[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>

1 files changed, 20 insertions, 16 deletions

diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 061479ff029f..0663287fa1b3 100644
--- a/arch/s390/kernel/setup.c
+++ b/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)
@@ -340,23 +339,29 @@ 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?
  */
@@ -364,8 +369,7 @@ 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);
@@ -373,7 +377,7 @@ early_param("noexec", early_parse_noexec);
 
 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, "
@@ -381,7 +385,7 @@ static void setup_addressing_mode(void)
                 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 =