s390: rework __switch_to() to allow larger task_struct offsets

If GCC_PLUGIN_RANDSTRUCT is enabled the members of task_struct will be
shuffled around. The offsets of the "pid" and "stack" members within
task_struct may not necessarily fit into 12 bits anymore, which causes
compile errors within __switch_to, since instructions are used, which
only have a 12 bit displacement field.

Therefore rework __switch_to, to allow for larger offsets.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index a316cd6999ad9712defdf46db85e16eb429aebcb..9e5f6cd8e4c2e443a2c7fb46792157933447d170 100644 (file)
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -180,18 +180,17 @@ _PIF_WORK = (_PIF_PER_TRAP | _PIF_SYSCALL_RESTART)
  */
 ENTRY(__switch_to)
        stmg    %r6,%r15,__SF_GPRS(%r15)        # store gprs of prev task
-       lgr     %r1,%r2
-       aghi    %r1,__TASK_thread               # thread_struct of prev task
-       lg      %r5,__TASK_stack(%r3)           # start of kernel stack of next
-       stg     %r15,__THREAD_ksp(%r1)          # store kernel stack of prev
-       lgr     %r1,%r3
-       aghi    %r1,__TASK_thread               # thread_struct of next task
+       lghi    %r4,__TASK_stack
+       lghi    %r1,__TASK_thread
+       lg      %r5,0(%r4,%r3)                  # start of kernel stack of next
+       stg     %r15,__THREAD_ksp(%r1,%r2)      # store kernel stack of prev
        lgr     %r15,%r5
        aghi    %r15,STACK_INIT                 # end of kernel stack of next
        stg     %r3,__LC_CURRENT                # store task struct of next
        stg     %r15,__LC_KERNEL_STACK          # store end of kernel stack
-       lg      %r15,__THREAD_ksp(%r1)          # load kernel stack of next
-       mvc     __LC_CURRENT_PID(4,%r0),__TASK_pid(%r3) # store pid of next
+       lg      %r15,__THREAD_ksp(%r1,%r3)      # load kernel stack of next
+       aghi    %r3,__TASK_pid
+       mvc     __LC_CURRENT_PID(4,%r0),0(%r3)  # store pid of next
        lmg     %r6,%r15,__SF_GPRS(%r15)        # load gprs of next task
        TSTMSK  __LC_MACHINE_FLAGS,MACHINE_FLAG_LPP
        bzr     %r14