[S390] Fixed handling of access register mode faults.

Replaced check_user_space() + __check_access_register with the new
check_space(). The old functions made wrong assumptions about kernel
and user space when the kernel and user address spaces are switched
(kernel in home space, user in primary/secondary space).
Secondly the user process can switch to the accress register mode if
it is running in primary or secondary mode. In addition it can load
an arbitrary value to the access registers. If any other value than
0 for primary space or 1 for secondary space is loaded and memory
is accessed using the base register related to the access register,
the program should be terminated with a SIGSEGV. To achieve that the
DUALD pointer in the DUCT and the PSALD pointer in the PASTE need
to point to an array of 8 invalid access-list entries to get a
ALEN-translation exception if an invalid alet is used.

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

1 files changed, 8 insertions, 3 deletions

diff --git a/arch/s390/kernel/head31.S b/arch/s390/kernel/head31.S
index da7c8bb80982..dc364c1419af 100644
--- a/arch/s390/kernel/head31.S
+++ b/arch/s390/kernel/head31.S
@@ -121,7 +121,7 @@ startup_continue:
         .long   .Lduct                  # cr2: dispatchable unit control table
         .long   0                       # cr3: instruction authorization
         .long   0                       # cr4: instruction authorization
-        .long   0xffffffff              # cr5: primary-aste origin
+        .long   .Lduct                  # cr5: primary-aste origin
         .long   0                       # cr6:  I/O interrupts
         .long   0                       # cr7:  secondary space segment table
         .long   0                       # cr8:  access registers translation
@@ -132,8 +132,6 @@ startup_continue:
         .long   0                       # cr13: home space segment table
         .long   0xc0000000              # cr14: machine check handling off
         .long   0                       # cr15: linkage stack operations
-.Lduct: .long   0,0,0,0,0,0,0,0
-        .long   0,0,0,0,0,0,0,0
 .Lpcfpu:.long   0x00080000,0x80000000 + .Lchkfpu
 .Lpccsp:.long   0x00080000,0x80000000 + .Lchkcsp
 .Lpcmvpg:.long  0x00080000,0x80000000 + .Lchkmvpg
@@ -147,6 +145,13 @@ startup_continue:
 .Linittu:   .long init_thread_union
 .Lstartup_init:
             .long startup_init
+        .align  64
+.Lduct: .long   0,0,0,0,.Lduald,0,0,0
+        .long   0,0,0,0,0,0,0,0
+        .align  128
+.Lduald:.rept   8
+        .long   0x80000000,0,0,0        # invalid access-list entries
+        .endr
 
         .org    0x12000
         .globl  _ehead