signal.c

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/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
 *
 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
 *  2000-2002   x86-64 support by Andi Kleen
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/tracehook.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/personality.h>
#include <linux/uaccess.h>
#include <linux/user-return-notifier.h>
#include <linux/uprobes.h>

#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/i387.h>
#include <asm/fpu-internal.h>
#include <asm/vdso.h>
#include <asm/mce.h>
#include <asm/sighandling.h>

#ifdef CONFIG_X86_64
#include <asm/proto.h>
#include <asm/ia32_unistd.h>
#include <asm/sys_ia32.h>
#endif /* CONFIG_X86_64 */

#include <asm/syscall.h>
#include <asm/syscalls.h>

#include <asm/sigframe.h>

#ifdef CONFIG_X86_32
# define FIX_EFLAGS (__FIX_EFLAGS | X86_EFLAGS_RF)
#else
# define FIX_EFLAGS __FIX_EFLAGS
#endif

#define COPY(x)         do {            \
    get_user_ex(regs->x, &sc->x);           \
} while (0)

#define GET_SEG(seg)        ({          \
    unsigned short tmp;             \
    get_user_ex(tmp, &sc->seg);         \
    tmp;                        \
})

#define COPY_SEG(seg)       do {            \
    regs->seg = GET_SEG(seg);           \
} while (0)

#define COPY_SEG_CPL3(seg)  do {            \
    regs->seg = GET_SEG(seg) | 3;           \
} while (0)

int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
               unsigned long *pax)
{
    void __user *buf;
    unsigned int tmpflags;
    unsigned int err = 0;

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

    get_user_try {

#ifdef CONFIG_X86_32
        set_user_gs(regs, GET_SEG(gs));
        COPY_SEG(fs);
        COPY_SEG(es);
        COPY_SEG(ds);
#endif /* CONFIG_X86_32 */

        COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
        COPY(dx); COPY(cx); COPY(ip);

#ifdef CONFIG_X86_64
        COPY(r8);
        COPY(r9);
        COPY(r10);
        COPY(r11);
        COPY(r12);
        COPY(r13);
        COPY(r14);
        COPY(r15);
#endif /* CONFIG_X86_64 */

#ifdef CONFIG_X86_32
        COPY_SEG_CPL3(cs);
        COPY_SEG_CPL3(ss);
#else /* !CONFIG_X86_32 */
        /* Kernel saves and restores only the CS segment register on signals,
         * which is the bare minimum needed to allow mixed 32/64-bit code.
         * App's signal handler can save/restore other segments if needed. */
        COPY_SEG_CPL3(cs);
#endif /* CONFIG_X86_32 */

        get_user_ex(tmpflags, &sc->flags);
        regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
        regs->orig_ax = -1;     /* disable syscall checks */

        get_user_ex(buf, &sc->fpstate);

        get_user_ex(*pax, &sc->ax);
    } get_user_catch(err);

    err |= restore_xstate_sig(buf, config_enabled(CONFIG_X86_32));

    return err;
}

int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
             struct pt_regs *regs, unsigned long mask)
{
    int err = 0;

    put_user_try {

#ifdef CONFIG_X86_32
        put_user_ex(get_user_gs(regs), (unsigned int __user *)&sc->gs);
        put_user_ex(regs->fs, (unsigned int __user *)&sc->fs);
        put_user_ex(regs->es, (unsigned int __user *)&sc->es);
        put_user_ex(regs->ds, (unsigned int __user *)&sc->ds);
#endif /* CONFIG_X86_32 */

        put_user_ex(regs->di, &sc->di);
        put_user_ex(regs->si, &sc->si);
        put_user_ex(regs->bp, &sc->bp);
        put_user_ex(regs->sp, &sc->sp);
        put_user_ex(regs->bx, &sc->bx);
        put_user_ex(regs->dx, &sc->dx);
        put_user_ex(regs->cx, &sc->cx);
        put_user_ex(regs->ax, &sc->ax);
#ifdef CONFIG_X86_64
        put_user_ex(regs->r8, &sc->r8);
        put_user_ex(regs->r9, &sc->r9);
        put_user_ex(regs->r10, &sc->r10);
        put_user_ex(regs->r11, &sc->r11);
        put_user_ex(regs->r12, &sc->r12);
        put_user_ex(regs->r13, &sc->r13);
        put_user_ex(regs->r14, &sc->r14);
        put_user_ex(regs->r15, &sc->r15);
#endif /* CONFIG_X86_64 */

        put_user_ex(current->thread.trap_nr, &sc->trapno);
        put_user_ex(current->thread.error_code, &sc->err);
        put_user_ex(regs->ip, &sc->ip);
#ifdef CONFIG_X86_32
        put_user_ex(regs->cs, (unsigned int __user *)&sc->cs);
        put_user_ex(regs->flags, &sc->flags);
        put_user_ex(regs->sp, &sc->sp_at_signal);
        put_user_ex(regs->ss, (unsigned int __user *)&sc->ss);
#else /* !CONFIG_X86_32 */
        put_user_ex(regs->flags, &sc->flags);
        put_user_ex(regs->cs, &sc->cs);
        put_user_ex(0, &sc->gs);
        put_user_ex(0, &sc->fs);
#endif /* CONFIG_X86_32 */

        put_user_ex(fpstate, &sc->fpstate);

        /* non-iBCS2 extensions.. */
        put_user_ex(mask, &sc->oldmask);
        put_user_ex(current->thread.cr2, &sc->cr2);
    } put_user_catch(err);

    return err;
}

/*
 * Set up a signal frame.
 */

/*
 * Determine which stack to use..
 */
static unsigned long align_sigframe(unsigned long sp)
{
#ifdef CONFIG_X86_32
    /*
     * Align the stack pointer according to the i386 ABI,
     * i.e. so that on function entry ((sp + 4) & 15) == 0.
     */
    sp = ((sp + 4) & -16ul) - 4;
#else /* !CONFIG_X86_32 */
    sp = round_down(sp, 16) - 8;
#endif
    return sp;
}

static inline void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
         void __user **fpstate)
{
    /* Default to using normal stack */
    unsigned long math_size = 0;
    unsigned long sp = regs->sp;
    unsigned long buf_fx = 0;
    int onsigstack = on_sig_stack(sp);

    /* redzone */
    if (config_enabled(CONFIG_X86_64))
        sp -= 128;

    if (!onsigstack) {
        /* This is the X/Open sanctioned signal stack switching.  */
        if (ka->sa.sa_flags & SA_ONSTACK) {
            if (current->sas_ss_size)
                sp = current->sas_ss_sp + current->sas_ss_size;
        } else if (config_enabled(CONFIG_X86_32) &&
               (regs->ss & 0xffff) != __USER_DS &&
               !(ka->sa.sa_flags & SA_RESTORER) &&
               ka->sa.sa_restorer) {
                /* This is the legacy signal stack switching. */
                sp = (unsigned long) ka->sa.sa_restorer;
        }
    }

    if (used_math()) {
        sp = alloc_mathframe(sp, config_enabled(CONFIG_X86_32),
                     &buf_fx, &math_size);
        *fpstate = (void __user *)sp;
    }

    sp = align_sigframe(sp - frame_size);

    /*
     * If we are on the alternate signal stack and would overflow it, don't.
     * Return an always-bogus address instead so we will die with SIGSEGV.
     */
    if (onsigstack && !likely(on_sig_stack(sp)))
        return (void __user *)-1L;

    /* save i387 and extended state */
    if (used_math() &&
        save_xstate_sig(*fpstate, (void __user *)buf_fx, math_size) < 0)
        return (void __user *)-1L;

    return (void __user *)sp;
}

#ifdef CONFIG_X86_32
static const struct {
    u16 poplmovl;
    u32 val;
    u16 int80;
} __attribute__((packed)) retcode = {
    0xb858,     /* popl %eax; movl $..., %eax */
    __NR_sigreturn,
    0x80cd,     /* int $0x80 */
};

static const struct {
    u8  movl;
    u32 val;
    u16 int80;
    u8  pad;
} __attribute__((packed)) rt_retcode = {
    0xb8,       /* movl $..., %eax */
    __NR_rt_sigreturn,
    0x80cd,     /* int $0x80 */
    0
};

static int
__setup_frame(int sig, struct k_sigaction *ka, sigset_t *set,
          struct pt_regs *regs)
{
    struct sigframe __user *frame;
    void __user *restorer;
    int err = 0;
    void __user *fpstate = NULL;

    frame = get_sigframe(ka, regs, sizeof(*frame), &fpstate);

    if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
        return -EFAULT;

    if (__put_user(sig, &frame->sig))
        return -EFAULT;

    if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
        return -EFAULT;

    if (_NSIG_WORDS > 1) {
        if (__copy_to_user(&frame->extramask, &set->sig[1],
                   sizeof(frame->extramask)))
            return -EFAULT;
    }

    if (current->mm->context.vdso)
        restorer = VDSO32_SYMBOL(current->mm->context.vdso, sigreturn);
    else
        restorer = &frame->retcode;
    if (ka->sa.sa_flags & SA_RESTORER)
        restorer = ka->sa.sa_restorer;

    /* Set up to return from userspace.  */
    err |= __put_user(restorer, &frame->pretcode);

    /*
     * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
     *
     * WE DO NOT USE IT ANY MORE! It's only left here for historical
     * reasons and because gdb uses it as a signature to notice
     * signal handler stack frames.
     */
    err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);

    if (err)
        return -EFAULT;

    /* Set up registers for signal handler */
    regs->sp = (unsigned long)frame;
    regs->ip = (unsigned long)ka->sa.sa_handler;
    regs->ax = (unsigned long)sig;
    regs->dx = 0;
    regs->cx = 0;

    regs->ds = __USER_DS;
    regs->es = __USER_DS;
    regs->ss = __USER_DS;
    regs->cs = __USER_CS;

    return 0;
}

static int __setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                sigset_t *set, struct pt_regs *regs)
{
    struct rt_sigframe __user *frame;
    void __user *restorer;
    int err = 0;
    void __user *fpstate = NULL;

    frame = get_sigframe(ka, regs, sizeof(*frame), &fpstate);

    if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
        return -EFAULT;

    put_user_try {
        put_user_ex(sig, &frame->sig);
        put_user_ex(&frame->info, &frame->pinfo);
        put_user_ex(&frame->uc, &frame->puc);

        /* Create the ucontext.  */
        if (cpu_has_xsave)
            put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
        else
            put_user_ex(0, &frame->uc.uc_flags);
        put_user_ex(0, &frame->uc.uc_link);
        put_user_ex(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
        put_user_ex(sas_ss_flags(regs->sp),
                &frame->uc.uc_stack.ss_flags);
        put_user_ex(current->sas_ss_size, &frame->uc.uc_stack.ss_size);

        /* Set up to return from userspace.  */
        restorer = VDSO32_SYMBOL(current->mm->context.vdso, rt_sigreturn);
        if (ka->sa.sa_flags & SA_RESTORER)
            restorer = ka->sa.sa_restorer;
        put_user_ex(restorer, &frame->pretcode);

        /*
         * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
         *
         * WE DO NOT USE IT ANY MORE! It's only left here for historical
         * reasons and because gdb uses it as a signature to notice
         * signal handler stack frames.
         */
        put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
    } put_user_catch(err);
    
    err |= copy_siginfo_to_user(&frame->info, info);
    err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
                regs, set->sig[0]);
    err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

    if (err)
        return -EFAULT;

    /* Set up registers for signal handler */
    regs->sp = (unsigned long)frame;
    regs->ip = (unsigned long)ka->sa.sa_handler;
    regs->ax = (unsigned long)sig;
    regs->dx = (unsigned long)&frame->info;
    regs->cx = (unsigned long)&frame->uc;

    regs->ds = __USER_DS;
    regs->es = __USER_DS;
    regs->ss = __USER_DS;
    regs->cs = __USER_CS;

    return 0;
}
#else /* !CONFIG_X86_32 */
static int __setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                sigset_t *set, struct pt_regs *regs)
{
    struct rt_sigframe __user *frame;
    void __user *fp = NULL;
    int err = 0;
    struct task_struct *me = current;

    frame = get_sigframe(ka, regs, sizeof(struct rt_sigframe), &fp);

    if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
        return -EFAULT;

    if (ka->sa.sa_flags & SA_SIGINFO) {
        if (copy_siginfo_to_user(&frame->info, info))
            return -EFAULT;
    }

    put_user_try {
        /* Create the ucontext.  */
        if (cpu_has_xsave)
            put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
        else
            put_user_ex(0, &frame->uc.uc_flags);
        put_user_ex(0, &frame->uc.uc_link);
        put_user_ex(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
        put_user_ex(sas_ss_flags(regs->sp),
                &frame->uc.uc_stack.ss_flags);
        put_user_ex(me->sas_ss_size, &frame->uc.uc_stack.ss_size);

        /* Set up to return from userspace.  If provided, use a stub
           already in userspace.  */
        /* x86-64 should always use SA_RESTORER. */
        if (ka->sa.sa_flags & SA_RESTORER) {
            put_user_ex(ka->sa.sa_restorer, &frame->pretcode);
        } else {
            /* could use a vstub here */
            err |= -EFAULT;
        }
    } put_user_catch(err);

    err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]);
    err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

    if (err)
        return -EFAULT;

    /* Set up registers for signal handler */
    regs->di = sig;
    /* In case the signal handler was declared without prototypes */
    regs->ax = 0;

    /* This also works for non SA_SIGINFO handlers because they expect the
       next argument after the signal number on the stack. */
    regs->si = (unsigned long)&frame->info;
    regs->dx = (unsigned long)&frame->uc;
    regs->ip = (unsigned long) ka->sa.sa_handler;

    regs->sp = (unsigned long)frame;

    /* Set up the CS register to run signal handlers in 64-bit mode,
       even if the handler happens to be interrupting 32-bit code. */
    regs->cs = __USER_CS;

    return 0;
}
#endif /* CONFIG_X86_32 */

static int x32_setup_rt_frame(int sig, struct k_sigaction *ka,
                  siginfo_t *info, compat_sigset_t *set,
                  struct pt_regs *regs)
{
#ifdef CONFIG_X86_X32_ABI
    struct rt_sigframe_x32 __user *frame;
    void __user *restorer;
    int err = 0;
    void __user *fpstate = NULL;

    frame = get_sigframe(ka, regs, sizeof(*frame), &fpstate);

    if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
        return -EFAULT;

    if (ka->sa.sa_flags & SA_SIGINFO) {
        if (copy_siginfo_to_user32(&frame->info, info))
            return -EFAULT;
    }

    put_user_try {
        /* Create the ucontext.  */
        if (cpu_has_xsave)
            put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
        else
            put_user_ex(0, &frame->uc.uc_flags);
        put_user_ex(0, &frame->uc.uc_link);
        put_user_ex(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
        put_user_ex(sas_ss_flags(regs->sp),
                &frame->uc.uc_stack.ss_flags);
        put_user_ex(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
        put_user_ex(0, &frame->uc.uc__pad0);

        if (ka->sa.sa_flags & SA_RESTORER) {
            restorer = ka->sa.sa_restorer;
        } else {
            /* could use a vstub here */
            restorer = NULL;
            err |= -EFAULT;
        }
        put_user_ex(restorer, &frame->pretcode);
    } put_user_catch(err);

    err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
                regs, set->sig[0]);
    err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

    if (err)
        return -EFAULT;

    /* Set up registers for signal handler */
    regs->sp = (unsigned long) frame;
    regs->ip = (unsigned long) ka->sa.sa_handler;

    /* We use the x32 calling convention here... */
    regs->di = sig;
    regs->si = (unsigned long) &frame->info;
    regs->dx = (unsigned long) &frame->uc;

    loadsegment(ds, __USER_DS);
    loadsegment(es, __USER_DS);

    regs->cs = __USER_CS;
    regs->ss = __USER_DS;
#endif  /* CONFIG_X86_X32_ABI */

    return 0;
}

#ifdef CONFIG_X86_32
/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
asmlinkage int
sys_sigsuspend(int history0, int history1, old_sigset_t mask)
{
    sigset_t blocked;
    siginitset(&blocked, mask);
    return sigsuspend(&blocked);
}

asmlinkage int
sys_sigaction(int sig, const struct old_sigaction __user *act,
          struct old_sigaction __user *oact)
{
    struct k_sigaction new_ka, old_ka;
    int ret = 0;

    if (act) {
        old_sigset_t mask;

        if (!access_ok(VERIFY_READ, act, sizeof(*act)))
            return -EFAULT;

        get_user_try {
            get_user_ex(new_ka.sa.sa_handler, &act->sa_handler);
            get_user_ex(new_ka.sa.sa_flags, &act->sa_flags);
            get_user_ex(mask, &act->sa_mask);
            get_user_ex(new_ka.sa.sa_restorer, &act->sa_restorer);
        } get_user_catch(ret);

        if (ret)
            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;

        put_user_try {
            put_user_ex(old_ka.sa.sa_handler, &oact->sa_handler);
            put_user_ex(old_ka.sa.sa_flags, &oact->sa_flags);
            put_user_ex(old_ka.sa.sa_mask.sig[0], &oact->sa_mask);
            put_user_ex(old_ka.sa.sa_restorer, &oact->sa_restorer);
        } put_user_catch(ret);

        if (ret)
            return -EFAULT;
    }

    return ret;
}
#endif /* CONFIG_X86_32 */

long
sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
        struct pt_regs *regs)
{
    return do_sigaltstack(uss, uoss, regs->sp);
}

/*
 * Do a signal return; undo the signal stack.
 */
#ifdef CONFIG_X86_32
unsigned long sys_sigreturn(struct pt_regs *regs)
{
    struct sigframe __user *frame;
    unsigned long ax;
    sigset_t set;

    frame = (struct sigframe __user *)(regs->sp - 8);

    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
        goto badframe;
    if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
        && __copy_from_user(&set.sig[1], &frame->extramask,
                    sizeof(frame->extramask))))
        goto badframe;

    set_current_blocked(&set);

    if (restore_sigcontext(regs, &frame->sc, &ax))
        goto badframe;
    return ax;

badframe:
    signal_fault(regs, frame, "sigreturn");

    return 0;
}
#endif /* CONFIG_X86_32 */

long sys_rt_sigreturn(struct pt_regs *regs)
{
    struct rt_sigframe __user *frame;
    unsigned long ax;
    sigset_t set;

    frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
        goto badframe;
    if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
        goto badframe;

    set_current_blocked(&set);

    if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
        goto badframe;

    if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
        goto badframe;

    return ax;

badframe:
    signal_fault(regs, frame, "rt_sigreturn");
    return 0;
}

/*
 * OK, we're invoking a handler:
 */
static int signr_convert(int sig)
{
#ifdef CONFIG_X86_32
    struct thread_info *info = current_thread_info();

    if (info->exec_domain && info->exec_domain->signal_invmap && sig < 32)
        return info->exec_domain->signal_invmap[sig];
#endif /* CONFIG_X86_32 */
    return sig;
}

static int
setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
        struct pt_regs *regs)
{
    int usig = signr_convert(sig);
    sigset_t *set = sigmask_to_save();
    compat_sigset_t *cset = (compat_sigset_t *) set;

    /* Set up the stack frame */
    if (is_ia32_frame()) {
        if (ka->sa.sa_flags & SA_SIGINFO)
            return ia32_setup_rt_frame(usig, ka, info, cset, regs);
        else
            return ia32_setup_frame(usig, ka, cset, regs);
    } else if (is_x32_frame()) {
        return x32_setup_rt_frame(usig, ka, info, cset, regs);
    } else {
        return __setup_rt_frame(sig, ka, info, set, regs);
    }
}

static void
handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
        struct pt_regs *regs)
{
    /* Are we from a system call? */
    if (syscall_get_nr(current, regs) >= 0) {
        /* If so, check system call restarting.. */
        switch (syscall_get_error(current, regs)) {
        case -ERESTART_RESTARTBLOCK:
        case -ERESTARTNOHAND:
            regs->ax = -EINTR;
            break;

        case -ERESTARTSYS:
            if (!(ka->sa.sa_flags & SA_RESTART)) {
                regs->ax = -EINTR;
                break;
            }
        /* fallthrough */
        case -ERESTARTNOINTR:
            regs->ax = regs->orig_ax;
            regs->ip -= 2;
            break;
        }
    }

    /*
     * If TF is set due to a debugger (TIF_FORCED_TF), clear the TF
     * flag so that register information in the sigcontext is correct.
     */
    if (unlikely(regs->flags & X86_EFLAGS_TF) &&
        likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
        regs->flags &= ~X86_EFLAGS_TF;

    if (setup_rt_frame(sig, ka, info, regs) < 0) {
        force_sigsegv(sig, current);
        return;
    }

    /*
     * Clear the direction flag as per the ABI for function entry.
     */
    regs->flags &= ~X86_EFLAGS_DF;

    /*
     * Clear TF when entering the signal handler, but
     * notify any tracer that was single-stepping it.
     * The tracer may want to single-step inside the
     * handler too.
     */
    regs->flags &= ~X86_EFLAGS_TF;

    signal_delivered(sig, info, ka, regs,
             test_thread_flag(TIF_SINGLESTEP));
}

#ifdef CONFIG_X86_32
#define NR_restart_syscall  __NR_restart_syscall
#else /* !CONFIG_X86_32 */
#define NR_restart_syscall  \
    test_thread_flag(TIF_IA32) ? __NR_ia32_restart_syscall : __NR_restart_syscall
#endif /* CONFIG_X86_32 */

/*
 * 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)
{
    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;
    }

    /* Did we come from a system call? */
    if (syscall_get_nr(current, regs) >= 0) {
        /* Restart the system call - no handlers present */
        switch (syscall_get_error(current, regs)) {
        case -ERESTARTNOHAND:
        case -ERESTARTSYS:
        case -ERESTARTNOINTR:
            regs->ax = regs->orig_ax;
            regs->ip -= 2;
            break;

        case -ERESTART_RESTARTBLOCK:
            regs->ax = NR_restart_syscall;
            regs->ip -= 2;
            break;
        }
    }

    /*
     * 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
 */
void
do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
{
    rcu_user_exit();

#ifdef CONFIG_X86_MCE
    /* notify userspace of pending MCEs */
    if (thread_info_flags & _TIF_MCE_NOTIFY)
        mce_notify_process();
#endif /* CONFIG_X86_64 && CONFIG_X86_MCE */

    if (thread_info_flags & _TIF_UPROBE)
        uprobe_notify_resume(regs);

    /* 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);
    }
    if (thread_info_flags & _TIF_USER_RETURN_NOTIFY)
        fire_user_return_notifiers();

    rcu_user_enter();
}

void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
{
    struct task_struct *me = current;

    if (show_unhandled_signals && printk_ratelimit()) {
        printk("%s"
               "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
               task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
               me->comm, me->pid, where, frame,
               regs->ip, regs->sp, regs->orig_ax);
        print_vma_addr(" in ", regs->ip);
        pr_cont("\n");
    }

    force_sig(SIGSEGV, me);
}

#ifdef CONFIG_X86_X32_ABI
asmlinkage long sys32_x32_rt_sigreturn(struct pt_regs *regs)
{
    struct rt_sigframe_x32 __user *frame;
    sigset_t set;
    unsigned long ax;
    struct pt_regs tregs;

    frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);

    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
        goto badframe;
    if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
        goto badframe;

    set_current_blocked(&set);

    if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
        goto badframe;

    tregs = *regs;
    if (sys32_sigaltstack(&frame->uc.uc_stack, NULL, &tregs) == -EFAULT)
        goto badframe;

    return ax;

badframe:
    signal_fault(regs, frame, "x32 rt_sigreturn");
    return 0;
}
#endif