// SPDX-License-Identifier: GPL-2.0
/*
 *  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/sched/task_stack.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 <linux/context_tracking.h>
#include <linux/syscalls.h>

#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/fpu/internal.h>
#include <asm/fpu/signal.h>
#include <asm/vdso.h>
#include <asm/mce.h>
#include <asm/sighandling.h>
#include <asm/vm86.h>

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

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

#include <asm/sigframe.h>
#include <asm/signal.h>

#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)

#ifdef CONFIG_X86_64
/*
 * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
 * alone.  Using this generally makes no sense unless
 * user_64bit_mode(regs) would return true.
 */
static void force_valid_ss(struct pt_regs *regs)
{
        u32 ar;
        asm volatile ("lar %[old_ss], %[ar]\n\t"
                      "jz 1f\n\t"               /* If invalid: */
                      "xorl %[ar], %[ar]\n\t"   /* set ar = 0 */
                      "1:"
                      : [ar] "=r" (ar)
                      : [old_ss] "rm" ((u16)regs->ss));

        /*
         * For a valid 64-bit user context, we need DPL 3, type
         * read-write data or read-write exp-down data, and S and P
         * set.  We can't use VERW because VERW doesn't check the
         * P bit.
         */
        ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
        if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
            ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
                regs->ss = __USER_DS;
}
#endif

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

        /* Always make any pending restarted system calls return -EINTR */
        current->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); COPY(ax);

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

                COPY_SEG_CPL3(cs);
                COPY_SEG_CPL3(ss);

                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_val, &sc->fpstate);
                buf = (void __user *)buf_val;
        } get_user_catch(err);

#ifdef CONFIG_X86_64
        /*
         * Fix up SS if needed for the benefit of old DOSEMU and
         * CRIU.
         */
        if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
                force_valid_ss(regs);
#endif

        err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32));

        force_iret();

        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);
                put_user_ex(regs->ss, &sc->ss);
#endif /* CONFIG_X86_32 */

                put_user_ex(fpstate, (unsigned long __user *)&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 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);
        int ret;

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

        /* This is the X/Open sanctioned signal stack switching.  */
        if (ka->sa.sa_flags & SA_ONSTACK) {
                if (sas_ss_flags(sp) == 0)
                        sp = current->sas_ss_sp + current->sas_ss_size;
        } else if (IS_ENABLED(CONFIG_X86_32) &&
                   !onsigstack &&
                   regs->ss != __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;
        }

        sp = fpu__alloc_mathframe(sp, IS_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 */
        ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
        if (ret < 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 ksignal *ksig, sigset_t *set,
              struct pt_regs *regs)
{
        struct sigframe __user *frame;
        void __user *restorer;
        int err = 0;
        void __user *fpstate = NULL;

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

        if (!access_ok(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 = current->mm->context.vdso +
                        vdso_image_32.sym___kernel_sigreturn;
        else
                restorer = &frame->retcode;
        if (ksig->ka.sa.sa_flags & SA_RESTORER)
                restorer = ksig->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)ksig->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 ksignal *ksig,
                            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(&ksig->ka, regs, sizeof(*frame), &fpstate);

        if (!access_ok(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 (static_cpu_has(X86_FEATURE_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);
                save_altstack_ex(&frame->uc.uc_stack, regs->sp);

                /* Set up to return from userspace.  */
                restorer = current->mm->context.vdso +
                        vdso_image_32.sym___kernel_rt_sigreturn;
                if (ksig->ka.sa.sa_flags & SA_RESTORER)
                        restorer = ksig->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, &ksig->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)ksig->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 unsigned long frame_uc_flags(struct pt_regs *regs)
{
        unsigned long flags;

        if (boot_cpu_has(X86_FEATURE_XSAVE))
                flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
        else
                flags = UC_SIGCONTEXT_SS;

        if (likely(user_64bit_mode(regs)))
                flags |= UC_STRICT_RESTORE_SS;

        return flags;
}

static int __setup_rt_frame(int sig, struct ksignal *ksig,
                            sigset_t *set, struct pt_regs *regs)
{
        struct rt_sigframe __user *frame;
        void __user *fp = NULL;
        unsigned long uc_flags;
        int err = 0;

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

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

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

        uc_flags = frame_uc_flags(regs);

        put_user_try {
                /* Create the ucontext.  */
                put_user_ex(uc_flags, &frame->uc.uc_flags);
                put_user_ex(0, &frame->uc.uc_link);
                save_altstack_ex(&frame->uc.uc_stack, regs->sp);

                /* Set up to return from userspace.  If provided, use a stub
                   already in userspace.  */
                /* x86-64 should always use SA_RESTORER. */
                if (ksig->ka.sa.sa_flags & SA_RESTORER) {
                        put_user_ex(ksig->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) ksig->ka.sa.sa_handler;

        regs->sp = (unsigned long)frame;

        /*
         * Set up the CS and SS registers to run signal handlers in
         * 64-bit mode, even if the handler happens to be interrupting
         * 32-bit or 16-bit code.
         *
         * SS is subtle.  In 64-bit mode, we don't need any particular
         * SS descriptor, but we do need SS to be valid.  It's possible
         * that the old SS is entirely bogus -- this can happen if the
         * signal we're trying to deliver is #GP or #SS caused by a bad
         * SS value.  We also have a compatbility issue here: DOSEMU
         * relies on the contents of the SS register indicating the
         * SS value at the time of the signal, even though that code in
         * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
         * avoids relying on sigreturn to restore SS; instead it uses
         * a trampoline.)  So we do our best: if the old SS was valid,
         * we keep it.  Otherwise we replace it.
         */
        regs->cs = __USER_CS;

        if (unlikely(regs->ss != __USER_DS))
                force_valid_ss(regs);

        return 0;
}
#endif /* CONFIG_X86_32 */

static int x32_setup_rt_frame(struct ksignal *ksig,
                              compat_sigset_t *set,
                              struct pt_regs *regs)
{
#ifdef CONFIG_X86_X32_ABI
        struct rt_sigframe_x32 __user *frame;
        unsigned long uc_flags;
        void __user *restorer;
        int err = 0;
        void __user *fpstate = NULL;

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

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

        if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
                if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
                        return -EFAULT;
        }

        uc_flags = frame_uc_flags(regs);

        put_user_try {
                /* Create the ucontext.  */
                put_user_ex(uc_flags, &frame->uc.uc_flags);
                put_user_ex(0, &frame->uc.uc_link);
                compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
                put_user_ex(0, &frame->uc.uc__pad0);

                if (ksig->ka.sa.sa_flags & SA_RESTORER) {
                        restorer = ksig->ka.sa.sa_restorer;
                } else {
                        /* could use a vstub here */
                        restorer = NULL;
                        err |= -EFAULT;
                }
                put_user_ex(restorer, (unsigned long __user *)&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) ksig->ka.sa.sa_handler;

        /* We use the x32 calling convention here... */
        regs->di = ksig->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;
}

/*
 * Do a signal return; undo the signal stack.
 */
#ifdef CONFIG_X86_32
SYSCALL_DEFINE0(sigreturn)
{
        struct pt_regs *regs = current_pt_regs();
        struct sigframe __user *frame;
        sigset_t set;

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

        if (!access_ok(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);

        /*
         * x86_32 has no uc_flags bits relevant to restore_sigcontext.
         * Save a few cycles by skipping the __get_user.
         */
        if (restore_sigcontext(regs, &frame->sc, 0))
                goto badframe;
        return regs->ax;

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

        return 0;
}
#endif /* CONFIG_X86_32 */

SYSCALL_DEFINE0(rt_sigreturn)
{
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe __user *frame;
        sigset_t set;
        unsigned long uc_flags;

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

        set_current_blocked(&set);

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

        if (restore_altstack(&frame->uc.uc_stack))
                goto badframe;

        return regs->ax;

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

static inline int is_ia32_compat_frame(struct ksignal *ksig)
{
        return IS_ENABLED(CONFIG_IA32_EMULATION) &&
                ksig->ka.sa.sa_flags & SA_IA32_ABI;
}

static inline int is_ia32_frame(struct ksignal *ksig)
{
        return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
}

static inline int is_x32_frame(struct ksignal *ksig)
{
        return IS_ENABLED(CONFIG_X86_X32_ABI) &&
                ksig->ka.sa.sa_flags & SA_X32_ABI;
}

static int
setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
{
        int usig = ksig->sig;
        sigset_t *set = sigmask_to_save();
        compat_sigset_t *cset = (compat_sigset_t *) set;

        /* Perform fixup for the pre-signal frame. */
        rseq_signal_deliver(ksig, regs);

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

static void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
        bool stepping, failed;
        struct fpu *fpu = &current->thread.fpu;

        if (v8086_mode(regs))
                save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);

        /* 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 (!(ksig->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 TF now
         * so that register information in the sigcontext is correct and
         * then notify the tracer before entering the signal handler.
         */
        stepping = test_thread_flag(TIF_SINGLESTEP);
        if (stepping)
                user_disable_single_step(current);

        failed = (setup_rt_frame(ksig, regs) < 0);
        if (!failed) {
                /*
                 * Clear the direction flag as per the ABI for function entry.
                 *
                 * Clear RF when entering the signal handler, because
                 * it might disable possible debug exception from the
                 * signal handler.
                 *
                 * Clear TF for the case when it wasn't set by debugger to
                 * avoid the recursive send_sigtrap() in SIGTRAP handler.
                 */
                regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
                /*
                 * Ensure the signal handler starts with the new fpu state.
                 */
                fpu__clear(fpu);
        }
        signal_setup_done(failed, ksig, stepping);
}

static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
{
        /*
         * This function is fundamentally broken as currently
         * implemented.
         *
         * The idea is that we want to trigger a call to the
         * restart_block() syscall and that we want in_ia32_syscall(),
         * in_x32_syscall(), etc. to match whatever they were in the
         * syscall being restarted.  We assume that the syscall
         * instruction at (regs->ip - 2) matches whatever syscall
         * instruction we used to enter in the first place.
         *
         * The problem is that we can get here when ptrace pokes
         * syscall-like values into regs even if we're not in a syscall
         * at all.
         *
         * For now, we maintain historical behavior and guess based on
         * stored state.  We could do better by saving the actual
         * syscall arch in restart_block or (with caveats on x32) by
         * checking if regs->ip points to 'int $0x80'.  The current
         * behavior is incorrect if a tracer has a different bitness
         * than the tracee.
         */
#ifdef CONFIG_IA32_EMULATION
        if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
                return __NR_ia32_restart_syscall;
#endif
#ifdef CONFIG_X86_X32_ABI
        return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
#else
        return __NR_restart_syscall;
#endif
}

/*
 * 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.
 */
void do_signal(struct pt_regs *regs)
{
        struct ksignal ksig;

        if (get_signal(&ksig)) {
                /* Whee! Actually deliver the signal.  */
                handle_signal(&ksig, 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 = get_nr_restart_syscall(regs);
                        regs->ip -= 2;
                        break;
                }
        }

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

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(KERN_CONT " in ", regs->ip);
                pr_cont("\n");
        }

        force_sig(SIGSEGV);
}

#ifdef CONFIG_X86_X32_ABI
asmlinkage long sys32_x32_rt_sigreturn(void)
{
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe_x32 __user *frame;
        sigset_t set;
        unsigned long uc_flags;

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

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

        set_current_blocked(&set);

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

        if (compat_restore_altstack(&frame->uc.uc_stack))
                goto badframe;

        return regs->ax;

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