlier than IBM System z9-109 EC/BC will reduce system performance.
-
-	  Note that this option will also be selected by selecting the execute
-	  protection option below. Enabling the execute protection via the
-	  noexec kernel parameter will also switch the addressing modes,
-	  independent of the switch_amode kernel parameter.
-
-
 config S390_EXEC_PROTECT
 	bool "Data execute protection"
-	select S390_SWITCH_AMODE
 	help
 	  This option allows to enable a buffer overflow protection for user
 	  space programs and it also selects the addressing mode option above.

arch/s390/defconfig

@@ -185,7 +185,6 @@ CONFIG_HOTPLUG_CPU=y
 CONFIG_COMPAT=y
 CONFIG_SYSVIPC_COMPAT=y
 CONFIG_AUDIT_ARCH=y
-CONFIG_S390_SWITCH_AMODE=y
 CONFIG_S390_EXEC_PROTECT=y
 
 #

arch/s390/include/asm/mmu_context.h

@@ -36,7 +36,7 @@ static inline int init_new_context(struct task_struct *tsk,
 		mm->context.has_pgste = 1;
 		mm->context.alloc_pgste = 1;
 	} else {
-		mm->context.noexec = s390_noexec;
+		mm->context.noexec = (user_mode == SECONDARY_SPACE_MODE);
 		mm->context.has_pgste = 0;
 		mm->context.alloc_pgste = 0;
 	}
@@ -58,7 +58,7 @@ static inline void update_mm(struct mm_struct *mm, struct task_struct *tsk)
 	pgd_t *pgd = mm->pgd;
 
 	S390_lowcore.user_asce = mm->context.asce_bits | __pa(pgd);
-	if (switch_amode) {
+	if (user_mode != HOME_SPACE_MODE) {
 		/* Load primary space page table origin. */
 		pgd = mm->context.noexec ? get_shadow_table(pgd) : pgd;
 		S390_lowcore.user_exec_asce = mm->context.asce_bits | __pa(pgd);

arch/s390/include/asm/pgalloc.h

@@ -143,7 +143,8 @@ static inline pgd_t *pgd_alloc(struct mm_struct *mm)
 	spin_lock_init(&mm->context.list_lock);
 	INIT_LIST_HEAD(&mm->context.crst_list);
 	INIT_LIST_HEAD(&mm->context.pgtable_list);
-	return (pgd_t *) crst_table_alloc(mm, s390_noexec);
+	return (pgd_t *)
+		crst_table_alloc(mm, user_mode == SECONDARY_SPACE_MODE);
 }
 #define pgd_free(mm, pgd) crst_table_free(mm, (unsigned long *) pgd)
 

arch/s390/include/asm/setup.h

@@ -49,17 +49,12 @@ extern unsigned long memory_end;
 
 void detect_memory_layout(struct mem_chunk chunk[]);
 
-#ifdef CONFIG_S390_SWITCH_AMODE
-extern unsigned int switch_amode;
-#else
-#define switch_amode	(0)
-#endif
-
-#ifdef CONFIG_S390_EXEC_PROTECT
-extern unsigned int s390_noexec;
-#else
-#define s390_noexec	(0)
-#endif
+#define PRIMARY_SPACE_MODE	0
+#define ACCESS_REGISTER_MODE	1
+#define SECONDARY_SPACE_MODE	2
+#define HOME_SPACE_MODE		3
+
+extern unsigned int user_mode;
 
 /*
  * Machine features detected in head.S

arch/s390/kernel/setup.c

@@ -305,9 +305,8 @@ static int __init early_parse_mem(char *p)
 }
 early_param("mem", early_parse_mem);
 
-#ifdef CONFIG_S390_SWITCH_AMODE
-unsigned int switch_amode = 0;
-EXPORT_SYMBOL_GPL(switch_amode);
+unsigned int user_mode = HOME_SPACE_MODE;
+EXPORT_SYMBOL_GPL(user_mode);
 
 static int set_amode_and_uaccess(unsigned long user_amode,
 				 unsigned long user32_amode)
@@ -340,48 +339,53 @@ static int set_amode_and_uaccess(unsigned long user_amode,
  */
 static int __init early_parse_switch_amode(char *p)
 {
-	switch_amode = 1;
+	if (user_mode != SECONDARY_SPACE_MODE)
+		user_mode = PRIMARY_SPACE_MODE;
 	return 0;
 }
 early_param("switch_amode", early_parse_switch_amode);
 
-#else /* CONFIG_S390_SWITCH_AMODE */
-static inline int set_amode_and_uaccess(unsigned long user_amode,
-					unsigned long user32_amode)
+static int __init early_parse_user_mode(char *p)
 {
+	if (p && strcmp(p, "primary") == 0)
+		user_mode = PRIMARY_SPACE_MODE;
+#ifdef CONFIG_S390_EXEC_PROTECT
+	else if (p && strcmp(p, "secondary") == 0)
+		user_mode = SECONDARY_SPACE_MODE;
+#endif
+	else if (!p || strcmp(p, "home") == 0)
+		user_mode = HOME_SPACE_MODE;
+	else
+		return 1;
 	return 0;
 }
-#endif /* CONFIG_S390_SWITCH_AMODE */
+early_param("user_mode", early_parse_user_mode);
 
 #ifdef CONFIG_S390_EXEC_PROTECT
-unsigned int s390_noexec = 0;
-EXPORT_SYMBOL_GPL(s390_noexec);
-
 /*
  * Enable execute protection?
  */
 static int __init early_parse_noexec(char *p)
 {
 	if (!strncmp(p, "off", 3))
 		return 0;
-	switch_amode = 1;
-	s390_noexec = 1;
+	user_mode = SECONDARY_SPACE_MODE;
 	return 0;
 }
 early_param("noexec", early_parse_noexec);
 #endif /* CONFIG_S390_EXEC_PROTECT */
 
 static void setup_addressing_mode(void)
 {
-	if (s390_noexec) {
+	if (user_mode == SECONDARY_SPACE_MODE) {
 		if (set_amode_and_uaccess(PSW_ASC_SECONDARY,
 					  PSW32_ASC_SECONDARY))
 			pr_info("Execute protection active, "
 				"mvcos available\n");
 		else
 			pr_info("Execute protection active, "
 				"mvcos not available\n");
-	} else if (switch_amode) {
+	} else if (user_mode == PRIMARY_SPACE_MODE) {
 		if (set_amode_and_uaccess(PSW_ASC_PRIMARY, PSW32_ASC_PRIMARY))
 			pr_info("Address spaces switched, "
 				"mvcos available\n");
@@ -411,7 +415,7 @@ setup_lowcore(void)
 	lc->restart_psw.mask = PSW_BASE_BITS | PSW_DEFAULT_KEY;
 	lc->restart_psw.addr =
 		PSW_ADDR_AMODE | (unsigned long) restart_int_handler;
-	if (switch_amode)
+	if (user_mode != HOME_SPACE_MODE)
 		lc->restart_psw.mask |= PSW_ASC_HOME;
 	lc->external_new_psw.mask = psw_kernel_bits;
 	lc->external_new_psw.addr =

arch/s390/kernel/vdso.c

@@ -86,7 +86,8 @@ static void vdso_init_data(struct vdso_data *vd)
 	unsigned int facility_list;
 
 	facility_list = stfl();
-	vd->ectg_available = switch_amode && (facility_list & 1);
+	vd->ectg_available =
+		user_mode != HOME_SPACE_MODE && (facility_list & 1);
 }
 
 #ifdef CONFIG_64BIT
@@ -114,7 +115,7 @@ int vdso_alloc_per_cpu(int cpu, struct _lowcore *lowcore)
 
 	lowcore->vdso_per_cpu_data = __LC_PASTE;
 
-	if (!switch_amode || !vdso_enabled)
+	if (user_mode == HOME_SPACE_MODE || !vdso_enabled)
 		return 0;
 
 	segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
@@ -160,7 +161,7 @@ void vdso_free_per_cpu(int cpu, struct _lowcore *lowcore)
 	unsigned long segment_table, page_table, page_frame;
 	u32 *psal, *aste;
 
-	if (!switch_amode || !vdso_enabled)
+	if (user_mode == HOME_SPACE_MODE || !vdso_enabled)
 		return;
 
 	psal = (u32 *)(addr_t) lowcore->paste[4];
@@ -184,7 +185,7 @@ static void __vdso_init_cr5(void *dummy)
 
 static void vdso_init_cr5(void)
 {
-	if (switch_amode && vdso_enabled)
+	if (user_mode != HOME_SPACE_MODE && vdso_enabled)
 		on_each_cpu(__vdso_init_cr5, NULL, 1);
 }
 #endif /* CONFIG_64BIT */

arch/s390/kvm/Kconfig

@@ -20,7 +20,6 @@ config KVM
 	depends on HAVE_KVM && EXPERIMENTAL
 	select PREEMPT_NOTIFIERS
 	select ANON_INODES
-	select S390_SWITCH_AMODE
 	---help---
 	  Support hosting paravirtualized guest machines using the SIE
 	  virtualization capability on the mainframe. This should work

arch/s390/lib/uaccess_mvcos.c

@@ -162,7 +162,6 @@ static size_t clear_user_mvcos(size_t size, void __user *to)
 	return size;
 }
 
-#ifdef CONFIG_S390_SWITCH_AMODE
 static size_t strnlen_user_mvcos(size_t count, const char __user *src)
 {
 	char buf[256];
@@ -200,7 +199,6 @@ static size_t strncpy_from_user_mvcos(size_t count, const char __user *src,
 	} while ((len_str == len) && (done < count));
 	return done;
 }
-#endif /* CONFIG_S390_SWITCH_AMODE */
 
 struct uaccess_ops uaccess_mvcos = {
 	.copy_from_user = copy_from_user_mvcos_check,
@@ -215,7 +213,6 @@ struct uaccess_ops uaccess_mvcos = {
 	.futex_atomic_cmpxchg = futex_atomic_cmpxchg_std,
 };
 
-#ifdef CONFIG_S390_SWITCH_AMODE
 struct uaccess_ops uaccess_mvcos_switch = {
 	.copy_from_user = copy_from_user_mvcos,
 	.copy_from_user_small = copy_from_user_mvcos,
@@ -228,4 +225,3 @@ struct uaccess_ops uaccess_mvcos_switch = {
 	.futex_atomic_op = futex_atomic_op_pt,
 	.futex_atomic_cmpxchg = futex_atomic_cmpxchg_pt,
 };
-#endif

arch/s390/mm/fault.c

@@ -112,7 +112,7 @@ static inline int user_space_fault(unsigned long trans_exc_code)
 	if (trans_exc_code == 2)
 		/* Access via secondary space, set_fs setting decides */
 		return current->thread.mm_segment.ar4;
-	if (!switch_amode)
+	if (user_mode == HOME_SPACE_MODE)
 		/* User space if the access has been done via home space. */
 		return trans_exc_code == 3;
 	/*
@@ -168,7 +168,7 @@ static void do_no_context(struct pt_regs *regs, unsigned long error_code,
 	 * terminate things with extreme prejudice.
 	 */
 	address = trans_exc_code & __FAIL_ADDR_MASK;
-	if (user_space_fault(trans_exc_code) == 0)
+	if (!user_space_fault(trans_exc_code))
 		printk(KERN_ALERT "Unable to handle kernel pointer dereference"
 		       " at virtual kernel address %p\n", (void *)address);
 	else

arch/s390/mm/pgtable.c

@@ -269,7 +269,7 @@ int s390_enable_sie(void)
 	struct mm_struct *mm, *old_mm;
 
 	/* Do we have switched amode? If no, we cannot do sie */
-	if (!switch_amode)
+	if (user_mode == HOME_SPACE_MODE)
 		return -EINVAL;
 
 	/* Do we have pgstes? if yes, we are done */