s390/kasan: increase instrumented stack size to 64k

Increase kasan instrumented kernel stack size from 32k to 64k. Other
architectures seems to get away with just doubling kernel stack size under
kasan, but on s390 this appears to be not enough due to bigger frame size.
The particular pain point is kasan inlined checks (CONFIG_KASAN_INLINE
vs CONFIG_KASAN_OUTLINE). With inlined checks one particular case hitting
stack overflow is fs sync on xfs filesystem:

 #0 [9a0681e8]  704 bytes  check_usage at 34b1fc
 #1 [9a0684a8]  432 bytes  check_usage at 34c710
 #2 [9a068658]  1048 bytes  validate_chain at 35044a
 #3 [9a068a70]  312 bytes  __lock_acquire at 3559fe
 #4 [9a068ba8]  440 bytes  lock_acquire at 3576ee
 #5 [9a068d60]  104 bytes  _raw_spin_lock at 21b44e0
 torvalds#6 [9a068dc8]  1992 bytes  enqueue_entity at 2dbf72
 torvalds#7 [9a069590]  1496 bytes  enqueue_task_fair at 2df5f0
 torvalds#8 [9a069b68]  64 bytes  ttwu_do_activate at 28f438
 torvalds#9 [9a069ba8]  552 bytes  try_to_wake_up at 298c4c
 torvalds#10 [9a069dd0]  168 bytes  wake_up_worker at 23f97c
 torvalds#11 [9a069e78]  200 bytes  insert_work at 23fc2e
 torvalds#12 [9a069f40]  648 bytes  __queue_work at 2487c0
 torvalds#13 [9a06a1c8]  200 bytes  __queue_delayed_work at 24db28
 torvalds#14 [9a06a290]  248 bytes  mod_delayed_work_on at 24de84
 torvalds#15 [9a06a388]  24 bytes  kblockd_mod_delayed_work_on at 153e2a0
 torvalds#16 [9a06a3a0]  288 bytes  __blk_mq_delay_run_hw_queue at 158168c
 torvalds#17 [9a06a4c0]  192 bytes  blk_mq_run_hw_queue at 1581a3c
 torvalds#18 [9a06a580]  184 bytes  blk_mq_sched_insert_requests at 15a2192
 torvalds#19 [9a06a638]  1024 bytes  blk_mq_flush_plug_list at 1590f3a
 torvalds#20 [9a06aa38]  704 bytes  blk_flush_plug_list at 1555028
 torvalds#21 [9a06acf8]  320 bytes  schedule at 219e476
 torvalds#22 [9a06ae38]  760 bytes  schedule_timeout at 21b0aac
 torvalds#23 [9a06b130]  408 bytes  wait_for_common at 21a1706
 torvalds#24 [9a06b2c8]  360 bytes  xfs_buf_iowait at fa1540
 torvalds#25 [9a06b430]  256 bytes  __xfs_buf_submit at fadae6
 torvalds#26 [9a06b530]  264 bytes  xfs_buf_read_map at fae3f6
 torvalds#27 [9a06b638]  656 bytes  xfs_trans_read_buf_map at 10ac9a8
 torvalds#28 [9a06b8c8]  304 bytes  xfs_btree_kill_root at e72426
 torvalds#29 [9a06b9f8]  288 bytes  xfs_btree_lookup_get_block at e7bc5e
 torvalds#30 [9a06bb18]  624 bytes  xfs_btree_lookup at e7e1a6
 torvalds#31 [9a06bd88]  2664 bytes  xfs_alloc_ag_vextent_near at dfa070
 torvalds#32 [9a06c7f0]  144 bytes  xfs_alloc_ag_vextent at dff3ca
 torvalds#33 [9a06c880]  1128 bytes  xfs_alloc_vextent at e05fce
 torvalds#34 [9a06cce8]  584 bytes  xfs_bmap_btalloc at e58342
 torvalds#35 [9a06cf30]  1336 bytes  xfs_bmapi_write at e618de
 torvalds#36 [9a06d468]  776 bytes  xfs_iomap_write_allocate at ff678e
 torvalds#37 [9a06d770]  720 bytes  xfs_map_blocks at f82af8
 torvalds#38 [9a06da40]  928 bytes  xfs_writepage_map at f83cd6
 torvalds#39 [9a06dde0]  320 bytes  xfs_do_writepage at f85872
 torvalds#40 [9a06df20]  1320 bytes  write_cache_pages at 73dfe8
 torvalds#41 [9a06e448]  208 bytes  xfs_vm_writepages at f7f892
 torvalds#42 [9a06e518]  88 bytes  do_writepages at 73fe6a
 torvalds#43 [9a06e570]  872 bytes  __writeback_single_inode at a20cb6
 torvalds#44 [9a06e8d8]  664 bytes  writeback_sb_inodes at a23be2
 torvalds#45 [9a06eb70]  296 bytes  __writeback_inodes_wb at a242e0
 torvalds#46 [9a06ec98]  928 bytes  wb_writeback at a2500e
 torvalds#47 [9a06f038]  848 bytes  wb_do_writeback at a260ae
 torvalds#48 [9a06f388]  536 bytes  wb_workfn at a28228
 torvalds#49 [9a06f5a0]  1088 bytes  process_one_work at 24a234
 torvalds#50 [9a06f9e0]  1120 bytes  worker_thread at 24ba26
 torvalds#51 [9a06fe40]  104 bytes  kthread at 26545a
 #52 [9a06fea8]             kernel_thread_starter at 21b6b62

To be able to increase the stack size to 64k reuse LLILL instruction
in __switch_to function to load 64k - STACK_FRAME_OVERHEAD - __PT_SIZE
(65192) value as unsigned.

Reported-by: Benjamin Block <bblock@linux.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Makefile

@@ -27,7 +27,7 @@ KBUILD_CFLAGS_DECOMPRESSOR += $(call cc-option,-ffreestanding)
 KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),-g)
 KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO_DWARF4), $(call cc-option, -gdwarf-4,))
 UTS_MACHINE	:= s390x
-STACK_SIZE	:= $(if $(CONFIG_KASAN),32768,16384)
+STACK_SIZE	:= $(if $(CONFIG_KASAN),65536,16384)
 CHECKFLAGS	+= -D__s390__ -D__s390x__
 
 export LD_BFD

arch/s390/include/asm/thread_info.h

@@ -14,7 +14,7 @@
  * General size of kernel stacks
  */
 #ifdef CONFIG_KASAN
-#define THREAD_SIZE_ORDER 3
+#define THREAD_SIZE_ORDER 4
 #else
 #define THREAD_SIZE_ORDER 2
 #endif

arch/s390/kernel/entry.S

@@ -236,10 +236,10 @@ ENTRY(__switch_to)
 	stmg	%r6,%r15,__SF_GPRS(%r15)	# store gprs of prev task
 	lghi	%r4,__TASK_stack
 	lghi	%r1,__TASK_thread
-	lg	%r5,0(%r4,%r3)			# start of kernel stack of next
+	llill	%r5,STACK_INIT
 	stg	%r15,__THREAD_ksp(%r1,%r2)	# store kernel stack of prev
-	lgr	%r15,%r5
-	aghi	%r15,STACK_INIT			# end of kernel stack of next
+	lg	%r15,0(%r4,%r3)			# start of kernel stack of next
+	agr	%r15,%r5			# 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,%r3)	# load kernel stack of next