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, 7 insertions, 5 deletions

diff --git a/arch/s390/lib/uaccess.c b/arch/s390/lib/uaccess.c
index e8f642446fed..2fece1fd210a 100644
--- a/arch/s390/lib/uaccess.c
+++ b/arch/s390/lib/uaccess.c
@@ -16,8 +16,8 @@
 #include <asm/mmu_context.h>
 #include <asm/facility.h>
 
-#ifdef CONFIG_DEBUG_USER_ASCE
-void debug_user_asce(void)
+#ifdef CONFIG_DEBUG_ENTRY
+void debug_user_asce(int exit)
 {
 	unsigned long cr1, cr7;
 
@@ -25,12 +25,14 @@ void debug_user_asce(void)
 	__ctl_store(cr7, 7, 7);
 	if (cr1 == S390_lowcore.kernel_asce && cr7 == S390_lowcore.user_asce)
 		return;
-	panic("incorrect ASCE on kernel exit\n"
+	panic("incorrect ASCE on kernel %s\n"
 	      "cr1:    %016lx cr7:  %016lx\n"
 	      "kernel: %016llx user: %016llx\n",
-	      cr1, cr7, S390_lowcore.kernel_asce, S390_lowcore.user_asce);
+	      exit ? "exit" : "entry", cr1, cr7,
+	      S390_lowcore.kernel_asce, S390_lowcore.user_asce);
+
 }
-#endif /*CONFIG_DEBUG_USER_ASCE */
+#endif /*CONFIG_DEBUG_ENTRY */
 
 #ifndef CONFIG_HAVE_MARCH_Z10_FEATURES
 static DEFINE_STATIC_KEY_FALSE(have_mvcos);