/*
 *  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
 */

#include <linux/sched.h>
#include <linux/mm.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/tracehook.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/personality.h>
#include <linux/uaccess.h>

#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/i387.h>
#include <asm/vdso.h>

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

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

#include <asm/sigframe.h>

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

#define __FIX_EFLAGS    (X86_EFLAGS_AC | X86_EFLAGS_OF | \
                         X86_EFLAGS_DF | X86_EFLAGS_TF | X86_EFLAGS_SF | \
                         X86_EFLAGS_ZF | X86_EFLAGS_AF | X86_EFLAGS_PF | \
                         X86_EFLAGS_CF)

#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)

static 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);
                err |= restore_i387_xstate(buf);

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

        return err;
}

static 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_no, &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 sp = regs->sp;
        int onsigstack = on_sig_stack(sp);

#ifdef CONFIG_X86_64
        /* redzone */
        sp -= 128;
#endif /* CONFIG_X86_64 */

        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 {
#ifdef CONFIG_X86_32
                        /* This is the legacy signal stack switching. */
                        if ((regs->ss & 0xffff) != __USER_DS &&
                                !(ka->sa.sa_flags & SA_RESTORER) &&
                                        ka->sa.sa_restorer)
                                sp = (unsigned long) ka->sa.sa_restorer;
#endif /* CONFIG_X86_32 */
                }
        }

        if (used_math()) {
                sp -= sig_xstate_size;
#ifdef CONFIG_X86_64
                sp = round_down(sp, 64);
#endif /* CONFIG_X86_64 */
                *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 state */
        if (used_math() && save_i387_xstate(*fpstate) < 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);
                err |= copy_siginfo_to_user(&frame->info, info);

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

                /* 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);

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

                /* 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);

        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 */

#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)
{
        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_restore_sigmask();

        return -ERESTARTNOHAND;
}

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 */

#ifdef CONFIG_X86_32
int sys_sigaltstack(struct pt_regs *regs)
{
        const stack_t __user *uss = (const stack_t __user *)regs->bx;
        stack_t __user *uoss = (stack_t __user *)regs->cx;

        return do_sigaltstack(uss, uoss, regs->sp);
}
#else /* !CONFIG_X86_32 */
asmlinkage long
sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
                struct pt_regs *regs)
{
        return do_sigaltstack(uss, uoss, regs->sp);
}
#endif /* CONFIG_X86_32 */

/*
 * 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;

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

        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;

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

        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;
}

#ifdef CONFIG_X86_32

#define is_ia32 1
#define ia32_setup_frame        __setup_frame
#define ia32_setup_rt_frame     __setup_rt_frame

#else /* !CONFIG_X86_32 */

#ifdef CONFIG_IA32_EMULATION
#define is_ia32 test_thread_flag(TIF_IA32)
#else /* !CONFIG_IA32_EMULATION */
#define is_ia32 0
#endif /* CONFIG_IA32_EMULATION */

int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                sigset_t *set, struct pt_regs *regs);
int ia32_setup_frame(int sig, struct k_sigaction *ka,
                sigset_t *set, struct pt_regs *regs);

#endif /* CONFIG_X86_32 */

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

        /* Set up the stack frame */
        if (is_ia32) {
                if (ka->sa.sa_flags & SA_SIGINFO)
                        ret = ia32_setup_rt_frame(usig, ka, info, set, regs);
                else
                        ret = ia32_setup_frame(usig, ka, set, regs);
        } else
                ret = __setup_rt_frame(sig, ka, info, set, regs);

        if (ret) {
                force_sigsegv(sig, current);
                return -EFAULT;
        }

        return ret;
}

static int
handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
              sigset_t *oldset, struct pt_regs *regs)
{
        int ret;

        /* 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;

        ret = setup_rt_frame(sig, ka, info, oldset, regs);

        if (ret)
                return ret;

#ifdef CONFIG_X86_64
        /*
         * This has nothing to do with segment registers,
         * despite the name.  This magic affects uaccess.h
         * macros' behavior.  Reset it to the normal setting.
         */
        set_fs(USER_DS);
#endif

        /*
         * 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;

        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);

        tracehook_signal_handler(sig, info, ka, regs,
                                 test_thread_flag(TIF_SINGLESTEP));

        return 0;
}

#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;
        sigset_t *oldset;

        /*
         * We want the common case to go fast, which is why we may in certain
         * cases get here from kernel mode. Just return without doing anything
         * if so.
         * X86_32: vm86 regs switched out by assembly code before reaching
         * here, so testing against kernel CS suffices.
         */
        if (!user_mode(regs))
                return;

        if (current_thread_info()->status & TS_RESTORE_SIGMASK)
                oldset = &current->saved_sigmask;
        else
                oldset = &current->blocked;

        signr = get_signal_to_deliver(&info, &ka, regs, NULL);
        if (signr > 0) {
                /*
                 * Re-enable any watchpoints before delivering the
                 * signal to user space. The processor register will
                 * have been cleared if the watchpoint triggered
                 * inside the kernel.
                 */
                if (current->thread.debugreg7)
                        set_debugreg(current->thread.debugreg7, 7);

                /* Whee! Actually deliver the signal.  */
                if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
                        /*
                         * A signal was successfully delivered; the saved
                         * sigmask will have been stored in the signal frame,
                         * and will be restored by sigreturn, so we can simply
                         * clear the TS_RESTORE_SIGMASK flag.
                         */
                        current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
                }
                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.
         */
        if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
                current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
                sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
        }
}

/*
 * 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)
{
#if defined(CONFIG_X86_64) && defined(CONFIG_X86_MCE)
        /* notify userspace of pending MCEs */
        if (thread_info_flags & _TIF_MCE_NOTIFY)
                mce_notify_user();
#endif /* CONFIG_X86_64 && CONFIG_X86_MCE */

        /* 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_X86_32
        clear_thread_flag(TIF_IRET);
#endif /* CONFIG_X86_32 */
}

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);
                printk(KERN_CONT "\n");
        }

        force_sig(SIGSEGV, me);
}