signal.c

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/*
 *  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);

/*
 * 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)
{
    sigset_t blocked;
    siginitset(&blocked, mask);
    return sigsuspend(&blocked);
}

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;

    set_current_blocked(&set);

    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;

    set_current_blocked(&set);

    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, 
         unsigned long mask, unsigned long sp)
{
    struct switch_stack *sw = (struct switch_stack *)regs - 1;
    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)
{
    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)))
        return -EFAULT;

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

    /* 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)
        return err;

    /* "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;
}

static int
setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
           sigset_t *set, struct pt_regs *regs)
{
    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)))
        return -EFAULT;

    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, 
                set->sig[0], oldsp);
    err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
    if (err)
        return -EFAULT;

    /* 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)
        return -EFAULT;

    /* "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;
}


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

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

    if (ret) {
        force_sigsegv(sig, current);
        return;
    }
    signal_delivered(sig, info, ka, regs, 0);
}

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, unsigned long r0, unsigned long r19)
{
    siginfo_t info;
    int signr;
    unsigned long single_stepping = ptrace_cancel_bpt(current);
    struct k_sigaction ka;

    /* 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);
        handle_signal(signr, &ka, &info, regs);
        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.  */
    restore_saved_sigmask();
    if (single_stepping)
        ptrace_set_bpt(current);    /* re-set breakpoint */
}

void
do_work_pending(struct pt_regs *regs, unsigned long thread_flags,
         unsigned long r0, unsigned long r19)
{
    do {
        if (thread_flags & _TIF_NEED_RESCHED) {
            schedule();
        } else {
            local_irq_enable();
            if (thread_flags & _TIF_SIGPENDING) {
                do_signal(regs, r0, r19);
                r0 = 0;
            } else {
                clear_thread_flag(TIF_NOTIFY_RESUME);
                tracehook_notify_resume(regs);
            }
        }
        local_irq_disable();
        thread_flags = current_thread_info()->flags;
    } while (thread_flags & _TIF_WORK_MASK);
}