[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/head64.S b/arch/s390/kernel/head64.S
index af09e18cc5d..37010709fe6 100644
--- a/arch/s390/kernel/head64.S
+++ b/arch/s390/kernel/head64.S
@@ -134,7 +134,7 @@ startup_continue:
         .quad   .Lduct                  # cr2: dispatchable unit control table
         .quad   0                       # cr3: instruction authorization
         .quad   0                       # cr4: instruction authorization
-        .quad   0xffffffffffffffff      # cr5: primary-aste origin
+        .quad   .Lduct                  # cr5: primary-aste origin
         .quad   0                       # cr6:  I/O interrupts
         .quad   0                       # cr7:  secondary space segment table
         .quad   0                       # cr8:  access registers translation
@@ -145,14 +145,19 @@ startup_continue:
         .quad   0                       # cr13: home space segment table
         .quad   0xc0000000              # cr14: machine check handling off
         .quad   0                       # cr15: linkage stack operations
-.Lduct: .long   0,0,0,0,0,0,0,0
-        .long   0,0,0,0,0,0,0,0
 .Lpcmsk:.quad   0x0000000180000000
 .L4malign:.quad 0xffffffffffc00000
 .Lscan2g:.quad  0x80000000 + 0x20000 - 8        # 2GB + 128K - 8
 .Lnop:  .long   0x07000700
 .Lparmaddr:
         .quad   PARMAREA
+        .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