From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: s390: add ppa to system call and program check path
References: bsc#1068032
Patch-mainline: Not yet, under development

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
---
 arch/s390/include/asm/processor.h |    1 
 arch/s390/kernel/alternative.c    |   13 ++++++++++
 arch/s390/kernel/entry.S          |   47 ++++++++++++++++++++++++++++++++++++++
 arch/s390/kernel/ipl.c            |    1 
 arch/s390/kernel/smp.c            |    2 +
 arch/s390/kernel/vmlinux.lds.S    |    3 ++
 6 files changed, 67 insertions(+)

--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -88,6 +88,7 @@ void cpu_detect_mhz_feature(void);
 extern const struct seq_operations cpuinfo_op;
 extern int sysctl_ieee_emulation_warnings;
 extern void execve_tail(void);
+extern void __bpon(void);
 
 /*
  * User space process size: 2GB for 31 bit, 4TB or 8PT for 64 bit.
--- a/arch/s390/kernel/alternative.c
+++ b/arch/s390/kernel/alternative.c
@@ -14,6 +14,19 @@ static int __init disable_alternative_in
 
 early_param("noaltinstr", disable_alternative_instructions);
 
+extern struct alt_instr __alt_nobp[], __alt_nobp_end[];
+static int __init nobp_setup(char *str)
+{
+	bool enabled;
+	int rc;
+
+	rc = kstrtobool(str, &enabled);
+	if (!rc && enabled)
+		apply_alternatives(__alt_nobp, __alt_nobp_end);
+	return rc;
+}
+__setup("nobp=", nobp_setup);
+
 struct brcl_insn {
 	u16 opc;
 	s32 disp;
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -157,6 +157,34 @@ _PIF_WORK	= (_PIF_PER_TRAP)
 		tm	off+\addr, \mask
 	.endm
 
+	.macro BPOFF
+	.pushsection .altinstr_replacement, "ax"
+660:	.long	0xb2e8c000
+	.popsection
+661:	.long	0x47000000
+	.pushsection .altnobp, "a"
+	.long 661b - .
+	.long 660b - .
+	.word 82
+	.byte 4
+	.byte 4
+	.popsection
+	.endm
+
+	.macro BPON
+	.pushsection .altinstr_replacement, "ax"
+662:	.long	0xb2e8d000
+	.popsection
+663:	.long	0x47000000
+	.pushsection .altnobp, "a"
+	.long 663b - .
+	.long 662b - .
+	.word 82
+	.byte 4
+	.byte 4
+	.popsection
+	.endm
+
 	.section .kprobes.text, "ax"
 .Ldummy:
 	/*
@@ -169,6 +197,11 @@ _PIF_WORK	= (_PIF_PER_TRAP)
 	 */
 	nop	0
 
+ENTRY(__bpon)
+	.globl __bpon
+	BPON
+	br	%r14
+
 /*
  * Scheduler resume function, called by switch_to
  *  gpr2 = (task_struct *) prev
@@ -225,9 +258,11 @@ ENTRY(sie64a)
 	jnz	.Lsie_skip
 	TSTMSK	__LC_CPU_FLAGS,_CIF_FPU
 	jo	.Lsie_skip			# exit if fp/vx regs changed
+	BPON
 .Lsie_entry:
 	sie	0(%r14)
 .Lsie_skip:
+	BPOFF
 	ni	__SIE_PROG0C+3(%r14),0xfe	# no longer in SIE
 	lctlg	%c1,%c1,__LC_USER_ASCE		# load primary asce
 .Lsie_done:
@@ -270,6 +305,7 @@ EXPORT_SYMBOL(sie_exit)
 
 ENTRY(system_call)
 	stpt	__LC_SYNC_ENTER_TIMER
+	BPOFF
 .Lsysc_stmg:
 	stmg	%r8,%r15,__LC_SAVE_AREA_SYNC
 	lg	%r12,__LC_CURRENT
@@ -316,6 +352,7 @@ ENTRY(system_call)
 	jnz	.Lsysc_work			# check for work
 	TSTMSK	__LC_CPU_FLAGS,_CIF_WORK
 	jnz	.Lsysc_work
+	BPON
 .Lsysc_restore:
 	lg	%r14,__LC_VDSO_PER_CPU
 	lmg	%r0,%r10,__PT_R0(%r11)
@@ -500,6 +537,7 @@ ENTRY(kernel_thread_starter)
 
 ENTRY(pgm_check_handler)
 	stpt	__LC_SYNC_ENTER_TIMER
+	BPOFF
 	stmg	%r8,%r15,__LC_SAVE_AREA_SYNC
 	lg	%r10,__LC_LAST_BREAK
 	lg	%r12,__LC_CURRENT
@@ -595,6 +633,7 @@ ENTRY(pgm_check_handler)
 ENTRY(io_int_handler)
 	STCK	__LC_INT_CLOCK
 	stpt	__LC_ASYNC_ENTER_TIMER
+	BPOFF
 	stmg	%r8,%r15,__LC_SAVE_AREA_ASYNC
 	lg	%r12,__LC_CURRENT
 	larl	%r13,cleanup_critical
@@ -635,9 +674,13 @@ ENTRY(io_int_handler)
 	lg	%r14,__LC_VDSO_PER_CPU
 	lmg	%r0,%r10,__PT_R0(%r11)
 	mvc	__LC_RETURN_PSW(16),__PT_PSW(%r11)
+	tm	__PT_PSW+1(%r11),0x01	# returning to user ?
+	jno	.Lio_exit_timer
+	BPON
 .Lio_exit_timer:
 	stpt	__LC_EXIT_TIMER
 	mvc	__VDSO_ECTG_BASE(16,%r14),__LC_EXIT_TIMER
+.Lio_exit_kernel:
 	lmg	%r11,%r15,__PT_R11(%r11)
 	lpswe	__LC_RETURN_PSW
 .Lio_done:
@@ -800,6 +843,7 @@ ENTRY(io_int_handler)
 ENTRY(ext_int_handler)
 	STCK	__LC_INT_CLOCK
 	stpt	__LC_ASYNC_ENTER_TIMER
+	BPOFF
 	stmg	%r8,%r15,__LC_SAVE_AREA_ASYNC
 	lg	%r12,__LC_CURRENT
 	larl	%r13,cleanup_critical
@@ -838,6 +882,7 @@ ENTRY(psw_idle)
 .Lpsw_idle_stcctm:
 #endif
 	oi	__LC_CPU_FLAGS+7,_CIF_ENABLED_WAIT
+	BPON
 	STCK	__CLOCK_IDLE_ENTER(%r2)
 	stpt	__TIMER_IDLE_ENTER(%r2)
 .Lpsw_idle_lpsw:
@@ -940,6 +985,7 @@ load_fpu_regs:
  */
 ENTRY(mcck_int_handler)
 	STCK	__LC_MCCK_CLOCK
+	BPOFF
 	la	%r1,4095		# revalidate r1
 	spt	__LC_CPU_TIMER_SAVE_AREA-4095(%r1)	# revalidate cpu timer
 	lmg	%r0,%r15,__LC_GPREGS_SAVE_AREA-4095(%r1)# revalidate gprs
@@ -995,6 +1041,7 @@ ENTRY(mcck_int_handler)
 	mvc	__LC_RETURN_MCCK_PSW(16),__PT_PSW(%r11) # move return PSW
 	tm	__LC_RETURN_MCCK_PSW+1,0x01 # returning to user ?
 	jno	0f
+	BPON
 	stpt	__LC_EXIT_TIMER
 	mvc	__VDSO_ECTG_BASE(16,%r14),__LC_EXIT_TIMER
 0:	lmg	%r11,%r15,__PT_R11(%r11)
--- a/arch/s390/kernel/ipl.c
+++ b/arch/s390/kernel/ipl.c
@@ -564,6 +564,7 @@ static struct kset *ipl_kset;
 
 static void __ipl_run(void *unused)
 {
+	__bpon();
 	diag308(DIAG308_LOAD_CLEAR, NULL);
 	if (MACHINE_IS_VM)
 		__cpcmd("IPL", NULL, 0, NULL);
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -327,6 +327,7 @@ static void pcpu_delegate(struct pcpu *p
 	mem_assign_absolute(lc->restart_fn, (unsigned long) func);
 	mem_assign_absolute(lc->restart_data, (unsigned long) data);
 	mem_assign_absolute(lc->restart_source, source_cpu);
+	__bpon();
 	asm volatile(
 		"0:	sigp	0,%0,%2	# sigp restart to target cpu\n"
 		"	brc	2,0b	# busy, try again\n"
@@ -902,6 +903,7 @@ void __cpu_die(unsigned int cpu)
 void __noreturn cpu_die(void)
 {
 	idle_task_exit();
+	__bpon();
 	pcpu_sigp_retry(pcpu_devices + smp_processor_id(), SIGP_STOP, 0);
 	for (;;) ;
 }
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -115,6 +115,9 @@ SECTIONS
 		__alt_instructions = .;
 		*(.altinstructions)
 		__alt_instructions_end = .;
+		__alt_nobp = .;
+		*(.altnobp)
+		__alt_nobp_end = .;
 	}
 
 	/*