signal.c

/*  $Id: signal.c,v 1.60 2002/02/09 19:49:31 davem Exp $
 *  arch/sparc64/kernel/signal.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
 *  Copyright (C) 1996 Miguel de Icaza (miguel@nuclecu.unam.mx)
 *  Copyright (C) 1997 Eddie C. Dost   (ecd@skynet.be)
 *  Copyright (C) 1997,1998 Jakub Jelinek   (jj@sunsite.mff.cuni.cz)
 */

#ifdef CONFIG_SPARC32_COMPAT
#include <linux/compat.h>	/* for compat_old_sigset_t */
#endif
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/mm.h>
#include <linux/tty.h>
#include <linux/binfmts.h>
#include <linux/bitops.h>

#include <asm/uaccess.h>
#include <asm/ptrace.h>
#include <asm/pgtable.h>
#include <asm/fpumacro.h>
#include <asm/uctx.h>
#include <asm/siginfo.h>
#include <asm/visasm.h>

#include "entry.h"
#include "systbls.h"

#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))

/* {set, get}context() needed for 64-bit SparcLinux userland. */
asmlinkage void sparc64_set_context(struct pt_regs *regs)
{
	struct ucontext __user *ucp = (struct ucontext __user *)
		regs->u_regs[UREG_I0];
	mc_gregset_t __user *grp;
	unsigned long pc, npc, tstate;
	unsigned long fp, i7;
	unsigned char fenab;
	int err;

	flush_user_windows();
	if (get_thread_wsaved()					||
	    (((unsigned long)ucp) & (sizeof(unsigned long)-1))	||
	    (!__access_ok(ucp, sizeof(*ucp))))
		goto do_sigsegv;
	grp  = &ucp->uc_mcontext.mc_gregs;
	err  = __get_user(pc, &((*grp)[MC_PC]));
	err |= __get_user(npc, &((*grp)[MC_NPC]));
	if (err || ((pc | npc) & 3))
		goto do_sigsegv;
	if (regs->u_regs[UREG_I1]) {
		sigset_t set;

		if (_NSIG_WORDS == 1) {
			if (__get_user(set.sig[0], &ucp->uc_sigmask.sig[0]))
				goto do_sigsegv;
		} else {
			if (__copy_from_user(&set, &ucp->uc_sigmask, sizeof(sigset_t)))
				goto do_sigsegv;
		}
		sigdelsetmask(&set, ~_BLOCKABLE);
		spin_lock_irq(&current->sighand->siglock);
		current->blocked = set;
		recalc_sigpending();
		spin_unlock_irq(&current->sighand->siglock);
	}
	if (test_thread_flag(TIF_32BIT)) {
		pc &= 0xffffffff;
		npc &= 0xffffffff;
	}
	regs->tpc = pc;
	regs->tnpc = npc;
	err |= __get_user(regs->y, &((*grp)[MC_Y]));
	err |= __get_user(tstate, &((*grp)[MC_TSTATE]));
	regs->tstate &= ~(TSTATE_ASI | TSTATE_ICC | TSTATE_XCC);
	regs->tstate |= (tstate & (TSTATE_ASI | TSTATE_ICC | TSTATE_XCC));
	err |= __get_user(regs->u_regs[UREG_G1], (&(*grp)[MC_G1]));
	err |= __get_user(regs->u_regs[UREG_G2], (&(*grp)[MC_G2]));
	err |= __get_user(regs->u_regs[UREG_G3], (&(*grp)[MC_G3]));
	err |= __get_user(regs->u_regs[UREG_G4], (&(*grp)[MC_G4]));
	err |= __get_user(regs->u_regs[UREG_G5], (&(*grp)[MC_G5]));
	err |= __get_user(regs->u_regs[UREG_G6], (&(*grp)[MC_G6]));
	err |= __get_user(regs->u_regs[UREG_G7], (&(*grp)[MC_G7]));
	err |= __get_user(regs->u_regs[UREG_I0], (&(*grp)[MC_O0]));
	err |= __get_user(regs->u_regs[UREG_I1], (&(*grp)[MC_O1]));
	err |= __get_user(regs->u_regs[UREG_I2], (&(*grp)[MC_O2]));
	err |= __get_user(regs->u_regs[UREG_I3], (&(*grp)[MC_O3]));
	err |= __get_user(regs->u_regs[UREG_I4], (&(*grp)[MC_O4]));
	err |= __get_user(regs->u_regs[UREG_I5], (&(*grp)[MC_O5]));
	err |= __get_user(regs->u_regs[UREG_I6], (&(*grp)[MC_O6]));
	err |= __get_user(regs->u_regs[UREG_I7], (&(*grp)[MC_O7]));

	err |= __get_user(fp, &(ucp->uc_mcontext.mc_fp));
	err |= __get_user(i7, &(ucp->uc_mcontext.mc_i7));
	err |= __put_user(fp,
	      (&(((struct reg_window __user *)(STACK_BIAS+regs->u_regs[UREG_I6]))->ins[6])));
	err |= __put_user(i7,
	      (&(((struct reg_window __user *)(STACK_BIAS+regs->u_regs[UREG_I6]))->ins[7])));

	err |= __get_user(fenab, &(ucp->uc_mcontext.mc_fpregs.mcfpu_enab));
	if (fenab) {
		unsigned long *fpregs = current_thread_info()->fpregs;
		unsigned long fprs;
		
		fprs_write(0);
		err |= __get_user(fprs, &(ucp->uc_mcontext.mc_fpregs.mcfpu_fprs));
		if (fprs & FPRS_DL)
			err |= copy_from_user(fpregs,
					      &(ucp->uc_mcontext.mc_fpregs.mcfpu_fregs),
					      (sizeof(unsigned int) * 32));
		if (fprs & FPRS_DU)
			err |= copy_from_user(fpregs+16,
			 ((unsigned long __user *)&(ucp->uc_mcontext.mc_fpregs.mcfpu_fregs))+16,
			 (sizeof(unsigned int) * 32));
		err |= __get_user(current_thread_info()->xfsr[0],
				  &(ucp->uc_mcontext.mc_fpregs.mcfpu_fsr));
		err |= __get_user(current_thread_info()->gsr[0],
				  &(ucp->uc_mcontext.mc_fpregs.mcfpu_gsr));
		regs->tstate &= ~TSTATE_PEF;
	}
	if (err)
		goto do_sigsegv;

	return;
do_sigsegv:
	force_sig(SIGSEGV, current);
}

asmlinkage void sparc64_get_context(struct pt_regs *regs)
{
	struct ucontext __user *ucp = (struct ucontext __user *)
		regs->u_regs[UREG_I0];
	mc_gregset_t __user *grp;
	mcontext_t __user *mcp;
	unsigned long fp, i7;
	unsigned char fenab;
	int err;

	synchronize_user_stack();
	if (get_thread_wsaved() || clear_user(ucp, sizeof(*ucp)))
		goto do_sigsegv;

#if 1
	fenab = 0; /* IMO get_context is like any other system call, thus modifies FPU state -jj */
#else
	fenab = (current_thread_info()->fpsaved[0] & FPRS_FEF);
#endif
		
	mcp = &ucp->uc_mcontext;
	grp = &mcp->mc_gregs;

	/* Skip over the trap instruction, first. */
	if (test_thread_flag(TIF_32BIT)) {
		regs->tpc   = (regs->tnpc & 0xffffffff);
		regs->tnpc  = (regs->tnpc + 4) & 0xffffffff;
	} else {
		regs->tpc   = regs->tnpc;
		regs->tnpc += 4;
	}
	err = 0;
	if (_NSIG_WORDS == 1)
		err |= __put_user(current->blocked.sig[0],
				  (unsigned long __user *)&ucp->uc_sigmask);
	else
		err |= __copy_to_user(&ucp->uc_sigmask, &current->blocked,
				      sizeof(sigset_t));

	err |= __put_user(regs->tstate, &((*grp)[MC_TSTATE]));
	err |= __put_user(regs->tpc, &((*grp)[MC_PC]));
	err |= __put_user(regs->tnpc, &((*grp)[MC_NPC]));
	err |= __put_user(regs->y, &((*grp)[MC_Y]));
	err |= __put_user(regs->u_regs[UREG_G1], &((*grp)[MC_G1]));
	err |= __put_user(regs->u_regs[UREG_G2], &((*grp)[MC_G2]));
	err |= __put_user(regs->u_regs[UREG_G3], &((*grp)[MC_G3]));
	err |= __put_user(regs->u_regs[UREG_G4], &((*grp)[MC_G4]));
	err |= __put_user(regs->u_regs[UREG_G5], &((*grp)[MC_G5]));
	err |= __put_user(regs->u_regs[UREG_G6], &((*grp)[MC_G6]));
	err |= __put_user(regs->u_regs[UREG_G7], &((*grp)[MC_G7]));
	err |= __put_user(regs->u_regs[UREG_I0], &((*grp)[MC_O0]));
	err |= __put_user(regs->u_regs[UREG_I1], &((*grp)[MC_O1]));
	err |= __put_user(regs->u_regs[UREG_I2], &((*grp)[MC_O2]));
	err |= __put_user(regs->u_regs[UREG_I3], &((*grp)[MC_O3]));
	err |= __put_user(regs->u_regs[UREG_I4], &((*grp)[MC_O4]));
	err |= __put_user(regs->u_regs[UREG_I5], &((*grp)[MC_O5]));
	err |= __put_user(regs->u_regs[UREG_I6], &((*grp)[MC_O6]));
	err |= __put_user(regs->u_regs[UREG_I7], &((*grp)[MC_O7]));

	err |= __get_user(fp,
		 (&(((struct reg_window __user *)(STACK_BIAS+regs->u_regs[UREG_I6]))->ins[6])));
	err |= __get_user(i7,
		 (&(((struct reg_window __user *)(STACK_BIAS+regs->u_regs[UREG_I6]))->ins[7])));
	err |= __put_user(fp, &(mcp->mc_fp));
	err |= __put_user(i7, &(mcp->mc_i7));

	err |= __put_user(fenab, &(mcp->mc_fpregs.mcfpu_enab));
	if (fenab) {
		unsigned long *fpregs = current_thread_info()->fpregs;
		unsigned long fprs;
		
		fprs = current_thread_info()->fpsaved[0];
		if (fprs & FPRS_DL)
			err |= copy_to_user(&(mcp->mc_fpregs.mcfpu_fregs), fpregs,
					    (sizeof(unsigned int) * 32));
		if (fprs & FPRS_DU)
			err |= copy_to_user(
                          ((unsigned long __user *)&(mcp->mc_fpregs.mcfpu_fregs))+16, fpregs+16,
			  (sizeof(unsigned int) * 32));
		err |= __put_user(current_thread_info()->xfsr[0], &(mcp->mc_fpregs.mcfpu_fsr));
		err |= __put_user(current_thread_info()->gsr[0], &(mcp->mc_fpregs.mcfpu_gsr));
		err |= __put_user(fprs, &(mcp->mc_fpregs.mcfpu_fprs));
	}
	if (err)
		goto do_sigsegv;

	return;
do_sigsegv:
	force_sig(SIGSEGV, current);
}

struct rt_signal_frame {
	struct sparc_stackf	ss;
	siginfo_t		info;
	struct pt_regs		regs;
	__siginfo_fpu_t __user	*fpu_save;
	stack_t			stack;
	sigset_t		mask;
	__siginfo_fpu_t		fpu_state;
};

/* Align macros */
#define RT_ALIGNEDSZ  (((sizeof(struct rt_signal_frame) + 7) & (~7)))

static long _sigpause_common(old_sigset_t set)
{
	set &= _BLOCKABLE;
	spin_lock_irq(&current->sighand->siglock);
	current->saved_sigmask = current->blocked;
	siginitset(&current->blocked, set);
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

	current->state = TASK_INTERRUPTIBLE;
	schedule();
	set_thread_flag(TIF_RESTORE_SIGMASK);
	return -ERESTARTNOHAND;
}

asmlinkage long sys_sigpause(unsigned int set)
{
	return _sigpause_common(set);
}

asmlinkage long sys_sigsuspend(old_sigset_t set)
{
	return _sigpause_common(set);
}

static inline int
restore_fpu_state(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
{
	unsigned long *fpregs = current_thread_info()->fpregs;
	unsigned long fprs;
	int err;

	err = __get_user(fprs, &fpu->si_fprs);
	fprs_write(0);
	regs->tstate &= ~TSTATE_PEF;
	if (fprs & FPRS_DL)
		err |= copy_from_user(fpregs, &fpu->si_float_regs[0],
		       	       (sizeof(unsigned int) * 32));
	if (fprs & FPRS_DU)
		err |= copy_from_user(fpregs+16, &fpu->si_float_regs[32],
		       	       (sizeof(unsigned int) * 32));
	err |= __get_user(current_thread_info()->xfsr[0], &fpu->si_fsr);
	err |= __get_user(current_thread_info()->gsr[0], &fpu->si_gsr);
	current_thread_info()->fpsaved[0] |= fprs;
	return err;
}

void do_rt_sigreturn(struct pt_regs *regs)
{
	struct rt_signal_frame __user *sf;
	unsigned long tpc, tnpc, tstate;
	__siginfo_fpu_t __user *fpu_save;
	sigset_t set;
	int err;

	/* Always make any pending restarted system calls return -EINTR */
	current_thread_info()->restart_block.fn = do_no_restart_syscall;

	synchronize_user_stack ();
	sf = (struct rt_signal_frame __user *)
		(regs->u_regs [UREG_FP] + STACK_BIAS);

	/* 1. Make sure we are not getting garbage from the user */
	if (((unsigned long) sf) & 3)
		goto segv;

	err = get_user(tpc, &sf->regs.tpc);
	err |= __get_user(tnpc, &sf->regs.tnpc);
	if (test_thread_flag(TIF_32BIT)) {
		tpc &= 0xffffffff;
		tnpc &= 0xffffffff;
	}
	err |= ((tpc | tnpc) & 3);

	/* 2. Restore the state */
	err |= __get_user(regs->y, &sf->regs.y);
	err |= __get_user(tstate, &sf->regs.tstate);
	err |= copy_from_user(regs->u_regs, sf->regs.u_regs, sizeof(regs->u_regs));

	/* User can only change condition codes and %asi in %tstate. */
	regs->tstate &= ~(TSTATE_ASI | TSTATE_ICC | TSTATE_XCC);
	regs->tstate |= (tstate & (TSTATE_ASI | TSTATE_ICC | TSTATE_XCC));

	err |= __get_user(fpu_save, &sf->fpu_save);
	if (fpu_save)
		err |= restore_fpu_state(regs, &sf->fpu_state);

	err |= __copy_from_user(&set, &sf->mask, sizeof(sigset_t));
	err |= do_sigaltstack(&sf->stack, NULL, (unsigned long)sf);

	if (err)
		goto segv;

	regs->tpc = tpc;
	regs->tnpc = tnpc;

	sigdelsetmask(&set, ~_BLOCKABLE);
	spin_lock_irq(&current->sighand->siglock);
	current->blocked = set;
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);
	return;
segv:
	force_sig(SIGSEGV, current);
}

/* Checks if the fp is valid */
static int invalid_frame_pointer(void __user *fp, int fplen)
{
	if (((unsigned long) fp) & 7)
		return 1;
	return 0;
}

static inline int
save_fpu_state(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
{
	unsigned long *fpregs = current_thread_info()->fpregs;
	unsigned long fprs;
	int err = 0;
	
	fprs = current_thread_info()->fpsaved[0];
	if (fprs & FPRS_DL)
		err |= copy_to_user(&fpu->si_float_regs[0], fpregs,
				    (sizeof(unsigned int) * 32));
	if (fprs & FPRS_DU)
		err |= copy_to_user(&fpu->si_float_regs[32], fpregs+16,
				    (sizeof(unsigned int) * 32));
	err |= __put_user(current_thread_info()->xfsr[0], &fpu->si_fsr);
	err |= __put_user(current_thread_info()->gsr[0], &fpu->si_gsr);
	err |= __put_user(fprs, &fpu->si_fprs);

	return err;
}

static inline void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, unsigned long framesize)
{
	unsigned long sp;

	sp = regs->u_regs[UREG_FP] + STACK_BIAS;

	/* This is the X/Open sanctioned signal stack switching.  */
	if (ka->sa.sa_flags & SA_ONSTACK) {
		if (!on_sig_stack(sp) &&
		    !((current->sas_ss_sp + current->sas_ss_size) & 7))
			sp = current->sas_ss_sp + current->sas_ss_size;
	}
	return (void __user *)(sp - framesize);
}

static inline void
setup_rt_frame(struct k_sigaction *ka, struct pt_regs *regs,
	       int signo, sigset_t *oldset, siginfo_t *info)
{
	struct rt_signal_frame __user *sf;
	int sigframe_size, err;

	/* 1. Make sure everything is clean */
	synchronize_user_stack();
	save_and_clear_fpu();
	
	sigframe_size = RT_ALIGNEDSZ;
	if (!(current_thread_info()->fpsaved[0] & FPRS_FEF))
		sigframe_size -= sizeof(__siginfo_fpu_t);

	sf = (struct rt_signal_frame __user *)
		get_sigframe(ka, regs, sigframe_size);
	
	if (invalid_frame_pointer (sf, sigframe_size))
		goto sigill;

	if (get_thread_wsaved() != 0)
		goto sigill;

	/* 2. Save the current process state */
	err = copy_to_user(&sf->regs, regs, sizeof (*regs));

	if (current_thread_info()->fpsaved[0] & FPRS_FEF) {
		err |= save_fpu_state(regs, &sf->fpu_state);
		err |= __put_user((u64)&sf->fpu_state, &sf->fpu_save);
	} else {
		err |= __put_user(0, &sf->fpu_save);
	}
	
	/* Setup sigaltstack */
	err |= __put_user(current->sas_ss_sp, &sf->stack.ss_sp);
	err |= __put_user(sas_ss_flags(regs->u_regs[UREG_FP]), &sf->stack.ss_flags);
	err |= __put_user(current->sas_ss_size, &sf->stack.ss_size);

	err |= copy_to_user(&sf->mask, oldset, sizeof(sigset_t));

	err |= copy_in_user((u64 __user *)sf,
			    (u64 __user *)(regs->u_regs[UREG_FP]+STACK_BIAS),
			    sizeof(struct reg_window));

	if (info)
		err |= copy_siginfo_to_user(&sf->info, info);
	else {
		err |= __put_user(signo, &sf->info.si_signo);
		err |= __put_user(SI_NOINFO, &sf->info.si_code);
	}
	if (err)
		goto sigsegv;
	
	/* 3. signal handler back-trampoline and parameters */
	regs->u_regs[UREG_FP] = ((unsigned long) sf) - STACK_BIAS;
	regs->u_regs[UREG_I0] = signo;
	regs->u_regs[UREG_I1] = (unsigned long) &sf->info;

	/* The sigcontext is passed in this way because of how it
	 * is defined in GLIBC's /usr/include/bits/sigcontext.h
	 * for sparc64.  It includes the 128 bytes of siginfo_t.
	 */
	regs->u_regs[UREG_I2] = (unsigned long) &sf->info;

	/* 5. signal handler */
	regs->tpc = (unsigned long) ka->sa.sa_handler;
	regs->tnpc = (regs->tpc + 4);
	if (test_thread_flag(TIF_32BIT)) {
		regs->tpc &= 0xffffffff;
		regs->tnpc &= 0xffffffff;
	}
	/* 4. return to kernel instructions */
	regs->u_regs[UREG_I7] = (unsigned long)ka->ka_restorer;
	return;

sigill:
	do_exit(SIGILL);
sigsegv:
	force_sigsegv(signo, current);
}

static inline void handle_signal(unsigned long signr, struct k_sigaction *ka,
				 siginfo_t *info,
				 sigset_t *oldset, struct pt_regs *regs)
{
	setup_rt_frame(ka, regs, signr, oldset,
		       (ka->sa.sa_flags & SA_SIGINFO) ? info : NULL);
	spin_lock_irq(&current->sighand->siglock);
	sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
	if (!(ka->sa.sa_flags & SA_NOMASK))
		sigaddset(&current->blocked,signr);
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);
}

static inline void syscall_restart(unsigned long orig_i0, struct pt_regs *regs,
				     struct sigaction *sa)
{
	switch (regs->u_regs[UREG_I0]) {
	case ERESTART_RESTARTBLOCK:
	case ERESTARTNOHAND:
	no_system_call_restart:
		regs->u_regs[UREG_I0] = EINTR;
		regs->tstate |= (TSTATE_ICARRY|TSTATE_XCARRY);
		break;
	case ERESTARTSYS:
		if (!(sa->sa_flags & SA_RESTART))
			goto no_system_call_restart;
		/* fallthrough */
	case ERESTARTNOINTR:
		regs->u_regs[UREG_I0] = orig_i0;
		regs->tpc -= 4;
		regs->tnpc -= 4;
	}
}

/* Note that 'init' is a special process: it doesn't get signals it doesn't
 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 * mistake.
 */
static void do_signal(struct pt_regs *regs, unsigned long orig_i0, int restart_syscall)
{
	siginfo_t info;
	struct signal_deliver_cookie cookie;
	struct k_sigaction ka;
	int signr;
	sigset_t *oldset;
	
	cookie.restart_syscall = restart_syscall;
	cookie.orig_i0 = orig_i0;

	if (test_thread_flag(TIF_RESTORE_SIGMASK))
		oldset = &current->saved_sigmask;
	else
		oldset = &current->blocked;

#ifdef CONFIG_SPARC32_COMPAT
	if (test_thread_flag(TIF_32BIT)) {
		extern void do_signal32(sigset_t *, struct pt_regs *,
					unsigned long, int);
		do_signal32(oldset, regs, orig_i0,
			    cookie.restart_syscall);
		return;
	}
#endif	

	signr = get_signal_to_deliver(&info, &ka, regs, &cookie);
	if (signr > 0) {
		if (cookie.restart_syscall)
			syscall_restart(orig_i0, regs, &ka.sa);
		handle_signal(signr, &ka, &info, oldset, regs);

		/* a signal was successfully delivered; the saved
		 * sigmask will have been stored in the signal frame,
		 * and will be restored by sigreturn, so we can simply
		 * clear the TIF_RESTORE_SIGMASK flag.
		 */
		if (test_thread_flag(TIF_RESTORE_SIGMASK))
			clear_thread_flag(TIF_RESTORE_SIGMASK);
		return;
	}
	if (cookie.restart_syscall &&
	    (regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
	     regs->u_regs[UREG_I0] == ERESTARTSYS ||
	     regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
		/* replay the system call when we are done */
		regs->u_regs[UREG_I0] = cookie.orig_i0;
		regs->tpc -= 4;
		regs->tnpc -= 4;
	}
	if (cookie.restart_syscall &&
	    regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) {
		regs->u_regs[UREG_G1] = __NR_restart_syscall;
		regs->tpc -= 4;
		regs->tnpc -= 4;
	}

	/* if there's no signal to deliver, we just put the saved sigmask
	 * back
	 */
	if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
		clear_thread_flag(TIF_RESTORE_SIGMASK);
		sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
	}
}

void do_notify_resume(struct pt_regs *regs, unsigned long orig_i0, int restart_syscall,
		      unsigned long thread_info_flags)
{
	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
		do_signal(regs, orig_i0, restart_syscall);
}

void ptrace_signal_deliver(struct pt_regs *regs, void *cookie)
{
	struct signal_deliver_cookie *cp = cookie;

	if (cp->restart_syscall &&
	    (regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
	     regs->u_regs[UREG_I0] == ERESTARTSYS ||
	     regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
		/* replay the system call when we are done */
		regs->u_regs[UREG_I0] = cp->orig_i0;
		regs->tpc -= 4;
		regs->tnpc -= 4;
		cp->restart_syscall = 0;
	}
	if (cp->restart_syscall &&
	    regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) {
		regs->u_regs[UREG_G1] = __NR_restart_syscall;
		regs->tpc -= 4;
		regs->tnpc -= 4;
		cp->restart_syscall = 0;
	}
}