s390: convert to generic entry

This patch converts s390 to use the generic entry infrastructure from
kernel/entry/*.

There are a few special things on s390:

- PIF_PER_TRAP is moved to TIF_PER_TRAP as the generic code doesn't
  know about our PIF flags in exit_to_user_mode_loop().

- The old code had several ways to restart syscalls:

  a) PIF_SYSCALL_RESTART, which was only set during execve to force a
     restart after upgrading a process (usually qemu-kvm) to pgste page
     table extensions.

  b) PIF_SYSCALL, which is set by do_signal() to indicate that the
     current syscall should be restarted. This is changed so that
     do_signal() now also uses PIF_SYSCALL_RESTART. Continuing to use
     PIF_SYSCALL doesn't work with the generic code, and changing it
     to PIF_SYSCALL_RESTART makes PIF_SYSCALL and PIF_SYSCALL_RESTART
     more unique.

- On s390 calling sys_sigreturn or sys_rt_sigreturn is implemented by
executing a svc instruction on the process stack which causes a fault.
While handling that fault the fault code sets PIF_SYSCALL to hand over
processing to the syscall code on exit to usermode.

The patch introduces PIF_SYSCALL_RET_SET, which is set if ptrace sets
a return value for a syscall. The s390x ptrace ABI uses r2 both for the
syscall number and return value, so ptrace cannot set the syscall number +
return value at the same time. The flag makes handling that a bit easier.
do_syscall() will just skip executing the syscall if PIF_SYSCALL_RET_SET
is set.

CONFIG_DEBUG_ASCE was removd in favour of the generic CONFIG_DEBUG_ENTRY.
CR1/7/13 will be checked both on kernel entry and exit to contain the
correct asces.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 12 insertions, 7 deletions

diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
index 86c8d5370e7f..11f8c296f60d 100644
--- a/arch/s390/kernel/nmi.c
+++ b/arch/s390/kernel/nmi.c
@@ -131,12 +131,11 @@ static notrace void s390_handle_damage(void)
 NOKPROBE_SYMBOL(s390_handle_damage);
 
 /*
- * Main machine check handler function. Will be called with interrupts enabled
- * or disabled and machine checks enabled or disabled.
+ * Main machine check handler function. Will be called with interrupts disabled
+ * and machine checks enabled.
  */
-void s390_handle_mcck(void)
+void __s390_handle_mcck(void)
 {
-	unsigned long flags;
 	struct mcck_struct mcck;
 
 	/*
@@ -144,12 +143,10 @@ void s390_handle_mcck(void)
 	 * machine checks. Afterwards delete the old state and enable machine
 	 * checks again.
 	 */
-	local_irq_save(flags);
 	local_mcck_disable();
 	mcck = *this_cpu_ptr(&cpu_mcck);
 	memset(this_cpu_ptr(&cpu_mcck), 0, sizeof(mcck));
 	local_mcck_enable();
-	local_irq_restore(flags);
 
 	if (mcck.channel_report)
 		crw_handle_channel_report();
@@ -181,8 +178,13 @@ void s390_handle_mcck(void)
 		do_exit(SIGSEGV);
 	}
 }
-EXPORT_SYMBOL_GPL(s390_handle_mcck);
 
+void noinstr s390_handle_mcck(void)
+{
+	trace_hardirqs_off();
+	__s390_handle_mcck();
+	trace_hardirqs_on();
+}
 /*
  * returns 0 if all required registers are available
  * returns 1 otherwise
@@ -344,6 +346,9 @@ int notrace s390_do_machine_check(struct pt_regs *regs)
 	int mcck_pending = 0;
 
 	nmi_enter();
+
+	if (user_mode(regs))
+		update_timer_mcck();
 	inc_irq_stat(NMI_NMI);
 	mci.val = S390_lowcore.mcck_interruption_code;
 	mcck = this_cpu_ptr(&cpu_mcck);