signal.c

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/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1991, 1992  Linus Torvalds
 * Copyright (C) 1994 - 2000  Ralf Baechle
 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
 */
#include <linux/cache.h>
#include <linux/irqflags.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/personality.h>
#include <linux/smp.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/compiler.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#include <linux/tracehook.h>

#include <asm/abi.h>
#include <asm/asm.h>
#include <linux/bitops.h>
#include <asm/cacheflush.h>
#include <asm/fpu.h>
#include <asm/sim.h>
#include <asm/ucontext.h>
#include <asm/cpu-features.h>
#include <asm/war.h>
#include <asm/vdso.h>
#include <asm/dsp.h>

#include "signal-common.h"

static int (*save_fp_context)(struct sigcontext __user *sc);
static int (*restore_fp_context)(struct sigcontext __user *sc);

extern asmlinkage int _save_fp_context(struct sigcontext __user *sc);
extern asmlinkage int _restore_fp_context(struct sigcontext __user *sc);

extern asmlinkage int fpu_emulator_save_context(struct sigcontext __user *sc);
extern asmlinkage int fpu_emulator_restore_context(struct sigcontext __user *sc);

struct sigframe {
    u32 sf_ass[4];      /* argument save space for o32 */
    u32 sf_pad[2];      /* Was: signal trampoline */
    struct sigcontext sf_sc;
    sigset_t sf_mask;
};

struct rt_sigframe {
    u32 rs_ass[4];      /* argument save space for o32 */
    u32 rs_pad[2];      /* Was: signal trampoline */
    struct siginfo rs_info;
    struct ucontext rs_uc;
};

/*
 * Helper routines
 */
static int protected_save_fp_context(struct sigcontext __user *sc)
{
    int err;
    while (1) {
        lock_fpu_owner();
        own_fpu_inatomic(1);
        err = save_fp_context(sc); /* this might fail */
        unlock_fpu_owner();
        if (likely(!err))
            break;
        /* touch the sigcontext and try again */
        err = __put_user(0, &sc->sc_fpregs[0]) |
            __put_user(0, &sc->sc_fpregs[31]) |
            __put_user(0, &sc->sc_fpc_csr);
        if (err)
            break;  /* really bad sigcontext */
    }
    return err;
}

static int protected_restore_fp_context(struct sigcontext __user *sc)
{
    int err, tmp __maybe_unused;
    while (1) {
        lock_fpu_owner();
        own_fpu_inatomic(0);
        err = restore_fp_context(sc); /* this might fail */
        unlock_fpu_owner();
        if (likely(!err))
            break;
        /* touch the sigcontext and try again */
        err = __get_user(tmp, &sc->sc_fpregs[0]) |
            __get_user(tmp, &sc->sc_fpregs[31]) |
            __get_user(tmp, &sc->sc_fpc_csr);
        if (err)
            break;  /* really bad sigcontext */
    }
    return err;
}

int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
    int err = 0;
    int i;
    unsigned int used_math;

    err |= __put_user(regs->cp0_epc, &sc->sc_pc);

    err |= __put_user(0, &sc->sc_regs[0]);
    for (i = 1; i < 32; i++)
        err |= __put_user(regs->regs[i], &sc->sc_regs[i]);

#ifdef CONFIG_CPU_HAS_SMARTMIPS
    err |= __put_user(regs->acx, &sc->sc_acx);
#endif
    err |= __put_user(regs->hi, &sc->sc_mdhi);
    err |= __put_user(regs->lo, &sc->sc_mdlo);
    if (cpu_has_dsp) {
        err |= __put_user(mfhi1(), &sc->sc_hi1);
        err |= __put_user(mflo1(), &sc->sc_lo1);
        err |= __put_user(mfhi2(), &sc->sc_hi2);
        err |= __put_user(mflo2(), &sc->sc_lo2);
        err |= __put_user(mfhi3(), &sc->sc_hi3);
        err |= __put_user(mflo3(), &sc->sc_lo3);
        err |= __put_user(rddsp(DSP_MASK), &sc->sc_dsp);
    }

    used_math = !!used_math();
    err |= __put_user(used_math, &sc->sc_used_math);

    if (used_math) {
        /*
         * Save FPU state to signal context. Signal handler
         * will "inherit" current FPU state.
         */
        err |= protected_save_fp_context(sc);
    }
    return err;
}

int fpcsr_pending(unsigned int __user *fpcsr)
{
    int err, sig = 0;
    unsigned int csr, enabled;

    err = __get_user(csr, fpcsr);
    enabled = FPU_CSR_UNI_X | ((csr & FPU_CSR_ALL_E) << 5);
    /*
     * If the signal handler set some FPU exceptions, clear it and
     * send SIGFPE.
     */
    if (csr & enabled) {
        csr &= ~enabled;
        err |= __put_user(csr, fpcsr);
        sig = SIGFPE;
    }
    return err ?: sig;
}

static int
check_and_restore_fp_context(struct sigcontext __user *sc)
{
    int err, sig;

    err = sig = fpcsr_pending(&sc->sc_fpc_csr);
    if (err > 0)
        err = 0;
    err |= protected_restore_fp_context(sc);
    return err ?: sig;
}

int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
    unsigned int used_math;
    unsigned long treg;
    int err = 0;
    int i;

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

    err |= __get_user(regs->cp0_epc, &sc->sc_pc);

#ifdef CONFIG_CPU_HAS_SMARTMIPS
    err |= __get_user(regs->acx, &sc->sc_acx);
#endif
    err |= __get_user(regs->hi, &sc->sc_mdhi);
    err |= __get_user(regs->lo, &sc->sc_mdlo);
    if (cpu_has_dsp) {
        err |= __get_user(treg, &sc->sc_hi1); mthi1(treg);
        err |= __get_user(treg, &sc->sc_lo1); mtlo1(treg);
        err |= __get_user(treg, &sc->sc_hi2); mthi2(treg);
        err |= __get_user(treg, &sc->sc_lo2); mtlo2(treg);
        err |= __get_user(treg, &sc->sc_hi3); mthi3(treg);
        err |= __get_user(treg, &sc->sc_lo3); mtlo3(treg);
        err |= __get_user(treg, &sc->sc_dsp); wrdsp(treg, DSP_MASK);
    }

    for (i = 1; i < 32; i++)
        err |= __get_user(regs->regs[i], &sc->sc_regs[i]);

    err |= __get_user(used_math, &sc->sc_used_math);
    conditional_used_math(used_math);

    if (used_math) {
        /* restore fpu context if we have used it before */
        if (!err)
            err = check_and_restore_fp_context(sc);
    } else {
        /* signal handler may have used FPU.  Give it up. */
        lose_fpu(0);
    }

    return err;
}

void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
              size_t frame_size)
{
    unsigned long sp;

    /* Default to using normal stack */
    sp = regs->regs[29];

    /*
     * FPU emulator may have it's own trampoline active just
     * above the user stack, 16-bytes before the next lowest
     * 16 byte boundary.  Try to avoid trashing it.
     */
    sp -= 32;

    /* This is the X/Open sanctioned signal stack switching.  */
    if ((ka->sa.sa_flags & SA_ONSTACK) && (sas_ss_flags (sp) == 0))
        sp = current->sas_ss_sp + current->sas_ss_size;

    return (void __user *)((sp - frame_size) & (ICACHE_REFILLS_WORKAROUND_WAR ? ~(cpu_icache_line_size()-1) : ALMASK));
}

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */

#ifdef CONFIG_TRAD_SIGNALS
asmlinkage int sys_sigsuspend(nabi_no_regargs struct pt_regs regs)
{
    sigset_t newset;
    sigset_t __user *uset;

    uset = (sigset_t __user *) regs.regs[4];
    if (copy_from_user(&newset, uset, sizeof(sigset_t)))
        return -EFAULT;
    return sigsuspend(&newset);
}
#endif

asmlinkage int sys_rt_sigsuspend(nabi_no_regargs struct pt_regs regs)
{
    sigset_t newset;
    sigset_t __user *unewset;
    size_t sigsetsize;

    /* XXX Don't preclude handling different sized sigset_t's.  */
    sigsetsize = regs.regs[5];
    if (sigsetsize != sizeof(sigset_t))
        return -EINVAL;

    unewset = (sigset_t __user *) regs.regs[4];
    if (copy_from_user(&newset, unewset, sizeof(newset)))
        return -EFAULT;
    return sigsuspend(&newset);
}

#ifdef CONFIG_TRAD_SIGNALS
SYSCALL_DEFINE3(sigaction, int, sig, const struct sigaction __user *, act,
    struct sigaction __user *, oact)
{
    struct k_sigaction new_ka, old_ka;
    int ret;
    int err = 0;

    if (act) {
        old_sigset_t mask;

        if (!access_ok(VERIFY_READ, act, sizeof(*act)))
            return -EFAULT;
        err |= __get_user(new_ka.sa.sa_handler, &act->sa_handler);
        err |= __get_user(new_ka.sa.sa_flags, &act->sa_flags);
        err |= __get_user(mask, &act->sa_mask.sig[0]);
        if (err)
            return -EFAULT;

        siginitset(&new_ka.sa.sa_mask, mask);
    }

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

    if (!ret && oact) {
        if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)))
            return -EFAULT;
        err |= __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
        err |= __put_user(old_ka.sa.sa_handler, &oact->sa_handler);
        err |= __put_user(old_ka.sa.sa_mask.sig[0], oact->sa_mask.sig);
        err |= __put_user(0, &oact->sa_mask.sig[1]);
        err |= __put_user(0, &oact->sa_mask.sig[2]);
        err |= __put_user(0, &oact->sa_mask.sig[3]);
        if (err)
            return -EFAULT;
    }

    return ret;
}
#endif

asmlinkage int sys_sigaltstack(nabi_no_regargs struct pt_regs regs)
{
    const stack_t __user *uss = (const stack_t __user *) regs.regs[4];
    stack_t __user *uoss = (stack_t __user *) regs.regs[5];
    unsigned long usp = regs.regs[29];

    return do_sigaltstack(uss, uoss, usp);
}

#ifdef CONFIG_TRAD_SIGNALS
asmlinkage void sys_sigreturn(nabi_no_regargs struct pt_regs regs)
{
    struct sigframe __user *frame;
    sigset_t blocked;
    int sig;

    frame = (struct sigframe __user *) regs.regs[29];
    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
        goto badframe;
    if (__copy_from_user(&blocked, &frame->sf_mask, sizeof(blocked)))
        goto badframe;

    set_current_blocked(&blocked);

    sig = restore_sigcontext(&regs, &frame->sf_sc);
    if (sig < 0)
        goto badframe;
    else if (sig)
        force_sig(sig, current);

    /*
     * Don't let your children do this ...
     */
    __asm__ __volatile__(
        "move\t$29, %0\n\t"
        "j\tsyscall_exit"
        :/* no outputs */
        :"r" (&regs));
    /* Unreached */

badframe:
    force_sig(SIGSEGV, current);
}
#endif /* CONFIG_TRAD_SIGNALS */

asmlinkage void sys_rt_sigreturn(nabi_no_regargs struct pt_regs regs)
{
    struct rt_sigframe __user *frame;
    sigset_t set;
    int sig;

    frame = (struct rt_sigframe __user *) regs.regs[29];
    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
        goto badframe;
    if (__copy_from_user(&set, &frame->rs_uc.uc_sigmask, sizeof(set)))
        goto badframe;

    set_current_blocked(&set);

    sig = restore_sigcontext(&regs, &frame->rs_uc.uc_mcontext);
    if (sig < 0)
        goto badframe;
    else if (sig)
        force_sig(sig, current);

    /* It is more difficult to avoid calling this function than to
       call it and ignore errors.  */
    do_sigaltstack(&frame->rs_uc.uc_stack, NULL, regs.regs[29]);

    /*
     * Don't let your children do this ...
     */
    __asm__ __volatile__(
        "move\t$29, %0\n\t"
        "j\tsyscall_exit"
        :/* no outputs */
        :"r" (&regs));
    /* Unreached */

badframe:
    force_sig(SIGSEGV, current);
}

#ifdef CONFIG_TRAD_SIGNALS
static int setup_frame(void *sig_return, struct k_sigaction *ka,
               struct pt_regs *regs, int signr, sigset_t *set)
{
    struct sigframe __user *frame;
    int err = 0;

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

    err |= setup_sigcontext(regs, &frame->sf_sc);
    err |= __copy_to_user(&frame->sf_mask, set, sizeof(*set));
    if (err)
        goto give_sigsegv;

    /*
     * Arguments to signal handler:
     *
     *   a0 = signal number
     *   a1 = 0 (should be cause)
     *   a2 = pointer to struct sigcontext
     *
     * $25 and c0_epc point to the signal handler, $29 points to the
     * struct sigframe.
     */
    regs->regs[ 4] = signr;
    regs->regs[ 5] = 0;
    regs->regs[ 6] = (unsigned long) &frame->sf_sc;
    regs->regs[29] = (unsigned long) frame;
    regs->regs[31] = (unsigned long) sig_return;
    regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;

    DEBUGP("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%lx\n",
           current->comm, current->pid,
           frame, regs->cp0_epc, regs->regs[31]);
    return 0;

give_sigsegv:
    force_sigsegv(signr, current);
    return -EFAULT;
}
#endif

static int setup_rt_frame(void *sig_return, struct k_sigaction *ka,
              struct pt_regs *regs, int signr, sigset_t *set,
              siginfo_t *info)
{
    struct rt_sigframe __user *frame;
    int err = 0;

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

    /* Create siginfo.  */
    err |= copy_siginfo_to_user(&frame->rs_info, info);

    /* Create the ucontext.  */
    err |= __put_user(0, &frame->rs_uc.uc_flags);
    err |= __put_user(NULL, &frame->rs_uc.uc_link);
    err |= __put_user((void __user *)current->sas_ss_sp,
                      &frame->rs_uc.uc_stack.ss_sp);
    err |= __put_user(sas_ss_flags(regs->regs[29]),
                      &frame->rs_uc.uc_stack.ss_flags);
    err |= __put_user(current->sas_ss_size,
                      &frame->rs_uc.uc_stack.ss_size);
    err |= setup_sigcontext(regs, &frame->rs_uc.uc_mcontext);
    err |= __copy_to_user(&frame->rs_uc.uc_sigmask, set, sizeof(*set));

    if (err)
        goto give_sigsegv;

    /*
     * Arguments to signal handler:
     *
     *   a0 = signal number
     *   a1 = 0 (should be cause)
     *   a2 = pointer to ucontext
     *
     * $25 and c0_epc point to the signal handler, $29 points to
     * the struct rt_sigframe.
     */
    regs->regs[ 4] = signr;
    regs->regs[ 5] = (unsigned long) &frame->rs_info;
    regs->regs[ 6] = (unsigned long) &frame->rs_uc;
    regs->regs[29] = (unsigned long) frame;
    regs->regs[31] = (unsigned long) sig_return;
    regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;

    DEBUGP("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%lx\n",
           current->comm, current->pid,
           frame, regs->cp0_epc, regs->regs[31]);

    return 0;

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

struct mips_abi mips_abi = {
#ifdef CONFIG_TRAD_SIGNALS
    .setup_frame    = setup_frame,
    .signal_return_offset = offsetof(struct mips_vdso, signal_trampoline),
#endif
    .setup_rt_frame = setup_rt_frame,
    .rt_signal_return_offset =
        offsetof(struct mips_vdso, rt_signal_trampoline),
    .restart    = __NR_restart_syscall
};

static void handle_signal(unsigned long sig, siginfo_t *info,
    struct k_sigaction *ka, struct pt_regs *regs)
{
    sigset_t *oldset = sigmask_to_save();
    int ret;
    struct mips_abi *abi = current->thread.abi;
    void *vdso = current->mm->context.vdso;

    if (regs->regs[0]) {
        switch(regs->regs[2]) {
        case ERESTART_RESTARTBLOCK:
        case ERESTARTNOHAND:
            regs->regs[2] = EINTR;
            break;
        case ERESTARTSYS:
            if (!(ka->sa.sa_flags & SA_RESTART)) {
                regs->regs[2] = EINTR;
                break;
            }
        /* fallthrough */
        case ERESTARTNOINTR:
            regs->regs[7] = regs->regs[26];
            regs->regs[2] = regs->regs[0];
            regs->cp0_epc -= 4;
        }

        regs->regs[0] = 0;      /* Don't deal with this again.  */
    }

    if (sig_uses_siginfo(ka))
        ret = abi->setup_rt_frame(vdso + abi->rt_signal_return_offset,
                      ka, regs, sig, oldset, info);
    else
        ret = abi->setup_frame(vdso + abi->signal_return_offset,
                       ka, regs, sig, oldset);

    if (ret)
        return;

    signal_delivered(sig, info, ka, regs, 0);
}

static void do_signal(struct pt_regs *regs)
{
    struct k_sigaction ka;
    siginfo_t info;
    int signr;

    signr = get_signal_to_deliver(&info, &ka, regs, NULL);
    if (signr > 0) {
        /* Whee!  Actually deliver the signal.  */
        handle_signal(signr, &info, &ka, regs);
        return;
    }

    if (regs->regs[0]) {
        if (regs->regs[2] == ERESTARTNOHAND ||
            regs->regs[2] == ERESTARTSYS ||
            regs->regs[2] == ERESTARTNOINTR) {
            regs->regs[2] = regs->regs[0];
            regs->regs[7] = regs->regs[26];
            regs->cp0_epc -= 4;
        }
        if (regs->regs[2] == ERESTART_RESTARTBLOCK) {
            regs->regs[2] = current->thread.abi->restart;
            regs->regs[7] = regs->regs[26];
            regs->cp0_epc -= 4;
        }
        regs->regs[0] = 0;  /* Don't deal with this again.  */
    }

    /*
     * If there's no signal to deliver, we just put the saved sigmask
     * back
     */
    restore_saved_sigmask();
}

/*
 * notification of userspace execution resumption
 * - triggered by the TIF_WORK_MASK flags
 */
asmlinkage void do_notify_resume(struct pt_regs *regs, void *unused,
    __u32 thread_info_flags)
{
    local_irq_enable();

    /* deal with pending signal delivery */
    if (thread_info_flags & _TIF_SIGPENDING)
        do_signal(regs);

    if (thread_info_flags & _TIF_NOTIFY_RESUME) {
        clear_thread_flag(TIF_NOTIFY_RESUME);
        tracehook_notify_resume(regs);
    }
}

#ifdef CONFIG_SMP
static int smp_save_fp_context(struct sigcontext __user *sc)
{
    return raw_cpu_has_fpu
           ? _save_fp_context(sc)
           : fpu_emulator_save_context(sc);
}

static int smp_restore_fp_context(struct sigcontext __user *sc)
{
    return raw_cpu_has_fpu
           ? _restore_fp_context(sc)
           : fpu_emulator_restore_context(sc);
}
#endif

static int signal_setup(void)
{
#ifdef CONFIG_SMP
    /* For now just do the cpu_has_fpu check when the functions are invoked */
    save_fp_context = smp_save_fp_context;
    restore_fp_context = smp_restore_fp_context;
#else
    if (cpu_has_fpu) {
        save_fp_context = _save_fp_context;
        restore_fp_context = _restore_fp_context;
    } else {
        save_fp_context = fpu_emulator_save_context;
        restore_fp_context = fpu_emulator_restore_context;
    }
#endif

    return 0;
}

arch_initcall(signal_setup);