s390/syscall: Merge __do_syscall() and do_syscall()

The compiler inlines do_syscall() into __do_syscall(). Therefore do this in
C code as well, since this makes the code easier to understand.

Also adjust and add various unlikely() and likely() annotations.

Furthermore this allows to replace the separate exit_to_user_mode() and
syscall_exit_to_user_mode_work() calls with a combined
syscall_exit_to_user_mode() call which results in slightly better code.

Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/arch/s390/kernel/syscall.c b/arch/s390/kernel/syscall.c
index c8df656b08bcf14d68cb999d022ed2e9454e0aca..535f3922ffa923102d8ca1c0d2eb3f37fb6a4dfe 100644 (file)
--- a/arch/s390/kernel/syscall.c
+++ b/arch/s390/kernel/syscall.c
@@ -82,25 +82,35 @@ SYSCALL_DEFINE0(ni_syscall)
        return -ENOSYS;
 }
 
-static void do_syscall(struct pt_regs *regs)
+void noinstr __do_syscall(struct pt_regs *regs, int per_trap)
 {
        unsigned long nr;
 
+       add_random_kstack_offset();
+       enter_from_user_mode(regs);
+       regs->psw = get_lowcore()->svc_old_psw;
+       regs->int_code = get_lowcore()->svc_int_code;
+       update_timer_sys();
+       if (cpu_has_bear())
+               current->thread.last_break = regs->last_break;
+       local_irq_enable();
+       regs->orig_gpr2 = regs->gprs[2];
+       if (unlikely(per_trap))
+               set_thread_flag(TIF_PER_TRAP);
+       regs->flags = 0;
+       set_pt_regs_flag(regs, PIF_SYSCALL);
        nr = regs->int_code & 0xffff;
-       if (!nr) {
+       if (likely(!nr)) {
                nr = regs->gprs[1] & 0xffff;
                regs->int_code &= ~0xffffUL;
                regs->int_code |= nr;
        }
-
        regs->gprs[2] = nr;
-
        if (nr == __NR_restart_syscall && !(current->restart_block.arch_data & 1)) {
                regs->psw.addr = current->restart_block.arch_data;
                current->restart_block.arch_data = 1;
        }
        nr = syscall_enter_from_user_mode_work(regs, nr);
-
        /*
         * In the s390 ptrace ABI, both the syscall number and the return value
         * use gpr2. However, userspace puts the syscall number either in the
@@ -108,37 +118,14 @@ static void do_syscall(struct pt_regs *regs)
         * work, the ptrace code sets PIF_SYSCALL_RET_SET, which is checked here
         * and if set, the syscall will be skipped.
         */
-
        if (unlikely(test_and_clear_pt_regs_flag(regs, PIF_SYSCALL_RET_SET)))
                goto out;
        regs->gprs[2] = -ENOSYS;
-       if (likely(nr >= NR_syscalls))
+       if (unlikely(nr >= NR_syscalls))
                goto out;
        do {
                regs->gprs[2] = current->thread.sys_call_table[nr](regs);
        } while (test_and_clear_pt_regs_flag(regs, PIF_EXECVE_PGSTE_RESTART));
 out:
-       syscall_exit_to_user_mode_work(regs);
-}
-
-void noinstr __do_syscall(struct pt_regs *regs, int per_trap)
-{
-       add_random_kstack_offset();
-       enter_from_user_mode(regs);
-       regs->psw = get_lowcore()->svc_old_psw;
-       regs->int_code = get_lowcore()->svc_int_code;
-       update_timer_sys();
-       if (cpu_has_bear())
-               current->thread.last_break = regs->last_break;
-
-       local_irq_enable();
-       regs->orig_gpr2 = regs->gprs[2];
-
-       if (per_trap)
-               set_thread_flag(TIF_PER_TRAP);
-
-       regs->flags = 0;
-       set_pt_regs_flag(regs, PIF_SYSCALL);
-       do_syscall(regs);
-       exit_to_user_mode();
+       syscall_exit_to_user_mode(regs);
 }