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, 65 insertions, 0 deletions

diff --git a/arch/s390/kernel/traps.c b/arch/s390/kernel/traps.c
index 8d1e8a1a97df..db7dd59b570c 100644
--- a/arch/s390/kernel/traps.c
+++ b/arch/s390/kernel/traps.c
@@ -13,6 +13,8 @@
  * 'Traps.c' handles hardware traps and faults after we have saved some
  * state in 'asm.s'.
  */
+#include "asm/irqflags.h"
+#include "asm/ptrace.h"
 #include <linux/kprobes.h>
 #include <linux/kdebug.h>
 #include <linux/extable.h>
@@ -23,7 +25,9 @@
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/cpu.h>
+#include <linux/entry-common.h>
 #include <asm/fpu/api.h>
+#include <asm/vtime.h>
 #include "entry.h"
 
 static inline void __user *get_trap_ip(struct pt_regs *regs)
@@ -288,3 +292,64 @@ void __init trap_init(void)
 	local_mcck_enable();
 	test_monitor_call();
 }
+
+void noinstr __do_pgm_check(struct pt_regs *regs)
+{
+	unsigned long last_break = S390_lowcore.breaking_event_addr;
+	unsigned int trapnr, syscall_redirect = 0;
+	irqentry_state_t state;
+
+	regs->int_code = *(u32 *)&S390_lowcore.pgm_ilc;
+	regs->int_parm_long = S390_lowcore.trans_exc_code;
+
+	state = irqentry_enter(regs);
+
+	if (user_mode(regs)) {
+		update_timer_sys();
+		if (last_break < 4096)
+			last_break = 1;
+		current->thread.last_break = last_break;
+		regs->args[0] = last_break;
+	}
+
+	if (S390_lowcore.pgm_code & 0x0200) {
+		/* transaction abort */
+		memcpy(&current->thread.trap_tdb, &S390_lowcore.pgm_tdb, 256);
+	}
+
+	if (S390_lowcore.pgm_code & PGM_INT_CODE_PER) {
+		if (user_mode(regs)) {
+			struct per_event *ev = &current->thread.per_event;
+
+			set_thread_flag(TIF_PER_TRAP);
+			ev->address = S390_lowcore.per_address;
+			ev->cause = *(u16 *)&S390_lowcore.per_code;
+			ev->paid = S390_lowcore.per_access_id;
+		} else {
+			/* PER event in kernel is kprobes */
+			__arch_local_irq_ssm(regs->psw.mask & ~PSW_MASK_PER);
+			do_per_trap(regs);
+			goto out;
+		}
+	}
+
+	if (!irqs_disabled_flags(regs->psw.mask))
+		trace_hardirqs_on();
+	__arch_local_irq_ssm(regs->psw.mask & ~PSW_MASK_PER);
+
+	trapnr = regs->int_code & PGM_INT_CODE_MASK;
+	if (trapnr)
+		pgm_check_table[trapnr](regs);
+	syscall_redirect = user_mode(regs) && test_pt_regs_flag(regs, PIF_SYSCALL);
+out:
+	local_irq_disable();
+	irqentry_exit(regs, state);
+
+	if (syscall_redirect) {
+		enter_from_user_mode(regs);
+		local_irq_enable();
+		regs->orig_gpr2 = regs->gprs[2];
+		do_syscall(regs);
+		exit_to_user_mode();
+	}
+}