s390 fixes for 5.8-rc3

- Fix kernel crash on system call single stepping.
 
 - Make sure early program check handler is executed with DAT on to
   avoid an endless program check loop.
 
 - Add __GFP_NOWARN flag to debug feature to avoid user triggerable
   allocation failure messages.
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Merge tag 's390-5.8-3' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

Pull s390 fixes from Heiko Carstens:

 - Fix kernel crash on system call single stepping.

 - Make sure early program check handler is executed with DAT on to
   avoid an endless program check loop.

 - Add __GFP_NOWARN flag to debug feature to avoid user triggerable
   allocation failure messages.

* tag 's390-5.8-3' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/debug: avoid kernel warning on too large number of pages
  s390/kasan: fix early pgm check handler execution
  s390: fix system call single stepping

arch/s390/kernel/debug.c

@@ -198,9 +198,10 @@ static debug_entry_t ***debug_areas_alloc(int pages_per_area, int nr_areas)
 	if (!areas)
 		goto fail_malloc_areas;
 	for (i = 0; i < nr_areas; i++) {
+		/* GFP_NOWARN to avoid user triggerable WARN, we handle fails */
 		areas[i] = kmalloc_array(pages_per_area,
 					 sizeof(debug_entry_t *),
-					 GFP_KERNEL);
+					 GFP_KERNEL | __GFP_NOWARN);
 		if (!areas[i])
 			goto fail_malloc_areas2;
 		for (j = 0; j < pages_per_area; j++) {

arch/s390/kernel/early.c

@@ -170,6 +170,8 @@ static noinline __init void setup_lowcore_early(void)
 	psw_t psw;
 
 	psw.mask = PSW_MASK_BASE | PSW_DEFAULT_KEY | PSW_MASK_EA | PSW_MASK_BA;
+	if (IS_ENABLED(CONFIG_KASAN))
+		psw.mask |= PSW_MASK_DAT;
 	psw.addr = (unsigned long) s390_base_ext_handler;
 	S390_lowcore.external_new_psw = psw;
 	psw.addr = (unsigned long) s390_base_pgm_handler;

arch/s390/kernel/entry.S

@@ -378,9 +378,9 @@ ENTRY(system_call)
 	stmg	%r8,%r15,__LC_SAVE_AREA_SYNC
 	BPOFF
 	lg	%r12,__LC_CURRENT
-	lghi	%r13,__TASK_thread
 	lghi	%r14,_PIF_SYSCALL
 .Lsysc_per:
+	lghi	%r13,__TASK_thread
 	lg	%r15,__LC_KERNEL_STACK
 	la	%r11,STACK_FRAME_OVERHEAD(%r15)	# pointer to pt_regs
 	UPDATE_VTIME %r8,%r9,__LC_SYNC_ENTER_TIMER