* better

[mascara-docs.git] / i386 / linux-2.3.21 / arch / ppc / kernel / signal.c

/*
 *  linux/arch/ppc/kernel/signal.c
 *
 *  $Id: signal.c,v 1.27 1999/08/03 19:16:38 cort Exp $
 *
 *  PowerPC version 
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 *  Derived from "arch/i386/kernel/signal.c"
 *    Copyright (C) 1991, 1992 Linus Torvalds
 *    1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.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/stddef.h>
#include <linux/elf.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>

#define DEBUG_SIG 0

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

#ifndef MIN
#define MIN(a,b) (((a) < (b)) ? (a) : (b))
#endif

#define GP_REGS_SIZE    MIN(sizeof(elf_gregset_t), sizeof(struct pt_regs))

/* 
 * These are the flags in the MSR that the user is allowed to change
 * by modifying the saved value of the MSR on the stack.  SE and BE
 * should not be in this list since gdb may want to change these.  I.e,
 * you should be able to step out of a signal handler to see what
 * instruction executes next after the signal handler completes.
 * Alternately, if you stepped into a signal handler, you should be
 * able to continue 'til the next breakpoint from within the signal
 * handler, even if the handler returns.
 */
#define MSR_USERCHANGE  (MSR_FE0 | MSR_FE1)

int do_signal(sigset_t *oldset, struct pt_regs *regs);
extern int sys_wait4(pid_t pid, unsigned long *stat_addr,
                     int options, unsigned long *ru);

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
int
sys_sigsuspend(old_sigset_t mask, int p2, int p3, int p4, int p6, int p7,
               struct pt_regs *regs)
{
        sigset_t saveset;

        mask &= _BLOCKABLE;
        spin_lock_irq(&current->sigmask_lock);
        saveset = current->blocked;
        siginitset(&current->blocked, mask);
        recalc_sigpending(current);
        spin_unlock_irq(&current->sigmask_lock);

        regs->gpr[3] = -EINTR;
        while (1) {
                current->state = TASK_INTERRUPTIBLE;
                schedule();
                if (do_signal(&saveset, regs))
                        /*
                         * If a signal handler needs to be called,
                         * do_signal() has set R3 to the signal number (the
                         * first argument of the signal handler), so don't
                         * overwrite that with EINTR !
                         * In the other cases, do_signal() doesn't touch 
                         * R3, so it's still set to -EINTR (see above).
                         */
                        return regs->gpr[3];
        }
}

int
sys_rt_sigsuspend(sigset_t *unewset, size_t sigsetsize, int p3, int p4, int p6,
                  int p7, struct pt_regs *regs)
{
        sigset_t saveset, newset;

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

        if (copy_from_user(&newset, unewset, sizeof(newset)))
                return -EFAULT;
        sigdelsetmask(&newset, ~_BLOCKABLE);

        spin_lock_irq(&current->sigmask_lock);
        saveset = current->blocked;
        current->blocked = newset;
        recalc_sigpending(current);
        spin_unlock_irq(&current->sigmask_lock);

        regs->gpr[3] = -EINTR;
        while (1) {
                current->state = TASK_INTERRUPTIBLE;
                schedule();
                if (do_signal(&saveset, regs))
                        return regs->gpr[3];
        }
}


asmlinkage int sys_rt_sigreturn(unsigned long __unused)
{
        printk("sys_rt_sigreturn(): %s/%d not yet implemented.\n",
               current->comm,current->pid);
        do_exit(SIGSEGV);
}

asmlinkage int
sys_sigaltstack(const stack_t *uss, stack_t *uoss)
{
        struct pt_regs *regs = (struct pt_regs *) &uss;
        return do_sigaltstack(uss, uoss, regs->gpr[1]);
}

int 
sys_sigaction(int sig, const struct old_sigaction *act,
              struct old_sigaction *oact)
{
        struct k_sigaction new_ka, old_ka;
        int ret;

        if (act) {
                old_sigset_t mask;
                if (verify_area(VERIFY_READ, act, sizeof(*act)) ||
                    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
                    __get_user(new_ka.sa.sa_restorer, &act->sa_restorer))
                        return -EFAULT;
                __get_user(new_ka.sa.sa_flags, &act->sa_flags);
                __get_user(mask, &act->sa_mask);
                siginitset(&new_ka.sa.sa_mask, mask);
        }

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

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

        return ret;
}

/*
 * When we have signals to deliver, we set up on the
 * user stack, going down from the original stack pointer:
 *      a sigregs struct
 *      one or more sigcontext structs
 *      a gap of __SIGNAL_FRAMESIZE bytes
 *
 * Each of these things must be a multiple of 16 bytes in size.
 *
 * XXX ultimately we will have to stack up a siginfo and ucontext
 * for each rt signal.
 */
struct sigregs {
        elf_gregset_t   gp_regs;
        double          fp_regs[ELF_NFPREG];
        unsigned long   tramp[2];
        /* Programs using the rs6000/xcoff abi can save up to 19 gp regs
           and 18 fp regs below sp before decrementing it. */
        int             abigap[56];
};

/*
 * Do a signal return; undo the signal stack.
 */
int sys_sigreturn(struct pt_regs *regs)
{
        struct sigcontext_struct *sc, sigctx;
        struct sigregs *sr;
        int ret;
        elf_gregset_t saved_regs;  /* an array of ELF_NGREG unsigned longs */
        sigset_t set;
        unsigned long prevsp;

        sc = (struct sigcontext_struct *)(regs->gpr[1] + __SIGNAL_FRAMESIZE);
        if (copy_from_user(&sigctx, sc, sizeof(sigctx)))
                goto badframe;

        set.sig[0] = sigctx.oldmask;
#if _NSIG_WORDS > 1
        set.sig[1] = sigctx._unused[3];
#endif
        sigdelsetmask(&set, ~_BLOCKABLE);
        spin_lock_irq(&current->sigmask_lock);
        current->blocked = set;
        recalc_sigpending(current);
        spin_unlock_irq(&current->sigmask_lock);

        sc++;                   /* Look at next sigcontext */
        if (sc == (struct sigcontext_struct *)(sigctx.regs)) {
                /* Last stacked signal - restore registers */
                sr = (struct sigregs *) sigctx.regs;
                if (regs->msr & MSR_FP )
                        giveup_fpu(current);
                if (copy_from_user(saved_regs, &sr->gp_regs,
                                   sizeof(sr->gp_regs)))
                        goto badframe;
                saved_regs[PT_MSR] = (regs->msr & ~MSR_USERCHANGE)
                        | (saved_regs[PT_MSR] & MSR_USERCHANGE);
                memcpy(regs, saved_regs, GP_REGS_SIZE);

                if (copy_from_user(current->thread.fpr, &sr->fp_regs,
                                   sizeof(sr->fp_regs)))
                        goto badframe;

                ret = regs->result;

        } else {
                /* More signals to go */
                regs->gpr[1] = (unsigned long)sc - __SIGNAL_FRAMESIZE;
                if (copy_from_user(&sigctx, sc, sizeof(sigctx)))
                        goto badframe;
                sr = (struct sigregs *) sigctx.regs;
                regs->gpr[3] = ret = sigctx.signal;
                regs->gpr[4] = (unsigned long) sc;
                regs->link = (unsigned long) &sr->tramp;
                regs->nip = sigctx.handler;

                if (get_user(prevsp, &sr->gp_regs[PT_R1])
                    || put_user(prevsp, (unsigned long *) regs->gpr[1]))
                        goto badframe;
        }
        return ret;

badframe:
        lock_kernel();
        do_exit(SIGSEGV);
}       

/*
 * Set up a signal frame.
 */
static void
setup_frame(struct pt_regs *regs, struct sigregs *frame,
            unsigned long newsp)
{
        struct sigcontext_struct *sc = (struct sigcontext_struct *) newsp;

        if (verify_area(VERIFY_WRITE, frame, sizeof(*frame)))
                goto badframe;
                if (regs->msr & MSR_FP)
                        giveup_fpu(current);
        if (__copy_to_user(&frame->gp_regs, regs, GP_REGS_SIZE)
            || __copy_to_user(&frame->fp_regs, current->thread.fpr,
                              ELF_NFPREG * sizeof(double))
            || __put_user(0x38007777UL, &frame->tramp[0])    /* li r0,0x7777 */
            || __put_user(0x44000002UL, &frame->tramp[1]))   /* sc */
                goto badframe;
        flush_icache_range((unsigned long) &frame->tramp[0],
                           (unsigned long) &frame->tramp[2]);

        newsp -= __SIGNAL_FRAMESIZE;
        if (put_user(regs->gpr[1], (unsigned long *)newsp)
            || get_user(regs->nip, &sc->handler)
            || get_user(regs->gpr[3], &sc->signal))
                goto badframe;
        regs->gpr[1] = newsp;
        regs->gpr[4] = (unsigned long) sc;
        regs->link = (unsigned long) frame->tramp;

        return;

badframe:
#if DEBUG_SIG
        printk("badframe in setup_frame, regs=%p frame=%p newsp=%lx\n",
               regs, frame, newsp);
#endif
        lock_kernel();
        do_exit(SIGSEGV);
}

/*
 * OK, we're invoking a handler
 */
static void
handle_signal(unsigned long sig, struct k_sigaction *ka,
              siginfo_t *info, sigset_t *oldset, struct pt_regs * regs,
              unsigned long *newspp, unsigned long frame)
{
        struct sigcontext_struct *sc;

        if (regs->trap == 0x0C00 /* System Call! */
            && ((int)regs->result == -ERESTARTNOHAND ||
                ((int)regs->result == -ERESTARTSYS &&
                 !(ka->sa.sa_flags & SA_RESTART))))
                regs->result = -EINTR;

        /* Put another sigcontext on the stack */
        *newspp -= sizeof(*sc);
        sc = (struct sigcontext_struct *) *newspp;
        if (verify_area(VERIFY_WRITE, sc, sizeof(*sc)))
                goto badframe;

        if (__put_user((unsigned long) ka->sa.sa_handler, &sc->handler)
            || __put_user(oldset->sig[0], &sc->oldmask)
#if _NSIG_WORDS > 1
            || __put_user(oldset->sig[1], &sc->_unused[3])
#endif
            || __put_user((struct pt_regs *)frame, &sc->regs)
            || __put_user(sig, &sc->signal))
                goto badframe;

        if (ka->sa.sa_flags & SA_ONESHOT)
                ka->sa.sa_handler = SIG_DFL;

        if (!(ka->sa.sa_flags & SA_NODEFER)) {
                spin_lock_irq(&current->sigmask_lock);
                sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
                sigaddset(&current->blocked,sig);
                recalc_sigpending(current);
                spin_unlock_irq(&current->sigmask_lock);
        }
        return;

badframe:
#if DEBUG_SIG
        printk("badframe in handle_signal, regs=%p frame=%lx newsp=%lx\n",
               regs, frame, *newspp);
        printk("sc=%p sig=%d ka=%p info=%p oldset=%p\n", sc, sig, ka, info, oldset);
#endif
        lock_kernel();
        do_exit(SIGSEGV);
}

/*
 * 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.
 */
int do_signal(sigset_t *oldset, struct pt_regs *regs)
{
        siginfo_t info;
        struct k_sigaction *ka;
        unsigned long frame, newsp;

        if (!oldset)
                oldset = &current->blocked;

        newsp = frame = 0;

        for (;;) {
                unsigned long signr;

                spin_lock_irq(&current->sigmask_lock);
                signr = dequeue_signal(&current->blocked, &info);
                spin_unlock_irq(&current->sigmask_lock);

                if (!signr)
                        break;

                if ((current->flags & PF_PTRACED) && signr != SIGKILL) {
                        /* Let the debugger run.  */
                        current->exit_code = signr;
                        current->state = TASK_STOPPED;
                        notify_parent(current, SIGCHLD);
                        schedule();

                        /* We're back.  Did the debugger cancel the sig?  */
                        if (!(signr = current->exit_code))
                                continue;
                        current->exit_code = 0;

                        /* The debugger continued.  Ignore SIGSTOP.  */
                        if (signr == SIGSTOP)
                                continue;

                        /* Update the siginfo structure.  Is this good?  */
                        if (signr != info.si_signo) {
                                info.si_signo = signr;
                                info.si_errno = 0;
                                info.si_code = SI_USER;
                                info.si_pid = current->p_pptr->pid;
                                info.si_uid = current->p_pptr->uid;
                        }

                        /* If the (new) signal is now blocked, requeue it.  */
                        if (sigismember(&current->blocked, signr)) {
                                send_sig_info(signr, &info, current);
                                continue;
                        }
                }

                ka = &current->sig->action[signr-1];
                if (ka->sa.sa_handler == SIG_IGN) {
                        if (signr != SIGCHLD)
                                continue;
                        /* Check for SIGCHLD: it's special.  */
                        while (sys_wait4(-1, NULL, WNOHANG, NULL) > 0)
                                /* nothing */;
                        continue;
                }

                if (ka->sa.sa_handler == SIG_DFL) {
                        int exit_code = signr;

                        /* Init gets no signals it doesn't want.  */
                        if (current->pid == 1)
                                continue;

                        switch (signr) {
                        case SIGCONT: case SIGCHLD: case SIGWINCH:
                                continue;

                        case SIGTSTP: case SIGTTIN: case SIGTTOU:
                                if (is_orphaned_pgrp(current->pgrp))
                                        continue;
                                /* FALLTHRU */

                        case SIGSTOP:
                                current->state = TASK_STOPPED;
                                current->exit_code = signr;
                                if (!(current->p_pptr->sig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP))
                                        notify_parent(current, SIGCHLD);
                                schedule();
                                continue;

                        case SIGQUIT: case SIGILL: case SIGTRAP:
                        case SIGABRT: case SIGFPE: case SIGSEGV:
                                if (do_coredump(signr, regs))
                                        exit_code |= 0x80;
                                /* FALLTHRU */

                        default:
                                lock_kernel();
                                sigaddset(&current->signal, signr);
                                recalc_sigpending(current);
                                current->flags |= PF_SIGNALED;
                                do_exit(exit_code);
                                /* NOTREACHED */
                        }
                }

                if ( (ka->sa.sa_flags & SA_ONSTACK)
                     && (! on_sig_stack(regs->gpr[1])))
                        newsp = (current->sas_ss_sp + current->sas_ss_size);
                else
                        newsp = regs->gpr[1];
                newsp = frame = newsp - sizeof(struct sigregs);

                /* Whee!  Actually deliver the signal.  */
                handle_signal(signr, ka, &info, oldset, regs, &newsp, frame);
        }

        if (regs->trap == 0x0C00 /* System Call! */ &&
            ((int)regs->result == -ERESTARTNOHAND ||
             (int)regs->result == -ERESTARTSYS ||
             (int)regs->result == -ERESTARTNOINTR)) {
                regs->gpr[3] = regs->orig_gpr3;
                regs->nip -= 4;         /* Back up & retry system call */
                regs->result = 0;
        }

        if (newsp == frame)
                return 0;               /* no signals delivered */

        setup_frame(regs, (struct sigregs *) frame, newsp);
        return 1;
}