signal.c

/*
 *  linux/arch/alpha/kernel/signal.c
 *
 *  Copyright (C) 1995  Linus Torvalds
 *
 *  1997-11-02  Modified for POSIX.1b signals by Richard Henderson
 */

#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/smp.h>
#include <linux/stddef.h>
#include <linux/tty.h>
#include <linux/binfmts.h>
#include <linux/bitops.h>
#include <linux/syscalls.h>
#include <linux/tracehook.h>

#include <asm/uaccess.h>
#include <asm/sigcontext.h>
#include <asm/ucontext.h>

#include "proto.h"


#define DEBUG_SIG 0

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

asmlinkage void ret_from_sys_call(void);
static void do_signal(struct pt_regs *, struct switch_stack *,
		      unsigned long, unsigned long);


/*
 * The OSF/1 sigprocmask calling sequence is different from the
 * C sigprocmask() sequence..
 */
SYSCALL_DEFINE2(osf_sigprocmask, int, how, unsigned long, newmask)
{
	sigset_t oldmask;
	sigset_t mask;
	unsigned long res;

	siginitset(&mask, newmask & _BLOCKABLE);
	res = sigprocmask(how, &mask, &oldmask);
	if (!res) {
		force_successful_syscall_return();
		res = oldmask.sig[0];
	}
	return res;
}

SYSCALL_DEFINE3(osf_sigaction, int, sig,
		const struct osf_sigaction __user *, act,
		struct osf_sigaction __user *, oact)
{
	struct k_sigaction new_ka, old_ka;
	int ret;

	if (act) {
		old_sigset_t mask;
		if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
		    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
		    __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
		    __get_user(mask, &act->sa_mask))
			return -EFAULT;
		siginitset(&new_ka.sa.sa_mask, mask);
		new_ka.ka_restorer = NULL;
	}

	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);

	if (!ret && oact) {
		if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
		    __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
		    __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
		    __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
			return -EFAULT;
	}

	return ret;
}

SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
		struct sigaction __user *, oact,
		size_t, sigsetsize, void __user *, restorer)
{
	struct k_sigaction new_ka, old_ka;
	int ret;

	/* XXX: Don't preclude handling different sized sigset_t's.  */
	if (sigsetsize != sizeof(sigset_t))
		return -EINVAL;

	if (act) {
		new_ka.ka_restorer = restorer;
		if (copy_from_user(&new_ka.sa, act, sizeof(*act)))
			return -EFAULT;
	}

	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);

	if (!ret && oact) {
		if (copy_to_user(oact, &old_ka.sa, sizeof(*oact)))
			return -EFAULT;
	}

	return ret;
}

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
SYSCALL_DEFINE1(sigsuspend, old_sigset_t, mask)
{
	mask &= _BLOCKABLE;
	spin_lock_irq(&current->sighand->siglock);
	current->saved_sigmask = current->blocked;
	siginitset(&current->blocked, mask);
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

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

asmlinkage int
sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss)
{
	return do_sigaltstack(uss, uoss, rdusp());
}

/*
 * Do a signal return; undo the signal stack.
 */

#if _NSIG_WORDS > 1
# error "Non SA_SIGINFO frame needs rearranging"
#endif

struct sigframe
{
	struct sigcontext sc;
	unsigned int retcode[3];
};

struct rt_sigframe
{
	struct siginfo info;
	struct ucontext uc;
	unsigned int retcode[3];
};

/* If this changes, userland unwinders that Know Things about our signal
   frame will break.  Do not undertake lightly.  It also implies an ABI
   change wrt the size of siginfo_t, which may cause some pain.  */
extern char compile_time_assert
        [offsetof(struct rt_sigframe, uc.uc_mcontext) == 176 ? 1 : -1];

#define INSN_MOV_R30_R16	0x47fe0410
#define INSN_LDI_R0		0x201f0000
#define INSN_CALLSYS		0x00000083

static long
restore_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
		   struct switch_stack *sw)
{
	unsigned long usp;
	long i, err = __get_user(regs->pc, &sc->sc_pc);

	current_thread_info()->restart_block.fn = do_no_restart_syscall;

	sw->r26 = (unsigned long) ret_from_sys_call;

	err |= __get_user(regs->r0, sc->sc_regs+0);
	err |= __get_user(regs->r1, sc->sc_regs+1);
	err |= __get_user(regs->r2, sc->sc_regs+2);
	err |= __get_user(regs->r3, sc->sc_regs+3);
	err |= __get_user(regs->r4, sc->sc_regs+4);
	err |= __get_user(regs->r5, sc->sc_regs+5);
	err |= __get_user(regs->r6, sc->sc_regs+6);
	err |= __get_user(regs->r7, sc->sc_regs+7);
	err |= __get_user(regs->r8, sc->sc_regs+8);
	err |= __get_user(sw->r9, sc->sc_regs+9);
	err |= __get_user(sw->r10, sc->sc_regs+10);
	err |= __get_user(sw->r11, sc->sc_regs+11);
	err |= __get_user(sw->r12, sc->sc_regs+12);
	err |= __get_user(sw->r13, sc->sc_regs+13);
	err |= __get_user(sw->r14, sc->sc_regs+14);
	err |= __get_user(sw->r15, sc->sc_regs+15);
	err |= __get_user(regs->r16, sc->sc_regs+16);
	err |= __get_user(regs->r17, sc->sc_regs+17);
	err |= __get_user(regs->r18, sc->sc_regs+18);
	err |= __get_user(regs->r19, sc->sc_regs+19);
	err |= __get_user(regs->r20, sc->sc_regs+20);
	err |= __get_user(regs->r21, sc->sc_regs+21);
	err |= __get_user(regs->r22, sc->sc_regs+22);
	err |= __get_user(regs->r23, sc->sc_regs+23);
	err |= __get_user(regs->r24, sc->sc_regs+24);
	err |= __get_user(regs->r25, sc->sc_regs+25);
	err |= __get_user(regs->r26, sc->sc_regs+26);
	err |= __get_user(regs->r27, sc->sc_regs+27);
	err |= __get_user(regs->r28, sc->sc_regs+28);
	err |= __get_user(regs->gp, sc->sc_regs+29);
	err |= __get_user(usp, sc->sc_regs+30);
	wrusp(usp);

	for (i = 0; i < 31; i++)
		err |= __get_user(sw->fp[i], sc->sc_fpregs+i);
	err |= __get_user(sw->fp[31], &sc->sc_fpcr);

	return err;
}

/* Note that this syscall is also used by setcontext(3) to install
   a given sigcontext.  This because it's impossible to set *all*
   registers and transfer control from userland.  */

asmlinkage void
do_sigreturn(struct sigcontext __user *sc, struct pt_regs *regs,
	     struct switch_stack *sw)
{
	sigset_t set;

	/* Verify that it's a good sigcontext before using it */
	if (!access_ok(VERIFY_READ, sc, sizeof(*sc)))
		goto give_sigsegv;
	if (__get_user(set.sig[0], &sc->sc_mask))
		goto give_sigsegv;

	sigdelsetmask(&set, ~_BLOCKABLE);
	spin_lock_irq(&current->sighand->siglock);
	current->blocked = set;
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

	if (restore_sigcontext(sc, regs, sw))
		goto give_sigsegv;

	/* Send SIGTRAP if we're single-stepping: */
	if (ptrace_cancel_bpt (current)) {
		siginfo_t info;

		info.si_signo = SIGTRAP;
		info.si_errno = 0;
		info.si_code = TRAP_BRKPT;
		info.si_addr = (void __user *) regs->pc;
		info.si_trapno = 0;
		send_sig_info(SIGTRAP, &info, current);
	}
	return;

give_sigsegv:
	force_sig(SIGSEGV, current);
}

asmlinkage void
do_rt_sigreturn(struct rt_sigframe __user *frame, struct pt_regs *regs,
		struct switch_stack *sw)
{
	sigset_t set;

	/* Verify that it's a good ucontext_t before using it */
	if (!access_ok(VERIFY_READ, &frame->uc, sizeof(frame->uc)))
		goto give_sigsegv;
	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
		goto give_sigsegv;

	sigdelsetmask(&set, ~_BLOCKABLE);
	spin_lock_irq(&current->sighand->siglock);
	current->blocked = set;
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

	if (restore_sigcontext(&frame->uc.uc_mcontext, regs, sw))
		goto give_sigsegv;

	/* Send SIGTRAP if we're single-stepping: */
	if (ptrace_cancel_bpt (current)) {
		siginfo_t info;

		info.si_signo = SIGTRAP;
		info.si_errno = 0;
		info.si_code = TRAP_BRKPT;
		info.si_addr = (void __user *) regs->pc;
		info.si_trapno = 0;
		send_sig_info(SIGTRAP, &info, current);
	}
	return;

give_sigsegv:
	force_sig(SIGSEGV, current);
}


/*
 * Set up a signal frame.
 */

static inline void __user *
get_sigframe(struct k_sigaction *ka, unsigned long sp, size_t frame_size)
{
	if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! sas_ss_flags(sp))
		sp = current->sas_ss_sp + current->sas_ss_size;

	return (void __user *)((sp - frame_size) & -32ul);
}

static long
setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, 
		 struct switch_stack *sw, unsigned long mask, unsigned long sp)
{
	long i, err = 0;

	err |= __put_user(on_sig_stack((unsigned long)sc), &sc->sc_onstack);
	err |= __put_user(mask, &sc->sc_mask);
	err |= __put_user(regs->pc, &sc->sc_pc);
	err |= __put_user(8, &sc->sc_ps);

	err |= __put_user(regs->r0 , sc->sc_regs+0);
	err |= __put_user(regs->r1 , sc->sc_regs+1);
	err |= __put_user(regs->r2 , sc->sc_regs+2);
	err |= __put_user(regs->r3 , sc->sc_regs+3);
	err |= __put_user(regs->r4 , sc->sc_regs+4);
	err |= __put_user(regs->r5 , sc->sc_regs+5);
	err |= __put_user(regs->r6 , sc->sc_regs+6);
	err |= __put_user(regs->r7 , sc->sc_regs+7);
	err |= __put_user(regs->r8 , sc->sc_regs+8);
	err |= __put_user(sw->r9   , sc->sc_regs+9);
	err |= __put_user(sw->r10  , sc->sc_regs+10);
	err |= __put_user(sw->r11  , sc->sc_regs+11);
	err |= __put_user(sw->r12  , sc->sc_regs+12);
	err |= __put_user(sw->r13  , sc->sc_regs+13);
	err |= __put_user(sw->r14  , sc->sc_regs+14);
	err |= __put_user(sw->r15  , sc->sc_regs+15);
	err |= __put_user(regs->r16, sc->sc_regs+16);
	err |= __put_user(regs->r17, sc->sc_regs+17);
	err |= __put_user(regs->r18, sc->sc_regs+18);
	err |= __put_user(regs->r19, sc->sc_regs+19);
	err |= __put_user(regs->r20, sc->sc_regs+20);
	err |= __put_user(regs->r21, sc->sc_regs+21);
	err |= __put_user(regs->r22, sc->sc_regs+22);
	err |= __put_user(regs->r23, sc->sc_regs+23);
	err |= __put_user(regs->r24, sc->sc_regs+24);
	err |= __put_user(regs->r25, sc->sc_regs+25);
	err |= __put_user(regs->r26, sc->sc_regs+26);
	err |= __put_user(regs->r27, sc->sc_regs+27);
	err |= __put_user(regs->r28, sc->sc_regs+28);
	err |= __put_user(regs->gp , sc->sc_regs+29);
	err |= __put_user(sp, sc->sc_regs+30);
	err |= __put_user(0, sc->sc_regs+31);

	for (i = 0; i < 31; i++)
		err |= __put_user(sw->fp[i], sc->sc_fpregs+i);
	err |= __put_user(0, sc->sc_fpregs+31);
	err |= __put_user(sw->fp[31], &sc->sc_fpcr);

	err |= __put_user(regs->trap_a0, &sc->sc_traparg_a0);
	err |= __put_user(regs->trap_a1, &sc->sc_traparg_a1);
	err |= __put_user(regs->trap_a2, &sc->sc_traparg_a2);

	return err;
}

static int
setup_frame(int sig, struct k_sigaction *ka, sigset_t *set,
	    struct pt_regs *regs, struct switch_stack * sw)
{
	unsigned long oldsp, r26, err = 0;
	struct sigframe __user *frame;

	oldsp = rdusp();
	frame = get_sigframe(ka, oldsp, sizeof(*frame));
	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
		goto give_sigsegv;

	err |= setup_sigcontext(&frame->sc, regs, sw, set->sig[0], oldsp);
	if (err)
		goto give_sigsegv;

	/* Set up to return from userspace.  If provided, use a stub
	   already in userspace.  */
	if (ka->ka_restorer) {
		r26 = (unsigned long) ka->ka_restorer;
	} else {
		err |= __put_user(INSN_MOV_R30_R16, frame->retcode+0);
		err |= __put_user(INSN_LDI_R0+__NR_sigreturn, frame->retcode+1);
		err |= __put_user(INSN_CALLSYS, frame->retcode+2);
		imb();
		r26 = (unsigned long) frame->retcode;
	}

	/* Check that everything was written properly.  */
	if (err)
		goto give_sigsegv;

	/* "Return" to the handler */
	regs->r26 = r26;
	regs->r27 = regs->pc = (unsigned long) ka->sa.sa_handler;
	regs->r16 = sig;			/* a0: signal number */
	regs->r17 = 0;				/* a1: exception code */
	regs->r18 = (unsigned long) &frame->sc;	/* a2: sigcontext pointer */
	wrusp((unsigned long) frame);
	
#if DEBUG_SIG
	printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
		current->comm, current->pid, frame, regs->pc, regs->r26);
#endif

	return 0;

give_sigsegv:
	force_sigsegv(sig, current);
	return -EFAULT;
}

static int
setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
	       sigset_t *set, struct pt_regs *regs, struct switch_stack * sw)
{
	unsigned long oldsp, r26, err = 0;
	struct rt_sigframe __user *frame;

	oldsp = rdusp();
	frame = get_sigframe(ka, oldsp, sizeof(*frame));
	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
		goto give_sigsegv;

	err |= copy_siginfo_to_user(&frame->info, info);

	/* Create the ucontext.  */
	err |= __put_user(0, &frame->uc.uc_flags);
	err |= __put_user(0, &frame->uc.uc_link);
	err |= __put_user(set->sig[0], &frame->uc.uc_osf_sigmask);
	err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
	err |= __put_user(sas_ss_flags(oldsp), &frame->uc.uc_stack.ss_flags);
	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, sw,
				set->sig[0], oldsp);
	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
	if (err)
		goto give_sigsegv;

	/* Set up to return from userspace.  If provided, use a stub
	   already in userspace.  */
	if (ka->ka_restorer) {
		r26 = (unsigned long) ka->ka_restorer;
	} else {
		err |= __put_user(INSN_MOV_R30_R16, frame->retcode+0);
		err |= __put_user(INSN_LDI_R0+__NR_rt_sigreturn,
				  frame->retcode+1);
		err |= __put_user(INSN_CALLSYS, frame->retcode+2);
		imb();
		r26 = (unsigned long) frame->retcode;
	}

	if (err)
		goto give_sigsegv;

	/* "Return" to the handler */
	regs->r26 = r26;
	regs->r27 = regs->pc = (unsigned long) ka->sa.sa_handler;
	regs->r16 = sig;			  /* a0: signal number */
	regs->r17 = (unsigned long) &frame->info; /* a1: siginfo pointer */
	regs->r18 = (unsigned long) &frame->uc;	  /* a2: ucontext pointer */
	wrusp((unsigned long) frame);

#if DEBUG_SIG
	printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
		current->comm, current->pid, frame, regs->pc, regs->r26);
#endif

	return 0;

give_sigsegv:
	force_sigsegv(sig, current);
	return -EFAULT;
}


/*
 * OK, we're invoking a handler.
 */
static inline int
handle_signal(int sig, struct k_sigaction *ka, siginfo_t *info,
	      sigset_t *oldset, struct pt_regs * regs, struct switch_stack *sw)
{
	int ret;

	if (ka->sa.sa_flags & SA_SIGINFO)
		ret = setup_rt_frame(sig, ka, info, oldset, regs, sw);
	else
		ret = setup_frame(sig, ka, oldset, regs, sw);

	if (ret == 0) {
		spin_lock_irq(&current->sighand->siglock);
		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
		if (!(ka->sa.sa_flags & SA_NODEFER)) 
			sigaddset(&current->blocked,sig);
		recalc_sigpending();
		spin_unlock_irq(&current->sighand->siglock);
	}

	return ret;
}

static inline void
syscall_restart(unsigned long r0, unsigned long r19,
		struct pt_regs *regs, struct k_sigaction *ka)
{
	switch (regs->r0) {
	case ERESTARTSYS:
		if (!(ka->sa.sa_flags & SA_RESTART)) {
		case ERESTARTNOHAND:
			regs->r0 = EINTR;
			break;
		}
		/* fallthrough */
	case ERESTARTNOINTR:
		regs->r0 = r0;	/* reset v0 and a3 and replay syscall */
		regs->r19 = r19;
		regs->pc -= 4;
		break;
	case ERESTART_RESTARTBLOCK:
		regs->r0 = EINTR;
		break;
	}
}


/*
 * 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.
 *
 * Note that we go through the signals twice: once to check the signals that
 * the kernel can handle, and then we build all the user-level signal handling
 * stack-frames in one go after that.
 *
 * "r0" and "r19" are the registers we need to restore for system call
 * restart. "r0" is also used as an indicator whether we can restart at
 * all (if we get here from anything but a syscall return, it will be 0)
 */
static void
do_signal(struct pt_regs * regs, struct switch_stack * sw,
	  unsigned long r0, unsigned long r19)
{
	siginfo_t info;
	int signr;
	unsigned long single_stepping = ptrace_cancel_bpt(current);
	struct k_sigaction ka;
	sigset_t *oldset;

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

	/* This lets the debugger run, ... */
	signr = get_signal_to_deliver(&info, &ka, regs, NULL);

	/* ... so re-check the single stepping. */
	single_stepping |= ptrace_cancel_bpt(current);

	if (signr > 0) {
		/* Whee!  Actually deliver the signal.  */
		if (r0)
			syscall_restart(r0, r19, regs, &ka);
		if (handle_signal(signr, &ka, &info, oldset, regs, sw) == 0) {
			/* A signal was successfully delivered, and the
			   saved sigmask was stored on the signal frame,
			   and will be restored by sigreturn.  So we can
			   simply clear the restore sigmask flag.  */
			if (test_thread_flag(TIF_RESTORE_SIGMASK))
				clear_thread_flag(TIF_RESTORE_SIGMASK);
		}
		if (single_stepping) 
			ptrace_set_bpt(current); /* re-set bpt */
		return;
	}

	if (r0) {
	  	switch (regs->r0) {
		case ERESTARTNOHAND:
		case ERESTARTSYS:
		case ERESTARTNOINTR:
			/* Reset v0 and a3 and replay syscall.  */
			regs->r0 = r0;
			regs->r19 = r19;
			regs->pc -= 4;
			break;
		case ERESTART_RESTARTBLOCK:
			/* Force v0 to the restart syscall and reply.  */
			regs->r0 = __NR_restart_syscall;
			regs->pc -= 4;
			break;
		}
	}

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

	if (single_stepping)
		ptrace_set_bpt(current);	/* re-set breakpoint */
}

void
do_notify_resume(struct pt_regs *regs, struct switch_stack *sw,
		 unsigned long thread_info_flags,
		 unsigned long r0, unsigned long r19)
{
	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
		do_signal(regs, sw, r0, r19);

	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
		clear_thread_flag(TIF_NOTIFY_RESUME);
		tracehook_notify_resume(regs);
		if (current->replacement_session_keyring)
			key_replace_session_keyring();
	}
}